Computational modeling was completed on a simplified downdraft gasifier to be implemented at the University of Iowa Oakdale Power Plant. The model was created in Gambit and exported to FLUENT, a computational fluid dynamics software program, in order to process non-premixed combustion on biomass fuels and better understand the combustion and gasification zones. The fuels were modeled as coal particles with the empirical formula of the biomass found from off-site proximate and ultimate analyses. The coal model inherent to FLUENT contains the same chemicals (C, H, N, O, and S) as the biomass tested, so this model was determined to be accurate. The model was tested for varying packing densities, oxidizer inlet velocities and fuel type to describe the effects on the combustion zone. It was concluded that packing densities around 0.5 with oxidizer inlet velocities less than 5 m/s would be ideal for modeling wood. The temperature distribution was the most even in this environment and produced a large rich fuel combustion (RFC) zone where gasification and pyrolysis could occur. The different fuels were found to have similar temperature and mean mixture fraction patterns, although the maximum temperatures attained were very different (1080K for seed corn and 678K for wood), the wood showed a greater area of RFC for gasification and pyrolysis.

Thermal gasification of biomass is being considered as one of the most promising technologies for converting biomass into gaseous fuel. Here we present results of gasification, using an adiabatic bed gasifier with air, steam as gasification medium, of mesquite and juniper. From Thermo-gravimetric analyses the pre-exponential factor (B) and activation energy of fuels for pyrolysis were obtained using single reaction models (SRM) and parallel reaction model (PRM). The single reaction model including convention Arrhenius (SRM-CA) and maximum volatile release rate model (SRM-MVR). The parallel reaction model fits the experimental data very well, followed by MVR. The CA model the least accurate model. The activation energies obtained from PRM are around 161,000 kJ/kmol and 158,000 kJ/kmol for juniper and mesquite fuels, respectively. And, the activation energies obtained from MVR are around100,000 kJ/kmol and 85,000 kJ/kmol for juniper and mesquite fuels, respectively. The effects of equivalence ratio (ER), particle size, and moisture content on the temperature profile, gas composition, tar yield, and higher heating value (HHV) were investigated. For air gasification, when moisture increased from 6% to 12% and ER decreased from 4.2 to 2.7, the mole composition of the dry product gas for mesquite varied as follow: 18-30% CO, 2-5% H2, 1-1.5% CH4, 0.4-0.6% C2H6, 52-64% N2, and 10-12% CO2. The tar yield shows peak value (150 g/Nm^3) with change in moisture content between 6-24%. The tar collected from the gasification process included light tar and heavy tar. The main composition of the light tar was moisture. The chemical properties of heavy tar were determined. For air-steam gasification, H2 rich mixture gas was produced. The HHV of the mesquite gas increased first when S: F ratio increased from 0.15 to 0.3 and when the S: F ratio increased to 0.45, HHV of the gas decreased. Mesquite was blended with the Wyoming Powder River Basin (PRB) coal with ratio of 90:10 and 80:20 in order to increase the Tpeak and HHV. It was found that the Tpeak increased with the increase of PRB coal weight percentage (0% to 20%).

Gasification is a thermo-chemical process which transforms biomass into valuable synthesis gas. Integrated with a biorefinery it can address the facility’s residue handling challenges and input demands. A number of feedstock, technology, oxidizer and product options are available for gasification along with combinations thereof. The objective of this work is to create a systematic method for optimizing the design of a residual biomass gasification unit. In detail, this work involves development of an optimization superstructure, creation of a biorefining scenario, process simulation, equipment sizing & costing, economic evaluation and optimization. The superstructure accommodates different feedstocks, reactor technologies, syngas cleaning options and final processing options. The criterion for optimization is annual worth. A biorefining scenario for the production of renewable diesel fuel from seed oil is developed; gasification receives the residues from this biorefinery. Availability of Soybeans, Jatropha, Chinese Tallow and woody biomass material is set by land use within a 50-mile radius. Four reactor technologies are considered, based on oxidizer type and operating pressure, along with three syngas cleaning methods and five processing options. Results show that residual gasification is profitable for large-scale biorefineries with the proper configuration. Low-pressure air gasification with filters, water-gas shift and hydrogen separation is the most advantageous combination of technology and product with an annual worth of $9.1 MM and a return on investment of 10.7 percent. Low-pressure air gasification with filters and methanol synthesis is the second most advantageous combination with an annual worth of $9.0 MM. Gasification is more economic for residue processing than combustion or disposal, and it competes well with natural gas-based methanol synthesis. However, it is less economic than steam-methane reforming of natural gas to hydrogen. Carbon dioxide credits contribute to profitability, affecting some configurations more than others. A carbon dioxide credit of $33/t makes the process competitive with conventional oil and gas development. Sensitivity analysis demonstrates a 10 percent change in hydrogen or electricity price results in a change to the optimal configuration of the unit. Accurate assessment of future commodity prices is critical to maximizing profitability.

