CN115468380A - FPLNG pretreatment and liquefaction integrated system and process - Google Patents

FPLNG pretreatment and liquefaction integrated system and process Download PDF

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Publication number
CN115468380A
CN115468380A CN202211354903.0A CN202211354903A CN115468380A CN 115468380 A CN115468380 A CN 115468380A CN 202211354903 A CN202211354903 A CN 202211354903A CN 115468380 A CN115468380 A CN 115468380A
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heat exchanger
plate heat
liquefaction
natural gas
fplng
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朱建鲁
李玉星
韩辉
刘金华
胡其会
王武昌
刘翠伟
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China University of Petroleum East China
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China University of Petroleum East China
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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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0228—Coupling of the liquefaction unit to other units or processes, so-called integrated processes
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
    • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
    • C10L3/10—Working-up natural gas or synthetic natural gas
    • C10L3/101—Removal of contaminants
    • C10L3/102—Removal of contaminants of acid contaminants
    • C10L3/104—Carbon dioxide
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/005—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by expansion of a gaseous refrigerant stream with extraction of work
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
    • F25J1/007—Primary atmospheric gases, mixtures thereof
    • F25J1/0072—Nitrogen
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0203—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle
    • F25J1/0204—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle as a single flow SCR cycle
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0244—Operation; Control and regulation; Instrumentation
    • F25J1/0254—Operation; Control and regulation; Instrumentation controlling particular process parameter, e.g. pressure, temperature
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0275—Construction and layout of liquefaction equipments, e.g. valves, machines adapted for special use of the liquefaction unit, e.g. portable or transportable devices
    • F25J1/0277—Offshore use, e.g. during shipping
    • F25J1/0278—Unit being stationary, e.g. on floating barge or fixed platform
    • 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
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/62—Separating low boiling components, e.g. He, H2, N2, Air
    • 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
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/66—Separating acid gases, e.g. CO2, SO2, H2S or RSH
    • 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
    • F25J2290/62—Details of storing a fluid in a tank

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Ocean & Marine Engineering (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

The invention discloses an FPLNG pretreatment and liquefaction integrated system and a process, comprising a natural gas liquefaction system and a nitrogen expansion system; the natural gas liquefaction system comprises a first plate heat exchanger, a second plate heat exchanger and a cyclone separator which are connected in sequence; the nitrogen expansion system comprises a first compressor, a first cooler, a second compressor, a second cooler and an expander which are connected in sequence; the natural gas liquefaction system and the nitrogen expansion system are coupled through the first plate heat exchanger and the second plate heat exchanger; the invention can increase CO by liquefying natural gas under pressure 2 Solubility of (2), CO 2 Will dissolve in LNG as CO 2 When the concentration of (A) is too high, CO is generated in the liquefaction process 2 Separation of solid CO by means of a cyclone 2 The pretreatment and liquefaction integrated treatment is realized, and a pretreatment and liquefaction system does not need to be independently arranged, so that the whole system is simplified and occupies a large areaThe land area is small, the cost is low, and the method accords with the offshore FPLNG liquefaction process.

Description

FPLNG pretreatment and liquefaction integrated system and process
Technical Field
The invention relates to the technical field of pretreatment and liquefaction of natural gas and water, in particular to an FPLNG pretreatment and liquefaction integrated system and process.
Background
In recent years, floating Production Storage and Offloading (FLNG, also known as FPSO-LNG) devices have been proposed in the ocean engineering community, which integrate liquefaction, storage, loading, unloading and outward transportation of offshore natural gas/petroleum gas, and utilize the easy transportation and Storage characteristics of LNG to reduce the exploitation cost of marginal small gas fields, deep sea natural gas and associated gas resources and realize the development of marginal benefit resources. In the prior art, before liquefaction of the extracted natural gas, deacidification treatment is usually carried out on the natural gas, and an independent deacidification system and a liquefaction system are needed, so that the whole system has large occupied area and higher cost, the PLNG (liquefied natural gas under pressure), namely the natural gas is stored and transported under higher pressure (1-2 MPa), the corresponding condensation temperature is obviously increased to-100-120 ℃ from-160 ℃ in the traditional process, and the CO (carbon monoxide) is also obviously increased to 2 Will increase the solubility of CO when CO is removed prior to natural gas liquefaction 2 There are certain difficulties and there is a need for a system that can integrate FPLNG pre-treatment and liquefaction to simplify the natural gas processing system.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an FPLNG pretreatment and liquefaction integrated system and process, which can separate CO in natural gas while carrying out liquefaction treatment on the natural gas 2 The natural gas is liquefied and simultaneously subjected to deacidification pretreatment.
