Browsing by Subject "Gasification"
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Item Analysis of power generation processes using petcoke(2009-05-15) Jayakumar, RamkumarPetroleum coke or petcoke, a refinery byproduct, has generally been considered as an unusable byproduct because of its high sulfur content. However energy industries now view petcoke as a potential feedstock for power generation because it has higher carbon content than other hydrocarbons like coal, biomass and sewage residue. This gives petcoke a great edge over other feedstocks to generate power. Models for the two most common processes for power generation, namely combustion and gasification, were developed using Aspen Plus steady state chemical process simulator. Overall plant layouts for both processes were developed by calculating the heat and mass balance of the unit operations. After conducting wide sensitivity analysis, results indicate that one ton of petcoke feedstock can generate up to 4 MW of net available power. Both processes have rates of return greater than 30%, although gasification offers a slightly more attractive opportunity than combustion.Item Coal gasification in China : policies, innovation, and technology transfer(2013-05) Dai, Yue; Rai, VarunWith 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 industriesa major user of coal and significant contributor to GHG and other emissions in Chinathis 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.Item Development of a Segregated Municipal Solid Waste Gasification System for Electrical Power Generation(2013-04-11) Maglinao, Amado LatayanGasification technologies are expected to play a key role in the future of solid waste management since the conversion of municipal and industrial solid wastes to a gaseous fuel significantly increases its value. Municipal solid waste (MSW) gasification for electrical power generation was conducted in a fluidized bed gasifier and the feasibility of using a control system was evaluated to facilitate its management and operation. The performance of an engine using the gas produced was evaluated. A procedure was also tested to upgrade the quality of the gas and optimize its production. The devices installed and automated control system developed was able to achieve and maintain the set conditions for optimum gasification. The most important parameters of reaction temperature and equivalence ratio were fully controlled. Gas production went at a rate of 4.00 kg min-1 with a yield of 2.78 m3 kg-1 of fuel and a heating value (HV) of 7.94 MJ Nm-3. Within the set limits of the tests, the highest production of synthesis gas and the net heating value of 8.97 MJ Nm-3 resulted from gasification at 725?C and ER of 0.25 which was very close to the predicted value of 7.47 MJ Nm-3. This was not affected by temperature but significantly affected by the equivalence ratio. The overall engine-generator efficiency at 7.5 kW electrical power load was lower at 19.81% for gasoline fueled engine compared to 35.27% for synthesis gas. The pressure swing adsorption (PSA) system increased the net heating value of the product gas by an average of 38% gas over that of inlet gas. There were no traces of carbon dioxide in the product gas indicating that it had been completely adsorbed by the system. MSW showed relatively lower fouling and slagging tendencies than cotton gin trash (CGT) and dairy manure (DM). This was further supported by the compressive strength measurements of the ash of MSW, CGT and DM and the EDS elemental analysis of the MSW ash.Item Fixed Bed Counter Current Gasification of Mesquite and Juniper Biomass Using Air-steam as Oxidizer(2012-11-27) Chen, Wei 1981-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%).Item Fixed Bed Countercurrent Low Temperature Gasification of Dairy Biomass and Coal-Dairy Biomass Blends Using Air-Steam as Oxidizer(2010-10-12) Gordillo Ariza, GerardoConcentrated animal feeding operations such as cattle feedlots and dairies produce a large amount of manure, cattle biomass (CB), which may lead to land, water, and air pollution if waste handling systems and storage and treatment structures are not properly managed. However, the concentrated production of low quality CB at these feeding operations serves as a good feedstock for in situ gasification for syngas (CO and H2) production and subsequent use in power generation. A small scale (10 kW) countercurrent fixed bed gasifier was rebuilt to perform gasification studies under quasisteady state conditions using dairy biomass (DB) as feedstock and various air-steam mixtures as oxidizing sources. A DB-ash (from DB) blend and a DB-Wyoming coal blend were also studied for comparison purposes. In addition, chlorinated char was also produced via pure pyrolysis of DB using N2 and N2-steam gas mixtures. The chlorinated char is useful for enhanced capture of Hg in ESP of coal fired boilers. Two main parameters were investigated in the gasification studies with air-steam mixtures. One was the equivalence ratio ER (the ratio of stochiometric air to actual air) and the second was the steam to fuel ratio (S:F). Prior to the experimental studies, atom conservation with i) limited product species and ii) equilibrium modeling studies with a large number of product species were performed on the gasification of DB to determine suitable range of operating conditions (ER and S:F ratio). Results on bed temperature profile, gas composition (CO, CO2, H2, CH4, C2H6, and N2), gross heating value (HHV), and energy conversion