An extensive study of intrinsic and extrinsic factors on biomass pyrolysis reactions is needed if valuable hydrocarbon gases are to be produced from pyrolysis of biomass. In the first phase of this study a spent coffee waste material was pyrolysed in a stainless steel batch reactor at 500 to 900°C with both N₂ and H₂ carrier gases. The use of H₂ gas did not affect the product distribution. Yields of pyrolysis gas products reached 61 and 74 wt% of the feed at 900°C for N₂ and H₂ carrier gases. Corresponding mass balance closures were obtained at 86 and 98 wt% of the feed. Catalytic effect of the stainless steel wall was confirmed. Maximum conversion of CO was found at pyrolysis zone temperature of 700°C. Pyrolysis experiments with spent coffee performed in a quartz (inert) batch reactor proved that the carrier gas had negligible influence on the primary pyrolysis product distribution. Pyrolysis with K₂CO₃ at 650, 700, and 800°C, showed catalysis of cracking reactions of pyrolysis tars and the water-gas shift reaction. Copyrolysis of biomass materials and coals were performed in the quartz reactor with the objective of producing a higher hydrocarbon content gas product. Copyrolysis of spent coffee and lignite coal at 800°C in a hydrogen atmosphere resulted in gas production of more than 45 wt% of the feed, compared with only 27 wt% for pure coal sample. Increases in production of CH₄ and C₂H₄ were 15.9 wt% and 21.3 Wt%. For copyrolysis with sub-bituminous coal, these synergistic increases were 36.5 wt% and 23.9 wt%. In the final phase of this research, a fluidized bed reactor was used to study hydropyrolysis of cellulose, spent coffee, aspen-poplar, bagasse and lignite coal in presence of sand (inert medium), ã-alumina catalyst, Engelhard US-260 (a silica alumina catalyst), 10 wt% nickel-ã-alumina, 10 wt% cobalt-ã-alumina and a 40 wt% nickel-refractory support catalyst. Over the temperature range of 500 to 600°C, the 10 wt% nickel catalyst was most effective in conversion of biomass. Overall it was found that the combination of cellulose with 10 wt% Ni catalyst at 550°C was the optimum catalyst-feed system for conversion of carbon content of biomass to methane. In this case the yield of CH₄ was 46.7 wt% of cellulose. Rate constants for (primary) pyrolysis, (secondary) tar-cracking and (tertiary) hydrogenation reactions at 550°C were determined. Rate constants for the above mentioned reactions were estimated to be k₁=2.88 s^-1 (pyrolysis model), k₁=2.88 and k₂=1.31 s^-1 (pyrolysis-cracking model), and k₁=2.88, k₂=13.1 and k₃=12.96 s^-1 (pyrolysis-cracking-hydrogenation model).

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Sujit Banerjee; Committee Co-Chair: Wm. James Frederick, Jr.; Committee Member: John D. Muzzy; Committee Member: Kristiina Iisa; Committee Member: Preet Singh. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Biomass is among the primary alternative energy sources that supplements the fossil fuels to meet today’s energy demand. Gasification is an efficient and environmental friendly technology for converting the energy content in the biomass into a combustible gas mixture, which can be used in various applications. The composition of this gas mixture varies greatly depending on the gasification agent, gasifier design and its operation parameters and can be classified as low and medium LHV gasified biomass. The wide range of possible gas composition between each of these classes and even within each class itself can be a challenge in the combustion for heat and/or power production. The difficulty is primarily associated with the range in the combustion properties that may affect the stability and the emission levels. Therefore, this thesis is intended to provide data of combustion properties for improving the operation or design of atmospheric combustion devices operated with such gas mixtures. The first part of this thesis presents a series of experimental work on combustion of low LHV gasified biomass (a simulated gas mixture of CO/H2/CH4/CO2/N2) with variation in the content of H2O and tar compound (simulated by C6H6). The laminar flame speed, lean blowoff limit and emission levels of low LHV gasified biomass based on the premixed combustion concept are reported in paper I and III. The results show that the presence of H2O and C6H6 in gasified biomass can give positive effects on these combustion parameters (laminar flame speed, lean blowoff limit and emission levels), but also that there are limits for these effects. Addition of a low percentage of H2O in the gasified biomass resulted in almost constant laminar flame speed and combustion temperature of the gas mixture, while its NOx emission and blowoff temperature were decreased. The opposite condition was found when H2O content was further increased. The blowoff limit was shifted to richer fuel equivalence ratio as H2O increased. A temperature limit was observed where CO emission could be maintained at low concentration. With C6H6 addition, the laminar flame speed first decreased, achieved a minimum value, and then increased with further addition of C6H6. The combustion temperature and NOx emission were increased, CO emission was reduced, and blowoff occurs at slightly higher equivalence ratio and temperature when C6H6 content is increased. The comparison with natural gas (simulated by CH4) is also made as can be found in paper I and II. Lower laminar flame speed, combustion temperature, slightly higher CO emission, lower NOx emission and leaner blowoff limit were obtained for low LHV gas mixture in comparison to natural gas. In the second part of the thesis, the focus is put on the combustion of a wide range of gasified biomass types, ranging from low to medium LHV gas mixture (paper IV). The correlation between laminar flame speed or lean blowoff limit and the composition of various gas mixtures was investigated (paper IV). It was found that H2 and content of diluents have higher influence on the laminar flame speed of the gas mixture compared to its CO and hydrocarbon contents. For lean blowoff limit, the diluents have the greatest impact followed by H2 and CO. The mathematical correlations derived from the study can be used to for models of these two combustion parameters for a wide range of gasified biomass fuel compositions. / <p>QC 20130411</p>

No description available.

