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1
Halliday, K. "Packed bed reactors." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599875.
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Conventional packed bed reactors of low tube to particle diameter ratio suffer from poor heat transfer near the tube wall, and also from increased axial dispersion compared with wide beds. In this dissertation the potential of a new reactor design aimed at overcoming these deficiencies is investigated. The radially-stratified bed provides more particles in the wall region to support improved heat transfer and also to flatten the voidage profile in an attempt to reduce the axial dispersion. An experimental study on the effect of stratification on voidage profiles using an image analysis technique showed that both the voidage and velocity profiles could be flattened. A study into the effect of different packing arrangements on axial dispersion has shown that the best arrangement for flattening the voidage profile can lead to over-compensation, resulting in channelling through the core and an increase in dispersion. However, a packing arrangement consisting of a binary mixture of large and small particles near the wall with the core of the bed packed solely with the larger, was shown to exhibit dispersion characteristics no worse than monosized packing. This same packing arrangement was also found to support improved heat transfer. At Re<SUB>p ></SUB> 1100 the heat transfer coefficient appropriate to the one-dimensional plug flow model was shown to increase by ca. 15%. A novel analysis of the one-dimensional reactor model has shown that use of a stratified bed of the same voidage, heat transfer coefficient, tube diameter, and feed flowrate as a monosized bed, results in a pressure drop which is 57% of that across a conventional bed of the same bed length. A further advantage of the stratified bed is that, on average, the catalyst particles are nearer the wall than in the conventional monosized bed. The magnitude of this and the other advantages was assessed by simulation of a reaction performed at high Reynolds numbers, the partial oxidation of ethylene. For this purpose, a new, plausible but simple two-dimensional model of the packed bed reactor was devised. A stratified bed was predicted to then have a pressure drop only some 34% of that of a conventional bed for the same overall conversion. This further reduction of some 23% in pressure drop stems largely from the reduction in packed length necessary to achieve a stipulated conversion. Alternatively, for the same selectivity, a stratified bed could reduce the pressure drop to about half that of a conventional bed of the same voidage. The potential of this novel design has thus been demonstrated: the next stage is optimisation.
2
Rao, Ammavajjala V. S. "Structural Characteristics Of Randomly Packed Beds Of Spheres." Thesis, Indian Institute of Science, 1994. https://etd.iisc.ac.in/handle/2005/133.
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Packed beds find extensive application in a wide variety of industries to cany out a large number of diverse processes. The main objective of the present work is to develop models to predict the arrangement of particles and based on them, to determine and evaluate the structural characteristics of packed beds. These problems have received only a limited attention in the literature. As a first attempt, spheres of uniform size are considered.
Beds of aspect ratio up to 2 (referred to as low aspect ratio beds) are analyzed by application of principles of analytical geometry. Expressions are derived for the location of particles and for the structural characteristics of the beds, both of which show periodicity. This leads to the concept of a unit cell which is the repetitive section of the bed whose characteristics are the same as those of the complete bed. The beds fall into three distinct groups — those with aspect ratio between 1 and l√3⁄2, between 1√3⁄2 and 2, and with aspect ratio 2. Equations are distinct for each group. The aspect ratio shows marked influence on the structural characteristics of the beds. Agreement of the predictions on the overall void fraction with the available experimental data is excellent. Radial void fraction profiles are estimated by defining a concentric cylindrical channel (CCC) of an arbitrary thickness and with the cylindrical surface through the radial position of interest located at the middle of the CCC, and by accounting for the solid volumes of all the segments (in this CCC) of spheres with centers lying within a distance of a particle radius on either side of the cylindrical surface. The curved boundaries of the sphere segments are rigorously accounted for. The results show that the entire bed is filled with variations in the void fraction, starting from a value of unity at the wall and zero (or close to zero) towards the axis of the bed.
Monte Carlo model for the simulation of high aspect ratio beds has not proved successful even with any of a wide variety of distribution functions for the coordinates of the sphere dropping point. With uniform distribution, the only distribution used in all the reports so far, and with normal distribution, there is not even a qualitative agreement with the reported data on void fraction variations. Distributions with asymmetric density functions such as exponential, Weibull, gamma and beta, show considerable improvement; beta distribution being the best. However even the best results with beta distribution show satisfactory agreement with the experimental data only up to about 2dp from the wall.
Simulations with the cluster growth model, modified to account for the confining nature of the wall, lead to more satisfactory results. The proposed algorithm consists of building up the cluster, sphere by sphere, by calculating all possible interior and wall sites for placing an incoming sphere in a stable and non-overlapping position on the current cluster. A preference parameter is defined to place the new sphere at locations along the cross section of the column at which the experimental void fraction profiles show prominent minima, that is, locations around which the bed has relatively high solid volume. Void fraction profiles in beds of various aspect ratios simulated by this model show good agreement with the corresponding experimental data. The structural characteristics of the high aspect ratio beds thus simulated are evaluated. The number of spheres per unit length, Ni is correlated with the aspect ratio. It becomes proportional to the square of the aspect ratio, with the proportionality constant being close to 0.9, for aspect ratios greater than about 10. This follows since in these beds the overall void fraction becomes constant at 0.4.
Majority of the spheres have contacts (with neighboring spheres) between 4 and 7, with the lower and upper limits for the coordination number being 2 and 9. The radial profile of the average coordination number (averaged over the height of the bed at the given radial position) shows small oscillations about a mean value of about 6 over almost the entire bed cross section starting from a distance of about ldp from the wall. At a distance of 0.5dp from the wall the predominant number of contacts is four while the mean value is about 4.3. The overall coordination number (averaged over the entire bed) shows inverse dependence on the aspect ratio. For random packings, that is, as the aspect ratio becomes infinity, the overall coordination number tends to six which corresponds to regular cubic arrangement.
Cumulative number fraction, CNf is a global measure of the arrangement of spheres in beds of high aspect ratio. Its radial variation shows four distinct regions whose locations are independent of the aspect ratio The CNf values in each region are correlated with aspect ratio The correlations combined with that of NL lead to a very useful and effective model for predicting void fraction profiles in a bed of any specified aspect ratio The validity of the predictive model is demonstrated
3
Rao, Ammavajjala V. S. "Structural Characteristics Of Randomly Packed Beds Of Spheres." Thesis, Indian Institute of Science, 1994. http://hdl.handle.net/2005/133.
Full textAbstract:
Packed beds find extensive application in a wide variety of industries to cany out a large number of diverse processes. The main objective of the present work is to develop models to predict the arrangement of particles and based on them, to determine and evaluate the structural characteristics of packed beds. These problems have received only a limited attention in the literature. As a first attempt, spheres of uniform size are considered.
