The Fischer-Tropsch reaction technology is utilised in Sasol’s Coal-to-liquid plant to produce liquid fuels from low grade coal. There are several processes on the Coal-to-liquid plant that generate aqueous streams which contain a high organic load and require treatment. The main contributors to the wastewater are the Phenosolvan plant, producing stripped gas liquor (SGL), and the Synthol plant, producing Fischer-Tropsch reaction water (FTRW). Stripped gas liquor contains water, organic acids, ammonia, and potentially toxic phenols. Fischer-Tropsch reaction water contains volatile fatty acids and alcohol. Stripped gas liquor is therefore nitrogen-rich while FTRW is nitrogen-deficient and requires nutrient supplementation for anaerobic treatment. Therefore co-treatment of the two streams could reduce nitrogen supplementation requirements. This study is part of a larger project to determine the feasibility of anaerobically co-digesting FTRW and SGL. This study has looked at the influence of SGL on the methanogenic activity of FTRW-acclimated sludge and involved the development of a method which allows accurate recording of the methanogenic activity in batch assays. Other studies involving the anaerobic digestion of high phenolic wastewaters showed that the phenol had an inhibitory effect on the specific methanogenic activity of the sludge, which was not acclimated to the phenol. The objective of this work was to test the hypotheses that (1) anaerobic sludge acclimated to FTRW will be inhibited by high molecular weight organics in SGL and (2) FTRW-acclimated sludge will not degrade phenolic compounds in SGL. This information will be used for designing process configurations for simultaneous treatment of the two streams with minimum contamination of the effluent stream. The serum bottle was used as a small batch reactor and the biogas production was monitored as an indication of the state of the reaction. The biogas produced was collected and measured by the downward displacement of a sodium hydroxide solution, which absorbed the carbon dioxide and collected only the methane. A concentration of 1 g COD/ℓ FTRW was chosen as the reference test due to the reproducibility of the replicates within each experiment as well as its reproducibility across different batches of sludge. For the first inhibition test, the test units contained an additional 5% SGL (0.05 g COD/ℓ SGL) and an additional 15% SGL (0.15 g COD/ℓ SGL, i.e. 13% of the total COD load) respectively, added to 1 g COD/ℓ FTRW. The 5% SGL test unit showed no inhibition compared to the reference unit. There was a reduction in the specific methanogenic activity of the 15% SGL test units compared to the reference unit. Since the total COD load was not the same in each unit, it cannot be conclusively stated that the SGL was responsible for the reduction in SMA, but this seems a reasonable possibility in the light of results from the reference test selection experiments which showed higher SMA at higher organic loading rates. For the second inhibition test, the test units contained 85% FTRW (0.85 g COD/ℓ FTRW) and 15% SGL (0.15 g COD/ℓ SGL) to make up a total COD load of 1 g COD/ℓ. There was an increase in the specific methanogenic activity of the test unit compared to the reference unit. There was very little change in the phenol concentration. Therefore, it was concluded the addition of SGL potentially reduced the SMA and that this could be an inhibitory effect, but that any inhibition would be a function of the concentration of potentially inhibitory substances in SGL and that these concentrations vary from batch to batch. However, the degree of SMA reduction is fairly low and would not prevent co-digestion of the two streams at the concentrations tested. It has been shown that FTRW anaerobic digestion can proceed adequately in the presence of SGL. There was some evidence that phenolics were degraded but at a much slower rate than COD. The percentage reduction in SMA due to additional SGL at concentrations and SGL:FTRW ratios tested was between 0 and 51%. Ultimately, this work is a first step in the development of a co-digestion model relating organic loading rate, SGL:FTRW feed ratio to methane recovery and extent of biodegradation of phenol for use in the design and optimization of a co-digestion system. / M.Sc.Eng. University of KwaZulu-Natal, Durban 2014.

Thesis (M.S.)--Brigham Young University. Dept. of Chemical Engineering, 2006. / Includes bibliographical references (p. 89-95).

