| Global warming caused by greenhouse effect has become increasingly prominent. The major factor of greenhouse effect is massive CO2 emission followed by fossil fuel combustion and power plant emission accounts for one third emission of the total world CO2. CCS (CO2 Capture and Storage) is the most effective way to reduce CO2 emission. Among CCS technologies, O2/CO2 combustion technology is considered to be a new generation of clean coal power generation technology, with obvious advantages and good prospect, which is easy to trap high concentration CO2 directly without separation and control pollutant emission comprehensively. Therefore, the importance of study on combustion characteristics and performance of pulverized coal in O2/CO2 atmosphere is significant.Non-isothermal experiments of three types of pulverized coal (PC) were conducted in thermo-gravimetric analyzer including PC pyrolysis in N2 and CO2 atmospheres, PC combustion in different proportions of O2/N2 and O2/CO2 atmospheres. Combustion characteristic parameters, combustion characteristic indexes and kinetic parameters for PC were calculated and analyzed. Research shows that, at the same O2 concentration when N2 is replaced by CO2, both PC ignition and burnout temperatures are lagged, the performance of volatile releasing characteristics, flammability and burnout deteriorates, reaction intensity declines and reaction mechanism changes, with the increase of O2 concentration, PC combustion performance is improved. The results also show the similarity of PC combustion characteristics between 30%O2/70%CO2 and air atmosphere is different from the results from tube furnace tests or numerical simulations due to the different oxygen concentration around pulverized coal particles.After analyzing the experimental data, the characteristics of coal combustion in O2/CO2 atmosphere were learned. PC combustion process of a 600MW tangential boiler was numerically simulated with the Computational Fluid Dynamics software FLUENT, based on the analysis, the rationality of the physical, mathematic model and the method of meshing were verified. The conditions in different proportion of O2/CO2 and different air distribution mode were numerical simulated, flow field, temperature profile, components concentrations, wall heat flux, heat absorption and so on were analyzed. Research shows that:comparing to air condition, the combustion of 21%02/79%C02 atmosphere is lagged, the boiler temperature and radiation levels reduces, burnout rate declines, with the increase of O2 concentration, PC combustion performance is improved; the combustion of 29%02/71%CO2 atmosphere is most closest to air atmosphere, but the emission of NO significantly reduces; after reducing the amount of OFA, the average wall heat flux increases, boiler flue gas rotation intensity increases; after increasing the height of primary air tuyere, the unburned carbon in slag reduces, burnout degree increases; among the type of secondary air distribution (Equal, Normal pagoda, Waist drum, Dumbbell, Double waist), the Double waist type's combustion performance is the best, whose flame is closed to the furnace center, the phenomenon of flame attachment reduces, furnace wall heat flux, total heat absorption and burnout degree are high; comparing to dry flue gas recycle, the phenomenon of flame attachment of wet flue gas recycle reduces, rotation intensity increases, the amount of storage heat increases, the overall heat transfer conditions is improved, then taking into account the cost of evaporation of flue gas, should adopt the wet recycle.The research results gained in this paper could provide significant reference to research on the combustion characteristics of pulverized coal and O2/CO2 combustion alteration or design of boiler.
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