Mercury removal from water

Abstract

Methods and apparatus relate to removal of mercury from water. The removal relies on transferring mercury from an aqueous stream to a natural gas stream upon contacting the aqueous stream with the natural gas stream. Processing of the natural gas stream after used to strip the mercury from the aqueous stream removes the mercury from the natural gas stream.

1 . A method, comprising:
 separating crude production into a gaseous hydrocarbon stream, a liquid hydrocarbon stream and an aqueous stream, wherein water forms a majority of the aqueous stream;   removing mercury from a contaminated gas stream including the gaseous hydrocarbon stream to provide a treated gas stream; and   contacting the treated gas stream with the aqueous stream to transfer mercury from the aqueous stream to the treated gas stream such that mercury removal from the aqueous stream is independent from the liquid hydrocarbon stream.   
     
     
         2 . The method according to  claim 1 , further comprising adding a reducing agent to the aqueous stream such that mercury-containing compounds in the aqueous stream are converted to form elemental mercury. 
     
     
         3 . The method according to  claim 1 , further comprising adding stannous chloride to the aqueous stream. 
     
     
         4 . The method according to  claim 1 , further comprising filtering the aqueous stream that has been contacted with the treated gas stream, wherein the filtering removes particles that include residual mercury. 
     
     
         5 . The method according to  claim 1 , further comprising adding a reducing agent to the aqueous stream and filtering the aqueous stream that has been contacted with the treated gas stream. 
     
     
         6 . The method according to  claim 1 , wherein the contaminated gas stream further includes a recycle stream formed of vapor effluent from the contacting of the treated gas stream with the aqueous stream. 
     
     
         7 . The method according to  claim 1 , further comprising contacting the treated gas stream with the liquid hydrocarbon stream to transfer mercury from the liquid hydrocarbon stream to the treated gas stream. 
     
     
         8 . The method according to  claim 1 , further comprising transferring mercury from a mixture of the liquid hydrocarbon stream and the aqueous stream to the treated gas stream, wherein the transferring is separate from and prior to the contacting of the treated gas stream with the aqueous stream. 
     
     
         9 . The method according to  claim 1 , wherein removing mercury from the contaminated gas stream comprises introducing the contaminated gas stream into a mercury-sorbent based removal unit. 
     
     
         10 . The method according to  claim 1 , further comprising removing mercury within vapor effluent from the contacting of the treated gas stream with the aqueous stream. 
     
     
         11 . The method according to  claim 1 , wherein clean water discharge formed of liquid effluent from the contacting of the treated gas stream with the aqueous stream contains less than 10 weight percent of elemental mercury contained in the aqueous stream. 
     
     
         12 . A method, comprising:
 adding a reducing agent to an aqueous stream such that mercury-containing compounds in the aqueous stream are converted to form elemental mercury;   transferring the elemental mercury from the aqueous stream to a methane-containing gas stream, wherein the transferring occurs upon contacting the gas stream with the aqueous stream combined with the reducing agent; and   removing the elemental mercury from the gas stream.   
     
     
         13 . The method according to  claim 12 , wherein the reducing agent is at least one of stannous chloride, sodium borohydride, and hydrazine. 
     
     
         14 . The method according to  claim 12 , wherein the reducing agent comprises stannous chloride. 
     
     
         15 . The method according to  claim 12 , further comprising separating crude production into the aqueous stream and vapors that form at least part of the gas stream upon being treated to remove mercury. 
     
     
         16 . The method according to  claim 12 , further comprising filtering the aqueous stream that has been contacted with the gas stream, wherein the filtering removes particles that include residual mercury. 
     
     
         17 . A method, comprising:
 separating crude production into a gaseous hydrocarbon stream, a liquid hydrocarbon stream and an aqueous stream, wherein water forms a majority of the aqueous stream;   transferring mercury from the liquid hydrocarbon stream to a first portion of a treated gas stream by contacting the first portion of the treated gas stream with the liquid hydrocarbon stream;   transferring mercury from the aqueous stream to a second portion of the treated gas stream by contacting the second portion of the treated gas stream with the aqueous stream independent of the first portion of the treated gas stream being contacted with the liquid hydrocarbon stream; and   forming the treated gas stream by removing mercury from the gaseous hydrocarbon stream mixed with the first and second portions of the treated gas stream recycled after the contacting with the liquid hydrocarbon and aqueous streams.   
     
     
         18 . The method according to  claim 17 , further comprising adding a reducing agent to the aqueous stream such that mercury-containing compounds in the aqueous stream are converted to form elemental mercury. 
     
     
         19 . The method according to  claim 17 , further comprising filtering the aqueous stream that has been contacted with the second portion of the treated gas stream, wherein the filtering removes particles that include residual mercury. 
     
     
         20 . The method according to  claim 17 , wherein the transferring mercury from the liquid hydrocarbon stream to the first portion of the treated gas stream occurs while the liquid hydrocarbon stream and the aqueous stream are mixed together.