Numerical Simulation And Experimental Research On Co-Combustion Characteristics Of Low Calorific Value Coal Bed Methane And Coal Gangue In Circulating Fluidized Bed

China's annual heavily emissions gangue, which is about ten percent of coal production, has aggregated piled up billions of tons at present. Long-term stockpiling of coal gangue needs amounts of land and leads to air and water pollution. Coal bed methane(CBM) resources in China is about 10 trillion cubic meter, of which proved reserves is 102.3 billion cubic meter and recoverable reserves is 470 billion cubic meter. Now, only a small part of CBM is used. Therefore, the efficient utilization of coal gangue and CBM is able to save resources and reduce greenhouse gas emission.It is hot topic at China and abroad that using fluidized bed to utilize low-grade fuel. In present, there are few systematic researchs on the co-combustion with different phases of the fuel in circulating fluidized bed. So that, based on the in-depth study of pyrolysis and combustion characteristics of coal gangue , the simulation and experimental research of multi-fluid flow and co-combustion characteristics of CBM and coal gangue were done. The study of different phases fuel in CFB the flow,heat transfer and combustion characteristics lays a solid theoretical foundation for further developing the CBM and coal gangue CFB firing technology.The experiments of the pyrolysis and combustion of coal gangue in different atmospheres were done by thermal analyser. The ignition of coal gangue, activation energy and other parameters were obtained. Physical and math models of burner adapting low calorific thermal value CBM combustion were built for the first time. The burner has been optimum designed by numerical simulation methods and the results were verified by experimentation. The physical and mathematical models which described the mixing burning of different phases fuel in CFB were established based on the subsistent 45t CFB for the first time. Numerical simulations were done for mixing burning of CBM and coal gangue. Flow field, temperature and concentration changes of CO2 and CH₄ were analyzed in depth. The best work condition was obtained.The renovation of a 45t CFB for mixing burning of CBM was carried out based on the results of numerical simulations for the first time. The cold and hot tests of the boiler were done. The variation laws of temperature in vertical direction, the concentration of CH₄ at the outlet of the furnace and boiler efficiency were test. The results have established the theory bases for the development of technology of mixing burning of coal bed methane and coal gangue in CFB. The pyrolysis and combustion of coal gangue kinetics characteristics study shows that the higher the volatile content in coal gangue, the more prone to thermal decomposition; final pyrolysis temperature increased, the pyrolysis of coal gangue weight loss rate increases; Larger sample size,the higher characteristic temperature pyrolysis, pyrolysis mass loss rate decreased; heating rate increases, DTG peak increased, weight loss reduced;the characteristics of high ash coal gangue lead to poor performance of its burn; combustion of coal gangue comprehensive close relationship with the volatile content, the higher the volatile, integrated combustion performance is better.Numerical simulation study on low-calorific value coal bed methane burner indicates that burning efficiency of part-premixed burner is highest, burning efficiency of diffusion burner is lowest, premixed burner is in between part-premixed burner and diffusion burner. Partially premixed burner has good jet rigid, combustion temperature is relatively high, in general, part of the premixed burner with gradually expanding, and the diffusion angle of 6.88°has a relatively high combustion efficiency.Low concentrations of methane burner cold and hot test showed that: diffusion burner pressure loss is minimum, fully premixed burner pressure loss is very bigt. Partially premixed burner flame temperature is maximum, fully premixed burner flame length is the shortest, diffusion burner flame length is longest. Comparing experimental results with the simulation results, we can see a good agreement between both, partially premixed burner has the best overall performance.Low calorific value coal methane and coal gangue CFB combustion simulation results show that when the ratio of coal gangue and coal bed methane is 10:0, the overall speed of the combustion chamber is relatively evenly distributed, with the increasing of coal bed methane, flow deflection increase, when the co-combustion ratio is 6:4, the degree of flow deflection is the highest. When all the fuel is coal gangue, the overall temperature of the combustion chamber is relatively evenly distributed. When the coal bed methane is injected, flow field deflection occurs, resulting in local high temperature. With the increasing of coal methane, the peak of the concentration of CH₄ occurs when the height away from the air distribution plate 5m,With the height increasing of the combustion chamber, CH₄ concentration significantly reduced. Comprehensive simulation results show that the ratio of coal gangue and coal bed methane is improper when more than 8:2, a beneficial use of primary and secondary air ratio 6:4. The experimental studies of coal bed methane and coal gangue co-combustion in Circulating fluidized bed show that air flow resistance of the air distribution plate increases with air volume increasing. The resistance characteristic curve of the air distribution plate is basically similar to a quadratic curve. With the increasing flow of air, an inflection point can be seen on the the pressure curve clearly, and the inflection point corresponds to the critical flow air volumeo f the air. It can be conclused from the thermal test data of high temperature in dense region, low and unifom temperature in dilute phase region that unburned particles in dense area can continue combustion in dilute phase region. With the increasing of the ratio of methane co-combution from 10:0 to 6:4, boiler efficiency increase from 82.6% to 84.1%.The study of the co-combustion characteristics of the coal bed methane and coal gangue in CFB is useful for further research and development relative technology. It has a very broad application prospect in comprehensive utilization of resources and environmental protection.