CN102435044B - Cryogenic separating system for preparing liquefied natural gas with oven gas - Google Patents
Cryogenic separating system for preparing liquefied natural gas with oven gas Download PDFInfo
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- CN102435044B CN102435044B CN201110412617.0A CN201110412617A CN102435044B CN 102435044 B CN102435044 B CN 102435044B CN 201110412617 A CN201110412617 A CN 201110412617A CN 102435044 B CN102435044 B CN 102435044B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0233—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 1 carbon atom or more
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
- F25J3/0223—H2/CO mixtures, i.e. synthesis gas; Water gas or shifted synthesis gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0252—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of hydrogen
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0257—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of nitrogen
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/74—Refluxing the column with at least a part of the partially condensed overhead gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2215/00—Processes characterised by the type or other details of the product stream
- F25J2215/04—Recovery of liquid products
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2270/00—Refrigeration techniques used
- F25J2270/14—External refrigeration with work-producing gas expansion loop
- F25J2270/16—External refrigeration with work-producing gas expansion loop with mutliple gas expansion loops of the same refrigerant
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2270/00—Refrigeration techniques used
- F25J2270/42—Quasi-closed internal or closed external nitrogen refrigeration cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
- F25J2290/34—Details about subcooling of liquids
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- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
The invention discloses a cryogenic separating system for preparing liquefied natural gas with oven gas. The cryogenic separating system comprises a methane-hydrogen rectifying tower, a methane-nitrogen rectifying tower, a feed gas cooler, a nitrogen subcooler, a tower top condenser I of the methane-hydrogen rectifying tower, a tower top condenser II of the methane-hydrogen rectifying tower and a tower bottom reboiler of the methane-hydrogen rectifying tower constituting a cryogenic separating pipeline system, a hydrogen-rich recovering pipeline system and a nitrogen-rich pipeline system for natural gas, and further comprises a two-stage nitrogen expanding refrigerating circulation loop for supplying cold energy to the feed gas cooler and the nitrogen subcooler. The cryogenic separating system for preparing liquefied natural gas with oven gas has the advantages of low cost, small investment, stable system, easiness for operating and high natural gas recovering rate.
Description
Technical field
The present invention relates to the system of oven gas preparing liquefied natural gas, especially a kind of cryogenic separation system of oven gas preparing liquefied natural gas.
Background technology
In oven gas, contain the components such as carbon monoxide, methane, hydrogen, nitrogen, belong to middle calorific value gas.Main component after methanation is processed in oven gas is methane, hydrogen, nitrogen and a small amount of ethane, the cost of producing natural gas with oven gas has larger competitiveness than coal preparing natural gas, both met national energy policy, can fully, rationally utilize industrial discharge gas resource, reduce greenhouse gas emission, can bring huge economic benefit for enterprise again simultaneously.In prior art, cryogenic separation natural gas from oven gas, is to adopt azeotrope kind of refrigeration cycle, and azeotrope need to increase storage, the transportation system of each cryogen, and cryogen compressor cost is higher.
Summary of the invention
The object of the invention is to: a kind of cryogenic separation system of oven gas preparing liquefied natural gas is provided, and cost is low, small investment, system stability, the rate of recovery simple to operate, natural gas are high.
For achieving the above object, the present invention can take following technical proposals:
The cryogenic separation system of a kind of oven gas preparing liquefied natural gas of the present invention, comprise methane-hydrogen rectifying column, methane-nitrogen rectifying column, feed gas chiller, nitrogen subcooler, the overhead condenser one of methane-hydrogen rectifying column, the overhead condenser two of methane-nitrogen rectifying column, and the tower bottom reboiler of methane-nitrogen rectifying column, the unstripped gas obtaining through methanation processing and pretreatment, successively through the first cooling line of described feed gas chiller, the cooling line of tower bottom reboiler, the second cooling line of feed gas chiller, methane-hydrogen rectifying column entrance, methane-hydrogen rectifying tower bottom outlet, pressure-reducing valve one, methane-nitrogen rectifying column entrance, the heating pipe line of tower bottom reboiler, the 3rd cooling line of feed gas chiller, pressure-reducing valve three and natural gas storage tank, form the cryogenic separation pipe-line system of natural gas, wherein the heating pipe line of tower bottom reboiler outlet is also communicated with ascending air entrance at the bottom of the tower of methane-nitrogen rectifying column, the tower top outlet of methane-hydrogen rectifying column is communicated with the cooling line of overhead condenser one, the first re-heat pipeline of nitrogen subcooler, the first re-heat pipeline and the hydrogen rich gas recovery tube of feed gas chiller successively, form hydrogen rich gas reclaim line system, wherein the outlet of the cooling line of overhead condenser one is also communicated with the overhead reflux liquid entrance of methane-hydrogen rectifying column, the tower top outlet of methane-nitrogen rectifying column is communicated with the cooling line of overhead condenser two, the second re-heat pipeline of nitrogen subcooler, the second re-heat pipeline and the rich nitrogen tube of feed gas chiller successively, form rich nitrogen pipeline system, wherein the outlet of the cooling line of overhead condenser two is also communicated with the overhead reflux liquid entrance of methane-nitrogen rectifying column, also being included as feed gas chiller and nitrogen subcooler provides the double-stage nitrogen swell refrigeration closed circuit of cold.