Beds of aspect ratio up to 2 (referred to as low aspect ratio beds) are analyzed by application of principles of analytical geometry. Expressions are derived for the location of particles and for the structural characteristics of the beds, both of which show periodicity. This leads to the concept of a unit cell which is the repetitive section of the bed whose characteristics are the same as those of the complete bed. The beds fall into three distinct groups — those with aspect ratio between 1 and l√3⁄2, between 1√3⁄2 and 2, and with aspect ratio 2. Equations are distinct for each group. The aspect ratio shows marked influence on the structural characteristics of the beds. Agreement of the predictions on the overall void fraction with the available experimental data is excellent. Radial void fraction profiles are estimated by defining a concentric cylindrical channel (CCC) of an arbitrary thickness and with the cylindrical surface through the radial position of interest located at the middle of the CCC, and by accounting for the solid volumes of all the segments (in this CCC) of spheres with centers lying within a distance of a particle radius on either side of the cylindrical surface. The curved boundaries of the sphere segments are rigorously accounted for. The results show that the entire bed is filled with variations in the void fraction, starting from a value of unity at the wall and zero (or close to zero) towards the axis of the bed.
Monte Carlo model for the simulation of high aspect ratio beds has not proved successful even with any of a wide variety of distribution functions for the coordinates of the sphere dropping point. With uniform distribution, the only distribution used in all the reports so far, and with normal distribution, there is not even a qualitative agreement with the reported data on void fraction variations. Distributions with asymmetric density functions such as exponential, Weibull, gamma and beta, show considerable improvement; beta distribution being the best. However even the best results with beta distribution show satisfactory agreement with the experimental data only up to about 2dp from the wall.
Simulations with the cluster growth model, modified to account for the confining nature of the wall, lead to more satisfactory results. The proposed algorithm consists of building up the cluster, sphere by sphere, by calculating all possible interior and wall sites for placing an incoming sphere in a stable and non-overlapping position on the current cluster. A preference parameter is defined to place the new sphere at locations along the cross section of the column at which the experimental void fraction profiles show prominent minima, that is, locations around which the bed has relatively high solid volume. Void fraction profiles in beds of various aspect ratios simulated by this model show good agreement with the corresponding experimental data. The structural characteristics of the high aspect ratio beds thus simulated are evaluated. The number of spheres per unit length, Ni is correlated with the aspect ratio. It becomes proportional to the square of the aspect ratio, with the proportionality constant being close to 0.9, for aspect ratios greater than about 10. This follows since in these beds the overall void fraction becomes constant at 0.4.
Majority of the spheres have contacts (with neighboring spheres) between 4 and 7, with the lower and upper limits for the coordination number being 2 and 9. The radial profile of the average coordination number (averaged over the height of the bed at the given radial position) shows small oscillations about a mean value of about 6 over almost the entire bed cross section starting from a distance of about ldp from the wall. At a distance of 0.5dp from the wall the predominant number of contacts is four while the mean value is about 4.3. The overall coordination number (averaged over the entire bed) shows inverse dependence on the aspect ratio. For random packings, that is, as the aspect ratio becomes infinity, the overall coordination number tends to six which corresponds to regular cubic arrangement.
Cumulative number fraction, CNf is a global measure of the arrangement of spheres in beds of high aspect ratio. Its radial variation shows four distinct regions whose locations are independent of the aspect ratio The CNf values in each region are correlated with aspect ratio The correlations combined with that of NL lead to a very useful and effective model for predicting void fraction profiles in a bed of any specified aspect ratio The validity of the predictive model is demonstrated
4
Hargraves, J. C. "The performance of packed bed regenerators." Thesis, University of Bradford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375104.
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5
Krist, Thomas. "Optimalizace zásobníku tepla typu "packed bed"." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417062.
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Tato diplomová práce se zabývá tématem výměny tepla v zásobníku tepla typu ”packed bed”. Cílem je popsat přenos tepla v zásobníku tepla obsahující kamínky malých průměrů, skrz který proudí horký vzduch. Toto je modelováno v prostředí MATLAB. Na začátku je krátký úvod do problematiky zahrnující ukládání tepla a jeho možné využití. Dále je uveden krátký přehled o základech přenosu tepla, typech přenosu tepla a termofyzikální vlastnosti systému vzduch-kámen. Ve třetí kapitole je představen zásobník tepla typu ”packed bed” a rozličné modely a dané podmínky jsou vysvětleny. Další kapitola se zabývá s numerickými metodami, převážně s metodou konečných diferencí použitou v této práci. Pátá kapitola se zaměřuje na obecnou optimalizaci daného problému přenosu tepla. Populačně založený metaheuristický optimalizační algoritmus zvaný Genetický algoritmus je popsán. Sestavení modelu je ukázáno v šesté kapitole, stejně jako prezentace výsledků získaných z programu MATLAB. V poslední kapitole je pak diskutován závěr a doporučení.
6
Ryan, Jennifer S. "Char combustion in a packed bed reactor." Thesis, University of Ottawa (Canada), 2000. http://hdl.handle.net/10393/8964.
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This study reports on overfeed packed bed char combustion experiments and modelling. Experimental results are used to verify the assumptions of an existing char combustion simulation. The computer model uses finite volume discretization methods to predict temperature and concentration profiles for packed bed char combustion. Also, the behaviour of ash in a packed bed is explored and incorporated into the model by accounting for the effect of ash on such properties as bed void fraction and heat and mass transfer processes. The effects of air flow rate and bed depth on the burning rate, the bed temperature and gas concentrations are also examined. Experiments were performed in a reactor 23 cm in diameter and 20 cm high. Thermocouples measured bed temperatures and a water-cooled probe sampled bed gases. Gas samples were analysed for CO2, CO and O2 using a gas chromatograph. The fuel was foundry coke with a particle diameter in the 1 cm size range. Experiments were run for bed heights ranging from 5 to 15 cm and air flow rates of 191 to 520 kg/m2hr. Comparison of the experimental bed profiles and burning rates with model predictions shows good agreement, indicating that the model can reliably predict packed bed char combustion. Species concentrations are shown to be only dependent on bed depth; whereas the burning rate is a function of both the bed depth and air flow rate. The data also show that the ash properties are highly dependent on the operating conditions; since the model predictions are very sensitive to the ash properties, a relationship between ash properties and temperature needs to be developed and included in the model. More research is also needed on the CO2 reduction reaction parameters and pore diffusion model and the oxidation kinetics in the ash layer.
7
Girgis, Elisabeth. "Fuel devolatilization in packed bed wood combustion." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26645.
