Patent ID: 8075303

Claim:
Method for homogenizing the heat distribution as well as decreasing the amount of NO x in the combustion products when operating an industrial furnace ( 1 ) with at least one conventional burner ( 2 a , 2 b , 2 c , 2 d ) using air as oxidant, where a lance ( 3 a , 3 b , 3 c , 3 d ) is introduced into the furnace ( 1 ), the method comprising streaming an additional oxidant comprising at least 50% oxygen gas into the furnace ( 1 ) through the lance ( 3 a , 3 b , 3 c , 3 d ), and the total amount of oxygen supplied, partly through the air, partly through the additional oxidant, is supplied in a predetermined ratio in relation to the amount of fuel being supplied through the air burner ( 2 a , 2 b , 2 c , 2 d ), wherein at least 40% of the supplied oxygen is supplied through the additional oxidant, the lance ( 3 a , 3 b , 3 c , 3 d ) is caused to be arranged at a distance from the air burner ( 2 a , 2 b , 2 c , 2 d ) of at least 0.3 meters, the additional oxidant is caused to stream into the furnace ( 1 ) through the lance ( 3 a , 3 b , 3 c , 3 d ) with at least sonic velocity, and the additional oxidant is supplied only when the air burner ( 2 a , 2 b , 2 c , 2 d ) is operated at or above a certain lowest power.