CN112393527A - LNG flash steam recovery method and system - Google Patents

LNG flash steam recovery method and system Download PDF

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Publication number
CN112393527A
CN112393527A CN202011418604.XA CN202011418604A CN112393527A CN 112393527 A CN112393527 A CN 112393527A CN 202011418604 A CN202011418604 A CN 202011418604A CN 112393527 A CN112393527 A CN 112393527A
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China
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heat exchanger
low
flow path
lng
pressure
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熊联友
徐鹏
汤建成
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Beijing Zhongke Fu Hai Low Temperature Technology Co ltd
Technical Institute of Physics and Chemistry of CAS
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Beijing Zhongke Fu Hai Low Temperature Technology Co ltd
Technical Institute of Physics and Chemistry of CAS
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Priority to CN202011418604.XA priority Critical patent/CN112393527A/en
Publication of CN112393527A publication Critical patent/CN112393527A/en
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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
    • F25J3/0209—Natural gas or substitute 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
    • 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
    • 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
    • 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
    • F25J3/028—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 noble gases
    • F25J3/029—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 noble gases of helium
    • 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
    • F25J3/08—Separating gaseous impurities from gases or gaseous mixtures or from liquefied gases or liquefied gaseous mixtures
    • 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
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/40—Processes or apparatus using other separation and/or other processing means using hybrid system, i.e. combining cryogenic and non-cryogenic separation techniques
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/60—Processes or apparatus using other separation and/or other processing means using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
    • 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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/90—Boil-off gas from storage
    • 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
    • F25J2215/30—Helium
    • 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
    • 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
    • F25J2270/30—Quasi-closed internal or closed external helium refrigeration cycle

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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)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

The invention provides an LNG flash steam recovery method and system, wherein the LNG flash steam recovery system comprises an LNG storage tank, a refrigeration cycle flow path and a recovery flow path; the refrigeration cycle flow path comprises a first compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger, a primary expander, a secondary expander, a control valve, a low-pressure pipeline and a high-pressure pipeline; the recovery flow path comprises CH4Rectification column, N2Condensation column, H2The system comprises a condensing tower, a I-stage low-temperature adsorber, a II-stage low-temperature adsorber, a He collecting pipe, a first air guide pipeline, a second air guide pipeline, a third air guide pipeline and a fourth air guide pipeline. In the invention, LNG flash steam generated in the LNG storage tank enters the recovery flow path and is cooled step by step through the refrigeration cycle flow path, and further can be sequentially cooled in CH4Rectification column, N2Condensation column, H2Separating high-purity CH from the condensing tower4、N2、H2And finally, high-recovery-rate and high-purity He is obtained.

Description

LNG flash steam recovery method and system
Technical Field
The invention relates to LNG flash steam treatment, in particular to an LNG flash steam recovery method and an LNG flash steam recovery system.
Background
Helium has special properties such as extremely low boiling point, density, strong chemical and radioactive inertness, is one of indispensable important gases for developing national defense military industry and high technology, and has irreplaceable effects in the fields of national defense, industry and science and technology such as aerospace, nuclear weapons, submarines, saturated diving operation, nuclear magnetic resonance, semiconductors, mobile phones, liquid crystal screens, optical fibers, large scientific devices and the like.
Helium is present in air at only 5ppm, primarily in natural gas, and therefore helium is produced almost entirely from natural gas. The natural gas in the United states is rich in helium resources, the helium content is high (about 0.8 percent on average and is respectively as high as 7.5 percent), and the yield and the consumption amount are the first of the whole world. China is short of helium resources, and the content of helium in natural gas is only 0.2% at most. Has no value for economically extracting helium. Therefore, China has been dependent on importing the required helium from abroad. The helium gas is expensive, so that the method has great influence on the field of using a large amount of helium in China and related scientific research and production units.
At present, in the natural gas field in the large Ordos basin in China, the helium content in the natural gas is about 0.04 percent, although the helium content is very low, the total storage capacity is huge. For storage and transportation, natural gas is typically produced by cryogenic methods to obtain LNG. During LNG production, flash steam, i.e., BOG, is generated in storage tanks and loading stations. Under normal pressure, the liquefaction temperatures of methane, nitrogen, hydrogen and helium are-162 deg.C, -196 deg.C, -253 deg.C and 268.65 deg.C, respectively, and under the pressure of the storage tank, helium, hydrogen and nitrogen are volatilized from LNG. In addition, partial methane gasification can also occur due to heat exchange between the tank walls and the environment. In order to reduce energy consumption, the LNG production process has a special recovery process to recover BOG gas, the BOG gas is compressed to high pressure (fig. 1), then a part of the BOG gas is used as a regeneration gas of a molecular sieve adsorption tower, and a part of the BOG gas enters a cold box to be liquefied into LNG again. After BOG is circulated for many times, helium, nitrogen and the like in the BOG are continuously concentrated, the final helium content can reach 3 percent, and the BOG completely has the industrial development value of purifying helium.
