Tesis sobre el tema "Chemical cleanings"
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1
Goujon, Christophe. "Conséquences des nettoyages chimiques sur la réactivité de la surface externe des tubes de générateurs de vapeur des centrales nucléaires à réacteur à eau sous pression". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066723.
Resumen
Les phénomènes d’encrassement et de colmatage des Générateurs de Vapeur (GV), essentiellement par la magnétite, constituent des enjeux majeurs pour la sureté et la performance des centrales nucléaires à réacteurs à eau sous pression. Ils ont pour origine principale la corrosion des tuyauteries en acier au carbone du poste d’eau du circuit secondaire. Depuis 2006, la stratégie de maintenance à long terme des GV du Parc nucléaire français repose sur l’application de nettoyages chimiques. Ce travail a pour objectif d’étudier l’effet des nettoyages chimiques sur la réactivité de la surface externe des tubes de GV des centrales REP. L’étude expérimentale s’est d’abord concentrée sur la synthèse de dépôts de magnétite, par voie électrochimique et hydrothermale, aboutissant à la formation de dépôts encrassants aux propriétés contrôlées. Parallèlement, l’encrassement des tubes de GV a été étudié in-situ sur la boucle d’essais FORTRAND (FORmation et Transport des Dépôts) par la reproduction des conditions physico-chimiques de corrosion-érosion du poste d’eau et des conditions représentatives de formation de dépôts dans les GV. Au préalable, l’oxydation des tubes a assuré la formation d’une couche de passivation en surface. Suite à l’encrassement, les caractérisations de surface indiquent la formation d’un dépôt encrassant de magnétite parfaitement recouvrant et dense. L’étude de l’effet des nettoyages chimiques a ensuite été réalisée dans la boucle d’essais spécifique ECCLIPS, conçue et construite dans le cadre de l’étude. La reproduction des procédés de nettoyages chimiques selon les conditions d’applications en vigueur sur le Parc français conduit à la dissolution pratiquement totale des dépôts encrassants. La conservation de la structure et de la composition de la couche de passivation confirme l’innocuité globale des procédés pour les tubes de GV. Enfin, le réencrassement des tubes nettoyés confirme l’absence d’effet des nettoyages sur la cinétique de formation des dépôts à court terme, donnée importante en vue de définir une fréquence de nettoyage des GV. A court terme, la différence de morphologie des dépôts réencrassants semble induire une porosité plus importante susceptible d’influer sur les performances thermiques des GV. A long terme, l’application plus régulière des nettoyages chimiques devrait limiter la densification des dépôts, particulièrement néfaste pour le transfert thermique, et donc produire des effets bénéfiques sur l’évolution des performances des GVIn the secondary circuit of nuclear Pressurized Water Reactors, magnetite (Fe3O4) deposits lead to Steam Generator (SG) fouling, decreasing the thermal performance and possibly enhancing the risk of SG tube cracking. As a counteraction, chemical cleanings have become the primary strategy to remove oxide deposits in SGs of the EDF fleet. The aim of this study is to investigate the effect of chemical cleaning on SG tubes surface reactivity. First, an electrochemical study was performed to deposit magnetite on substrates made of Inconel 600 and 690 (SG tubes materials). Thermodynamic calculations, voltamperometric studies and deposit characterizations were performed to define the experimental protocol. Magnetite films with a thickness up to several dozen on micrometers were grown by cathodic electrodeposition. Then, SG tubes were fouled in a specific experimental loop, FORTRAND. In this device, magnetite and soluble iron were formed and released in solution by carbon steel pipes corrosion in feedwater circuit representative conditions. Then, corrosion products were flow-carried to the autoclave where their precipitation and deposition on heated SG tubes led to tubes fouling. To reproduce surface characteristics of SG tubes surface, a static oxidation step was first performed in FORTRAND autoclave and result in the formation of a fully covering passive layer on the SG tubes surface.Then in-situ fouling test was done by recirculation in FORTRAND test loop. The magnetite deposit formed on tubes was composed of a dense layer of small crystals. Second, chemical cleaning processes were applied on fouled substrates and tubes in a specific experimental device ECCLIPS designed for this purpose. SG industrial cleaning processes timing and thermochemical conditions were strictly respected during these operations and lead to the dissolution of most of the fouling deposit. The passive layer was still covering the whole surface of the tube and no variation in its thickness or composition was noticed which could indicate that chemical cleaning have no effect on the SG tubes integrity. Finally, cleaned tubes fouling was performed in FORTRAND in the same experimental conditions as before the cleaning test. It could be concluded that there is no effect of chemical cleaning on the fouling kinetics of SG tubes for a short period as the amount of deposit formed before and after cleaning was identical. Nevertheless, the small crystallite dense layer observed before cleaning was not present on cleaned tubes and the size of crystallites were bigger after cleaning. For a short period, this morphology could result in the formation of a fouling deposit with more porosity. As the increase of deposit porosity can impact the thermal transfer at the SG tube surface, morphology changes, hardly predictible, could be important for the SG thermal performance after chemical cleaning. For a longer period, frequent SG cleaning applications should prevent the densification of the deposit and thus delay performance loss over time
2
Bartlett, Meloney. "Chemical cleaning of fouled membrane systems". Thesis, University of Bath, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285409.
3
Abdullah, Syed Zaki. "Membrane ageing due to chemical cleaning agent". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46862.
Resumen
Sodium hypochlorite is commonly used as a cleaning agent to remove adsorbed foulants from PVDF-based micro/ultra filtration membranes in water and wastewater treatment applications. Although effective for fouling control, extended sodium hypochlorite exposure can affect the physical/chemical characteristics and hinder the treatment performance of these membranes. In the present study, experiments were conducted to comprehensively quantify the effects of sodium hypochlorite exposure on changes in the physical/chemical characteristics and the filtration performances of blended PVDF-based supported hollow-fiber membranes and identifying the mechanism(s) responsible for the changes. Both the effect of the sodium hypochlorite concentration (C) and the duration of exposure (t) on the membrane characteristics are investigated. The physical/chemical characteristics and the filtration performances of virgin and aged (i.e., weathered due to exposure to sodium hypochlorite) membranes were compared. The membranes were characterized based on chemical composition (FTIR and NMR), mechanical strength (yield strength), surface hydrophilicity (contact angle), pore size and porosity (scanning electron microscopy and challenge test), membrane resistance (clean water permeation test), and affinity of the membrane for foulants (cleaning efficiency). The results indicated that exposure dose and concentration of the sodium hypochlorite used have a significant influence on the membrane characteristics. For the exposure conditions considered, the impact of sodium hypochlorite exposure on the parameters investigated could be most accurately and consistently correlated to an exposure dose relationship of the form Cnt (where, C=concentration and t=exposure time) rather than the Ct relationship commonly used to define the extent of exposure to cleaning agents. For all the parameters investigated, the power coefficient n was less than 1 indicating that time had a greater impact on the changes than did the concentration of the sodium hypochlorite. The results suggest that the use of sodium hypochlorite for chemical cleaning, at concentrations that are higher than those typically used for chemical cleaning would have less of an effect on the characteristics of the membrane materials. Changes in the characteristics were attributed to the oxidation of the hydrophilic additives (HA) present in blended PVDF membranes. A new non-destructive membrane characterization technique to evaluate the amount of membrane ageing is proposed.
4
Shorrock, Chris. "Membrane cleaning : cleaning-in-place of a microfiltration membrane fouled during yeast harvesting". Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285410.
5
Bird, Michael Roger. "Cleaning of food process plant". Thesis, University of Cambridge, 1993. https://www.repository.cam.ac.uk/handle/1810/251541.
6
Porcelli, Nicandro. "Chemical cleaning of potable microfiltration and ultrafiltration membranes". Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4659.
Resumen
Concerns over possible waterborne disease forced drinking water supply companies in England and Wales to adopt microfiltration and ultrafiltration technologies rapidly. MF and UF membrane plants are designed to produce water of a consistent quality regardless of throughput and fluctuations in the feedwater quality. To operate well they need to maintain flux and balance the rate of fouling, and chemical cleaning performance is critical to this. Giant steps have been taken into characterizing the foulants scientifically in the last few years while cleaning is reactive and ad hoc. This thesis explores the basis for a corresponding cleaning science for the technology to develop quantitively. Cleaning performance was defined in terms of a response to combinations of explanatory variables in a materials limited cleaning envelope. The study focused on applying variations of cleanant concentration, applied temperature and soak times to a variety of membranes fouled with different waters and regimes. An experimental design was developed and applied consistently to a number of different sampled sites; allowing an optimised recovery from the polynomial expressions for each treatment, through factorial analysis of the data. The size and variety of the data set analysed allowed comparison and quantification of the different deviations from optimal cleaning response. This effect was seen to vary temporally and with operating regime and the methods usefulness as a practical tool in the membrane plant lifecycle was considered. Cost evaluation of the variation in cleaning response showed that sub-optimal cleaning costs and energy use may be significant and the thesis also illustrated how module geometry affects initial cake deposition and thus cleanability. By demonstrating the potential for cleaning factor analysis, the potential for a combined heuristic and predictive cleaning control science is possible, but will need new strategies to manage technology change.
