New Combustion Technology for Low Nitric Oxides Emission Using Highly Preheated Air

It has been held that heat-recirculating combustion by regeneration produces high temperature flames and nitric oxides emission increases with the maximum temperature of a furnace. This is the main reason why reduction of nitric oxides is strongly required to enjoy high thermal efficiency of regenerative combustion systems. However, if we use preheated combustion air higher than the autoignition temperature of a fuel gas, combustion takes place even though combustion air is diluted with burned gases until the oxygen concentration becomes as low as 3 percent. We can utilize this unexpected condition to reduce nitric oxides emission because the temperature rise due to combustion under this condition is considered small. This implies the possibility of innovative combustion technology in which both high thermal efficiency and low nitric oxides emission can be achieved simultaneously.