Dissertations / Theses on the topic 'Azeotropic distillation'

In ths work, new multicomponent feasibility, column design and column sequencing tools are proposed. These tools are particularly useful in the synthesis of distillation columns and column sequences that separate azeotropic mixtures, where they provide accurate design parameters as well as good estimates of product compositions for use in commercial simulators. Recent work on ternary mixtures has led to the development of a new criterion for establishing staged column feasibility. This new criterion provides a necessary and sufficient condition for staged-column feasibility, and a column design method is developed based on this criterion for the design of simple and complex columns. The column design method can be extended to describe non-ideal column operation as well as packed columns. The column design method is particularly useful in the design of columns that separate azeotropic mixtures as it provides accurate column specifications where conventional shortcut methods fail. A retrofit method for increasing throughput is also developed using the new feasibility criterion. A new feasibility test for product compositions from columns separating multicomponent mixtures is introduced. Unlike present methods, the new feasibility test requires only the specification of the principal mole fractions in both products. Visualisation is not required as feasibility is established numerically. The feasibility test is therefore applicable to mixtures with any number of components. The feasibility test is extended to identify feasible and potentially feasible classes of splits, which are defined by product regions instead of product compositions. Various classes of splits are then grouped according to type. A column design method for columns separating multicomponent azeotropic mixtures is developed. Based on a new criterion developed for application in ternary mixtures, the new column design method requires the specification of the principal mole fractions in both products. The design method is developed for two cases - columns that produce pure components and columns that perform general splits. In both cases a matrix of feasible operating parameters can be constructed, which can be used to identify favorouble operating parameters. The feasibility and column design methods are used to develop an algorithmic column sequence synthesis procedure for multi component azeotropic mixtures. Given a feed composition and product requirements, the synthesis procedure makes use of the feasibility test for classes of splits to generate a number of potentially feasible column sequences, each of which has an associated recycle superstructure. Feasible column sequences are then identified and the multi component column design methods are employed for every column in the sequence.

A large number of distillation sequences can be generated to separate a multicomponent azeotropic mixture. However, there is no systematic and efficient method for synthesising promising sequences, which also consider recycle connections and flowrates. In this work, a systematic procedure is developed for synthesising economically promising distillation sequences separating multicomponent homogeneous azeotropic mixtures. The procedure uses spherically approximated distillation boundaries, a shortcut column design method, and allows recycle and sequence alternatives to be screened. Both feasibility and design are addressed. Approximation of a distillation boundary as a spherical surface is a simple nonlinear, yet more accurate representation of the actual boundary than a linear approximation. For shortcut column design, azeotropes are treated as pseudocomponents and the relative volatilities of all singular points of the system are characterised, based on the transformation of vapour-liquid equilibrium behaviour in terms of pure components into that in terms of singular points. Once the relative volatilities of singular points are obtained, the classical Fenske-Underwood-Gilliland method can be used to design columns separating azeotropic mixtures. This method is extremely computationally efficient and can be applied to homogeneous azeotropic mixtures with any number of components; the results are useful for initialising rigorous simulations using commercial software and for assessing feasibility of proposed splits. Together with the spherical approximation of distillation boundaries, this shortcut method provides a basis for evaluating distillation sequences with recycles. Analysis of feasibility requirements of splits, component recovery requirements and the effects of recycles on the performance of proposed splits allows rules and procedures for selecting recycles to be proposed. Recycles with compositions of either singular points or mixtures of singular points are identified that are beneficial to the feasibility of sequences and the recovery of components. The principles are applicable to azeotropic mixtures with any number of components; using these procedures, recycle structures can be generated and are much simpler than the superstructures of recycle alternatives. The sequence synthesis procedure of Thong and Jobson (2001c) allows all potentially feasible sequences to be generated. To screen among these sequences, a split feasibility test and a two-step screening procedure are proposed. In the first step, feasibility of splits is tested efficiently and sequences containing either infeasible or sloppy splits are eliminated. In the second step, sequences containing sloppy splits are generated, based on the evaluation of sequences containing only feasible sharp splits. Using this procedure, the number of distillation sequences identified using the procedure of Thong and Jobson (2001c) can be significantly reduced. A systematic methodology is proposed for the synthesis and evaluation of multicomponent homogeneous azeotropic distillation sequences. The methodology is computationally efficient. It is demonstrated through a case study, the synthesis of distillation sequences separating a five-component mixture, in which two homogeneous azeotropes are formed, and for which over 5000 sequences producing pure component products can be generated. Using this methodology, only ten sequences are evaluated to identify three promising sequences. The evaluation of each sequence using the shortcut column design method is extremely efficient compared with that using the boundary value method.

Distillation is the most widespread method for separating liquid mixtures. The separation of azeotropic mixtures requires a special distillation method. My aim was to improve the batch distillation separation of azeotropic mixtures. A new algorithm was presented for the determination of product sequences of batch distillation of multicomponent azeotropic mixtures. Non-conventional configurations were studied by simulation with emphasis on closed operation. The effects of off-cut recycle on a six-batch separation process of a waste solvent mixture were also investigated. Batch extractive distillation was studied for the separation of two azeotropic mixtures. A new extractive policy was also proposed. A generalised model of batch heteroazeotropic distillation with variable decanter hold-up was developed. This model was extended for batch heterogeneous extractive distillation.

Separation of azeotropic mixtures is of great industrial importance and distillation is the dominating unit operation for such separations. However, the presence of azeotropes and non-idealities in the phase behaviour of such mixtures complicates the separation. In the pharmaceutical and fine/specialty chemical industry, the small-scale production and the requirement for flexibility indicates batch distillation as the best suited process. Among, various techniques to enhance distillation, heterogeneous azeotropic (heteroazeotropic) distillation is a very powerful and widely used one. Thus, there is a need for deeper understanding of the complex behaviour of the separation of heteroazeotropic mixtures in batch distillation columns.

This thesis is concerned with feasibility and operation aspects of heteroazeotropic distillation in different batch column configurations. Both conventional batch columns (rectifiers) and novel configurations (multivessel columns), with and without vapour bypass, are considered. The focus is on closed operations, without product removal. Batch time requirements for operation in all columns are provided for both zeotropic and heteroazeotropic mixtures. The advantages and drawbacks of each configuration are discussed and compared based on dynamic simulations. The configuration of the vapour stream in the middle vessel has an important effect on the time requirements of the process. Later on, a detailed analysis of the process is provided and previous published work concerning different operation modes and separation strategies is put under the right perspective. Simple control schemes are proposed for the practical operation of the columns and the realisation of the desired steady state results. The thesis ends with a detailed feasibility study of the process. The possibilities and limitations raised by different operational modes and separation strategies are illustrated. Simple feasibility conditions and entrainer selection rules are formulated that allow someone to investigate feasibility of the process in a systematic and comprehensive manner.

The batch distillation of crude wood oil by direct liquefaction was studied; azeotropic distillations and some characterization were also performed. It was found that 26-33 percent of the crude wood oil could be distilled by simple batch vacuum distillations with pressures from 50-300 mm Hg. With the use of ethylene glycol and glycerol 29-85 percent more oil was distilled partly due to the azeotrope formed which allows the oil to boil at a reduced pressure. The water liberated and the polymerization which took place during the distillations were studied. It was found that fluid catalytic cracking bottoms eliminates polymerization when it is co-distilled with the crude wood oil. A novel scheme for the separation of the phenolic fraction by azeotropic distillation is presented.

Separation of azeotropic mixtures is a topic of great practical and industrial interest. Most liquid mixtures of organic components form nonideal systems. The presence of some specific groups, particularly polar groups (oxygen, nitrogen, chlorine and fluorine), often results in the formation of azeotropes. Azeotropic mixtures may often be effectively separated by distillation by adding a liquid material (entrainer) to the system.

For the development of separation processes for azeotropic mixtures, there is a need for insight into the fundamental phenomena of nonideal and azeotropic phase equilibria. This thesis includes a detailed survey on azeotropic phase equilibriumdiagrams of ernarymixtures. Diagram analysis is shown to be an efficient tool for prediction of feasible separations. As a simplifying concept it is proposed that all feasible structures of ternary azeotropic phase equilibrium diagrams can be qualitatively represented by a few elementary cells of which only four have so far been reported to exist. This greatly reduces the complexity of azeotropic istillation analysis and is a key to a simple evaluation of the possibilities and limitations of azeotropic mixtures separation.

Insights gained from continuous azeotropic distillation is extended to the operation of batch distillation with focus on the dynamics and control of multivessel and extractive batch distillation as processes for separating azeotropic mixtures. Practical implications of this renewed insight for the fine- and specialty chemical industries are given in the concluding pages of the thesis.

This thesis presents a novel methodology for synthesis of sequences separating ternary heterogeneous azeotropic mixtures employing distillation columns and decanters. Column design methods are developed for assessing feasibility of proposed separations and for identifying economically attractive designs of columns in sequences. Design methods for advanced and complex configurations of heterogeneous azeotropic columns exploit the boundary value method. The methods can be used for establishing product feasibility in a column and evaluating a column design on a basis of cost. A new design method is developed for columns with integrated decanters, in which the existence of two liquid phases is not limited to the decanter. For a column with multiple heterogeneous stages, multiple feasible designs can be generated, corresponding to different numbers of heterogeneous stages and various ratios of two liquid phases on the heterogeneous stages. The resulting feasible designs have different total numbers of stages and feed locations for a given set of product specifications and reflux ratio. The new design method is extended further for double-feed columns and columns with intermediate decanters. Case studies indicate that the presence of heterogeneous liquid in columns considerably improves the economic performance in some cases. The economic performance is also affected by the number of heterogeneous stages. The number of heterogeneous stages that leads to near-optimal designs can be determined using the new column design methods. For some mixtures, employing complex column configurations makes the separation feasible and provides significant cost savings. For other mixtures, the complex columns may not be as attractive as single-feed columns with integrated decanters. Column design details and other results form the column design methods are used successfully to initialise rigorous simulations and to facilitate simulation convergence.