Described double-stage nitrogen swell refrigeration closed circuit, comprises circulating nitrogen gas compressor, cold junction booster expansion turbine, hot junction booster expansion turbine and J/T valve; Low-pressure nitrogen is divided into two strands through circulating nitrogen gas compressor boost and after being cooled to room temperature, one enters the pressurized end supercharging of hot junction booster expansion turbine, then the 4th cooling line that enters unstripped gas heat exchanger is cooling, from the most of nitrogen of unstripped gas heat exchanger middle part extraction, enter the expanding end of described cold junction booster expansion turbine, from expanding end, export the 4th re-heat pipeline re-heat that enters unstripped gas heat exchanger, for feed gas chiller provides cold; From unstripped gas heat exchanger middle part, extract fraction nitrogen out and enter that the cooling line of nitrogen subcooler is cooling, liquefaction, through J/T valve decompression refrigeration, as the low-temperature receiver of the overhead condenser one of methane-hydrogen rectifying column and the overhead condenser two of methane-nitrogen rectifying column, described overhead condenser one and overhead condenser two are respectively methane-hydrogen rectifying column, methane-nitrogen rectifying column provides required phegma, after liquid nitrogen vaporization successively through the 3rd re-heat pipeline of nitrogen subcooler and the 5th re-heat pipeline re-heat of feed gas chiller, for nitrogen subcooler and feed gas chiller provide cold; Another strand enters the pressurized end supercharging of cold junction booster expansion turbine, then the 5th cooling line that enters unstripped gas heat exchanger is cooling, then enter the expanding end of cold junction booster expansion turbine, from expanding end, export the 3rd re-heat pipeline re-heat that enters unstripped gas heat exchanger, for feed gas chiller provides cold; From the nitrogen of the 3rd, the 4th and the 5th re-heat pipeline of feed gas chiller, import the entrance of circulating nitrogen gas compressor, enter kind of refrigeration cycle next time.
In described double-stage nitrogen swell refrigeration closed circuit, be provided with nitrogen and supplement mouth, described nitrogen supplements mouth and is connected with circulating nitrogen gas suction port of compressor pipeline.
Compared with prior art the invention has the beneficial effects as follows: because the present invention utilizes the low pressure nitrogen that backflows, rich nitrogen, hydrogen rich gas provides cold to provide the cooling unstripped gas of cold and supercharging nitrogen to feed gas chiller, utilize the low pressure nitrogen that backflows, rich nitrogen, hydrogen rich gas provides cold cooling liquid nitrogen to nitrogen subcooler, reduced the energy consumption of whole system, again owing to having adopted the mode of the circulation of double-stage nitrogen swell refrigeration and the combination of liquid nitrogen throttling refrigeration, the equipment investment of separating natural gas is reduced greatly, and further reduced the energy consumption of whole system, system stability is good, simple to operate, the rate of recovery of natural gas is high.
Accompanying drawing explanation
Fig. 1 is the structural representation of the cryogenic separation system of oven gas preparing liquefied natural gas of the present invention.
