Methods for the treatment of a flue gas stream using catalytically-enhanced sorbent compositions

Abstract

A sorbent composition that is useful for injection into a flue gas stream of a coal burning furnace to efficiently remove mercury from the flue gas stream. The sorbent composition may include a sorbent with an associated ancillary catalyst component that is a catalytic metal, a precursor to a catalytic metal, a catalytic metal compound or a precursor to a catalytic metal compound. Alternatively, a catalytic metal or metal compound, or their precursors, may be admixed with the coal feedstock prior to or during combustion in the furnace, or may be independently injected into a flue gas stream. A catalytic promoter may also be used to enhance the performance of the catalytic metal or metal compound.

What is claimed is: 
     
         1 . A method for the removal of one or more contaminants from a flue gas stream, the method comprising the steps of:
 combusting a fuel source, the combusting generating a flue gas stream comprising one or more contaminants;   contacting the flue gas stream with a solid sorbent and with an ancillary catalyst component;   maintaining the ancillary catalyst component in contact with the flue gas stream for a period of time sufficient to catalytically oxidize at least a portion of the one or more contaminants and form an oxidized contaminant species; and   sequestering the oxidized contaminant species with the solid sorbent.   
     
     
         2 . The method recited in  claim 1 , wherein the solid sorbent has a mean particle diameter (D50) of not greater than about 25 μm. 
     
     
         3 . The method recited in  claim 1 , wherein the solid sorbent has a mean particle diameter (D50) of not greater than about 20 μm. 
     
     
         4 . The method recited in  claim 1 , wherein the solid sorbent has a mean particle diameter (D50) of not greater than about 15 μm. 
     
     
         5 . The method recited in  claim 1 , wherein the solid sorbent comprises powdered activated carbon. 
     
     
         6 . The method recited in  claim 1 , wherein the ancillary catalyst component comprises a catalytic metal selected from the group consisting of Fe, Cu, Mn, Zn, Pd, Au, Ag, Pt, Ir, V, Ni, Ce, and mixtures thereof. 
     
     
         7 . The method recited in  claim 1 , wherein the ancillary catalyst component comprises a catalytic metal selected from the group consisting of Fe, Cu, Mn, Zn and combinations thereof. 
     
     
         8 . The method recited in  claim 1 , wherein the ancillary catalyst component comprises a catalytic metal compound selected from the group consisting of a metal salt, a metal oxide, a metal halide, a metal hydroxide, a metal carbonate, and combinations thereof. 
     
     
         9 . The method recited in  claim 8 , wherein the catalytic metal compound is selected from the group consisting of copper (II) oxide (CuO), copper (II) chloride (CuCl 2 ), copper (II) nitrate (Cu(NO 3 ) 2 ), copper (II) hydroxide (Cu(OH) 2 ), copper (II) carbonate (CuCO 3 ), iron (III) oxide (Fe 2 O 3 ), iron (III) chloride (FeCl 3 ), iron (III) nitrate (Fe(NO 3 ) 3 ), iron (III) sulfate Fe 2 (SO 4 ) 3 , cerium (IV) oxide (CeO 2 ), manganese (IV) oxide (MnO 2 ), vanadium (V) oxide (V 2 O 5 ), zinc (II) oxide (ZnO) and zinc sulfate (ZnSO 4 ). 
     
     
         10 . The method recited in  claim 1 , further comprising the step of contacting the flue gas stream with a catalytic promoter. 
     
     
         11 . The method recited in  claim 10 , wherein the catalytic promoter comprises a metal selected from the group consisting of alkali metals and alkaline earth metals. 
     
     
         12 . The method recited in  claim 10 , wherein the catalytic promoter comprises a metal selected from the group consisting of Al, Li, Na, K, Be, Ca, Sr, Ba, Sc, Y, Mg and combinations thereof. 
     
     
         13 . The method recited in  claim 1 , wherein the flue gas stream is contacted with the solid sorbent and with the ancillary catalyst component in the absence of any added halogen. 
     
     
         14 . The method recited in  claim 1 , wherein the one or more contaminants comprises mercury. 
     
     
         15 . The method recited in  claim 1 , wherein the solid sorbent comprises powdered activated carbon. 
     
     
         16 . The method recited in  claim 1 , wherein the ancillary catalyst component is dispersed on the solid sorbent to form a sorbent composition comprising catalytically active sorbent particles. 
     
     
         17 . The method recited in  claim 1 , wherein the ancillary catalyst component is physically separate from the solid sorbent when contacted with the flue gas stream. 
     
     
         18 . The method recited in  claim 17 , wherein the ancillary catalyst component or a precursor to the ancillary catalyst component is injected into the flue gas stream separate from the solid sorbent. 
     
     
         19 . The method recited in  17 , wherein the ancillary catalyst component or a precursor to the ancillary catalyst component is added to the fuel source before or during combustion of the fuel source. 
     
     
         20 . The method recited in  claim 1 , wherein the fuel source comprises coal.