Thesis (MScEng)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Distillation is the most widely used separation technique in the chemical process industry and typically accounts for approximately one-third of the total capital cost and more than half of the total energy consumption of a typical petrochemical-chemical plant. Therefore, the design and optimization of the distillation sequence are of critical importance to the economics of the entire process. Azeotropic mixtures cannot be separated into their pure components via normal distillation. Enhanced distillation techniques such as heterogeneous azeotropic distillation should be considered for these mixtures. Isobaric vapour-liquid-liquid equilibrium (VLLE) data are highly important for the design and analysis of heterogeneous distillation columns. However, limited VLLE data are available in literature due to the difficulties involved with measuring such data. The objective of this work was to systematically evaluate and compare the performance of selected entrainers (including benzene, DIPE and cyclohexane) for the dehydration of C2 and C3 alcohols. To meet this objective, phase equilibrium data had to be measured. Isobaric VLLE at standard atmospheric conditions were measured with a dynamic Guillespie unit equipped with an ultrasonic homogenizer, which prevented liquid-liquid separation. Vapour-liquid equilibrium (VLE) and VLLE data were measured for ethanol/water/di-isopropyl ether (DIPE), n-propanol/water/DIPE and n-propanol/water/isooctane. The VLE data were found to be thermodynamically consistent according to the L-W (Wisniak 1993) and McDermott-Ellis consistency tests. No thermodynamic consistency test, specifically for VLLE data, could be found in literature, but the LLE part of the data followed a regular profile according to the Othmer-Tobias correlation. The binary DIPE/water and isooctane/water azeotropes, as well as ternary ethanol/DIPE/water and n-propanol/isooctane/water azeotropes, as measured in this work, agree well with those found in literature. Regressed parameters for the NRTL, UNIQUAC, and UNIFAC models, generally improved the model predictions compared with built-in Aspen parameters. This confirmed the importance of having actual measured VLLE data available for evaluation and improvement of estimations by thermodynamic models. NRTL predicted the ethanol/DIPE/water and n-propanol/DIPE/water VLLE most accurately. Despite the improved regressed parameters for n-propanol/isooctane/water predictions, the models are still considered unsuitable for accurate prediction of the VLLE behaviour of this system. Separation sequences were simulated in Aspen with built-in and regressed parameters, respectively, to illustrate the significant effect such inaccurate parameters have on these simulations. Phase diagram (VLLE data) evaluation of ethanol and isopropanol (IPA) with various entrainers, as found in literature, indicated that DIPE might be a good entrainer for the dehydration of these alcohols. Benzene and cyclohexane are generally used as entrainers in industry for these processes. Benzene is however carcinogenic and therefore an alternative has to be found (United States Department of Labour - Occupational Safety & Health Administration 2011). Separation sequences were simulated for ethanol dehydration with benzene and DIPE as entrainers, respectively. Taking cost and safety into account, DIPE can be considered an acceptable replacement for benzene as entrainer for ethanol dehydration. A separation sequence was also simulated for the dehydration of IPA with DIPE as entrainer and compared to a simulation with cyclohexane (Arifin, Chien 2007) as entrainer. DIPE was found to be a reasonable alternative to cyclohexane as entrainer for IPA dehydration. Two other separation sequences were simulated as practical examples where DIPE could be used as entrainer for the recovery of ethanol or n-propanol from aqueous Fischer Tropsch waste streams. DIPE is therefore found to be a feasible alternative entrainer to benzene and cyclohexane for the dehydration of ethanol and IPA via heterogeneous azeotropic distillation, based on pre-liminary cost considerations, separation ability and safety. Better entrainers than DIPE may exist, but from the data available in literature and the measurements made in this work DIPE appears to be superior to benzene, cyclohexane and isooctane.
AFRIKAANSE OPSOMMING: Distillasie is die mees algemeen-gebruikte skeidingstegniek in die chemiese proses-industrie. Dit is tipies verantwoordelik vir ʼn derde van die totale kapitaalkoste en meer as die helfte van die totale energie verbruik op ʼn tipiese petrochemiese chemiese aanleg. Daarom is die ontwerp en optimering van ʼn distillasie trein van kardinale belang vir die winsgewendheid van die proses. Azeotropiese mengsels kan nie slegs deur normale distillasie in suiwer komponente geskei word nie. Gevorderde distillasie tegnieke soos heterogene azeotropiese distillasie moet dus oorweeg word vir sulke mengsels. Isobariese damp-vloeistof-vloeistof ewewigsdata is een van die belangrikste fisiese eienskappe vir die ontwerp van heterogene distillasie kolomme. Die hoeveelheid damp-vloeistof-vloeistof ewewigsdata wat beskikbaar is in die literatuur is egter baie beperk omdat dit moeilik is om die data te meet. In hierdie werk is isobariese damp-vloeistof-vloeistof ewewigsdata met ʼn dinamiese Guillespie eenheid, by standaard atmosferiese druk gemeet. Die eenheid is toegerus met ʼn ultrasoniese homogeniseerder om vloeistof-vloeistof skeiding te voorkom. Temperatuur is gemeet met ʼn akkuraatheid van 0.03oC by 0oC. Die sisteem se druk is konstant gehou op 101.3 kPa met ʼn akkuraatheid van 0.35 % VSU (Vol Skaal Uitset). Die ewewigsamestellings is met ʼn relatiewe akkuraatheid van 2 % gemeet. Daar is damp-vloeistof en damp-vloeistof-vloeistof ewewigsdata van etanol/water/di-isopropiel eter (DIPE), npropanol/ water/ DIPE en n-propanol/water/iso-oktaan gemeet. Die damp-vloeistof ewewigsdata is deur die LW (Wisniak 1993) en McDermott-Ellis termodinamiese konsistensie toetse getoets en konsistent bevind. Geen termodinamiese konsistensie toets spesifiek vir damp-vloeistof-vloeistof ewewigsdata kon gevind word nie. Die Othmer-Tobias korrelasie dui egter aan dat die vloeistof-vloeistof ewewig gedeelte van die data ʼn reëlmatige gang volg. Die binêre DIPE/water en iso-oktaan/water azeotrope en ternêre etanol/DIPE/water en n-propanol/iso-oktaan/water fase-ewewigte wat in hierdie werk gemeet is, stem ooreen met die wat in die literatuur te vind is. Die parameters vir die modelle (NRTL, UNIQUAC en UNIFAC) wat in hierdie werk bestudeer is, is in die algemeen verbeter deur regressie van die eksperimentele data. Dit dui daarop dat dit belangrik is om eksperimentele damp-vloeistof-vloeistof ewewigsdata te hê om die voorspellings van termodinamiese modelle mee te evalueer en te verbeter. Die etanol/water/ DIPE en n-propanol/water/DIPE damp-vloeistof-vloeistof ewewigsdata is die akkuraatste deur NRTL voorspel. Ten spyte van die verbeteringe wat deur regressie behaal is met die NRTL en UNIQUAC parameters vir n-propanol/water/isooktaan, word hierdie modelle steeds nie as gepas vir die voorspelling van hierdie datastel beskou nie. Skeidingsreekse is gesimuleer met die ingeboude Aspen parameters en regressie parameters, onderskeidelik, om te illustreer dat onakkurate parameters ʼn beduidende effek op sulke simulasies het. Die evaluasie van fase diagramme van etanol en IPA met verskeie skeidingsagente, wat in die literatuur te vind is, dui aan dat DIPE ʼn goeie skeidingsagent kan wees vir die dehidrasie van hierdie alkohole. Skeidingsreekse vir die dehidrasie van etanol met benseen en DIPE, onderskeidelik, is gesimuleer. Met koste en veiligheid in ag geneem, is daar gevind dat DIPE ʼn aanvaarbare plaasvervanger vir benseen as skeidingsagent vir etanol dehidrasie kan wees. Daar is ook ʼn skeidingsreeks vir die dehidrasie van IPA met DIPE as skeidingsagent gesimuleer en met ʼn simulasie (Arifin, Chien 2007) wat sikloheksaan as skeidingsagent gebruik, vergelyk. Daar is bevind dat DIPE ʼn redelike alternatief vir sikloheksaan kan wees as skeidingsagent vir IPA dehidrasie. Nog twee skeidingsreekse is gesimuleer om as praktiese voorbeelde te dien van die gebruik van DIPE as skeidingsagent om etanol of n-propanol vanaf waterige Fischer-Tropsch afvalstrome te herwin. Daarom is daar bevind dat DIPE ʼn geldige alternatiewe skeidingsagent vir benseen en sikloheksaan is, gebaseer op koste, skeidingsvermoë en veiligheid. Daar kan beter skeidingsagente as DIPE bestaan, maar vanuit die data beskikbaar in literatuur en die metings geneem in hierdie werk, is DIPE die beste.

Thesis (MEng)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: The operation and optimisation of a distillation train directly effects the total energy consumption of a typical processing plant. With this in mind, the efficient separation of low molecular weight alcohol azeotropes, using heterogeneous azeotropic distillation, is of great economic and environmental importance. Heterogeneous azeotropic distillation involves the addition of an extraneous component, known as an entrainer, to the mixture to facilitate separation. Benzene has long been replaced as the entrainer of choice, due to its carcinogenic nature, and research into finding a more suitable entrainer has commenced. To determine if an entrainer is suitable for a particular separation, detailed phase behaviour information of the ternary alcohol/entrainer/water system is required; vapour-liquid (VLE), vapour-liquid-liquid (VLLE) equilibria data and the composition of all azeotropes present. This is complicated by the fact that thermodynamic models (like the nonrandom two-liquid (NRTL), universal functional (UNIFAC) and universal quasichemical (UNIQUAC) activity coefficient models) often fail to predict the phase equilibria of ternary systems. The lack of available experimental phase equilibria data, and the inability of thermodynamic models to predict phase equilibria data, has fueled the need for the experimental determination of accurate, repeatable isobaric VLE, VLLE and azeotropic data. With this in mind, this research is focused on the experimental determination of VLE, VLLE and azeotropic data for three low molecular weight alcohol/entrainer/water systems at 101.3 kPa. Following an extensive literature study on azeotropes, applicable separation techniques and available VLE and VLLE data in literature, the ethanol/2-butanone/water, n-propanol/2-butanone/water and iso-propanol/2-butanone/water systems were chosen for experimental investigation. The experimental determination was carried out in a Gillespie type still, equipped with an ultrasonic homogenizer. The temperature and pressure accuracies of the equipment were found to be 0.03°C and 2mbar respectively. The chosen experimental methodology was verified, and its repeatability tested, through the measurement of isobaric VLE and VLLE data of ethanol/isooctane, ethanol/n-butanol/water and n-propanol/isooctane/water systems at 101.3 kPa and subsequent comparison of the measured data with literature data. The compositional error reported, taking into account experimental and analysis effects, is ±0.014 mole fraction. All experimentally determined data sets, verification and new data, were tested for thermodynamic consistency by using the Wisniak modification of the Herrington test, the L/W consistency test, as well as the McDermott-Ellis consistency test, and found to be consistent. The Othmer-Tobias correlation was used to ensure the measured LLE data followed a steady trend, with all R-values larger than 0.910. For all three of the new systems chosen, the absence of ternary heterogeneous azeotropes was noted. The presence of a ternary homogeneous azeotrope was found for both the ethanol/2-butanone/water and iso-propanol/2-butanone/water systems. No ternary azeotropes are present for the n-propanol/2-butanone/water system. Suitable entrainers were compared to 2-butanone (MEK) by plotting measured data and literature information of five similar alcohol/entrainer/water systems on a ternary phase diagram. It was found that MEK could not be considered as a suitable entrainer for heterogeneous azeotropic distillation of ethanol, n-propanol and IPA. This is due to the absence of a ternary heterogeneous azeotrope for the aforementioned alcohol/MEK/water systems. Finally, the ability of thermodynamic models (NRTL, UNIFAC and UNIQUAC) to predict experimental data was determined both visually and through descriptive statistics. This entailed the inspection of ternary phase diagrams and the calculation and evaluation of average absolute deviation (AAD) and and average absolute relative deviation (AARD%) values. The measured data were modelled in Aspen Plus®. It was found that none of the models could predict the ternary systems with acceptable accuracy and the data were regressed. In general, the regressed parameters for the NRTL, UNIFAC and UNIQAC models improved the model predictions when compared to the built-in Aspen parameters. The UNIFAC model predicted the ethanol/MEK/water and n-propanol/MEK/water systems most accurately while none of the models could predict the IPA/MEK/water systems with acceptable accuracy.
AFRIKAANSE OPSOMMING: Die ontwerp en optimering van 'n distillasietrein het ‘n duidelike effek op die totale energieverbruik van ‘n tipiese prosesaanleg. Met dit in gedagte, is ‘n meer doeltreffende skeiding van lae molekulêre massa alkohol aseotrope, met behulp van heterogene aseotropiese distillasie, voordelig vir die ekonomie en die omgewing. Heterogene aseotropiese distillasie behels die toevoeging van 'n eksterne komponent, wat bekend staan as 'n skeidingsagent, om uiteindelik die skeiding te fasiliteer deur die komponente se dampdrukke te verander. Benseen was in die verlede ‘n gewilde skeidingsagent, maar dit is a.g.v. sy karsenogeniese eienskappe nie meer aanvaarbaar om te gebruik nie. Nuwe navorsing in hierdie veld fokus dus onder andere op die identifisering van meer geskikte skeidingsagente. Om te bepaal of 'n skeidingsagent geskik is, word indiepte fasegedrag inligting benodig, i.e. damp-vloeistof en damp-vloeistof-vloeistof ewewigsdata en die samestelling van alle aseotrope teenwoordig. Ongelukkig kan termodinamiese modelle dikwels nie die fasegedrag van ternêre stelsels voorspel nie. Dit, sowel as die beperkte beskikbaarheid van eksperimentele ewewigsdata in die literatuur, het dus hierdie navorsing aangevuur. Die projek het gefokus op die experimentele bepaling van damp-vloeistof en damp-vloeistof-vloeistof ewewigsdata en aseotropiese data vir drie alkohol/skeidingsagent/water-stelsels by 101.3 kPa. Na ‘n indiepte literatuurstudie van aseotrope, gepaste skeidingstegnieke en beskikbare damp-vloeistof en damp-vloeistof-vloeistof ewewigsdata, is 2-butanone (MEK) gekies as ‘n moontlike skeidingsagent en die etanol/MEK/water-, n-propanol/MEK/water- en iso-propanol/MEK/water-stelsels gekies vir eksperimentele ondersoek. Die data is met ‘n dinamiese Gillespie eenheid gemeet, toegerus met ‘n ultrasoniese homogeniseerder om vloeistof-vloeistof skeiding te voorkom. Die akkuraatheidsbande van temperatuur- en druk meetinstrumente was 0,03°C en 2 mbar, onderskeidelik. Die eksperimentele metode en die herhaalbaarheid van metings is bevesting, deur die isobariese damp-vloeistof en damp-vloeistof-vloeistof ewewigsdata van etanol/iso-oktaan, etanol/n-butanol/water en n-propanol/iso-oktaan/water te vergelyk met onafhanklike stelle ooreenstemmende data uit die literatuur. Die gesamentlike eksperimentele en analitiese fout wat gemaak kon word tydens bepaling van molfraksie samestellings was ±0.014 molfraksie. Alle gemete eksperimentele data is getoets vir termodinamiese samehang deur middel van beide die L/W en McDermott-Ellis konsekwentheidstoetse. Die Othmer-Tobias korrelasie is gebruik om seker te maak dat die gemete LLE data ‘n konstante tendens volg, met alle R-waardes groter as 0.910. Vir al drie van die nuwe stelsels wat gekies is, was ‘n drieledige heterogene aseotroop afwesig. Die teenwoordigheid van drieledige homogene aseotrope is egter waargeneem vir die etanol/MEK/water- en IPA/MEK/water-stelsels. Geen drieledige aseotrope is vir die n-propanol/MEK/water-sisteem gevind nie. Alle gemete data, asook literatuur inligting van vyf soortgelyke alkohol/skeidingsagent/water sisteme, is op ‘n drieledige fase diagram voorgestel om die skeidingsagente met mekaar te vergelyk. Hiervolgens word dit getoon dat MEK nie as ‘n gepaste skeidingsagent vir heterogene aseotropiese distillase beskou kan word nie a.g.v. die afwesigheid van ‘n drieledige heterogene aseotroop in die voorgenoemde alkohol/MEK/waterstelsels. Die vermoë van die termodinamiese modelle (NRTL, UNIFAC en UNIQUAC) om die eksperimentele data te voorspel is visueel (per grafiek) sowel as deur beskrywende statistiek bepaal. Dit behels die inspeksie van drieledige fasediagrame en die berekening en evaluasie van die gemiddelde absolute afwyking en gemiddelde absolute relatiewe afwykingswaardes. Hierdie teoretiese data is met Aspen Plus® bepaal. Nie een van die modelle kon die drieledige stelsels se fasegedrag met aanvaarbare akkuraatheid voorspel nie. Die parameters vir die NRTL-,UNIFAC- en UNIQUAC-modelle kan verbeter word deur middel van regressie, in vergelyking met die ingeboude Aspen parameters. Dit is bevind dat die UNIFAC model die etanol/MEK/water- en n-propanol/MEK/water-stelsel die beste kan voorspel. Nie een van die bogenoemde modelle kon egter die fasegedrag van die IPA/MEK/water-stelsel voorspel nie.