The technical scheme of the invention is as follows:
in a first aspect of the present invention, there is provided an FPLNG pre-treatment and liquefaction integrated system comprising a natural gas liquefaction system and a nitrogen expansion system; the natural gas liquefaction system comprises a first plate heat exchanger, a second plate heat exchanger and a cyclone separator which are connected in sequence; the nitrogen expansion system comprises a first compressor, a first cooler, a second compressor, a second cooler and an expander which are connected in sequence; the natural gas liquefaction system and the nitrogen expansion system are coupled through the first plate heat exchanger and the second plate heat exchanger.
In some embodiments of the invention, the first plate heat exchanger is provided with an inlet and an outlet for high, medium and low temperature fluids; the second plate heat exchanger is provided with an inlet and an outlet for high and low temperature fluids.
In some embodiments of the present invention, the outlet of the second cooler is connected to the intermediate-temperature fluid inlet of the first plate heat exchanger, the intermediate-temperature fluid outlet of the first plate heat exchanger is connected to the expander and the second plate heat exchanger in sequence, and the low-temperature fluid outlet of the second plate heat exchanger is connected to the low-temperature fluid inlet of the first plate heat exchanger.
In some embodiments of the invention, the cryogenic fluid outlet of the first plate heat exchanger is connected to the first compressor.
In some embodiments of the invention, the high temperature fluid inlet of the first plate heat exchanger is connected to a natural gas pipeline.
In some embodiments of the invention, the first compressor is connected to a nitrogen line.
In some embodiments of the invention, a throttle valve is provided between the second plate heat exchanger and the cyclone separator.
In a second aspect of the invention, an FPLNG pre-treatment and liquefaction integrated process is provided, wherein natural gas is condensed and liquefied through a first plate heat exchanger and a second plate heat exchanger, is depressurized through a throttle valve, and is separated from solid CO through a cyclone separator 2 。
In some embodiments of the invention, after two-stage compression and two-stage cooling, nitrogen firstly enters the first plate heat exchanger for precooling, then enters the expander for expansion and cooling, and the cooled nitrogen firstly enters the second plate heat exchanger for cooling the natural gas and then enters the first plate heat exchanger for cooling the natural gas.
In some embodiments of the invention, the nitrogen at the elevated temperature is re-introduced into the first compressor for compression, and is continuously recycled.
One or more technical schemes of the invention have the following beneficial effects:
(1) The invention utilizes natural gas to increase CO by adopting pressurized liquefaction 2 Solubility of (2), reduced power consumption, CO 2 Content of CO is below 0.5% 2 Will dissolve in LNG as CO 2 When the concentration of (A) is too high, CO is generated in the liquefaction process 2 Separation of solid CO by means of a cyclone 2 Enhanced CO removal from natural gas 2 The efficiency of (c).
(2) The invention removes CO by pretreating natural gas 2 After natural gas liquefaction, pretreatment liquefaction integration treatment is realized, and a pretreatment and liquefaction system does not need to be independently arranged, so that the whole system is simplified, the occupied area is small, the cost is lower, and the offshore FPLNG liquefaction process is met.
(3) Compared with the nitrogen expansion liquefaction technology, the nitrogen expansion liquefaction technology has the advantages that the temperature does not need to be reduced to-160 ℃, the number of equipment is small, and the occupied area is small.
