高温水蒸气氛围中煤燃烧特性研究

A scheme of adding high temperature water vapor to the combustion system to achieve low-nitrogen combustion is proposed to reduce NO _x production during coal combustion, and its thermodynamic calculation and experimental research are carried out. Firstly, the possibility and limitation of the reactions in the volatile combustion process of coal after adding high temperature water vapor are examined by theoretical calculation based on the standard molar reaction Gibbs free energy change, the standard molar enthalpy and the equilibrium constant. Results of reaction path speculation show that in the high temperature water vapor atmosphere, the reactions of converting N element to N ₂ occur in the temperature range of coal combustion. Secondly, in reactions with various excess air coefficients, the equilibrium components after adding different concentrations of high temperature water vapor are calculated using the software HSC Chemistry. Results of the thermodynamic calculation show that the reaction of NO _x precursor to N ₂ happens in a wide temperature range: when the temperature ranges from 700 to 800 and excess air coefficient lies between 0.6 and 0.8, the formation of NO _x significantly reduces by adding high temperature water vapor; Reduction rate of NO _x increases with the concentration of high temperature water vapor increasing. Eventually, the combustion characteristics of pulverized coal in water vapor and air atmosphere are tested in a pulverized coal fixed bed combustion experiment system. It shows that the formation of NO _x is inhibited by adding high temperature water vapor and the effect is better that the result of the thermodynamic calculation, and the NO _x reduction rate has a nonlinear relation with the water vapor concentration and the temperature. This study may provide an economical and efficient reference solution to low NO _x combustion of coal.