Abstract:

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, a three-dimensional physical model of metal fiber surface combustion was established, and the full-premixed combustion numerical solution was carried out based on the porous medium resistance model, metal fiber turbulence model and EDC combustion model. The flame combustion conditions and the velocity characteristics of hot smoke flow field of metal fiber surface combustion in limited space were obtained. Temperature field distribution and fuel distribution in furnace. Considering the influence of different excess air coefficient, the emission characteristics and average generation rate distribution of fast burning NOx and thermal NOx on metal fiber surface were obtained. The results show that under different excess air coefficients, the generation rate of fast NOx is faster than that of thermal NOx. However, limited by the effective reaction space and reaction duration, the volume occupied by fast NOx in the furnace is much smaller than that of thermal NOx.With the increase of excess air coefficient, the generation rate and emission of thermal NOx gradually decrease. When α=1.6, the emission of NOx 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 thermodynamic NOx can be suppressed by controlling the excessive air coefficient, and ultra-low nitrogen combustion of industrial gas boilers can also be effectively achieved.

Key words: low nitrogen combustion, metal fiber burner; surface combustion, numerical simulation