Patent ID: 8920160

Claim:
A low NO x emission industrial burner including: a hollow metal body defining a longitudinal axis, a refractory diffuser, arranged at an open end of the hollow body so as to define a volume within said body, the refractory diffuser having a cavity defining a first combustion area, a second combustion area downstream of the first combustion area and in communication therewith, a first injection lance for injection of a fuel gas, centrally arranged within said hollow body, in communication at one end with said first combustion area, at least one second injection lance for injection of the fuel gas, laterally arranged within said hollow body, directly in communication at one end with said second combustion area, switching means adapted to switch the injection of the fuel gas from the first injection lance to said at least one second injection lance or vice versa, a conduit for feeding comburent air into said volume, first longitudinal holes for the injection of a first portion of the comburent air, provided in the refractory diffuser and arranged along a first cylindrical side surface, each first longitudinal hole having an outlet section directly in communication with the first combustion area, second longitudinal holes for the injection of a second portion of the comburent air, provided in the refractory diffuser and arranged along a second cylindrical side surface, which is coaxial and external to the first cylindrical side surface, each second longitudinal hole having an outlet section directly in communication with the second combustion area, wherein said at least one second injection lance for the injection of the fuel gas is at least partially housed within a respective second longitudinal hole for the injection of a second portion of the comburent air, said burner being adapted to perform a multistage flame combustion during heating of a combustion chamber until an autoignition temperature of the fuel gas is reached and, indifferently, a multistage flame combustion or a flameless combustion at temperatures higher than said autoignition temperature, thus ensuring low NO x emissions at any operating conditions.