Use of hydrocarbon emulsions as a reburn fuel to reduce nox emissions

Abstract

An in-furnace combustion application process method and apparatus reduces nitrogen oxides in flue gas by injecting a bitumen, carbon residue or an asphalt water emulsion or a mixture thereof into flue gas so that the three types of emulsions (injected individually or as a blend) mixes with said flue gas. The emulsions are preferably atomized before injection and may also be injected in jet streams.

1 . A method of reducing NOx emissions from a furnace comprising introducing a hydrocarbon-water emulsion into the flue gas of the furnace in a reburn zone downstream of a primary combustion zone where the hydrocarbon in the emulsion is selected from bitumen, atmospheric residue, heavy fuel oil, vacuum residue, asphalt, solvent de-asphalter, and mixtures thereof. 
   
   
       2 . The method of  claim 1  where a fixed reduced nitrogen compound is added to the emulsion prior to introduction into the furnace. 
   
   
       3 . The method of  claim 2  where the fixed reduced nitrogen compound is urea or aqueous ammonia. 
   
   
       4 . The method of  claim 2  where an amount of fixed reduced nitrogen compound is added such that the number of atoms of reduced nitrogen are in the range of 0.25 to 3 times the number of atoms of NO x  in the primary combustion products. 
   
   
       5 . The method of  claim 1  where the hydrocarbon component of the emulsion is 57 to 99% by weight of the emulsion. 
   
   
       6 . The method of  claim 1  where the hydrocarbon component of the emulsion is 65 to 80% by weight of the emulsion. 
   
   
       7 . The method of  claim 1  where the emulsion is introduced into the flue gas by injection in the form of atomized droplets. 
   
   
       8 . The method of  claim 7  where the atomized droplets comprise an inner hydrocarbon droplet surrounded by an aqueous outer layer. 
   
   
       9 . The method of  claim 7  where the atomized droplets comprise an inner aqueous droplet surrounded by a hydrocarbon outer layer. 
   
   
       10 . The method of  claim 9  where the atomized droplets are from 60 to 300 micrometers in diameter. 
   
   
       11 . The method of  claim 9  where the atomized droplets are from 80 to 300 micrometers in diameter and encase an aqueous droplet of from 5 to 30 microns in diameter. 
   
   
       12 . The method of  claim 8  where the atomized droplets are from 120 to 300 micrometers in diameter and encase a hydrocarbon droplet of from 5 to 20 microns in diameter. 
   
   
       13 . The method of  claim 1  where the flue gas at the point of introduction of the emulsion is at a temperature of from 1900° F. to 2600° F. 
   
   
       14 . The method of  claim 1  where the flue gas at the point of introduction of the emulsion is at a temperature of from 1900° F. to 2200° F. 
   
   
       15 . The method of  claim 1  where the amount of energy input from the hydrocarbon in water emulsion comprises from 1 to 20% of the total energy input to the furnace. 
   
   
       16 . The method of  claim 15  where the amount of energy input from the hydrocarbon in water emulsion comprises from 1 to 7.9% of the total energy input to the furnace and no burnout air is supplied to the furnace. 
   
   
       17 . The method of  claim 15  where the amount of energy input from the hydrocarbon in water emulsion comprises from 8 to 20% of the total energy input to the furnace. 
   
   
       18 . The method of  claim 1  further comprising introducing burn-out air at a location after or downstream of the place where the emulsion is injected.