7
Moitsheki, Lesego Johannes. "Nanofiltration : fouling and chemical cleaning / Lesego Johannes Moitsheki". Thesis, North-West University, 2003. http://hdl.handle.net/10394/391.
Resumen
The challenge of providing developing rural areas in South Africa with
sufficient potable water is substantial. North West Province, among others, is
water-stressed, semi-arid, and largely rural with a high dependence on
groundwater as a strategic resource. Some parts of the province are having
poor water quality which ends up affecting households, farming and livestock.
The aim of this study is to evaluate the performance of nanofiltration (NF)
membranes in detrimental ion (fluoride, nitrate and sulphate) rejection and to
monitor fouling on membranes with their subsequent chemical cleaning.
Five commercial membranes (D12, D11, CTC1, NF90 and NF70) were
characterized using scanning electron microscopy (SEM), single salt
retentions and clean water permeation studies. The three-layered structure of
the membranes was observed using SEM, viz.: smooth dense layer, loosely
networked sublayer and the support. 012, D11 and CTC1 showed higher
water flux than NF90 and NF70. Membranes showed more retention of
divalent ions than of monovalent ions. All tested membranes showed a
negative surface charge density.
During treatment of sampled rural water, all the membranes tested (D12, D11,
CTC1, NF90 and NF70) gave different ion retention results and were mostly
influenced by water composition. All tested membranes satisfactorily rejected
sulphate. NF70 effectively rejected all the ions of interest (fluoride, nitrate and
sulphate) from rural water, indicating that NF70 behaves more like a reverse
osmosis (RO) than an NF-membrane.
During fouling experiments, it was found that salts crystallize on the
membrane surface, thus decreasing the membrane performance. Cake
formation was observed on the membranes fouled with rural water. During
chemical cleaning, acid was not an effective cleaning agent. Alkali and
surfactant solutions separately proved to be moderate cleaning agents (flux
recovery ranged from 50% to 75%) while their combination (alkali and
surfactant) gave the best results (100% flux recovery)Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2004.
8
Pérez, Mohedano Raúl. "Cleaning principles in automatic dishwashers". Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6590/.
Resumen
Cleaning inside automatic dishwashers (ADWs) represents an example of a ‘black box’ problem. The description of the phenomena occurring during a typical wash cycle is not currently well known. This thesis aims to illustrate and expand the in-depth knowledge required to better understand the wash process by analysing the different mechanical and chemical factors involved as well as the interactions between them. Online measurements techniques (Positron Emission Particle Tracking, scanning Fluid Dynamic Gauge or Image Analysis) were combined with statistical and numerical modelling to investigate the evolution over time of the cleaning system.
9
Lawing, Andrew S. (Andrew Scott). "Gas-phase cleaning of silicon wafer surfaces". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/38852.
10
Goode, Kylee Rebecca. "Characterising the cleaning behaviour of brewery foulants, to minimise the cost of cleaning in place operations". Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3908/.
Resumen
Industry operations require a clean plant to make safe, quality products consistently. As well as product quality, the environmental impact of processes has become increasingly important to industry and consumers. Cleaning In Place (CIP) is the ubiquitous method used to ensure plant cleanliness and hygiene. It is therefore vital the system is optimal and efficient. I.e. the correct cleaning agent is delivered to the fouled surface at the right time, temperature, flow rate and concentration. This cannot be assured without effective online measurement technologies. Fryer and Asteriadou (2009) describe how the nature of a fouling deposit can be related to the cost of cleaning. The evolution of three key deposit types has also enabled current fouling and cleaning literature to be easily classified. In the brewery there are many types of soil that need to be cleaned of which the cost of cleaning was unknown. The cost of fermenter CIP in one brewery was found to be £106 k per year. Effective fouling methods for yeast and caramel; and the relationship between flow, temperature, and caustic concentration in the removal of yeast and caramel soils seen in industry has been done. This work has helped determine effective cleaning methods for these soils from stainless steel coupons and pipes. Fermentation vessels have been found by Goode et al., (2010) to have two types of soil: A – fouling above the beer resulting from the act of fermentation, and B – fouling below the beer resulting from emptying the fermenter. The type B fouling below the beer was found to be a type 1 soil that could be removed with water. An increase in flow velocity and Reynolds number decreased cleaning time. An increase in temperature did not decrease cleaning time significantly at higher flow velocities, 0.5 m s-1. Fouling above the beer occurs when material is transported to and stick on to the wall during fermentation foaming. This happens initially and as a result the fouling has a long aging time. This yeast film represents a type 2 deposit, removed in part by water and in part by chemical. Most of the deposit could be removed by rinsing with warm water. At 50°C the greatest amount of deposit was removed in the shortest time. A visually clean surface could be achieved at all temperatures, 20, 30, 50 and 70°C, using both 2 and 0.2 wt % Advantis 210 (1 and 0.1 wt % NaOH respectively). A visually clean surface was achieved quicker at higher detergent temperatures rather than rinsing at higher flow velocity or concentration. This finding suggests most deposit can be removed with warm water and cleaned with lower detergent concentrations. Currently in the brewery 2 % NaOH is used at 70°C. Caramel represents a type 3 soil. When heated it sticks to stainless steel and requires chemical action for removal. Confectionary caramel was cooked onto pipes and coupons and the effect of flow velocity, temperature and concentration on removal determined. At high flow velocity most of the deposit could be removed from the pipe using water. There was no significant difference in the mass of caramel removed by the water however. A visually clean surface was achieved by rinsing at 80°C with 2.5% Advantis. A visually clean surface could not be achieved at lower temperatures at higher concentration, 5% Advantis, or at higher flow velocity. The measurement of online conductivity and flow rate values was invaluable during each experiment. Turbidity values did indicate the removal of yeast and caramel from pipes however offline measurements were required to confirm removal. Caramel removal could be wholly quantified by mass when cleaning pipes. The integration of the turbidity values measured during each rinse correlated well with the mass of deposit removed in most cases. Coupon cleaning was wholly quantified by area . A cost saving of £69 k can be made by optimising fermenter CIP to warm pre-rinsing followed by ambient caustic circulation. An £8 k saving can be made by optimising yeast tank CIP to pre-rinsing only and acid sanitisation. Industry must ensure effective online CIP measurements are made throughout cleaning to describe the process effectively and enable optimisation. It is crucial to have cleaning measurement information to hand because that is how we ensure our customers they are buying a quality product. Also you cannot optimise what you do not measure effectively.
11
Ng, Dedy. "Nanoparticles removal in post-CMP (Chemical-Mechanical Polishing) cleaning". Thesis, Texas A&M University, 2005. http://hdl.handle.net/1969.1/4159.
Resumen
Research was performed to study the particle adhesion on the wafer surface after the chemical-mechanical polishing (CMP) process. The embedded particles can be abrasive particles from the slurry, debris from pad material, and particles of film being polished. Different methods of particle removal mechanism were investigated in order to find out the most effective technique. In post-CMP cleaning, surfactant was added in the solution. Results were compared with cleaning without surfactant and showed that cleaning was more effective with the combined interaction of the mechanical effort from the brush sweeping and the chemistry of the surfactant in the solution (i.e., tribochemical interaction). Numerical analysis was also performed to predict the particle removal rate with the addition of surfactants. The van der Waals forces present in the wafer-particle interface were calculated in order to find the energy required to remove the particle. Finally, the adhesion process was studied by modeling the van der Waals force as a function of separation distance between the particle and the surface. The successful adaptation of elasticity theory to nanoparticle-surface interaction brought insight into CMP cleaning mechanisms. The model tells us that it is not always the case that as the separation distance is decreased, the attraction force will be increased. The force value estimated can be used for slurry design and CMP process estimation.
12
Mallon, James M. "Floc structure and the improvement of chemical water cleaning". Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324839.
13
Din, Rizwan. "Chemical cleaning of starch based deposits from hard surfaces". Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311234.
14
Weis, Andreas. "Fouling and cleaning synergy in ultrafiltration membrane systems : chemical cleaning after filtration of spent sulphite liquor". Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425883.
15
Stephen, Christopher Mark. "Filtration and cleaning behaviour of rigid ceramic filters". Thesis, University of Surrey, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337002.
16
Han, Yong-Pil 1962. "HF vapor etching and cleaning of silicon wafer surfaces". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/32698.
Resumen
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999.Includes bibliographical references.
