Power Matched Mixed Refrigerant Compression Circuit

Abstract

A refrigerant compressor circuit for use in a liquefaction plant includes a first compression string driven by a first driver; a second compression string driven by a second driver, a pre-cooling refrigerant compression stage arranged in the first compression string to receive a stream of pre-cooling refrigerant at an inlet pressure and discharge the pre-cooling refrigerant at an outlet pressure, a first compression stage arranged in the first compression string to compress a mixed refrigerant gas from a first pressure to a second pressure, and, a second compression stage arranged in the second compression string to compress the mixed refrigerant gas from the second pressure to a third pressure. The pre-cooling refrigerant compression stage and the first compression stage of the circuit are co-axially mounted on a first shaft drivingly coupled to a first driver in the first compression string.

1 . A refrigerant compressor circuit for use in a liquefaction plant, the refrigerant compressor circuit comprising:
 a first compression string driven by a first driver;   a second compression string driven by a second driver;   a pre-cooling refrigerant compression stage arranged in the first compression string to receive a stream of pre-cooling refrigerant at an inlet pressure and discharge the pre-cooling refrigerant at an outlet pressure;   a first compression stage arranged in the first compression string to compress a mixed refrigerant gas from a first pressure to a second pressure; and,   a second compression stage arranged in the second compression string to compress the mixed refrigerant gas from the second pressure to a third pressure,   wherein the pre-cooling refrigerant compression stage and the first compression stage are co-axially mounted on a first shaft drivingly coupled to a first driver in the first compression string.   
     
     
         2 . A refrigerant compressor circuit according to  claim 1 , wherein a first intercooling heat exchanger is arranged between the first compression stage and the second compression stage for removing heat of compression from the mixed refrigerant gas. 
     
     
         3 . The refrigerant circuit of  claim 1 , wherein the mass flow of refrigerant to the second compression stage is directed to flow through a first segment and then a second segment within a single back-to-back compressor body. 
     
     
         4 . The refrigerant circuit of  claim 1 , wherein the first driver has more power than the second driver. 
     
     
         5 . The refrigerant circuit of  claim 1 , wherein the first compression stage is provided with a single compressor body comprising:
 a first suction inlet arranged to receive a first stream of refrigerant and direct the flow of the first stream of refrigerant into a first segment; and   a second suction inlet arranged to receive a second stream of refrigerant and direct the flow of the second stream of refrigerant into a second segment;   wherein the first and second segments are arranged end to end such that the first and second suction inlets are arranged at distal ends of the single compressor body, and the first and second streams are combined together as they flow out of a common outlet of the single compressor body.   
     
     
         6 . The refrigerant circuit of  claim 5 , further comprising a first distribution means for splitting the mass flow of refrigerant gas to the first compression stage into the first stream and second stream such that the first stream fed to the first suction inlet and the second stream fed to the section suction inlet are symmetrical. 
     
     
         7 . The refrigerant circuit of  claim 6 , wherein the first distribution means causes the mass flow of refrigerant to enter a branched tee such that a first half of the mass flow of refrigerant leaves the branched tee through one end of a straight run of pipe, while a second half of the mass flow of refrigerant leaves the branched tee in the opposite direction through the opposite end of the straight run of pipe. 
     
     
         8 . The refrigerant circuit of  claim 1 , wherein the pre-cooling refrigerant compression stage comprises a single pre-cooling refrigerant compressor body with a plurality of suction inlets arranged to receive evaporated pre-cooling refrigerant at a corresponding plurality of different pressures. 
     
     
         9 . The refrigerant circuit of  claim 1 , further comprising a third compression stage to compress the mixed refrigerant gas from the third pressure to a fourth pressure. 
     
     
         10 . The refrigerant circuit of  claim 9 , wherein the second compression stage and the third compression stage are co-axially mounted on a second shaft drivingly coupled to a second driver in the second compression string. 
     
     
         11 . The refrigerant circuit of  claim 9 , further comprising a second intercooling heat exchanger arranged between the second compression stage and the third compression stage, wherein the second intercooling heat exchanger is configured to remove heat of compression from the refrigerant. 
     
     
         12 . The refrigerant circuit of  claim 9 , wherein the second and third compression stages are combined within a single back to back compressor body. 
     
     
         13 . A plant for the production of a liquefied hydrocarbon product such as liquefied natural gas, the plant comprising:
 a main heat exchanger in which natural gas is liquefied by indirect heat exchange with an evaporating mixed refrigerant; and   a refrigerant circuit to compress the evaporated refrigerant for re-use in the main heat exchanger system, the refrigerant circuit comprising:   a first compression string driven by a first driver;   a second compression string driven by a second driver;   a pre-cooling refrigerant compression stage arranged in the first compression string to receive a stream of pre-cooling refrigerant at an inlet pressure and discharge the pre-cooling refrigerant at an outlet pressure;   a first compression stage arranged in the first compression string to compress a mixed refrigerant gas from a first pressure to a second pressure; and   a second compression stage arranged in the second compression string to compress the mixed refrigerant gas from the second pressure to a third pressure;   wherein the pre-cooling refrigerant compression stage and the first compression stage are co-axially mounted on a first shaft drivingly coupled to a first driver in the first compression string.   
     
     
         14 . The plant of  claim 13 , wherein a first intercooling heat exchanger is arranged between the first compression stage and the second compression stage to remove heat of compression from the mixed refrigerant gas. 
     
     
         15 . The plant of  claim 13 , wherein the mass flow of refrigerant to the second compression stage is directed to flow through a first segment and then a second segment within a single back-to-back compressor body. 
     
