Research On Closing-To-Wall Air Technologies Of 600MW Opposite Firing Boiler

With more and more coal fired power plant boilers reforming low-NO_x combustion technology,the problem of high temperature corrosion of water wall is becoming increasingly prominent,especially the side wall of opposed firing boiler.Therefore,how to ensure low NOx combustion without high temperature corrosion has become an urgent problem to be solved.In this paper,the Dongfang 600 MW subcritical unit opposite firing boiler is taken as the research object.the effects of different closing-to-wall air structures and operating parameters on the flow and combustion characteristics in the furnace are studied by means of gas-particle two-phase flow characteristics experiments and numerical simulation,which provides guidance for solving the high temperature corrosion problem of boilers by closing-to-wall air technology.Firstly,according to the present situation of water wall high temperature corrosion of boiler on site and the development of water wall high temperature corrosion control technology at home and abroad,three technical schemes for water wall high temperature corrosion control are put forward.Then a gas-particle two-phase modeling test-bed with a scale of 1:9 was built in the laboratory,and the parameters of closing-to-wall air were optimized by using a three-dimensional PDA measurement system.The gas-particle two-phase flow characteristics in the furnace under the conditions of closing-to-wall air nozzle type,air rate,nozzle location and air volume ratio were studied respectively.The results show that the bigger the air rate,the stronger the penetration ability of the air flow and the average axial velocity,and the smaller the average radial and tangential velocity.The closer the closing-to-wall air nozzle is to the center line of the burner,the stronger the disturbance of the closing-to-wall air by the air flow of the burner,the weaker the penetration ability,and the smaller the average gas-particle velocity.Finally,the numerical simulation of the whole furnace is used to simulate the effect of the optimum scheme on the field boiler,which is as follows:the front and rear wall nozzles are adopted,the rate of closing-to-wall air is 3%,and the distance between closing-to-wall air nozzles and side walls is 80 mm.and the differences of temperature field,flow field and concentration field in the furnace before and after the closing-to-wall air technology transformation are compared.The results show that the optimum scheme of closing-to-wall air can significantly increase the concentration of O₂ and reduce the concentration of CO in the middle of the side walls without affecting the flow field and temperature field of the main combustion zone in the furnace,so as to achieve the goal of high temperature corrosion control.