With the rapid development and wide application of the LNG industry, the number of LNG plants in China is increasing, and the amount of BOG waste gas generated in the plants is also increasing, so that the adoption of a new process for extracting helium from BOG in the LNG production is a good method for economically extracting helium from natural gas, which is suitable for the national conditions of China. The method is beneficial to relieving the contradiction between the shortage of helium resources and the helium demand in China.
In addition, for an LNG plant with the nitrogen mole fraction in the raw material gas exceeding 1%, the BOG gas generated by a storage tank and a loading station enters the device again to recover the LNG, and the accumulation of the nitrogen content in the system is easily caused. The higher the nitrogen content in the natural gas, the more difficult it is to liquefy the natural gas, and the higher the power consumption of the liquefaction process. Therefore, the nitrogen in the BOG must be separated at the same time as the purified helium is separated from the BOG.
Disclosure of Invention
The embodiment of the invention relates to an LNG flash steam recovery system, which can comprehensively recover helium, methane and nitrogen from LNG flash steam, has high recovery efficiency and high recovery purity, adopts a simple refrigeration cycle system, is convenient to operate and maintain, and solves the problems of high gas separation difficulty, low recovery efficiency and low purity in BOG waste gas treatment in the prior art.
The embodiment of the invention provides an LNG flash steam recovery system, which comprises an LNG storage tank, a refrigeration cycle flow path and a recovery flow path, wherein the LNG storage tank comprises a refrigeration cycle flow path and a recovery flow path;
the refrigeration cycle flow path comprises a first compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger, a primary expander, a secondary expander, a control valve, a low-pressure pipeline and a high-pressure pipeline, wherein a high-pressure outlet of the first compressor is sequentially connected with the first heat exchanger, the second heat exchanger, the third heat exchanger, the fourth heat exchanger, the primary expander, the fifth heat exchanger and the secondary expander through the high-pressure pipeline, and a low-pressure outlet of the secondary expander is sequentially connected with low-pressure inlets of the sixth heat exchanger, the fifth heat exchanger, the fourth heat exchanger, the third heat exchanger, the second heat exchanger, the first heat exchanger and the first compressor through the low-pressure pipeline;
the recovery flow path comprisesCH4Rectification column, N2Condensation column, H2The system comprises a condensing tower, a He collecting pipe, a I-level low-temperature adsorber, a II-level low-temperature adsorber, a first air guide pipeline, a second air guide pipeline, a third air guide pipeline and a fourth air guide pipeline; the gas outlet of the LNG storage tank is connected to the CH sequentially through the second compressor, the first heat exchanger and the second heat exchanger along the first gas guide pipeline4The gas outlet of the rectifying tower is communicated with the third heat exchanger and the N in sequence through the second gas guide pipeline2Inlet of a condensation column, N2The gas outlet of the condensing tower is communicated with the I-grade low-temperature adsorber, the fourth heat exchanger, the fifth heat exchanger and the H-grade low-temperature adsorber in sequence through the third gas guide pipeline2A condensation column, said H2And the gas outlet of the condensing tower is sequentially communicated with the sixth heat exchanger, the II-grade low-temperature adsorber and the He collecting pipe through the fourth gas guide pipeline.
As an embodiment, the recovery flow path further comprises a reboiler and a heating branch;
the gas inlet of heating branch road is connected the gas outlet of first heat exchanger, the gas outlet of heating branch road is connected the gas inlet of second heat exchanger, just the gas outlet of first heat exchanger with be provided with first governing valve between the gas inlet of second heat exchanger, the reboiler establish ties in on the heating branch road, and in be provided with the second governing valve on the intake pipe way of heating branch road.
As one embodiment, the number of the I-stage low-temperature adsorbers is two, and the two I-stage low-temperature adsorbers are connected in parallel, and the two I-stage low-temperature adsorbers are switched to work, one is used for adsorption, and the other is used for regeneration; the two groups of II-stage low-temperature adsorbers are connected in parallel, and the two groups of II-stage low-temperature adsorbers are switched to work, one group of II-stage low-temperature adsorbers is used for adsorbing, and the other group of II-stage low-temperature adsorbers is used for regenerating.
In one embodiment, the He collecting pipe is connected to the sixth heat exchanger, the fifth heat exchanger, the fourth heat exchanger, the third heat exchanger, the second heat exchanger, and the first heat exchanger in this order.
