Method and system for converting flare gas

Abstract

A volume of natural gas including a volume of methane and a volume of other alkanes may be cleaned of the other alkanes using a steam reformer system to create synthesis gas. This synthesis gas may then be combined with hydrogen to produce methane and water.

1 - 20 . (canceled) 
     
     
         21 . A method for controlling a system to clean flare gas, the method comprising:
 receiving output measurements from the system, the output measurements including one or more of a CO 2  output and a methane output;   determining if one or more of the CO 2  output measurement and the methane output measurement are different than a CO 2  output set point and a methane output set point;   adjusting one or more of an inlet water flow to at least one steam reformer system and an inlet gas flow to the at least one steam reformer system in response to the CO 2  output set point and a methane output set point being different than the CO 2  output measurement and the methane output measurement;   wherein the at least one steam reformer system is configured to:
 receive a volume of natural gas from the inlet gas flow, the volume of natural gas including a volume of methane and a volume of other alkanes, 
 receive a volume of water from the inlet water flow, and 
 crack at least a portion of the volume of other alkanes from the volume of natural gas to generate synthesis gas from the volume of natural gas and the volume of water. 
   
     
     
         22 . The method according to  claim 21  further combining the synthesis gas with hydrogen to form methane. 
     
     
         23 . The method according to  claim 21 , wherein the output measurements further include a pressure output. 
     
     
         24 . The method according to  claim 21 , wherein the CO 2  output measurement is higher than the CO 2  output set point and the methane output measurement is lower than the methane output set point. 
     
     
         25 . The method according to  claim 24 , wherein the adjusting the one or more of the inlet water flow to at least one steam reformer system and the inlet gas flow to the at least one steam reformer system in response to the CO 2  output set point and the methane output set point being different than the CO 2  output measurement and the methane output measurement includes decreasing the inlet water flow. 
     
     
         26 . The method according to  claim 25 , further comprising decreasing the inlet gas flow in response to determining that a methane output from the system does not increase. 
     
     
         27 . The method according to  claim 21 , wherein the CO 2  output measurement is higher than the CO 2  output set point and the methane output measurement is higher than the methane output set point. 
     
     
         28 . The method according to  claim 27 , wherein the adjusting the one or more of the inlet water flow to at least one steam reformer system and the inlet gas flow to the at least one steam reformer system in response to the CO 2  output set point and the methane output set point being different than the CO 2  output measurement and the methane output measurement includes decreasing the inlet water flow. 
     
     
         29 . The method according to  claim 21 , wherein the CO 2  output measurement is lower than the CO 2  output set point and the methane output measurement is lower than the methane output set point. 
     
     
         30 . The method according to  claim 29 , wherein the adjusting the one or more of the inlet water flow to at least one steam reformer system and the inlet gas flow to the at least one steam reformer system in response to the CO 2  output set point and the methane output set point being different than the CO 2  output measurement and the methane output measurement includes decreasing the inlet gas flow. 
     
     
         31 . The method according to  claim 30 , further comprising increasing both the inlet gas flow and the inlet water flow in response to determining that a methane output from the system does not increase. 
     
     
         32 . A system for converting an input gas stream containing methane gas and other hydrocarbons into a methane-rich stream, comprising:
 a steam reformer reactor configured to receive input water and the input gas stream to produce a synthesis gas therefrom by (a) converting at least a portion of the other hydrocarbons of the input gas stream with the input water to the synthesis gas, and (b) allowing at least a portion of the methane gas from the input gas stream to pass through the steam reformer system unconverted, wherein the synthesis gas includes carbon oxide gas and hydrogen gas; and   a methanation reactor in fluid communication with the steam reformer reactor to receive the synthesis gas and the unconverted methane gas to produce the methane-rich stream by (a) converting at least a portion of the carbon oxide gas and at least a portion of the hydrogen gas in the synthesis gas to additional methane gas, and (b) combining the unconverted methane gas and the additional methane gas,   whereby the methane-rich stream has a greater methane concentration than the input gas stream.   
     
     
         33 . The system according to  claim 32 , further comprising a hydrogen generator in fluid communication with the methanation reactor, wherein hydrogen is supplied by the hydrogen generator to the methanation reactor in response to determining that mass balancing needs adjustment in the methanation reactor. 
     
     
         34 . The system according to  claim 33 , wherein the hydrogen generator comprises:
 another steam reformer reactor configured to receive the input water and the input gas stream to produce another synthesis gas therefrom by (a) cracking at least a portion of the other hydrocarbons, and (b) cracking at least a substantial portion of the methane gas of the input gas stream with the input water to the another synthesis gas with a lesser portion of the input water, wherein the another synthesis gas includes carbon oxide gas and hydrogen gas; and   a hydrogen purifier in fluid communication with the another steam reformer reactor to separate the hydrogen gas in the another synthesis gas from the carbon oxide gas allowing a partial pressure of the hydrogen gas to pass through the hydrogen purifier to the methanation reactor as required.   
     
     
         35 . The system according to  claim 33 , wherein the hydrogen generator comprises a hydrogen supply in fluid communication with the methanation reactor that allows supplied hydrogen gas to flow to the methanation reactor as required. 
     
     
         36 . The system according to  claim 34 , further comprising the hydrogen purifier in fluid communication with a burner system of at least one of the steam reformer reactor and the methanation reactor, wherein a portion of the synthesis gas fuels the burner system. 
     
     
         37 . The system according to  claim 32 , wherein the methanation reactor is configured to combine the hydrogen gas with the carbon oxides from the synthesis gas to form the additional methane gas and residual water. 
     
     
         38 . The system according to  claim 37 , further comprising a water removal system in fluid communication with the methanation reactor to remove at least a portion of the residual water from the methane-rich stream. 
     
     
         39 . The system according to  claim 38 , wherein the water removal system is in fluid communication with an inlet water source to receive the residual water for replenishing the input water. 
     
     
         40 . A system for converting an input gas stream containing methane gas and other hydrocarbons, comprising:
 a steam reformer reactor configured to receive water and the input gas stream to produce a synthesis gas therefrom by (a) converting at least a portion of the other hydrocarbons of the input gas stream with the water to the synthesis gas with a lesser portion of the water, and other gases, and (b) allowing at least a portion of the methane gas from the input gas stream to pass through the steam reformer system unconverted;   wherein the other gases in the output stream includes carbon oxide gas and hydrogen gas,   a methanation reactor configured to receive the synthesis gas and to produce a methane-rich stream therefrom having a greater methane concentration than the input stream;   wherein the methanation reactor is configured to convert at least a portion of the carbon oxide gas and at least a portion of the hydrogen gas in the synthesis gas to additional methane gas to produce a gas output composed of the methane gas and the additional methane gas.