CN116202020B - Integrated processing system and method for natural gas ethane recovery and LNG vaporization - Google Patents
Integrated processing system and method for natural gas ethane recovery and LNG vaporization Download PDFInfo
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- CN116202020B CN116202020B CN202310320917.9A CN202310320917A CN116202020B CN 116202020 B CN116202020 B CN 116202020B CN 202310320917 A CN202310320917 A CN 202310320917A CN 116202020 B CN116202020 B CN 116202020B
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 70
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 238000009834 vaporization Methods 0.000 title claims abstract description 36
- 230000008016 vaporization Effects 0.000 title claims abstract description 36
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000011084 recovery Methods 0.000 title claims abstract description 27
- 239000003345 natural gas Substances 0.000 title claims abstract description 23
- 238000012545 processing Methods 0.000 title claims description 10
- 239000007789 gas Substances 0.000 claims abstract description 127
- 238000001816 cooling Methods 0.000 claims abstract description 54
- 238000004781 supercooling Methods 0.000 claims abstract description 51
- 239000002994 raw material Substances 0.000 claims abstract description 45
- 239000007791 liquid phase Substances 0.000 claims abstract description 38
- 230000008569 process Effects 0.000 claims abstract description 18
- 238000010992 reflux Methods 0.000 claims abstract description 18
- 239000012071 phase Substances 0.000 claims abstract description 14
- 238000000926 separation method Methods 0.000 claims description 14
- 230000005540 biological transmission Effects 0.000 claims description 11
- 239000007788 liquid Substances 0.000 claims description 11
- 230000006835 compression Effects 0.000 claims description 7
- 238000007906 compression Methods 0.000 claims description 7
- 238000003303 reheating Methods 0.000 claims description 5
- 238000003672 processing method Methods 0.000 claims description 2
- 238000005057 refrigeration Methods 0.000 description 9
- 230000006872 improvement Effects 0.000 description 7
- 238000004064 recycling Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004134 energy conservation Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C9/00—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure
- F17C9/02—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure with change of state, e.g. vaporisation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
- F17C2227/03—Heat exchange with the fluid
- F17C2227/0337—Heat exchange with the fluid by cooling
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2265/00—Effects achieved by gas storage or gas handling
- F17C2265/03—Treating the boil-off
- F17C2265/032—Treating the boil-off by recovery
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
The invention discloses an integrated treatment system and method for natural gas ethane recovery and LNG vaporization, comprising the following steps: dividing the raw material gas into two parts, and respectively entering a main cooling box and a pre-cooling box for pre-cooling; one path of raw material gas after being precooled by the main cooling box is mixed with the raw material gas after being precooled by the precooling cooling box and then enters a low-temperature separator to separate gas phase and liquid phase; another path of raw material gas after being precooled by the main cooling box enters the supercooling cooling box for supercooling; part of the externally-conveyed dry gas flows back, and enters a supercooling cold box for supercooling after being precooled by a main cold box; separating the gas phase, the liquid phase, the supercooled raw material gas and the reflux dry gas in a demethanizer, obtaining lean gas (mainly methane gas) at the top of the demethanizer, and obtaining C 2 + condensate at the bottom of the demethanizer; LNG sequentially passes through the cold box for heat exchange and temperature rise, and the main cold box for heat exchange and vaporization, so that NG output is obtained. The invention recovers a large amount of high-grade cold energy released in the LNG vaporization process for natural gas ethane recovery.
Description
Technical Field
The invention relates to the technical field of natural gas cryogenic processing, in particular to an integrated processing system and method for natural gas ethane recovery and LNG vaporization.
Background
Currently, natural gas ethane recovery processes mainly include liquid subcooling processes, gas subcooling processes, and partial dry gas recycle processes (RSV). The most common use of the technology for recovering ethane from large and medium-sized oil and gas fields at home and abroad is an RSV technology, a typical RSV technology flow chart is shown in figure 1, and the technology mainly comprises a raw material gas precooling cold box 1, a low-temperature separator 2, an expansion compressor 3, a supercooling cold box 4, a demethanizer 5, an external transmission compressor 6, a tower bottom reboiler 7 and a condensate pump 8, and the connection relation of the components is shown in figure 1; the main process flow for recycling ethane is as follows: and part of the dry gas with higher pressure is condensed sequentially through the raw gas precooling cold box 1 and the supercooling cold box 4, throttled by a throttle valve, enters the top of the demethanizer 5 to provide top reflux, and forms a refrigeration cycle with methane as a main component at the top of the tower, thereby improving the ethane yield. The RSV process has the advantages of high ethane yield up to 95%, low adaptability to CO 2 content in the material gas, easy formation of freeze blocking in the top of the demethanizer, high refrigerating energy consumption, etc.