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Packed bed combustion is the burning of solid fuel particles supported by a grate with the combustion air supplied from below. The combustion process is divided into four main stages: drying, devolatilization, volatiles combustion and char combustion. Biomasses proposed as renewal energy sources, such as wood, have a very high volatile content (∼80%). Therefore mechanistic models developed for the prediction of bed characteristics during biomass combustion must include devolatilization and volatile combustion stages in order to correctly predict combustion behaviour for better emissions control and process efficiency. A novel in-situ sampling method for tar, a major pyrolysis product, was developed that allows its concentration to be measured at various heights within the packed bed and appears to work satisfactorily. A series of experiments on packed bed combustion were conducted in a laboratory 'pot' type combustor. Two different equivalent particle size diameters (2.8 cm and 3.2 cm) of untreated spruce wood and two different airflow rates (0.025 kg/m2s and 0.03 kg/m 2s) were tested at a 22 cm bed height. Although the experimental data show scatter, the measurements indicated that pyrolysis occurred primarily within two particle diameters of the top of the bed, with large amounts of tar and CO and somewhat less CO2 being produced. This research also expanded a numerical model for packed bed combustion of solid fuels with the addition of a simple first order pyrolysis reaction, in which fixed proportions of the products were set as light volatiles of CO and CO2 with the balance as tar. The model results compared well with bed temperature, particle size and density measurement throughout the bed and gas concentration (CO, CO2, O2, and CH4) measurements in the reduction and oxidation zone.
8
Ryan, Jennifer. "Char combustion in a packed bed reactor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0019/MQ58500.pdf.
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9
Burns, John Robert. "Liquid distribution in a rotating packed bed." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308010.
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10
Chang, Boon Fuei. "A non-wetting packed bed gas scrubber." Thesis, University of Sheffield, 2003. http://etheses.whiterose.ac.uk/15160/.
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Present integrated gasification combined cycle (IGCC) systems demonstrate high system efficiency and impressive environmental performance, giving them an edge over conventional pulverised fuel power stations. A key area in the development of IGCCs is hot fuel gas clean-up (HGCU). Fuel gas cleaning at elevated temperatures reduces thermal efficiency losses associated with gas quenching in conventional cold gas cleaning methods. Current hot gas desulphurisation techniques focus on the use of regenerable metal oxide sorbents, however the long-term sorbent performance issues have yet to be fully addressed. A fresh and radical approach may provide the key to overcoming the inherent limitations associated with metal oxide sorbents. A molten tin irrigated packed bed scrubber adopted in this research project is one such innovative way forward in HGCU. The hot scrubber offers the prospect of a multicomponent clean-up device. High-temperature sulphur removal takes place via absorption of H2S (and COS) into molten tin whilst discrete molten tin droplets and rivulets on the packing surface act as solid particulate collectors. The primary aim of this research project was to investigate the workings of a small-scale room temperature packed bed scrubber operating under non-wetting flow conditions analogous to the molten tin irrigated scrubber. Water irrigation of low surface energy packings simulated the nonwetting flow of liquid metals. The air-water analogue of the liquid metal scrubber provided the platform for hydrodynamics (flow visualisation, flooding and liquid holdup), particulate removal and mass transfer studies under non-wetting flow conditions. The performance of a small air lift for water circulation through the column was also investigated. These cold studies offered insight into the operation and performance of the liquid metal hot scrubber. Prior to the cold gas scrubber studies, preliminary small-scale gasification tests on petroleum coke samples were performed to investigate the effect of molten tin on H2S in the product fuel gas. The tests provided actual experimental evidence of the possibility of sulphur removal by molten tin in a gasification environment. It was shown that the maximum possible size of a liquid droplet hanging from a non-wetting spherical solid surface could be predicted from the liquid surface tension and density based on force balance. The mobility of static holdup in a non-wettable packed bed has been demonstrated, this being due to the tendency for the liquid to form discrete droplets rather than spreading films. Existing flooding and liquid holdup correlations that hold for conventional wettable packed beds were shown to be inadequate where non-wetting systems were concerned. Summary hence alternative methods applicable to the latter were sought. The introduction of a non-wetting tendency factor based on the ratio of the solid critical surface tension to the liquid surface tension, enabled the flooding capacities of non-wetting systems including those of this study to be predicted using Sherwood et al. 's graphical flooding correlation. The total volumetric liquid holdup was well correlated against the bed pressure drop, true gas velocity and gas density, offering the prospects of predicting holdup for systems using the same spherical packing. In general, the water-irrigated packed bed showed good hydrodynamic similarities to liquid metal systems, suggesting a dominating influence of liquid-solid contact angle which overrides striking differences in liquid physical properties. The performance of the small air lift pump was unaffected by varying the number of gas ports on the injector without any change to the hole size. The operating curve of the air lift pump could be predicted with good accuracy using momentum balance and two phase flow theory, provided that all major pressure losses in the system were accounted for, including notably the downcomer friction losses and accelerative effects. The non-wetting packed bed scrubber demonstrated impressive dust removal performance. Total separation efficiencies as high as 99.6% and cut sizes approaching submicron were achieved. Dust particles larger than about 6.5 um can be separated to efficiencies greater than 98%. Complete particle separation was achieved in all cases for dust particles larger than 16 J..lm. Particulate removal in a packed bed of spheres under non-wetting flow conditions has also been modelled using computational fluid dynamics (FLUENT). Simulation results showed that particle separation efficiency increases with particle size and density, but is unaffected by particle concentration. The predicted particle size corresponding to 98% efficiency is about 40 J..lm. In mass transfer, the height of the gas film transfer unit of various non-wetting spherical packed bed systems including those of this study was correlated successfully against the gas phase Reynolds number, the liquid superficial velocity and the packing diameter. Results from the cold gas scrubber studies have offered insight and understanding into the workings and development of the liquid metal packed bed gas scrubber. Findings and correlations derived from the water model studies, occasionally complemented by data from other non-wetting systems, have provided the means to predict the hydrodynamics, particulate removal capability and mass transfer performance of the liquid metal based gas scrubber. The pilot unit of the hot gas scrubber has been designed and fully constructed. The high temperature gas cleaning facility is ready for commissioning.
11
Akanji, O., and AV Kolesnikov. "Modelling of Hydrogen Adsorption/Desorption in Metal Hydride Reactor." American Scientific Publishers, 2010. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001925.
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Abstract
In order to make efficient hydrogen storage utilization as a fuel in fuel cell plant, there is need
for its effective storage. Previous studies on hydrogen storage considered the hydrogen adsorption/
desorption in radial direction only which is one dimensional approach in this project, two dimensional
computational model is implemented in CFD software to simulate the diffusion and heating
of hydrogen in both radial and axial directions. The model consists of a system of partial differential
equation (PDE) describing two-dimensional heat and mass transfer of hydrogen in porous matrix.
Mathematical model was developed to simulate heat and mass transfer in a packed bed reactor with
metal hydride as a material for hydrogen absorption and desorption. Importance of bed porosity
radial distribution and correct equation for effective thermal conductivity is discussed.
12
Gunjal, P. R. "Flow modeling and mixing in packed bed reactor." Thesis(Ph.D.), Indian Institute of Technology, Bombay, 2005. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2487.
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Brooks, Paul David Edwards. "The design of moving packed bed high temperature heat exchangers." Thesis, University of the West of England, Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321834.