In 2004 the Department of Chemical and Process Engineering (CAPE) at University of Canterbury began a programme to investigate using biomass gasification integrated combined cycle (BIGCC) technology to convert waste products and residues to useful energy for the wood processing sector. This research was conducted as a part of Objective Two of the programme to develop gasification and gas cleaning technology. This project involved commissioning and characterising the operation of the Fast Internal Circulating Fluidised Bed (FICFB) gasifier and comparing its operation with a more conventional up-draught process owned and operated by Page Macrae in Mount Manganui. The wood derived gas composition of each gasifier was measured using gas chromatography and these compositions were used to calculate lower heating values (LHV). The CAPE FICFB gasifier has proven to produce successfully a gas with a lower heating value of 10400-12500 kJ/Nm³. The Page Macrae gasification process produces a low quality gas with a lower heating value of 4100-5100 kJ/Nm³. This is much lower than the CAPE gasifier since the oxidant used in the up-draught gasification process is air and the product gas is diluted by nitrogen. The Page Macrae gasification system combusts wood derived gas to produce steam for a laminar veneer lumber (LVL) processing plant so gas quality and heating value are less important than in electrical production applications. Reducing the nitrogen content of the CAPE product gas will increase the heating value of the gas. Improvements to the boiler system will reduce the amount of air required for gasification and hence reduce the nitrogen content. Further improvements to gas quality can be gained from a change in the fuel feed point from on top of the gasification column's bubbling fluidised bed to the side of the bubbling fluidised bed. The CAPE gasifier is much more complicated and requires specialised operators but produces a gas suitable for gas engine and gas turbine technology. Overall the CAPE gasification system is more suited to BIGCC applications than the Page Macrae process.

The purpose of this research was to investigate the feasibility of installing gasification based combined heat and power plants in the New Zealand wood processing industry. This is in accordance with Objective Four of the BIGAS Consortium. This thesis builds on previous work on Objective Four (Rutherford, 2006) where integration into MDF (Medium Density Fibreboard) was investigated. The previous research identified the most suitable form of combined heat and power was a BIG-GE (Biomass Integrated Gasification Gas Engine) process, due to both lower capital investment and overall breakeven electricity production cost. This technology has therefore been adopted, and the investigation has been carried further in this research to incorporate integration into sawmills and LVL (Laminated Veneer Lumber) plants. It is recognised, however, especially when reviewing overseas successes and failures, that the base economics are only one factor in the feasibility of a plant. The research, therefore, has moved further to investigate New Zealand policy, the power market, lower capital alternatives and novel methods of integration. The conclusion of the study is gasification based combined heat and power plants in the New Zealand wood processing industry can be equal or better in economic terms than other forms of renewable generation, however, the application is very niche. Lower capital cost alternatives, stable and low priced biomass feed and a favourable power market in regards to distributed generation is key to the viability of such a plant. Government policy is favourable towards biomass gasification due to the target of 90% electrical generation by renewable resources by 2025. Distributed generation is also encouraged in the Government’s forward strategy. However, the technology has advanced further overseas due to capital grants and a premium paid for ‘green’ electricity. While the technology may be economic in its own right, active government support would lower the perceived risk increasing the likelihood of an investor taking interest in an initial project.

Biomass, as a renewable energy resource, can be utilized to generate chemicals, heat, and electricity. Compared with biomass combustion, biomass gasification is more eco-friendly because it generates less amount of green gas (CO2) and other polluting gases (NOx and SO2). This research is focused on biomass gasification using a circulating fluidized bed. In the gasifier, fully fluidized biomass particles react with water vapor and air to generate syngas (CO and H2). A comprehensive model, consisting of three modules, hydrodynamics, mass transfer and energy transfer modules, is built to simulate this process using ANSYS Fluent software and C programming language. In the hydrodynamics module, the k-epsilon turbulence equations are coupled with the fluctuating energy equation to simulate gas-particle interaction in the turbulent flows occurring in the riser. In the mass transfer and energy transfer modules, heat transfer and mass transfer in turbulent flows are simulated to solve for the profiles of temperature and species concentration in the gasifier. The impacts of thermal radiation, water gas shift reaction (WGS), equivalence ratio (ER), and char combustion product distribution coefficient are also investigated to gain deeper understanding of biomass gasification process.

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 137-140).

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 79-80).

Thesis (M.S.)--Humboldt State University, 2008. / Includes bibliographical references (leaves 114-118). Also available via Humboldt Digital Scholar.