Thesis (M.S.)--Missouri University of Science and Technology, 2010. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 17, 2010) Includes bibliographical references (p. 67-77).

Thesis (M.S. in chemical engineering)--Washington State University, December 2006. / Includes bibliographical references.

Thesis (M.S. in mechanical engineering)--Washington State University, August 2006. / Includes bibliographical references.

Thesis (Ph. D.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 1, 2007) Includes bibliographical references.

Thesis (M.S.)--Baylor University, 2006. / Includes bibliographical references (p. 134-141).

Percolating packed bed digesters were operated successfully in a batch mode using a wheat straw - dairy manure substrate of between 21 and 27% total solids. The vessels used had a nominal 10 1 volume and were constructed of perspex. Temperatures of 25-35°C were used, recirculation rates of 0-15 litres.hr-1 (the digesters having a diameter of 0.18 metres thus corresponding to superficial flow rates of between O and 0.382 l/m2 /hr), solid : liquid ratios of 1:1 to 4:1 and bed heights of 0.26 to 2.05 metres. The optima found were a temperature of 35°C, recirculation rate of 3 litres.hr1-, a solid: liquid ratio of 2:1 and a bed height of 1.5 metres. Experiments were conducted for periods of up to 70 days, though operation beyond a 40 day period was found to produce little extra biogas. The performance compared favourably with other high solids waste digesters with gas yields of 0.305 m 3 /kg VS added and solids losses of 47% volatile solids and 64% cellulose being obtained over a 40 day period. No major problems of inhibition or blocking occurred. Linking of digesters in series via their recirculation systems was found to be advantageous. Gas yields were found to be increased by approximately 18% and solids losses increased by approximately 20% when the waste was treated in this semicontinuous manner. These increases were found to be a result of the rapid transfer of well-adapted bacteria to the fresh digester. Lag phase in the fresh digester was reduced by three days and potentially inhibitory levels of volatile fatty acids were not present. Concentrations of up to around 5000 ppm VFAs were found during the start-up of batch digesters causing some inhibition of gas production. During semi-continuous operation however concentrations of around 2000 ppm were developed when fresh digesters were linked in, no inhibition occurred and in fact this concentration proved stimulatory to gas production. Experimentation into the optimum retention time of a maximum of three digesters in series was conducted, with retention times of 90, 60 and 30 days being considered. A 30 day retention period was found to depress gas production due to unstable conditions when fresh digesters were added by up to 32% compared with Batch Operation. Gas production was increased at both 60 and 90 day retention times by amounts similar to those previously stated. A retention time of 60 days was found to be optimum as little extra gas was produced after this time, with volatile solids losses being increased by only 9.3% by operating for a further 30 days. Colonisation of the solid substrate was shown to be rapid, by the use of adenosine 51 triphosphate analysis, gas production rate and electron microscope analysis. In addition a dynamic bacterial population appeared to be present in the solid phase with the rates of growth and attachment being approximately equal to the rates of decay and detachment. When digesters were operating in their steady phase, methanogens were present in the liquor at concentrations of between 10 6 - 10 7 /ml and non-methanogens at between 10 7 - 108 /ml showing a large population of bacteria to be present for the inoculation of fresh digesters.

The semi-continuous digestion of poultry litter and manure was carried out in 51 digesters at 35°C to determine the potential of each waste for methane production, and to investigate the relationships between gas yield (GY) and loading rate (LR). GY's obtained were 0.327 m3 kg VS added-1 for litter and 0.397 m kg VS added-1 for manure. During the digestion of litter, GY increased both with increasing retention time (RT) and influent concentration. For manure GY increased with influent concentration up to 2.6 - 4.1% VS after which further increases caused reductions in GY due to ammonia inhibition which reached 4274 mgl of NH4 + - N. The effects of raised concentrations of NH4 + - N on manure batch digesters seeded with sludge adapted to different levels of NH4 - N was investigated by shock loading NH4C1 or NH4 HCO3. High adapted seed was more tolerant of NH4C1 than low adapted seed whereas the opposite was true for NH4 HCO3 which at low levels had a stimulatory effect on low adapted seed. Long term effects of raised NH4 + -N concentrations were examined by adding NH4Cl to semi-continuously fed manure digesters. Increasing NH4 concentrations to 3062 mgl-1 and 4324 mgl-1 reduced GY's to 88% and 73°^ of control levels respectively. After periods of up to 22 weeks exposure to these concentrations GY's failed to regain untreated values indicating that complete adaptation had not occurred. The potential for digestion of poultry wastes at high solids concentrations (up to 27% TS) was tested in a packed bed type digester. Successful hydrolysis and acidogenesis occurred but methanogenesis was inhibited by NH4 + - N concentrations of up to 13,314 mgl -1. Replacing the liquor allowed intiation of Methane production during the digestion of manure but not litter. A study of Monod growth kinetics revealed that the increase in GY obtained with increasing influent concentration was due to the dependence of digester effluent concentration on RT but not influent concentration. Models were developed to describe the uninhibited digestion of litter and the inhibited digestion of manure.

The ready availability of biomass in Brazil makes this type of fuel a major candidate to integrate the country's energy matrix. Although this fuel is used as a primary energy source, its use for electricity generation is still modest. On the other hand, high efficiency and power density achieved by modem gas turbine engines make them a promising option for the power generation market. Thus, this thesis has as main objective to analyse the marriage between the solid fuel, biomass in this case, and gas turbines. Two main types of power plants are studied; the biomass integrated gasification gas turbine cycle (BIGGT) and the externally fired cycle (EFGT), which for the first time is thoroughly studied for the use of biomass fuel, plus the intercooled and recuperated variants of these power plants. The results are compared with the ordinary natural gas fuelled cycle. The method involves on- and off-design point performance and exergy analysis. The economic performance and optimisation for each cycle is also explored in order to assess their feasibility. The optimisation technique adopted is the Genetic Algorithm (GA) connected to the conventional hill-climbing methodology. This merge uses the GA to identify the region of optimum values, which are then passed on to the hill-climbing algorithm. In this way the long time demanded by the GA to converge is shortened and the unreliability of the hill-climbing method in finding the global optimum is overcome. The codes developed for design-point performance analysis and optimisation, compared with a commercial package, proved reliable and robust. The tools developed for exergy analysis (on- and off-design) are also robust and flexible, with the capability of analysing and calculating the properties of mixtures made of 23 different gases. The emissions equations are sufficiently accurate for the purposes of this thesis. The relationship proposed for calculating the variable operating and maintenance costs proved to be consistent with the current knowledge. The results show that the optimised cycles are competitive with current technology in terms of cost of electricity, the EFGT being the more competitive biomass cycle, with costs of electricity (US$ 0.07/kWh) comparable with those of the natural gas fuelled power plants. The BIGGT in its turn shows a cost of electricity 29 percent higher than its natural gas and externally fired counterparts (US$0.09/kWh) counterparts. The method used to work out the best investment - the required revenue (RR) method - demonstrated that the EFGT is again comparable with the NGGT cycle, with its RR being only 7 percent higher. The BIGGT cycle shows a higher RR due to its costly gasification/cleaning system. The minimisation of the exergy destruction ratio indicates that little improvement would be achieved after the reduction of this parameter, and a penalty - an 85 percent increase in the cost of electricity - must be paid. The environmental advantage of the biomass-fuelled cycles over the natural gas cycle is clear, making these systems very promising as low emissions alternatives. Both BIGGT and EFGT cycles presented very low CQ2 emissions. Regarding NO., emissions, the EFGT cycle has the lowest rates, whereas the BIGGT has the highest.

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