大比例半焦煤粉掺混燃烧排放数值模拟研究

Numerical study of the emission from co-combustion of large-proportion semi-coke and pulverized coal

半焦是原煤经过干馏后得到的产物,具有高热值、低挥发分的特点。现阶段作为煤化工副产品的半焦并未得到充分使用,研究半焦与煤粉的掺混燃烧有助于提高经济效益,而掺混燃烧的难点在于半焦的着火条件较差、燃尽率低、NOx排放质量浓度高。采用数值模拟方法研究了半焦与煤粉大比例掺混燃烧条件下,给粉方式、掺混比、二次风配风方式对炉膛内的温度场、NO质量分数场和CO质量分数场分布的影响。结果表明:均匀配风给粉条件下,半焦的最佳掺混比例为40%;燃料分层时半焦布置在上部燃烧器会导致炉内温度和NO质量分数激增,但可以通过改变二次风配风来改善。

Semi-coke is a product obtained from dry distillation of raw coal,and is of high calorific value and low volatile content.At present,semi-coke,as a by-product of coal chemical industry,has not been fully utilized.Studying the blending and co-combustion of semi-coke with pulverized coal will improve its economic benefit.However,the difficulties of the cocombustion lay on the poor ignition conditions,low burnout rate and high NOx emission.In the study on co-combustion of pulverized coal blended with large-proportion semi-coke,the effect of coal powder feeding method,blending ratio and secondary air distribution on the temperature field,NO mass fraction field and CO mass fraction field in a furnace was analyzed by numerical simulation.The results show that the optimal blending ratio of semi-coke is 40%;under the condition of even air and powder distribution.When the fuel is stratified,the semi-coke arranged on the upper part of the burner will make furnace temperature and NO mass fraction soar,which can be improved by optimize the secondary air distribution.