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Motil, Brian Joseph. "Gas-Liquid Two-Phase Flow through Packed Bed Reactors in Microgravity." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1133468615.
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Al-Meshragi, Mohamed. "An investigation of radial heat transfer in packed beds." Thesis, University of Salford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253077.
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Sabri, M. N. "Models for the analysis of thermal dispersion in packed beds." Thesis, Swansea University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378831.
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17
Adler, Neal Cary. "Dairy Manure Flushwater Treatment by Packed-Bed Anaerobic Digesters." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1025.
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Wastewater treatment performance of three pilot-scale packed-bed anaerobic digesters with walnut shell medium was researched for treating dairy freestall barn flushwater. Reciprocation mixing was evaluated as a means to lessen channelization in the media bed and to improve biogas production and organic matter removal at ambient temperatures. Reciprocation has been used in biological nitrogen removal systems to introduce air into the system to repeatedly oxygenate nitrifying biofilm along with mixing (Behrends et al. 2003), but the anaerobic systems benefit from mixing. Two tanks were used in each system, where one was full and one was empty at any given time. Water was repeatedly pumped from one tank to the other and back again (reciprocation). A key research objective was to determine the minimum reciprocation frequency (between 0-10 per day) while still maintaining moderate methane production and treatment performance. Broken walnut shells with a specific surface area of 360 m2/m3 were used as the packed media. Digester influent, which was pretreated to remove large solids, had the following characteristics: total solids (TS) of 5.5 g/L, volatile solids (VS) of 2.8 g/L, 5-day carbonaceous biochemical oxygen demand (cBOD5) of 800 mg/L, and chemical oxygen demand (COD) of 4340 mg/L. Average digesting liquid temperatures ranged from 14.1 to 23.6 °C. At 6-day theoretical hydraulic residence times (V/Q where V is Lliquid, which is volume of liquid occupying the digester pores, and Q is total daily influent flow) and 1 reciprocation per day, methane production was 0.060 ± 0.10 LCH4/Lliquid-day and at 10 reciprocations methane production 0.058 ± 0.14 LCH4/Lliquid-day (mean ± standard deviation of measurements over time). COD percent removals were both 51% at 6-day V/Q. Since multiple reciprocations did not appear to make a difference in methane production and treatment performance, fewer reciprocations were used in subsequent experiments. Higher flow rates were also used in subsequent experiments to accelerate sludge clogging and channelization in the walnut-shell bed and thereby allow detection of any advantage provided by reciprocation compared to an upflow reactor. At 0 and 1 reciprocations per day and 0.35 and 0.50-day V/Qs, respectively, methane production was 0.24 ± 0.08 and 0.23 ± 0.08 LCH4/Lliquid-day and COD percent removal was 17 and 22%. Over the study period of 226 days, walnut shell porosities decreased due to sludge accumulation from 0.68 and 0.64 (start-up or clean-bed) to 0.31 and 0.24 in the 1 and 0 reciprocation per day reactors. Sludge accumulation and channelization did not appear to be affected by reciprocation mixing on the scale of this study.
18
Halliday, K. "The potential of the radially-stratified packed bed as catalytic chemical reactor." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384498.
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Freiwald, Martin Georg. "Transport processes in packed beds of low tube to particle diameter ratio." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387132.
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Tuck, Arden R. C. "Modelling of particle pyrolysis in a packed bed combustor." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27491.
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The combustion process of a dry wood particle within a packed bed combustor starts with the heat up and devolatilization of the wood to form char which then travels down through the reduction and oxidation zones to complete the combustion process.
This thesis describes the development of a computational model for overfeed packed bed combustion of wood and other biomass fuels, including the modelling and tracking of individual particles within the devolatilization region of the bed. It builds on an earlier continuum bed model, with no description of processes within individual particles. A numerical model for the heat-up and pyrolysis of an individual particle is developed and numerically tested to determine the preferred grid sizing, time step (Deltat) and node number. The impact of particle density, size, the heat of pyrolysis and kinetics on devolatilization are studied. The particle model is then incorporated into the overall bed model by developing a mechanism for particle tracking in the devolatilization region of the bed, coupled with interpolation processes to transfer information between the bed and the particles. The resultant model shows that the model not only produces more detail about particle processes in the combustor but also produces profiles that compare well to the Girgis (2004) experimental data.
21
Mehrvar, Mehrab. "Kinetic modelling and a novel packed bed photocatalytic reactor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0003/NQ30630.pdf.
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Piché, Simon. "Prediction of packed bed hydrodynamics using neural network computing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ57835.pdf.
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Underhill, K. "Network analysis for modelling transport in packed bed reactors." Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382920.
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Perry, Steven D. (Steven David). "Packed fiber bed reactor design for animal cell culture." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/17220.
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O'Neill, Kerry. "Packed bed systems : an insight into more flexible design." Thesis, Teesside University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518728.
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Rashidian, Babak. "Deflector effects in fixed bed (biomass) combustors and non-combusting packed beds." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2016. https://ro.ecu.edu.au/theses/1937.
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Combustion can be used to thermally process biomass fuels and yield both heat and power in a sustainable manner. At present, direct combustion of solid biomass is the primary approach for generating electricity and heat when these fuels are used at a commercial scale.
Deflectors have been used in the freeboard section of industrial combustors to reduce radiant heat loss through flue gases and for particle emissions abatement. Freeboard deflectors can also influence emissions and freeboard temperature distributions by changing the flow dynamics. Despite much research into laboratory scale biomass combustion and packed beds, there have been no systematic studies into the impact of deflectors (heat shields) on the axial and radial temperature profiles, test methodologies used or the emissions in laboratory scale fixed bed biomass combustors operated on pelletised fuels.
Through a combination of experiments and numerical simulations, this research has investigated such issues in both high temperature fixed bed biomass combustors as well as relatively lower temperature (non-combusting) packed beds subject to different heating modes.
Experiments have been carried out on a laboratory scale (continuous feed) fixed bed combustor featuring both primary air (supplied through the fuel bed) as well as secondary air (in the freeboard). A freeboard deflector was located at different axial locations during this testing. The aim was to characterize deflector effects on burning rate, temperature distribution (near-wall and near-centreline) and gaseous emissions (NO, CO, CO2) over a range of primary and secondary air flow rates. A systematic method has been developed to establish the steady state time period during the combustion process. In this regard, detailed analyses on the time series of thermocouples, emissions and fuel mass conversion data have been performed. The proposed method is based on calculating the percentile mean deviation of temperature and NO/CO emissions data which can provide a more effective means of resolving the stand of the steady state operating, compared to only using the time evolution of these variables. In addition, the significance of the thermocouple radiative corrections (losses) and its effect on the accuracy of measured temperatures has been investigated. The results concluded that NO, CO and CO2 emissions are affected by the presence of a deflector in the mid-range of combustion stoichiometry (λ=0.439-0.509). However, deflector effects were found to be most prominent for NO and CO emissions by reducing and rising their levels, respectively. Deflectors affect upstream near-wall temperatures, but their impact depends on relative (axial) position (H). Furthermore, results reveal that deflectors do not have significant effects on the burning rate and flow availability of the exhaust gases.