1. Reaction-separation interactions: A waste minimisation approach to process design that promotes opportunistic recycling and includes a systematic technique for designing a recycle network in the context of an overall process. 2. Azeotropic separation systems: (a) A novel geometric approach for synthesis of cleaner and cost effective distillation sequences for homogeneous azeotropic mixtures with and without boundary crossing. Important insights include: • a geometric approach for synthesizing and screening the alternative separation sequences which results in a catalogue pairing the RCMs of the ternary systems with their most promising separation sequences: • a novel procedure for entrainer minimisation for azeotropic distillation sequences, and • new evidences linking the type of separation sequence, the azeotropic column feedstage location and the volatility of an entrainer with the separability of homogeneous azeotropic mixtures. These findings conclusively explain the peculiar dependencies of the separability of homogeneous azeotropic mixtures on the reflux ratio and the number of stages. (b) A geometric approach for synthesis of cost effective distillation sequences for heterogeneous azeotropic mixtures which enables the graphical prediction of the absolute minimum number of units, the region and the point of desirable entrainer flowrate, the optimum decanter tie line position, and the distillate composition for the entrainer recovery column. (c) Guidelines for exploiting feed composition flexibility to improve azeotropic separation based on a novel geometric approach. Important insights include: • the significance of the binary, ternary and desirable ternary feed compositions, and a procedure to achieve the desirable ternary feed composition. • the development of a selection catalogue for feed preconcentration based on a novel geometric approach. • the use of mixing and recycling for grassroot design and retrofit.

O trabalho visa substituir processos comercialmente usados na indústria para purificação da glicerina obtida a partir de biodiesel. A purificação da glicerina até grau técnico ou P.A. (99,5 % em massa) implica em um grande consumo de energia nos processos de evaporação e destilação, pela necessidade de altos vácuos. Como alternativa, a desidratação da glicerina pode ser realizada por destilação azeotrópica heterogênea usando baixas temperaturas e a pressão atmosférica. O objetivo deste trabalho foi estudar a viabilidade técnica do processo de desidratação da glicerina por meio da destilação azeotrópica com tolueno e comparar o consumo de energia com os processos tradicionais. Para atingir o objetivo, avaliou-se a influencia das variáveis de processo: vazão de alimentação de glicerina (g/s) (X1 codificado), vazão de alimentação do vapor de tolueno (g/s) (X2 codificado), concentração inicial de glicerina (% em massa) (X3 codificado), temperatura de alimentação da glicerina (°C) (X4 codificado), na concentração final de glicerina. A construção do modelo foi feita a partir de um planejamento fatorial composto de segunda ordem, usando glicerina P.A. A concentração final foi estimada mediante o índice de refração e massa específica. Obteve-se o seguinte modelo: 2 1,96X2 13,18X3 6,42X1X3 2,24X2X3 1 %GLI = 79,42 8,88X1 + 4,72X + + + que mostrou que a temperatura de alimentação (X4 codificada) não exerceu influencia na concentração final de glicerina. Observou-se pelo modelo que é preferível utilizar valores máximos de X2.e mínimos de X1. Com estes ensaios foi possível obter uma glicerina 99% pura, porém apresentava um ligeiro cheiro de tolueno, que foi eliminado mediante arraste com ar (stripping). Para verificar o modelo empregou-se glicerina bruta oriunda do biodiesel previamente tratada. O processo prévio consistiu de: acidificação, neutralização, salting out com isopropanol, evaporação do álcool e troca iônica. A glicerina obtida após o processo de troca iônica, aparentemente só água e glicerina com 38,6 % em massa, foi usada para a verificação do modelo. Obteve-se por destilação azeotrópica uma glicerina com 92 % em massa, quando o valor predito pelo modelo foi 99 %. Esta glicerina tratada apresentou um desvio do modelo devido a presença de resíduos de sabões, porém ficou demonstrado a possibilidade de desidratação de glicerina por este processo necessitando apenas de melhorias nas etapas de purificação até a troca iônica. Também, avaliou-se a eficiência da coluna comparando a separação dada pela coluna com a dada por um único estágio de equilíbrio nas mesmas condições de vazão e concentração, concluindo-se que era da ordem de 10 %. Finalmente, este processo consome cerca de 57,72 % de energia em relação aos processos de evaporação e destilação a vácuo tradicionalmente usados.
This study aims to replace commercially processes used in industry for glycerine purification obtained from biodiesel. The purification of glycerine up to technical degree or PA (99.5% by weight) involves a large consumption of energy in the evaporation and distillation processes due to need operate at high vacuum. Alternatively, dehydration of glycerine can be achieved by heterogeneous azeotropic distillation using low temperature and atmospheric pressure. The objective of this work was to study the technical feasibility of the dehydration process of glycerine through azeotropic distillation with toluene and compare the energy consumption with traditional processes. To reach this objective, the influence of process variables: feed flow rate of glycerine (g/s) (X1 coded), feed flow rate of steam toluene (g/s) (X2 coded), initial concentration of glycerine (% by weight) (X3 coded), the temperature of food glycerine (°C) (X4 coded) has been studied in the final concentration of glycerine. The empirical model was built through fitting of data obtained from a factorial second order design, using glycerine PA. The final concentration was estimated by refractive index and density. The fitted model was: 2 1,96X2 13,18X3 6,42X1X3 2,24X2X3 1 %GLI = 79,42 8,88X1 + 4,72X + + + The model appoints that the feed (inlet glycerine solution) temperature (X4 coded) had no influence in the outlet concentration of glycerine. Moreover, it has been observed that is better to use maximum X2.and minimum X1. From these tests were possible to obtain a glycerine 99% purely, but it had a light smell of toluene, which was removed by stripping with air. In order to verify the empirical model, it has been used raw glycerine from biodiesel production. This glycerine was previously treated following the steps: acidification, neutralization, salting out with isopropanol, evaporation of isopropanol and ion exchange. The obtained glycerine after the process of ion exchange, presented 38.6% in weight, apparently only glycerine in water, has been used to check the model. Content of glycerine by this distillation was 92% in weight, when the predict value by the model was 99%. The deviation from the model was due to the presence of soap residues, but it has been demonstrated the possibility of dehydration of glycerine by this process requiring only some improvements in purification steps up to the ion exchange. In addition, it has been estimated the column efficiency by comparison of the separation in both column and single stage at the same flow rate and concentration conditions, concluding that it was 10 %. Finally, this process consumes approximately 57.72% of energy in relation to the processes of evaporation and vacuum distillation traditionally used.

Implantées depuis plus de dix ans dans l’industrie, l’intérêt des colonnes à cloison n’est aujourd’hui plus à démontrer. Suivant les applications envisagées, elles peuvent permettre d’important gain tant énergétique qu’économique. Cependant leur design est toujours complexe et les méthodes de conception développées ne s’adressent qu’à des applications avec des mélanges proches de l’idéalité. Le développement d’une nouvelle méthode de design d’une colonne à distillation de mélanges non-idéaux applicable aux colonnes à cloison constitue l’objet d’étude de cette thèse. Dans un premier temps, une procédure de faisabilité et de design d’une colonne classique basée sur les feuilles opératoires a été proposée. Les paramètres de design obtenus sont ensuite utilisés comme initialisation d’une simulation rigoureuse conduite au sein du logiciel Prosim Plus. Afin de tester cette procédure, des mélanges idéaux, non-idéaux et azéotropiques ont été utilisés. Il a pu être montré que les paramètres de design obtenus permettent d’accéder à un design plus fiable et plus efficient, aussi bien d’un point de vue énergétique qu’économique, que ceux obtenus par la bien connue méthode shortcut FUGK. Dans un second temps, la procédure a été adaptée aux colonnes à cloison. Les paramètres obtenus ont également servi à initialiser une simulation rigoureuse et la procédure a été testée avec les mêmes mélanges. Il a été mis en évidence que les paramètres de design obtenus permettaient d’obtenir une bonne initialisation de la colonne. Comparée avec une autre méthode développée précédemment par le laboratoire, la procédure développée s’est révélée plus fiable et a permis l’obtention de design plus économique tant du point de vue énergétique qu’en termes d’investissement. Enfin, une phase de validation expérimentale a également été réalisée sur une installation pilote. Dans un premier temps, l’instrumentation et le contrôle de la colonne ont été fortement améliorés. Dans un second temps, des résultats expérimentaux réalisés sur avec un mélange hétéro-azéotropique ont pu valider des simulations en terme de profils de composition et de température interne ainsi que les compositions et les débits de sortie de la colonne.