The objectives of this project are to understand the reaction mechanisms for oxide etching by both HF/H2 0 and HF/alcohol processes and to develop a vapor phase HF cleaning process to remove metallic contamination and native oxide on a silicon surface. Although the HF vapor process has been studied intensively for past several decades, the commercial application has not been very successful due to the unknown nature of the process. This study, performed at MIT, has emphasized on finding possible applications to the semiconductor industry as a replacement to the aqueous phase cleaning processes. The ultimate purpose of this project is to demonstrate feasibility of the HF vapor process for a vacuum compatible and clustered cleaning process. In this study, the etching experiments were carried out in a stainless steel vacuum chamber connected to a vacuum wafer transfer system. Samples were introduced through a load lock chamber and transferred to the HF vapor reaction chamber. The base pressure of the system was maintained under 10-7 Torr. The system can handle sample sizes between 1 cm square and 10 cm diameter silicon wafers. The etching rates were measured by an in situ ellipsometer installed on the HF vapor reactor. Ellipsometric measurements suggest that oxide etching can occur without a condensed layer or with a condensed layer on the oxide surface. The etching rates of oxide in the condensed regime were very high (3,000-12,000 A/min) compared to the gas phase regime (0-300 A/min). The etching regime in which a condensed layer is formed is a function of not only the partial pressures of HF and H 20 in the feed gas, but also a function of the mass transport of the products from the sample in the gas phase. We have categorized two different etching regimes: the gas phase regime and the condensed phase regime. In the gas phase etching regime, reactant molecules are adsorbed on the oxide surface in sub-monolayer, monolayer, or multilayer films. In the multilayer adsorption regime, the etching rate is usually low (typically 0-400 A/min) and is linearly proportional to the partial pressure of HF and H20. The etching rate in this regime is greatly affected by the temperature of the substrate. The mass transfer rate limits the etch rate of oxide in the multilayer adsorption regime. In the submonolayer or monolayer adsorption regime the etching rate is described by Langmuir- Hinshelwood kinetics. The etching rate is governed by surface kinetics in this regime. Advantages of this etching regime are: 1) smoother etched surface, 2) low selectivity to TEOS, 3) haze-free etched surface, 4) no metal attack, 5) perfect removal of native oxide, and 6) vacuum compatible process. The HF vapor process in this regime is an ideal process for contact cleaning and polymer removal after metal or via etching. Electrostatic charge on the wafer surface affects the etching reaction significantly in the non-condensed regimes. A positively charged surface enhanced the etching reaction in the submonolayer and monolayer etching regimes. Direct ionization of HF on the oxide surface is responsible for the enhancement in this regime. A negatively charged surface mainly enhanced the etching in the multilayer regime. A thicker multilayer, induced by the formation of fluorosilicate, is responsible for the etching enhancement in this regime. We have demonstrated a successful removal of sodium from both oxide and silicon surfaces using HF/H2 0, HF/IPA, and HF/H20/SiF4 processes in reduced pressure operation. All experiments were performed in a vacuum environment and in-situ XPS was used to measure the surface concentration of sodium. The sodium contamination on oxide surface was successfully removed by both HF/H 20 and HF/IPA processes. The HF/H 20 process could not remove all of sodium contamination on a silicon surface. The addition of SiF4 in the HF/H 20 process greatly enhances the cleaning effect, reducing Na contamination below the detection limit of our XPS, even on a silicon surface. Based on our study, we have reported a true gas phase and vacuum compatible HF vapor process, operated in the monolayer adsorption regime at elevated temperature. A successful removal of RIE residue was performed with a combined cleaning procedure of HF vapor and ashing process. This combined process is a perfect dry cleaning process for contact cleaning method. This process sequence is ideal for a vacuum cluster configuration in which a single wafer is processed at a time and is not exposed in the ambient.
by Yong-Pil Han.
Ph.D.
17
Puspitasari, Vera Liany Chemical Sciences & Engineering Faculty of Engineering UNSW. "Membrane cleaning and ageing effect by chemical and enzymatic agents". Awarded by:University of New South Wales. Chemical Sciences & Engineering, 2009. http://handle.unsw.edu.au/1959.4/43731.
Resumen
MBR suppliers are largely recommending NaOCl as the cleaning agent. Despite the popularity of this chemical for membrane cleaning, there is a lack of publications regarding NaOCl optimum cleaning conditions. To properly conduct this optimization study (i.e. obtain the required level of reproducibility and confidence), a rigorous methodology is still required. The potential effect of NaOCl on polymeric materials ageing has drawn attention and recent studies have been dedicated to assess the impact of its exposure on numerous membrane materials (except polyvinylidene fluoride (PVDF)). PVDF and polypropylene (PP) hollow fibers were investigated using unwashed yeast as model fouling solution, while mixture of sodium alginate and bovine serum albumin (BSA) acted as feed solution for PVDF flat sheet. The cleaning efficiency and optimum NaOCl concentration were found to vary between the different membrane materials and between single and cyclical cleanings. During cyclical cleaning, foulant was more difficult to remove. When 2% NaOCl was used, Fourier Transform Infra Red (FTIR) Spectroscopy showed a change in membrane function groups on PVDF flat sheet, indicating ageing occurrence. NaOCl agemg caused changes in membrane properties. PP hollow fibers became more brittle with 60 % elongation decrease after 13 weeks. PVDF flat sheet membrane exhibited two-steps-degradation mechanism; firstly, the removal of its surface modification substance, and secondly, the increase of its hydrophilicity. These results were confirmed by X-ray Photoelectron Spectroscopy (XPS), FTIR Spectroscopy, contact angle and hydraulic measurement. Enzyme is an alternative option for membrane cleaning. However, the enzymatic cleaning study did not present encouraging results. Optimum cleaning efficiency for protease (68%) and amylase (73%) were found to be lower compared to NaOCl cleaning (95%). Lowry and Dubois methods found that residual foulants were present on the membrane after the cleaning process, which caused fouling to occur faster when membrane was re-used.
18
Ul, Hai Irfan. "Bubbling fluidized bed biomass gasification and product gas cleaning". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43678/.
Resumen
Biomass is used for fuel by humanity from prehistoric times. With the passage of time and to meet the energy needs, non-conventional ways of utilizing the conventional sources became an interest with use of technologies. Biomass gasification is a proven technology that can economically use alternative energy resource of “Carbon Neutral”. Biomass product gas from biomass gasification is composed of CO, CO2, CH4, H2, other hydrocarbons, traces of other components and tar from biomass gasification. Fluidized bed gasification is one of the promising technologies to achieve high thermal conversion efficiency as it takes great advantages of fluidization in terms of uniform temperature profiles and excellent gas-solid interactions. The present research is aimed to evaluate the performance of a bubbling fluidized bed biomass gasifier for product gas production composition using air as gasification agent and SRC willow chips as biomass. Particle capture efficiency of the mop fan and an effect of different operating conditions such as bed temperature, equivalent ratio on the product gas composition and heating value are also investigated at Institute of Sustainable Energy Technology, University of Nottingham. The concentrations of particulate matter in the product gas before and after the mop fan cleaning unit are measured to assess the performance of the cleaning unit. Different fan rotating speeds and different flow rates of spray water are used to optimise the particle removal efficiency of this unit. It has been found that the mop fan cleaning unit has achieved an efficiency of 90% in removing particle matters and an efficiency of more than 80% in removing N-species presented in the product gas. Tars appear as a major issue in the product gas and should be removed from the product gas before they get condensed in the equipments which utilise product gas. Tar arrest techniques were successfully tested in this investigation such as woodchips bed, water spray and mop fan. The synergic effect of tar removal of water spray and mop fan found to be more effective in removing tars as if used individually. Different spray water amounts were used with a constant fan speed for keen observation of tars’ solubility in the water and found reasonable removal of tars from product gas.
19
MacDonald, John. "The effects of commercial chemical cleaning processes on sandstones in Scotland". Thesis, Robert Gordon University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386363.
20
Kent, Anthony Clifford. "The mechanics of abrasion relating to household cleaning". Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6954/.
Resumen
Abrasion of polymer surface films or coatings in an everyday occurrence, whether in the home, work or industry. As a result a wide variety of polymer films can be found on surfaces. Despite the numerous applications, three body thin film abrasion appears a niche area of study and as a result under-researched. This investigation focuses on identifying, characterising and quantifying the abrasive wear of a baked dehydrated castor oil deposit formed on stainless steel. The primary aim of this project is to understand how the fundamental properties of the liquid abrasive cleaning system contribute to the material removal. Investigations have primarily been carried out using a reciprocating linear tribometer for the cleaning and a profilometer to measure the wear. The wear of the baked oil film was found to largely follow the established Archard wear equation of sliding distance and load, despite the fact it was derived to describe two body and not three body wear. However the wear rate was not inversely proportional to hardness and there were significant effects when parameters not in the Archard equation are considered. IN particular changing the speed, viscosity, particle size and distribution all had an impact on the wear.
