Mixed Refrigerant Liquefaction System and Method with Pre-Cooling

Abstract

A system for cooling a gas includes a pre-cool heat exchanger and a liquefaction heat exchanger. The pre-cool heat exchanger uses a pre-cool refrigerant to pre-cool a feed gas stream prior to the stream being directed to a liquefaction heat exchanger. The liquefaction heat exchanger uses a mixed refrigerant to further cool the pre-cooled gas. The pre-cool heat exchanger also pre-cools the liquefaction mixed refrigerant used by the liquefaction heat exchanger.

What is claimed is: 
     
         1 . A system for cooling a gas with a pre-cool refrigerant and a mixed refrigerant comprising:
 a. a pre-cool heat exchanger having a feed gas inlet adapted to receive a feed gas stream and a feed gas outlet, a pre-cool refrigerant inlet and a pre-cool refrigerant outlet and a liquefaction mixed refrigerant inlet and a liquefaction mixed refrigerant outlet, said pre-cool heat exchanger configured to use the pre-cool refrigerant to cool feed gas passing through the pre-cool heat exchanger between the feed gas inlet and outlet and to cool liquefaction mixed refrigerant passing through the pre-cool heat exchanger between the liquefaction mixed refrigerant inlet and outlet;   b. a pre-cool compressor system including:
 i) a pre-cool compressor having an inlet in fluid communication with the pre-cool refrigerant outlet of the pre-cool heat exchanger; 
 ii) a pre-cool condenser having an inlet in fluid communication with an outlet of the pre-cool compressor, said pre-cool condenser also having outlet in fluid communication with the pre-cool refrigerant inlet of the pre-cool heat exchanger: 
   c. a liquefaction heat exchanger including a liquefying passage in fluid communication with the feed gas outlet of the pre-cool heat exchanger, a primary refrigeration passage, a high pressure vapor cooling passage and a cold separator vapor cooling passage, where the cold separator vapor cooling passage has an outlet in fluid communication with the primary refrigeration passage;   d. a mixed refrigerant compression system including:
 i) a mixed refrigerant compressor having an inlet in fluid communication with an outlet of the primary refrigeration passage; 
 ii) a mixed refrigerant cooler having an inlet in fluid communication with an outlet of the mixed refrigerant compressor, said mixed refrigerant cooler having an outlet in fluid communication with the liquefaction mixed refrigerant inlet of the pre-cool heat exchanger, 
 iii) a high pressure accumulator having an inlet in fluid communication with the liquefaction mixed refrigerant outlet of the pre-cool heat exchanger and a vapor outlet in fluid communication with an inlet of the high pressure vapor cooling passage of the liquefaction heat exchanger; 
   e. a cold vapor separator having an inlet in fluid communication with an outlet of the high pressure vapor cooling passage of the liquefaction heat exchanger, a vapor outlet in fluid communication with an inlet of the cold separator vapor cooling passage of the liquefaction heat exchanger and a liquid outlet in communication with the primary refrigeration passage of the liquefaction heat exchanger.   
     
     
         2 . The system of  claim 1  wherein the pre-cool heat exchanger includes a warm pre-cool heat exchanger and a cold pre-cool heat exchanger. 
     
     
         3 . The system of  claim 2  wherein each of the warm pre-cool heat exchanger and the cold pre-cool heat exchanger includes a shell that receives the pre-cool refrigerant and at least one of the warm pre-cool heat exchanger and the cold pre-cool heat exchanger includes a feed gas core that receives the feed gas. 
     
     
         4 . The system of  claim 2  wherein each of the warm pre-cool heat exchanger and the cold pre-cool heat exchanger includes a liquefaction mixed refrigerant core configured to cool liquefaction mixed refrigerant passing through the pre-cool heat exchanger between the liquefaction mixed refrigerant inlet and outlet. 
     
     
         5 . The system of  claim 4  wherein a single liquefaction mixed refrigerant core extends within both of the shells of the warm and cold pre-cool heat exchangers and is configured to cool liquefaction mixed refrigerant passing through the pre-cool heat exchanger between the liquefaction mixed refrigerant inlet and outlet. 
     
     
         6 . The system of  claim 5  wherein an internal head extends between interior spaces of the shells of the warm and cold pre-cool heat exchangers and the single liquefaction mixed refrigerant core extends through the internal head. 
     
     
         7 . The system of  claim 1  wherein the mixed refrigerant compression system further includes a mixed refrigerant second compressor or compression stage having an inlet in fluid communication with the outlet of the mixed refrigerant cooler, a second mixed refrigerant cooler having an inlet if fluid communication with an outlet of the mixed refrigerant second compressor or compression stage, said second cooler having an outlet in fluid communication with the liquefaction mixed refrigerant inlet of the pre-cool heat exchanger. 
     