The specific embodiment
As shown in Figure 1, the cryogenic separation system of a kind of oven gas preparing liquefied natural gas of the present invention, comprise methane-hydrogen rectifying column T-101, methane-nitrogen rectifying column T-102, feed gas chiller E-201, nitrogen subcooler E-202, overhead condenser one E-104 of methane-hydrogen rectifying column T-101, overhead condenser two E-105 of methane-nitrogen rectifying column T-102, the tower bottom reboiler E-106 of methane-nitrogen rectifying column T-102, circulating nitrogen gas compressor C-101, hot junction booster expansion turbine ET-101, cold junction booster expansion turbine ET-102, J/T valve V-102, pressure-reducing valve one V-101 and pressure-reducing valve three V-103,
The unstripped gas obtaining through methanation processing and pretreatment, successively through the first cooling line LY-1 of described feed gas chiller E-201, the cooling line of tower bottom reboiler E-106, the second cooling line LY-2 of feed gas chiller E-201, methane-hydrogen rectifying column T-101 entrance, methane-hydrogen rectifying column T-101 tower bottom outlet, pressure-reducing valve one V-101, methane-nitrogen rectifying column T-102 entrance, the heating pipe line of tower bottom reboiler E-106, the 3rd cooling line LY-3 of feed gas chiller E-201, pressure-reducing valve three V-103 and natural gas storage tank, form the cryogenic separation pipe-line system of natural gas, wherein the heating pipe line of tower bottom reboiler E-106 outlet is also communicated with uprising gas entrance at the bottom of the tower of methane-nitrogen rectifying column T-102,
The tower top outlet of methane-hydrogen rectifying column T-101 is communicated with the cooling line of overhead condenser one E-104, the first re-heat pipeline FD-1 of nitrogen subcooler E-202, the first re-heat pipeline FY-1 and the hydrogen rich gas recovery tube of feed gas chiller E-201 successively, form hydrogen rich gas reclaim line system, wherein the outlet of the cooling line of overhead condenser one E-104 is also communicated with the overhead reflux liquid entrance of methane-hydrogen rectifying column T-101;
The tower top outlet of methane-nitrogen rectifying column T-102 is communicated with the cooling line of overhead condenser two E-105, the second re-heat pipeline FD-2 of nitrogen subcooler E-202, the second re-heat pipeline FY-2 and the rich nitrogen tube of feed gas chiller E-201 successively, form rich nitrogen pipeline system, wherein the outlet of the cooling line of overhead condenser two E-105 is also communicated with the overhead reflux liquid entrance of methane-nitrogen rectifying column T-102;
Also being included as feed gas chiller E-201 and nitrogen subcooler E-202 provides the double-stage nitrogen swell refrigeration closed circuit of cold.Described double-stage nitrogen swell refrigeration closed circuit, comprises circulating nitrogen gas compressor C-101, hot junction booster expansion turbine ET-101, cold junction booster expansion turbine ET-102 and J/T valve V-102, low-pressure nitrogen is divided into two strands through the C-101 supercharging of circulating nitrogen gas compressor and after being cooled to room temperature, one enters the pressurized end supercharging of hot junction booster expansion turbine ET-101, then the 4th cooling line LY-4 that enters unstripped gas heat exchanger E-201 is cooling, from the most of nitrogen of unstripped gas heat exchanger E-201 middle part extraction, enter the expanding end of described hot junction booster expansion turbine ET-101, from expanding end, export the 4th re-heat pipeline FY-4 re-heat that enters unstripped gas heat exchanger E-201, for feed gas chiller, E-201 provides cold, the cooling line LD-1 that enters nitrogen subcooler E-202 from unstripped gas heat exchanger E-201 middle part extraction fraction nitrogen is cooling, liquefaction, through J/T valve V-102 decompression refrigeration, as the low-temperature receiver of overhead condenser one E-104 of methane-hydrogen rectifying column T-101 and overhead condenser two E-105 of methane-nitrogen rectifying column T-102, described overhead condenser one E-104 and overhead condenser two E-105 are respectively methane-hydrogen rectifying column T-101, methane-nitrogen rectifying column T-102 provide required phegma, the 5th re-heat pipeline FY-5 re-heat through the 3rd re-heat pipeline FD-3 and the feed gas chiller E-201 of nitrogen subcooler E-202 successively after liquid nitrogen vaporization, for nitrogen subcooler E-202 and feed gas chiller E-201 provide cold, another strand enters the pressurized end supercharging of cold junction booster expansion turbine ET-102, then the 5th cooling line LY-5 that enters unstripped gas heat exchanger E-201 is cooling, then enter the expanding end of cold junction booster expansion turbine ET-102, from expanding end, export the 3rd re-heat pipeline FY-3 re-heat that enters unstripped gas heat exchanger E-201, for feed gas chiller, E-201 provides cold, from the 3rd, the 4th and the 5th re-heat pipeline FY-3 of feed gas chiller E-201,4 and 5 nitrogen, import the entrance of circulating nitrogen gas compressor C-101, enter kind of refrigeration cycle next time.
