Burner

Abstract

A burner capable of producing a low NO x emission combustion in the whole operating range, maintaining the flame at all times anchored to the diffuser body of the burner and without the use of systems, for example valves, with which to switch the introduction position of the reactants according to the temperature of the furnace. Such a burner is more flexible and cost-effective, both from a system point of view and from a control point of view, with respect to traditional burners.

1 . A burner comprising:
 a comburent gas inlet opening,   a combustible gas inlet opening,   a first external tubular body provided at a respective first end with one or more respective ports for the outlet of part of comburent gas, and connected to the comburent gas inlet opening;   a second tubular body arranged within the first tubular body and communicating with the latter, provided at a respective first end with one or more respective ports for the outlet of another part of comburent gas,   a third tubular body arranged within the second tubular body, provided at a respective first end with one or more respective ports for the outlet of part of combustible gas, and connected to the combustible gas inlet opening;   a fourth tubular body arranged within the third tubular body and communicating with the latter, provided at a respective first end with one or more respective ports for the outlet of another part of combustible gas,   wherein the respective first ends of the first, second, third, fourth tubular bodies are arranged in proximity of a same first end of the burner so that two combustion zones of comburent gas with combustible gas are defined at the same first end of the burner.   
   
   
       2 . A burner according to  claim 1 , wherein the one or more respective ports of the second tubular body are arranged in more internal position with respect to the one or more respective ports of the first tubular body. 
   
   
       3 . A burner according to  claim 2 , wherein the one or more respective ports of the third tubular body are arranged in more internal position with respect to the one or more respective ports of the fourth tubular body. 
   
   
       4 . A burner according to  claim 3 , wherein the second tubular body is provided with radial holes communicating with the first body. 
   
   
       5 . A burner according to  claim 4 , wherein said radial holes are arranged at a second end of the second body, preferably at the comburent gas inlet opening. 
   
   
       6 . A burner according to  claim 4 , wherein the fourth tubular body is provided with radial holes communicating with the third body. 
   
   
       7 . A burner according to  claim 6 , wherein said radial holes are arranged at a second end of the fourth body, preferably at the combustible gas inlet opening. 
   
   
       8 . A burner according to  claim 1 , wherein the first, second, third and fourth tubular bodies are cylindrical and coaxial. 
   
   
       9 . A burner according to  claim 1 , wherein in the fourth tubular body there is provided an inlet opening of inert gas for a cooling of the burner. 
   
   
       10 . A burner according to  claim 1 , wherein there are provided two electrodes respectively to ignite and to detect a flame, passing within the second body and accommodated within the diffuser body. 
   
   
       11 . A combustion process in a burner according to  claim 1 , comprising the following stages:
 inlet of comburent gas, through an opening, in a first and a second tubular body in first predetermined proportions,   inlet of combustible gas, through an opening, in a third and a fourth tubular body in second predetermined proportions,   a first combustion stage by means of injection at a first combustion zone of part of the combustible gas through the one or more ports of the third tubular body and of part of the comburent gas through the one or more ports ( 9 ) of the second tubular body,   a second combustion stage by means of injection at a second combustion zone of another part of the combustible gas through the one or more ports of the fourth tubular body and of another part of the comburent gas through the one or more ports of the first tubular body, wherein the first combustion stage occurs with a stoichiometric ratio in high excess of combustible gas so as to reduce the flame temperature and the formation of NO x  and to allow the detection of the flame both when hot and when cold,   and wherein the second combustion stage comprises a recirculation of combustion products of said first stage so as to dilute the combustion again reducing the flame temperature and the formation of NO x .   
   
   
       12 . A combustion process according to  claim 11 , wherein the first predetermined proportions are equal to approximately 50-70% in the first body and to approximately 30-50% in the second body. 
   
   
       13 . A combustion process according to  claim 11 , wherein the second predetermined proportions are equal to approximately 5-35% in the third body and to approximately 65-95% in the fourth body. 
   
   
       14 . A combustion process according to  claim 11 , wherein the outlet speed of the comburent gas from the ports of the first body and the outlet speed of the combustible gas from the one or more ports of the fourth tubular body is such to cause said recirculation of combustion products of the first stage.