NGL recovery from natural gas using a mixed refrigerant
First Claim
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1. A process for recovering natural gas liquids (NGL) from a hydrocarbon-containing feed gas stream, said process comprising:
- (a) cooling and at least partially condensing a hydrocarbon-containing feed gas stream to thereby provide a cooled feed gas stream, wherein at least a portion of said cooling is carried out via indirect heat exchange with a mixed refrigerant stream in a first heat exchanger of a closed-loop mixed refrigerant refrigeration cycle;
(b) separating said cooled feed gas stream into a first vapor stream and a first liquid stream in a vapor-liquid separator;
(c) splitting said first vapor stream into a first vapor portion and a second vapor portion;
(d) cooling at least a portion of said first vapor portion in said first heat exchanger to thereby provide a cooled first vapor stream, wherein at least a portion of said cooling is carried out via indirect heat exchange with said mixed refrigerant stream used to perform said cooling of step (a);
(e) flashing said cooled first vapor stream to thereby provide a first flashed stream;
(f) flashing said second vapor portion to thereby provide a second flashed stream;
(g) flashing the entire first liquid stream to provide a two-phase fluid stream having a vapor fraction of at least 0.10;
(h) introducing said first flashed stream, the entire two-phase fluid stream, and said second flashed stream into a distillation column via respective first, second, and third fluid inlets of said distillation column, wherein said first fluid inlet is located at a higher separation stage than said second and said third fluid inlets, and wherein said third fluid inlet is located at the same separation stage or at a lower separation stage than said second fluid inlet; and
(i) recovering an overhead residue gas stream and a liquid bottoms product stream from said distillation column, wherein said recovering step includes operating said distillation column in a C2 recovery mode or a C2 rejection mode,wherein, when said distillation column is operated in said C2 recovery mode, said liquid bottoms product stream comprises at least 90 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger and said overhead residue gas stream comprises less than 10 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger, andwherein, when said distillation column is operated in a C2 rejection mode, said liquid bottoms product stream comprises less than 30 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger and said overhead residue gas stream comprises at least 70 percent of the total moles of C2 components in said hydrocarbon containing feed gas stream introduced into said first heat exchanger,wherein prior to step (a), said mixed refrigerant stream is compressed, cooled, and expanded to thereby generate refrigeration, wherein at least a portion of said refrigeration is used to accomplish at least a portion of said cooling of step (a) and at least a portion of said cooling of step (d).
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Abstract
An NGL recovery facility for separating ethane and heavier (C2 ) components from a hydrocarbon-containing feed gas stream that utilizes a single, closed-loop mixed refrigerant cycle. The vapor and liquid portions of the feed gas stream are isenthalpically flashed and the resulting expanded streams are introduced into the NGL recovery column. Optionally, a second vapor stream can be flashed and then introduced into the recovery column at the same or lower separation stage than the flashed liquid stream. As a result, the NGL recovery facility can optimize C2 recovery with compression costs.
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Citations
18 Claims
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1. A process for recovering natural gas liquids (NGL) from a hydrocarbon-containing feed gas stream, said process comprising:
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(a) cooling and at least partially condensing a hydrocarbon-containing feed gas stream to thereby provide a cooled feed gas stream, wherein at least a portion of said cooling is carried out via indirect heat exchange with a mixed refrigerant stream in a first heat exchanger of a closed-loop mixed refrigerant refrigeration cycle; (b) separating said cooled feed gas stream into a first vapor stream and a first liquid stream in a vapor-liquid separator; (c) splitting said first vapor stream into a first vapor portion and a second vapor portion; (d) cooling at least a portion of said first vapor portion in said first heat exchanger to thereby provide a cooled first vapor stream, wherein at least a portion of said cooling is carried out via indirect heat exchange with said mixed refrigerant stream used to perform said cooling of step (a); (e) flashing said cooled first vapor stream to thereby provide a first flashed stream; (f) flashing said second vapor portion to thereby provide a second flashed stream; (g) flashing the entire first liquid stream to provide a two-phase fluid stream having a vapor fraction of at least 0.10; (h) introducing said first flashed stream, the entire two-phase fluid stream, and said second flashed stream into a distillation column via respective first, second, and third fluid inlets of said distillation column, wherein said first fluid inlet is located at a higher separation stage than said second and said third fluid inlets, and wherein said third fluid inlet is located at the same separation stage or at a lower separation stage than said second fluid inlet; and (i) recovering an overhead residue gas stream and a liquid bottoms product stream from said distillation column, wherein said recovering step includes operating said distillation column in a C2 recovery mode or a C2 rejection mode, wherein, when said distillation column is operated in said C2 recovery mode, said liquid bottoms product stream comprises at least 90 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger and said overhead residue gas stream comprises less than 10 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger, and wherein, when said distillation column is operated in a C2 rejection mode, said liquid bottoms product stream comprises less than 30 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger and said overhead residue gas stream comprises at least 70 percent of the total moles of C2 components in said hydrocarbon containing feed gas stream introduced into said first heat exchanger, wherein prior to step (a), said mixed refrigerant stream is compressed, cooled, and expanded to thereby generate refrigeration, wherein at least a portion of said refrigeration is used to accomplish at least a portion of said cooling of step (a) and at least a portion of said cooling of step (d). - View Dependent Claims (2, 3, 4, 5, 6, 13, 16)
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7. A process for recovering natural gas liquids (NGL) from a hydrocarbon-containing feed gas stream, said process comprising:
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(a) cooling a hydrocarbon-containing feed gas stream in a first heat exchanger via indirect heat exchange with a mixed refrigerant stream to thereby provide a cooled feed gas stream and a warmed refrigerant stream; (b) separating said cooled feed gas stream into a first vapor stream and a first liquid stream in a vapor-liquid separator; (c) splitting said first vapor stream into a first vapor portion and a second vapor portion; (d) cooling said first vapor portion to thereby provide a cooled vapor portion, wherein at least a portion of said cooling is carried out in said first heat exchanger via indirect heat exchange with said mixed refrigerant stream used to perform said cooling of step (a); (e) flashing said cooled vapor portion to thereby provide a first flashed stream; (f) flashing said second vapor portion to thereby provide a second flashed stream; (g) introducing said first and said second flashed streams into a distillation column at respective first and second fluid inlets; (h) flashing the entire first liquid stream to thereby provide a third flashed stream and introducing the entire third flashed stream into said distillation column via a third fluid inlet, wherein said third flashed stream is a two-phase stream having a vapor fraction of at least 0.10; and (i) recovering an NGL-enriched liquid product stream and an overhead residue gas stream from said distillation column, wherein said recovering includes operating said distillation column in a C2 recovery mode or a C2 rejection mode, wherein said second fluid inlet is and said third fluid inlet are located at lower separation stages than said first fluid inlet, wherein said second fluid inlet is located at the same separation stage as or at a lower separation stage than said third fluid inlet, wherein, when said distillation column is operated in said C2 recovery mode, said liquid product stream comprises at least 90 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger and said overhead residue gas stream comprises less than 10 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger, and wherein, when said distillation column is operated in a C2 rejection mode, said liquid product stream comprises less than 30 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first heat exchanger and said overhead residue gas stream comprises at least 70 percent of the total moles of C2 components in said hydrocarbon containing feed gas stream introduced into said first heat exchanger. - View Dependent Claims (8, 9, 10, 14, 17)
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11. A facility for recovering natural gas liquids (NGL) from a hydrocarbon-containing feed gas stream using a single closed-loop mixed refrigeration cycle, said facility comprising:
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a primary heat exchanger having a first cooling pass disposed therein, wherein said first cooling pass is operable to cool said hydrocarbon-containing feed gas stream; a vapor-liquid separator fluidly coupled to said first cooling pass for receiving the cooled feed gas stream, said vapor-liquid separator comprising a first vapor outlet for discharging a first vapor stream, and a first liquid outlet for discharging a first liquid stream; a vapor splitter defining a single vapor inlet and two vapor outlets for splitting said first vapor stream into a first vapor portion and a second vapor portion, wherein said single vapor inlet is fluidly coupled to said vapor outlet of said vapor-liquid separator; a second cooling pass disposed within said primary heat exchanger and fluidly coupled to one of said vapor outlets of said vapor splitter, wherein said second cooling pass is configured for cooling at least a portion of said first vapor portion; a first expansion device fluidly coupled to said second cooling pass for flashing at least a portion of the cooled first vapor portion to provide a first flashed stream; a second expansion device fluidly coupled to said first liquid outlet of said vapor-liquid separator for flashing the entire first liquid stream to provide a second flashed stream comprising two phases and having a vapor fraction of at least 0.10; a third expansion device for flashing the second vapor portion to provide a third flashed stream, wherein the other of said vapor outlets of said splitter is fluidly coupled to said third expansion device; a distillation column comprising a first fluid inlet for receiving said first flashed stream from said first expansion device, a second fluid inlet for receiving the entire second flashed stream from said second expansion device, a third fluid inlet for receiving said third flashed stream from said third expansion device, an upper vapor outlet for discharging an overhead residue gas stream, and a lower liquid outlet for discharging a liquid product stream, wherein said distillation column is configured to operate in a C2 recovery mode or a C2 rejection mode, wherein said first fluid inlet of said distillation column is positioned at a higher separation stage than said second fluid inlet and said third fluid inlet of said distillation column, wherein and said third fluid inlet is positioned at the same separation stage or at a lower separation stage than said second fluid inlet; and a single closed-loop mixed refrigeration cycle, said cycle comprising— a refrigerant compressor defining a suction inlet for receiving a mixed refrigerant stream and a discharge outlet for discharging a stream of compressed mixed refrigerant; a first refrigerant cooling pass disposed within said primary heat exchanger, wherein said first refrigerant cooling pass is fluidly coupled to said discharge outlet of said refrigerant compressor and is configured to subcool the compressed mixed refrigerant stream; a refrigerant expansion device fluidly coupled to said first refrigerant cooling pass for expanding the subcooled mixed refrigerant stream and generating refrigeration; and a first refrigerant warming pass disposed within said primary heat exchanger, wherein said first refrigerant warming pass fluidly coupled to said refrigerant expansion device, wherein said first refrigerant warming pass is configured to cool the feed gas stream in said first cooling pass and the vapor stream in said second cooling pass, wherein said first refrigerant warming pass is fluidly coupled to said suction inlet of said refrigerant compressor, wherein, when said distillation column is operated in said C2 recovery mode, said liquid product stream comprises at least 90 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first cooling pass of said primary heat exchanger and said overhead residue gas stream comprises less than 10 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first cooling pass of said primary heat exchanger, and wherein, when said distillation column is operated in a C2 rejection mode, said liquid product stream comprises less than 30 percent of the total moles of C2 components in said hydrocarbon-containing feed gas stream introduced into said first cooling pass of said primary heat exchanger and said overhead residue gas stream comprises at least 70 percent of the total moles of C2 components in said hydrocarbon containing feed gas stream introduced into said first cooling pass of said primary heat exchanger. - View Dependent Claims (12, 15, 18)
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Specification