Energy saving and consumption reduction are more and more emphasized, wherein the recycling of LNG vaporization cold energy has become a hot spot problem of domestic and foreign research, but the recycling of LNG vaporization cold energy is limited to refrigeration of a refrigerator, refrigeration of an air conditioner and the like at present, and huge development and exploration space exists.
In the existing natural gas ethane recovery process, the refrigeration mode usually adopts propane refrigeration, refrigerant refrigeration, expansion refrigeration and the like, and the integrated treatment process of LNG vaporization cold energy recovery and ethane recovery is not considered, so that a process capable of combining LNG vaporization cold energy recovery and natural gas ethane recovery is needed to be explored, energy conservation and consumption reduction of ethane recovery are realized, and the problems that a heat exchanger is easy to corrode and freeze and block in the LNG vaporization process are solved.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides an integrated treatment system and an integrated treatment method for natural gas ethane recovery and LNG vaporization, which are used for recovering a large amount of high-grade cold energy released in the LNG vaporization process for the natural gas ethane recovery, so that the purposes of saving energy and reducing consumption are achieved while the high yield of ethane recovery is ensured, meanwhile, an LNG vaporization device is simplified, and a new way for recycling the LNG cold energy is explored.
The invention discloses an integrated treatment system for natural gas ethane recovery and LNG vaporization, which comprises: the system comprises a main cooling box, a precooling cooling box, a supercooling cooling box, a low-temperature separator, a demethanizer, an expansion compressor and an output compressor; wherein,
The first cold end inlet of the main cold box is used for receiving reflux dry gas, the first cold end outlet of the main cold box is connected with the first cold end inlet of the supercooling cold box, and the first cold end outlet of the supercooling cold box is connected to the top of the demethanizer;
The second cold end inlet of the main cold box is used for receiving part of raw material gas, and the second cold end outlet is respectively connected with the second cold end inlet of the supercooling cold box and the inlet of the low-temperature separator; the cold end inlet of the precooling cold box is used for receiving the rest part of raw material gas, and the cold end outlet is connected with the inlet of the low-temperature separator; the second cold end outlet of the supercooling cold box is connected to the upper part of the demethanizer, the gas outlet of the low-temperature separator is connected to the middle upper part of the demethanizer through the expansion end of the expansion compressor, and the liquid outlet of the low-temperature separator is connected to the middle part of the demethanizer;
The overhead gas outlet of the demethanizer is sequentially connected with the first hot end of the supercooling cold box, the first hot end of the main cold box, the compression end of the expansion compressor and the external transmission compressor, and the dry gas is externally transmitted through the outlet of the external transmission compressor; LNG is transported out to NG after passing through the second hot end of the supercooling cold box and the second hot end of the main cold box.
As a further improvement of the invention, the middle lower part of the demethanizer is provided with two liquid phase side extraction-return lines, one liquid phase side extraction-return line is connected with the first hot end of the precooling cold box, and the other liquid phase side extraction-return line is connected with the second hot end of the precooling cold box.
As a further improvement of the invention, the bottom of the demethanizer is connected with a circulating pipeline of a reboiler, and a liquid outlet of the reboiler is used for condensate outflow through the condensate pump.
As a further improvement of the invention, the return dry gas is part of the export dry gas.
As a further improvement of the invention, a volatile gas outlet is also arranged on the liquid outlet pipe of the low-temperature separator, and the volatile gas outlet is connected with the second cold end inlet of the supercooling cold box.
