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Call number: LD2668 .T4 1979 H69 / Master of Science

Biomass gasification is a promising technology for conversion of various biomass feedstocks to producer gas for subsequent production of fuels and chemicals. A dual fluidised bed (DFB) steam gasifier is used in the present research to produce the producer gas for Fischer-Tropsch (FT) liquid fuel synthesis. However, NH3 and H2S gases in the producer gas remain an issue to be resolved because they are poisonous to the catalysts employed in the FT reactor. To remove NH3 and H2S, two methods were investigated in this research: (1) primary measures which were employed in the DFB steam gasifier including process optimisation and application of bed materials for catalytic NH3 decomposition and H2S adsorption; and (2) secondary measures or downstream cleaning methods after the gasifier. The combination of the primary measures and the secondary measures is an effective way to remove the NH3 and H2S in the producer gas from gasification process. Studies on the primary measures were divided into two parts. In the first part, in situ reduction of NH3 and H2S in biomass producer gas from the DFB steam gasifier was performed. The primary measures consisted of optimisation of operation conditions and application of bed materials. The main operation conditions in the DFB steam gasifier studied were gasification temperature, steam to fuel (S/F) ratio, and mean gas residence time (f). The bed materials tested include silica sand, iron sand (ilmenite), and calcined olivine sand. For the second part of the primary measures, an influence of the lignite to fuel (L/F) ratio on NH3 and H2S concentrations and conversions in co-gasification of blended lignite and wood pellets in the DFB steam gasifier was investigated. Experiments were performed in the DFB steam gasifier at 800C with blended lignite and radiata pine wood with the L/F ratio ranging from 0% to 100%. It was found that all of the studied parameters including gasification temperature, S/F ratio, f, bed material, and L/F ratio significantly influenced the NH3 and H2S concentrations and conversions in the producer gas. For the secondary measures, a novel hot catalytic reactor and adsorber was developed in the present research for the simultaneous removal of NH3 and H2S. In a hot gas reactor operated at 500-800C and under atmospheric pressure, titanomagnetite was tested for NH3 and H2S removal by hot catalytic NH3 decomposition and H2S adsorption reactions. Titanomagnetite was tested with three different gas streams including 2,000 ppmv NH3 in Ar, 2,000 ppmv NH3 and 230 ppmv H2S in Ar, and 2,000 ppmv NH3 and 230 ppmv H2S in simulated biomass producer gas. From the experimental results, it was discovered that ferrite (α-Fe) readily formed by the H2 reduction of titanomagnetite has shown almost complete NH3 decomposition (100%) in Ar gas at 700 and 800C. The presence of H2S in the gas mixture of NH3 and Ar slightly reduced the catalytic activity for NH3 decomposition at 700 and 800C (>96%) and H2S adsorption of more than 98% could be achieved at the same temperature range. However, in the test with simulated biomass producer gas, 60% NH3 decomposition and 9% H2S adsorption were obtained at 800C, whereas 40% NH3 decomposition and 80% H2S adsorption were obtained at 500C. The decrease of NH3 decomposition and H2S adsorption at 800C in simulated biomass producer gas could be due to the high content of H2 (45 vol%) in the feed gas that favours the reverse reactions of NH3 decomposition and H2S adsorption, the increased surface coverage of the active α-Fe phase by adsorbed hydrogen, and the competition of α-Fe for the reverse water-gas shift reaction. Besides, it was discovered that the temperature significantly affected the removal of NH3 and H2S in simulated biomass producer gas and thus it needs to be optimised.

No description available.

