Fuel dilution for reducing NOx production

Abstract

A combustion device and combustion method for mixing a fuel and a fluid to form a diluted fuel mixture and passing the diluted fuel mixture through a nozzle. The nozzle comprises a nozzle body having an inlet face, an outlet face, and an inlet flow axis passing through the inlet face and the outlet face, and one or more slots extending through the nozzle body from the inlet face to the outlet face, each slot having a slot axis.

1 . A combustion method comprising: 
 mixing a first substantially gaseous fuel having a first fuel index and a fluid having a second fuel index which is different than the first fuel index in a conduit thereby forming a diluted fuel mixture; and    passing the diluted fuel mixture through a nozzle, the nozzle comprising: 
 a nozzle body having an inlet face, an outlet face, and an inlet flow axis passing through the inlet face and the outlet face; and  
 one or more slots extending through the nozzle body from the inlet face to the outlet face, each slot having a slot axis.  
   
   
   
       2 . The combustion method of  claim 1  wherein the nozzle comprises two or more slots extending through the nozzle body from the inlet face to the outlet face.  
   
   
       3 . The combustion method of  claim 1  wherein the second fuel index is less than the first fuel index by at least 0.1.  
   
   
       4 . The combustion method of  claim 1  wherein the fluid is a second substantially gaseous fuel.  
   
   
       5 . The combustion method of  claim 1  wherein the fluid is selected from the group consisting of steam, carbon monoxide, carbon dioxide, nitrogen, argon, helium, xenon, krypton and mixtures thereof.  
   
   
       6 . The combustion method of  claim 1  wherein the fluid comprises flue gas.  
   
   
       7 . The combustion method of  claim 1  wherein the fluid comprises hydrogen PSA offgas.  
   
   
       8 . The combustion method of  claim 1  wherein the first substantially gaseous fuel comprises refinery offgas, natural gas, or hydrogen PSA offgas.  
   
   
       9 . The combustion method of  claim 1  wherein the first substantially gaseous fuel comprises methane or propane.  
   
   
       10 . The combustion method of  claim 1  further comprising: 
 introducing an oxidant gas; and    combusting at least a portion of the diluted fuel mixture with at least a portion of the oxidant gas.    
   
   
       11 . The combustion method of  claim 1  further comprising: 
 entraining a furnace gas in at least a portion of the diluted fuel mixture in a furnace thereby forming a furnace gas entrained fuel mixture;    introducing an oxidant gas; and    combusting at least a portion of the furnace gas entrained fuel mixture with at least a portion of the oxidant gas.    
   
   
       12 . The combustion method of  claim 1  further comprising: 
 swirling at least one of the first substantially gaseous fuel and the fluid prior to mixing the first substantially gaseous fuel and the fluid.    
   
   
       13 . The combustion method of  claim 1  wherein the diluted fuel mixture has a residence time in the conduit and the residence time is 0.1 to 10 milliseconds.  
   
   
       14 . A combustion device comprising: 
 a first conduit portion for conveying a fuel;    a second conduit portion for conveying a fluid which is different from the fuel;    a mixing conduit in fluid communication with the first conduit portion and in fluid communication with the second conduit portion for mixing the fuel and the fluid to form a diluted fuel mixture; and    a nozzle in fluid communication with the mixing conduit for passing the diluted fuel mixture therethrough, the nozzle comprising: 
 a nozzle body having an inlet face, an outlet face, and an inlet flow axis passing through the inlet face and the outlet face; and  
 one or more slots extending through the nozzle body from the inlet face to the outlet face, each slot having a slot axis.  
   
   
   
       15 . The combustion device of  claim 14  wherein the nozzle comprises two or more slots extending through the nozzle body from the inlet face to the outlet face.  
   
   
       16 . The combustion device of  claim 15  wherein the slot axis of at least one of the slots is not parallel to the inlet flow axis of the nozzle body.  
   
   
       17 . The combustion device of  claim 15  wherein the slot axes of at least two slots are not parallel to each other.  
   
   
       18 . The combustion device of  claim 15  wherein at least two of the slots intersect each other.  
   
   
       19 . The combustion device of  claim 15  wherein none of the slots intersect.  
   
   
       20 . The combustion device of  claim 15  having three or more slots wherein a first slot of the three or more slots intersects with a second slot of the three or more slots and a third slot of the three or more slots.  
   
   
       21 . The combustion device of  claim 15  having four or more slots wherein a first slot and a second slot intersect each other and a third slot and a fourth slot intersect each other.  
   
   
       22 . The combustion device of  claim 14 , wherein the first conduit portion is disposed within the second conduit portion.  
   
   
       23 . The combustion device of  claim 22 , wherein the first conduit portion has an outlet, the outlet of the first conduit portion has an equivalent diameter, and the mixing conduit has a length in a range of 2 to 20 times the equivalent diameter of the outlet of the first conduit portion.  
   
   
       24 . The combustion device of  claim 14 , wherein the second conduit portion is disposed within the first conduit portion.  
   
   
       25 . The combustion device of  claim 24 , wherein the second conduit portion has an outlet, the outlet of the second conduit portion has an equivalent diameter, and the mixing conduit has a length in a range of 2 to 20 times the equivalent diameter of the outlet of the second conduit portion.  
   
   
       26 . The combustion device of  claim 14 , wherein the first conduit portion is not disposed within the second conduit portion and the second conduit portion is not disposed within the first conduit portion.  
   
   
       27 . The combustion device of  claim 14 , further comprising a swirling means in at least one of the first conduit portion and the second conduit portion.