Characteristic research of a new type of secondary-air-box on a W-flame boiler with slit type burner

In order to solve the problem of air lack in the middle of the furnace which was caused by the wide width of the furnace and the large sectional dimension of the air-box in the original design of a W-flame boiler with slit type burner,a new separated type of secondary-air-box was modified from the original design of boiler No.4 in Huaneng Shang'an Power Plant.Characteristic test after the modification of the new type of secondary-air-box showed that the air speed deviation between the upper and lower arches and the air duct regions was smaller than conventional cold ventilation.When one side of the forced draft fans was run and the communicating door was closed,air speed at the stopped side was obviously lower than the side that forced draft fan was operated.The deviation of the air velocity near the nozzle could be effectively reduced through the adjustment of the secondary air doors on the upper and lower arches.In the case of opening the communicating door of single forced draft fan,the deviation of the mean air speed between the three duct regions was not far different from the operation of the double forced draft fans.On the contrary,the furnace outlet oxygen showed a trend of middle height and low both ends; and the oxygen distribution in the furnace outlet tended to be balance after adjusting the opening of the secondary-air-box door indicating the secondary-air-box door can effectively regulate the air distribution of the secondary air in the furnace and change the oxygen distribution in the outlet of the furnace.It has been showed that the appropriate adjustment of the secondary-air-box door opening can effectively reduce the SCR inlet NOxconcentration and ensure the economic and environmental operation of the boiler.