(4) CO of the invention 2 The separation adopts a low-temperature separation method, and CO is realized in the natural gas liquefaction process 2 Separation, the cold energy can be self-supplied, and compared with other methods, the method can reduce energy consumption and reduce occupied area; other methods, such as solution regeneration by chemical absorption, consume a large amount of energy, and the occupied areas of the absorption tower and the regeneration tower are large; the physical absorption method has low energy consumption for solvent regeneration and also has the problem of large occupied area; the recovery rate of methane by the pressure swing adsorption method is low, and the number of equipment sets of the device is large; the membrane separation process has a large hydrocarbon loss.
Drawings
Fig. 1 is a schematic structural view of an FPLNG pretreatment and liquefaction integrated system of the present invention.
In the figure: 1. a first plate heat exchanger; 2. a second plate heat exchanger; 3. a cyclone separator; 4. a first compressor; 5. a first cooler; 6. a second compressor; 7. a second cooler; 8. an expander; 9. a circulator; 10. a throttle valve.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
For convenience of description, the words "up", "down", "left" and "right" in the present invention, if any, merely indicate correspondence with up, down, left and right directions of the drawings themselves, and do not limit the structure, but merely facilitate the description of the invention and simplify the description, rather than indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the invention.
Example 1
The inventor finds that the corresponding condensation temperature of the liquefied natural gas stored and transported under higher pressure (1-2 MPa) is obviously increased from-160 ℃ in the traditional process to-100-120 ℃. CO due to the increase of the condensation temperature 2 The solubility in LNG is also remarkably improved from about 0.01 percent to 1.00 to 3.30 percent, if CO can be utilized 2 The property of solubility in LNG to increase with increasing condensation temperature, CO can be converted 2 To remove the liquefied natural gas, in an exemplary embodiment of the present invention, an integrated FPLNG pre-treatment and liquefaction system is provided, as shown in fig. 1, including a natural gas liquefaction system and nitrogenAn expansion system; the natural gas liquefaction system comprises a first plate heat exchanger 1, a second plate heat exchanger 2 and a cyclone separator 3 which are connected in sequence; the nitrogen expansion system comprises a first compressor 4, a first cooler 5, a second compressor 6, a second cooler 7 and an expander 9 which are connected in sequence; the natural gas liquefaction system and the nitrogen expansion system are coupled by a first plate heat exchanger 1 and a second plate heat exchanger 2.
The natural gas liquefaction system realizes condensation cooling of natural gas and removal of CO in the natural gas 2 (ii) a Wherein, the first plate heat exchanger 1 is provided with an inlet and an outlet for high, medium and low temperature fluids; the inlet and the outlet of high and low temperature fluids are arranged on the second plate heat exchanger 2, the high-temperature fluid inlet on the first plate heat exchanger 1 is connected with a natural gas pipeline, the high-temperature fluid outlet of the first plate heat exchanger 1 is connected with the high-temperature fluid inlet of the second plate heat exchanger 2, the high-temperature fluid outlet of the second plate heat exchanger 2 is connected with the cyclone separator, a throttle valve 10 is arranged between the second plate heat exchanger and the cyclone separator, natural gas is firstly precooled in the first plate heat exchanger, then enters the second plate heat exchanger for deep cooling, is depressurized through the throttle valve, and finally enters the cyclone separator for separating CO 2 And (3) a solid.
The nitrogen expansion system is used for providing cold energy for the natural gas liquefaction system, the first compressor is connected with a nitrogen pipeline, nitrogen is used as a refrigerant, and the natural gas is liquefied by utilizing the pressurization expansion refrigeration of the nitrogen; the coupling mode of the nitrogen system and the natural gas liquefaction system is that the outlet of the second cooler 7 is connected with the medium temperature fluid inlet of the first plate heat exchanger 1, the medium temperature fluid outlet of the first plate heat exchanger 1 is sequentially connected with the expander 8 and the second plate heat exchanger 2, the low temperature fluid outlet of the second plate heat exchanger 2 is connected with the low temperature fluid inlet of the first plate heat exchanger 1, and the low temperature fluid outlet of the first plate heat exchanger is connected with the first compressor 1; the working process of the nitrogen expansion system is as follows: nitrogen gas gets into first compressor 4 and compresses, pressure risees, then gets into 5 condensation cooling of first cooler, reentrant second compressor 6 compresses, pressure risees once more, get into 7 condensation cooling of second cooler after that, nitrogen gas after twice compression condensation cooling, advance to get into first plate heat exchanger 1 and carry out the precooling, then the inflation cooling in getting into expander 8, nitrogen gas after the cooling gets into second plate heat exchanger 2 earlier and cools down the natural gas, reentrant first plate heat exchanger 1 cools down the natural gas.