     
         16 . The plant of  claim 13 , wherein the first driver has more power than the second driver. 
     
     
         17 . The plant of  claim 13 , wherein the first compression stage is provided with a single compressor body comprising:
 a first suction inlet arranged to receive a first stream of refrigerant and direct the flow of the first stream of refrigerant into a first segment; and   a second suction inlet arranged to receive a second stream of refrigerant and direct the flow of the second stream of refrigerant into a second segment;   wherein the first and second segments are arranged end to end such that the first and second suction inlets are arranged at distal ends of the single compressor body, and the first and second streams are combined together as they flow out of a common outlet of the single compressor body.   
     
     
         18 . The plant of  claim 17 , further comprising a first distribution means for splitting the mass flow of refrigerant gas to the first compression stage into the first stream and second stream such that the first stream fed to the first suction inlet and the second stream fed to the section suction inlet are symmetrical. 
     
     
         19 . The plant of  claim 18 , wherein the first distribution means causes the mass flow of refrigerant to enter a branched tee such that a first half of the mass flow of refrigerant leaves the branched tee through one end of a straight run of pipe, while a second half of the mass flow of refrigerant leaves the branched tee in the opposite direction through the opposite end of the straight run of pipe. 
     
     
         20 . The plant of  claim 13 , wherein the pre-cooling refrigerant compression stage comprises a single pre-cooling refrigerant compressor body with a plurality of suction inlets arranged to receive evaporated pre-cooling refrigerant at a corresponding plurality of different pressures. 
     
     
         21 . The plant of  claim 13 , further comprising a third compression stage to compress the mixed refrigerant gas from the third pressure to a fourth pressure. 
     
     
         22 . The plant of  claim 21 , wherein the second compression stage and the third compression stage are co-axially mounted on a second shaft drivingly coupled to a second driver in the second compression string. 
     
     
         23 . The plant of  claim 21 , further comprising a second intercooling heat exchanger arranged between the second compression stage and the third compression stage to remove heat of compression from the refrigerant. 
     
     
         24 . The refrigerant circuit of  claim 21 , wherein the second and third compression stages are combined within a single back to back compressor body. 
     
     
         25 . A method for cooling, preferably liquefying, a hydrocarbon stream, wherein the hydrocarbon stream is cooled by indirect heat exchange with an evaporating refrigerant, and the evaporated refrigerant is cooled using a refrigerant compressor circuit comprising:
 a first compression string driven by a first driver;   a second compression string driven by a second driver;   a pre-cooling refrigerant compression stage arranged in the first compression string to receive a stream of pre-cooling refrigerant at an inlet pressure and discharge the pre-cooling refrigerant at an outlet pressure;   a first compression stage arranged in the first compression string to compress a mixed refrigerant gas from a first pressure to a second pressure; and   a second compression stage arranged in the second compression string to compress the mixed refrigerant gas from the second pressure to a third pressure;   wherein the pre-cooling refrigerant compression stage and the first compression stage are co-axially mounted on a first shaft drivingly coupled to a first driver in the first compression string.   
     
     
         26 . A method according to  claim 25 , wherein a first intercooling heat exchanger is arranged between the first compression stage and the second compression stage to remove heat of compression from the mixed refrigerant gas. 
     
     
         27 . A method according to  claim 25 , wherein the mass flow of refrigerant to the second compression stage is directed to flow through a first segment and then a second segment within a single back-to-back compressor body. 
     
     
         28 . A method according to  claim 25 , wherein the first driver has more power than the second driver. 
     
     
         29 . A method according to  claim 25 , wherein the first compression stage is provided with a single compressor body comprising:
 a first suction inlet arranged to receive a first stream of refrigerant and direct the flow of the first stream of refrigerant into a first segment; and   a second suction inlet arranged to receive a second stream of refrigerant and direct the flow of the second stream of refrigerant into a second segment;   wherein the first and second segments are arranged end to end such that the first and second suction inlets are arranged at distal ends of the single compressor body, and the first and second streams are combined together as they flow out of a common outlet of the single compressor body.   
     
     
         30 . A method according to  claim 29 , wherein the refrigerant compressor circuit further comprises a first distribution means for splitting the mass flow of refrigerant gas to the first compression stage into the first stream and second stream such that the first stream fed to the first suction inlet and the second stream fed to the section suction inlet are symmetrical. 
     
     
         31 . A method according to  claim 30 , wherein the first distribution means causes the mass flow of refrigerant to enter a branched tee such that a first half of the mass flow of refrigerant leaves the branched tee through one end of a straight run of pipe, while a second half of the mass flow of refrigerant leaves the branched tee in the opposite direction through the opposite end of the straight run of pipe. 
     
     
         32 . A method according to  claim 25 , wherein the pre-cooling refrigerant compression stage comprises a single pre-cooling refrigerant compressor body with a plurality of suction inlets arranged to receive evaporated pre-cooling refrigerant at a corresponding plurality of different pressures. 
     
     
         33 . A method according to  claim 25 , wherein the refrigerant compressor circuit further comprises a third compression stage to compress the mixed refrigerant gas from the third pressure to a fourth pressure. 
     
     
         34 . A method according to  claim 33 , wherein the second compression stage and the third compression stage are co-axially mounted on a second shaft drivingly coupled to a second driver in the second compression string. 
     
     
         35 . A method according to  claim 33 , wherein the refrigerant compressor circuit further comprises a second intercooling heat exchanger arranged between the second compression stage and the third compression stage to remove heat of compression from the refrigerant. 
     
     
         36 . A method according to  claim 33 , wherein the second and third compression stages are combined within a single back to back compressor body.