烟气再循环对350kW燃气锅炉超低氮燃烧工况稳定性的影响

Influence of Flue Gas Recirculation on Combustion Stability of 350 kW Gas-fired Boiler under Ultra-low NOx Combustion Conditions

对采用外部烟气再循环技术的350 kW全预混表面燃烧燃气锅炉在不同负荷和烟气再循环率下的排放和燃烧稳定性进行了实验研究。结果表明,烟气再循环的引入可以有效降低锅炉NOx排放至30 mg/m 3以下。加设烟气再循环后,随着烟气再循环率的增加,炉膛内频率在20~30 Hz之间的压力振幅先增加后减小,与此同时2 Hz左右的压力振幅逐渐增大,燃烧不稳定程度加剧,直至喘振发生。喘振发生时,燃烧室强烈的压力振荡将沿着再循环管道传递回燃烧室,并对燃烧室压力场产生进一步影响,导致压力振荡在传递过程中被放大,最终导致火焰熄灭。

The emissions and combustion stability of 350 kW gas-fired boiler with full premix burner using external flue gas recirculation technology under different loads and flue gas recirculation rates are studied.Results show that the introduction of flue gas recirculation can effectively reduce boiler NOx emissions to below 30 mg/m 3.After the flue gas recirculation is added,as the recirculation rate increases,the amplitude of pressure oscillations at 20~30 Hz in the furnace increases first and then decreases,while the amplitude of pressure oscillations at about 2 Hz gradually increases,and combustion instability intensifies until surge occurs.When surge occurs,the intense pressure oscillations in the combustion chamber are transmitted back to the combustion chamber along the recirculation pipe and have a further effect on the pressure field of combustion chamber,causing the pressure oscillation to be amplified during the transmission,eventually leading to flame extinction.