Environmental regulations have historically been focused on individual emission points, facilities, or industrial sectors. However, recent and emerging regulations for greenhouse gas (GHG) emissions such as those contained in the Energy Independence and Security Act (EISA) of 2007 have introduced the concept of product life cycle limits on the emissions of transportation fuels. Thus, a complete life cycle assessment (LCA) of the transportation fuel must be completed where all emissions from field to the vehicle’s fuel tank and from tank to the vehicle’s exhaust must be assessed. However, although there have been extensive analysis of the GHG emissions associated with transportation fuels, there are substantial uncertainties associated with these estimates that can be attributed to poor data quality, inconsistent methodological choices, and model uncertainties, among others. This thesis evaluates the uncertainties present in LCA through the case study of fuel production using Fischer-Tropsch (F-T) synthesis of fuels derived from coal and biomass. Specifically, GHG emission estimates for F-T synthesis process scenarios are presented and the uncertainties in the estimates are discussed. Overall uncertainties in GHG emissions due to changes in the details of the process configurations in the F-T process can be up to 11%. This finding suggests that the details of fuel refining conditions will need to be specified in determining whether fuels meet GHG emission requirements, complicating the implementation of life cycle GHG regulations. / text

Um einen dauerhaften Einsatz Al2O3-basierter Feuerfestwerkstoffe in Hochtemperaturanlagen zur Synthesegaserzeugung zu ermöglichen, erfolgte die Entwicklung neuer Materialien mit verbesserter Thermoschock- und Korrosionsbeständigkeit gegenüber flüssiger Kohleschlacke. In einem industrienahen Spinell-Alumina-Verbundwerkstoff lässt sich die Mikro- und Porenstruktur durch Zugabe von 6 Gew.-% eines Spinell-reichen Zements optimieren, wodurch die Infiltration und zugleich die Korrosion durch saure Braunkohleasche erheblich reduziert werden konnte. Die Zugabe von 2,5 Gew.-% TiO2 zu einer Al2O3-Gießmasse führt ebenfalls zur Verbesserung der Thermoschockbeständigkeit und verhindert während des Tiegeltests die weitere Auflösung der Al2O3-Matrix, indem sich auf dem Werkstoff durch Reaktion mit MgO der Schlacke eine dichte in situ Spinell-Schutzschicht ausbildet. So erfolgte die Entwicklung von Materialien mit hervorragenden thermomechanischen Eigenschaften und ausreichender Korrosionsbeständigkeit, welche als umweltfreundliche und kostengünstige Alternative zu den derzeit eingesetzten Cr2O3-reichen Werkstoffen angesehen werden können.

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The past few years have seen an upsurge in the use of renewable biomass as a source of energy due to growing concerns over greenhouse gas emissions caused by the combustion of fossil fuels and the need for energy independence due to depleting fossil fuel resources. Although coal will continue to be a major source of energy for many years, there is still great interest in replacing part of the coal used in energy generation with renewable biomass. Combustion converts inherent chemical energy of carbonaceous feedstock to only thermal energy. On the other hand, partial oxidation processes like gasification convert chemical energy into thermal energy as well as synthesis gas which can be easily stored or transported using existing infrastructure for downstream chemical conversion to higher value specialty chemicals as well as production of heat, hydrogen, and power. Devolatilization or pyrolysis plays an important role during gasification and is considered to be the starting point for all heterogeneous gasification reactions. Pyrolysis kinetic modeling is, therefore, an important step in analyzing interactions between blended feedstocks. The thermal evolution profiles of different coal-biomass blends were investigated at various heating rates using thermogravimetric analysis. Using MATLAB, complex models for devolatilization of the blends were solved for obtaining and predicting the global kinetic parameters. Parallel first order reactions model, distributed activation energy model and matrix inversion algorithm were utilized and compared for this purpose. Using these global kinetic parameters, devolatilization rates of unknown fuel blends gasified at unknown heating rates can be accurately predicted using the matrix inversion method. A unique laboratory scale auto-thermal moving bed gasifier was also designed and constructed for studying the thermochemical conversion of coal-biomass blends. The effect of varying operating parameters was analyzed for optimizing syngas production. In addition, stable carbon isotope analysis using Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry (GC-C-IRMS) was used for qualitatively and quantitatively measuring individual contributions of coal and biomass feedstocks for generation of carbonaceous gases during gasification. The predictive models utilized and experimental data obtained via these methods can provide valuable information for analyzing synergistic interactions between feedstocks and also for process modeling and optimization.