To date there has been much work carried out in the field of surface science to gain a better understanding of the fundamentals of a wide range of catalytic systems and reactions. The central theme of this thesis relates to cobalt based Fischer-Tropsch synthesis (FTS) with particular focus on the structure, composition and surface chemistry of CoPd bimetallic systems and on the interaction of Co with oxide support materials. In the work described in this thesis MEIS and STM are used to examine the growth of Co on Pd{111} and to characterise the structure of CoPd alloys created by thermal treatment of thin Co films. MEIS investigations indicate that Co grows initially as an fcc overlayer, but beyond a few layers, a stacking fault exists resulting in hcp growth. On annealing between 550 and 700 K, a previously unreported ordered surface alloy is observed giving rise to a p(2 x 1) structure which is concluded to be the surface termination of an ordered CoPd bulk alloy. At higher annealing temperatures, long range Moiré structure is observed by STM which MEIS reveals to correspond to a Pd-rich alloy. MEIS is used to investigate adsorbate induced segregation effects at CoPd surfaces on Pd{111}. The adsorption of O2, CO, H2 and CO/H2 mixtures (syngas) were all examined on a range of bimetallic surfaces. Oxygen adsorption on CoPd alloys strongly segregates cobalt to the surface as a result of the facile oxidation reaction. The behaviour of the components of syngas was more complex with the most noticeable effects being observed on surfaces which were more defect rich. The growth, annealing behaviour and adsorption properties of Co particles on oxide and mixed oxide surfaces are examined using MEIS and TPD.

A cold-flow vibated-bed microreactor system, operating at the room temperature and atmospheric pressure, was built and tested. The purpose of this microreactor was to simulate gas- and solid-mixing in a hot-flow microreactor system. The latter is being developed to study carbon deposition rates for continuous Fischer-Tropsch synthesis from a low H₂:CO gas with rapid switching of catalyst between gas atmospheres. The cold-flow microreactor consisted of three chambers with vertical sliding baffles that shift catalyst between the smaller, center reaction chamber and two outer chambers. The results show that the solid mixing within each chamber is essentially complete within one second after transfer of catalyst. The solid mixing was independent of gas flow and gas flow rate. Results of gas-mixing studies show that gas transfer between chambers of the microreactor was due to the transfer of gas within the interstices of transferred catalyst particles. During rapid baffle-switching intervals, complete gas mixing within each chamber occurred. The amount of gas transferred from the center chamber to each outer chamber was nearly constant and increased only slightly with feed gas rate to the center chamber. For the gas feed rates tested, the percentage of gas fed to the center chamber that transferred to each outer chamber was low, ranging from 1.2 to 4.9 percent. The results of this study are significant to the further development of the "sliding-baffle" microreactor for continuous Fischer-Tropsch synthesis, from a low H₂:CO gas. The microreactor will give important information on the rate of carbon deposition in a system that switches catalyst between two gas atmospheres. / M.S.

Thesis (Ph.D.(Chemistry))--University of Pretoria, 2004. / Includes summary. Also available online.

