Study On The NOx Formation And Influence Law During The Stage Of Pulverized Coal Ignition

As the biggest producer and consumer of coal in the world , the coal hold a dominant position in the energy need and consumption of our country . However , during the process of the pulverized coal burning, it will emit a lot of NO_x which will pollute the enviroment greatly and be much harmful to people's health. But , for the coal fired boiler, the emission and control of NO_x are still complex,so more comprehensive studies are needed for the development of the pointed low NO_x emisstion technology.This paper has first discussed the formation mechanism and influence factors of NO_x and resited some effective control measures in the boiler of power plant , and introduced the test equipment - ignition furnace in details. Next ,the characteristics of NO_x emission along the ignition furnace are investigated for three typical pulverized coals under different excess air factors and main air rates during ignition stage. Combustion product are collected and analyzed to calculate the Conversion rate and decide the optimal value of excess air factor and main air rate. Besides, other factors are also analyzed particularly, such as the coal sort and using the inner main air alone. The results show that NO_x are mainly produced in the primary ignition zone, excess air factor and main air rate have a great influence on the release of NO_x. With the decrease of the two factors, NO_x emission as well as the NO_x conversion rate decreases gradually. However the lower is not the better, there exists an optimal value. There isn't much change of the characteristic of NO_x emission by using the inner main air alone. Besides, NO_x emissions are closely related to the coal sort. Generally speaking, during ignition stage, the higher volatile the coal contains, the more NO_x it emits, and the forwarder the peak value of NO_x release moves. Nitrogen content has a small influence in the NO_x formation during ignition stage.