As preferably, in described double-stage nitrogen swell refrigeration closed circuit, be provided with nitrogen and supplement mouth, described nitrogen supplements mouth and is connected with the entrance pipe of circulating nitrogen gas compressor C-101.
Deep cooling separating method of the present invention is as follows:
Step 1: it is methane that oven gas obtains main component after methanation processing and pretreatment, hydrogen, the unstripped gas that the pressure of nitrogen and a small amount of ethane is 1.7～2.1Mpa, the the first cooling line LY-1 that described unstripped gas is imported to feed gas chiller E-201 is cooled to after-120～-126 ℃, from described feed gas chiller E-201 middle part, extract out, then import the thermal source of tower bottom reboiler E-106 as this tower bottom reboiler E-106, then the second cooling line LY-2 that imports feed gas chiller E-201 continues to be cooled to-140～-150 ℃, from the feed gas chiller E-201 unstripped gas containing a small amount of liquid out, import methane-hydrogen rectifying column T-101, after rectifying, obtain the tower bottom liquid product of tower top hydrogen-rich gas and-150～-160 ℃, the main component of this tower bottom liquid product is nitrogen, methane and hydrogen,
Step 2: by described tower top hydrogen-rich gas successively through the first re-heat pipeline FY-1 of the first re-heat pipeline FD-1, the feed gas chiller E-201 of the cooling line of overhead condenser one E-104, nitrogen subcooler E-202, for described nitrogen subcooler E-202 and feed gas chiller E-201 provide cold, re-heat is to returning to methanation reaction device after normal temperature or through the PSA high-purity hydrogen of purifying to obtain; Described tower bottom liquid product is imported after pressure-reducing valve one V-101 is decompressed to 0.3～0.42Mpa to methane-nitrogen rectifying column T-102, after rectifying, obtain methane production and the rich nitrogen of tower top at the bottom of tower; The rich nitrogen of described tower top provides cold through the second re-heat pipeline FD-2, feed gas chiller E-201 the second re-heat pipeline FY-2 of the cooling line of overhead condenser two E-105, nitrogen subcooler E-202 for nitrogen subcooler E-202 and feed gas chiller E-201 successively; At the bottom of described tower, methane production is crossed cold 6～8 ℃, pressure-reducing valve three V-103 through the 3rd cooling line LY-3 of the heating pipe line of tower bottom reboiler E-106, feed gas chiller E-201 successively and is decompressed to after required pressure, imports natural gas storage tank;
Described feed gas chiller E-201 and nitrogen subcooler E-202 adopt the circulation of double-stage nitrogen swell refrigeration: the low-pressure nitrogen that pressure is 0.28～0.36Mpa is divided into two strands through the C-101 supercharging of circulating nitrogen gas compressor and after being cooled to room temperature, one pressurized end that enters hot junction booster expansion turbine ET-101 is pressurized to 2.2～2.4Mpa, then the 4th cooling line LY-4 that enters unstripped gas heat exchanger E-201 is cooled to-25 ℃, from the most of nitrogen of unstripped gas heat exchanger E-201 middle part extraction, enter the expanding end of described hot junction booster expansion turbine ET-101, the pressure that exports out from expanding end is 0.3～0.4Mpa, temperature is the nitrogen of-165 ℃, enter i.e. the 4th re-heat pipeline FY-4 re-heat of low-pressure nitrogen passage of unstripped gas heat exchanger E-201, for feed gas chiller, E-201 provides cold, from unstripped gas heat exchanger E-201 middle part, extract out the cooling line LD-1 that fraction nitrogen enters nitrogen subcooler E-202 and liquefy, be cooled to-170～-180 ℃, through J/T valve V-102 decompression refrigeration, as the low-temperature receiver of overhead condenser one E-104 of methane-hydrogen rectifying column T-101 and overhead condenser two E-105 of methane-nitrogen rectifying column T-102, described overhead condenser one E-104 provides required phegma for methane-hydrogen rectifying column T-101, described overhead condenser two E-105 provide required phegma for methane-nitrogen rectifying column T-102, the main component of described phegma is nitrogen, methane