Apparatus and methods for capturing vent gas in natural gas systems

Abstract

A natural gas system includes a pneumatic controller configured to discharge vent gas, an expansion vessel configured to discharge an expanded pilot gas, wherein the expansion vessel includes an internal volume configured to expand the vent gas discharged from the pneumatic controller whereby the expanded pilot gas discharged from the outlet port falls within a predefined discharge pressure range, a vent gas flowpath extending from the pneumatic controller to the expansion vessel, a burner assembly coupled to the expansion vessel and configured to ignite the expanded pilot gas discharged by the expansion vessel, and a pilot gas flowpath extending from the expansion vessel to the burner assembly.

What is claimed is: 
     
         1 . A natural gas system, comprising:
 one or more pneumatic controllers, wherein each pneumatic controller is configured to discharge a vent gas in response to operation of the one or more pneumatic controllers;   an expansion vessel comprising a one or more inlet ports and an outlet port configured to discharge an expanded pilot gas, wherein the expansion vessel comprises an internal volume configured to expand the vent gas discharged from the one or more pneumatic controllers whereby the expanded pilot gas discharged from the outlet port falls within a predefined discharge pressure range;   a one or more vent gas flowpaths extending from the one or more pneumatic controllers to the one or more inlet ports of the expansion vessel, wherein the one or more vent gas flowpaths are configured to transport vent gas discharged from the one or more pneumatic controllers to the inlet ports of the expansion vessel;   a burner assembly coupled to the expansion vessel and configured to ignite the expanded pilot gas discharged by the outlet port of the expansion vessel; and   a pilot gas flowpath extending from the outlet port of the expansion vessel to the burner assembly, wherein the pilot gas flowpath is configured to transport the expanded pilot gas from the expansion vessel to the burner assembly.   
     
     
         2 . The natural gas system of  claim 1 , wherein the discharge pressure range is based on an operational pressure range of the burner assembly. 
     
     
         3 . The natural gas system of  claim 1 , wherein the internal volume of the expansion vessel is equal to or greater than 250 cubic inches. 
     
     
         4 . The natural gas system of  claim 1 , wherein the internal volume of the expansion vessel is equal to or greater than 275 cubic inches. 
     
     
         5 . The natural gas system of  claim 1 , wherein at least one of the one or more pneumatic controllers comprises a pneumatically controlled valve. 
     
     
         6 . The natural gas system of  claim 1 , wherein the internal volume of the expansion vessel is configured to maintain a pressure differential between the expanded pilot gas discharged from the outlet port and the vent gas received by the one or more inlet ports that is equal to or greater than  5  pounds per square inch (PSI). 
     
     
         7 . The natural gas system of  claim 1 , further comprising a separator comprising a separator vessel, at least one of the one or more the pneumatic controllers, and the burner assembly that is configured to heat an internal volume of the separator vessel. 
     
     
         8 . The natural gas system of  claim 1 , further comprising an inlet pilot gas flowpath extending from a pilot gas source to a pilot inlet port of the one or more inlet ports of the expansion vessel, wherein pilot inlet port is configured to receive an inlet pilot gas stream transportable along the inlet pilot gas flowpath, and wherein the pressure of the inlet pilot gas stream received by the pilot inlet port falls within the discharge pressure range. 
     
     
         9 . A method for capturing vent gas produced by a natural gas system, the method comprising:
 (a) discharging a vent gas from a one or more pneumatic controllers;   (b) flowing the discharged vent gas along a one or more vent gas flowpaths that extends from the one or more pneumatic controllers to a one or more inlet ports of an expansion vessel;   (c) expanding the vent gas within an internal volume of the expansion vessel to depressurize the vent gas within the internal volume;   (d) discharging the vent gas as an expanded pilot gas from an outlet port of the expansion vessel whereby the expanded pilot gas falls within a predefined discharge pressure range;   (e) flowing the expanded pilot gas along an expanded pilot gas flowpath extending from the outlet port of the expansion vessel to a burner assembly; and   (f) igniting the expanded pilot gas by the burner assembly.   
     
     
         10 . The method of  claim 9 , wherein the pressure of the expanded pilot gas flowing along the expanded pilot gas flowpath is less than ten pounds per square inch gauge (PSIG). 
     
     
         11 . The method of  claim 10 , wherein the pressure of the vent gas flowing along the one or more vent gas flowpaths is greater than ten PSIG. 
     
     
         12 . The method of  claim 9 , wherein at least one of the one or more pneumatic controllers comprises a pneumatically controlled valve and (a) comprises discharging at least a portion of the vent gas in response to operating the pneumatically controlled valve. 
     
     
         13 . The method of  claim 9 , wherein the burner assembly comprises a pilot burner assembly of a separator of the natural gas system. 
     
     
         14 . The method of  claim 13 , further comprising:
 (g) flowing an inlet pilot gas stream along an inlet pilot gas flowpath extending from a pilot gas source to a pilot inlet port of the one or more inlet ports of the expansion vessel; and   (h) forming within the internal volume of the expansion vessel the expanded pilot gas from the inlet pilot gas received by the pilot inlet port of the expansion vessel and the vent gas received by the one or more inlet ports of the expansion vessel.   
     
     
         15 . A natural gas system, comprising:
 a separator comprising:
 a separator vessel; 
 a one or more pneumatic controllers, wherein each pneumatic controller is configured to discharge a vent gas in response to operation of the one or more pneumatic controllers; and 
 a burner assembly configured to heat an internal volume of the separator vessel; 
   an expansion vessel comprising a one or more inlet ports and an outlet port configured to discharge an expanded pilot gas, wherein the expansion vessel comprises an internal volume configured to expand the vent gas discharged from the one or more pneumatic controllers of the separator;   a one or more vent gas flowpaths extending from the one or more pneumatic controllers of the separator to the one or more inlet ports of the expansion vessel, wherein the one or more vent gas flowpaths are configured to transport vent gas discharged from the one or more pneumatic controllers to the inlet ports of the expansion vessel; and   an expanded pilot gas flowpath extending from the outlet port of the expansion vessel to the burner assembly of the separator, wherein the expanded pilot gas flowpath is configured to transport the expanded pilot gas from the expansion vessel to the burner assembly;   wherein the burner assembly of the separator is configured to ignite the expanded pilot gas discharged by the outlet port of the expansion vessel.   
     
     
         16 . The natural gas system of  claim 15 , wherein the internal volume of the expansion vessel is configured to expand the vent gas discharged from the one or more pneumatic controllers whereby the expanded pilot gas discharged from the outlet port falls within a predefined discharge pressure range. 
     
     
         17 . The natural gas system of  claim 15 , further comprising an inlet pilot gas flowpath extending from a pilot gas source to a pilot inlet port of the one or more inlet ports of the expansion vessel, wherein pilot inlet port is configured to receive an inlet pilot gas stream transportable along the inlet pilot gas flowpath. 
     
     
         18 . The natural gas system of  claim 17 , wherein:
 the internal volume of the expansion vessel is configured to expand the vent gas discharged from the one or more pneumatic controllers whereby the expanded pilot gas discharged from the outlet port falls within a predefined discharge pressure range; and   the pressure of the inlet pilot gas stream received by the pilot inlet port falls within the discharge pressure range.   
     
     
         19 . The natural gas system of  claim 18 , wherein the discharge pressure range is based on an operational pressure range of the burner assembly. 
     
     
         20 . The natural gas system of  claim 15 , wherein the internal volume of the expansion vessel is configured to maintain a pressure differential between the expanded pilot gas discharged from the outlet port and the vent gas received by the one or more inlet ports that is equal to or greater than  5  pounds per square inch (PSI).