Numerical Simualtion Of The Effect Of Secondary Air Distribution On Combustion Characteristics In A Down Fired Boiler

In our country, generate electricity with low volatile coal occupy a very big proportion. W-flame boiler is the main type to fuel low volatile coal. But nowadays, the low volatile coal combustion in the W-flame boiler universally exists some problems, such as low combustion efficiency, excessive discharge of pollutants, furnace slagging, and so on. So, it's very important for our country's energy saving and emission reduction to carry out the technology of fuelling low volatile coal in W-flame boiler with High efficiency and low pollution. In this study, the influence of changing Secondary Air Distribution to the combustion characteristics of W-flame boiler was developed with numerical simulation methods, in order to provide reference information to it's optimal adjustment of combustion.A Integrated model of three-dimensional simulation of the combustion process was settled up to a310MW W-flame boiler ,the fluid flow, combustion and NOx generation process were simulated. The results of temperature distribution along the furnace height direction had a consistent trend with the results from image detection, the relative error is within 10%;at the same time ,the NO emission of furnace exit had a12.6% error with the experimental value. It indicated that the simulation method and model could reasonably simulate the fluid flow, combustion and NOx generation characteristics, which provided a basis for the further development of influence of Secondary Air Distribution on Combustion Characteristics in a Down Fired BoilerUsing the established three-dimensional numerical simulation model of combustion, carried out the numerical simulation of the influence of changing D/E Secondary Air's speed to the combustion characteristics, got the following conclusion. Keep D/E Secondary Airspeed a little high, then, it make the ParameterrM move to a high lever, as a consequence ,coal particles stay more time in boiler, and the c content in ash decreases .at the same time ,the central of fire moves to a lower parts of boiler, make the air distribution in boiler more powerful. at last ,the emission of NO decrease because of N reduction. Of course, the moving down of flame centre was good for the improvement of the heat transfer characteristics of the boiler and the safety and economics of boiler operation.Study suggests that, for the coal with better fire performance, under the conditions of ensuring the steady combustion in furnace, increasing the Secondary Air appropriately helps to increase the efficiency of coal combustion, reduce emissions of NO and improve he safety and economics of boiler operation.