Fuel Gas Conditioner

Abstract

A system and method for conditioning fuel gas comprises a separator to receive rich gas and to separate NGLs from the rich gas to produce lean fuel gas. A first valve is coupled before the separator to receive the rich gas to expand the rich gas in a throttling or Joule-Thomson effect to reduce the pressure and temperature of the rich gas for the separator. A heat exchanger is coupled before the first valve to transfer heat from the rich gas to the lean fuel gas. The system can further comprise another separator to receive rich gas to separate water from the rich gas to preprocess the rich gas. The system can further comprise a temperature control loop utilizing a slip stream from the separator, a second expansion valve, and another heat exchanger.

What is claimed is: 
     
         1 . A fuel gas conditioner, comprising:
 a) an inlet configured to be coupled to a rich gas source at high-pressure and high-temperature;   b) a first separator coupled to the inlet and configured to receive high-pressure and high-temperature rich gas to separate liquid including water from the rich gas resulting in high-pressure and high-temperature pre-conditioned gas;   c) a first valve coupled to the first separator to receive the high-pressure and high-temperature pre-conditioned gas to expand the pre-conditioned gas in a Joule-Thomson effect to reduce the pressure and temperature of the pre-conditioned gas resulting in low-pressure and low-temperature pre-conditioned gas;   d) a second separator coupled to the first separator and the first valve, and configured to receive the low-pressure and low-temperature pre-conditioned gas and to further separate liquid including natural gas liquids (NGLs) from the low-pressure and low-temperature pre-conditioned gas to produce lean fuel gas;   e) a first heat exchanger coupled between the first and second separators, and coupled to the second separator, to transfer heat from the pre-conditioned gas to the lean fuel gas;   f) a second heat exchanger coupled between and to the first and second separators to transfer heat from the pre-conditioned gas to separated liquid from the first and second separators;   g) a second valve coupled to the first separator to receive the pre-conditioned gas to expand the pre-conditioned gas in a Joule-Thomson effect to reduce the pressure and temperature of the pre-conditioned gas and defining a slip stream; and   h) a third heat exchanger coupled between the first and second separators, and coupled to the slip stream, to transfer heat from the pre-conditioned gas to the slip stream, the second valve and the third heat exchanger defining a temperature control loop.   
     
     
         2 . The fuel gas conditioner in accordance with  claim 1 , further comprising:
 a) a mobile skid configured to be deliverable to a site requiring gas conditioning;   b) the inlet, the first separator, the second separator, the first valve, the first heat exchanger, the second heat exchanger, the second valve and the third heat exchanger being carried by the skid; and   c) a conditioned lean fuel gas outlet carried by the skid and coupled to the first heat exchanger and the second separator.   
     
     
         3 . The fuel gas conditioner in accordance with  claim 1 , further comprising:
 a) a third three-phase separator coupled to the first and second separators to receive the liquid, and configured to separate the liquid into residue gas, waste water and natural gas liquids (NGLs); and   b) a fourth heat exchanger coupled between the first and second separators, and coupled to the third three-phase separator, to transfer heat from the pre-conditioned gas to the residual gas.   
     
     
         4 . The fuel gas conditioner in accordance with  claim 3 , further comprising:
 a) a mobile skid configured to be deliverable to a site requiring gas conditioning;   b) the inlet, the first separator, the second separator, the first valve, the first heat exchanger, the second heat exchanger, the second valve, the third heat exchanger, the third three-phase separator, and the fourth heat exchanger being carried by the skid;   c) a waste water outlet carried by the skid and coupled to the third three-phase separator;   d) an NGL outlet carried by the skid and coupled to the third three-phase separator; and   e) a residue gas vent carried by the skid and coupled to the third three-phase separator.   
     
     
         5 . The fuel gas conditioner in accordance with  claim 1 , wherein the inlet is configured to be coupled to a rich gas source at high-pressure between 800-1200 psig and high temperature between 70-110° F. 
     
     
         6 . The fuel gas conditioner in accordance with  claim 1 , wherein the second separator is configured to operate at low-pressure between 50-150 psig and low-temperature between −50 to −90° F. 
     
     
         7 . The fuel gas conditioner in accordance with  claim 1 , further comprising:
 a) a temperature sensor associated with the second separator; and   b) a control actuator associated with the second valve and coupled to the temperature sensor to control the second valve base on temperature sensed by the temperature sensor.   
     