Orientador: Maria Regina Wolf Maciel
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-18T13:50:07Z (GMT). No. of bitstreams: 1 JaimesFigueroa_JaiverEfren_M.pdf: 4284661 bytes, checksum: 5b7383def90a5143160bc892b406c75c (MD5) Previous issue date: 2011
Resumo: A produção de etanol a partir da cana de açúcar é uma tecnologia dominada completamente pelo Brasil porém, encontra-se na etapa de intensificação, otimização e inovação. O etanol pode ser produzido como hidratado ou anidro, sendo necessário, para produção deste último, um processo posterior de desidratação. Existem inúmeros processos de desidratação, dentre dos quais a destilação extrativa é um dos mais simples de realizar. A destilação extrativa usa um solvente para modificar o equilíbrio líquido-vapor, permitindo quebrar o azeótropo etanol/água que impede que a desidratação seja feita por destilação convencional. O solvente de extração é de grande importância, dele depende a facilidade com que vai ser feita a separação, a quantidade a ser utilizada e o requerimento energético do processo. Nesse contexto, aparecem os líquidos iônicos, que são apresentados como ótimos solventes potenciais de extração; um líquido iônico (LI) é um sal composto por um cátion orgânico com pelo menos uma carga deslocada e um ânion inorgânico; sua estrutura evita que se forme uma rede cristalina estável, resultando em solventes líquidos altamente iônicos com temperaturas de fusão inferiores a 100 °C e com insignificante pressão de vapor. Os LI são principalmente usados em substituição aos solventes convencionais, podendo ser uma alternativa para diminuir a poluição ambiental, evitando a emissão de componentes orgânicos voláteis ao meio ambiente. Com a justificativa anterior, o objetivo desta dissertação foi analisar e otimizar o processo de obtenção de etanol anidro a partir da mistura etanol + água de composição pré-azeotrópica, empregando líquidos iônicos (LI), visando avaliar seu potencial; os LI estudados foram: 1-butil-3-metilimidazólio cloreto, 1-butil-3-metilimidazólio metilsulfato, 1-butil-3-metilimidazólio acetato, 1-butil-3-metilimidazólio tetrafluoroborato, 1-butil-3-metilimidazólio dicianamida, 1-etil-3-metilimidazólio cloreto, 1-etil-3-metilimidazólio tetrafluoroborato, 1-hexil-3-metilimidazólio cloreto. Neste trabalho foi encontrado o requerimento energético e a quantidade de LI a ser empregado para obter os valores máximos de pureza e porcentagens de recuperação de etanol e água. A influência das condições de operação e desenho utilizadas, tais como fração de etanol na alimentação, relação LI:alimentação, temperatura da alimentação e do LI de reposição, quantidade de estágios, relação molar de refluxo, estágio de alimentação e vazão molar de destilado da coluna de recuperação de etanol e de purificação de LI, foram analisadas empregando o simulador comercial Aspen Plus e, otimizadas empregando a técnica de delineamento de experimentos. Todos os LI estudados apresentaram capacidade de desidratar o etanol, elevando sua concentração de pré até pós-azeotropia, obtendo-se pureza de etanol maiores que 0,995 em massa. Além disso, dependendo do LI utilizado, o processo atinge porcentagens de recuperação de etanol e água, em média, de 98% e 74%, respectivamente. Na definição do modelo para o coeficiente de atividade do equilíbrio ternário líquido vapor da mistura etanol + água + LI foram testados o NRTL e UNIQUAC, chegando-se à conclusão de que o equilíbrio representado pelo modelo de NRTL é o mais adequado
Abstract: The production of ethanol from sugar cane is a technology led and dominated by Brazil. However, it is still in a stage of optimization and innovation. Ethanol can be produced in a hydrated or dehydrated state, but the latter requires an additional process to the conventional distillation. There are numerous dehydration processes that can be implemented, but the extractive distillation is one of the most simple. Extractive distillation uses a solvent that modifies the liquid-vapor equilibrium and eliminates the presence of the ethanol-water azeotrope that prevents the use of conventional distillation for the dehydration process. The solvent for the extraction is of great importance since it dictates the degree of separation and the energy requirements for the process. In this context, ionic liquids are considered since they have been presented as excellent solvents for extraction. An ionic liquid (IL) is a salt formed by an organic cation with at least one delocalized charge, and an inorganic anion. The structure of the ionic liquids prevents the formation of a stable crystalline net, resulting in highly ionic liquid solvents that have melting points below 100 ºC and negligible vapor pressures. With those characteristics, ionic liquids can be a replacement for conventional solvents offering alternatives for the decrease of the environmental impact by preventing the emissions of volatile compounds to the environment. With the previous justification, the objective of this master dissertation was to analyze and optimize the process of obtaining anhydrous ethanol from a mixture ethanol + water with pre-azeotropic composition by using ionic liquids; and also to evaluate their performance in this application to evaluate its potential. Ionic liquids were studied: 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-hexil-3-methylimidazolium chloride. In this work, the minimum energy requirement and the amount of ionic liquid needed to obtain maximum ethanol purity and maximum recovery of ethanol and water exiting the process were found. The influence of the design and operation conditions used, such as the ethanol composition in the feed, the IL/feed ratio, the temperature of the feed and the IL, the number of plates, the reflux molar ratio and the distilled flux in the columns of purification of ethanol and recovery of ionic liquids were studied using the commercial simulator ASPEN PLUS, and optimized by utilization of the design of experiments (DOE) technique. All the ionic liquids used were able to dehydrate the ethanol, increasing its concentration from pre to post azeotrope, generating ethanol with purity above 0.995 in mass. In addition to that, depending on the ionic liquid used, the process reached average water and ethanol recoveries of 98% and 74% respectively. In the definition of the model for the activity coefficient in the ternary vapor-liquid equilibrium of the ethanol-water-IL mixtures, the models NRTL and UNIQUAC were studied concluding that the NRTL model was the most adequate
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química

Thesis (PhD)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Data on the process performance at different operating conditions are required to determine the feasibility of a separation process. Such data can be experimentally measured, but due to the time and costs associated with pilot plant scale experiments, the use of predictive process models are often preferred. The main aim of this project is to establish a working process model in Aspen Plus® that can be used to predict the separation performance of a supercritical fluid fractionation process aimed at the separation of mixtures of detergent range alkanes and alcohol isomers where similar boiling points or low relative volatilities can occur. Currently, an azeotropic distillation process is employed for the separation of detergent range alkanes and alcohols. Although this process shows good separation performance, some concerns regarding the operating conditions are raised: the preferred entrainer, diethylene glycol, is toxic to humans; very low operating pressures of 0.016 – 0.031 MPa and high temperatures of 473 K are required; additional processing units and materials are required to remove the entrainer from the product streams. An alternative process, supercritical fluid fractionation, is proposed in this work after previous studies have reported that this process have potential for the separation of alkanes and alcohols. The supercritical fluid fractionation process addresses the concerns of the azeotropic distillation process in the following ways: a non-toxic solvent, CO2, is used as the separating agent; mild temperatures of 344 K is proposed, but at the cost of the low operating pressures of the azeotropic process; and a single process unit and no additional material is required to separate the solvent from the product streams. A process model was developed in Aspen Plus® to evaluate the separation performance of the newly proposed supercritical fluid fractionation process and compare it to the current azeotropic distillation process. The development of the process model included the development of an accurate thermodynamic model in Aspen Plus®. After thorough evaluation of a number of cubic equations of state, the RK-ASPEN model was found to be superior in its representation and prediction of phase transition pressures for multi-component mixtures of detergent range alkanes and alcohols in the temperature range 318 – 348 K. Phase transition pressures could be predicted with an error of less than 6 % with the inclusion of regressed polar parameters and binary solute-solvent interaction parameters for two multi-component mixtures: CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol) and CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol). Polar parameters were regressed from pure component vapour pressure data predicted with correlations available in Aspen Plus®. Binary interaction parameters were regressed from experimental bubble and dew point data. Binary bubble and dew point data were measured for a number of systems containing ethane or CO2 and a C10-alkane or C10-alcohol isomer at temperatures between 308 K and 353 K, and compositions ranging between 0.01 and 0.7 mass fraction solute. A comparison between the phase equilibrium data measured for these systems revealed that the structure of the molecule, and not only the molecular weight, influences its solubility in the supercritical solvent. The phase transition pressures of n-decane, 2-methylnonane, 3-methylnonane and 4-methylnonane did not differ significantly in CO2 or ethane, and these compounds will in all likelihood not be separated in a supercritical fluid fractionation process. The phase transition pressures measured for the C10-alcohol isomers decreased in both CO2 and ethane in the following order: 1-decanol, 3,7-dimethyl-1-octanol, 2-decanol, 2,6-dimethyl-2-octanol and 3,7-dimethyl-3-octanol. The position of the hydroxyl group and the number, length and position of the side branches, all influence the solubility behaviour and phase transition pressures of the isomeric alcohols in the supercritical solvent. Since the use of ethane did not show any significant benefits with regard to selectivity, the use of the less harmful and less expensive solvent, CO2, in further investigations was justified. The RK-ASPEN thermodynamic model, with the inclusion of the regressed polar and binary solute-solvent interaction parameters, was implemented in the process model and the separation performance of the process was simulated at different operating conditions for the CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) mixture. A comparison to experimental pilot plant data revealed that the model cannot be used to predict the separation performance at low fractionation temperatures (316 K) due to shortcomings in the thermodynamic model. However, the performance of the process at high fractionation temperatures (344 K) could be predicted well, with an error of 10 – 36 %. Simulations for the CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) and CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol) mixtures showed that the composition of the feed mixture have a significant effect on the location and size of the operating window and optimum operating conditions. The optimum operating conditions were defined as the conditions where an acceptable selectivity ratio and alcohol recovery occurred simultaneously. Since the selectivity ratio and alcohol recovery have opposing optimization approaches, a number of possible optimum operating conditions exist, based on the product specifications. When an alcohol and an alkane with similar phase behaviour exist in a mixture, a distinct minimum selectivity ratio will occur at a point within the extract-to-feed ratio limits of the process. When the alkanes and alcohols present in a mixture do not have similar or overlapping phase transition pressures, the minimum selectivity ratio will typically cover a small range of extract-to-feed ratios at the high end limit of the extract-to-feed ratio range. To summarize: A process model was established in Aspen Plus® that can be used to determine the feasibility and separation performance of a supercritical fractionation process for a feed mixture of detergent range alkane and alcohol isomers. The model was used to prove that an SFF process is a feasible alternative process to consider for the removal of alkanes from mixtures of detergent range alcohol isomers, even where overlapping boiling points or low relative volatilities occur. During the development of the process model, the following significant novel contributions were made: · New phase equilibrium data were measured for C10-alkane and C10-alcohol isomers in supercritical ethane, as published in The Journal of Supercritical Fluids 58 (2011) 330 – 342. · New phase equilibrium data were measured for C10-alkane and C10-alcohol isomers in supercritical CO2, as published in The Journal of Supercritical Fluids 59 (2011) 14 – 26. · A thermodynamic model was developed in Aspen Plus® that can accurately predict the phase transition pressures of binary, ternary and multi-component mixtures of detergent range alkanes and alcohols in supercritical CO2, as published in The Journal of Supercritical Fluids 84 (2013) 132 – 145. · A process model was developed in Aspen Plus® that can be used to predict the separation performance of a supercritical fluid fractionation process for the separation of mixtures of detergent range alkanes and alcohols. · Experimental and simulated results indicated that a supercritical fluid fractionation process can be implemented successfully to separate an alkane from a mixture of alcohol isomers, as was shown for two mixtures: CO2 + (25 % n-decane + 25 % 1-decanol + 25 % 3,7-dimethyl-1-octanol + 25 % 2,6-dimethyl-2-octanol) and CO2 + (20 % n-dodecane + 70 % 1-decanol + 10 % 3,7-dimethyl-1-octanol).
AFRIKAANSE OPSOMMING: Data oor die omvang van skeiding by verskillende bedryfstoestande word benodig om die lewensvatbaarheid van ’n skeidingsproses te bepaal. Sulke data kan eksperimenteel gemeet word, maar as gevolg van die tyd en kostes geassosieer met eksperimente op loodsaanlegskaal, word die gebruik van prosesmodelle verkies. Die hoofdoel van hierdie projek is om ’n werkende prosesmodel, wat daarop gemik is om C8 – C20 alkane en alkohol isomere te skei, in Aspen Plus® tot stand te bring om die omvang van die skeiding van ’n superkritiese fraksioneringsproses te meet. Tans word azeotropiese distillasie gebruik vir die skeiding van C8 – C20 alkane en alkoholisomere. Alhoewel goeie skeiding met hierdie proses bewerkstellig word, is daar sekere eienskappe van die proses wat aandag vereis: die voorgestelde skeidingsagent, dietileen glikol, is giftig vir mense; baie lae bedryfsdrukke van 0.016 – 0.031 MPa en hoë temperature van 473 K word benodig; addisionele proseseenhede en materiaal is nodig om die skeidingsagent van die produkte te verwyder. Die gebruik van ’n alternatiewe proses - superkritiese fraksionering - word in hierdie werk voorgestel nadat vorige studies getoon het dat hierdie proses die potensiaal het om alkane en alkohole te skei. Die superkritiese fraksioneringsproses spreek al die kommerwekkende eienskappe van azeotropiese distillasie aan soos volg: ’n veilige oplosmiddel, CO2, word as die skeidingsagent gebruik; gemiddelde temperature van 344 K word voorgestel, maar ten koste van lae bedryfsdrukke; ’n enkele proseseenheid en geen addisionele materiaal word benodig om die oplosmiddel van die produkte te skei nie. ’n Prosesmodel is in Aspen Plus® ontwikkel om die omvang van die skeiding wat deur die voorgestelde superkritiese fraksioneringsproses teweeggebring is, te evalueer en te vergelyk met die azeotropiese distillasieproses wat tans in gebruik is. Die ontwikkeling van die prosesmodel sluit die ontwikkeling van ’n akkurate termodinamiese model in Aspen Plus® in. Na deeglike evaluasie van ’n aantal kubiese toestandsvergelykings is gevind dat die RK-ASPEN-model die faseoorgangsdrukke van multi-komponentmengsels van C8 – C20 alkane en alkohole die beste voorspel binne die temperatuurbereik van 318 – 348 K. Faseoorgangsdrukke kon voorspel word met ’n fout van minder as 6 % met die insluiting van voorafbepaalde polêre parameters en binêre interaksie-parameters vir twee multi-komponentmengsels: CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol) and CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol). Polêre parameters is bepaal met dampdruk data, wat voorspel is met korrelasies in Aspen Plus®. Binêre interaksieparameters is van eksperimentele faseoorgangsdata bepaal. Binêre faseoorgangsdata is vir ’n aantal sisteme wat uit etaan of CO2 en ’n C10-alkaan- of C10-alkohol-isomeer bestaan, gemeet by temperature tussen 308 K en 353 K en samestellings van tussen 0.01 en 0.7 massafraksie van die opgeloste stof. ’n Vergelyking tussen die gemete fase-ewewigsdata het onthul dat die struktuur van die molekuul, en nie net die molekulêre massa nie, die oplosbaarheid van die stof in die superkritiese oplosmiddel beïnvloed. Die faseoorgangsdrukke van n-dekaan, 2-metielnonaan, 3-metielnonaan en 4-metielnonaan het geen skynbare verskille getoon in etaan of CO2 nie en dus sal hierdie stowwe in alle waarkynlikheid nie met ’n superkritiese fraksioneringsproses geskei kan word nie. Die faseoorgangsdrukke wat vir die C10-alkohol gemeet is, het in beide etaan en CO2 afgeneem in die volgende volgorde: 1-dekanol, 3,7-dimetiel-1-oktanol, 2-dekanol, 2,6-dimetiel-2-oktanol en 3,7-dimetiel-3-oktanol. Die posisie van die hidroksielgroep en die aantal, lengte en posisie van die sytakke beïnvloed die oplosbaarheidsgedrag van die alkohol-isomere in die superkritiese oplosmiddel. Aangesien die gebruik van etaan nie enige voordele ten opsigte van selektiwiteit inhou nie, is die gebruik van die minder skadelike en goedkoper oplosmiddel, CO2, vir verdere ondersoeke geregverdig. Die ontwikkelde termodinamiese model, met die insluiting van die polêre parameters en binêre interaksieparameters, is in die prosesmodel ingesluit en die omvang van die skeiding van die proses is gesimuleer by verskillende bedryfstoestande vir die CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) mengsel. ’n Vergelyking tussen die gesimuleerde data en die eksperimentele loodsaanlegdata het onthul dat die model nie die omvang van die skeiding kan voorspel by lae fraksioneringstemperature (316 K) nie as gevolg van die tekortkominge in die termodinamiese model. Die omvang van die skeiding by hoë temperature (344 K) kon egter goed voorspel word met ’n fout van 10 – 36 %. Simulasies van die CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) en CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol) mengsels het getoon dat die samestelling van die voermengsel ’n beduidende effek op die grootte van die bedryfsvenster en optimum bedryfstoestande het. Die optimum bedryfstoestande word gedefinieer as die toestande waar ’n aanvaarbare selektiwiteitsverhouding en alkoholherwinning terselfdertyd voorkom. Aangesien die selektiwiteitsverhouding en alkoholherwinning teenstrydige optimeringsbenaderings het, bestaan daar ’n aantal optimum bedryfstoestande gebaseer op die produkspesifikasies. Wanneer ’n alkohol en ’n alkaan met ooreenstemmende fasegedrag saam in ’n mengsel voorkom, bestaan daar ’n duidelike minimum selektiwiteitsverhouding by ’n punt binne die ekstrak-tot-voer-verhoudingslimiete van die proses. Wanneer die alkane en alkohole in ’n mengsel nie ooreenstemmende fasegedrag toon nie, sal die minimum selektiwiteitsverhouding oor ’n reeks ekstrak-tot-voer-verhoudings voorkom, tipies by die hoë limiet van die ekstrak-tot-voer-verhoudingsreeks. Om op te som: ’n Prosesmodel is in Aspen Plus® tot stand gebring wat die lewensvatbaarheid en omvang van die moontlike skeiding van ’n superkritiese fraksioneringsproses vir voermengsels van C8 – C20 alkane en alkohol-isomere kan voorspel. Die model is gebruik om te bewys dat ’n superkritiese proses ’n lewensvatbare alternatiewe proses is om te oorweeg vir die verwydering van alkane uit mengsels van alkohol-isomere, self waar ooreenstemmende kookpunte of lae relatiewe vlugtigheid tussen komponente voorkom. Tydens die ontwikkeling van die prosesmodel is die volgende beduidende nuwe bydraes gemaak: · Nuwe fase-ewewigsdata is gemeet vir C10-alkaan- en C10-alkohol-isomere in superkritiese etaan, soos gepubliseer in The Journal of Supercritical Fluids 58 (2011) 330 – 342. · Nuwe fase-ewewigsdata is gemeet vir C10-alkaan and C10-alkohol isomere in superkritiese CO2, soos gepubliseer in The Journal of Supercritical Fluids 59 (2011) 14 – 26. · ’n Termodinamiese model is ontwikkel in Aspen Plus® wat die faseoorgangsdrukke van binêre, ternêre en multi-komponent mengsels van C8 – C20 alkane en alkohol-isomere in superkritiese CO2 akkuraat kan voorspel, soos gepubliseer in The Journal of Supercritical Fluids 84 (2013) 132 – 145. · ’n Prosesmodel is ontwikkel in Aspen Plus® wat die omvang van die moontlike skeiding van ’n superkritiese fraksioneringsproses, gemik op die skeiding van mengsels van C8 – C20 alkane en alkohol-isomere, kan voorspel. · Eksperimentele en gesimuleerde resultate toon aan dat ’n superkritiese fraksioneringsproses suksesvol geïmplementeer kan word vir die skeiding van ’n alkaan vanuit ’n mengsel van alkohol-isomere, soos bewys vir twee mengsels: CO2 + (25 % n-dekaan + 25 % 1-dekanol + 25 % 3,7-dimetiel-1-oktanol + 25 % 2,6-dimetiel-2-oktanol) en CO2 + (20 % n-dodekaan + 70 % 1-dekanol + 10 % 3,7-dimetiel-1-oktanol).

