Research About The Cold Air Dynamic Filed For A 660MW Down-Fired Boiler

With the rapid development of the national economy of China, Energy consumption has become increasingly high. For China's coal-dominated energy structure,More than half of coal is used in power station boiler. In china's power coal reserve,The capacity of low quality coal such as anthracite and lean coal which are used for power generation will increase. Therefore, the development of low quality coal combustion technology becomes imminent. W-shaped flame boiler, which adopts methods such as long-flame, air staging and sectionalized combustion of pulverized coal, is applicable for burning anthracite, lean coal and other low quality coal in large power station boilers. At present, more than 50 W-type flame boilers have been put in service in China, but some problems still exist.Aiming at the problems that there are high carbon-in-ash and NO_X emission in the down fire boiler from some Power plant, in this paper, the bench was built on the basis of #2 boiler from the Power plant which has the capacity of 660MW.The Geometry ratio of 1:15 was adopted. The test includes mainly two parts. First, tracer experiments were done in different angels of F-layer guiding devices. The other part was air dynamic field measurement test using the 30 degree F-layer guiding device in the cold boiler.The result shows that the flow field is improved obviously through the F-layer guiding device. With the increase of the angle, the guiding effect becomes obvious and the primary air jet is prolonged. Under the degree of 30 for the F-layer guiding device, under-way jet travel can meet the requirements. In every angle for F-layer guiding device, the guiding effect becomes less evident with the increase of over fire air (OFA) air ratio, and the primary air jet gets shorter. When the primary air reaches 20 percent and 25 percent, it can meet the demand. Modified exhaust gas can mix with the primary air very well, which is favorable for preventing the primary air from washing the wall. Reducing jet area is beneficial for organizing the whole flow.By analyzing the result of tracer experiment, 30 degree F-layer guiding device can improve the whole field, meet the need of the primary air jet, and the system resistance is relatively small. The further results show that the flow distribution is in accordance with the experimental data. Under the 30 degree F-layer diversion device, with the increasing air ratios of OFA, the mixed airflow declination angle gets smaller from the F-layer second air outlet. However, at the air ratio of 20 percent or 25 percent, it can keep a wide dip. The increasing air ratio is adverse to the primary air undershoot. While the air ratio gets 20 percent or the velocity is increased, it helps the primary air jet. Changing F-layer air has less influence on the flow. The smaller jet area can enhance the air speed and make up the shortage of retrofitting OFA. However, when the area gets reduced too much, it causes the jet location down and affects the primary air jet.