The nitrogen gas after this embodiment will twice compression condensation cooling, advance to go into first plate heat exchanger and utilize the nitrogen gas from second plate heat exchanger to carry out the precooling, and the nitrogen gas after the precooling transmits cold volume for the natural gas again, carries out the precooling to the natural gas, and the heat transfer process in first plate heat exchanger promptly is: the nitrogen from the second cooler exchanges heat with the nitrogen from the second plate heat exchanger, the temperature of the nitrogen from the second cooler is reduced, and the temperature of the nitrogen from the second plate heat exchanger is increased; the nitrogen from the second plate heat exchanger exchanges heat with the natural gas, the temperature of the nitrogen from the second plate heat exchanger is increased, and the temperature of the natural gas is reduced. The nitrogen of the second cooler enters the first plate heat exchanger firstly because the natural gas is cooled to about minus 115 ℃ in the follow-up process, the nitrogen is at least reduced to minus 115 ℃, otherwise, the temperature is crossed, the nitrogen enters the first plate heat exchanger firstly, the nitrogen can be precooled, and the temperature is lower when the nitrogen is expanded.
According to the embodiment, the nitrogen after being expanded and cooled enters the second plate heat exchanger to exchange heat with the natural gas firstly, and then enters the first plate heat exchanger to exchange heat, so that the cold energy can be efficiently utilized, because the second plate heat exchanger cools the natural gas to-115 ℃ and the temperature of the expanded nitrogen is lower than-115 ℃, the process can be realized, and if the expanded nitrogen enters the first plate heat exchanger firstly, the temperature can rise, the temperature entering the second plate heat exchanger can be higher than-115 ℃, the natural gas cannot be cooled to reach the target temperature, the temperature entering the plate heat exchanger cannot be lower than-115 ℃, and the cold energy cannot be efficiently utilized.
The system of the present embodiment is simulated in simulation software, and the data of one embodiment is as follows:
natural gas: natural at 50 deg.CThe gas is condensed and cooled by the first plate heat exchanger, the temperature is reduced to minus 50 ℃, the gas is subjected to cryogenic cooling by the second plate heat exchanger, the temperature is reduced to minus 115 ℃, the pressure is reduced to 1.7MPa by the throttle valve, and finally the gas is separated by the cyclone separator. Simulated CO in this scheme 2 Initial mole fraction of 0.5%, during liquefaction of natural gas, CO 2 Directly dissolved in natural gas, since CO is increased by the condensation temperature 2 The solubility of the liquefied natural gas in LNG is remarkably improved from about 0.01% to 1.00% -3.30%, and CO can be separated by a cyclone separator in the process of liquefying the natural gas 2 And (5) separating solids.
Nitrogen gas: n at 8.9 ℃ and 150kPa 2 Compressing with a first compressor to 300kPa, heating to 90.84 deg.C, cooling with a first condenser to 20 deg.C, compressing with a second compressor to 600kPa, heating to 109.5 deg.C, cooling with a second condenser to 20 deg.C, cooling with a first plate heat exchanger to 80 deg.C, and condensing to obtain N 2 And expanding to 170kPa, reducing the temperature to-124.7 ℃, exchanging heat with natural gas in a second plate heat exchanger, increasing the temperature to-105.1 ℃, finally entering a first plate heat exchanger for heat exchange, increasing the temperature to 8.941 ℃, and entering a first compressor for circulation.