     
         8 . The system of  claim 7  wherein the pre-cool heat exchanger includes an interstage mixed refrigerant inlet and an interstage mixed refrigerant outlet, and wherein the mixed refrigerant compressor has an outlet in fluid communication with the interstage mixed refrigerant inlet of the pre-cool heat exchanger and the interstage mixed refrigerant outlet of the pre-cool heat exchanger is in fluid communication with an interstage accumulator having a vapor outlet in fluid communication with the inlet of the second compressor or second compression stage and a liquid outlet in fluid communication with the primary refrigeration passage of the liquefaction heat exchanger. 
     
     
         9 . The system of  claim 1  wherein the high pressure accumulator includes a liquid outlet and the liquefaction heat exchanger further comprises a high pressure liquid cooling passage having an inlet in fluid communication with the liquid outlet of the high pressure accumulator and an outlet in fluid communication with the primary refrigeration passage of the liquefaction heat exchanger. 
     
     
         10 . The system of  claim 1  wherein the pre-cool refrigerant is propane, butane, ammonia or a chlorofluorocarbon. 
     
     
         11 . The system of  claim 1  wherein the pre-cool refrigerant is a mixed refrigerant. 
     
     
         12 . The system of  claim 11  wherein the pre-cool refrigerant heat exchanger is a plate and fin heat exchanger. 
     
     
         13 . A method for cooling a feed gas stream comprising the steps of:
 a. pre-cooling the feed gas stream in a pre-cool heat exchanger using a first refrigerant to form a pre-cooled feed gas stream;   b. further cooling the pre-cooled feed gas stream by:
 i) cooling a high pressure second refrigerant stream in the pre-cool heat exchanger to form a cooled high pressure second refrigerant stream 
 ii) separating the cooled high pressure second refrigerant stream to form a high pressure vapor stream and a high pressure liquid stream; 
 iii) cooling the high pressure vapor stream in a liquefaction heat exchanger, to form a mixed phase stream; 
 iv) separating the mixed phase stream with a cold vapor separator to form a cold separator vapor stream and a cold separator liquid stream; 
 v) condensing the cold separator vapor stream in the liquefaction heat exchanger using the second refrigerant and flashing, to form a cold temperature refrigerant stream; 
 vi) directing the cold temperature refrigerant stream to the liquefaction heat exchanger; 
 vii) subcooling the high pressure liquid stream to form a subcooled high pressure liquid stream and combining with the cold temperature refrigerant stream in the liquefaction heat exchanger; 
 viii) subcooling the cold separator liquid stream to form a subcooled cold separator liquid stream and combining with the cold temperature refrigerant stream in the liquefaction heat exchanger; and 
 ix) thermally contacting the pre-cooled gas stream in the liquefaction heat exchanger with the cold temperature refrigerant stream. 
   
     
     
         14 . The method of  claim 13  wherein the high pressure liquid stream and the cold separator liquid stream are subcooled in the liquefaction heat exchanger. 
     
     
         15 . The method of  claim 13  wherein step b. further comprises the steps of cooling a low pressure mixed refrigerant stream in the pre-cool heat exchanger, separating the cooled low pressure mixed refrigerant stream to form a low pressure mixed refrigerant vapor stream and a low pressure mixed refrigerant liquid stream, compressing the low pressure mixed refrigerant vapor stream to form a high pressure mixed refrigerant steam and then cooling the high pressure mixed refrigerant stream to form the cooled high pressure mixed refrigerant stream and directing the low pressure mixed refrigerant liquid stream to the liquefaction heat exchanger. 
     
     
         16 . The method of  claim 15  wherein the high pressure mixed refrigerant stream is cooled in the pre-cool heat exchanger to form the cooled high pressure mixed refrigerant stream. 
     
     
         17 . The method of  claim 15  wherein the high pressure mixed refrigerant stream is cooled in both the pre-cool heat exchanger and the liquefaction heat exchanger to form the cooled high pressure mixed refrigerant stream. 
     
     
         18 . The method of  claim 13  wherein the pre-cool refrigerant is propane, butane, ammonia or a chlorofluorocarbon. 
     
     
         19 . The method of  claim 13  wherein the pre-cool refrigerant is a mixed refrigerant. 
     
     
         20 . The method of  claim 13  wherein step a. includes a first pre-cooling stage using a warm pre-cool heat exchanger and a second pre-cooling stage using a cold pre-cool heat exchanger. 
     
