OCR Text |
Show 2 because the flame temperature is increased. However, when fuel or air is diluted by the inert gas (N2) or exhaust gas, the amount of NOx is reduced drastically and flame is stable even below the lean limit of inflamability because the temperature maintain at high level, even though oxygen concentration decrease. Thus, the low N 0 X combustion can be achieved. The preheat is usually gotten by recuperation from the furnace exhaust gases to save energy by the heat transfer of a latent heat in the furnace. For active N 0 X control, mechanical fluegas recycle through the burner, also is referred to as external fluegas recirculation, can be employed. The air and fuel are introduced into the combustion zone in which exhaust gases that have lost thermal enthalpy by heat transfer to the burner tile. Therefore, by introducing regenerator, reaction temperatures and reactant concentration levels are lowered. However, such forced recirculation is costly. Removal of NOx by treatment is also expensive. Other approaches to N 0 X abatement include air staging, fuel staging, and so-called as reburning, but none of these alone have proven capable of meeting the more stringent legislated limits on N 0 X when substantial air reheat is employed without resort to more costly and cumbersome control technologies such as external fluegas recirculation. It is evident that product recirculation has been considered to be the single most effective means of suppressing N 0 X formation. If this can be obtained through burner design alone, possibly also incorporating aspects of staging and reburning, then technologies that are both very effective in NOx control and economically attractive should result. These effects are obtained by the highly preheated air [1-5]. Soviesial et al. constructed a new burner, in which complex mixing processes coupled with non-adiabatic reaction at unusually low temperature and concentrations occur [1]. It is noteworthy that the development of regenerative burner constitutes a reversal of a long trend in burner design and furnace operation, a reversion to a mode of operation whose virtues for N 0 X reduction were earlier unrecognized, nor would they have been deemed important, but whose penalties, primarily for combustion stability, The |