System Integration Research On Coal Partial Gasification And Semicoke Combustion

Coal is the primary energy source of China,Most of the coal consumed is usually used through a single combustion way. Coal staged conversion improve utilization ratio of coal source from staged utilization according to different reaction properties in different reaction stage,not only this technology is easy and feasible,the investment is low,but also it may solves source and energy problem effectively.A review on coal partial gasification technology and semickoe combustion technology for domestic and oversea is proceeded . On basis of this, a coal partial gasification and combustion multi-generation technology was put forward.In order to deeply know the different reaction properties in different reaction stage and analyze the effect on gasification and combustion for the physical factor, the kinetics experiment was carried out on coal pyrolysis,gasification,combustion and semicoke combustion with TGA. Research show that: reaction rate on gasification is low and high temperature and long residence time was needed for gasification reaction occurrence compared with combustion and pyrolysis ; Reaction rate for coal gasification and pyrolysis is accelerated with increase of heating rate; gasification reaction is affected deeply by ratio of coal to ash, Reaction rate firstly increases and then decreases with the increase on ratio of coal to ash, experiment show optimum ratio of coal to ash is existing.In order to make further research the effects for opration condition on coal gasification and semicoke character, a multifunctioanal test device for coal combustion and gasification was set up. A lot of experiment was conducted on it. Experiment on coal pyrolysis and gasification with different coal type, coal size and atmosphere has been made on it. emicoke character was analysed by nitrogen adsorption instrument. Experiment show that content of H₂,CO,CO₂,CH₄ increase with dense phase temperature increases in process of coal pyrolysis. Output of coal gas increases with ratio of gas to coal increased and gas quality was improved with ratio of steam to coal increased in process of coal parical gasification in atmosphere of air and steam. Gas quality was further increased in atmosphere of air/steam/oxygen. On basis of it, Experiment about semicoke combustion was conducted on the multifunctional test device.Research shows that semicoke of partial gasification can be stably burned and emission of pollutants was less.In order to verify feasibility of the technology of coal partial gasification and semicoke combustion, a 1MW pilot plant facility has been erected. A lot of experiments on coal partical gasification with air and semicoke combustion, recycle gas pyrolysis and semicoke combustion has been made on the 1MW pilot paint test facility. With air as gasification agent, system can produce low heating value gas,temperature is high and carbon conversion efficiendy increases with the bed temperature in the gasifier. With recycle gas as gasification agent, the system can produce high heating value gas, but carbon conversion efficiency is low and gas yield is low.On basis of summary on model about combustion and gasification in fluidized bed established by previous researchers, a mathmatic model on coal partial pyrolysis and gasification system was estebliashed according to result of experiment. The model include model for fluid dynamics in fluidized bed, model for coal pyrolysis and gasification, model for cyclone, model for partical attrition and elutriation, model for heat transfer in CFB, mass balance and energy balance about combustion furnace and gasifier. Simulation calculation for experiment condition on 1MW multi-generation pilot plant was proceeded. The result shows that experiment result and model calculation is coincidence primarily.