21
An, Ju Jin. "Study of surface kinetics in PECVD chamber cleaning using remote plasma source". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43204.
Resumen
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2008.Includes bibliographical references (p. 132-136).
The scope of this research work is to characterize the Transformer Coupled Toroidal Plasma (TCTP); to understand gas phase reactions and surface reactions of neutrals in the cleaning chamber by analyzing the concentration of neutrals in downstream cleaning process chamber; and to make a global model that predicts the partial pressure of active species in the cleaning chamber. The final goal is to set-up an optimal cleaning process using the results from the experiment and the global model. The first object is to characterize the TCTP and the power consumed by plasma is measured as one approach to the characterization of plasma. MKS Astex plasma source has a very high power density. Compared to a typical industrial plasma source, the power density of the TCTP source is two orders of magnitude higher. The extremely high power density makes the plasma source very unique and its parameters very different from other plasma sources. It is discussed that there are several factors that affect the plasma power consumption. One factor is the flow rate of inlet gas and the elevated pressure due to the high flow rate of inlet gas increases the power consumption. Experimentally it is observed that the plasma power is linearly dependent upon the plasma source pressure, not upon the process chamber pressure. Another factor of controlling the power consumption is the resistivity of gases. For example, the bonding energy of N-F in NF3 gas is different from the bonding energy of C-F bonding in C2F6. Experimental result shows that C2F6 + 02 gas requires more power than NF3 gas to dissociate in the plasma due to the different resistivity. The second object is to understand gas phase reactions and surface reactions among neutrals in the cleaning chamber. The effect of nitric oxide as a silicon nitride etching enhancement factor is discussed.
(cont.) It is shown that only 4.5% of additives (02, CO and CO2) into NF3 discharge doubles nitride etching rate and the enhancement of etching rate occurs regardless of the additive types. The enhancement results from the production of NO in the discharge of NF3 gas mixture. As the amount of oxygen containing additive increases, the amount of NO increases. However, atomic fluorine decreases as the amount of oxygen containing additive increases because the additive dilutes NF3 plasma. At low process chamber pressure, the effect of NO is offset by the dilution effect of atomic fluorine. At high pressure, addition of oxygen enhances the recombination of atomic fluorine and 25% of 02 in NF3 discharge decreases 54% of atomic fluorine. Therefore, the effect of a decrease in atomic fluorine is remarkably higher than the effect of increase in the concentration of NO by adding 02 at high pressure, which leads to a decrease of nitride etching rate at 5torr. Also, the nitride etching rates of NF3 plasma and NF3/C2F/O2 plasma are compared and it is shown that NF3/C2F/O02 plasma brings better performance than NF3 plasma in increasing the nitride etching rate. The main reason why the nitride etching rate of NF3/C2F6/02 plasma is higher than that of NF3 plasma is because nitric oxide is formed in the gas phase of NF3/C2FdO2 plasma and the nitric oxide reacts with the nitrogen atom on the silicon nitride surface producing N20 or N2, while nitrogen is substituted by oxygen on the surface by the reaction. Removing nitrogen atom from silicon nitride substrate is assumed to be the rate-limiting step in the fluorine base etching of silicon nitride film. In summary, the nitric oxide makes it easier to remove the nitrogen atom from silicon nitride surface in the presence of atomic fluorine, which is the rate-limiting step for nitride etching with F base gas, therefore enhancing silicon nitride etching rate. The last object is to make a global model to predict the partial pressure of neutrals in downstream.
(cont.) It is shown that incorporating kinetics into the global modeling of PECVD chamber cleaning system successfully enables the prediction of the partial pressure of atomic fluorine in NF3/N2 and NF3/02 discharge, which is crucial in estimating cleaning rate of TEOS film. First of all, effect of nitrogen addition in NF3 discharge is experimentally investigated by measuring the etching rates of TEOS film and the partial pressure of neutral species. Both modeling results and experimental results make a good agreement that the addition of nitrogen in NF3 has advantage in increasing TEOS etching rate at high chamber pressure. In other words, at high chamber pressure, TEOS etching rate is increased by adding nitrogen in NF3 plasma. Then, the effect of oxygen in NF3 discharge is studied. TEOS film etching rates and partial pressure of atomic fluorine in the gas phase shows that adding oxygen in NF3 discharge increases F-F recombination, which lowers TEOS etching rate. By incorporating the above kinetics information in the global model, the partial pressure of neutral species in NF3/02 discharge is successfully predicted by the global model.
by Ju Jin An.
Ph.D.
22
Alharthi, Majed. "Fouling and cleaning studies of protein fouling at pasteurisation temperatures". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4892/.
Resumen
Fouling and cleaning processes impact industrial production, in terms of economics, product quality, product safety, and plant efficiency. Therefore, optimisation of fouling and cleaning processes is a significant issue, and needs a good understanding of fouling and cleaning kinetics. Ideal monitors should determine the right time when a process run should stop and when a plant will be clean in order to improve the process efficiency. This thesis investigated the fouling and cleaning behaviour of dairy fluids in a plate heat exchanger (PHE) and bench scale fouling rig, using whey protein concentrate (WPC) and WPC-/m (with added minerals) as fluid models. Fouling and cleaning monitoring methods were also investigated as new ways to operate and control the processes. Experiments displayed that fouling increased with increasing protein concentration up to a limit of approx. β-Lg 0.3 wt. %. Increasing the flow rate from 100 to 150 l/h decreased the Δ(ΔP) fouling rate for β-Lg concentrations of 0.1, 0.3 and 0.5wt.% by 34, 70 and 72.7%, respectively, due to the increasing of shear stresses at the heat transfer surface. Adding minerals to WPC has lowered the temperature at which β-Lg begins to denature. The differences in fouling behaviour of WPC and WPCm had an effect on cleaning behaviour. Increasing the mineral content in WPC deposits leads to cleaning behaviour which differs completely from that of proteinaceous deposit as no pressure peak is observed.
23
Benjamin, Michael L. "Cleaning Product Chemical Exposures Measured in a Simulated Home Healthcare Work Environment". University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1573224213774289.
24
Reza, Humayun. "Cleaning and restoring old masonry buildings : investigations of physical and chemical characteristics of masonry stones and clay bricks during cleaning". Thesis, Edinburgh Napier University, 2014. http://researchrepository.napier.ac.uk/Output/8851.
Resumen
Historic buildings and monuments are a precious finite asset and powerful reminders for future generations of the work and way of life of earlier cultures and civilisations. The stone cleaning and restoration of historic buildings is a crucial element in keeping the good look, integrity and quality of the fine art, method of construction and architecture of previous civilisations. Stone cleaning is one of the most noticeable changes a building can be subjected to, which changes its appearance, persona and environmental context. In this study, a series of physical and chemical tests were conducted to further investigate, evaluate and improve the efficiency of building cleaning. Seven different abrasives were adopted for air abrasive cleaning, including copper slag (fine, medium and coarse), recycled glass (fine, medium and coarse) and hazelnut/almond shell (natural abrasive), on a total of eight masonry stones and clay bricks, including yellow sandstone, red sandstone, limestone, marble, granite, white clay brick, yellow clay brick and red clay brick. Physical investigations included sieve tests and impact tests on the abrasives, greyscale image analysis, thickness reduction measurements, Vickers surface hardness tests, Charpy impact tests and water absorption tests. Chemical investigations included Scanning Electron Microscope (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX) analyses. Sieve tests and impact tests confirmed that the abrasives utilised were fairly reliable, and the abrasives with high bulk densities were stronger and tougher than those with low bulk density. Greyscale digital image analysis indicated a lower greyscale value corresponded to a dirtier masonry surface. In general, the greyscale continuously increased with the increasing cleaning time and tended to be stable when the surface became fully cleaned. The cleanness was also introduced for assessing the effectiveness of the building cleaning. Similar trends could be observed. Both parameters proved to be significantly useful. For most of the samples, monotonic increase trends were observed between the greyscale and thickness reduction. The image analysis on greyscale and the thickness measurement were two useful methods for assessing the cleaning degree of a masonry stone or clay brick. Based on the analysis on all the testing data, it is possible to recommend a more suitable abrasive for each masonry stone or brick. For granite and red clay brick, medium glass produced the best performance, while for limestone, marble and red sandstone, fine glass was promising. For yellow clay brick, fine slag could be the best option, while for yellow sandstone the natural abrasive was found to be the most suitable. vi The Vickers hardness test results indicated that a larger hardness corresponded to a harder masonry surface. Also the surface hardness continuously increased with the increasing cleaning time but at a decrease rate. Most of the increasing trends of the surface hardness could be approximately expressed using parabolic relationships. Granite was found to be the hardest, and followed by marble and limestone. However, there were no big differences in the surface hardness between yellow clay brick, yellow sandstone, red sandstone and white clay brick. The impact resistances of seven masonry stones and bricks were obtained by conducting the Charpy impact resistance tests. Granite showed the highest impact resistance among all the stones and bricks and was followed by marble, limestone, clay bricks and sandstones. The stones and bricks with higher impact resistances also had higher hardness values but lower water absorptions. The water absorbing capacity of the seven masonry stones and bricks was quantitatively determined. Two types of clay bricks showed the highest water absorptions, and the water absorptions for limestone, yellow sandstone and red sandstone were also quite high. However, the water absorption of marble and granite was found to be very low. Larger water absorption corresponded to a softer stone or brick, while smaller water absorption corresponded to a harder stone or brick. The chemical investigations by using the SEM and EDX techniques showed that the chemical substances on the masonry surface varied largely for different types of stones and bricks. This study showed the way to detect such soiling using chemical analysis by monitor the changes in chemical elements and compounds during the building cleaning. Finally, comprehensive conclusions were presented, together with useful suggestions for future work.
