Numerical Simulation Of Secondary Wind Distribution Characteristics In Coal-fired Boilers

Energy necessary for survival and development of mankind,and it is also the focus of political,economic,and diplomacy in the world today.With the continuous development and increasing strength of our country,the demand for energy is also increasing.At present,thermal power is still the main energy source of our country.The main fuel for thermal power is coal,it is a non-renewable energy source.Excessive use of coal will cause resource depletion.In addition,the burning of coal will make a lot of harmful substances produced and pollute the city.air.Therefore,the improvement of the efficiency of coal-fired boilers is an urgent problem in China today.In coal-fired boilers,the secondary air is the main source of oxygen required for fuel combustion,therefore,the quality of the secondary air has a critical impact on the operation of the boiler.However,in hedge-fired boiler,there are several burners in each bellow,because the air inlets of the secondary air are on both sides,and the secondary air bellow is too long,it will make differences of air flow in the same air bellow,that is,the uneven distribution of the secondary air flow,which will cause the secondary air skew from sides to the middle,resulting in insufficient secondary air near the side wall,and make the inadequate combustion of fuel,a reducing atmosphere will be formed near the side wall,leading to corrosion of the oxidation protective film on the surface of the water wall of the side wall,and then the water wall will be corroded.It is likely to cause safety accidents.Therefore,the avoidance of uneven distribution of the secondary air has been became an important subject of boiler combustion research.Numerical simulation technology has been becoming an effective method for predicting the flow field in the furnace with the continuous development of science and technology and the improvement in technology.The use of numerical simulation technology can eliminate the tediousness and cost of experiments,and also has a higher accuracy rate.In this paper,the secondary air duct of a 600MW hedge-fired boiler in a domestic power plant is used as a model to simulate the velocity and flow field of the bellows,summarize the distribution of secondary air,and analyze the distribution of secondary air flow according to the simulation results.Then the problem of secondary air flow distribution will be analyzed based on the simulation results.After that,the flow distribution of the secondary air was adjusted by adjusting the opening of the air door of each burner,and finally verified by numerical simulation,and the following conclusions were drawn:1.In the secondary air duct,due to the different gas velocity on the windward side and the leeward side of the burner,the uneven distribution of secondary air flow and the deflection of secondary air are caused.And the larger the difference between the gas velocity on the windward side and the leeward side,the larger the difference between the secondary air flow and the average secondary air flow.2.The flow of secondary air entering the combustor can be controlled by adjusting the opening of the air door of each combustor,and then the secondary air can be evenly distributed to each combustor.This method can effectively reduce the deviation of the secondary air flow of the combustor.In addition,the combustion quality of the boiler can be improved and the high temperature corrosion of the side wall will be reduced.