Methods of Manufacturing Bentonite Polution Control Sorbents

Abstract

Methods of manufacturing bentonite sorbents for removal of pollutants including mercury from gas streams, such as a flue gas stream from coal-fired utility plants are disclosed. The methods include mixing bentonite sorbent particles with a sulfide salt and a metal salt to form a metal sulfide on the outer surface of the bentonite sorbent particles.

1 . A method of removing pollutants from a flue gas stream comprising injecting a sorbent into a coal-fired boiler flue gas stream, the sorbent comprising bentonite particles having a metal sulfide dispersed on the surface of the particles by a grinding, milling or incipient wetness process. 
   
   
       2 . The method of  claim 1 , wherein the pollutants include mercury. 
   
   
       3 . The method of  claim 1 , wherein the metal sulfide is the reaction product of a metal salt and a sulfide salt. 
   
   
       4 . The method of  claim 3 , wherein the reaction product is an in situ reaction product. 
   
   
       5 . The method of  claim 1 , wherein the bentonite particles have an average size less than about 80 μm. 
   
   
       6 . The method of  claim 3 , wherein the metal salts are salts selected from the group consisting of alkaline, alkaline earth metals and metals having an atomic number in the range of 21 to 30, 38 to 50 and 56 to 79, and combinations thereof. 
   
   
       7 . The method of  claim 6 , wherein the metal salt includes a metal selected from the group consisting of copper, titanium, tin, iron, manganese and mixtures thereof. 
   
   
       8 . The method of  claim 6 , wherein the metal salt is selected from the group consisting of nitrate, chloride, sulfate, acetate salts and mixtures thereof. 
   
   
       9 . The method of  claim 1 , wherein the loading level of the metal sulfide is in the range of about 1 to about 20 weight percent. 
   
   
       10 . The method of  claim 3 , wherein the sulfide salt is a sulfide precursor that forms a S 2−  anion. 
   
   
       11 . The method of  claim 10 , wherein the sulfide salt is selected from the group consisting of Na 2 S and (NH 4 ) 2 S. 
   
   
       12 . The method of  claim 1 , wherein the metal sulfide is selected from the group consisting of copper sulfides, tin sulfides, manganese sulfides, titanium sulfides and iron sulfides. 
   
   
       13 . A method of removing pollutants from a flue gas stream comprising:
 preparing sorbent particles by mixing a solid metal salt with bentonite particles, adding a sulfide salt into the mixture using a grinding process, milling process or an incipient wetness process so that the metal salt and sulfide salt react to form a metal sulfide on the surface of the bentonite particles, and drying the mixture; and   injecting the sorbent particles into a coal-fired boiler flue gas stream.   
   
   
       14 . The method of  claim 13 , wherein the method does not utilize ion exchange to form the metal sulfide on the surface of the particles. 
   
   
       15 . The method of  claim 13 , wherein the metal sulfide forms in situ on the particles. 
   
   
       16 . The method of  claim 13 , wherein the metal salts are salts selected from the group consisting of alkaline, alkaline earth metals and metals having an atomic number in the range of 21 to 30, 38 to 50 and 56 to 79, and combinations thereof. 
   
   
       17 . The method of  claim 13 , wherein the sulfide salt is a sulfide precursor that forms a S 2−  anion. 
   
   
       18 . The method of  claim 13 , further comprising reducing the average particle of the particles to less than about 80 μm.