In this study, imaging with ionizing radiation was evaluated as a research technique in coal research. Part of the evaluation was to conduct a thorough literature survey as well as a preliminary investigation into coal pyrolysis and gasification with micro–focus X–ray tomography. The literature survey summarizes previous research experiences, primarily focussing on the possibility of utilizing a specific coal bed for carbon dioxide sequestration and methane production. This includes quantifying the fracture and cleat network and visualizing the orientation of this network. The cleat and fracture spacing and aperture are used to calculate certain parameters necessary to model gas flow. Other aspects include non–destructive characterization which consisted of determining the porosity and the minerals and macerals present and the respective mineral distribution. The literature survey also includes a section on the utilization of neutrons in coal research and a description of a neutron imaging facility in South Africa is presented. Three coal samples from the Waterberg and Highveld regions of South Africa were used to investigate the process of pyrolysis through micro–focus X–ray tomography. The samples swelled significantly when 50% pyrolysis was achieved after which the samples became brittle. This verified the plastic nature of the coal, that is prevalent under these conditions. It was also possible to perform qualitative characterizations prior to and during the process. Regions of low and high density materials could also be visualized. The distribution of the minerals is indicative of the permeability of the organic matrix. Two coal samples of the Highveld regions were used to investigate gasification up to a level of 30%. It was possible to verify that the reaction progressed according to the mechanisms proposed by the un–reacted shrinking core model. The mineral matter and the high density coal macerals did not influence the reaction in any way. / http://hdl.handle.net//10394/7008 / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

Magistro baigiamajame darbe aptariamas Lietuvos ir Europos Sąjungos šalių energetikos sektorius. Apžvelgiamos direktyvos, strategijos, plėtros planai bei teisės aktai skirti energetikos plėtojimui šalyje. Tiriamuoju objektu pasirenkama Trakų Vokės katilinė, kuri aprūpina šiluma kvartalą degindama gamtines dujas vandens šildymo katiluose. Šiame darbe yra nagrinėjamos penkios alternatyvos: kogeneratorius ir dujiniai katilai, kogeneratorius su akumuliacine talpa ir dujiniais katilais, kogeneratorius su akumuliacine talpa ir biokuro katilais, kogeneratorius su akumuliacine talpa ir šilumos siurbliu, medienos dujofikavimo reaktorius su kogeneratoriumi ir vandens šildymo katilais. Alternatyvos yra nagrinėjamos dviem skirtingais scenarijais, kai kogeneratoriaus pagaminta elektra parduodama pagal VIAP tarifus ir pagal „Nord pool spot“ Lietuva biržos kainas. Tiriamasis darbas atliekamas naudojantis „energyPRO“ modeliavimo programa. Atlikus modeliavimą, sistemų veikimas įvertinamas pirminės energijos suvartojimu, ekologiniu ir ekonominiu požiūriais. Atliekama jautrumo analizė keičiant ekonominius rodiklius bei vertinant šilumos gamybą be kogeneracijos. Pagal gautus rezultatus suformuluojamos išvados. Darbą sudaro 10 skyrių. Apimtis – 79 psl. teksto be priedų, 47 iliustracijų, 10 lentelių, 74 bibliografiniai šaltiniai. / In this master thesis, Lithuanian and European Union’s countries energy sector was discussed. An overview was made on EU directives, Lithuanian strategies, development plans and legalizations. Investigation object was Trakų Vokė boiler house with its district heating system. In the boiler house heat produced by combusting natural gas. During the research five alternatives were analysed: cogeneration and heat only boilers, cogeneration with thermal storage and heat only boilers, cogeneration with thermal storage and biomass heat only boilers, cogeneration with thermal storage and high temperature heat pump, biomass gasification reactor with cogeneration and heat only boilers. Alternatives are analysed based on two scenarios, first on when cogeneration is working by fixed electricity tariffs and second when cogeneration is working by liberalized electricity market conditions. Thesis carried out using “energyPRO” modelling software. All modelled systems are assessed by techno-economic and ecological approach. A sensitivity analysis was made by changing economical values and assessing systems without cogeneration. Based on the results conclusion was formed. Thesis includes 10 chapters. Size of work – 79 pages excluding appendixes, 47 pictures, 10 tables, 74 reference sources.

