Scrubber for removing heavy metals from gases

Abstract

A wet scrubber for absorbing a heavy metal from a gas stream, a liquor for said wet scrubber, and a power-plant comprising said wet scrubber are described. The wet scrubber has a liquor containing an oxidizer in ionic liquid. Optionally, the oxidizer has, in pure state, high vapor pressure, and in the ionic liquid, the oxidizer forms a complex that has a much lower vapor pressure. In a preferred embodiment, the liquor is substantially free of any ligand that binds to the metal to be absorbed by the liquor.

1 . A wet scrubber for absorbing elemental heavy metal from a gas stream, the scrubber comprising:
 a vessel having a gas inlet and a gas outlet, and in the vessel,   a liquor comprising:
 an oxidizer capable of oxidizing said elemental heavy metal and 
 an ionic liquid, 
   
       the liquor being substantially free of any ligand capable of binding an ion of the heavy metal. 
     
     
         2 . A wet scrubber according to  claim 1 , wherein said liquor consists essentially of an ionic liquid and an oxidizer. 
     
     
         3 . A wet scrubber according to  claim 1 , comprising a liquid inlet and a liquid outlet, the scrubber being configured to contact liquid with the gas between said liquid inlet and outlet. 
     
     
         4 . A wet scrubber according to  claim 1 , wherein said oxidizer is selected from the group consisting of chlorine dioxide and iodine. 
     
     
         5 . (canceled) 
     
     
         6 . A wet scrubber according to  claim 1 , wherein said ionic liquid comprises a cation and an anion, and said anion is a halide. 
     
     
         7 . A wet scrubber for absorbing, at a working temperature, a heavy metal from a gas stream, the scrubber comprising:
 a vessel having a gas inlet and a gas outlet, and in the vessel,   a liquor comprising:
 an ionic liquid comprising an anion and a cation, and 
 an oxidizing complex capable of oxidizing, at the working temperature, said heavy metal, the oxidizing complex comprising an oxidizing moiety and a complexing agent, said oxidizing complex having, in the liquor, a partial vapor pressure that is at least 10 times smaller than a vapor pressure of the oxidizing moiety in pure state. 
   
     
     
         8 . A wet scrubber according to  claim 7 , wherein said complexing agent is one of said anion and cation. 
     
     
         9 . A wet scrubber according to  claim 7 , wherein said oxidizing moiety is selected from the group consisting of chlorine dioxide and a halogen. 
     
     
         10 .- 11 . (canceled) 
     
     
         12 . A wet scrubber according to  claim 7 , wherein said oxidizing complex is a compound of the general formula X 2 Y − , wherein each of X and Y is independently selected from Br, Cl, and I. 
     
     
         13 . (canceled) 
     
     
         14 . A wet scrubber for absorbing a heavy metal from a gas stream, the scrubber comprising: a vessel having a gas inlet and a gas outlet, a liquid inlet and a liquid outlet, and in the vessel, a liquor moving from the liquid inlet to the liquid outlet, the liquor comprising an ionic liquid and an oxidizer capable of oxidizing the heavy metal. 
     
     
         15 . A wet scrubber according to  claim 14 , comprising a filter configured for separating solids from the liquor exiting from the vessel through the liquid outlet. 
     
     
         16 . A wet scrubber according to  claim 14 , comprising a liquid path configured for feeding said liquid inlet with liquor that has exited from the vessel through the liquid outlet. 
     
     
         17 . A wet scrubber according to  claim 14 , wherein said oxidizer comprises chlorine dioxide or iodine of a halogen-halide complex. 
     
     
         18 .- 19 . (canceled) 
     
     
         20 . A wet scrubber according to  claim 1 , wherein the liquor is in form of a mist. 
     
     
         21 . A wet scrubber according to  claim 1 , wherein the heavy metal is elemental and the ionic liquid has an oxidation potential that is insufficient for oxidizing the elemental heavy metal at the working temperature of the scrubber. 
     
     
         22 .- 24 . (canceled) 
     
     
         25 . A method of scrubbing elemental heavy metal from a gas stream, the method comprising:
 providing a liquor free to move in a vessel, the liquor comprising an ionic liquid and an oxidizer capable of oxidizing the elemental metal; and   directing the gas stream into the vessel so as to contact with the liquor.   
     
     
         26 . A method according to  claim 25 , wherein providing a liquor comprises:
 reacting said ionic liquid with an oxidizing moiety, thereby obtaining a liquor comprising:
 the ionic liquid and an oxidizing complex comprising the oxidizing moiety complexed with an ion of said ionic liquid. 
   
     
     
         27 .- 29 . (canceled) 
     
     
         30 . A method according to  claim 25 , wherein said ionic liquid comprises an anion and a cation, and said anion is selected from chloride, bromide, and iodide. 
     
     
         31 . A method according to  claim 25 , wherein contacting the gas with the liquor comprises bubbling a gas into the liquor or contacting the gas with liquor in the form of droplets or mist. 
     
     
         32 .- 34 . (canceled) 
     
     
         35 . A method according to  claim 25 , comprising:
 separating heavy metal salt from the liquor to obtain a liquor with reduced amount of metal salt; and   using the liquor with reduced amount of metal salt for scrubbing the heavy metal from the gas stream.   
     
     
         36 . A compound of the general formula A + X − Y 2 , wherein
 A + X − , at 25° C., is an ionic liquid; and   X and Y are each independently F, Cl, Br, or I.   
     
     
         37 . A compound according to  claim 36 , wherein A +  is a cyclic tertiary ammonium cation. 
     
     
         38 . A compound according to  claim 36 , wherein A +  is an aromatic cation. 
     
     
         39 . A compound according to  claim 36 , wherein A +  is according to any of the general formulae I-VII, 
       
         
           
           
               
               
           
         
       
       wherein each of R and R′ independently is a C 2 -C 10  alkyl. 
     
     
         40 . A compound according to  claim 36 , wherein A +  is selected from 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, and 1-octyl-3-methylimidazolium. 
     
     
         41 . A compound according to  claim 36 , wherein Y is I. 
     
     
         42 . A compound according to  claim 36 , wherein X is Cl. 
     
     
         43 . A wet scrubber according to  claim 1 , wherein said liquor comprises a compound according to  claim 36 . 
     
     
         44 . A method according to  claim 25 , wherein the liquor comprises a compound according to  claim 36 . 
     
     
         45 .- 48 . (canceled)