25
Domingues, Joana Andreia Lameiras. "Spectroscopy studies on conservation issues in modern and contemporary paintings". Master's thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/4480.
Resumen
Dissertation presented to the Faculty of Sciences and Technology of New University
of Lisbon in fulfilment of the requirements for the Master’s degree in Conservation and Restoration Specialization in easel paintingModern and contemporary paintings are one of today’s grand challenges in conservation of cultural heritage. Particularly, these paintings have often been retouched using materials rather similar to originals, thus, compromising the reversibility of the overpainting. In this work, FTIR and Raman spectroscopies, assisted by optical microscopy, were used to evaluate the effectiveness and harmfulness of chemical and laser cleaning methods for the removal of overpaints. Representative mock-ups prepared with commercial paint formulations were used. The laser cleaning experiment was part of an interdisciplinary study which aims the evaluation of method’s limitations by using the most aggressive cleaning parameters. The combined use of FTIR and Raman spectroscopies could identify constituent materials of modern paints, controlling their behaviour under cleaning, while optical microscopy allowed the evaluation on surface morphology. In addition, equivalent portable equipments from MOLAB were covered as a preparation for in situ analysis. Several problems in the selective removal of overpaints were found with chemical cleaning. The laser cleaning showed better efficiency in removing them, although, some alterations occurred upon laser irradiation, for instance, binder degradation with carbon formation and titanium white alteration. The proposed spectroscopic protocol was considered useful for controlling different cleaning methods in modern and contemporary paintings.
26
Palabiyik, Ibrahim. "Investigation of fluid mechanical removal in the cleaning process". Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4593/.
Resumen
The cleaning of pipework from fluids of high viscosity is a significant problem in many food and personal care industries which can cause considerable economic and environmental impact. Three stages are identified in the cleaning of straight pipes; (i) a short core removal stage of product recovery, before water breaks through the filled pipe, (ii) the 1st cleaning stage (film removal stage) when there is a continuous wavy annular film on the wall, and (iii) the 2nd cleaning stage (patch removal stage) in which the material is present as patches on the wall. The product recovery stage is found to influence the overall cleaning process. Conducting product recovery at low temperatures and high flow rates cause the formation of a wavy wall layer which leads to more rapid subsequent removal. A two step CIP protocol is proposed to decrease the environmental impact of cleaning of a viscoelastic material (toothpaste) from pipework. Applying cold water in the 1st cleaning stage and hot water in the 2nd cleaning stage results in 40 % energy saving without affecting the cleaning performance significantly compared to traditional CIP protocols used in plants. Yield stress of deposits is the key effect on the cleaning of deposits. A new dimensionless number is explored. It is physically a ratio of flow energy to the yield stress of a deposit. It has collapsed cleaning time data onto a one curve for different deposits cleaned at different velocities. It can be used to predict cleaning times of deposits or identify the governing cleaning mechanisms in cleaning. It is found that the magnitude of pressure loss in flow can be used to quantify the flow and turbulence effect on cleaning and scale up lab scale data. The results show that although fluid mechanical removal is a complex process, cleaning time of deposits can be predicted by knowing its rheology and fluid mechanical parameters of cleaning fluid.
27
Macháček, Martin. "Měření doby života nosičů proudu ve strukturách křemíkových solárních článků". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217834.
Resumen
This thesis deals with a lifetime measurement of current carriers in silicon solar cell structures. In the first chapter there is a description of several recombination models and their participation at a final effective lifetime value. By using these recombination models in a computer simulation it is possible to receive approximate evaluation of some important silicon solar cell structure parameters. The PC1D simulation program was used for this thesis. For the lifetime measurement of real test-wafers two methods were used: QSSPC (quasi-steady-state photoconductance) and MW-PCD (microwave photoconductance decay). There is a detail description of these methods, used measurements machines and differences between both of them in the chapter four. The main objective of the thesis is mentioned in the last chapter, which is mainly focused on a chemical passivation of silicon wafers and deals with a problem of post-passivation wafer cleaning. There are three passivation techniques mentioned: the iodine in ethanol solution, the iodine and polymer in ethanol solution and the quinhydron in methanol solution. In two cases a results, that are adequate to return the tested wafers in the manufacture process, were achieved.
28
Novak, Maria L. "Optimal Strategy to Develop Cleaning Procedures for Filling Machines Equipped with Clean-in-Place (CIP) Technology". University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613747962470201.
29
Dieudonne, Vincent. "Chemical and Electrochemical Coal Cleaning in acidic medium application and analysis of the process". Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43846.
30
Cole, Pamela Anne. "Cleaning of toothpaste from process equipment by fluid flow at laboratory and pilot scales". Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4128/.
Resumen
Cleaning studies were performed to remove toothpaste by fluid flow at different temperatures and velocities to mimic CIP (Cleaning-In-Place) processes on toothpaste coated coupons at laboratory scale and fully filled pipeline at pilot scale (different lengths and diameters). The cleaning time was reduced by increasing the velocity and temperature of the water, however no further time benefit was seen above 40°C. The adhesive force for different pastes calculated from micromanipulation data followed the same trend as cleaning times on the laboratory cleaning rig. This cleaning data for the different paste formulations had a logarithmic relationship with the viscosity term from the Herschel-Bulkley rheological model. Removal of toothpaste from pipes occurred by the core of the paste being removed from the centre of the pipe to leave a thin coating on the pipe wall, which was then eroded by flow. Pipes of lengths between 0.3 m and 2 m (47.7 mm diameter pipe) showed no difference in cleaning time. The rate limiting process was removal of the thin wall coating and therefore not a function of length. An inverse wall shear stress relationship with cleaning time was found to represent all the data, at all scales and under all conditions.
31
Stefanov, Bozhidar. "Photocatalytic TiO2 thin films for air cleaning : Effect of facet orientation, chemical functionalization, and reaction conditions". Doctoral thesis, Uppsala universitet, Fasta tillståndets fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-265056.
Resumen
Poor indoor air quality is a source of adverse health effects. TiO2 coatings deposited on well-illuminated surfaces, such as window panes, can be used to fully mineralize indoor air pollutants by photocatalysis. In such applications it is important to ensure stable photocatalytic activity for a wide range of operating conditions, such as relative humidity and temperature, and to avoid deactivation of the catalyst. In this thesis photocatalytic removal of the indoor-pollutant acetaldehyde (CH3CHO) on nanostructured TiO2 films is investigated, and in particular it is proposed how such films can be modified and operated for maximum performance. Catalyst deactivation can be reduced by purposefully changing the surface acidity of TiO2 by covalently attaching SO4 to the surface. Moreover, the overall photocatalytic activity on anatase TiO2 films can be improved by increasing the fraction of exposed reactive {001} surfaces, which otherwise are dominated by {101} surfaces. In the first part of the thesis mode-resolved in-situ FTIR is used to elucidate the reaction kinetics of CH3CHO adsorption and photo-oxidation on the TiO2 and SO4 – modified TiO2 surfaces. Surface concentrations of main products and corresponding reaction rates were determined. Formate is the major reaction product, whose further oxidation limits the complete oxidation to gaseous species, and is responsible for photocatalyst deactivation by site inhibition. The oxidation reaction is characterized by two reaction pathways, which are associated with two types of surface reaction sites. On the sulfate modified TiO2 catalyst fewer intermediates are accumulated, and this catalyst resists deactivation much better than pure TiO2. A hitherto unknown intermediate – surface-bound acetaldehyde dimer with an adsorption band at 1643 cm−1 was discovered, using interplay between FTIR spectroscopy and DFT calculations. The second part of the thesis treats the effect of increasing the relative abundance of exposed {001} facets on the photocatalytic activity of anatase TiO2 films prepared by DC magnetron sputtering. A positive effect was observed both for liquid-phase photo-oxidation of methylene blue, and for gas-phase photocatalytic removal of CH3CHO. In both cases it was found that the exposed {001} surfaces were an order of magnitude more reactive, compared to the {101} ones. Furthermore, it was found that the reactive films were more resilient towards deactivation, and exhibited almost unchanged activity under varying reaction conditions. Finally, a synergetic effect of SO4 – modification and high fraction of exposed {001} surfaces was found, yielding photocatalysts with sustained high activity. The results presented here for facet controlled and chemically modified TiO2 films are of interest for applications in the built environment for indoor air purification and as self-cleaning surfaces.GRINDOOR
32
Emmerich, Jodi. "Cost analysis on the use of chamber cleaning agents nitrogen trifluoride and chlorine trifluoride in the semiconductor industry". Online version, 1999. http://www.uwstout.edu/lib/thesis/1999/1999emmerichj.pdf.
