Burners

Abstract

The invention provides a nozzle-mixed burner for use in an endothermic process such as hydrogen reforming or ammonia reforming or ethylene cracking or EDC cracking. The burner comprises a fuel duct extending axially through a wall of the furnace. The fuel duct delivers gaseous fuel to an array of nozzles extending laterally to spray the fuel outwardly into an annular chamber defined by a cap. Combustion air is delivered to the chamber by way of a primary air duct. A convergent-divergent section of the duct and an outwardly divergent section of the chamber together form a radially extending venturi. Combustion of the fuel, supplemented by the venturi effect, draws the air through the duct by natural inspiration.

1 . A burner for an endothermic process, which burner comprises a fuel duct having an axially extending portion extending axially forwards from a proximal end to discharge fuel at a distal end and an air duct having an axially extending portion extending axially forwards from said proximal end to discharge combustion air at said distal end, wherein after discharge the discharged fuel burns in the presence of the discharged combustion air and draws the combustion air through the air duct by natural inspiration, wherein the fuel duct has at said distal end a laterally extending portion whereby the fuel is discharged laterally and the air duct has at said distal end a laterally extending portion whereby the combustion air is discharged laterally. 
     
     
         2 . A burner as claimed in  claim 1 , wherein the axially extending portion of the air duct is circumjacent the axially extending portion of the fuel duct. 
     
     
         3 . A burner as claimed in  claim 1 , wherein the air duct comprises at its distal end an annular chamber extending laterally outwards towards a lateral opening for the discharge of the combustion air. 
     
     
         4 . A burner as claimed in  claim 3 , wherein the annular chamber comprises a dished section facing rearwards to turn the combustion air from axial flow through the axially extending portion of the air duct to lateral flow through the laterally extending portion of the air duct. 
     
     
         5 . A burner as claimed in  claim 4 , wherein the annular chamber is divergent towards its lateral opening. 
     
     
         6 . A burner as claimed in  claim 5 , wherein the axially extending portion of the air duct comprises adjacent said distal end a section convergent towards the annular chamber. 
     
     
         7 . A burner as claimed in  claim 3 , wherein the fuel duct comprises at its distal end a plurality of ports extending within the annular chamber towards the lateral opening thereof. 
     
     
         8 . A burner as claimed in  claim 7 , wherein said plurality of ports comprises a first set of ports for a main fuel supply and a second set of ports for a stabilising fuel supply. 
     
     
         9 . A burner as claimed in  claim 8 , wherein the ports of said second set are inclined rearwardly of the ports of the first set. 
     
     
         10 . A burner as claimed in  claim 8 , wherein the fuel duct comprises one fuel passage connected to the first set of ports and a separate second fuel passage connected to the second set of ports. 
     
     
         11 . A burner as claimed in  claim 8 , wherein said plurality of ports comprises a third set of ports for fuel staging. 
     
     
         12 . A burner as claimed in  claim 3 , wherein the lateral opening of the annular chamber comprises a flame stabilisation ring. 
     
     
         13 . A burner as claimed in  claim 1 , wherein the burner comprises a plurality of air control vanes extending across a convergent-divergent section of the axially extending portion of the air duct. 
     
     
         14 . A burner as claimed in  claim 1 , wherein the burner comprises a secondary air duct extending axially from said proximal end to said distal end. 
     
     
         15 . A furnace for an endothermic process, wherein the furnace comprises a plurality of nozzle-mix burners configured and arranged to draw in combustion air by natural inspiration. 
     
     
         16 . A furnace as claimed in  claim 15 , wherein said burners are as claimed in  claim 1  each with the air duct and the fuel duct thereof extending through a wall of the furnace. 
     
     
         17 . A furnace as claimed in  claim 16 , wherein the furnace is configured and arranged to operate within a specified noise limit. 
     
     
         18 . A method of operating a furnace for an endothermic process, wherein the furnace is heated by a plurality of nozzle-mix burners configured and arranged to draw in combustion air by natural inspiration. 
     
     
         19 . A method of operating a furnace as claimed in  claim 18 , wherein said burners are as claimed in  claim 1  each with the air duct and the fuel duct thereof extending through a wall of the furnace. 
     
     
         20 . A method of modifying a furnace equipped with a plurality of wall-mounted burners of the premix type, wherein said method comprises replacing the pre-mix burners with nozzle-mix burners as claimed in  claim 1 .