Study Of Technical Theory High Efficiency Air Staging Combustion Controling NO_X Emissions

At present, we mainly used combustion technology for the control of nitrogen oxide emissions. Effective methods are low-NOX staged combustion furnace technology, low-NOX burner air staging and fuel classification techniques. The research of the air-staged efficient and the nitrogen characteristics are less, and the micro-study for the air-staged combustion is in initial stage. We mainly focused on removal of nitrogen oxides on the technology. So the depth study of coal air-staged combustion characteristics, the comparing of staged properties of different coals, the explaining of the mechanism of staged combustion from the micro level can help us to understand the efficient air staged, and have great significance for the reduction of nitrogen oxides.In this paper, the mechanism and the efficient of staged combustion of different types of coal are researched, which Shenhua as the representation of a high volatile, Linfen as a high ash content bituminous, Baorixile lignite as the representation of lignite coals. The experimental system is one-dimensional Multi-path Air Inlet Furnace with sampling along the furnace. Through the analysis of sampling, we research the impact of combustion process, coal composition, particle size, the excessive air ratio, air staged ratio, staged location of air injected and other factors on the release of NOX. The data along the furnace provide support for the analysis and the results and ensure the objectivity, so it plays a very important role for the improvement of the air staging combustion theory. The results showed that: the types of coals have a great influence on the efficient of staged combustion, lignite has a good effect for its easy lighting and strong burning, the effect of bituminous staging combustion is better then anthracite; coal contents impact the staged effect. Due to the high ash Linfen coal and the ignition time features, its effect of staging is weaken then Shenhua coal; staging level have different effects to coals. NOX of Light staging of Linfen is higher than unstaging. NOX of most coals reduces with level of staging, but the burn out rate reduces highly also; staging positions also have impact on air staging combustion, lignite have weaker effect than bituminous coal. Increase staging positions can reduce the nitrogen oxide emissions; in low oxygen oxidation-reduction zone, adding a small amount of air can enhanced the reduction, it has effect for lignite and high volatile bituminous coal, however, if there is no low oxygen oxidation-reduction zone, adding a small amount of air is meaningless.This paper presents the concept of apparent air staging. It is that the total air volume is divided by the ratio of the main combustion air and burned air. The greater the rate of the main combustion air, the greater the level of air staging. It did not consider the actual staged combustion effect of pulverized coal particles, even if the oxygen of the main combustion zone has reduced, but still the atmosphere is strong oxidation, nitrogen oxides generated strongly and the surface reduction reaction is very weak, the role of OFA is not much meaning, so the reduction of the final pollutant emission is not obvious or even counter-productive.