| Down-fired boiler is a kind of combustion equipment used to burn inferior coal with low volatile content and difficult ignition temperature.Due to its long combustion stroke,the pulverized coal is easy to burn out.It is widely used in China.However,because the coal used in W flame boilers is generally low in volatile matter and difficult to catch fire,the combustion temperature in the furnace is higher and the NOx emission at the furnace outlet is also higher.The combustion arrangement of the W flame boiler plays a decisive role in the flow and combustion characteristics of the furnace,which directly affects the pollutant emission of the boiler.Therefore,it is of great significance to study the combustion arrangement of the W flame boiler.This paper was based on a 350 MW anthracite-fired W-type flame boiler,a 1:20boiler mold scale model test bench was built,and glass microbeads were used to replace the coal powder particles.The gas-solid two-phase flow law of the particle flow carried by the gas flow inside the furnace is measured.Obtain the experimental data of the gas-solid two-phase flow PDA in the furnace under the original working conditions,and obtain the particle volume flow rate and the change rule of the vertical velocity.The gas-solid two-phase flow under different working conditions was numerically simulated and compared with the results obtained from the PDA experiment to verify the accuracy of the flow model.A numerical simulation of the combustion process in a 350 MW W flame boiler burning anthracite was carried out.The accuracy of the numerical simulation method is determined by comparing and verifying the temperature of the measuring point in the furnace with industrial test data.Extract the distribution of furnace section speed,temperature,oxygen concentration,NOx concentration,and the ignition temperature curve of pulverized coal particles,and analyze the effects of different internal and external secondary air baffle openings and the angle of the tertiary air nozzle on the flow and combustion process And analyze the carbon content of combustibles in fly ash at the furnace outlet and the NOx content at the furnace outlet to determine the best opening degree of the secondary air baffle inside and outside and the inclination angle of the tertiary air nozzle.In order to optimize Fluent’s original NOx model and improve the accuracy of numerical simulation calculations,user-defined programming UDF was carried out through the data obtained from the reaction mechanism experiment of coal-burning coal,and the Ux program simulated calculation of the NOx distribution and site The NOx distribution in the furnace measured by industrial experiments and the original Flux NOx model were compared to verify the feasibility of the UDF program.In order to realize the efficient use of blue charcoal,a low-volatile low-quality fuel,based on a 350 MW anthracite W-type flame boiler,a numerical simulation study on anthracite and blue charcoal co-firing was conducted.According to the different calorific value ratio of anthracite and blue charcoal and different coal blending methods of coal mill,a comparative analysis was carried out,and the influence law of calorific value ratio and coal blending method on furnace combustion was obtained. |