In this study, imaging with ionizing radiation was evaluated as a research technique in coal research. Part of the evaluation was to conduct a thorough literature survey as well as a preliminary investigation into coal pyrolysis and gasification with micro–focus X–ray tomography. The literature survey summarizes previous research experiences, primarily focussing on the possibility of utilizing a specific coal bed for carbon dioxide sequestration and methane production. This includes quantifying the fracture and cleat network and visualizing the orientation of this network. The cleat and fracture spacing and aperture are used to calculate certain parameters necessary to model gas flow. Other aspects include non–destructive characterization which consisted of determining the porosity and the minerals and macerals present and the respective mineral distribution. The literature survey also includes a section on the utilization of neutrons in coal research and a description of a neutron imaging facility in South Africa is presented. Three coal samples from the Waterberg and Highveld regions of South Africa were used to investigate the process of pyrolysis through micro–focus X–ray tomography. The samples swelled significantly when 50% pyrolysis was achieved after which the samples became brittle. This verified the plastic nature of the coal, that is prevalent under these conditions. It was also possible to perform qualitative characterizations prior to and during the process. Regions of low and high density materials could also be visualized. The distribution of the minerals is indicative of the permeability of the organic matrix. Two coal samples of the Highveld regions were used to investigate gasification up to a level of 30%. It was possible to verify that the reaction progressed according to the mechanisms proposed by the un–reacted shrinking core model. The mineral matter and the high density coal macerals did not influence the reaction in any way. / http://hdl.handle.net//10394/7008 / Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012.

A systematic in-depth study has been undertaken to establish the corrosion mechanism of a Model 25Cr-35Ni-Fe alloy and four commercial alloys HP40Nb, AISI314, HP40Al and Alloy 800H in low oxygen, high sulphur and carbon containing environments typically found in coal gasification and fluidised bed combustion processes. A review of present knowledge of corrosion processes in purely oxidizing, sulphidizing and carburizing environments and multiple reactant carburizing/ oxidizing, carburizing/sulphizing and oxidizing/sulphidizing environments is given. The experimental programme was designed to establish the role of sulphur on the corrosion process by studying corrosion mechanisms in a sulphurfree H2-7%C0-1.5%H2o gas, a low sulphur H2-7%C0-1.5%H20-0.2%H 2 S gas (pS2_8= 10 bar), and a high sulphur H 2 -7%C0-1.5%H 2 0-0.6%H 2 S gas (pS = lO bar) at 800'C. All_21j_hree environments had a constant partiaf pressure of oxygen (po2 = 10 bar) and carbon activity (ac = 0.3). In the sulphur-free gas the Model alloy formed a thin uniform cr 2 o 3 layer which grew at a constant parabolic rate throughout the exposure period of 0 - 5000 hours. Surface working increased the growth rate and thickness of the Cr 2 o 3 layer but created a large number of cracks and pores which allowed carbon containing gaseous species to diffuse through the oxide to form carbide precipitates in the alloy substrata. Alloying additions of Si promoted the formation of an inner SiO layer which reduced the corrosion rate by cutting off the outward diffusion of Cr, Mn and Fe. Alloying additions of Mn promoted the formation of an additional outer (Mn, Fe )Cr 2o 4 layer. The 3. 5% Al content of the HP40Al was insufficient to form a complete Al 2 o3 layer. Alloy 800H was susceptible to localised internal oxidation. Adding a low level of sulphur (0.2% H 2 S) to the gas increased the corrosion rate of the Model alloy in the 1nitial stages. This rate gradually slowed down before becoming parabolic after 1000 - 2000 hours. This was due to the nucleation of sulphides in addition to oxides. The oxides and sulphides grew side by side until the oxides overgrew the sulphides to form a complete Cr 2o3 layer which cut off further ingress of sulphur from the gas. The entrapped sulphides promoted localized thickening of the oxide layer. Eventually the sulphur redistributed from the sulphides in the scale to internal sulphide precipitates in the alloy with the corrosion rate returning to that of the sulphur-fre,e gas for the rest of the exposure period (5000 hours total). In the commercial alloys the internal sulphide precipitates prevented the inner Si02 layer becoming complete. Sulphur doped the (Mn, Fe) Cr 2 0 4 outer layer ana the intermediate Cr 2o3 layer formed from the spinal layer, increasing the number of cation . vacancies and the growth rate of the scale. These factors caused a massive Cr depletion of the alloy substrata after several thousand hours. The internal carbides became unstable which led to a massive amount of internal attack and a dramatic increase (breakaway) in the corrosion rate. Due to its thickness and the presence of Si02 inner layer the external scale became susceptible to spallation. If this occurred the oxides and sulphides nucleated on the alloy surface again but sulphides. protective alloy. insufficient Cr was available for the oxides to overgrow the The sulphides therefore grew to form a fast growing nonsulphide scale which soon led to catastrophic failure of the Increasing the level of sulphur in the gas to 0.6% H2S caused oxides and sulphides to nucleate on the surface, but in this case the sulphides overgrew the oxides to form thick fast growing non-protective sulphide scales on all the alloys.