The invention also discloses an integrated treatment method for natural gas ethane recovery and LNG vaporization, which comprises the following steps:
Precooling raw material gas:
Dividing the raw material gas into two parts, wherein one part enters a main cooling box for precooling, and the other part enters a precooling cooling box for precooling;
and (3) low-temperature separation:
The raw material gas precooled by the main cooling box is divided into two paths, and one path of the raw material gas is mixed with the raw material gas precooled by the precooling cooling box and then enters a low-temperature separator to separate gas phase and liquid phase; the gas phase enters the middle upper part of the demethanizer after passing through the expansion end of the expansion compressor, and the liquid phase enters the middle part of the demethanizer;
gas supercooling:
another path of raw material gas precooled by the main cooling box enters the supercooling cooling box for supercooling, and then enters the upper part of the demethanizer; sequentially introducing the reflux dry gas into a main cooling box for precooling, introducing into a supercooling cooling box for supercooling, and introducing into the top of a demethanizer;
methane separation:
The gas phase, the liquid phase, the raw material gas and the reflux dry gas which enter a demethanizer are separated in the demethanizer to obtain lean gas (more than 98 percent of methane) which is mainly methane and C 2 + condensate; lean gas flows out from the top outlet of the demethanizer, sequentially passes through a cold box and a main cold box for heat exchange and temperature rise, and is pressurized by a compression end of an expansion compressor and then is pressurized by an external compressor for dry gas external transmission; c 2 + condensate flows out from the bottom outlet of the demethanizer, is pressurized by a condensate pump at the bottom of the demethanizer, and enters the next working procedure for ethane separation;
LNG vaporization:
LNG sequentially passes through the cold box for heat exchange and temperature rise, and the main cold box for heat exchange and vaporization, so that NG output is obtained.
As a further improvement of the invention, the main cooling box pre-cools the raw material gas and the reflux dry gas to-60 to-65 ℃, the pre-cooling box pre-cools the raw material gas to-40 to-45 ℃, and the supercooling box supercools the raw material gas and the reflux dry gas to-120 to-125 ℃.
As a further improvement of the present invention, there is also included:
The two liquid phase side extraction-return lines of the demethanizer extract liquid phases, and the liquid phases enter a precooling cold box for reheating and then return to the demethanizer again to be preheated by a reboiler at the bottom of the demethanizer.
Compared with the prior art, the invention has the beneficial effects that:
1. The invention realizes the integration of the natural gas ethane recovery process and the LNG vaporization process, recovers a large amount of high-grade cold energy released in the LNG vaporization process, and is used for refrigerating the natural gas ethane recovery process; not only can obtain higher ethane recovery rate, but also can recycle the cold energy of LNG vaporization, thereby achieving the purposes of energy conservation and consumption reduction;
2. The invention adopts the raw gas to supercool and enter the tower, so as to improve the reflux components at the top of the demethanizer, ensure the ethane yield, and simultaneously reduce the risk of CO 2 at the top of the demethanizer;
3. In the invention, LNG and demethanizer overhead gas are adopted to jointly provide cold energy for the supercooling cold box, compared with the RSV process, which only provides cold energy by the demethanizer overhead gas, thereby being beneficial to improving ethane yield;
4. According to the invention, part of raw gas is supercooled and enters the top of the demethanizer, so that the heavy hydrocarbon content of the overhead material flow is improved, and the risk of CO 2 at the top of the demethanizer is reduced;
5. the LNG and expander refrigeration mode is adopted, so that the refrigeration capacity in the system is fully recycled, and the energy-saving effect is remarkable.
Drawings
FIG. 1 is a prior art RSV process flow diagram;
Fig. 2 is a schematic diagram of an integrated processing system for natural gas ethane recovery and LNG vaporization as disclosed herein.
In the figure:
1. Precooling a raw material gas cold box; 2. a cryogenic separator; 3. an expansion compressor; 4. supercooling cold box; 5. a demethanizer; 6. an output compressor; 7. a bottom reboiler; 8. a condensate pump;
11. A main cooling box; 12. precooling a cold box; 13. supercooling cold box; 14. a reboiler; 15. a cryogenic separator; 16. a demethanizer; 17. an expansion compressor; 18. an output compressor; 19. and a condensate pump.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention is described in further detail below with reference to the attached drawing figures:
As shown in fig. 2, the present invention provides an integrated processing system for natural gas ethane recovery and LNG vaporization, comprising: a main cooling tank 11, a pre-cooling tank 12, a sub-cooling tank 13, a reboiler 14, a cryogenic separator 15, a demethanizer 16, an expansion compressor 17, an external compressor 18 and a condensate pump 19;
the connection relation of the components is as follows:
The first cold end inlet of the main cold box 11 is used for receiving the reflux dry gas, the first cold end outlet of the main cold box 11 is connected with the first cold end inlet of the supercooling cold box 13, and the first cold end outlet of the supercooling cold box 13 is connected to the top of the demethanizer 16; wherein, the reflux dry gas is part of the external dry gas.