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Capes
Grande parte das indústrias apresenta complexidade no que diz respeito ao seu modo de operação. A fim de reduzir os problemas relacionados ao forte acoplamento existente nesses processos, a busca pela incorporação de dispositivos de inteligência artificial vem apresentando uma tendência crescente nos últimos anos. Devido à complexidade de operação e controle em processos multivariáveis, o diagnóstico e monitoramento de falhas nos processos tornaram-se cada vez mais difícil, com isso a aplicação destes dispositivos tem alcançado resultados satisfatórios em relação aos procedimentos executados com operadores humanos. A análise de componentes independentes (ICA) é uma técnica de separação de sinais que se baseia no uso de estatísticas de ordem superior para estimar cada uma das fontes desconhecidas por meio da observação de diversas misturas geradas a partir destas fontes. Embora sejam encontrados trabalhos recentes sobre a utilização do ICA em processos industriais, apenas dois trabalhos até o presente momento, foram aplicados em processos envolvendo colunas de destilação. O presente trabalho tem como objetivo propor uma estratégia de controle a uma coluna de destilação de alta pureza. A estratégia é baseada na técnica de separação de sinais ICA, tornando as malhas de controle desacopladas e facilitando assim o desempenho do controle. O desempenho do sistema de controle utilizando a técnica apresentou excelentes resultados em relação a uma estrutura convencional sem desacoplamento. As estruturas de controle foram implementadas em ambiente Aspen Plus DynamicsTM e Simulink/ Matlab®. O processo foi estruturado em ambiente Aspen Plus Dynamics™ e os controladores foram implementados no Simulink.
Much of the industry presents complexity with regard to its mode of operation. In order to reduce the problems related to existing strong engagement in these processes, the search for the incorporation of artificial intelligence devices has shown an increasing trend in recent years. Due to the complexity of operation and control in multivariate processes, the diagnosis and fault monitoring in the processes have become increasingly difficult, thus the application of these devices has achieved satisfactory results in relation to procedures performed with human operators. The independent component analysis (ICA) is a signal separation technique that is based on the use of higher order statistics to estimate each of the unknown source by observing various mixtures generated from these sources. Although found recent work on the use of the ICA in industrial processes, only two studies to date, have been applied in cases involving distillation columns. This paper aims to propose a control strategy to a high purity distillation column. The strategy is based on the ICA signal separation technique, making decoupled control loops, thus facilitating control performance. The performance of the control system using the technique showed excellent results compared to a conventional structure without decoupling. The control structures have been implemented in Aspen Plus Dynamics™ and Simulink / Matlab® environment. The process was structured environment Aspen Plus Dynamics™ and the controls were implemented in Simulink.

Recent publications on ethanol production and purification shows optimized energy and water consumptions as low as 22,000 Btu/gal ethanol and 1.54 gal water/gal ethanol respectively using multieffect distillation. Karuppiah, et al use column rating and mathematical optimization methods and shortcut design models to design evaluate and optimize the energy and water consumption. In this work, we compare shortcut design and rigorous simulation models for an ethanol purification distillation system, and we show that distillation systems based on shortcut design underestimate the true energy and water consumption of the distillation system. We then use ASPEN Plus, to design a multieffect distillation system and an extractive distillation system using rigorous simulation and compare the two for energy and water consumptions. We show that the extractive distillation system has lower steam and cooling water consumptions and consequently lower energy and water consumptions than multieffect distillation in corn-to-ethanol production and purification. We also show that the extractive distillation system is cheaper than the multieffect distillation system on a cost per gal ethanol basis. This work gives an energy consumption of 29987 Btu/gal ethanol and water consumptions 2.82 gal/gal ethanol for the multieffect distillation system at a manufacturing cost of $3.03/gal ethanol. For the extractive distillation system, we calculate an energy consumption of 28199 Btu/gal ethanol and a water consumption of 2.79 gal/gal ethanol at a manufacturing cost of $2.88/gal ethanol.
Master of Science

Cryogenic carbon capture process can be used to efficiently eliminate CO2 emissions from fossil-fueled power plants. The energy-storing embodiment of cryogenic carbon capture (ES-CCC) integrates energy storage with cryogenic carbon capture and uses natural gas as a refrigerant. ES-CCC captures CO2 from slowly varying or steady-state sources even as it absorbs and replaces large amounts of energy on the grid for energy storage. These large transients occur in the LNG generation as the process moves through energy storing to energy recovery operations. Additionally, raw natural gas often includes CO2 that forms an azeotrope with ethane. Breaking this azeotrope and separating CO2 from other hydrocarbons to meet natural gas pipeline and liquefied natural gas (LNG) standards is very energy intensive. The purpose of this work is to (a) describe a dynamic heat exchanger that reduces the heat exchanger performance and efficiency losses experienced under transient conditions and (b) introduce an alternative extractive distillation system for CO2 separation from ethane that requires less capital and has a lower operating cost than the conventional system for the same purification. This investigation demonstrates theoretically and experimentally that the dynamic heat exchangers can absorb sudden and large changes in flow rates and other properties without compromising either the heat exchanger efficiency or creating thermal or other stresses. These heat exchangers play an essential role in the ES-CCC process. Designs for retrofitting existing heat exchangers and for replacing existing heat exchangers with new designs are both theoretically and experimentally tested. The ES-CCC process requires natural gas processing to meet pipeline and LNG standards in many applications, depending primarily on the CO2 content of locally available NG. The energy, cost, and dynamic response of such processing hinges primarily on the most difficult step, breaking the CO2-ethane azeotrope. This project proposes and analyzes an alternative process for breaking this azeotrope and a control scheme that dramatically improves the dynamic response of natural gas processing plants, including steady and transient control scheme and processing simulations. These contributions to the ES-CCC capture process all have much broader applications in many chemical and energy processes. These contributions to ES-CCC and other industrial processes improve energy efficiency and dynamic performance of many processes and are ready for larger scale demonstration.

