生物质链条炉床层燃烧建模及一次风影响分析

Modeling of bed combustion in grate-fired biomass boilers and analysis of the effects of primary air

中文关键词: 生物质  床层燃烧  数值模拟  一次风

英文关键词: biomass  bed combustion  numerical simulation  primary air

中文摘要:

      基于多孔介质非热平衡的方法,考虑了床层高度的变化及颗粒内部温度梯度的影响,建立了一维非稳态燃烧模型来模拟炉排上移动床层的生物质燃烧。模拟计算结果与实验值对比分析表明,总体上数值计算结果与实验数据吻合较好。通过对不同一次风参数下床层燃烧的模拟结果分析得到,随着一次风风量的增加,床层剩余质量先减小后增大；在燃烧前期,床层出口气体温度上升速度减慢,挥发分析出速率降低,焦炭燃烧速率增大；在燃烧中期,床层出口气体温度先上升后下降,焦炭燃烧速率下降。一次风风温相比于一次风风量对床层燃烧影响较小,增大一次风风温可以提高挥发分析出速率,降低床层出口气体温度和床层剩余质量。

英文摘要:

      Based on the thermal non-equilibrium porous medium method, a one-dimensional unsteady combustion model considering the change of bed height and the influence of temperature gradient in particles has been developed to simulate the biomass combustion in moving bed on the grate. The predictions of the numerical model are compared with experimental results and show good agreement. The effects of primary air on bed combustion are numerically investigated and the results indicate that the residual mass decreases and then increases with the increase of primary air flow rate; rising velocity of the gas temperature above the bed and volatile release rate decrease, but char burning rate increases with the increase of primary air flow rate in the earlier stage of combustion; in the middle stage, the gas temperature above the bed increases and then decreases with the increase of primary air flow rate, and char burning rate decreases. The temperature of primary air has less influence than flow rate on bed combustion, volatile release rate increases, but gas temperature above the bed and residual mass decrease with increasing primary air temperature.