The second cold end inlet of the main cold box 11 is used for receiving part of raw material gas, and the second cold end outlet of the main cold box 11 is respectively connected with the second cold end inlet of the supercooling cold box 13 and the inlet of the low-temperature separator 15; the cold end inlet of the precooling cold box 12 is used for receiving the rest of raw material gas, and the cold end outlet of the precooling cold box 12 is connected with the inlet of the low-temperature separator 15; the second cold end outlet of the supercooling cold box 13 is connected to the upper part of the demethanizer 16, the gas outlet of the low-temperature separator 15 is connected to the middle upper part of the demethanizer 16 through the expansion end of the expansion compressor 17, and the liquid outlet of the low-temperature separator 15 is connected to the middle part of the demethanizer 16; further, a volatile gas outlet is further arranged on the liquid outlet pipeline of the low-temperature separator 15, and the volatile gas outlet is connected with the second cold end inlet of the supercooling cold box 13.
The overhead gas outlet of the demethanizer 16 is sequentially connected with a first hot end of a supercooling cold box 13, a first hot end of a main cold box 11, a compression end of an expansion compressor 17 and an external transmission compressor 18, and is used for externally transmitting dry gas through the outlet of the external transmission compressor 18, and the external transmission dry gas can be connected to a first cold end inlet of the main cold box 11 through a backflow branch pipe; the LNG passes through the second hot side of the cold box 13 and the second hot side of the main cold box 11 and then is NG-fed.
The lower middle part of the demethanizer 16 is provided with two liquid phase side extraction-return lines, one liquid phase side extraction-return line is connected with a first hot end of the precooling cold box 12, and the other liquid phase side extraction-return line is connected with a second hot end of the precooling cold box 12; the bottom of the demethanizer 16 is connected with a circulating pipeline of the reboiler 14, and a liquid outlet of the reboiler 14 carries out condensate output through a condensate pump; or the condensate pump may be directly connected to the liquid outlet at the bottom of the demethanizer 16.
Based on the integrated processing system, the integrated processing method for natural gas ethane recovery and LNG vaporization provided by the invention comprises the following steps:
Step 1, precooling raw material gas:
Dividing the raw material gas into two parts, wherein one part enters a main cooling box for precooling, and the other part enters a precooling cooling box for precooling;
step 2, low-temperature separation:
The raw material gas precooled by the main cooling box is divided into two paths, and one path of the raw material gas is mixed with the raw material gas precooled by the precooling cooling box and then enters a low-temperature separator to separate gas phase and liquid phase; the gas phase enters the middle upper part of the demethanizer after passing through the expansion end of the expansion compressor, and the liquid phase enters the middle part of the demethanizer;
Step 3, supercooling gas:
another path of raw material gas precooled by the main cooling box enters the supercooling cooling box for supercooling, and then enters the upper part of the demethanizer; sequentially introducing the reflux dry gas into a main cooling box for precooling, introducing into a supercooling cooling box for supercooling, and introducing into the top of a demethanizer;
Step 4, methane separation:
the gas phase, the liquid phase, the raw material gas and the reflux dry gas which enter a demethanizer are separated in the demethanizer to obtain lean gas mainly containing methane and C 2 + condensate; lean gas flows out from the top outlet of the demethanizer, sequentially passes through a cold box and a main cold box for heat exchange and temperature rise, and is pressurized by a compression end of an expansion compressor and then is pressurized by an external compressor for dry gas external transmission; c 2 + condensate flows out from the bottom outlet of the demethanizer, is pressurized by a condensate pump at the bottom of the demethanizer, and enters the next working procedure for ethane separation; further, the two liquid phase side extraction-return lines of the demethanizer extract liquid phases to enter a pre-cooling cold box for reheating, and then return to the demethanizer again for preheating in a reboiler at the bottom of the demethanizer;
Step 5, LNG vaporization:
LNG sequentially passes through the cold box for heat exchange and temperature rise, and the main cold box for heat exchange and vaporization, so that NG output is obtained.