Orientador : Maria Regina Wolf Maciel
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: A destilação é, certamente, o processo mais aplicado na separação de misturas líquidas. Embora esta seja uma operação unitária conhecida de longa data, ainda, nos dias de hoje persistem algumas dificuldades na proposição de esquemas de destilação apropriados. Sendo assim, o objetivo deste trabalho de tese foi aplicar modelos mais realistas na caracterização de misturas e na simulação de processos de destilação, em regimes estacionários e dinâmicos. Para tanto, foram avaliados dois softawes, desenvolvidos no Laboratório de Desenvolvimentos de Processos de Separação, para simulações de colunas de destilação considerando os modelos de estágios de equilíbrio e de não equilíbrio. Os resultados obtidos mostraram que, geralmente, os perfis obtidos com as duas modelagens são diferentes, em ambos os regimes. A modelagem de estágios de não equilíbrio foi aplicada também para a caracterização de sistemas, utilizando mapas de curvas residuais. Avaliou-se, ainda, a influência das correlações de eficiência de Barros & Wolf em mapas de curvas residuais. Os perfis obtidos com as correlações de eficiência de Barros & Wolf mostram grande concordância com os calculados pelo modelo de estágios de não equilíbrio. Com os mapas de curvas residuais calculados concluiu-se que as trajetórias líquidas de composição não cruzam as fronteiras de destilação, sendo esta um questão de polêmica na atualidade, no entanto, nossos resultados mostram os perfis corretos. Além disso, desenvolveu-se, neste trabalho de tese, um programa computacional para a caracterização de sistemas reativos. A vantagem do novo algoritmo proposto está, principalmente, no fato do programa não depender de estimativas inicias e ser de fácil convergência. O programa é, também, capaz de predizer todos os azeótropos presentes na mistura, quando existam um ou mais de um, ou ainda de afirmar que a mistura é zeotrópica. Os resultados obtidos são concordantes com valores experimentais ou calculados por outros métodos. Na linha do processo de destilação reativa, sendo este um processo inovador, foi proposta a separação da mistura fenol + água. A separação desta mistura é de grande interesse, por questões econômicas e ambientais. Preliminarmente, fez-se um estudo na busca de uma reação apropriada para o consumo de fenol. O processo proposto atende completamente às questões ambientais, visto que gera somente correntes limpas e é, portanto, uma nova alternativa para o tratamento de correntes fenólicas. Por fim, desenvolveu-se neste trabalho um conjunto completo para caracterização de sistemas e simulação de processos, envolvendo desde o modelo de estágios de equilíbrio até o modelo de estágios de não equilíbrio. Propôs-se, ainda, um eficiente processo para o tratamento de águas fenólicas
Abstract: Distillation is, certainly, the most applied process in the separation of liquid mixtures. Although this is a very known unit operation, still nowadays some difficulties persist in the proposal of appropriate distillation schemes. Thus, the objective of this work was to apply more realistic models in the characterization of mixtures and in the simulation of distillation process in, both, steady state and dynamic regime. In this way, two softwares developed in the Laboratory of Separation Processes Development were evaluated. These softwares consider the equilibrium and the nonequilibrium stage models in steady state and dynamic regime. The results show that, generally, the profiles obtained with the two models are different, in both regimes. The nonequilibrium stage model was also applied for the systems characterization, in residue curve maps. It was evaluated, still, the influence of Barros & Wolf correlations for efficiencies on residue curve maps. The profiles obtained with the Barros & Wolf correlations show good agreement with the calculated with the nonequilibrium stage model. The calculated residue curve maps showed that residue curves do not cross distillation boundaries. Nowadays, this is a question of controversy, however our results show the correct behavior. Moreover, it was developed in this work a computational program for the characterization of reactive systems. The advantage of the new proposed algorithm is mainly because the program does not depend on initial estimates and it is of easy convergence. The program is, also, able to predict all the azeotropes present in the mixture, when one or more than one exist, or still to affirm that the mixture is zeotropic. The obtained results are in agreement with experimental values or values calculated by other methods. Regarding to reactive distillation, being an innovative process, it was proposed the separation of the mixture phenol + water. The separation of this mixture is of great interest, for economic and environmental issues. Preliminarily, it was carried out a study of an appropriate reaction for the phenol consumption. The considered process takes care of environmental questions, since it only generates current clean and it is, therefore, an alternative process for the phenolic wastewater treatment. Finally, in this work, it was developed a complete set for characterization of systems and simulation of processes, involving the equilibrium and the nonequilibrium stage modes, in steady state and dynamic regime. It was considered, still, an efficient process for the phenolic wastewater treatment
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química

Orientadores: Rubens Maciel Filho, Maria Regina Wolf Maciel
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: No Brasil, o bioetanol é usado para substituir a gasolina, compondo uma porcentagem desta ou sendo usado como combustível alternativo. Esta tendência de substituição dos combustíveis fósseis vem se fortalecendo em âmbito global, sendo necessárias, portanto, alternativas e propostas que viabilizem o aumento da produção de forma economicamente e ambientalmente sustentável. Neste contexto, a otimização energética do processo de separação do bioetanol visa à disponibilização de bagaço de cana-de-açúcar, usado como combustível na geração de vapor de processo, para a produção de bioetanol através do processo de hidrólise. Para tanto, inovações ao processo são essenciais e melhoramento na representação de modelos torna-se necessário para estudos e avaliações. Neste trabalho, simulações da etapa de destilação para a produção de álcool hidratado assim como da etapa de desidratação do bioetanol foram realizadas utilizando o simulador Aspen Plus®. Visando um estudo dentro de um cenário mais realista, a modelagem de estágios de não equilíbrio foi utilizada para prever o comportamento das colunas de destilação envolvidas. Além disso, o uso da correlação de Barros e Wolf para a determinação de eficiência na modelagem de estágios de equilíbrio em colunas de destilação foi avaliado. A comparação entre as modelagens de estágios de equilíbrio e não equilíbrio para as destilações convencional e extrativa indicou que a associação da correlação de eficiência de Barros e Wolf à modelagem de estágios de equilíbrio fornece predições satisfatórias tendo como referência a modelagem de estágios de não-equilíbrio. Para a destilação azeotrópica, o estudo de formação de duas fases líquidas na coluna foi realizado, indicando que os parâmetros de processo, como posição de alimentação, possuem influência significativa. O estudo da fermentação extrativa a vácuo, como configuração alternativa às etapas de fermentação e concentração, revelou seu potencial para redução do consumo de energia na etapa de destilação subseqüente, sendo uma alternativa viável para intensificação de processos
Abstract: In Brazil, bioethanol is used to replace gasoline, being a percentage of this or used as an alternative fuel. This trend of replacing fossil fuels has gained strength globally, necessitating, therefore, alternatives and proposals to enable the increase of production in an economically and environmentally sustainable way. In this context, the energy optimization of the bioethanol separation aims the provision of sugarcane bagasse, used as fuel in process steam generation, for bioethanol production through the hydrolysis process. Consequently, innovations to the process are essential and improvement in the representation of models is required for studies and evaluations. In this work, simulations of the distillation step for the production of hydrous bioethanol and the bioethanol dehydration were performed using the simulator Aspen Plus®. In order to study a more realistic scenario, nonequilibrium stage model was used to predict the behavior of the involved distillation columns. Furthermore, the use of Barros and Wolf correlation for the determination of efficiency in equilibrium stage model for distillation columns was evaluated. The comparison between equilibrium and nonequilibrium stage models for conventional and extractive distillation processes indicated that the association between Barros and Wolf efficiency correlation and equilibrium stage model provides satisfactory predictions considering the nonequilibrium stage model as reference. For azeotropic distillation, formation of two liquid phases inside the column was studied, indicating that process parameters, such as feed position, have significant influence. The study of vacuum extractive fermentation, as an alternative configuration to fermentation and concentration steps, showed its potential for reducing energy consumption in the subsequent distillation step, and it seems a viable alternative to process intensification
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química

Orientadores: Maria Regina Wolf Maciel, Antonio Andre Chivanga Barros
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Devido à sua abrangência com os fenômenos de transferência de massa, calor e quantidade de movimento, capacidade e características operacionais, relações termodinâmicas e o amplo envolvimento com outros equipamentos industriais, o estudo dos processos de separação por destilação toma-se muito complexo, apesar de sua extensiva utilização nas indústrias químicas e petroquímicas. Por isto, trabalhos de grande relevância científica são ainda desenvolvidos para melhor entender os fenômenos relacionados e que permitem melhorar a sua operacionalidade. Assim, este trabalho teve como objetivo a avaliação experimental de uma coluna de destilação com pratos perfurados, permitindo averiguar o comportamento das eficiências de Murphree, O'Connell e da correlação de Barros & Wolf, além da avaliação dos perfis dos coeficientes de transferência de massa e calor ao longo do equipamento. Os dados experimentais obtidos foram utilizados para a validação dos modelos de estágios de equilíbrio e de não equilíbrio e da correlação de eficiência desenvolvida por Barros & Wolf. Para a realização deste trabalho, uma coluna de destilação, em aço inoxidável, contendo 8 pratos perfurados com vertedor e um sistema para controle da potência foram projetados e construídos. A coluna contém 8 pontos para a coleta de amostras de líquido e termopares acoplados em cada prato para a leitura de temperatura. Para cada experimento foram variadas as composições do etanol na alimentação e a potência fomecida ao refervedor para avaliar a influência da carga térmica sobre o comportamento das frações molares e da temperatura em uma coluna operada a refluxo total. Nos ensaios, trabalhou-se com o sistema etanolágua por ser de fácil determinação analítica e por existirem dados de equilíbrio precisos e alguns valores de eficiência. Após o alcance do estado estacionário, determinado a partir de leituras periódicas de temperatura ao longo do equipamento, foram feitas coletas de amostras de líquido em cada estágio da coluna, as quais foram analisadas empregando a técnica de cromatografia à gás. Com os dados da temperatura, composição do etanol e da água em cada estágio e da potência fomecida ao refervedor, foram calculadas as eficiências de Murphree e de O'Connell. Com a utilização de programas computacionais envolvendo a modelagem de estágios de equilíbrio (com a correlação de Barros & Wolf) e de não equilíbrio, desenvolvidos no Laboratório de Desenvolvimento de Processos de Separação da UNICAMP, foram realizadas simulações nas condições de operação dos experimentos, cujos dados obtidos foram utilizados para comparação com dados experimentais de forma a corroborar tais modelos. Os resultados obtidos mostraram que as modelagens de estágios de equil íbrio e de não equilíbrio reproduzem, com grande fidelidade, as condições reais do processo e representam o comportamento real dos coeficientes de transferência de massa e calor ao longo da coluna de destilação. Os resultados obtidos mostraram-se compatíveis com os dados da literatura
Abstract: Due to the relation with the mass, heat and momentum transfer phenomena, capacity and operational characteristics, thermodynamic properties and the wide relationship with other industrial equipment, the study of the separation processes by distillation becomes very complex, in spite of its extensive use in the chemical and petrochemical industries. For this reason, researches of great scientific relevance are still being developed for better understanding the related phenomena and for allowing the improvement of the operation. Thus, this work presents as objective the experimental study of a distillation column with sieve plates to evaluate the behaviour of the Murphree efficiency, Q'Connell and Barros & Wolf correlations and the mass and heat transfer coefficients along the equipment. The experimental data were obtained used for the validation of the equilibrium and nonequilibrium stage models and of the new efficiency correlation developed by Barros & Wolf. For these purposes, a stainless steel distillation column with eight sieve plates with down comer and a system for the power measuring were designed and built. The column contains eight spaced temperature/sample points. For each experiment, the ethanol feed composition and the heat duty were changed to evaluate the influence of the heat duty on the behaviour of the mole fractions and on the temperature profiles in the column operating at total reflux. After established the steady state, the liquid samples and the temperature were taken in each stage of the column, and the samples were analyzed using the gas chromatography technique. Using the temperature and ethanol and water compositions in each stage and the heat duty supplied to the reboiler, Murphree and Q'Connell efficiency were calculated. The programs involving the equilibrium stage model (with Barros & Wolf correlation) and the nonequilibrium stage model developed in the Laboratory of Separation Process Development (UNICAMP) were used in the simulations at the same conditions of the experiments. The data obtained with simulations were compared with experimental data to corroborate such models. The obtained results showed that the equilibrium stage model and the nonequilibrium stage model reproduce, with great fidelity, the real conditions of the process and they can be used to represent the real behaviour of the mass and heat transfer coefficients along the distillation column
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química

We examine the simplest homogeneous azeotropic distillation sequence of industrial relevance, where we add an entrainer to a binary azeotrope in order to recover both azeotropic constituents as pure products. Despite its apparent simplicity, such distillation columns can exhibit an unusual behavior not observed in zeotropic distillation:
- For some mixtures, separation as a function of reflux goes through a maximum. At infinite reflux, no separation is achieved.
- In some cases, achieving the same specifications with a larger number of trays requires a larger reflux.
- In some cases the only feasible separation yields the intermediate component as a pure distillate while the bottom product contains the light and heavy components.
- In some cases the only feasible separation yields the intermediate component as a pure bottom product while the distillate contains the light and Hay components.