In this work, carbonaceous deposits on spent HTFT catalysts were investigated. This research was required in order to better understand the observed loss in productivity observed in the industrial reactors, with the aim of improving the economy of the HTFT process. A host of complementary techniques were employed to systematically determine the composition of a typical catalyst recovered from a reactor. Spent HTFT catalysts are comprised of magnetite and a mixture of iron carbides as well as adsorbed hydrocarbon products (soft carbon) and hard carbon. Reaction initiates at the particle surface and along the promoter-rich grain boundaries toward the core of the grains. A partially reacted particle would therefore have a core-shell structure, with magnetite representing the unreacted region of the catalyst. The reacted region consists of a porous carbonaceous matrix with soft carbon and carbide crystallites nestled in this matrix. The hard carbonaceous species is a mixture of polymeric carbon and polycyclic aromatic hydrocarbons. The particle structure is linked to the sample preparation method and an alternative method yielding catalyst particle with uniformly distributed promoter elements could be beneficial. Investigating carbonaceous species is a complex process, and development of a fresh methodology would aid in the quest for insight into the nature of carbonaceous species in various systems. A new approach which entails a combination of the traditional techniques combined with MALDI-TOF MS enabled a deeper investigation. Additional aspects such as the molecular weight distributions along with known information about crystallinity and morphology of the catalyst provide a comprehensive study of carbonaceous material. Polymeric carbon and very large polycyclic aromatic hydrocarbons constitute hard carbon and can be observed with minimal sample preparation procedures. The evolution of the HTFT catalysts was investigated as a function of time-on-stream. This enabled us to study the effects of increasing amounts of hard carbon on the activity and the chemical and physical properties of the catalysts. The catalyst activity was found to decrease with increasing hard carbon content, although the effect of carbon deposition cannot be distinguished from phase transformation (oxidation) which occurs simultaneously. A method to quantify the amount of hard carbon, which progressively builds up on the catalyst, was demonstrated. This required a great deal of method development, which provides a platform for future investigations of these catalysts. Importantly, it allows predictions of the amounts of carbon that will be deposited after a certain reaction time. This allows more efficient regulation of catalyst replacement. The production of fine carbon-rich particles in the industrial reactor poses a major problem in the process. Carbon deposition leads to an increase in particle diameter with time on-stream. Permissible levels of hard carbon were identified, beyond which the mechanical strength of the catalyst particles deteriorate. This leads to break-up of the particles and therefore fines formation. The surface area and pore volume generally increase with progressive deposition of hard carbon, while the bulk density of the catalyst material exhibits a linear decrease with carbon build-up. A mechanism is proposed for hard carbon formation which apparently occurs through the dissociative adsorption of CO to form a carbon monolayer. This is followed by polymerisation of the carbon atoms. Meta-stable interstitial carbides are formed at the iron-carbon interface. Owing to a carbon concentration gradient between the top of the surface and the bottom of the metal or carbide particle, carbon diffusion across the crystal (carbide decomposition) and grows as a PAH molecule lifting the iron carbide away from the particle. As this corrosion process is intrinsic to iron-based catalysts, a catalyst that contains sulphur is proposed for future development.

Orientador: Reginaldo Guirardello / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-18T13:21:06Z (GMT). No. of bitstreams: 1 Yamada_ShinobuTomas_D.pdf: 3876142 bytes, checksum: 951723c2abec9e70853595542ea18fe3 (MD5) Previous issue date: 2011 / Resumo: Esta tese apresenta a cinética e a fluidodinâmica do processo Fischer Tropsch realizado nos softwares científicos Fortran (Formula Translation) e CFX (Fluidodinâmica Computacional) da AEA Technology plc. O presente trabalho é uma simulação computacional de um sistema catalítico, multifásico, multicomponente e não isotérmico com topologia tridimensional, baseado em catalisador de cobalto suportado, recheio de esferas de aço e meio reacional formado por pseudocomponentes, gás combustível - GLP, nafta - gasolina - diesel, ceras de baixo - médio - alto peso molecular e vapor de água, além do gás de síntese (CO + H2) não convertido. As modelagens da cinética de reação e do balanço de massa estão estruturadas na linguagem de programação Fortran com modelos