Using The Classification Of Air Reduce Boiler No_x Emission And Optimization Of The Water Wall Near The Wall Atmosphere Experimental Study

The NOx is among the most serious pollutants from the coal-fired boilers, resulting in domestic pollution and acid rain. With more stringent NOx emission regulation, there is an imperative necessity for China to develop a suitable de-NOx technology.The air-staging technique can reduce the NOx emission effectively. With air staging, normally 75-85% of the air is supplied to the primary combustion zone along with all of the required fuel. This creates a "fuel-rich" flame zone where the formation of NOx is retarded due to sub-stoichiometric combustion conditions. The sub-stoichiometric conditions limit NOx formation by reducing the combustion temperature and limiting the amount of oxygen available for NOX production. The remainder of the air is injected outside the primary combustion zone to complete the combustion of the fuel.The air-staging technique has been carried into execution in an utility coal-fired boilers where the secondary air has been feed to the furnace at the downstream of coal-powder flow, formed staged-air combustion in both vertical and horizontal direction, reduced the NOx formation by 35%.The high-temperature corrosion of the water wall tubes has also been studied in this thesis. In China, high-temperature corrosion has been found in most of the coal-fired boiler of power plant, and resulted in enormous loss.It is found that the high-temperature corrosion was mostly due to the exist of H₂S in the gas, and which mainly comes from the iro'n-pyrites-sulfur in the coal.With the air-staging technique adopted, the area where high-temperature corrosion aroused was covered by the fresh air and the sub-stoichiometry was optimized.