A CFD model of a porous media has been implanted to study the effects of freeboard deflectors on the heat transfer inside packed bed columns for the temperature range of 100°C to 400°C (which is typical for drying and volatile release in biomass combustion). Results show that the deflector do affect temperature profiles along the freeboard as well as wall temperatures but this is dependent on the mode of heating and emissivity of the deflector.
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Abou-Ziyan, H. Z. Z. "Heat and momentum transfer in porous material used for thermal energy storage." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233826.
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Meng, Xuewei. "Flow Through, 2D/3D Nanoplatelet Supports for Packed Beds and Columns." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38445.
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High performance catalyst supports and packing materials are playing an increasing role in many reactions and separations. The dispersion in packed bed reactors and separation columns can be reduced by the development of new packing structures having open and connected pore geometries. The application of new materials in High Performance Liquid Chromatography (HPLC) with sub 5 micron particle sizes are growing. These small particles offer better performance and improved bed and column efficiencies. Recently developed, twinned Alumina Nanosheets (TAN) are 2D/3D nanomaterials that offer promising open geometries for use as column packings and catalysts supports. They have a small particle size (4 um in length, 1 um in width and 0.1 um in thickness) and excellent flow-through capabilities. TANs have recently been used to successfully produce high throughput dynamic membranes.
However, their resistance to compaction is unknown and thought to be limited. A technique was developed to reinforce the TAN nanomaterial. Two binder materials were tested as reinforcing agents; SiO2 and AlH6O12P3. The binder-reinforced TANs were then packed into columns. Eleven columns having a 4 cm initial packing length were assembled. Tracer injection studies were performed to investigate the flow behavior and dispersion in these columns. SEM images were also taken to characterize the particles before and after compaction. The best results were obtained using a binding solution containing 7.5 (wt%) SiO2. The binder SiO2 offered a better resistance to compaction than the AlH6O12P3. The Peclet (Pe) number for the columns ranged from 22 to 648. When the content of SiO2 increased from 0 to 7.5 (wt%), the columns showed an increase in the Pe number. When SiO2 increased from 7.5 to 20 (wt%), the columns showed a decrease in the Pe number. However, AlH6O12P3 did not present any relation between the binder content and the Pe number.
The results of this work demonstrate that reinforced TANs, are a new type of material that offers a packing with an open pore structure and improved channel connectivity. The new reinforced material offers considerable potential in many applications such as catalysis and separations over conventional materials. If they are used as packing materials in HPLC columns or packed bed reactors, they can contribute to a higher separation efficiency or an enhanced conversion rate or productivity, bringing more advantages and benefits than ordinary packing materials.
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Cooper, Judy. "A numerical model for char combustion in packed bed reactors." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9679.
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A numerical simulation of the combustion of centimeter-sized char particles in an overfeed fuel bed is presented. One-dimensional mass, species and energy balances for the reading system are solved by finite volume discretization methods to predict operating curves and temperature and concentration profiles for char combustion under a variety of conditions. The simulation is unique in that it employs separate gas and solid phase energy balances with finite-rate CO kinetics and a particle number balance to account for the shrinkage of the char particles as they descend through the bed. All the major energy transport processes, such as particle-to-fluid heat and mass transfer, conduction, convection and radiation, are modelled. The simulation was run for beds of 1-3 cm particles ranging from 30-60 cm in height. The range of air flow rates studied ranged from 0.036 to 0.87 m/s. Comparisons between predicted gas and temperature profiles and similar profiles obtained from the literature generally showed good agreement, indicating that the simulation was reliable enough for use as a design tool over the range of conditions that were studied. The simulation proved to be quite sensitive to choices of the heat and mass transfer coefficients and also to the CO$\sb2$ reduction rate expression, indicating that there is a need for more research on large-particle kinetics and high-temperature packed bed energy transport processes.
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Smith, Robert James. "Oxidative extraction of chlorinated pulp in a packed bed reactor." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/10265.
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Van, der Walt Andries Johannes Kellerman. "Pressure drop through a packed bed / A.J.K. van der Walt." Thesis, North-West University, 2006. http://hdl.handle.net/10394/4330.
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Tuddenham, Read Stapley. "Thermal hydraulic analysis of a packed bed reactor fuel element." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26300.
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Lau, Anna. "Effect of pulsatile flow on liquid phase packed bed adsorption." Thesis, University of Bath, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362237.
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Bravo, de Nahui Flora. "Mass transfer behaviour for a packed bed copper cementation system." Thesis, University of Exeter, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234559.
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Lukin, Ilya [Verfasser]. "Rotating Packed Bed Application for Aroma Recovery Intensification / Ilya Lukin." München : Verlag Dr. Hut, 2021. http://d-nb.info/1232847844/34.
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Hall, Stephen. "Optimisation of biogas production from percolating packed bed anaerobic digesters." Thesis, University of South Wales, 1986. https://pure.southwales.ac.uk/en/studentthesis/optimisation-of-biogas-production-from-percolating-packed-bed-anaerobic-digesters(6825c6bf-4ee7-439e-832a-28aa8b7cd4d3).html.
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Percolating packed bed digesters were operated successfully in a batch mode using a wheat straw - dairy manure substrate of between 21 and 27% total solids. The vessels used had a nominal 10 1 volume and were constructed of perspex. Temperatures of 25-35°C were used, recirculation rates of 0-15 litres.hr-1 (the digesters having a diameter of 0.18 metres thus corresponding to superficial flow rates of between O and 0.382 l/m2 /hr), solid : liquid ratios of 1:1 to 4:1 and bed heights of 0.26 to 2.05 metres. The optima found were a temperature of 35°C, recirculation rate of 3 litres.hr1-, a solid: liquid ratio of 2:1 and a bed height of 1.5 metres. Experiments were conducted for periods of up to 70 days, though operation beyond a 40 day period was found to produce little extra biogas. The performance compared favourably with other high solids waste digesters with gas yields of 0.305 m 3 /kg VS added and solids losses of 47% volatile solids and 64% cellulose being obtained over a 40 day period. No major problems of inhibition or blocking occurred. Linking of digesters in series via their recirculation systems was found to be advantageous. Gas yields were found to be increased by approximately 18% and solids losses increased by approximately 20% when the waste was treated in this semicontinuous manner. These increases were found to be a result of the rapid transfer of well-adapted bacteria to the fresh digester. Lag phase in the fresh digester was reduced by three days and potentially inhibitory levels of volatile fatty acids were not present. Concentrations of up to around 5000 ppm VFAs were found during the start-up of batch digesters causing some inhibition of gas production. During semi-continuous operation however concentrations of around 2000 ppm were developed when fresh digesters were linked in, no inhibition occurred and in fact this concentration proved stimulatory to gas production. Experimentation into the optimum retention time of a maximum of three digesters in series was conducted, with retention times of 90, 60 and 30 days being considered. A 30 day retention period was found to depress gas production due to unstable conditions when fresh digesters were added by up to 32% compared with Batch Operation. Gas production was increased at both 60 and 90 day retention times by amounts similar to those previously stated. A retention time of 60 days was found to be optimum as little extra gas was produced after this time, with volatile solids losses being increased by only 9.3% by operating for a further 30 days. Colonisation of the solid substrate was shown to be rapid, by the use of adenosine 51 triphosphate analysis, gas production rate and electron microscope analysis. In addition a dynamic bacterial population appeared to be present in the solid phase with the rates of growth and attachment being approximately equal to the rates of decay and detachment. When digesters were operating in their steady phase, methanogens were present in the liquor at concentrations of between 10 6 - 10 7 /ml and non-methanogens at between 10 7 - 108 /ml showing a large population of bacteria to be present for the inoculation of fresh digesters.