matemáticos da tecnologia Fischer Tropsch e as modelagens dos balanços de energia, momento e turbulência pelo software computacional CFX, com geometria baseada no Reator Arge Sasol em Leito Fixo composto por cinco domínios (recheio - meio reacional - entrada - saída - parede) e um subdomínio (catalisador), configuradas numa malha com mais de cinco milhões de elementos e um milhão de nós. A cinética é o modelo esquematizado por Sarup-Wojciechowski (1989) com a constante cinética definida pela expressão modificada da lei de Arrhenius. A modelagem da fluidodinâmica é tratada pelas equações de Navier Stokes e turbulência através do modelo k-? e "disperse phase zero equation", complementados pela biblioteca de propriedades fisico-químicas Diadem DIPPR, artigos científicos e experimentos em planta piloto realizados na Unidade de Industrialização do Xisto - Petrobras, São Mateus do Sul - (PR) / Abstract: This thesis presents the fluid dynamics and the kinetics of Fischer Tropsch Process in a fixed bed reactor accomplished in the scientific software Fortran (Formula Translation) and CFX (Computational Fluid Dynamics) of AEA Technology plc. The current work is a computational simulation of the catalytic system, multiphase, multicomponent and non isothermal with 3D topology, that is based on the cobalt supported catalyst, column random packing and the reaction mean treated on pseudo components concept, fuel gas - PLG, naphtha - gasoline - diesel oil, low - medium - high molecular weight waxes and water steam, besides non converted syngas (CO + H2). The kinetics reaction modelling and mass balance are structured in Fortran programming language with mathematic models of Fischer Tropsch technology. Also the energy balance, momentum and turbulence phenomena are structured by CFX, with geometry based on the Arge Sasol Fixed Bed Reactor consisted for five domains (packing - reaction media - in- out - wall) and one subdomain (catalyst), configured in a mesh with more than five million of elements and one million of nodes. The kinetic models are schematized by Sarup-Wojciechowski (1989) equation and the kinetic constant defined according to a modified expression of the Arrhenius law. The modelling of the fluid dinamics are considered on the Navier Stokes fundamental equations and turbulence phenomena through k-? and "disperse phase zero equation", complemented by the physical-chemicals library property Diadem DIPPR, scientifc articles and data referred to pilot plant experiments performed in the Unidade de Industrialização do Xisto - Petrobras, located in São Mateus do Sul - (PR) / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

Thesis (PhD (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: A techno-economic feasibility study was performed to compare biological and thermochemical process routes for production of liquid biofuels from sugarcane bagasse in South Africa using process modelling. Processing of sugarcane bagasse for the production of bioethanol, pyrolysis oil or Fischer-Tropsch liquid fuels were identified as relevant for this case study. For each main process route, various modes or configurations were evaluated, and in total eleven process scenarios were modelled, for which fourteen economic models were developed to include different scales of biomass input. Although detailed process modelling of various biofuels processes has been performed for other (mainly first world) countries, comparative studies have been very limited and mainly focused on mature technology. This is the first techno-economic case study performed for South Africa to compare these process routes using data for sugarcane bagasse. The technical and economic performance of each process route was investigated using the following approach: Obtain reliable data sets from literature for processing of sugarcane bagasse via biological pretreatment, hydrolysis and fermentation, fast and vacuum pyrolysis, and equilibrium gasification to be sufficient for process modelling. Develop process models for eleven process scenarios to compare their energy efficiencies and product yields. In order to reflect currently available technology, conservative assumptions were made where necessary and the measured data collected from literature was used. The modelling was performed to reflect energy-self-sufficient processes by using the thermal energy available as a source of heat and electricity for the process. Develop economic models using cost data available in literature and price data and economic parameters applicable to South Africa. Compare the three process routes using technical and economic results obtained from the process and economic models and identify the most promising scenarios. For bioethanol production, experimental data was collected for three pretreatment methods, namely steam explosion, dilute acid and liquid hot water pretreatment performed at pretreatment solids concentrations of 50wt%, 10wt% and 5wt%, respectively. This was followed by enzymatic hydrolysis and