While these unusual features can be regarded as curiosities, they are essential for proper entrainer selection and design. When designing a homogeneous azeotropic sequence which separates a binary azeotrope into two pure products, we must first choose the entrainer. Currently available entrainer selection criteria, are inadequate: They contradict one another and often lead to incorrect conclusions. Indeed, for a minimum boiling azeotrope, the existing entrainer selection rules state that, one should use a high boiling component that introduces no additional azeotrope (Benedict & Rubin 1945), an intermediate boiling component that introduces no additional azeotrope (Hoffman 1964), a component which introduces no distillation boundary between the azeotropic constituents (Doherty & Caldarola 1985), and either a low boiling component that introduces no additional azeotrope or a component that introduces new minimum boiling azeotropes (Stichlmair, Fair & Bravo 1989). By taking advantage of the curious aforementioned features, we have been able to understand when these criteria, are correct, or incorrect.

In the case of homogeneous azeotropic distillation, separability at finite reflex and at infinite reflux are not equivalent and must be examined separately. By analyzing in detail the profiles of columns operated at infinite reflux, we have:
- shown that a binary azeotrope can be separated with only one distillation column. We present a necessary and sufficient condition that identifies such situations;
- found a necessary and sufficient condition for separability in a two-column sequence. When separation is feasible, this condition indicates the flowsheet of the corresponding separation sequence;
- shown that separation is very often feasible in a three-column separation if the two azeotropic constituents are located in adjacent distillation regions.

Then, we examine two situations where separation is feasible at finite reflux but not at infinite reflex.

Finally, we present practical solutions (in the case of entrainers that add no azeotropes to two problems of industrial relevance: Given a binary azeotrope that we want to separate into pure components, and a set of candidate entrainers, how do we determine which one is the best? Also, for each of these entrainers, what is the flowsheet of the feasible separation sequence(s)? We obtain these solutions by analyzing in detail the mechanisms by which heavy, intermediate and light entrainers make separation feasible, using the new notions of equivolatility curves, of isovolatility curves and of local volatility order. We show that the second question finds an easy solution from the volatility order diagram.

This analysis shows that a good entrainer is a component that "breaks" the azeotrope easily (i.e., even when its concentration is small) and yields high relative volatilities between the two azeotropic consituents. Because these attributes can be easily identified in an entrainer from the equivolatility curve diagram of the ternary mixture azeotropic component #1 - azeotropic component #2 - entrainer, we can easily compare entrainers by examining the corresponding equivolatility curve diagrams. We also demonstrate the validity and limits of this method with numerous examples.

博士
國立臺灣科技大學
化學工程系
91
A liquid-liquid equilibrium (LLE) apparatus was used in the present study to measure the LLE data of aqueous solutions containing ethanol or 2-propanol with different entrainers, including 1-butanol, butyl propionate, ethyl caporate, ethyl acetate and isopropyl acetate, at temperatures from 283.15 K to 323.15 K. A static-type apparatus equipped with a visual cell was also utilized to measure vapor-liquid equilibrium (VLE) and vapor-liquid-liquid equilibrium (VLLE) data for the binary and ternary mixtures of water/ethanol/ethyl benzoate, water/2-propanol/ethyl acetate and water/2-propanol/isopropyl acetate at temperatures from 308.15 K to 373.15 K. The experimental results showed that a maximum pressure azeotrope exhibited on each isotherm of ethyl acetate + 2-propanol and isopropyl acetate + 2-propanol. The NRTL and UNIQUAC models were selected to represent the phase behavior for the investigated systems. Those model parameters determined from the binary LLE data were found to be linearly dependent on temperature. With an ideal gas-phase assumption the solution theory models represent satisfactorily the VLLE properties for the binary VLLE systems. It was also found that using the parameters determined from the binary VLE, LLE or VLLE data couldn’t predict accurately the VLLE properties of the ternary systems. The representation for the VLLE behavior was improved, while the six parameters of the NRTL and the UNIQUAC models were determined, simultaneously, from the isothermal VLLE ternary data. These experimental data were also used to test the validity of various versions of the UNIFAC model. The calculated results showed that the UNIFAC-Lyngby predicted the binary VLE properties well, but the UNIFAC-LLE represented just qualitatively the phase behavior for the binary and ternary VLLE systems. The Soave-Redlich-Kwong equation (SRK), a cubic equation of state, was utilized to calculate VLE and VLLE properties by using three types of a function that accounts for the temperature dependence of the energy parameter ( ) in the attractive term. The selected mixing rules in this study are the van der Waals (vdW) one-fluid mixing rule and Chung-Twu (GE) mixing rule. The calculated results showed that the SRK-T/CT-UNIFAC-Lyngby, in general, not only predicted accurately the binary VLE properties, but also represented the ternary VLLE phase behavior reasonably well. The vapor pressure data of the pure components were the only required property for this method. Moreover, the SRK-T/CT-UNIFAC-LLE yielded better prediction for the type 2 LLE systems.

碩士
東海大學
化學工程學系
89
Dual composition control for a single heterogeneous column which using the reflux ratio and reboiler heat duty as manipulated variables to maintain both the top and bottom composition is applied in most distillation columns. Normally, it is not easy to maintain the product purity in the heterogeneous azetropic distillation column, since the controlled variables were not linear with manipulated variables. The objective of this study is to build up a simple control scheme, which will be able to ensure precise composition control for ternary heterogeneous azeotropic distillation systems. A new control scheme named “two columns control”, which considered the whole plant including heterogeneous azeotropic column, recovery column and the responding recovery streams was proposed in this stuey. It recommended using the heat duty of each column (i.e., azeotropic and recovery column) to control its bottom product. In addition, a modular dynamic simulation model based on Franks (1972) structure for an azeotropic distillation system separating iso-propanol and water with cyclohexane as entrainer was developed. It was found from the dynamic simulation the product purity in the single column is reduced when disturbance occurred, since manipulated variables are interacted each other. On the other hand, the proposed two columns control strategy can perform a precise dual composition control for the heterogeneous azeotropic distillation system.

碩士
東海大學
化學工程學系
88
The objective of this study is to build up a simple control scheme that will be able to ensure precise composition control for ternary heterogeneous azeotropic distillation systems. A modular dynamic simulation model based on Franks (1972) structure for an azeotropic distillation system separating ethanol and water using benzene as the entrainer was developed. Then, dual-composition control for a single heterogeneous column using the reflux ratio and the reboiler duty as manipulated variables to maintain the top and the bottom compositions was investigated. It was found that the pairing of manipulated and controlled variables for the single column could not be consistent from the studies of relative gain array (RGA) and Niederlinski index (NI). Dynamic simulation also shows that the precise dual-composition control for a single azeotropic column was not easy, even though the temperature for each stage of the column could be perfectly controlled. On the other hand, a new control scheme was proposed, which considered the heterogeneous column, the connected recovery column, and the corresponding recycle stream as a whole plant, and named as the two-column control in this study. The proposed two-column control strategy recommended using the heat duty of each column (i.e., azeotropic and recovery columns) to control its bottom product. Dynamic tests with RGA and NI analyses have demonstrated that the proposed two-column control strategy can perform a precise dual-composition control for the ternary heterogeneous azeotropic distillation system.

碩士
國立成功大學
化學工程學系碩博士班
91
By addressing both flowsheeting and scheduling issues, an integrated design method for the batch azeotropic distillation systems has been developed in this work. The design method can be applied in two stages. First, the optimal flowsheet (state-task network, STN) is synthesized with an integer program (IP). A mixed integer linear programming (MILP) model is then constructed accordingly for generating the optimal schedule. The implementation procedure of the proposed design approach is demonstrated with a series of case studies in this thesis. From the numerical results obtained in various examples, it can be clearly observed that the performance of a batch azeotropic distillation process can be greatly affected by the STN structure. Consequently, the importance of the proposed integrated design approach can be confirmed indirectly.

碩士
東海大學
化學工程學系研究所
86
A modular approach based on the rigorous dynamic model for heterogeneous azeotropic distillation columns has been developed in this study. An ethanol dehydration system using benzene as entrainer is also explored on the basis of these modules. The dynamic behavior of the heterogeneous azeotropic column is tested by the disturbances of feed flow rate, feed composition,and reflux fraction of aqueous phase in decanter. Also, simulation of the controlled distillation column using classic PI control and PI with feedforward control is studied. Simulation results have demonstrated that the developed modules are workable and they can be reliably used in the further advanced control studies of heterogeneous azeotropic distillation columns.

碩士
東海大學
化學工程與材料工程學系
101
Due to shortage of energy resources and fluctuating oil prices in recent years, the development of energy-saving processes has become an important issue. In view of energy-efficient features of newly developed dividing-wall columns (DWC), this study looks into the design of a reactive distillation system and a heterogeneous azeotropic system by incorporating DWCs using ChemCad. The first system involves the esterification of mixed acids (acetic acid and propionic acid) with methanol to yield methyl acetate, methyl propionate, and water. Simulation and optimal design are carried out for conventional reactive distillation sequence as well as for reactive dividing-wall distillation system. Results show that the reactive dividing-wall system saves steam consumption by about 45.2%, compared with that of the conventional reactive distillation sequence. The reactive dividing-wall column reduces total annual costs (TAC) by 34-37%, when compared with that of its counterpart. The second case studied is a heterogeneous azeotropic distillation system, involving dehydration of crude isopropyl alcohol. Cyclohexane is used as an entrainer for the system. Two optimal separation systems are generated, including one with a single dividing wall column and one with a double dividing wall column. In comparison with an azeotropic distillation sequence containing two stripping columns, reported in the literature (Chang et al., 2012), simulation results show that the former two systems can cut steam usage further by 6.0%. The two systems save about 6-10% in terms of TAC. The use of DWCs has been demonstrated in the case studies, and DWCs prove to be superior to the convention distillation system, with respect to costs and energy efficiency.

碩士
國立臺灣科技大學
化學工程系
95
The common practice in the studies of batch distillation is through simulation of such process. However, simulation results might not match experimental results. To this aim, this work proposed a correction factor between simulation results and experimental results. By comparing the difference between simulation and experimental results, revision is made to the mathematical model based on correction principles to achieve a closer match of the results. In addition, parametric analysis is carried out by comparisons of simulation results with experimental results for various parameters. This verification process greatly increased the acceptability of the revised mathematical model.

碩士
國立臺灣科技大學
化學工程系
98
The design and control of three dehydration process system via azeotropic distillation will be investigated in this thesis. In azeotropic distillation system that commonly divide into three parts, heterogeneous azeotropic distillation, homogeneous azeotropic distillation and pressure swing distillation. First in the heterogeneous azeotropic distillation system considers a flowsheet for the separation of the 1,4 - Dioxane/water azeotropes that comparing Ethyl acetate and Benzene as entrainer. Also use pressure swing distillation system to separate this azeotropes. Second system is using heterogeneous azeotropic distillation system to separate Methyl methacrylate (MMA)/methanol/water. Design with two columns and a decanter or design with a single column with side flow and a decanter are used. The final system is to study a homogeneous azeotropic distillation column system for the separation of Propylene Glycol Monomethyl Ether (PM) and water using Sulfolane as entrainer. The proposed flowsheet should be a two-column system which contains a extractive distillation column and a entrainer recovery distillation column. The optimal design flowsheet has been established for the above three system by minimizing Total Annual Cost (TAC) of the design flowsheet. A very simple overall control strategy has also been proposed for the above systems which requires only one tray temperature control loop in each column to hold the high-purity specifications of the products.

碩士
國立臺灣大學
化學工程學研究所
92
In this research, we discuss the influence of feed impurities m-xylene and methyl acetate on the operation for dehydration of acetic acid by heterogeneous azeotropic distillation. A concept is presented for the design of side-draw to prevent the accumulation of m-xylene composition in distillation column from long-term operation. The theoretical research illustrates steady-state and dynamic simulations of an industrial column. Optimal TAC estimation decides the best side-draw stage, flow rate and feasible make-up flowrate of entrainer, iso-butyl acetate, into the column. As the flowrate of side-draw is too low it will be not easy to operate smoothly in experiential application. We purge higher side-draw flowrate to make the process more practicable in dynamic simulation. According to the result of simulation we can decide the better purge time and flowrate of side-draw stream. In particular, we find the m-xylene from feed line could be a better entrainer for the industrial separation of acetic acid-water system. It can improve the process to have more economic benefits.