As one embodiment, the cooling system further comprises a cooling box, wherein the cooling box is provided with a high-pressure pipeline interface, a low-pressure pipeline interface and a CH4Interface, N2Interface, H2The first heat exchanger, the second heat exchanger, the third heat exchanger, the fourth heat exchanger, the fifth heat exchanger, the sixth heat exchanger, the primary expander, the secondary expander, the low-pressure pipeline, the high-pressure pipeline and the recovery flow path are all located in the cold box; the high-pressure pipeline is connected with a high-pressure outlet of the first compressor through the high-pressure pipeline interface, the low-pressure pipeline is connected with a low-pressure inlet of the first compressor through a low-pressure pipeline interface, the first gas guide pipeline is connected with an outlet of the second compressor through the first gas guide pipeline interface, and the CH4Interface with the CH4CH of rectifying column4Outlet, said N2Interface with the N2N of condensation tower2An outlet, said H2Interface with the H2H of condensing tower2And the He collecting pipe interface is connected with the outlet of the He collecting pipe.
The He storage tank is connected with the low-pressure inlet of the first compressor, and a control valve is arranged on a flow path between the He storage tank and the low-pressure inlet of the first compressor.
The embodiment of the invention also provides an LNG flash steam recovery method, wherein LNG flash steam in the LNG storage tank enters the recovery flow path after being compressed;
the LNG flash steam entering the recovery flow path sequentially carries out gradual heat exchange and cooling through a plurality of heat exchangers on the refrigeration circulating flow path; CH is sequentially arranged along the flow direction of LNG flash steam in the recovery flow path4Rectification column, N2Condensation column, H2A condensing tower, a He collecting pipe and CH4Separating CH in LNG flash steam at the rectifying tower4In said N2Separation of N by condensation column2In said H2Separation of H by condensation column2And the remaining He enters the He collection tube.
The embodiment of the invention at least has the following beneficial effects:
in the recovery system provided by the invention, the LNG flash steam generated in the LNG storage tank enters the recovery flow path and is cooled step by step through the refrigeration cycle flow path, and further can be sequentially cooled in CH4Rectification column, N2Condensation column, H2Separating high-purity CH from the condensing tower4、N2、H2And finally the residual He in the LNG flash steam is collected by a He collecting pipe, so that a helium product with very high purity can be obtained, and in addition, CH in the LNG flash steam is treated4、N2、H2The recovery rate of (a) is also very high.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a conventional LNG plant process flow;
fig. 2 is a schematic structural diagram of an LNG flash vapor recovery system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2, an embodiment of the present invention provides an LNG flash vapor recovery system, including an LNG storage tank 1, a refrigeration cycle flow path 2, and a recovery flow path 3, where the refrigeration cycle flow path 2 is used to generate refrigeration to exchange heat with the recovery flow path 3, and the recovery flow path 3 can sequentially recover LNG flash vapor generated in the LNG storage tank 1.
Specifically, the refrigeration cycle flow path 2 includes a first compressor 21, a first heat exchanger 29, a second heat exchanger 22, a third heat exchanger 23, a fourth heat exchanger 24, a turbine inlet control valve 28, a first-stage expander 25, a fifth heat exchanger 211, a second-stage expander 210, a low-pressure pipeline 26, and a high-pressure pipeline 213, and a high-pressure outlet of the first compressor 21 is connected to the first heat exchanger 29, the second heat exchanger 22, the third heat exchanger 23, the fourth heat exchanger 24, the turbine inlet control valve 28, the first-stage expander 25, the fifth heat exchanger 211, and the second-stage expander 210 in this order through the high-pressure pipeline 213; the low-pressure outlet of the secondary expansion machine 210 is connected to the sixth heat exchanger 212, the fifth heat exchanger 211, the fourth heat exchanger 24, the third heat exchanger 23, the second heat exchanger 22, the first heat exchanger 29, and the low-pressure inlet of the first compressor 21 in this order through the low-pressure line 26. The circulating working medium of the refrigeration cycle flow path 2 may be helium, specifically, the refrigeration cycle flow path 2 is connected to the He storage tank 4, helium stored in the He storage tank 4 enters the refrigeration cycle flow path 2, and compressed by the first compressor 21 to form high-pressure helium which enters the high-pressure pipeline 213, usually, helium discharged by the first compressor 21 should be deoiled by the oil separator 27, and sequentially flows through the first heat exchanger 29, the second heat exchanger 22, the third heat exchanger 23 and the fourth heat exchanger 24 by the high-pressure pipeline 213, and adiabatically expanded to low-pressure low-temperature helium by the first-stage expander 25 enters the fifth heat exchanger 211, and adiabatically expanded to lower-pressure low-temperature helium by the second-stage expander 210 enters the low-pressure pipeline 26, and the low-pressure low-temperature helium sequentially flows through the sixth heat exchanger 212, the fifth heat exchanger 211, the fourth heat exchanger 24, the third heat exchanger 23, the sixth heat exchanger 212, The second heat exchanger 22 and the first heat exchanger 29 are compressed in the first compressor 21, so that a circulation process of helium is formed, in the process, the heat exchange temperature of the first heat exchanger 29 is higher than that of the second heat exchanger 22, the heat exchange temperature of the second heat exchanger 22 is higher than that of the third heat exchanger 23, the heat exchange temperature of the third heat exchanger 23 is higher than that of the fourth heat exchanger 243, the heat exchange temperature of the fourth heat exchanger 24 is higher than that of the fifth heat exchanger 211, and the heat exchange temperature of the fifth heat exchanger 211 is higher than that of the sixth heat exchanger 212, so that multi-stage heat exchange cooling can be realized. The inlet side of the high-pressure pipeline 213 corresponding to the first-stage expander 25 is provided with the regulating valve 28 which can regulate the amount of expansion gas entering the first-stage expander 25, and the first-stage expander 25 and the second-stage expander 210 can adopt turbo expanders, so that the whole refrigeration cycle flow path 2 is a turbo-inverted brayton refrigeration cycle, and the first-stage expander 25 and the second-stage expander 210 are refrigeration parts, so that the refrigeration efficiency is high, the refrigeration capacity is large, the refrigeration cycle system is simple, and the operation and maintenance are convenient.
