Systems and processes for stationary and mobile natural gas liquefaction

Abstract

The disclosure describes processes which include cooling a natural gas product stream to a cryogenic liquid storage temperature by way of refrigeration streams which include a primary refrigeration stream, a secondary refrigeration stream, and a tertiary refrigeration stream in a refrigeration system. After leaving the refrigeration system, the pressure of each refrigeration stream is increased, and upon reaching a sufficient pressure, the refrigeration streams are recycled to flow back into the refrigeration system as a recycle stream. The disclosure further describes systems capable of performing the processes. The processes and systems can include one or more sensors and one or more controls capable of adjusting a flow rate, flow volume, and/or flow ratio among one or more gas streams to maximize cooling efficiency based on monitoring from the one or more sensors. Mobile natural gas liquefaction systems are also described.

1 . A process, comprising:
 providing a raw natural feed gas to a gas cleanup system and removing one or more impurities from the raw natural feed gas to produce an incoming gas stream;   delivering the incoming gas stream to one of multiple gas inlet options of a gas liquefaction system, depending on pressure of the incoming gas stream, and by way of the gas liquefaction system:
 cooling the incoming gas stream to a cryogenic liquid storage temperature by way of a refrigeration system comprising primary, secondary, and tertiary refrigeration streams; 
 increasing the refrigeration streams to a desired pressure (P recycle ); and 
 recycling the refrigeration streams through the refrigeration system until a desired cryogenic liquid storage temperature is reached. 
   
     
     
         2 . The process of  claim 1 , wherein the gas liquefaction system is disposed on one or more first mobile unit, the gas cleanup system is disposed on one or more second mobile unit, and/or electrical power equipment for operating the gas liquefaction system and/or the gas cleanup system is disposed on one or more third mobile unit. 
     
     
         3 . The process of  claim 1 , further comprising splitting the incoming gas stream to form a first stream which provides the primary refrigeration stream and a second stream which provides a product stream, which product stream provides the secondary refrigeration stream and the tertiary refrigeration stream. 
     
     
         4 . The process of  claim 3 , further comprising monitoring one or more of flow rate, flow volume, gas temperature, gas composition or gas pressure, and adjusting a flow rate, flow volume, and/or flow ratio within and/or among one or more of the incoming gas stream, the first stream, the second stream, the product stream, the primary refrigeration stream, the secondary refrigeration stream, and/or the tertiary refrigeration stream based on the monitoring. 
     
     
         5 . The process of  claim 3 , further comprising directing the first stream through a heat exchanger and then a turbo-expander to form the primary refrigeration stream. 
     
     
         6 . The process of  claim 1 , wherein the refrigeration system comprises one or more heat exchanger or system. 
     
     
         7 . The process of  claim 6 , further comprising, after leaving the refrigeration system, mixing one or more of the refrigeration streams with incoming gas, before increasing the pressure of the refrigeration streams to P recycle  pressure, or mixing the incoming gas optionally at the P recycle  pressure. 
     
     
         8 . The process of  claim 7 , wherein increasing the pressure of the refrigeration streams is performed by:
 a 3-stage compressor with three compressors sharing the same shaft, or   three standalone compressors, or   a first compressor comprising a first compression stage on a first shaft, and a second compressor comprising second and third compression stages sharing a second shaft; or   a first compressor comprising first and second compression stages sharing a first shaft, and a second compressor comprising a third compression stage on a second shaft.   
     
     
         9 . The process of  claim 1 , further comprising expanding, decreasing the pressure, and/or further cooling the incoming gas stream by way of one or more Joule-Thompson valves to form a liquefied natural gas (LNG) product, the secondary refrigeration stream, and the tertiary refrigeration stream. 
     
     
         10 . The process of  claim 9 , further comprising after passing through the Joule-Thompson valve(s), providing:
 i) a first stream that is an LNG to storage stream;   ii) a second stream that mixes with boil off gas from storage to form the tertiary refrigeration stream; and   iii) a third stream that results in the secondary refrigeration stream or is split to result in the secondary refrigeration stream and a stream that contributes to the tertiary refrigeration stream.   
     
     
         11 . The process of  claim 10 , wherein the third stream is split and:
 i) a portion of the split stream, a vapor phase, mixes with the second stream and is subsequently compressed; and   ii) a portion of the split stream, a liquid phase, forms the secondary refrigeration stream and is pumped pressure higher than P recycle  and compression is not required before recycling back into the product stream.   
     