ABSTRACT REMOVAL OF HYDROGEN SULFIDE BY REGENERABLE METAL OXIDE SORBENTS Karayilan, Dilek M.S., Department of Chemical Engineering Supervisor : Prof. Dr. Timur Dogu Co-Supervisor: Prof. Dr. G&uuml / lSen Dogu June 2004, 166 pages High-temperature desulfurization of coal-derived fuel gases is an essential process in advanced power generation technologies. It may be accomplished by using metal oxide sorbents. Among the sorbents investigated CuO sorbent has received considerable attention. However, CuO in uncombined form is readily reduced to copper by the H2 and CO contained in fuel gases which lowers the desulfurization efficiency. To improve the performance of CuO-based sorbents, they have been combined with other metal oxides, forming metal oxide sorbents. Sulfidation experiments were carried out at 627 oC using a gas mixture composed of 1 % H2S and 10 % H2 in helium. Sorbent regeneration was carried out in the same reactor on sulfided samples at 700 oC using 6 % O2 in N2. Total flow rate of gas mixture was kept at 100 ml/min in most of the experiments. In this study, Cu-Mn-O, Cu-Mn-V-O and Cu-V-O sorbents were developed by using complexation method. Performance of prepared sorbents were investigated in a fixed-bed quartz microreactor over six sulfidation/regeneration cycles. During six cycles, sulfur retention capacity of Cu-Mn-O decreased slightly from 0.152 to 0.128 (g S)/(g of Sorbent) while some decrease from 0.110 to 0.054 (g S)/(g of Sorbent) was observed with Cu-Mn-V-O. Cu-V-O showed a very good performance in the first sulfidation and excessive thermal sintering in the first regeneration prevented further testing. Sulfur retention capacity of Cu-V-O was calculated as 0.123 (g S)/(g of Sorbent) at the end of the first sulfidation. In addition, SO2 formation in sulfidation experiments was observed only with Cu-V-O sorbent.

Liquid transportation fuels can be produced by gasification of carbon containing biomass to syngas( a gaseous mixture of CO and H2) with subsequent conversion of the syngas to fuels. One possible process is the so called mixed alcohols synthesis, which produces a mixture of ethanol and higher alcohols. Another possible process is the reaction of syngas to Fischer-Tropsch liquids, mainly diesel fuel. This study examines the economics of syngas, ethanol and diesel fuel production from lignocellulosic biomass (southern pine residues). The process is modeled with Aspen Plus, a process simulation software package. The process is simulated for plant sizes between 715 and 2205 dry tons/day. The feedstock moisture content is varied between 20% and 50% and the feedstock costs are varied between $30/dry ton and $80/dry ton. The influences of the examined variables on the minimum product selling price are determined. The economic effects of an integration of the mixed alcohols and the FT diesel process with a kraft mill are also evaluated.