     
         8 . A fuel gas conditioner, comprising:
 a) a mobile skid configured to be deliverable to a site requiring gas conditioning;   b) an inlet carried by the skid and configured to be coupled to a rich gas source at high-pressure and high-temperature;   c) a first separator carried by the skid and coupled to the inlet and configured to receive high-pressure and high-temperature rich gas to separate liquid including water from the rich gas resulting in high-pressure and high-temperature pre-conditioned gas;   d) a first valve carried by the skid and coupled to the first separator to receive the high-pressure and high-temperature pre-conditioned gas to expand the pre-conditioned gas in a Joule-Thomson effect to reduce the pressure and temperature of the pre-conditioned gas resulting in low-pressure and low-temperature pre-conditioned gas;   e) a second separator carried by the skid and coupled to the first separator and the first valve, and configured to receive the low-pressure and low-temperature pre-conditioned gas and to further separate liquid including natural gas liquids (NGLs) from the low-pressure and low-temperature pre-conditioned gas to produce lean fuel gas;   f) a first heat exchanger carried by the skid and coupled between the first and second separators, and coupled to the second separator, to transfer heat from the pre-conditioned gas to the lean fuel gas;   g) a second heat exchanger carried by the skid and coupled between the first and second separators to transfer heat from the pre-conditioned gas to separated liquid from the separators;   h) a second valve carried by the skid and coupled to the first separator to receive the high-pressure and high-temperature pre-conditioned rich gas to expand the rich gas in a Joule-Thomson effect to reduce the pressure and temperature of the rich gas and defining a slip stream; and   i) a third heat exchanger carried by the skid and coupled between the first and second separators, and coupled to the slip stream, to transfer heat from the rich gas to the slip stream, the second valve and the third heat exchanger defining a temperature control loop.   
     
     
         9 . The fuel gas conditioner in accordance with  claim 8 , further comprising:
 a) a third three-phase separator carried by the skid and coupled to the first and second separators to receive the liquid, and configured to separate the liquid into residue gas, waste water and natural gas liquids (NGLs); and   b) a fourth heat exchanger carried by the skid and coupled between the first and second separators, and coupled to the third three-phase separator, to transfer heat from the rich gas to the residual gas.   
     
     
         10 . The fuel gas conditioner in accordance with  claim 8 , wherein the inlet is configured to be coupled to the rich gas source at high-pressure between 800-1200 psig and high temperature between 70-110° F. 
     
     
         11 . The fuel gas conditioner in accordance with  claim 8 , wherein the second separator is configured to operate at low-pressure between 50-150 psig and low-temperature between −50 to −90° F. 
     
     
         12 . The fuel gas conditioner in accordance with  claim 8 , further comprising:
 a) a temperature sensor associated with the second separator; and   b) a control actuator associated with the second valve and coupled to the temperature sensor to control the second valve base on temperature sensed by the temperature sensor.   
     
     
         13 . A method for conditioning fuel gas, the method comprising:
 a) separating liquid from a rich gas in a first separator at a high pressure and a high temperature resulting in high-pressure and high-temperature pre-conditioned gas containing high-pressure and high-temperature hydrocarbon liquids;   b) cooling the pre-conditioned gas in a series of heat exchangers, including first, second and third heat exchangers;   c) expanding the high-pressure and high-temperature pre-conditioned gas in a Joule-Thomson effect to reduce the pressure and temperature of the pre-conditioned gas by passing the pre-conditioned gas through a first valve resulting in low-temperature and low-pressure pre-conditioned gas;   d) separating liquids from the pre-conditioned gas in a second separator resulting in a lean fuel gas;   e) passing the lean fuel gas through the first heat exchanger to cool the pre-conditioned gas;   f) passing the liquids through the second heat exchanger to cool the pre-conditioned gas;   g) taking a slip stream of the high-pressure and high-temperature pre-conditioned gas after the first separator; and   h) passing the slip stream through the third heat exchanger to cool the pre-conditioned gas.   
     
     
         14 . The method in accordance with  claim 13 , further comprising:
 a) cooling the pre-conditioned gas in a fourth heat exchanger;   b) separating the liquid from the first and second separators in a third three-phase separator into residue gas, waste water and natural gas liquids (NGLs); and   c) passing the residue gas through the fourth heat exchanger to cool the pre-conditioned rich gas.   
     
     
         15 . The method in accordance with  claim 13 , further comprising:
 coupling the first separator to a rich gas source at a high pressure between 800-1200 psig and a high temperature between 70-110° F.   
     
     
         16 . The method in accordance with  claim 13 , further comprising:
 separating hydrocarbon liquids from the pre-conditioned gas in the second separator at a low-pressure between 50-150 psig and a low-temperature between −50 to −90° F.   
     
     
         17 . The method in accordance with  claim 13 , further comprising:
 sensing a temperature of the second separator; and   controlling the second valve based on the temperature sensed at the second separator.