separate co-fermentation. Pyrolysis data for production of bio-oil via fast and vacuum pyrolysis was also collected. For gasification, data was generated via equilibrium modelling based on literature that validated the method against experimental data for sugarcane bagasse gasification. The equilibrium model was used to determine optimum gasification conditions for either gasification efficiency or syngas composition, using sugarcane bagasse, fast pyrolysis slurry or vacuum pyrolysis slurry as feedstock. These results were integrated with a downstream process model for Fischer-Tropsch synthesis to evaluate the effect of upstream optimisation on the process energy efficiency and economics, and the inclusion of a shift reactor was also evaluated. The effect of process heat integration and boilers with steam turbine cycles to produce process heat and electricity, and possibly electricity by-product, was included for each process. This analysis assumed that certain process units could be successfully scaled to commercial scales at the same yields and efficiencies determined by experimental and equilibrium modelling data. The most important process units that need to be proven on an industrial scale are pretreatment, hydrolysis and fermentation for bioethanol production, the fast pyrolysis and vacuum pyrolysis reactors, and the operation of a twostage gasifier with nickel catalyst at near equilibrium conditions. All of these process units have already been proven on a bench scale with sugarcane bagasse as feedstock. The economic models were based on a critical evaluation of equipment cost data available in literature, and a conservative approach was taken to reflect 1st plant technology. Data for the cost and availability of raw materials was obtained from the local industry and all price data and economic parameters (debt ratio, interest and tax rates) were applicable to the current situation in South Africa. A sensitivity analysis was performed to investigate the effects of likely market fluctuations on the process economics. A summary of the technical and economic performances of the most promising scenarios is shown in the table below. The bioethanol process models showed that the liquid hot water and dilute acid pretreatment scenarios are not energy self-sufficient and require additional fossil energy input to supply process energy needs. This is attributed to the excessive process steam requirements for pretreatment and conditioning due to the low pretreatment solid concentrations of 5wt% and 10wt%, respectively. The critical solids concentration during dilute acid pretreatment for an energy selfsufficient process was found to be 35%, although this was a theoretical scenario and the data needs to be verified experimentally. At a pretreatment level of 50% solids, steam explosion achieved the highest process thermal energy efficiency for bioethanol of 55.8%, and a liquid fuel energy efficiency of 40.9%. Both pyrolysis processes are energy self-sufficient, although some of the char produced by fast pyrolysis is used to supplement the higher process energy demand of fast compared to vacuum pyrolysis. The thermal process energy efficiencies of both pyrolysis processes are roughly 70% for the production of crude bio-oil that can be sold as a residual fuel oil. However, the liquid fuel energy efficiency of fast pyrolysis is 66.5%, compared to 57.5% for vacuum pyrolysis, since fast pyrolysis produces more bio-oil and less char than vacuum pyrolysis. / Centre for Renewable and Sustainable Energy Studies

Este trabalho tem como objetivo traçar um panorama geral da tecnologia de gaseificação ao longo da história. Inicialmente concebida para obter gás do carvão mineral e possibilitar uma iluminação pública mais eficiente, a gaseificação passou por várias fases. Na virada do século XIX para o XX, quando o town gas perdeu a iluminação pública para a eletricidade, a produção de gás passou a se voltar para aquecimento e cocção. Se novas possibilidades foram criadas a partir da descoberta da síntese de Fischer-Tropsch (que possibilitava a transformação do gás de síntese em líquidos que poderiam substituir combustíveis e matérias-primas para toda a cadeia petroquímica), a resolução dos problemas de logística do gás natural reduziu a importância do gás do carvão mineral também para o aquecimento e cocção. Crises de abastecimento de petróleo, o principal combustível do século XX, motivaram novas iniciativas e novas formas de utilização da gaseificação como, por exemplo, os gasogênios, que gaseificavam biomassa e carvão para movimentar veículos automotores especialmente durante a Segunda Grande Guerra. Já nos períodos de abundância de petróleo a tecnologia acabava por ser abandonada, uma vez que este era muito mais eficiente e conveniente. Na passagem do século XX para o século XXI, entretanto, as preocupações com as mudanças climáticas colocaram em cheque a contínua utilização de combustíveis fósseis entre os quais o petróleo. Nesse contexto abriu-se uma nova