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Yang, Mengyan. "Thermal monitoring for the control of packed bed adsorption chromatography." Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334658.
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Reynders, Frederik Jakobus Wilhelm. "Gas-limited hydrogenation of 1-octene in a packed bed reactor." Diss., University of Pretoria, 2011. http://hdl.handle.net/2263/26555.
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Jalalabadi, Hassan Khodaei. "Thermal conversion in biomass: Single particle drying and packed-bed combustion." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2016. https://ro.ecu.edu.au/theses/1959.
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Biomass combustion is widely seen as a key source of sustainable energy. To better understand some of the factors that affect the performance of biomass combustors, both theoretical and experimental studies are undertaken on laboratory scale burners. The present study provides an overview of the methodologies employed to model laboratory-scale fixed-bed combustors. This thesis contributes to Computational Fluid Dynamic (CFD) modelling of evaporation for different single biomass particles and also experimental application of different secondary air flow rates, configurations and positions on the particulate and gaseous emissions of combustors.
The overview covers a wide range of biomass combustion topics ranging from modelling and experimental studies of both single and packed bed combustors particularly for laboratory scale fixed-bed systems. It also includes treatment of the fundamental thermo-physical fuel characteristics that should be considered when undertaking macro-scale (bed-level) modelling. The work concludes with overall observations on the modelling of fixed-bed combustion as well as opportunities for further research to resolve specific challenges.
The evolution of various single biomass particles during the drying process is investigated to achieve a deeper understanding of their thermal behaviour. The two most conventional models; Arrhenius and Heat sink models have been employed for modelling several single biomass particles in simulations using Ansys-Fluent 15 software (Research version). Several sub-models are implemented in a commercial CFD code to simulate two different evaporation models. To predict transient evolution of wood composition (moisture and dry wood); the transport equations (energy and moisture evaporation) are modelled to assess reaction, heat loss, effective thermal conductivity, specific heat capacity and radiative and convective heat transfers between the particle and surrounding environment. The developed models show close agreement with a set of previous works (experimental and numerical).
The results indicate that the geometric shape of the particle and the external boundaries that are exposed to radiation and convection strongly influences the evaporation process. The results of this study will be used to model the drying process in fixed-bed combustion (future studies).
Secondly, an experimental study of the effect of air staging distribution and position on particulate emissions in a laboratory scale biomass combustor is performed. Detailed analyse of the temperature in primary and post combustion zones, burning rate, and PM emissions in a fixed-bed laboratory scale combustor are undertaken. Two different secondary air distribution designs, uniform and nonuniform secondary air distribution system, for two different positions are assembled above the bed. The contribution of temperature, secondary air flow rates, configuration and distance from the bed level into burning rate, outflow heat, CO and PM concentrations are investigated. Uniform distribution of secondary air flow rate results in remarkable decrease in particulate matters (PM) and 50% CO emissions. The air staging strategies have been employed to study the effect of burning rate, temperature in primary and post combustion zones, and formation of NO, CO and PM emissions, taking into account the air to fuel stoichiometric ratio. Approximately 40% NO reduction is achieved due to application of non-uniform air distribution at higher secondary air flow rates.
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Pringle, Tom. "Novel routes to potential packed bed absorbents for the desulphiding reaction." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/11278.
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Three interdependent areas of investigation were conducted in order to formulate a repeatable, reliable and simple set of procedures to synthesize, characterize and assess the potential desulphiding ability of the synthesized materials. The exclusion of atmospheric carbon dioxide throughout the sequence of preparation, characterization and assessment and the transfer processes between these stages was a key component of the design strategy and final success of these procedures. The three areas of investigation were: (i) synthesis of precursor materials; (ii) development of air-free apparatus and regimes for the hydrolysis of precursors and the collection and transfer of hydrolysis products to air-free apparatus for analysis and; (iii) investigation of the properties of the products using purpose built equipment. The aim of the syntheses was to prepare contaminant free samples of ZnO, Zn(OH)<SUB>2</SUB> or any other structurally modified compounds of zinc which may have activity as desulphiding reagents. The hydrolysis of zinc-based complexes containing oxygen-donor ligands was found to be a productive route to generating such structurally modified compounds of zinc. Basic zinc carboxylates (in particular hexakis(μ-2-acetato-O-O')-(μ-4-oxo)-tetrazinc, Zn<SUB>4</SUB>O(O<SUB>2</SUB>CCH<SUB>3</SUB>)<SUB>6</SUB>) were found to be the simplest to prepare, with good yields and high levels of purity (ascertained by the absence of surface carbonate contaminants). These offered a rich source of structurally novel materials. The preparation of these materials led to the crystallographic determination of the structure of hexakis[μ-(propanato-O:O')]-μ<SUB>4</SUB>-oxotetrazinc, Zn<SUB>4</SUB>O(O<SUB>2</SUB>CCH<SUB>2</SUB>CH<SUB>3</SUB>)<SUB>6</SUB>. Two novel acetates of zinc were also discovered by sublimation of the neutral acetate. These have been assigned as the novel acetates Zn<SUB>8</SUB>O<SUB>3</SUB>(O<SUB>2</SUB>CCH<SUB>3</SUB>)<SUB>10</SUB> and Zn<SUB>2</SUB>(O<SUB>2</SUB>CCH<SUB>3</SUB>)<SUB>4</SUB>. In addition, mass spectral evidence supports the proposed existence of related multi-nuclear propionates.
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Roshani, Shahram. "Elucidation of local and global structural properties of packed bed configurations." Thesis, University of Leeds, 1990. http://etheses.whiterose.ac.uk/3153/.