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

The present work, where additional value-creating processes in existing combined heat and power (CHP) structures have been examined, is motivated by a political- and consumer-driven strive towards a bioeconomy and a stagnation for the existing business models in large parts of the CHP sector. The research is based on cases where the integration of flash pyrolysis for co-production of bio-oil, co-gasification for production of fuel gas and synthetic biofuels as well as leaching of extractable fuel components in existing CHP plants have been simulated. In particular, this work has focused on the CHP plants that utilize boilers of fluidized bed (FB) type, where the concept of coupling a separate FB reactor to the FB of the boiler forms an important basis for the analyses. In such dual fluidized bed (DFB) technology, heat is transferred from the boiler to the new rector that is operating with other fluidization media than air, thereby enabling other thermochemical processes than combustion to take place. The result of this work shows that broader operations at existing CHP plants have the potential to enable production of significant volumes of chemicals and/or fuels with high efficiency, while maintaining heat supply to external customers. Based on the insight that the technical preconditions for a broader operation are favourable, the motivation and ability among the incumbents in the Swedish CHP sector to participate in a transition of their operation towards a biorefinery was examined. The result of this assessment showed that the incumbents believe that a broader operation can create significant values for their own operations, the society and the environment, but that they lack both a strong motivation as well as important abilities to move into the new technological fields. If the concepts of broader production are widely implemented in the Swedish FB based CHP sector, this can substantially contribute in the transition towards a bioeconomy. / Bioeconomy has been identified to hold a great potential for reducing fossil fuel dependence and for maintaining and creating economic growth. Large parts of the combined heat and power (CHP) sector, which successfully have contributed in the transition towards a fossil free society, are at present facing stagnation. District heating actors are facing challenges due to warmer climate, better insulated buildings and competition from heat pumps. The forest industry where CHP plants supplies processes with heat is facing structural changes foremost in the graphic segments. The emerging bioeconomy and the stagnation for the existing business models in large parts of the CHP sector form the background for the examination of additional value-creating processes in the existing CHP structure presented in this thesis. The technical viability for integration of fast pyrolysis, gasification and leaching with existing CHP plants has been analysed as well as the motivation and ability of the CHP incumbents to participate in a transition towards the bioeconomy by developing their plants to biorefineries.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering Johannesburg, 29 August 2016 / This study discusses underground coal gasification (UCG) and the analysis thereof. Two main methods were used. The first is the Bond Equivalent Diagram, which gives an ideal of where operations should take place in relation to their coal and product gas compositions. This method was used to analyze several real life sites for their idealized and actual operations. The second consisted of a comparative exergy simulation study. This was done for an air-blown UCG plant with a downstream Fischer-Tropsch reactor and an oxygen-blown UCG plant with upstream air separation. The plants were analyzed by their overall exergy efficiency as well as their exergy outputs with respect to coal inputs (fuel). It was discovered that the air-blown simulation with downstream Fischer-Tropsch was the better choice from an exergy point of view due to it having higher efficiencies (1.5 for overall, 1.38 for fuel) as opposed to the oxygen-blown simulation (0.77 overall, 0.8 for fuel). This coupled with other design and safety factors led to the conclusion that the air-blown simulation was better. / MT2017

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 238-245. / by Mark Steven Dershowitz. / M.S.

Gasification is a process that converts organics or fossil fuel based material into syngas at high temperature under controlled amount of air. Gasification thus increases the practicality of using biomass as a renewable source of energy. The goal of this paper is to explore corn kernel gasification at the University of Iowa Oakdale pilot scale gasifier. The results of this paper consists of three parts; the temperature profile in the gasifier, gas analysis at 950F and 1050F, and bio char analysis. The temperature profile within the gasifier was obtained and studied; different temperature gasification zones were identified. Sample gases at 950F and 1050F were obtained and analyzed. It was seen that the syngas production (in volume) at 1050 F was 12.2% greater than that of 950F. A 37.4%, 27.1% and 38.3% increase in composition of H, CO and CH4 respectively was also observed. Ultimate analysis, proximate analysis, SEM and BET tests were carried on the corn bio char produced. From the ultimate and proximate analysis, it was observed that corn bio char was similar to activated carbon. Oakdale bio-char was compared with other processed powder bio char. It was observed that char produced from the Oakdale gasifier was more porous than powder bio-char, possibly making it a better soil amendment.