Reaction zone characteristics, thermal performance and NOx/N2O emissions analyses of ammonia MILD combustion

Abstract

Pure ammonia MILD combustion is studied numerically in a furnace. The effects of furnace wall temperature and dilution of inlet air with nitrogen on the characteristics of reaction zone (RZ), temperature distribution and exhaust emissions are investigated. The results show that lowering the furnace wall temperature and adding diluent to the inlet air, result in expansion of the RZ, reduction of fuel and oxidizer consumption rates, lower Damkohler, increased turbulent Reynolds and more similar RZ properties to the distributed combustion regime in the combustion regimes diagram. At a lower concentration of oxygen in the oxidizer, a higher threshold wall temperature is required for stable MILD combustion. Reducing the wall temperature and oxygen mole fraction in the oxidizer, increases the uniformity of temperature distribution. Analysis of exhaust emissions shows that reducing wall temperature and oxygen level in the oxidizer stream can significantly reduce NOx pollution, however, N2O emission rises.