The Numerical Analysis On The Burnout Problem Of The Under-bed Start-up Burner In CFB Boiler

Energy and environment problems are getting more and more attention by the people all over the world. In the process of reform and development of China, it gets rapid economic development, national power is strengthened greatly. But this development relied on excessive consumption on energy, which caused serious energy and environment problems. Circulating fluidized bed boiler combustion technology is the best solution to reduce this problem, it is efficient energy-saving, low pollution and low emission, what’s more, it can use so many kinds of fuel, and it even can burn garbage. In nowadays, Chinese circulating fluidized bed CFB boiler technology is already quite mature, but the circulating fluidized bed boiler has some specific characteristics, there are still some hard problems, such as the start-up problem of circulating fluidized bed boiler which plagued many power plants is a thorny problem. In the light of burning problems of under-bed starting burner that caused in the circulating fluidized bed boiler, this article carried on deep research, and putted forward some constructive suggestions for practical problems.First, this article is to find the reason of the burnout problem of under-bed starting burner with analyzing the air distribution, nozzle parameters and pressure of wind chamber, and point out the error of actual operation in some electric power plant.Secondly, the under-bed start-up burner was abstracted and simplified, and the physical model to compute was established. Use numerical calculation software to simulate the combustion process of the under-bed starting burner in different conditions, the influences on the process of the under-bed starting burner combustion which is caused by the difference of the air distribution, nozzle parameters and pressure of wind chamber were analyzed.As to air distribution, the mixing and ignition wind were analyzed in this paper, a conclusion can be obtained as follows:1、the mixing air flow can be as large as possible when it meet the need for maintaining the minimum temperature of mixed flue gas, this setting can prevent the burnout problem;2、in order to make the burner achieve complete combustion as soon as possible, there must be a reasonable value for ignition air.As to nozzle parameter, the combustion processes were simulated in different fuel injection quantity, it was found that the temperature fields of different burner power were similar in reasonable air distribution conditions, but the higher burner power needs more air. The pressure of wind chamber was also simulated and analyzed. In the analysis of burnout problem, few people thought the burnout problem could be linked to the pressure of wind chamber, but according to the analysis in this paper, the effect of pressure of wind chamber to the combustion process of under-bed start-up burner is serious, it also can cause burnout accident.