Reducing environmental pollution and fouling when burning coal

Abstract

Powder components containing calcium, alumina, silica, iron, magnesium, and a halogen sorbent are used in combination during coal combustion to produce environmental benefits. Sorbents are added to the coal ahead of combustion and/or are added into the flame or downstream of the flame. The alkalinity and chlorine of the powder is minimized in order to mitigate unwanted fouling, especially when used with sub-bituminous and lignite coals.

What is claimed: 
     
         1 . A method of burning coal in a furnace to reduce emissions of NO x  and at least one of SO x  and mercury, the method comprising burning a refined coal in the furnace, wherein the refined coal comprises an admixture of sub-bituminous coal or lignite coal, bromine compound, and a powder sorbent, and
 wherein the powder sorbent comprises calcium, silica, alumina, and further comprises less than 1% by weight Na 2 O and less than 1% by K 2 O, based on the weight of the powder sorbent.   
     
     
         2 . A method according to  claim 1 , wherein the powder sorbent comprises less than 0.5% Na 2 O and less than 0.5% K 2 O. 
     
     
         3 . A method according to  claim 1 , wherein the coal is Powder River Basin coal. 
     
     
         4 . A method according to  claim 1 , wherein the refined coal comprises 0.001 to 1.0% by weight bromine compound and 0.1 to 10% by powder sorbent. 
     
     
         5 . A method according to  claim 4 , wherein the refined coal comprises 0.002 to 1.0% by weight of the bromine compound and 0.1 to 2.0% by weight of the powder sorbent. 
     
     
         6 . A method according to  claim 1 , wherein the powder sorbent comprises cement kiln dust (CKD). 
     
     
         7 . A method according to  claim 6 , wherein the powder sorbent comprises grind outs, CKD and one or more of kiln feed, transition cement, weathered clinker, impound CKD, and limestone. 
     
     
         8 . A method according to  claim 1 , wherein the powder sorbent comprises greater than 40% CaO, greater than 10% SiO 2 , 2 to 10% Al 2 O 3 , 1 to 5% Fe 2 O 3 , and 1 to 5% MgO, wherein the percentages are by weight based on the weight of the powder sorbent. 
     
     
         9 . A method according to  claim 1 , wherein the powder sorbent comprises CKD and grind outs. 
     
     
         10 . A method according to  claim 1 , wherein the powder sorbent comprises CKD and aluminosilicate clay. 
     
     
         11 . A method according to  claim 1 , wherein the powder sorbent comprises CKD and kaolin. 
     
     
         12 . A method according to  claim 1 , wherein the powder sorbent comprises less than 0.5% chlorine. 
     
     
         13 . A method of generating energy through combustion of mercury-containing sub-bituminous coal in the furnace of a coal burning facility comprising;
 applying a first sorbent composition onto the coal;   delivering the coal with the applied first sorbent into the furnace;   adding a second sorbent into the furnace as the coal is being delivered; and   combusting the coal in the presence of the first and second sorbents in the furnace to produce heat energy and ash,   
       wherein the first sorbent comprises a bromine compound and the second sorbent comprises greater than 40% CaO, greater than 10% SiO 2 , 2 to 10% Al 2 O 3 , 1 to 5% Fe 2 O 3 , and 1 to 5% MgO, less than 1% Na 2 O, less than 1% K 2 O, and less than 0.5% by weight chlorine, wherein the percentages are by weight based on the total weight of the second sorbent. 
     
     
         14 . The method according to  claim 13 , wherein the second sorbent comprises less than 0.5% Na 2 O and less than 0.5% K 2 O. 
     
     
         15 . The method according to  claim 13 , wherein the first sorbent is a aqueous solution of calcium bromide. 
     
     
         16 . The method according to  claim 13 , comprising adding calcium bromide at a rate of 0.001 to 0.5%, based on the amount of coal being burned. 
     
     
         17 . The method according to  claim 13 , wherein mercury emissions from the coal burning facility are reduced by 40% or greater compared to burning the coal without the first and second sorbents. 
     
     
         18 . The method according to  claim 13 , wherein emissions of NO x  from the coal burning facility are reduced by greater than or equal to 20%, compared to burning the coal without the first and second sorbent. 
     
     
         19 . The method according to  claim 13 , wherein the coal is Powder River Basin (PRB) coal. 
     
     
         20 . The method according to  claim 13 , wherein the second sorbent comprises CKD and grind outs. 
     
     
         21 . The method according to  claim 13 , wherein the second sorbent comprises CKD and one or more of grind outs, kiln feed, transition cement, weathered clinker, impound CKD, and limestone. 
     
     
         22 . The method according to  claim 13 , comprising adding the second sorbent at a rate of 0.1 to 10% y weight, based on the weight of the coal being consumed. 
     
     
         23 . A method of making a refined coal comprising sub-bituminous coal or lignite coal, and further comprising sorbent components, the method comprising admixing the coal, 0.001-1 wt % of a liquid sorbent, and 0.1 to 10% by weight of a powder sorbent, wherein the percentages are by weight based on the total weight of the refined coal, wherein the liquid sorbent comprises a bromine compound and the powder sorbent comprises calcium, silica, alumina, and further comprises less than 1% Na 2 O by weight and less than 1% K 2 O by weight, and wherein the powder sorbent further comprises less than 0.1% by weight chlorine. 
     
     
         24 . The method according to  claim 23 , carried out in a batch process. 
     
     
         25 . The method according to  claim 23 , carried out as a continuous process. 
     
     
         26 . The method according to  claim 23 , wherein the liquid sorbent is an aqueous solution of calcium bromide. 
     
     
         27 . The method according to  claim 23 , wherein the powder sorbent comprises less than 0.5% Na 2 O and less than 0.5% K 2 O. 
     
     
         28 . The method according to  claim 23 , wherein the powder sorbent comprises CKD and one or more of grind outs, kiln feed, transition cement, weathered clinker, impound CKD, and limestone. 
     
     
         29 . The method according to  claim 23 , wherein the powder sorbent comprises CKD, limestone, and alumina silicate clay. 
     
     
         30 . The method according to  claim 23 , wherein the powder sorbent comprises kaolin. 
     
     
         31 . The method according to  claim 23 , wherein the powder sorbent comprises metakaolin. 
     
     
         32 . The method according to  claim 23 , wherein the coal is PRB coal.