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Some of the most common unit operations being used in the chemical industry are based upon packed bed configurations. Multi-tubular catalytic reactors are a prominent example of such systems which are believed by many experts to be the heart of the chemical profession and frequently the most expensive units of the plant. They offer extensive surface area between phases of the matter in a compact physical manner, and also are relatively easy to construct and maintain. The successfuld esign of such systems depends on models, which should describe the processes occurring within the fixed bed and must also be able to accurately represent the intrinsic behaviour of the reactor quantitatively. It is therefore necessary to have good estimates of the associated transport parameters, namely the wall heat transfer coefficient, effective radial and axial thermal conductivity coefficients and radial and axial dispersion coefficients, in order to design efficiently. Unfortunately, the accuracy of the design data for the prediction of these parameters are in doubt. They are considered to be unreliable because of being based on poorly defined packed bed models in terms of structure of the packing. The non-uniformities of voidage in the packing matrix must be appreciated and hence be included in descriptive models of the physical system in order to establish reliable design data. As the roles of modelling and experimentation are complementary, a number of beds comprised of equilateral cylindrical particles were prepared to examine their global and local structural properties, with a view to identifying and characterising features which could be used for prediction purposes. The microstructural details within packed beds were studied by means of an image analyser, so that the local variations of voidage in angular, axial and radial directions could be portrayed. It is only on the basis of this kind of information that a well-defined description of the bed structure becomes accessible. This research activity has been concerned with the study of several factors influencing the packing structure such as entrance/exit and wall effects, reproducibility and scaling problems. Also succeeding the accurate data acquisition stage, a number of correlations have been developed for a wide scope of diameter ratios covering the industrial range. These correlations allow the mean and local voidage distributions to be predicted reliably.
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Potters, Kimberlee. "Magnetic Resonance Imaging of columnar reactors." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336775.
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Domingos, Joana Margarida Bendada. "Acidogenic digestion of effluents of the cheese industry in packed bed biofilm reactors." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/10648.
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Dissertation for the Master degree in Biotechnology<br>The main goal of the present work was to study the production of volatile fatty acids (VFAs) from cheese whey powder (CWP) by employing a packed bed bioreactor (PPBR) for the anaerobic acidogenesis.
First experiments were performed in 100-mL Pyrex bottles to study the acidogenesis trends, namely: lactose consumption, VFAs and biogas production and composition. These tests were done with freely suspended-cells (control experiment) and with immobilized cells using granular activated carbon (AC) and ceramic cube Vukopor S10 supports. The utilized inoculum – an acidogenic mix
consortium- belongs to an analogous CWP digestion process in which a different culture system is being studied. Therefore, the incubations conditions were the same as for that culture system: 20 g/L of CWP (corresponding to 15 g/L lactose), 37ºC and pH 6. The observed trend consisted on lactose
consumption, lactic acid formation (as an intermediate product) and from this VFAs production. The best yield was obtained when Vukopor was used (87% against 30% for AC); after 9 days the VFAs was (g/L): acetic (1.6), propionic (2.4); butyric (6.6) acids.
The mentioned preliminary studies allowed selecting the operational hydraulic retention time(HRT) for the bioreactors.
Two recirculate 1-liter PBBR one filled with Vukopor and other with AC were developed. CWP
concentration, pH and temperature were the same as in the microcosm experiment. Both were operated in batch and continuous. In first batch performed in PBBR-Vuko it was achieved 6 g/L of propionic. However a loss of capability of producing it was observed during continuous operation. It was ascribed to a wash-out of related strains. With PBBR-Vuko were tested two different hydraulic
retention times (HRT), 9 and 6 days, instead for PBBR-AC only HRT of 9 days. The yields for PBBRVuko were the same as at the microcosms scale, 80% for both HRT. On the other hand, the yield for PBBR-AC was 20%, this is a confirmation that AC was not the proper support even at a 1-L scale.
Additionally to immobilization study, it was also set up a bioreactor with freely suspended cells. In this last mentioned bioreactor when a HRT of 6 days was set up it was observed a decrease in the VFAs yield to 44%. From this, it was concluded that the immobilization is an advantage for the VFAs production.
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Montràs, Boet Anna. "Mathematical modelling and molecular analysis of a nitrifying packed bed biofilm reactor." Doctoral thesis, Universitat Autònoma de Barcelona, 2009. http://hdl.handle.net/10803/5327.
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MELiSSA (Micro Ecological Life Support System Alternative) és el sistema desenvolupat per l'Agència Espacial Europea (ESA) i el consorci MELiSSA en el camp del suport de vida durant missions de llarga durada a l'espai. Basat en un ecosistema aquàtic, MELiSSA va ser concebut com una eina per desenvolupar la tecnologia necessària per a un sistema de suport de vida biològic que en un futur ha de permetre la producció d'aliment, aigua i oxigen a partir dels residus orgànics generats per una tripulació. <br/>Per assolir aquest objectiu, el concepte MELiSSA compta amb l'activitat combinada de cinc compartiments colonitzats per diferents microorganismes i plantes superiors, interconnectats entre ells. Aquesta tesi es centra en el tercer compartiment del bucle MELiSSA, en el qual l'amoni és convertit a nitrat, que és la font de nitrogen més adequada per al creixement dels cianobacteris i plantes superiors que colonitzen els compartiments fotosintètics. <br/>L'oxidació biològica d'amoni a nitrat té lloc en dues etapes successives que porten a terme dos tipus de soques bacterianes. En el projecte MELiSSA aquest procés es porta a terme en una columna de llit fix mitjançant Nitrosomonas europaea i Nitrobacter winogradkyi immobilitzats sobre un suport polimèric, i amb aportació d'aire en el mateix sentit de circulació que el medi líquid. El reactor pilot del tercer compartiment ha estat operant a la planta pilot del projecte MELiSSA durant períodes prolongats de temps abans de l'inici del treball realitzat en aquesta tesi. <br/>La principal aportació d'aquesta tesi es troba en l'obtenció de nova informació sobre el funcionament del reactor a través d'un estudi detallat de la biopel·lícula i també mitjançant el desenvolupament d'un model matemàtic que ens permetrà estudiar els efectes de diferents paràmetres d'operació sobre el procés i l'estructura de la biopel·lícula. S'implementaran també els aparells de mesura necessaris per millorar la qualitat de la monitorització de les diferents espècies de nitrogen a la fase líquida. Els coneixements adquirits en la realització d'aquest treball seran utilitzats per portar a terme el re-disseny del reactor per tal de millorar-ne el funcionament dins de la planta pilot del projecte MELiSSA.<br>MELiSSA (Micro Ecological Life Support System Alternative) is the system developed by the European Space Agency (ESA) and the MELiSSA consortium in the field of life support for long term manned missions in Space. Based on the principle of an aquatic ecosystem, MELiSSA was conceived as a tool to develop the required technology for a future biological life support system. Its final aim is the production of food, fresh water and oxygen from the organic wastes of a crew. <br/>To achieve this goal, the MELiSSA concept is based on the use of five interconnected compartments colonised by several microorganisms and higher plants. This thesis is focused on the third compartment of the MELiSSA loop, in which ammonium is converted to nitrate, the most suitable nitrogen source for the growth of the bacteria and higher plants colonising the photosynthetic compartment. The biological oxidation of ammonium to nitrate, which consists of two successive reactions carried out by two different bacterial strains, takes place in a packed bed biofilm reactor. Nitrosomonas europaea and Nitrobacter winogradskyi are immobilised on a polymeric support, with air flowing cocurrently with the feed medium. The pilot-scale reactor of compartment III (CIII) had been in operation in the MELiSSA pilot plant for several years before the start of the present work. <br/>The main contributions of this thesis are in increasing the understanding of the reactor performance by studying the nitrifying biofilm in depth, and by developing a mathematical model that allows the effects of different operational parameters on the process and on the biofilm structure, to be studied. Moreover, continuous monitoring of the nitrifying efficiency will be improved by installing the necessary on-line equipment to experimentally measure the concentrations of all the nitrogen species in the liquid phase. The additional knowledge achieved on the reactor performance via this work will finally lead to re-design the reactor hardware for optimal performance in the MELiSSA pilot plant. <br/>The knowledge acquired in this thesis was finally used to define the main features of the re-design of the pilot reactor of the MELiSSA compartment III.