and hydrogen, the 5th re-heat pipeline FY-5 re-heat through the 3rd re-heat pipeline FD-3 and the feed gas chiller E-201 of nitrogen subcooler E-202 successively after liquid nitrogen vaporization, for nitrogen subcooler E-202 and feed gas chiller E-201 provide cold, the pressurized end that another strand enters cold junction booster expansion turbine ET-102 is pressurized to 1.7～1.85Mpa, then the 5th cooling line LY-5 that enters unstripped gas heat exchanger E-201 is cooled to-110～-120 ℃, then enter the expanding end of ET-102, i.e. the 3rd re-heat pipeline FY-3 re-heat of low-pressure nitrogen passage that enters unstripped gas heat exchanger E-201 from expanding end outlet, for feed gas chiller, E-201 provides cold, from the 3rd, the 4th and the 5th re-heat pipeline FY-3 of feed gas chiller E-201,4 and 5 nitrogen, import the entrance of circulating nitrogen gas compressor C-101, enter kind of refrigeration cycle next time.
As preferably, in the nitrogen of described double-stage nitrogen swell refrigeration circulation, add 5%～15% methane gas, object is to optimize heat exchange, reduces energy consumption.
Use the obtainable liquefied natural gas purity approximately 92% of the present invention, ethane content approximately 7%, yield 99%; The yield of byproduct recycle hydrogen approximately 99%; Specific energy consumption is 0.65kw.h/Nm3 LNG.
The present invention is not limited to the above-mentioned specific embodiment, and any technical scheme being equal to mutually with the present invention, or the simple replacement that the present invention is carried out, all in protection scope of the present invention.
Claims (3)
1. the cryogenic separation system of an oven gas preparing liquefied natural gas, comprise methane-hydrogen rectifying column (T-101), methane-nitrogen rectifying column (T-102), unstripped gas heat exchanger (E-201), nitrogen subcooler (E-202), the overhead condenser one (E-104) of methane-hydrogen rectifying column (T-101), the overhead condenser two (E-105) of methane-nitrogen rectifying column (T-102), and the tower bottom reboiler (E-106) of methane-nitrogen rectifying column (T-102), the unstripped gas obtaining through methanation processing and pretreatment, successively through first cooling line (LY-1) of described unstripped gas heat exchanger (E-201), the cooling line of tower bottom reboiler (E-106), second cooling line (LY-2) of unstripped gas heat exchanger (E-201), methane-hydrogen rectifying column (T-101) entrance, methane-hydrogen rectifying column (T-101) tower bottom outlet, pressure-reducing valve one (V-101), methane-nitrogen rectifying column (T-102) entrance, the heating pipe line of tower bottom reboiler (E-106), the 3rd cooling line (LY-3) of unstripped gas heat exchanger (E-201), pressure-reducing valve three (V-103) and natural gas storage tank, form the cryogenic separation pipe-line system of natural gas, wherein the heating pipe line of tower bottom reboiler (E-106) outlet is also communicated with ascending air entrance at the bottom of the tower of methane-nitrogen rectifying column (T-102), the tower top outlet of methane-hydrogen rectifying column (T-101) is communicated with the cooling line of overhead condenser one (E-104), the first re-heat pipeline (FD-1) of nitrogen subcooler (E-202), the first re-heat pipeline (FY-1) and the hydrogen rich gas recovery tube of unstripped gas heat exchanger (E-201) successively, form hydrogen rich gas reclaim line system, wherein the outlet of the cooling line of overhead condenser one (E-104) is also communicated with the overhead reflux liquid entrance of methane-hydrogen rectifying column (T-101), the tower top outlet of methane-nitrogen rectifying column (T-102) is communicated with the cooling line of overhead condenser two (E-105), the second re-heat pipeline (FD-2) of nitrogen subcooler (E-202), the second re-heat pipeline (FY-2) and the rich nitrogen tube of unstripped gas heat exchanger (E-201) successively, form rich nitrogen pipeline system, wherein the outlet of the cooling line of overhead condenser two (E-105) is also communicated with the overhead reflux liquid entrance of methane-nitrogen rectifying column (T-102),