33
Lütkenhaus, Davidson. "Engineering understanding of cleaning : effect of chemistry and mechanical forces on soil removal". Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7929/.
Resumen
The cleaning of food-based soils is highly relevant in domestic and industrial environments due to the costs associated with these operations as well as the significant consumption of time, water, and energy. Understanding the relationship between chemical and mechanical forces required to clean a surface is a critical step towards optimizing these processes. A complex twophase polymerized grease was developed and characterized with respect to its morphology, component distribution, and chemical composition. A thorough evaluation and physicochemical characterization of the cleaning process of this complex soil from a hard substrate was performed at two different length scales. Results showed that surfactants are more effective at weakening the cohesive interactions within the soil matrix and less effective in removing the adhesive bonds at the soil-substrate interface. A statistical model for cleaning efficiency was developed which described cleaning as a function of chemical and mechanical contributions. The effect of the chemistry on hydration and final cleaning performance was investigated through a definitive model screening and correlated to the tribological forces involved in the process. The model was shown to be applicable to several industrially relevant surfactant systems and revealed that hydration is the main factor driving cleaning of this two-phase soil.
34
Peng, Hui. "The treatment of bilge water using a MF/UF hybrid membrane system: Membrane fouling, cleaning and the effect of constituents on flux decline". Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6110.
Resumen
Bilge water accumulates in recesses and bilges onboard ships. Depending on the type of design and age, ships can generate large volumes of bilge water. This wastewater is a mixture of fresh water and seawater containing various contaminants. Typical contaminants may include fuels, oils, greases, detergents, solvents, rusts, paints, insulation material and a wide variety of other substances. Bilge water is a very challenging wastewater to treat due to large variations in production rates and the complex nature of the wastes in solution. Membrane based Oily Water Separators (OWS) are being increasingly used throughout the world for the treatment of oily wastewater. This work focused on two areas of study: (1) Effects of selected components found in bilge water on membrane performance, and (2) Pilot scale testing using a Microfiltration/Ultrafiltration (MF/UF) hybrid system. The studies are aimed at determining suitable membrane materials and optimum operating conditions such as trans-membrane pressure (TMP) and backflushing for permeate flux enhancement. (Abstract shortened by UMI.)
35
Young, Maureen Elinor. "Biological growths and their relationship to the physical and chemical characteristics of sandstones before and after cleaning". Thesis, Robert Gordon University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336619.
36
Han, Zhenxing. "Particle Removal and Feature Damage Reduction Using Carbonated Ammonia Solutions for Enhanced Megasonic Cleaning Processes". Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/306364.
Resumen
In integrated circuit (IC) manufacturing, particulate contamination from hundreds of processe steps is a major cause of yield loss. The removal of particles is typically achieved through liquid chemical formulations aided by a sound field in the MHz frequency range. When liquid is irradiated with megasonic waves, dissolved gases play an important role in particle removal and feature damage. To take the advantage of the beneficial effect of CO₂ (aq.), this thesis describes the development and optimization of a megasonic cleaning process using a chemical system containing NH₄OH and NH₄HCO₃ at an alkaline pH in which a specific amount of aqueous CO₂ can be maintained to minimize feature damage. In addition, certain etching effects at a slightly alkaline pH were supported for achieving high particle removal. Sonoluminescence (SL) data were collected from these cleaning solutions and correlated with the cleaning performance. The intensity of SL is believed to be a sensitive indicator of transient cavitation during megasonic irradiation, which is thought to be responsible for fragile feature damage. To further analyze the SL signal with respect to the emission from hydroxyl radicals, single-band filters were used to collect the SL signal in different wavelength ranges. The study of particle removal and feature damage was performed using a single-wafer cleaning tool, MegPie® (ProSys, Inc.), which provided acoustic irradiation at a frequency of 0.925 MHz. Commercially available SiO₂ slurry with 200 ± 20 nm particles was used for particle contamination. Particle removal was investigated on both blanket SiO₂ samples and patterned samples. Feature damage studies were conducted on patterned samples by examining the number of line breakages per unit area. By adjusting the pH in NH₄OH/NH₄HCO₃ solutions from 7.8 to 8.5, the amount of CO₂ (aq.) was varied. At a pH of 8.2 with ~ 320 ppm CO₂ (aq.) in the cleaning solution, a high particle removal efficiency was achieved (> 90%) at an acoustic power intensity of 1 W/cm² for an exposure time of 60 s, and the feature damage was reduced by > 50%. For SL signal analysis, band filters in the wavelength range of (i) 280 – 305.5 nm, (ii) 300 – 340 nm, (iii) 335 – 375 nm, and (iv) 374.5 – 397.5 nm were used to resolve the SL spectrum in these wavelength ranges. The filters were sandwiched, one at a time, between the optical window and the photomultiplier tube (PMT) in the Cavitation Threshold (CT) cell. Air-, Ar-, and CO₂-containing DI water (at pH 4.53 with ~ 90 ppm aqueous CO₂) was pumped through the cell at a flow rate of 130 ml/min. The acoustic power was ramped from 0.1 to 4 W/cm² at an acoustic frequency of 0.925 MHz. The SL signal intensity showed the highest value in the ranges of 300 – 340 and 335 – 375 nm in air- and Ar-saturated DI water, which is due to the emission from excited hydroxyl radicals. These results are consistent with an SL spectrum analysis performed using expensive optical set-ups. In CO₂-containing DI water, the SL signal intensity was suppressed by a factor of 100. The methodology reported in this work is simple, inexpensive, and capable of capturing SL spectral features due to hydroxyl radicals.
37
Gilabert, Oriol Guillem. "Optimization of ultrafiltration membrane cleaning processes. Pretreatment for reverse osmosis in seawater desalination plants". Doctoral thesis, Universitat Rovira i Virgili, 2013. http://hdl.handle.net/10803/108954.
Resumen
Esta tesis explica com mejorar la eficiencia del proceso de ultrafiltración en la desalinización de agua de mar. Esto se consigue optimizando diferentes procesos de limpieza como los contralavados y las limpiezas químicas mejoradas. Para conseguirlo se siguen diferentes estrategias como reducir el número de pasos de los contralavados, reducir la frecuencia de los contralavados, usar salmorra proveniente del concentrado de osmosis y reducir el consumo de químicos. Se propone una nueva metodología para analizar los ciclos de limpieza mediante la modelización del proceso. Diferentes tipos de fibra son analizados mediante su permeabilidad y tolerancia a la suciedad. Se presenta una nueva metodología para prevenir la cloración de las membranas de osmosis inversa causadas por las limpiezas químicas mejoradas que se llevan a cabo aguas arriba. Todos los descubrimientos son validados con datos obtenidos de plantas reales. Estas mejoras aumentan la eficiencia del proceso hasta al 98% y reducen el coste de operación de la ultrafiltración en un 7%.This thesis gives an overview on how to improve efficiency of the ultrafiltration filtration process in seawater desalination. This is achieved by optimizing different cleaning processes such as the backwash and the chemical enhanced backwash. Key success factors rely on reducing the number of backwash steps, improving the backwash frequency, using reverse osmosis brine for backwashing and reducing the chemical consumption. A new methodology to analyze these cleanings cycles is proposed through modeling the process. Different fibers types are also analyzed according to its permeability and its fouling tolerance. A methodology to prevent reverse osmosis chlorination from upstream chemical enhanced backwash cleaning is presented. All the findings are validated through real plant operating data. The proposed improvements increase the process efficiency to 98% and lead to a 7% cost reduction in the ultrafiltration process.
38
Van, Dyke Stephanie A. "An analysis of chlorine trifluoride as an effective substitute for nitrogen triflouride in the chemical vapor deposition reactor cleaning process". Online version, 1998. http://www.uwstout.edu/lib/thesis/1998/1998vandykes.pdf.
39
Frýba, Lukáš. "Analýza alternativ odstraňování PCDD/F při spalování odpadů". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229471.
Resumen
The thesis is focused on analyzing the current status of the technology used for cleaning flue gas from persistent organic pollutants, especially PCDD/F. For the three most commonly used methods of solution operational and energy efficiency comparison was made, where achievable energy export and the impact of the change in working conditions on the efficiency indicators of energy production and use of the energy was evaluated. In conditions we considered an alternative machine-technological solutions used for the final disposal of persistent organic pollutants resulting from the waste combustion in terms of additional operating costs and energy efficiency.
