Numerical Study On Combustion Process Of 660MW Ultra-supercritical Oxy-coal Fired Boiler

China is the country with the largest coal production and consumption in the world. In China, almost three quarters of electric power generation rely on coal-fired units. Currently, two prominent problems for coal generating electric power are high coal consumption of unit electric power generation and seriously environmental pollution. Ultra-supercritical Oxy-coal fired unit can effectively weaken these two problems. However, there are few researches on this technology. In this paper, 660 MW Ultra-supercritical Oxy-coal fired boiler was conceptually designed and studied by numerical method.In order to keep the ultra-supercritical unit running with high parameters, Zhungeer coal was selected as design coal in this paper. We can acquire reasonable design parameters of the boiler based on the rational structure design and static simulation. By using the tangential firing, the burner positioned in four corners and four walls of the furnace was designed, respectively. Based on literatures, a series of suitable computing models were considered and analyzed, and the selected models were tested in order to ensure their accuracy.To ensure the performances of boiler and burner can meet the design requirements, the process of combustion in boiler was simulated by FLUENT and the operating conditions of ultra-supercritical oxy-coal fired boiler were studied. Based on numerical simulations, the distribution rules of velocity field, temperature field, component mole fraction, wall heat flux and particle trajectory were obtained. The results show that for the four-corner tangential combustion mode, the tangential diameter in the burner region varies with height, a vortex emerges at the top of the front wall and high temperature zone happens on both sides of primary air jet. Under the rich oxygen atmosphere, the peak value of nitrogen is only 0.25%. The distributions of wall heat flux are not uniform, the maximum value of wall heat flux appears in the burner region, and the distributions of particle trajectories are also related to the velocity field and the temperature field. When boiler is running under the four-wall tangential combustion mode, the diameter's change is smaller; the velocity and temperature field distribute more uniformly. The high temperature zone appears only on the back fire surface of primary air jet. In addition, under four-wall tangential combustion mode, the peak values of wall heat flux are decreased and more uniform wall heat flux appears, the coal particles are more flammable and the commixture of wind and pulverized coal is more abundant. Therefore, the four-wall tangential combustion mode is better than the four-corner tangential combustion mode.