Example 2
The FPLNG pretreatment and liquefaction integrated process comprises the steps of condensing and liquefying natural gas through a first plate heat exchanger and a second plate heat exchanger, reducing pressure through a throttle valve, and separating solid CO through a cyclone separator 2 ；
Further, after two-stage compression and two-stage cooling, nitrogen firstly enters a first plate heat exchanger for precooling, then enters an expander for expansion and cooling, and the cooled nitrogen firstly enters a second plate heat exchanger for cooling the natural gas and then enters a first plate heat exchanger for cooling the natural gas;
further, the nitrogen with the increased temperature enters the first compressor again for compression and is circulated continuously.
The FPLNG pretreatment and liquefaction integrated process provided by the embodiment adopts pressurized liquefaction, and can increase CO in the liquefaction process 2 Solubility of (2), reduced power consumption, CO 2 When the content is reduced to below 0.5 percent, CO 2 Will dissolve in LNG as CO 2 When the concentration of (A) is too high, CO is generated in the liquefaction process 2 Can separate solid CO by a cyclone separator 2 。
The embodiments described above are intended to illustrate the technical solutions of the present invention in detail, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modification, supplement or similar substitution made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. An FPLNG pretreatment and liquefaction integrated system is characterized by comprising a natural gas liquefaction system and a nitrogen expansion system; the natural gas liquefaction system comprises a first plate heat exchanger, a second plate heat exchanger and a cyclone separator which are connected in sequence; the nitrogen expansion system comprises a first compressor, a first cooler, a second compressor, a second cooler and an expander which are connected in sequence; and the natural gas liquefaction system and the nitrogen expansion system are coupled through the first plate heat exchanger and the second plate heat exchanger.
2. The FPLNG pretreatment and liquefaction integrated system of claim 1, wherein the first plate heat exchanger is provided with high, medium and low temperature fluid inlets and outlets; the second plate heat exchanger is provided with an inlet and an outlet of high and low temperature fluids.
3. The FPLNG pre-treatment and liquefaction integrated system of claim 2, wherein the outlet of the second cooler is connected to the medium temperature fluid inlet of the first plate heat exchanger, the medium temperature fluid outlet of the first plate heat exchanger is sequentially connected to the expander and the second plate heat exchanger, and the low temperature fluid outlet of the second plate heat exchanger is connected to the low temperature fluid inlet of the first plate heat exchanger.
4. The FPLNG pretreatment and liquefaction integrated system of claim 3, wherein the cryogenic fluid outlet of the first plate heat exchanger is coupled to the first compressor.
5. The FPLNG pretreatment and liquefaction integrated system of claim 2, wherein the high temperature fluid inlet of the first plate heat exchanger is coupled to a natural gas pipeline.
6. The FPLNG pretreatment and liquefaction integrated system of claim 1, wherein the first compressor is coupled to a nitrogen pipeline.
7. The FPLNG pretreatment and liquefaction integrated system of claim 1, wherein a throttling valve is disposed between the second plate heat exchanger and the cyclone.
8. An integrated FPLNG pretreatment and liquefaction process is realized by adopting the integrated FPLNG pretreatment and liquefaction system of any one of claims 1 to 7, and is characterized in that natural gas is condensed and liquefied by a first plate heat exchanger and a second plate heat exchanger, is depressurized by a throttle valve, and is separated from solid CO by a cyclone separator 2 。
9. The FPLNG pretreatment and liquefaction integrated process of claim 8, wherein the nitrogen gas after two-stage compression and two-stage cooling first enters the first plate heat exchanger for pre-cooling and then enters the expander for expansion and cooling, and the cooled nitrogen gas first enters the second plate heat exchanger for cooling the natural gas and then enters the first plate heat exchanger for cooling the natural gas.
10. The FPLNG pretreatment and liquefaction integrated process of claim 9, comprising: the nitrogen with the increased temperature enters the first compressor again to be compressed, and the circulation is continued.
CN202211354903.0A 2022-11-01 2022-11-01 FPLNG pretreatment and liquefaction integrated system and process Pending CN115468380A (en)

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