Filter system

Abstract

The present invention is an improved filtration system, filtering method and unique chemical composition for capturing mercury and other pollutants in flue gases generated by process gas streams. The improved filtration system may take various forms depending on the type of filter system most desired for a particular application; however, the filter system includes at least a filter element or elements and an adsorbent component having a composition suitable for capturing mercury on the downstream side of the filter element.

We claim:  
     
         1 . A composition comprising: 
 a binding agent comprising at least one binding compound having a component selected from the group consisting of an anion of a halide, an anion of a thiocyanate, an anion of a sulfide, an anion of a polysulfide, an anion of selenium, an oxyanion of selenium, an anion of tellurium, an oxyanion of tellurium, an anion of phosphorus, and an oxyanion of phosphorus; and    a promoter comprising at least one promoter compound having a component selected from a multivalent metallic cation and a multivalent metalloid cation, said promoter compound having a standard aqueous reduction potential Emf value at 25° C. less than −0.56 volts,    wherein said composition is capable of chemical reaction with elemental and oxidized mercury to bind said elemental and oxidized mercury.    
     
     
         2 . The composition of  claim 1 , wherein said promoter comprises at least one material selected from the group consisting of a carboxylate salt of Zn (II) and a carboxylate salt of Mg (II).  
     
     
         3 . The composition of  claim 1 , wherein said binding agent comprises at least one compound selected from the group consisting of potassium iodide, copper iodide, zinc iodide and copper thiocyanate.  
     
     
         4 . The composition of  claim 1 , wherein said binding agent comprises potassium iodide and said promoter comprises zinc acetate.  
     
     
         5 . A composition comprising the reaction product of mercury, potassium iodide and zinc acetate.  
     
     
         6 . A composition comprising 
 (a) an air-permeable high surface area support having thereon    (b) a binding agent comprising at least one binding compound having a component selected from the group consisting of an anion of a halide, an anion of a thiocyanate, an anion of a sulfide, an anion of a polysulfide, an anion of selenium, an oxyanion of selenium, an anion of tellurium, an oxyanion of tellurium, an anion of phosphorus, and an oxyanion of phosphorus; and    (c) a promoter comprising at least one promoter compound having a component selected from a multivalent metallic cation and a multivalent metalloid cation, said promoter compound having a standard aqueous reduction potential Emf value at 25° C. less than −0.56 volts, 
 wherein said composition is capable of chemical reaction with elemental and oxidized mercury to bind said elemental and oxidized mercury.  
   
     
     
         7 . A composition comprising 
 activated carbon having thereon potassium iodide and zinc acetate.    
     
     
         8 . A composition comprising 
 activated carbon having thereon the reaction product of potassium iodide, zinc acetate and mercury.    
     
     
         9 . An article comprising: 
 an air permeable high surface area support material; and    a coating on at least a portion of said high surface area support material comprising (1) a binding agent comprising at least one binding compound having a component selected from the group consisting of an anion of a halide, an anion of a thiocyanate, an anion of a sulfide, an anion of a polysulfide, an anion of selenium, an oxyanion of selenium, an anion of tellurium, an oxyanion of tellurium, an anion of phosphorus, and an oxyanion of phosphorus; and (2) a promoter comprising at least one promoter compound having a component selected from a multivalent metallic cation and a multivalent metalloid cation, said promoter compound having a standard aqueous reduction potential Emf value at 25° C. less than −0.56 volts.    
     
     
         10 . The article of  claim 9 , wherein said porous support material comprises activated carbon.  
     
     
         11 . The article of  claim 9 , wherein said article is in the form of a tube.  
     
     
         12 . The article of  claim 9 , wherein said article is in the form of a flat sheet.  
     
     
         13 . The article of  claim 9 , wherein said article is pleated.  
     
     
         14 . The article of  claim 9 , wherein said article is in the form of a canister.  
     
     
         15 . The article of  claim 9 , wherein said porous support material comprises an activated carbon fiber felt.  
     