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Vosoughi, Marcus M. "Numerical simulation of packed bed adsorption applied to a package dyeing machine." Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1514.
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Vamvakeros, Antonios. "Operando chemical tomography of packed bed and membrane reactors for methane processing." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/10027550/.
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Heterogeneous functional materials, like catalytic solids, batteries and fuel cells tend to usually possess complex structures where the 3D spatial distribution of the various components of these materials is rarely uniform. Such materials are known to change with time under operating conditions. In order to gain an insight into the structure-function relationships, it is essential to study them in situ with spatially-resolved techniques. The work presented in this thesis focuses on the development and application of synchrotron X-ray tomographic imaging methods to study various catalytic materials in real time and under real process conditions. The main X-ray tomographic imaging technique used in this study is X-ray diffraction computed tomography (XRD-CT) which couples powder diffraction with “pencil” beam computed tomography. Chapters 3 and 4 of this thesis outline some of the technical achievements accomplished in this work. More specifically, Chapter 3 outlines the development of a new data processing strategy used to remove line or “streak” artefacts generated in reconstructed XRD-CT images due to the presence of large crystallites in the sample; a common problem in XRD-CT measurements. Chapter 4 introduces a new data collection strategy, termed interlaced XRD-CT, which allows, post experiment, choice between temporal and spatial resolution. This data collection strategy can in principle be applied to all pencil beam CT techniques. The results from the first multi-length scale chemical imaging experiments of an unpromoted and a La-promoted Mn-Na-W/SiO2 catalyst for the oxidative coupling of methane are presented in Chapter 5. The spatially-resolved chemical signals obtained from these operando experiments provided new chemical information that can lead to the rational design of improved OCM catalysts. In Chapter 6, the results from, the first ever reported, XRD-CT experiments of working catalytic membrane reactors are presented. It is shown that the pertinent changes in the physicochemical state of these integrated reactor systems can be spatially-resolved. The results from Rietveld analysis of a 5D diffraction imaging (>106 diffraction patterns) redox experiment of a Ni-Pd/CeO2-ZrO2/Al2O3 catalyst and the first XRD-CT study of this catalyst during partial oxidation of methane are presented in Chapter 7.
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Chamchan, Nipon, and 子辰. "Validation of packed bed and rotating packed bed absorber model with pilot-plant data." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/77313375403665601453.
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碩士<br>國立清華大學<br>化學工程學系<br>104<br>In this research, the model of packed bed and rotating packed bed was validated with pilot plant data. The PB model was validated with Radfrac rate-based model on Aspen plus and in-house PB model on ACM platform, the simulation results showed good corresponding on both model. However, the mass transfer correlation model should be carefully select depends on the type of packing. With Billet and Schultes (1999) model demonstrate well with random packing but not in structured packing system. However, the model developed on Aspen plus and ACM show quite the same simulation results.
For Bravo (1985) and Hanley (2012), mass transfer correlation model show the good result on structured packing system and quite higher in random packing system.
Furthermore, RPB model was developed on ACM with an assumption as well as in PB model, but in different geometry absorber model. The RPB results demonstrated the satisfactory result with the experiment data. Therefore, the in-house model on ACM shows the reliable simulation result in the pilot plant scale.
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Okhuysen, Mary Ann. "A model packed bed filtration." Thesis, 2000. http://hdl.handle.net/1911/17368.
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A mathematical simulation model is developed that calculates the evolution of particle removal and headloss in a packed bed filter, as functions of the morphology of the colloidal particle deposits in the filter. The expressions derived are based on the postulate that particles form deposits that grow as mass fractals. The model is calibrated and validated with a set of laboratory data previously obtained. The calibrated value of fractal dimension was found to coincide with measurements obtained in an earlier study using light scattering. The effect of the filtration velocity and particle size on the fractal dimension of the deposits is evaluated. The hypothesis that higher filtration velocities create denser deposits is supported. However, a trend of increasing fractal dimension with decreasing particle size runs counter to theoretical expectations. The model is extended to include the effect of variable conditions in the influent.
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Lin, Jia Zhang, and 林佳璋. "Characteristics of rotating packed bed." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/66235297241789435698.
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Zhang, Jia Yu, and 張家諭. "Compared Rotating Packed Bed and Packed Bed Capture CO2 from Blast Furnace Vent and Solvent Assessment." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/50076504902731667280.
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碩士<br>國立清華大學<br>化學工程學系<br>103<br>Greenhouse effect main reason for the significant increase in global average temperatures since the industrial revolution. Greenhouse effect is most likely one of the reasons for the extensive use of fossil fuels so that the CO2 concentration in the atmosphere increased significantly. In order to suppress the rise in CO2 concentration, Energy saving and carbon reduction have become the key projects of the National Energy Policy Development Environment. For this purpose, we build a carbon capture system in steel plant and laboratory. As a basis for the application of various absorbents related research, and provide process improvement methods to achieve energy savings.
The study capture CO2 by 30wt% MEA solution and 4mPZ+4mDETA solution that was carried out in rotating packed bed connected gas stripper. The conventional packed bed absorber and stripper were replaced by a rotating packed bed for reducing the volumes of conventional packed bed absorber and stripper and the regeneration energy of chemical absorbent in CO2 capture process. Developed as a result of gravity rotating bed can improve the gas-liquid contact surface area. In the study, compared with conventional packed bed and rotating packed bed for CO2 capture efficiency at same fixed operation condition. It was found that both capture efficiency are similar, but the volume of rotating bed is the volume of the conventional packed bed 1/3 times.