efficiency (ECE) are presented. Both modeling and experimental results show that gasification under increased ER and S:F ratios tend to produce rich mixtures in H2 and CO2 but poor in CO. Increased ER produces gases with higher HHV but decreases the ECE due to higher tar and char production. Gasification of DB under the operating conditions 1.59less than0.8 yielded gas mixtures with compositions as given below: CO (4.77 - 11.73 %), H2 (13.48 - 25.45%), CO2 (11-25.2%), CH4 (0.43-1.73 %), and C2H6 (0.2- 0.69%). In general, the bed temperature profiles had peaks that ranged between 519 and 1032 degrees C for DB gasification.Item Gasification of Low Ash Partially Composted Dairy Biomass with Enriched Air Mixture(2012-02-14) Thanapal, Siva SankarBiomass is one of the renewable and non-conventional energy sources and it includes municipal solid wastes and animal wastes in addition to agricultural residue. Concentrated animal feeding operations produce large quantities of cattle biomass which might result in land and water pollution if left untreated. Different methods are employed to extract the available energy from the cattle biomass (CB) which includes co-firing and gasification. There are two types of CB: Feedlot biomass (FB), animal waste from feedlots and dairy biomass (DB), animal waste from dairy farms. Experiments were performed in the part on gasification of both FB and DB. Earlier studies on gasification of DB with different steam-fuel ratios resulted in increased production of hydrogen. In the present study, dairy biomass was gasified in a medium with enriched oxygen percentage varying from 24% to 28%. The effect of enriched air mixture, equivalence ratio and steam-fuel ratio on the performance of gasifier was studied. Limited studies were done using a mixture of carbon dioxide and oxygen as the gasification medium and also a methodology was developed to determine the gasification efficiency based on mass and heat contents of gas. The results show that the peak temperature within the bed increases with increase in oxygen concentration in the gasification medium. Also carbon dioxide concentration in the mixture increases with corresponding decrease in carbon monoxide with increase in oxygen concentration of the incoming gasification medium. The peak temperature increased from 988?C to 1192?C as the oxygen concentration increased from 21% to 28% at ER=2.1. The upper limit on oxygen concentration is limited to 28% due to high peak temperature and resulting ash agglomeration. Higher heating value (HHV) of the gases decreases with increase in equivalence ratio. The gases produced using carbon dioxide and oxygen mixture had a higher HHV when compared to that of air and enriched air gasification. Typically the HHV of the gases increased from 2219 kJ/m? to 3479 kJ/m? when carbon dioxide and oxygen mixture is used for gasification instead of air at ER=4.2 in the absence of steam.Item Instrumentation and Evaluation of a Pilot Scale Fluidized Bed Biomass Gasification System(2009-12-04) Maglinao, Amado LA pilot scale fluidized bed biomass gasifier developed at Texas A&M University in College Station, Texas was instrumented with thermocouples, pressure transducers and motor controllers for monitoring gasification temperature and pressure, air flow and biomass feeding rates. A process control program was also developed and employed for easier measurement and control. The gasifier was then evaluated in the gasification of sorghum, cotton gin trash (CGT) and manure and predicting the slagging and fouling tendencies of CGT and manure. The expected start-up time, operating temperature and desired fluidization were achieved without any trouble in the instrumented gasifier. The air flow rate was maintained at 1.99 kg/min and the fuel flow rate at 0.95 kg/min. The process control program considerably facilitated its operation which can now be remotely done. The gasification of sorghum, CGT and manure showed that they contained high amounts of volatile component matter and comparable yields of hydrogen, carbon monoxide and methane. Manure showed higher ash content while sorghum yielded lower amount of hydrogen. Their heating values and gas yields did not vary but were considered low ranging from only 4.09 to 4.19 MJ/m3 and from 1.8 to 2.5 m3/kg, respectively. The production of hydrogen and gas calorific values were significantly affected by biomass type but not by the operating temperature. The high values of the alkali index and base-to acid ratio indicated fouling and slagging tendencies of manure and CGT during gasification. The compressive strength profile of pelleted CGT and manure ash showed that the melting (or eutectic point) of these feedstock were around 800 degrees C for CGT and 600 degrees C for manure. Scanning electron microscopy (SEM) images showed relatively uniform bonding behavior and structure of the manure ash while CGT showed agglomeration in its structure as the temperature increased. The instrumentation of the fluidized bed gasifier and employing a process control program made its operation more convenient and safe. Further evaluation showed its application in quantifying the gasification products and predicting the slagging and fouling tendencies of selected biomass. With further development, a full automation of the operation of the gasifier may soon be realized.Item Modeling, Optimization and Economic Evaluation of Residual Biomass Gasification(2012-02-14) Georgeson, AdamGasification 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.