40
Peck, Oliver. "An investigation into the strength and thickness of biofouling deposits to optimise chemical, water and energy use in industrial process cleaning". Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.723340.
Resumen
Biofouling is both a human health hazard and detrimental to process efficiency. Biofilm growth is inevitable on exposed surfaces, so an informed approach to cleaning and timely management are essential. Chemicals can readily kill cells, but the biofilm structure must be removed to prevent re-growth and maintain sterility. Chemical agents also pose health and environmental risks, but the typical alternative is to pump unsustainable volumes of cleaning solution through pipelines for mechanical cleaning. The aim of this research was to apply green cleaning principles to biofouling removal in industry, reducing the amount of chemicals, water and energy used in cleaning. Biofilms of Escherichia coli and Burkholderia cepacia were grown on polyethylene, glass and stainless steel 304, in single and mixed species cultures. Fluid dynamic gauging (FDG) utilises hydrodynamics to measure both the thickness and attached strength of the biofilms and therefore the optimum water usage for removal can be estimated, and is both relatively simple and inexpensive to operate. As well as using a static culture method, a drip flow reactor was built to develop biofilms under flow conditions. The use of FDG offers an original way of monitoring both the attachment strength and thickness of mixed species biofilms, and drip flow is an alternative to traditional biofilm growth methods for analysis of removal behaviours, with particular relevance to food production environments. The adhesive and cohesive strengths of both single and mixed species biofilms increased up to 14 days’ growth, and as previous studies suggest that this will be sustained over longer periods under flow conditions, cleaning prior to peak strength would be prudent – at later stages the risk of pathogens developing and contaminating the process would likely become too great, particularly if the biofilm is experiencing significant detachment which increasingly occurs with age. The development of greater, sustained thickness over time can also pose problems with heat transfer and enhanced pressure drop. Protein, a key component of the extracellular matrix, showed a strong correlation with the adhesive strength of mixed species biofilms. Biofilms grown on polyethylene attached more strongly in the early stages of growth than those on glass or steel, which may be due to the greater hydrophobicity of the surface. Chemicals can be used most effectively to weaken the outer layers, and sodium hypochlorite was also shown to be useful for weakening surface adhesion – the required shear stress for 95% removal was reduced by approximately 60% for 5 and 10-day old biofilms. There are more risks associated with chlorine-based disinfectants than the alternative, peracetic acid, although finding a suitable low concentration would be simple using this method. There is no simple solution, complicated further by the unpredictability of the species present in industrial biofouling. The best way of minimising the risk of spoiling and contamination would be to clean surfaces with regularity, in the region of every 5 days rather than after a more prolonged period, which would also serve to minimise the resources used by preventing biofilms from becoming too strongly attached or too thick. A chemical input would need to be determined by testing for the optimum concentration necessary for a suitable effect, thus eliminating excess use, and thereby reducing water and energy use in the process. Taking a multispecies sample from a process flow could offer a more realistic approximation of industrial biofilms. Surface coatings to prevent adhesion are the focus of much research, and could be an alternative to reactive methods.
41
Gupta, Apoorv. "Vätgaslagring, -distribution och -rening". Thesis, KTH, Skolan för kemivetenskap (CHE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-213674.
Resumen
Rising greenhouse gas (GHG) emissions is a major cause of concern today. The primary source of energy all over the globe is fossil fuels, a non-renewable source of energy that is expected to get exhausted in the next 60-100 years. Damage to environment cannot be easily reversed but the initial steps are to reduce the damage done. Other alternative cleaner sources of energy are being looked into as viable options to replace fossil fuels. The objective of this study is to identify options for using hydrogen as an energy carrier in the future with a major focus on the transportation sector. This project is limited to theoretical study looking into the options for hydrogen storage and distribution. Gaseous and liquid hydrogen storage have been looked in to thoroughly and are far from meeting Department of Energy, USA, (DOE) ultimate targets for automobile fleets, hence a shift to other storage options is imminent. Metal hydride storage is believed to be the upcoming technology as the mid-term solution to storage issues and hence is given a lot of attention in this project. On-board storage in metal hydrides is studied and it can be concluded that no metal hydride known to us today is capable of satisfying the DOE ultimate targets. Finally, the study ends with options accessible to AGA to purchase hydrogen within Sweden and how they can be cleaned to meet the fuel cell gas purity requirements.
42
Elfverson, Cajsa. "Analysis of physical and chemical properties of fractionated grains and seeds with an emphasis on barley /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5708-4.pdf.
43
Stanton, David. "Coloured, photocatalytic coatings for self-cleaning and architectural glazing applications : precursors and processes for the aerosol-assisted chemical vapour deposition of functional coatings on glass". Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681056.
Resumen
There are a number of “smart” coatings that can be applied to glass. These include self-cleaning coatings based on titanium dioxide, and low-E coatings based on fluorine-doped tin oxide. Products are often more desirable with colour options such as Pilkington Activ BlueTM. There are currently no alternatives to body tinting glass to achieve colour, which is a time-consuming and expensive procedure. The work in this project details a number of coloured coatings via the AACVD or combustion processing of metal nitrate/urea precursors.
44
Flückiger, Peter Henri. "The use of life-cycle assessment and product risk assessment within application development of chemicals : a case study of perchloroethylene use in dry cleaning /". [S.l.] : [s.n.], 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13047.
45
Monteiro, Patricia Guerreiro. "Análise da limpeza dentinária em canais radiculares preparados com um sistema rotatório e diferentes substâncias químicas". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/23/23145/tde-11042008-110242/.
Resumen
O desenvolvimento de instrumentos endodônticos em ligas de níquel-titânio (Ni-Ti) derivou maior rapidez na modelagem do canal radicular o que nos leva a questionar se realmente estariam as substâncias químicas auxiliares tendo oportunidade de agir convenientemente, considerando que o tempo de atuação das mesmas foi significantemente encurtado. Tendo em vista esse aspecto foi objeto deste trabalho avaliar, com auxílio de microscopia eletrônica de varredura (MEV) e leituras computadorizadas, a limpeza da superfície dentinária radicular, terços cervical, médio e apical, em canais radiculares de incisivos inferiores humanos, preparados pelo sistema rotatório K3?ENDO diante do uso de hipoclorito de sódio a 2,5%, (pH 11,0), do creme de Endo PTC reagindo com hipoclorito de sódio a 0,5%, (pH 11,0), empregando-se essa substância em duas diferentes consistências; sua consistência normal (Endo PTC-N) e uma outra de menor densidade (Endo-PTC-L); e, de um gel de clorexidina (Endogel®) com dois tipos de irrigação final. Concluída a fase de preparo todos os grupos receberam irrigação-aspiração final com soluções de hipoclorito de sódio a 0,5%, (pH 11,0) e de EDTA-T a 17%, exceção feita ao grupo em que se empregou o Endogel®, para o qual seguiu-se dois regimes de irrigação, em um grupo, irrigação-aspiração final com 20 mL de soro fisiológico, conforme recomendações do fabricante e em outro grupo empregou-se irrigação com EDTA-T. As amostras foram então preparadas para MEV e suas imagens analisadas pelo programa Scion Image. Os resultados revelaram haver diferença estatisticamente significante entre os grupos, sendo que o grupo do Endo-PTC-L se mostrou superior aos demais grupos testados no terço médio e apical já o grupo do Endogel seguido da irrigação final com EDTA-T apenas no terço médio, não havendo diferença estatística entre eles.The development of nickel-titanium (NiTi) endodontic instruments results in more quickness during the root canal shaping phase that induce us to discuss if really would be the chemical substances are having opportunities to act properly, considering that the time of action of the same was significantly reduced. The object of this research was evaluate, using the scanning electron microscopy (SEM) and computerized analysis, the cleaning on root canal walls in coronal, middle and apical thirds in mandibular human incisives prepared with K3 NiTi rotary instruments and different chemical substances: 2,5% sodium hypochlorite (pH 11,0), Endo PTC cream at normal consistency (Endo PTC-N) neutralized by 0,5% sodium hypochlorite (pH 11,0), Endo PTC cream with lower density (Endo PTC-L) neutralized by 0,5% sodium hypochlorite (pH 11,0) and chlorhexidine gel (Endogel). Concluded the cleaning and shaping phase, all the groups received a final irrigation with of 0,5% sodium hypochlorite solution (pH 11,0) followed by 17% EDTA-T solution, except the Endogel group that received two different regimens of final irrigation, one group with 20 ml of physiological serum and another with the 17% EDTA-T solution. The samples were prepared for the SEM analysis and the images obtained were analyzed using the Scion Image program. The results showed a significant difference between the groups tested seeing that the Endo PTC-L group, in middle and apical thirds and Endogel followed by the final irrigation with EDTA-T group, in middle third were superiors in comparation with the other groups.
