Sorbent compositions and methods for the removal of contaminants from a gas stream

Abstract

A sorbent composition for the sequestration of mercury from a gas stream, a method for sequestering mercury from a gas stream and a method for the manufacture of a sorbent composition. The sorbent composition includes a highly porous particulate sorbent and at least two additive components, namely a non-halogen metal compound comprising a metal cation and an inorganic sulfur-containing compound, where at least a portion of the sulfur in the sulfur-containing compound has an oxidation state of equal to or less than +4. The method includes injecting the highly porous particulate sorbent and the two additive components into a gas stream, either discretely or as a single sorbent composition, to sequester mercury in the particulate sorbent. The method has a high degree of efficacy for mercury removal without requiring the addition of halogens to the gas stream.

1 . A method for the treatment of a gas stream to capture contaminants from the gas stream, comprising the steps of:
 contacting the gas stream with a particulate sorbent to disperse the particulate sorbent within the gas stream;   contacting the gas stream with a non-halogen metal compound comprising a metal cation;   contacting the gas stream with an inorganic sulfur-containing compound, wherein at least a portion of the sulfur in the sulfur-containing compound has an oxidation state of equal to or less than +4; and   separating the particulate sorbent from the gas stream.   
     
     
         2 . The method recited in  claim 1 , wherein each of the contacting steps are carried out by contacting the gas stream with a sorbent composition comprising the particulate sorbent, the non-halogen metal compound and the inorganic sulfur-containing compound. 
     
     
         3 . The method recited in  claim 2 , wherein the sorbent composition comprises not greater than about 0.5 wt. % halogens. 
     
     
         4 . The method recited in  claim 2 , wherein the sorbent composition comprises not greater than about 0.1 wt. % halogens. 
     
     
         5 . The method recited in  claim 2 , wherein the sorbent composition comprises substantially no halogens. 
     
     
         6 . The method recited in  claim 2 , wherein the sorbent composition is in the form of free-flowing particulates, and wherein the contacting steps comprise injecting the free-flowing sorbent composition particulates into the gas stream. 
     
     
         7 . The method recited in  claim 1 , wherein the step of contacting the gas stream with a particulate sorbent comprises injecting the particulate sorbent into the gas stream. 
     
     
         8 . The method recited in  claim 7 , wherein the step of contacting the gas stream with the inorganic sulfur-containing compound comprises injecting the inorganic sulfur-containing compound into the gas stream. 
     
     
         9 . The method recited in  claim 8 , wherein the inorganic sulfur-containing compound is injected into the gas stream as a discrete component. 
     
     
         10 . The method recited  claim 7 , wherein the step of contacting the gas stream with the non-halogen metal compound comprises injecting the non-halogen metal compound into the gas stream. 
     
     
         11 . The method recited in  claim 10 , wherein the non-halogen metal compound is injected into the gas stream as a discrete component. 
     
     
         12 . The method recited in  claim 1 , wherein the gas stream is a gas stream emanating from a boiler. 
     
     
         13 . The method recited in  claim 1 , wherein the gas stream is a gas stream emanating from a coal-fired boiler. 
     
     
         14 . The method recited in  claim 1 , wherein the contaminants comprise mercury. 
     
     
         15 . A method for the treatment of a gas stream to capture contaminants from the gas stream, comprising the steps of:
 receiving the gas stream comprising mercury;   contacting a sorbent composition with the gas stream, wherein the sorbent composition comprises a particulate sorbent, a non-halogen metal compound, and a sulfur containing compound; and   separating at least a portion of the mercury from the gas stream based at least in part on the sorbent composition.   
     
     
         16 . The method recited in  claim 15 , wherein the step of contacting the gas stream with the sorbent composition comprises injecting the sorbent composition into the gas stream. 
     
     
         17 . The method recited in  claim 15 , wherein the particulate sorbent, the non-halogen metal compound, and the sulfur containing compound of the sorbent composition are discrete components. 
     
     
         18 . A method for the treatment of a gas stream to capture mercury from the gas stream, comprising the steps of:
 receiving, from a boiler, the gas stream comprising mercury;   contacting a sorbent composition with the gas stream, wherein the sorbent composition comprises a particulate sorbent, a non-halogen metal compound, and a sulfur-containing compound, wherein the sorbent composition is contacted with the gas stream before or after the gas stream passes through a preheater unit; and   separating at least a portion of the mercury from the gas stream based at least in part on the sorbent composition.   
     
     
         19 . The method recited in  claim 18 , wherein one or more of the particulate sorbent, the non-halogen metal compound, and the sulfur-containing compound of the sorbent composition is contacted with the gas stream before passing the gas stream through the preheater unit, after passing the gas stream through the preheater unit, or a combination thereof. 
     
     
         20 . The method recited in  claim 18 , wherein the step of separating at least the portion of the mercury from the gas comprises passing the gas stream through a particulate collection device that separates the sorbent composition from the gas stream.