Also being included as unstripped gas heat exchanger (E-201) and nitrogen subcooler (E-202) provides the double-stage nitrogen swell refrigeration closed circuit of cold, described double-stage nitrogen swell refrigeration closed circuit, comprise circulating nitrogen gas compressor (C-101), hot junction booster expansion turbine (ET-101), cold junction booster expansion turbine (ET-102) and J/T valve (V-102), low-pressure nitrogen is divided into two strands through (C-101) supercharging of circulating nitrogen gas compressor and after being cooled to room temperature, one enters the pressurized end supercharging of hot junction booster expansion turbine (ET-101), then the 4th cooling line (LY-4) that enters unstripped gas heat exchanger (E-201) is cooling, from the most of nitrogen of unstripped gas heat exchanger (E-201) middle part extraction, enter the expanding end of described hot junction booster expansion turbine (ET-101), from expanding end, export the 4th re-heat pipeline (FY-4) re-heat that enters unstripped gas heat exchanger (E-201), for unstripped gas heat exchanger (E-201) provides cold, the cooling line (LD-1) that enters nitrogen subcooler (E-202) from unstripped gas heat exchanger (E-201) middle part extraction fraction nitrogen is cooling, liquefaction, through J/T valve (V-102) decompression refrigeration, as the low-temperature receiver of the overhead condenser one (E-104) of methane-hydrogen rectifying column (T-101) and the overhead condenser two (E-105) of methane-nitrogen rectifying column (T-102), described overhead condenser one (E-104) and overhead condenser two (E-105) are respectively methane-hydrogen rectifying column (T-101), methane-nitrogen rectifying column (T-102) provides required phegma, the 5th re-heat pipeline (FY-5) re-heat through the 3rd re-heat pipeline (FD-3) and the unstripped gas heat exchanger (E-201) of nitrogen subcooler (E-202) successively after liquid nitrogen vaporization, for nitrogen subcooler (E-202) and unstripped gas heat exchanger (E-201) provide cold, another burst of pressurized end supercharging that enters cold junction booster expansion turbine (ET-102), then the 5th cooling line (LY-5) that enters unstripped gas heat exchanger (E-201) is cooling, then enter the expanding end of cold junction booster expansion turbine (ET-102), from expanding end, export the 3rd re-heat pipeline (FY-3) re-heat that enters unstripped gas heat exchanger (E-201), for unstripped gas heat exchanger (E-201) provides cold, from the nitrogen of the 3rd, the 4th and the 5th re-heat pipeline (FY-3,4 and 5) of unstripped gas heat exchanger (E-201), import the entrance of circulating nitrogen gas compressor (C-101), enter kind of refrigeration cycle next time,
Concrete steps are as follows:
Step 1: it is methane that oven gas obtains main component after methanation processing and pretreatment, hydrogen, the unstripped gas that the pressure of nitrogen and a small amount of ethane is 1.7～2.1Mpa, the first cooling line (LY-1) that described unstripped gas is imported to unstripped gas heat exchanger (E-201) is cooled to after-120～-126 ℃, from described unstripped gas heat exchanger (E-201) middle part, extract out, then import the thermal source of tower bottom reboiler (E-106) as this tower bottom reboiler (E-106), then the second cooling line (LY-2) that imports unstripped gas heat exchanger (E-201) continues to be cooled to-140～-150 ℃, from unstripped gas heat exchanger (E-201) unstripped gas containing a small amount of liquid out, import methane-hydrogen rectifying column (T-101), after rectifying, obtain the tower bottom liquid product of tower top hydrogen-rich gas and-150～-160 ℃, the main component of this tower bottom liquid product is nitrogen, methane and hydrogen,
