Modeling of combustion characteristics and NOx emission in highly preheated and diluted air combustion

The gas diffusion combustion in a regenerative furnace with highly preheate d and diluted air has been numerically investigated in this paper. The high ly preheated air combustion possesses high combustion intensity and high le vel temperature, but the NOx emission also has an unwanted high level. Decr easing the oxygen concentration in the highly preheated air could decrease the NOx emission and improve the uniformity of temperature distribution in the furnace. The combustion characteristics of highly preheated and diluted air combustion have been studied, including temperature distribution, soot formation, OH radical distribution, as well, as NOx emission. The influenc e of the preheated air temperature, the oxygen concentration, and the air d iluent has also been investigated. The optimal combinations of the preheate d air temperature and the oxygen concentration have been predicted in the c ase of flue gas recirculation, which could provide the highest possible tem perature in the furnace while keeping the NOx emission lower than the permi tted value. (C) 1998 by John Wiley & Sons, Ltd.