Method for combustion of pulverized coal with reduced emissions

Abstract

Methods of reducing the NOx emissions generated from the burning of pulverized coal in a heat-producing unit, wherein the method comprises the steps of: (a) introducing pulverized coal into a combustion chamber of the heat-producing unit; and (b) co-firing the pulverized coal with an oxygenate source selected from glycerol, glycerol derivatives, propylene glycol, propylene glycol derivatives, ethylene glycol, ethylene glycol derivatives, fatty acid alkyl esters, fatty alcohols, and mixtures thereof, where the combustion of the oxygenate source generates at least 2.5%, on a heat input basis, of the total heat generated by the co-firing.

1 . A method of reducing the NOx emissions generated from the burning of pulverized coal in a heat-producing unit, wherein said method comprises the steps of: 
 a) introducing pulverized coal into a combustion chamber of the heat-producing unit; and    b) co-firing the pulverized coal with an oxygenate source selected from the group consisting of glycerol, propylene glycol, propylene glycol derivatives, ethylene glycol, ethylene glycol derivatives, fatty acid alkyl esters, fatty alcohols, and mixtures thereof;    wherein combustion of the oxygenate source generates at least 2.5%, on a heat input basis, of the total heat generated by the co-firing.    
   
   
       2 . A method according to  claim 2  wherein the oxygenate source is selected from the group consisting of glycerol derivatives, propylene glycol derivatives, ethylene glycol derivatives, fatty acid alkyl esters, and mixtures thereof.  
   
   
       3 . A method according to  claim 2  wherein the glycerol derivative is selected from the group consisting of glycerol ethers in which 1 to 3 of the glycerol hydroxyl groups have been etherified.  
   
   
       4 . A method according to  claim 2  wherein the glycerol derivative is selected from the group consisting of di t-butyl glycerol ethers, tri t-butyl glycerol ethers, solketal, and mixtures thereof.  
   
   
       5 . A method according to  claim 1  wherein the oxygenate is selected from the group consisting of methyl esters of fatty acids, and mixtures thereof.  
   
   
       6 . A method according to  claim 1  wherein the heat-producing unit is a coal-burning boiler.  
   
   
       7 . A method according to  claim 1  wherein the heat-producing unit is a coal-burning furnace.  
   
   
       8 . A method according to  claim 1  wherein the pulverized coal and the oxygenate source are introduced into the combustion chamber through separate injection devices.  
   
   
       9 . A method according to  claim 1  wherein the pulverized coal and the oxygenate source are burned substantially concurrently.  
   
   
       10 . A method according to  claim 6  wherein the boiler comprises an air supply system, a flue-gas cooling chamber, and a stack.  
   
   
       11 . A method according to 6 wherein the boiler comprises a low-NOx burner co-located with the combustion chamber and further comprises air fired downstream of burner air selected from the group consisting of secondary air flows, tertiary air flows, and mixtures thereof.  
   
   
       12 . A method according to  claim 1  wherein combustion of the oxygenate source generates from about 2.5% to about 40%, on a heat input basis, of the total heat generated by the co-firing.  
   
   
       13 . A method according to  claim 12  wherein the oxygenate source is a mixture of di t-butyl and tri t-butyl glycerol ethers.  
   
   
       14 . A method according to  claim 1  wherein the composition further comprises a secondary oxygenate source selected from the group consisting of oils, fats, fatty acids, and mixtures thereof.