     
         12 . The process of  claim 1 , wherein once the desired cryogenic liquid storage temperature is reached, delivering resultant liquefied natural gas product to storage. 
     
     
         13 . A mobile natural gas liquefaction system comprising:
 one or more first mobile unit housing gas liquefaction equipment;   one or more second mobile unit housing gas cleanup equipment; and   one or more third mobile unit housing electrical power equipment;   wherein the second mobile unit is capable of a fluid communication with the first mobile unit and/or third mobile unit which allows transfer of a gas supply thereto and wherein the first mobile unit is capable of a fluid communication with the third mobile unit which allows transfer of fuel gas from the first mobile unit to the third mobile unit; and   wherein the first mobile unit comprises an output for delivering liquefied natural gas to cryogenic liquid storage.   
     
     
         14 . The mobile natural gas liquefaction system of  claim 13 , wherein the gas liquefaction equipment is configured to and capable of performing the process of  claim 1 . 
     
     
         15 . The mobile natural gas liquefaction system of  claim 13 , wherein the gas liquefaction equipment is capable of liquefaction of gas supplied from the second mobile unit. 
     
     
         16 . The mobile natural gas liquefaction system of  claim 13 , wherein:
 the electrical power supply is capable of powering the gas liquefaction equipment and/or the gas cleanup equipment; and   the electrical power equipment of the third mobile unit comprises an electrical generator capable of using as fuel any one or more of i) gas supplied from the second mobile unit, ii) feed gas, iii) gas from the first mobile unit; and/or any other as fuel gas.   
     
     
         17 . The mobile natural gas liquefaction system of  claim 13 , wherein the first mobile unit housing the gas liquefaction equipment comprises a 3-stage compressor with three compressors sharing the same shaft, or three standalone compressors, or a first compressor comprising a first compression stage on a first shaft and a second compressor comprising second and third compression stages sharing a second shaft, or a first compressor comprising first and second compression stages sharing a first shaft, and a second compressor comprising a third compression stage on a second shaft. 
     
     
         18 . The mobile natural gas liquefaction system of  claim 13 , wherein the second mobile unit comprises:
 an input designed to receive feed gas to supply the gas cleanup equipment; and   one or more output capable of supplying gas to the first mobile unit and/or fuel gas to the third mobile unit.   
     
     
         19 . The mobile natural gas liquefaction system of  claim 18 , wherein the gas cleanup equipment is designed to remove one or more of the following from the feed gas: water, heavy hydrocarbons, BTEX, H 2 S, Hg, Mercaptans and/or carbon dioxide. 
     
     
         20 . The mobile natural gas liquefaction system of  claim 13 , wherein the first mobile unit, the second mobile unit, and the third mobile unit are each independently chosen from trailers, skids, sea containers, a portable or transportable housing or container, an ISO container, housings or containers with or without wheels, open or closed housings or containers without or with walls, a flatbed, housings or containers that are portable or transportable in whole or part and/or temporarily or permanently fixed at a location for use and/or portable or transportable before, during and/or after use. 
     
     
         21 . The mobile natural gas liquefaction system of  claim 13 , wherein the first mobile unit housing the gas liquefaction equipment is configured for delivering resultant liquefied natural gas product to storage. 
     
     
         22 . A mobile natural gas liquefaction system comprising:
 a mobile unit;   gas liquefaction equipment disposed on the mobile unit;   wherein the gas liquefaction equipment comprises a turbo expander/compressor.   
     
     
         23 . The system of  claim 22 , wherein:
 the turbo expander/compressor is disposed on a common shaft and is disposed in a manner to produce a primary refrigeration stream;   such that the turbo expander is capable of rapidly letting down gas pressure, while the turbo compressor is driven by the turbo expander and is capable of increasing gas pressure.   
     
     
         24 . The system of  claim 23 , wherein:
 the gas liquefaction equipment further comprises a heat exchanger disposed in a manner to receive the primary refrigeration stream from the turbo expander and deliver the primary refrigeration stream to the turbo compressor.   
     
     
         25 . The system of  claim 22 , wherein:
 the gas liquefaction system utilizes methane (CH4) as the refrigeration gas.