Examples:
the invention provides an integrated treatment method for natural gas ethane recovery and LNG vaporization, which comprises the following steps:
S1, precooling raw material gas:
The raw material gas is divided into two parts, one part enters the main cooling box 11 to be precooled to be cooled to minus 60 ℃ to minus 65 ℃ and then is divided into two paths, and the other part enters the precooling cooling box 12 to be cooled to minus 40 ℃ to minus 45 ℃.
S2, low-temperature separation:
The raw material gas (cooled to minus 60 to minus 65 ℃) after being precooled by the main cooling box 11 is divided into two paths, wherein one path (about 69 to 75 percent) is mixed with the raw material gas after being cooled by the precooling box 12 and then goes to the low-temperature separator 15 to separate gas phase and liquid phase; the gas phase separated by the cryogenic separator 15 is expanded to 22.5barg through the expansion end of the expansion compressor 17, cooled to about-68 to-72 ℃, and then enters the middle upper part of the demethanizer 16; the separated liquid phase is throttled by a throttle valve to be cooled to minus 59 to minus 62 ℃ and then enters the middle part of the demethanizer 16.
S3, supercooling gas:
The other path of the raw material gas (cooled to minus 60 ℃ to minus 65 ℃) which is precooled by the main cooling box 11 enters the supercooling cooling box 13 to be cooled to minus 120 ℃ to minus 125 ℃, and enters the upper part of the demethanizer 16 after being regulated to 22 barg to 23barg by the regulating valve; part of the dry gas (the pressure is about 47 barg) is returned, and after being precooled to-60 to-65 ℃ by the main cooling box 11, the dry gas enters the supercooling cooling box 13 to be cooled to-120 to-125 ℃, and after being regulated to 22 to 23barg by the regulating valve, the dry gas enters the top of the demethanizer 16.
S4, methane separation:
the gas phase and the liquid phase obtained by separation in the S2 enter a demethanizer 16, the reflux dry gas and part of raw gas after cold treatment in the S3 enter the demethanizer 16, and methane gas and C 2 + condensate are obtained by separation in the demethanizer 16;
Methane gas flows out from the top outlet of the demethanizer 16 to have the temperature of about-102 ℃, is heated to-73 to-78 ℃ through heat exchange of the cold box 13, enters the main cold box 11 to be heated to 15-18 ℃, is pressurized to about 23barg through the compression end of the expansion compressor 17, and enters the output compressor 18 to be pressurized and then is output; the condensate containing ethane flows out from the bottom outlet of the demethanizer 16, and enters the next working procedure for ethane separation after being pressurized by a bottom condensate pump 19;
In order to reasonably recycle cold energy, the lower part of the demethanizer 16 is provided with two liquid phase side extraction-return lines, and the liquid phase extraction temperature of the demethanizer 16 is-43 to-46 ℃ in the liquid phase side extraction-return line of the upper part, and the liquid phase side extraction-return line enters the precooling cold box 12 to exchange heat and raise the temperature to-10 to-15 ℃ and returns to the demethanizer 16; in the lower liquid phase side extraction-return line, the liquid phase extraction temperature of the demethanizer 16 is 0 to minus 5 ℃, the temperature is raised to more than 0 ℃ through heat exchange of the precooling cold box 12, and the liquid phase is returned to the demethanizer 16 through the return line.
S5, LNG vaporization:
LNG (pressure 89barg, temperature about minus 130 ℃) enters a supercooling cold box 13 for reheating, LNG with the temperature of minus 75 ℃ to minus 80 ℃ is obtained, NG is obtained after the LNG enters a main cold box 11 for reheating again, and the NG temperature is about 15 ℃ to 18 ℃ and the pressure is 86 to 88barg.
