超临界650 MW机组对冲燃烧锅炉结焦防控研究

Study on coking prevention of supercritical 650 MW opposed firing boiler

针对某超临界650 MW机组对冲燃烧锅炉结渣问题,通过热力计算校核不同煤种对其炉膛出口烟温及锅炉热负荷影响,采用计算流体力学(CFD)模拟计算分析炉内配风及燃烧器扩锥角对炉膛烟气动力场与烟温的影响。研究结果表明:锅炉设计参数及煤种不是该炉结渣的主要影响因素;变风量模拟结果表明调整内、外二次风比例可明显改变炉膛烟气动力场,但在实际调整过程中变风量对于抑制锅炉结渣效果不显著;变扩锥角模拟表明将燃烧器扩锥角由45°改为30°可降低水冷壁区域热负荷,可抑制燃烧器周围区域结渣;在现场实验中,将燃烧器扩锥角由45°改为30°并调整配风后,锅炉结渣情况得到大幅改善;适量降低SOFA风比例可以降低炉膛火焰中心高度及炉膛出口烟温;二次风旋向对炉内流场特性影响明显,在后续调整中可考虑针对SOFA风比例和二次风旋向作进一步调整。

In order to effectively prevent the slagging of a supercritical 650 MW opposed firing boiler,the influence of different coal types on the flue gas temperature at the furnace outlet and the heat load of the boiler was checked by thermodynamic checking calculation,and the influence of the air distribution in the furnace and the coneexpanding angle of the burner on the flue gas dynamic field and flue temperature of the furnace was analyzed by CFD simulation.The results of the thermodynamic checking calculation showed that the boiler and the coal type were not the main reason for slagging.The variable air volume simulation showed that adjusting the ratio of internal and external secondary air could have effect on the dynamic field of flue gas.But in operation,changing the air volume did not solve the slagging problem well.The simulation results pointed out that the heat load of the water wall area could be reduced by reducing the cone-expanding angle of the burner from 45°to 30°,so as to inhibit the slagging.In the actual adjustment,after changing the cone expansion angle of the burner from 45°to 30°and adjusting the air distribution,the slagging situation of the boiler was greatly improved.The calculation results of variable SOFA wind showed that the appropriate reduction of SOFA wind proportion could reduce the flame height and the flue gas outlet temperature.The simulation of variable secondary air rotation showed that the secondary air rotation had a significant influence on the flow field and the slagging risk would significantly increase if the rotation of the burner was not arranged according to designed value.Further adjustments to SOFA wind ratio and secondary wind swirl could be considered in following adjustments.