Research Of NO_x Production Mechanisms At Oxy-fuel Combustion

The main greenhouse gas——CO₂ influence reversely on environment, and the use of coal combustion is increasing to the CO₂ production. There are many researchers who are researching the CO₂ reduction in coal combustion. The O₂/CO₂ combustion technology is one of the most important achievements for CO₂ recovery. As a novel low emission combustion technology, O₂/CO₂ combustion technology can not only reclaim the CO₂, but also is useful in controlling the emission of NO_x.This thesis does research on combustion characteristics by simulating the chemical kinetics of CH4 combustion in O₂/CO₂ and O₂/N2 atmosphere. The following developments were obtained basing on our kinetic study: A majority of productions are similar in both O₂/CO₂ and O₂/N2; concentration of CO is much higher at O₂/CO₂ combustion; Mixture of O₂/CO₂ has high thermal capacity and low diffusibility, which bring many disadvantages in combustion: With 40% initial O₂ concentration, the adiabatic flame temperature in O₂/CO₂ is 292°C lower than that in O₂/N2 and flame speed is only one third of that in O₂/N2. The difference of temperature between two atmospheres becomes 443°C at 20% O₂ concentration.In addition, based on the system of Drop Tube Furnace (DTF), a series of experiments on emissions of NO_x in O₂/CO₂ atmosphere are carried out. According to the datum, we can reach the conclusion that: The yield of NO_x in O₂/CO₂ is lower than that in O₂/N2 atmosphere, but the difference is not very big; Temperature has the similar effect on emissions of NO_x in both two atmospheres; the effect of coal composition on fuel-NO_x determines the rule of NO_x production. The coal with higher N content and lower FC/V value will emits more NO_x.The disciplines summarized from the calculation and experiments are significative for the theory and technology. It provides reliable reference for optimizing the emission characteristic in O₂/CO₂ combustion technology.