An automated procedure to synthesize, design, and optimize homogeneous, azeotropic distillation sequences is presented. The procedure allows for the rapid screening of feasible separation trains and comparison of process alternatives. The synthesis step has been automated using techniques from differential topology and graph theory. The only physical property data needed to determine the physically permissible separation(s) for a given feed are the boiling point temperatures of all pure components and azeotropes. The procedure is well suited to screening candidate entrainers for separating binary azeotropic mixtures as well as determining viable sequences for many-component azeotropic mixtures. Once the distillation train has been synthesized, each column must be designed to meet the target product compositions. An algorithm for calculating the minimum reflux ratio for ideal, nonideal, and azeotropic distillation columns with significant heat effects is presented. The algorithm applies to single- and multiple-feed columns. An algorithm for determining the number of theoretical trays required for the column at operating conditions is also presented. The column sequences are optimized to ensure that comparisons among alternative entrainers and/or sequences are done on an equitable basis. The most significant optimization variable in the separation of binary azeotropic mixtures is the feed ratio, the dimensionless entrainer recycle flow rate. Sequences properly designed and optimized are found to be significantly cheaper than those previously reported in the literature.

碩士
國立臺灣科技大學
化學工程系
97
The design and control of three dehydration process system via heterogeneous azeotropic distillation will be investigated in this thesis. First system considers a flowsheet for the separation of the IC5/methanol azeotropes that takes advantage of the heterogeneity of the azeotrope. Two stripping columns and a decanter are used. Second system is to study a heterogeneous azeotropic distillation column system for the separation of Propylene Glycol Monomethyl Ether (PM) and water using Isopropyl acetate (IPOAC) as entrainer. The proposed flowsheet should be a two-column system which contains a pre-concentrator and a heterogeneous azeotropic distillation column. The last system is dehydration of Pyridine using toluene as entrainer. The optimum steady-state design is a two-column system which combines per-concentrator column and recovery column into a single system. The optimal design flowsheet has been established for the above three system by minimizing Total Annual Cost (TAC) of the design flowsheet. A very simple overall control strategy has also been proposed for the above systems which requires only one tray temperature control loop in each column to hold the high-purity specifications of the two products.

碩士
東海大學
化學工程學系
87
A rigorous dynamic model for heterogeneous azeotropic distillation columns based on the modular approach has been developed in this study. Dynamic behavior for a heterogeneous azeotropic distillation column with various of controllers can be linked together using these modules. Both ethanol dehydration and SBA (secondary butyl alcohol) dehydration processes including steady-state study have been explored on basis of these modules. It was also found that the calculations of VLE/VLLE using rigorous thermodynamic algorithm is often the bottleneck of executing speed during computer simulation for a heterogeneous azeotropic distillation. Thus, techniques using artificial neural networks (ANN) to learn the phase equilibrium relationships instead of using rigorous thermodynamic algorithm has been proposed in this study. The results show that both steady-state and dynamic simulation using ANN approximate models can consist with the rigorous algorithm. Besides, the computation speed has drastically improved. Furthermore, controllability studies based on the relative gain array (RGA) criteria for the dehydration of acetic acid using n-butyl acetate as entrainer has also been investigated. It was found that the control pairing for double-composition control is highly depended upon both operation conditions and disturbances, and there are two kinds of steady-state modes in the system, i.e., water-rich mode and entrainer-rich mode. These will cause difficulty in the control of a heterogeneous azeotropic distillation column. Similar phenomena were also found in the ethanol dehydration process in this study.

碩士
國立宜蘭大學
化學工程與材料工程學系碩士班
97
The separation of azeotropic mixtures is a common task in the chemical industry. The pressure swing distillation(PSD) is an effective separation of binary azeotropic mixtures, and it has the advantages of simplicity, low energy and low cost. In this study we focused on two parts, the first part is to determine the azeotropic compositions and temperatures by use of the Wilson equation. The second part is to explore the applicability of PSD and locate the best operating conditions. The study shows various compositions corresponding to the pressure 1atm、2atm、3atm、5atm and 10atm, respectively. Then we group them to pressure sensitivity and pressure non-sensitivity azeotropic mixtures system. Only the pressure sensitive azeotropic mixtures can be used in the PSD economically. Also, we investigate the effectiveness of recycle flow rate . Totally we examined 18 systems of binary azeotropic mixtures. Among them, we found that 13 systems (72.22%) were suitable for operation of PSD . The results of this study provided us with useful information for further study in applicability of pressure swing distillation. Among them, we found that 13 systems were suitable for operation of PSD . The results of this study provided us with useful information for further study in applicability of pressure swing distillation.

碩士
國立成功大學
化學工程學系碩博士班
96
By addressing both flow sheet generation and scheduling issues, a sequential design method has been developed in this work for the batch azeotropic distillation systems. The proposed strategies can be applied in two stages. Firstly, an Integer Programming (IP) is solved to produce the optimal flow sheet (or state-task network). A Mixed Integer Linear Programming Model (MILP) is then constructed accordingly for generating the optimal short-term schedule. On the other hand, a Mixed Integer Non-Linear Programming (MINLP) is also constructed for generating optimal cyclic schedule. The concept of event points is adopted to facilitate the continuous-time representation in this formulation. The implementation procedure is demonstrated with several case studies. Satisfactory process configurations and production schedules can both be produced in all the cases we have studied so far.

While it has been known for about 130 years that azeotropes are influenced by changing pressure, this fact has never been fully exploited. In this dissertation it is shown how pressure effects can be used to advantage or can foil attempts to distill homogeneous azeotropic mixtures and how an analysis of the fixed points of the distillation model leads to new important insights into extractive distillations. As the pressure varies, not only the composition but also the number of azeotropes can change. A change in the number of azeotropes corresponds to a transcritical bifurcation. A bifurcation-theoretic treatment provides a model-independent method for locating global changes in the residue-curve map of a mixture as the pressure changes and for predicting the presence of severe tangent pinches. Existing methods for synthesizing thermally-integrated distillation sequences frequently fail when applied to nonideal and azeotropic systems because changing column pressures often introduces new azeotropes and distillation boundaries into the mixture, which make some separation tasks infeasible. A new, systematic thermal-integration procedure is presented that combines a bifurcation and residue-curve map analysis with the method of Andrecovich and Westerberg and results in substantial energy savings. A new pressure-swing distillation process is presented that makes it possible to separate mixtures in which the desired products lie in different distillation regions when one end of the distillation boundary is a pressure-sensitive azeotrope. Thus pressure-insensitive binary azeotropes can be separated using novel entrainers that form pressure-sensitive distillation boundaries. In addition to a minimum reflux, every extractive distillation also exhibits a maximum reflux, above which the desired separation is impossible, and a minimum entrainer flow rate, below which the separation is also impossible. Both of these quantities are shown to correspond to bifurcations of the finite-difference equations describing the middle section of the column and, given a VLE model, both can be easily calculated knowing only information about the column feed and the desired product compositions--i.e., prior to any column design calculations. Both the minimum entrainer flow and the maximum reflux ratio have important implications for extractive distillations. A comparison of minimum entrainer flows provides a simple method to discriminate between entrainers with the same feasible residue-curve map. A heuristic is presented for estimating a near optimal design value of the entrainer flow. Maximum reflux results in the separation becoming more difficult at both low and high reflux ratios, requiring nonstandard control action in certain reflux ranges.

碩士
國立臺灣大學
化學工程學研究所
105
Triple column pressure swing distillation (TCPSD) can be a promising method to separate azeotropic ternary mixtures. In order to adopt this configuration, a pre-requisite is that the distillation boundaries move apparently under different operating pressures, and this can be checked through the residue curve map (RCM). In this thesis, a rigorous and extensive study on TCPSD is performed, with several separation system containing different amount of azeotropes as demonstration. All of the simulation work is implemented in Aspen Plus v8.4. The first separation system is the Propanol/acetone/toluene system, which forms an azeotrope. In conventional pressure swing distillation process (CPSD), the lightest component acetone is separated at first column, with propanol and toluene obtained from the flow-up binary pressure swing distillation. For TCPSD, the separation sequence is propanol-toluene-acetone by using the moving distillation boundary based on different operating pressure. The second system studied is the Methanol/ethanol/methyl ethyl ketone (MEK) mixture, which forms two azeotropes, one between methanol-MEK and another between ethanol-MEK. It RCM presents one distillation boundary at atmosphere. For a typical mixture with two azeotropes, it is hard to obtain three product with high purity by TCPSD. However, for this system, methanol-MEK azeotrope pair disappears at high pressure, so TCPSD can be used in this mixture. The third system, Ethanol/ethyl acetate (EtAc)/carbon chloride (CCl4) mixture, forms three azeotropes. By investigating the pressure-sensitive moving boundaries, the complex azeotropic mixture can be separated by TCPSD with a different separation configuration discussed in this research. The fourth system, Methanol/methyl acetate (MeAc)/ hexane system, forms four azeotropes and its triangle diagram shows several distillation boundaries which moves apparently as pressure changes. Throughout the four systems studied in this thesis, sequential iterative method is used to optimize all the flowsheets with minimized TAC as the objective function. Because there are quite a few design and operating variables need to be optimized, some simplification is need to reasonably relieve the tasks. After that, the optimal cases of CPSD and TCPSD are directly compared, in order to get a deeper insight into the feasibilities and advantages when applying TCPSD configuration to different separation systems.

Ethanol-water forms homogeneous minimum boiling azeotrope and it has most common occurrence in many industrial processes. There are various techniques exist to separate azeotropic compositions. In this work we studied the basic features of azeotropic distillation using Aspen plus simulation. Since entrainers are indispensable in separating constant boiling mixtures, in this work, performances of three different entrainers were studied viz. benzene, n-pentane and cyclohexane. The effect of various process variables viz. reflux-ratio and distillate rate on the purity of the final products was studied in detail. RadFrac simulator was used to study the distillation process and NRTL method was used as the base thermodynamic method. It has been found out after simulation that cyclohexane performed best where maximum purity of ethanol (99.91%) was obtained closely followed by n-pentane (99.84%) and benzene (99.77%) as entrainers. The optimum number of stages were 25 (for n-pentane), 45 each for benzene and cyclohexane respectively.

碩士
國立臺灣大學
化學工程學研究所
98
The optimization of complete designs for hybrid membrane-distillation systems is done in this research. The possibility of design improvement by using internal recycle is investigated. Internal recycle in pervaporation only improves the design in some cases. These conditions where internal recycle is beneficial are determined by studying the generalized dimensionless equations. The result is a general framework for understanding internal recycle. Two real systems which are ethanol – water and isopropanol - water system are also investigated. Optimization results without the recycle show the difference in the azeotrope composition causes a difference in the optimum process configuration. The optimal design for ethanol system has a single distillation column followed by a membrane cascade. On other hand, for the isopropyl alcohol system a second distillation column in the configuration gives a better design. The appropriate application of internal recycle further improves the design in both cases. Control structures for these designs are developed to ensure the controllability of the process. The dynamic simulation of the system with internal recycle shows a slower response compared to those without internal recycle.

碩士
國立臺灣科技大學
化學工程系
89
In various chemical processes, often we need to separate acetone and chloroform. This research is to study this important homogeneous azeotropic separation. Two-column and three-column structures will be compared in the thesis. After the steady state simulations of two structures, the optimum process designs and operating conditions will be given respectively. The most economical structure for this separation will be recommended. Proper control strategy of this homogeneous azeotropic separation will also be studied under various feed rate and feed composition changes. Dynamic simulations of various control strategies will be compared.

碩士
國立臺灣科技大學
化學工程系
89
Acetic acid is a very important chemical in industry with wide applications. In various chemical processes, often we need to separate acetic acid and water. This research is to study this important acetic acid dehydration process. Due to tangent pinch characteristics of the process, it is more appropriate to add entrainer and using heterogeneous distillation column for this separation. Seven candidate entrainers will be compared in the thesis and the most economical entrainer for this separation will be recommened. After the entrainer selection, the optimum process design and operating condition will be given. Proper control strategy of this heterogeneous column will also be studied under various feed rate and feed composition changes. Dynamic simulations of various control strategies will be compared.