有机固废热解气MILD燃烧的数值分析

Numerical Analysis of MILD Combustion of Organic Solid Waste Pyrolysis Gas

热解气的MILD燃烧是有机固废高效转换利用的关键技术之一。与传统单组分气体相比,固废热解气组分复杂、热值低、燃烧稳定性差。为提高固废热解气的高效清洁利用,采用数值模拟的方法,研究了不同燃料、空气过剩系数和空气入口截面积对固废热解气燃烧特性的影响,以及MILD燃烧形成条件。研究结果表明:相比单一组分甲烷,固废热解气由于高氢气含量使燃烧过程超前,且峰值温度高,温度场分布不均匀;改变燃烧室进口的配风条件对燃烧过程具有明显的影响,随着过剩空气系数的减小,燃烧室内的峰值温度有所下降,整体温度水平上升,温度分布变得更为均匀,但同时高温区的范围也明显增大,导致出口处NO排放量增加;在较低的过剩空气系数下,空气入口截面积的减小可以降低燃烧室内的峰值温度,温度分布均匀性得到有效提高,出口处NO含量会降低到0.003%以下,从而实现固废热解气的MILD燃烧。

MILD combustion of pyrolysis gas is one of the key technologies for efficient conversion and utilization of organic solid waste.Compared with traditional single-component gas,solid waste pyrolysis gas has the characteristics of complex components,low heat value and poor combustion stability.In order to improve the efficient and clean utilization of solid waste pyrolysis gas,the effects of different fuels,air excess coefficients and air inlet cross-sectional areas on the combustion characteristics of solid waste pyrolysis gas and its MILD combustion formation conditions were studied with numerical simulation methods.The research results show that,compared with the single components of methane,the combustion process of the solid waste pyrolysis gas is sped up because of its high hydrogen content.In addition,its peak temperature is high,and its temperature field is unevenly distributed.Changing the air distribution conditions at the inlet of the combustion chamber has a significant impact on the combustion process.With the reduction of excess air coefficient,the peak temperature in the combustion chamber decreases,the overall temperature level rises,and the temperature distribution becomes more uniform,but at the same time the range of the high temperature region also increases significantly,resulting in an increase in NO content at the outlet.Under the condition of low excess air coefficient,the reduction of the air inlet cross-sectional area can reduce the peak temperature in the combustion chamber,and the uniformity of temperature distribution can be effectively improved.In order to achieve MILD combustion of solid waste pyrolysis,the content of NO at the outlet should be reduced to no more than 0.003%.