燃煤链条炉掺烧半焦NO_(x)生成特性及配风优化数值模拟研究

Numerical Simulation Study on NO_(x) Emission Characteristics and the Optimization of Air Induction of Coal-Fired Chain Boiler Blended with Semi-Coke

针对煤炭分级分质转换过程中产生的过剩副产品热解半焦,为更加高效清洁的利用煤炭资源,本文提出在链条炉中掺烧热解半焦。使用Fluent软件对链条炉中烟煤与半焦的掺烧工况进行了数值模拟,研究了炉膛内流场、温度场和组分场的变化规律以及配风优化的影响,探讨了掺烧过程中NO_(x)的生成特性以及配风优化对炉内燃烧性能的影响。结果表明,提高半焦的掺混比例,炉膛中NO的体积分数升高,炉膛出口平均烟温降低。推迟配风有助于炉内形成贫氧程度更深的局部还原性区域,从而抑制NO_(x)原始生成,减少炉膛NO_(x)最终排放。层燃室燃复合燃烧时,烟煤在炉排上燃烧的同时将半焦粉末喷入炉膛,半焦比例每增加5%,炉膛出口平均温度约增加30℃;半焦粉末在炉中喉口位置喷入时,炉膛出口烟温最高。本文的研究结果能够为链条炉高效低污染掺烧利用热解半焦等低挥发分煤基固体燃料,提供一定的理论依据和科学指导。

To utilize coal resources more efficiently and cleanly,this paper proposes the blending of pyrolysis semi-coke in the chain boiler for the excessive by-products,pyrolysis semicokes,produced in the process of coal classification in quality.Numerical simulations of the blending conditions of bituminous coal and semi-coke in a chain boiler were carried out by using Fluent software.The paper investigates the changing patterns of flow field,temperature field and component field in the boiler and the effect of air distribution optimization,explores the NO_(x) emission characteristics and the effect of air distribution optimization on the combustion performance of the boiler during the blending process.The results show that the concentration of NO in the boiler increases and the average gas temperature at the boiler outlet decreases by increasing the blending ratio of semi-coke.Delaying the air distribution helps to form a local reductive zone with deeper oxygen-deficient in the boiler,thus suppressing the original NO_(x) generation and finally reducing the NO_(x) emission of the boiler.When compound combustion of rate firing-chamber rating is organized,the bituminous coal is burned on the grate while the semi-coke powder is sprayed into the boiler.For each 5%increase in the semi-coke proportion,the average temperature at the boiler outlet increases by about 30℃;the highest gas temperature of the furnace outlet is when the semi-coke powder is sprayed in the throat of the boiler.The results of this paper can provide some theoretical basis and scientific guidance for the efficient and low-pollution blending of low volatile coal-based solid fuels such as pyrolysis semi-coke in chain boilers.