基于FLIC软件的生物质层燃数值模拟

Numerical simulation of biomass grate furnace combustion based on FLIC

摘要:

为了优化链条炉燃烧，基于FLIC模拟平台对我国东北地区某7 MW生物质层燃热风炉进行数值模拟. 模拟结果表明，燃烧过程大致可分成3个阶段，依次是位于炉排上0~0.5 m的水分蒸发段、0.5~2.1 m的挥发分逸出燃烧段以及1.0~2.8 m固定碳燃烧阶段. 该燃料挥发分占比较高, 析出后床层厚度明显减薄，一次风温过低导致固定碳燃尽率低，所以可以适当提高一次风温. 根据燃料处于不同燃烧阶段，按需供风，如，在挥发分逸出燃烧阶段提供总风量的80%~90%，在固定碳燃烧阶段提供总风量的10%~20%，以此提高燃烧效率，并可以根据烟气温度对拱角以及炉拱覆盖长度进行结构优化，增强炉拱的引燃以及燃尽作用. 本文根据模拟所得结果提出对一次风以及其供风方式的优化策略，从而达到优化燃烧的目的.

Abstract:

Based on the FLIC simulation platform, we have performed a numerical simulation study on a 7 MW biomass layer fired hot air boiler in Northeast China. The simulation results show that the biomass layer can be roughly divided into three stages, the water evaporation section (0~0.5 m), the volatile emission combustion section (0.5~2.1 m) and the fixed carbon combustion section (1.0~2.8 m). The volatile content of this fuel is relatively high, the thickness of the bed after its precipitation is significantly reduced, and the primary air temperature is too low, resulting in a low fixed carbon burnout rate, so the primary air temperature can be appropriately increased. According to the characteristics of the fuel in different combustion stages, the air can be supplied on demand. For example, 80% to 90% of the total volume can be provided during the volatiles escape combustion stage, and 10% to 20% of the total air can be provided during the fixed carbon combustion stage. This improves the fuel combustion efficiency, and can optimize the structure of the arch angle and the furnace arch coverage length according to the flue gas temperature, and enhance the ignition and burnout of the furnace arch. According to the simulation results, it is proposed to optimize the primary air and the air supply scheme to make the combustion more adequate.