With its burgeoning energy consumption and emissions of greenhouse gases (GHGs), China is central to addressing the problem of climate change. As the world leader in GHG emissions for years, China is under tremendous international pressure in the fight against climate change. Focusing on China's coal-to-chemicals industriesa major user of coal and significant contributor to GHG and other emissions in Chinathis thesis seeks to explain how national policies have affected the deployment of coal gasification in China. The data and information for this thesis were mainly collected from interviews with experts from Chinese and U.S. companies, relevant government reports, and other Internet sources. First, I present the current state of energy consumption and the development status of related industries that are applying gasification technologies in China. I then present related policies and pilot projects for the development of gasification technology and analyze how these affect the Chinese gasification market. I analyze factors that have promoted a change in the mode of partnership between foreign firms and Chinese firms (from licensing contracts to joint ventures), and how joint ventures are enabling gasification technology transfer currently. Finally, I argue how the underlying conditions create drivers that promote gasification technology transfer despite China’s weak IP regime. / text

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Biomass gasification is a technology under development that presents a means of generating hydrogen using renewable energy. While many forms of gasification have been investigated, steam gasification using a dual fluidised bed (DFB) reactor has been shown to efficiently produce high hydrogen content producer gas. The aims of this research were to increase the hydrogen yield from the 100kW DFB gasifier installed at the University of Canterbury, and thereby improve the current state of the art of gasifier operation. Calcium carbonate-based minerals such as calcite and dolomite were shown to be able to improve hydrogen production by absorbing carbon dioxide in the producer gas, promoting the water gas shift reaction. Bed material mixtures of olivine and calcite were the most effective at improving gasifier performance, increasing producer gas yield by 20%, increasing cold gas efficiency by 6% and increasing hydrogen yield by 85%. In addition, the carbon monoxide content was reduced and the ratio of hydrogen to carbon monoxide in the producer gas was ideal for Fisher-Tropsch synthesis of liquid fuels.

A series of experiments was conducted to investigate the potential influence of pre- and post adding of catalysts to a demineralized coal char. The catalysts were chosen according to yield better catalytic activity and be inexpensive. CO2 gasification was conducted on the samples in a temperature range of 500 °C to 900 °C. The coal chosen was a high-inertinite, high-ash, Highveld bituminous coal. The catalysts chosen were sodium carbonate, potassium carbonate, and a mixture of the two catalysts. Different methods were used to investigate the factors influencing the reactivity of the demineralized coal char, and the extent of the influence from the catalysts. Proximate analysis, ultimate analysis and ash yields were conducted on the starting material to determine the change the demineralization had on the coal. Ash fusion temperatures of the samples were also obtained. The results indicated that demineralization lowered the ash content, as well as the ash fusion temperatures, but the ultimate analysis showed consistency in both sets of samples. Mass losses obtained during the thermal treatment experiments under CO2 atmosphere showed an increase in mass loss in the order of samples without addition of catalysts to the smallest amount of addition. Potassium carbonate showed the largest increase in mass loss during CO2 thermal treatment, together with the mixture of the two catalysts. Samples with pre-added catalysts also had a larger mass loss than samples with post-added catalysts. According to the XRD and QEMSCAN results, some potassium species are retained in the ash, which is confirmed by XRF results. The XRF results also showed that the amount of alkali species retained is quite large. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2011

Thesis--University of Missouri, School of Mines and Metallurgy, 1912. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed April 16, 2009)

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains x, 164 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 119-121).