Study On Underground Coal Catalytic Gasification Features And Technology

Due to the restraining factors for the underground coal gasification, such as the coal occurrence, geologic structure and hydrological conditions, etc., gas components, heating value, and gas production stability cannot reach theover-ground coal gasification efficiency, and these are restraining the commercialization of the technology. The research is to utilize the catalytic gasification technology to underground coal gasification to increase the quality specifications of raw gas. The test is mainly based on three typical coal samples for the study object, which has designed with multi-function underground catalyst loading device and two approaches of underground catalyst injection. It selects alkali metals and alkaline-earth metals as the main catalyst, and employs horizontal fixed bed reactor for the systemic research of chemical reaction characteristics, dynamics and thermodynamics during the coal catalytic pyrolysis and coke catalytic gasification, and makes further analysis of catalytic mechanism. Finally, it utilizes pilot test unit and multi-nozzle injection gasifier featured with linear type distribution for underground coal catalytic gasification verification tests on the anthracite seam.From the test result, it reveals that underground catalyst injection approach can catalyze the coal reaction to increase the coal gas quality and gasification reaction rate. It’s summarized as below:The catalyst increases the yield of gaseous products and H2content during pyrolysis. Based on specific surface area test, XRD and SEM analysis, the catalyst can extend specific surface area of anthracite and defer the graphitization process of anthracite. After catalysis, it produces more pore channels on the coke surface than the previous coal and the coke, the surface roughness is increased, and the reactivity is enhanced.Underground catalytic gasification can increase coke carbon conversion rate, and increase the effective gas composition content. Via different mathematical models and their modifications, with combination of Arrhenius equation, it draws the conclusion that:Ca(OH)2can increase the apparent reaction rate by1.34to1.41times compared to pre-catalysis for coke oxygen-enriched and steam gasification reaction, and the apparent activation energy can decrease by31to33kJ·mol-1. And, activation energy decreases by10.44to16.10kJ·mol-1via adding compound catalyst Ca(OH)2-Na2CO3compared to adding Ca(OH)2; moreover, Ea has linear compensation correlation with pre-exponential factor A.When it utilizes the multi-nozzle injection gasifier featured with linear type distribution and different processes to make catalytic gasification, the coal gas composition is much closer to the thermodynamic equilibrium of theoretical gas, the gasification efficiency and combustion area are superior to normal gasification; and, catalytic gasification has synergistic effects on the desulfuration and the decoking of the raw coal gas from the underground gasifier. Catalytic ignition can increase the temperature escalating rate of the coal seam; and, temperature variation trend and data stimulation process are nearly in consistency.