46
Patel, Ankit Arvind. "Novel P-(SBMA) Grafted Glass Fiber Filters and Glass Slides for Oil-Water Separation and Underwater Self-Cleaning Applications". University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353362655.
47
Ersoz, Tugce Irfan. "Application Of Semi Conductor Films Over Glass/ceramic Surfaces And Their Low Temperature Photocatalytic Activity". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610377/index.pdf.
Resumen
Semiconductor metal oxides can be induced by light with proper wavelength resulting in oxidation and reduction reactions for the transformation of water and oxygen molecules into active radicals. With this method, it is possible to obtain self-cleaning surfaces and products having antimicrobial properties.
The aim of this study is to develop semiconductor metal oxide thin films for multifunctional glass products and the characterization of photocatalytic self cleaning and antimicrobial properties. As semiconductor metal oxidestitanium dioxide (TiO2), tin oxide (SnO2) and their binary mixtures (TiO2-SnO2) are selected because of their abundancy, non toxic properties, stability and the ability of absorbing light close to visible range. Also the effect of metal dopants such as praseodymium (Pr), palladium (Pd), silver (Ag) and iron (Fe) was examined with these metal oxides. The colloidal solutions were synthesized by using sol-gel method in order to apply the developed method to industrial usage as applying on large surfaces. The glass substrates were coated with the colloidal solutions by dip coating and the dried samples were calcined under air flow. The best calcination condition for pure TiO2 coated thin film was determined as 400oC for 45 minutes. Surface characterization studies were performed by using UV-Visible Spectrophotometer for band gap measurement, CAM for contact angle measurement, SEM for surface morphology and tophology. The methylene blue adsorption tests were carried out and the effective surface area of the samples were predicted by the Langmuir adsorption isotherm of samples. The photocatalytic activities of the coated thin films were measured with the degradation of organic materials as red wine and methylene blue, and with the antimicrobial activity tests as counting the number of viable E.coli cells. 61.2% deactivation of methylene blue stain was achieved over SnO2 coated thin films while this was 22.1% over TiO2 coated thin films after irradiation for 180 minutes. The superior photocatalytic activity was observed with TiO2 samples doped with Pd and Ag ions. The TiO2-SnO2 coated samples performed limited photocatalytic activity which is less than the activity of SnO2 coated samples which was confirmed with surface area measurements as SnO2 coated samples had higher surface area (9.81 cm2/cm2) than TiO2-SnO2 coated samples. Surface area increased with increasing the amount of SnO2 and it was in the following order: SnO2 >
80% SnO2 + 20% TiO2 >
50% SnO2 + 50%TiO2 >
35% SnO2 + 65%TiO2 >
20% SnO2 + 80% TiO2 >
TiO2.
48
Costa, Thiago Ranzani da. "Estudos de biofilmes microbianos em membranas de osmose reversa". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-09032017-145456/.
Resumen
Sistemas de membranas filtrantes, principalmente os de osmose reversa, estão sendo cada vez mais utilizados em diversos seguimentos de empresas (farmacêutica, tratamento de água, alimentícia e química), devido à diminuição do preço dos elementos filtrantes e da alta qualidade do produto obtido. O biofouling corresponde a um tipo de fouling inevitável, caracterizado pelo crescimento de microrganismos na superfície das membranas e liberação de EPS pelos mesmos; por isso, um melhor conhecimento sobre estas estruturas é necessário. O presente trabalho teve como objetivo caracterizar o biofouling em diferentes membranas de osmose reversa colmatadas de diferentes indústrias pela técnica da autópsia e comparar com resultados obtidos com biofilmes de cultura pura formados em membranas de osmose reversa; além de verificar a influência de biofilmes na deposição de sais e ação de compostos químicos utilizados na limpeza química de membranas nos mesmos. A autópsia dos elementos colmatados mostrou uma grande quantidade de células viáveis porém, com concentrações de carboidratos muito baixas; diferentemente do que ocorreu quando biofilmes de cultura pura isolados destas membranas foram analisados, apresentando correlações fortes entre quantidade de células viáveis e macromoléculas como proteínas e, principalmente, carboidratos. Com relação à influência dos biofilmes na deposição de sais, dois dos quatro biofilmes de cultura pura apresentaram incorporação de bário em sua estrutura (revelado por análises de fluorescência de raios X), esta incorporação, provavelmente, ocorreu por troca iônica e não pela deposição de sulfato de bário. Compostos como hidróxido de sódio (pH = 12) e ácido clorídrico (pH = 2) apresentaram bons resultados na diminuição de células viáveis porém, a recuperação dos microrganismos foi menor com a utilização do ácido. Os compostos EDTA e SDS não foram eficazes na diminuição de viáveis.Systems of filter membranes, especially reverse osmosis, are being increasingly used in various segments of companies (pharmaceutical, water treatment, food and chemical industries) due to the decrease in the price of the filter elements and high quality of the product. The biofouling corresponds to a type of inevitable fouling characterized by growth of microorganisms on the surface of the membrane and release of EPS by them; so a better understanding of these structures is necessary. This study aimed to characterize the biofouling in different reverse osmosis membranes addressed from different industries by the technique of autopsy and compared with results obtained with pure culture biofilms in reverse osmosis membranes; and to verify the influence of biofilms in the deposition of salts and action of chemical compounds used in chemical cleaning of membranes in them. The autopsy of clogged elements showed a lot of viable cells but with very low carbohydrate concentrations; unlike what occurred when biofilms isolated pure culture of these membranes were analyzed, showing strong correlation between number of viable cells and macromolecules such as proteins and especially carbohydrates. Regarding the influence of biofilms in the deposition of salts, two of the four pure culture biofilms showed barium incorporation in its structure (revealed by fluorescence analysis X-ray), this merger probably occurred by ion exchange and not by deposition barium sulfate. Compounds such as sodium hydroxide (pH = 12) and hydrochloric acid (pH = 2) showed good results in the decrease of viable cells however, the recovery of microorganisms was lower with use of the acid. EDTA and SDS compounds were not effective in reducing viable.
49
Gupta, Vipul. "Deposition and Characterization of Hydrophobic Coatings". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3859.
Resumen
Hydrophobic coatings find application in various sectors of the economy including to electronics, textiles, optical devices, and in scientific and commercial equipment. These different applications demand that different hydrophobic coatings posses a range of properties that may include smoothness or roughness, thicknesses on the order of a monolayer or a micron, robustness or the ability to dissolve quickly, transparency or opacity, water resistance or water permeability, electrical conductivity, oleophobicity, etc. However, whatever the final/desired properties, deposition via dry-deposition processes offers significant advantages, including greater reproducibility, increased environmental friendliness, and cost effectiveness on an industrial scale. Herein I explore the chemical vapor deposition of silanes and the characterization of a commercial, hydrophobic coating to better prepare and understand hydrophobic coatings on different materials. One of the characterization techniques I used frequently in these studies is X-ray photoelectron spectroscopy (XPS). Accordingly, in Chapter 2 of this thesis I discuss this technique vis-à-vis the chemical shifts it detects, which reflect the oxidation states of materials being probed. In particular, I discuss a recommendation made over a decade ago by Gion Calzaferri for 'fixing' the problem of oxidation numbers as applied to organic materials and show how XPS confirms his suggestion. In Chapter 3 I introduce hydrogen as an etch/cleaning gas for silicon wafers. I first show that, like argon and oxygen plasmas, hydrogen plasmas will effectively clean silicon wafers. However, I then show that hydrogen plasma treatment leads to a silicon surface that is chemically different than those prepared with the other plasmas and that undergoes silanization to a greater extent -- the resulting surfaces have higher water contact angles and thicknesses. In Chapter 4 I study the deposition of a potential barrier layer for water, which was prepared from an aza silane: N-n-butyl-aza-2,2-dimethoxysilacyclopentane (1) in a molecular layer deposition (MLD)-like process using either water or ammonium hydroxide as the second half reactant. This molecule has the interesting property of undergoing self-limiting growth, where the termination of this growth is accelerated by use of an ammonium hydroxide catalyst. Interestingly, films of 1 are considerably thicker on nylon than on silicon, which is explained by nylon acting as a water reservoir in the reaction. In Chapter 5 I show the careful characterization of the hydrophobic coating on an Apple iPod nano, which was probed by ToF-SIMS, wetting, and XPS. I could identify that the coating is only applied to the touchscreen of the device. SIMS suggested that the fluorinated coating contains oxygen, which should add to its biodegradability. Finally, in Chapter 6 I make recommendation for future work in these areas.
50
Bayless, Lynette Vera. "Photocatalytic oxidation of volatile organic compounds for indoor air applications". Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1496.