perspectiva para a gaseificação de biomassa, uma vez que esta, combinada com as possibilidades criadas pela síntese de Fischer-Tropsch, possibilitou a criação do conceito de biorrefinarias e de toda uma cadeia química a partir de matérias-primas não apenas renováveis, mas que também são residuais e não alimentares. Embora ainda haja desafios técnicos e, principalmente, econômicos a serem alcançados, outros desafios deste século além da questão climática -, os resíduos sólidos urbanos podem constituir-se em uma importante fonte de insumos para o processo de gaseificação. / This dissertation aims to deliver a systematic approach of the history of gasification process. Initially conceived to obtain coal gas to viabilize more efficient lighting for major cities, the gasification process has passed through several phases. During the Nineteenth Century, the town gas (the gas obtained from coal) has revolutionized night life in modern cities. At the turn of the Nineteenth Century, town gas lost public lighting to electricity, and gas from coal had to migrate to heating and cooking. New possibilities were created with the Fischer-Tropsch synthesis in the twenties. This process enabled the transformation of Syngas a product of the gasification process into any kind of hydrocarbon molecule. So, it could have been a useful substitute to oil, mainly during the oil supply crisis. The Twentieth Century was characterized by intense oil utilization in transport, mechanical forces, electricity generation and also creating products like plastic and asphalt. Gasification was seen as a very good alternative supply of raw material for these products, but in fact, the several oil supply crisis of the Twentieth Century were too short for make the gasification feasible. At the end of twentieth century another issue arose to boost gasification initiatives: climate change. Due the greenhouse effect and concerns about its consequences, researchers and companies started projects of biomass gasification to replace fossil fuels - which includes oil. So far, all these initiatives havent shown up as feasible in commercial production, but the opportunity to create a fossil oil substitute from non food raw materials still involves a lot of effort.

Made available in DSpace on 2014-12-17T15:01:24Z (GMT). No. of bitstreams: 1 MarcioBDB_DISSERT.pdf: 1427541 bytes, checksum: 4ea4ab1aa3dd7faa960c62967facffc8 (MD5) Previous issue date: 2010-09-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / This work aims at the implementation and adaptation of a computational model for the study of the Fischer-Tropsch reaction in a slurry bed reactor from synthesis gas (CO+H2) for the selective production of hydrocarbons (CnHm), with emphasis on evaluation of the influence of operating conditions on the distribution of products formed during the reaction.The present model takes into account effects of rigorous phase equilibrium in a reactive flash drum, a detailed kinetic model able of predicting the formation of each chemical species of the reaction system, as well as control loops of the process variables for pressure and level of slurry phase. As a result, a system of Differential Algebraic Equations was solved using the computational code DASSL (Petzold, 1982). The consistent initialization for the problem was based on phase equilibrium formed by the existing components in the reactor. In addition, the index of the system was reduced to 1 by the introduction of control laws that govern the output of the reactor products. The results were compared qualitatively with experimental data collected in the Fischer-Tropsch Synthesis plant installed at Laborat?rio de Processamento de G?s - CTG?S-ER-Natal/RN / O presente trabalho tem como objetivo a implementa??o e adapta??o de um modelo computacional de equil?brio de fases visando o estudo do processo Fischer- Tropsch em reator leito de lama a partir de g?s de s?ntese (CO + H2) para a produ??o seletiva de hidrocarbonetos (CnHm), com ?nfase na avalia??o da influ?ncia das condi??es operacionais sobre a distribui??o dos produtos formados durante a rea??o. O modelo em quest?o leva em conta efeitos do equil?brio de fases de modo rigoroso num tambor flash reativo, uma cin?tica detalhada que prev? a forma??o de cada componente do sistema reacional, bem como malhas de controle do processo para as vari?veis press?o e n?vel da fase lama. O sistema de equa??es obtido ? do tipo Alg?brico Diferencial, e foi resolvido utilizando-se o c?digo computacional DASSL (Petzold, 1982). A inicializa??o consistente do sistema de equa??es foi feita com base na condi??o de equil?brio de fases inicial formado pelos componentes j? existentes no reator, sendo o ?ndice do sistema reduzido a 1 pela introdu??o das leis de controle que regem a sa?da de produtos do reator. Os resultados obtidos foram comparados qualitativamente com os dados experimentais coletados na planta de s?ntese de Fischer- Tropsch instalada no Laborat?rio de Processamento de G?s do CTG?S-ER em Natal/RN