     
         21 . A system for cooling a feed gas with a mixed refrigerant comprising:
 a. a pre-cool heat exchanger having a pre-cool refrigerant inlet configured to receive a stream of pre-cool refrigerant and a pre-cool refrigerant outlet and a liquefaction mixed refrigerant inlet and a liquefaction mixed refrigerant outlet, said pre-cool heat exchanger configured to use the pre-cool refrigerant to cool liquefaction mixed refrigerant passing through the pre-cool heat exchanger between the liquefaction mixed refrigerant inlet and outlet;   b. a liquefaction heat exchanger including a liquefying passage configured to receive a stream of the feed gas, a primary refrigeration passage, a high pressure vapor cooling passage and a cold separator vapor cooling passage, where the cold separator vapor cooling passage has an outlet in fluid communication with the primary refrigeration passage;   c. a mixed refrigerant compression system including:   i) a mixed refrigerant compressor having an inlet in fluid communication with an outlet of the primary refrigeration passage;   ii) a mixed refrigerant cooler having an inlet in fluid communication with an outlet of the mixed refrigerant compressor, said mixed refrigerant cooler having an outlet in fluid communication with the liquefaction mixed refrigerant inlet of the pre-cool heat exchanger,   iii) a high pressure accumulator having an inlet in fluid communication with the liquefaction mixed refrigerant outlet of the pre-cool heat exchanger and a vapor outlet in fluid communication with an inlet of the high pressure vapor cooling passage of the liquefaction heat exchanger;   d. a cold vapor separator having an inlet in fluid communication with an outlet of the high pressure vapor cooling passage of the liquefaction heat exchanger, a vapor outlet in fluid communication with an inlet of the cold separator vapor cooling passage of the liquefaction heat exchanger and a liquid outlet in communication with the primary refrigeration passage of the liquefaction heat exchanger.   
     
     
         22 . The system of  claim 21  wherein the pre-cool heat exchanger also includes a feed gas inlet adapted to receive a feed gas stream and a feed gas outlet and said pre-cool heat exchanger is configured to use the pre-cool refrigerant to cool feed gas passing through the pre- cool heat exchanger between the feed gas inlet and the feed gas outlet. 
     
     
         23 . The system of  claim 21  wherein the pre-cool heat exchanger includes a plurality of heat exchangers connected in series or parallel. 
     
     
         24 . The system of  claim 21  wherein the pre-cool refrigerant is selected from the group consisting of propane, butane, ammonia, water, water glycol mix, lithium bromide solution, liquid fluorinated hydrocarbons and liquid hydrocarbons. 
     
     
         25 . The system of  claim 21  further comprising a pump configured to pump a stream of pre-cool refrigerant to the pre-cool refrigerant inlet of the pre-cool heat exchanger. 
     
     
         26 . The system of  claim 21  further comprising a pre-cool refrigerant system selected from the group consisting of a mechanical chiller, an adsorption chiller, a thermoelectric chiller and a thermoacoustic refrigerator wherein the pre-cool refrigerant system is configured to cool the pre-cool refrigerant. 
     
     
         27 . A method for cooling a feed gas stream comprising the steps of:
 a. directing the feed gas stream into a liquefaction heat exchanger;   b. cooling a high pressure mixed refrigerant stream in a pre-cool heat exchanger to form a cooled high pressure mixed refrigerant stream;   c. cooling the feed gas stream in the liquefaction heat exchanger by:
 i) separating the cooled high pressure mixed refrigerant stream to form a high pressure vapor stream and a high pressure liquid stream; 
 ii) cooling the high pressure vapor stream in the liquefaction heat exchanger to form a mixed phase stream; 
 iii) separating the mixed phase stream with a cold vapor separator to form a cold separator vapor stream and a cold separator liquid stream; 
 iv) condensing the cold separator vapor stream in the liquefaction heat exchanger and flashing, to form a cold temperature refrigerant stream; 
 v) directing the cold temperature refrigerant stream to the liquefaction heat exchanger; 
 vi) subcooling the high pressure liquid stream in the liquefaction heat exchanger to form a subcooled high pressure liquid stream and combining with the cold temperature refrigerant stream in the liquefaction heat exchanger; 
 vii) subcooling the cold separator liquid stream to form a subcooled cold separator liquid stream and combining with the cold temperature refrigerant stream in the liquefaction heat exchanger; and 
 viii) thermally contacting the gas stream in the liquefaction heat exchanger with the cold temperature refrigerant stream. 
   
     
     
         28 . The method of  claim 27  further comprising the step of pre-cooling the feed gas stream in the pre-cool heat exchanger prior to step a. 
     
     
         29 . The method of  claim 27  wherein step b. is performed using a pre-cool refrigerant that is cooled using a pre-cool refrigerant system selected from the group consisting of a mechanical chiller, an adsorption chiller, a thermoelectric chiller and a thermoacoustic refrigerator. 
     
     
         30 . The method of  claim 29  wherein the pre-cool refrigerant is cooled to a temperature colder than a temperature that can be achieved by either air cooling or evaporative cooling.