Study on Low Nitrogen Combustion Characteristics of Metal Fiber Burner in Limited Space

Metal fiber surface combustion technology has become one of the most promising low nitrogen combustion technologies for gas boilers because of its advantages of stable combustion process and uniform temperature distribution. Based on the low-nitrogen combustion experimental data of metal fiber surface in limited space, this study established a three-dimensional physical model of metal fiber surface combustion and carried out the full-premixed combustion numerical solution based on the porous medium resistance model, metal fiber turbulence model and EDC combustion model. It obtained the flame combustion conditions and the velocity characteristics of hot smoke flow field of metal fiber surface combustion in limited space, as well as the temperature field distribution and fuel distribution in furnace. Considering the influence of different excess air coefficient, it studied the emission characte-ristics and average generation rate distribution of prompt NO_x and thermal NO_x on metal fiber surface. The results show that under different excess air coefficients, the generation rate of prompt NO_x is faster than that of thermal NO_x. However, limited by the effective reaction space and reaction duration, the volume occupied by prompt NO_x in the furnace is much smaller than that of thermal NO_x. With the increase of excess air coefficient, the generation rate and emission of thermal NO_x gradually decrease. When α=1.6, the emission of NO_x from flue gas outlet is 22.55 mg/m³, which meets the standard of low nitrogen combustion. Therefore, in addition to changing the flame temperature, oxygen concentration and combustion mode, the generation of thermal NO_x can be suppressed by controlling the excessive air coefficient, and ultralow nitrogen combustion of industrial gas boilers can also be effectively achieved.