The invention has the advantages that:
According to the invention, the natural gas ethane recovery process is combined with the LNG vaporization process, so that a large amount of high-grade cold energy released in the LNG vaporization process is fully recycled, simultaneously, NG is also co-produced, the investment of an independently arranged LNG vaporization device is saved, the overall economic benefit is improved, and a new way for recycling the LNG vaporization cold energy is explored; the system is suitable for co-production operation of a common natural gas treatment plant and an LNG receiving station in coastal areas.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. An integrated processing system for natural gas ethane recovery and LNG vaporization, comprising: the system comprises a main cooling box, a precooling cooling box, a supercooling cooling box, a low-temperature separator, a demethanizer, an expansion compressor and an output compressor; wherein,
The first cold end inlet of the main cold box is used for receiving reflux dry gas, the first cold end outlet of the main cold box is connected with the first cold end inlet of the supercooling cold box, and the first cold end outlet of the supercooling cold box is connected to the top of the demethanizer;
The second cold end inlet of the main cold box is used for receiving part of raw material gas, and the second cold end outlet is respectively connected with the second cold end inlet of the supercooling cold box and the inlet of the low-temperature separator; the cold end inlet of the precooling cold box is used for receiving the rest part of raw material gas, and the cold end outlet is connected with the inlet of the low-temperature separator; the second cold end outlet of the supercooling cold box is connected to the upper part of the demethanizer, the gas outlet of the low-temperature separator is connected to the middle upper part of the demethanizer through the expansion end of the expansion compressor, and the liquid outlet of the low-temperature separator is connected to the middle part of the demethanizer; a volatile gas outlet is further arranged on the liquid outlet pipeline of the low-temperature separator and is connected with a second cold end inlet of the supercooling cold box;
The overhead gas outlet of the demethanizer is sequentially connected with the first hot end of the supercooling cold box, the first hot end of the main cold box, the compression end of the expansion compressor and the external transmission compressor, and the dry gas is externally transmitted through the outlet of the external transmission compressor; LNG is transported out to NG after passing through the second hot end of the supercooling cold box and the second hot end of the main cold box.
2. The integrated processing system of claim 1, wherein the lower middle portion of the demethanizer is provided with two liquid-phase side draw-return lines, one liquid-phase side draw-return line being connected to a first hot side of the pre-chill tank and the other liquid-phase side draw-return line being connected to a second hot side of the pre-chill tank.
3. The integrated treatment system of claim 1, wherein a bottom of the demethanizer is connected to a recycle line of a reboiler, and a liquid outlet of the reboiler is configured to conduct condensate export via a condensate pump.
4. The integrated processing system according to any one of claims 1 to 3, wherein the return dry gas is a part of the export dry gas.
5. An integrated process for the recovery of ethane and the vaporization of LNG from natural gas based on an integrated process system according to any one of claims 1 to 4, comprising:
Precooling raw material gas:
Dividing the raw material gas into two parts, wherein one part enters a main cooling box for precooling, and the other part enters a precooling cooling box for precooling;
and (3) low-temperature separation:
The raw material gas precooled by the main cooling box is divided into two paths, and one path of the raw material gas is mixed with the raw material gas precooled by the precooling cooling box and then enters a low-temperature separator to separate gas phase and liquid phase; the gas phase enters the middle upper part of the demethanizer after passing through the expansion end of the expansion compressor, and the liquid phase enters the middle part of the demethanizer;
gas supercooling:
another path of raw material gas precooled by the main cooling box enters the supercooling cooling box for supercooling, and then enters the upper part of the demethanizer; sequentially introducing the reflux dry gas into a main cooling box for precooling, introducing into a supercooling cooling box for supercooling, and introducing into the top of a demethanizer;
methane separation:
The gas phase, the liquid phase, the raw material gas and the reflux dry gas which enter a demethanizer are separated in the demethanizer to obtain lean gas and C 2 + condensate with the main component of methane; lean gas flows out from the top outlet of the demethanizer, sequentially passes through a cold box and a main cold box for heat exchange and temperature rise, and is pressurized by a compression end of an expansion compressor and then is pressurized by an external compressor for dry gas external transmission; c 2 + condensate flows out from the bottom outlet of the demethanizer, is pressurized by a condensate pump at the bottom of the demethanizer, and enters the next working procedure for ethane separation;
LNG vaporization:
LNG sequentially passes through the cold box for heat exchange and temperature rise, and the main cold box for heat exchange and vaporization, so that NG output is obtained.
6. The integrated treatment method according to claim 5, wherein the main cooling tank pre-cools the raw material gas and the reflux dry gas to-60 to-65 ℃, the pre-cooling tank pre-cools the raw material gas to-40 to-45 ℃, and the sub-cooling tank sub-cools the raw material gas and the reflux dry gas to-120 to-125 ℃.
7. The integrated processing method according to claim 5, further comprising:
The two liquid phase side extraction-return lines of the demethanizer extract liquid phases, and the liquid phases enter a precooling cold box for reheating and then return to the demethanizer again to be preheated by a reboiler at the bottom of the demethanizer.
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