     
         16 . The article of  claim 9 , wherein said article is rigid.  
     
     
         17 . The article of  claim 9 , wherein said article is flexible.  
     
     
         18 . The article of  claim 9 , wherein said air permeable high surface area support material comprises a fluoropolymer material filled with a high surface area component.  
     
     
         19 . An article comprising a rigid tube of activated carbon having a coating on at least a portion thereof, said coating comprising potassium iodide and zinc acetate.  
     
     
         20 . The article of  claim 9 , wherein said high surface area support material comprises at least one of woven and nonwoven fibers selected from the group consisting of glass and mineral, said fibers having thereon a coating of a high surface area component.  
     
     
         21 . The article of  claim 20 , wherein said high surface area component comprises activated carbon.  
     
     
         22 . The article of  claim 1  in the form of an insert for a filter element.  
     
     
         23 . An article comprising: 
 an air permeable high surface area support material comprising activated carbon; and    a coating on said support material comprising a binding agent comprising potassium iodide and a promoter comprising zinc acetate.    
     
     
         24 . A filter system comprising 
 at least one particulate collection filter element; and    an insert oriented on the downstream side of said at least one particulate collection filter element, said insert comprising a high surface area support material having on at least a portion thereof a coating composition comprising a binding agent and a promoter, whereby said composition is capable of chemical reaction with elemental and oxidized mercury to bind said elemental and oxidized mercury.    
     
     
         25 . A filter system comprising 
 at least one particulate collection filter element selected from a filter bag and a filter cartridge; and    a removable insert oriented within said at least one particulate collection filter element, said insert comprising a high surface area support material having on at least a portion thereof a coating composition comprising a binding agent and a promoter, whereby said composition is capable of chemical reaction with elemental and oxidized mercury to bind said elemental and oxidized mercury.    
     
     
         26 . The filter system of  claim 24 , wherein said filter element comprises a depth filtration element.  
     
     
         27 . The filtration system of  claim 24 , wherein said filter element comprises a surface filtration element.  
     
     
         28 . The filter system of  claim 24 , wherein said filter element comprises an expanded PTFE membrane.  
     
     
         29 . The filter system of  claim 24 , wherein said coating on said air permeable high surface area support material comprises a binding agent comprising potassium iodide and a promoter comprising zinc acetate.  
     
     
         30 . A filter system comprising 
 at least one particulate collection filter element; and    a mercury collecting filter element oriented separate from and downstream of said particulate collection filter element, said mercury collecting filter element comprising a high surface area support material having on at least a portion thereof a coating composition comprising a binding agent and a promoter, whereby said composition is capable of chemical reaction with elemental and oxidized mercury to bind said elemental and oxidized mercury.    
     
     
         31 . The filter system of  claim 30 , wherein said mercury collection filter element is in the form of a panel filter array.  
     
     
         32 . A filter element comprising 
 an air permeable high surface area support material having on at least a portion thereof a coating composition comprising a binding agent and a promoter, whereby said composition is capable of chemical reaction with elemental and oxidized mercury to bind said elemental and oxidized mercury; and    a sheet of microporous membrane mounted on at least one side of the porous support material, the sheet having a pore structure sufficiently small enough to serve as a barrier to isolate particles in the fluid stream away from the porous support material.    
     
     
         33 . A method of separating particulates and heavy metals from a gas stream comprising: 
 providing a filter system comprising at least one particulate collection filter element; and a mercury collecting filter element oriented downstream of said particulate collection filter element, said mercury collecting filter element comprising an air permeable high surface area support material having on at least a portion thereof a coating composition comprising a binding agent and a promoter, whereby said composition is capable of chemical reaction with elemental and oxidized mercury to bind said elemental and oxidized mercury;    placing said filter system in a gas stream with the particulate collection filter element oriented in an upstream position relative to the mercury collecting filter element to collect the particles suspended in the gas stream;    whereby said particulate is collected on said particulate filter element and said elemental and oxidized mercury is collected downstream of said particulate filter element by said mercury collecting filter element.