Step 2: by described tower top hydrogen-rich gas successively through the cooling line of overhead condenser one (E-104), the first re-heat pipeline (FD-1) of nitrogen subcooler (E-202), the first re-heat pipeline (FY-1) of unstripped gas heat exchanger (E-201), for described nitrogen subcooler (E-202) and unstripped gas heat exchanger (E-201) provide cold, re-heat is to returning to methanation reaction device after normal temperature or through the PSA high-purity hydrogen of purifying to obtain; Described tower bottom liquid product is imported after pressure-reducing valve one V-101 is decompressed to 0.3～0.42Mpa to methane-nitrogen rectifying column (T-102), after rectifying, obtain methane production and the rich nitrogen of tower top at the bottom of tower; The rich nitrogen of described tower top provides cold through the second re-heat pipeline (FD-2) of the cooling line of overhead condenser two (E-105), nitrogen subcooler (E-202), unstripped gas heat exchanger (E-201) the second re-heat pipeline (FY-2) for nitrogen subcooler (E-202) and unstripped gas heat exchanger (E-201) successively; At the bottom of described tower, methane production is decompressed to after required pressure through heating pipe line, cold 6～8 ℃ excessively of the 3rd cooling lines (LY-3) of unstripped gas heat exchanger (E-201), the pressure-reducing valve three (V-103) of tower bottom reboiler (E-106) successively, imports natural gas storage tank;
Described unstripped gas heat exchanger (E-201) and nitrogen subcooler (E-202) adopt the circulation of double-stage nitrogen swell refrigeration: the low-pressure nitrogen that pressure is 0.28～0.36Mpa is divided into two strands through (C-101) supercharging of circulating nitrogen gas compressor and after being cooled to room temperature, one pressurized end that enters hot junction booster expansion turbine (ET-101) is pressurized to 2.2～2.4Mpa, then the 4th cooling line (LY-4) that enters unstripped gas heat exchanger (E-201) is cooled to-25 ℃, from the most of nitrogen of unstripped gas heat exchanger (E-201) middle part extraction, enter the expanding end of described hot junction booster expansion turbine (ET-101), the pressure that exports out from expanding end is 0.3～0.4Mpa, temperature is the nitrogen of-165 ℃, enter i.e. the 4th re-heat pipeline (FY-4) re-heat of low-pressure nitrogen passage of unstripped gas heat exchanger (E-201), for unstripped gas heat exchanger (E-201) provides cold, from unstripped gas heat exchanger (E-201) middle part, extract out the cooling line (LD-1) that fraction nitrogen enters nitrogen subcooler (E-202) and liquefy, be cooled to-170～-180 ℃, through J/T valve (V-102) decompression refrigeration, as the low-temperature receiver of the overhead condenser one (E-104) of methane-hydrogen rectifying column (T-101) and the overhead condenser two (E-105) of methane-nitrogen rectifying column (T-102), described overhead condenser one (E-104) provides required phegma for methane-hydrogen rectifying column (T-101), described overhead condenser two (E-105) provides required phegma for methane-nitrogen rectifying column (T-102), the main component of described phegma is nitrogen, methane and hydrogen, the 5th re-heat pipeline (FY-5) re-heat through the 3rd re-heat pipeline (FD-3) and the unstripped gas heat exchanger (E-201) of nitrogen subcooler (E-202) successively after liquid nitrogen vaporization, for nitrogen subcooler (E-202) and unstripped gas heat exchanger (E-201) provide cold, the pressurized end that another strand enters cold junction booster expansion turbine (ET-102) is pressurized to 1.7～1.85Mpa, then the 5th cooling line (LY-5) that enters unstripped gas heat exchanger (E-201) is cooled to-110～-120 ℃, then enter the expanding end of (ET-102), from expanding end outlet, enter i.e. the 3rd re-heat pipeline (FY-3) re-heat of low-pressure nitrogen passage of unstripped gas heat exchanger (E-201), for unstripped gas heat exchanger (E-201) provides cold, from the nitrogen of the 3rd, the 4th and the 5th re-heat pipeline (FY-3,4 and 5) of unstripped gas heat exchanger (E-201), import the entrance of circulating nitrogen gas compressor (C-101), enter kind of refrigeration cycle next time.
2. the cryogenic separation system of a kind of oven gas preparing liquefied natural gas according to claim 1, is characterized in that: in the nitrogen of described double-stage nitrogen swell refrigeration circulation, add 5%～15% methane gas.
3. the cryogenic separation system of a kind of oven gas preparing liquefied natural gas according to claim 1, it is characterized in that: in described double-stage nitrogen swell refrigeration closed circuit, be provided with nitrogen and supplement mouth, described nitrogen supplements mouth and is connected with circulating nitrogen gas compressor (C-101) entrance pipe.
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