The recovery channel 3 includes CH4Rectifying column 31, N2Condensing towers 32, H2A condensing tower 33, a He collecting pipe 34, a first air guide pipeline 35, a second air guide pipeline 36, a third air guide pipeline 37 and a fourth air guide pipeline 322, wherein the air outlet of the LNG storage tank 1 is connected with a CH sequentially through a second compressor 11 and the first air guide pipeline 354Gas inlet, CH, of rectifying column 314The gas outlet of the rectifying tower 31 is connected with N through a second gas guide pipeline 362Inlet connection of the condensation column 32, N2The outlet of the condensing tower 32 is connected with H through a third air guide pipeline 372Inlet connection of the condensation column 33, H2The outlet of the condensing tower 33 is connected to the He collecting pipe 34 through a fourth gas guiding pipe 322. The LNG flash steam volatilized from the LNG storage tank 1 is reheated to normal temperature and then pressurized by the second compressor 11, then oil is removed by the oil separator 12, and the deoiled LNG flash steam sequentially enters CH4Rectifying column 31, N2Condensing tower 32, I-stage low-temperature adsorber 316 and H2The condensing tower 33, the II-stage low-temperature adsorber 320 and the He collecting pipe 34 are required to be gradually cooled by the refrigeration cycle flow path 2 in the process, and CH in LNG flash steam can be sequentially separated4、N2、H2To obtain high-purity He. Separated CH of course4、N2Either He or H can be collected and recovered by the refrigerating cycle flow path 2 again to separate H2It may be directed to a flare blow down pipe.
Specifically, the LNG flash vapor in the first air guide pipeline 35 exchanges heat and cools through the first heat exchanger 29 and the second heat exchanger 22, the cooled LNG flash vapor enters the rectifying tower 31 for rectification, specifically, a condenser 38 is arranged at the top of the rectifying tower 31, and the cold energy of the condenser 38 can adopt liquid to be rectifiedThe nitrogen is supplied or a separate nitrogen refrigerator is adopted, so that CH in LNG flash steam can be further removed4Is separated in liquid form into CH4The bottom of the rectifying tower 31 and the residual N in the LNG flash steam2He and H2Liquid CH discharged from the top and collected by the rectifying tower 314The purity reaches more than 99 percent.
In a preferred embodiment, a reboiler 39 is provided at the bottom of the rectifying column 31, and CH can be recovered by the reboiler 394The amount of cold of (1). Specifically, the recovery flow path 3 further includes a heating branch 310, the LNG flash steam in the first gas guide line 35 enters the first heat exchanger 29 for heat exchange and temperature reduction, then enters the second heat exchanger 22 for heat exchange and temperature reduction, and enters the rectifying tower 31 through an adjusting valve 312; the gas inlet and the gas outlet of the heating branch 310 are both connected to the first gas guide pipeline 35, the reboiler 39 is connected in series to the heating branch 310, specifically, the gas inlet of the heating branch 310 is connected to the gas outlet of the first heat exchanger 29, the gas outlet of the heating branch 310 is connected to a flow path of the first gas guide pipeline 35 between the second heat exchanger 22 and the first heat exchanger 29, the flow path is provided with a first regulating valve 311, the heating branch 310 is provided with a second regulating valve 312, and the second regulating valve 312 is located on the flow path between the gas inlet of the heating branch 310 and the reboiler 39. In this embodiment, part of the LNG flash steam after heat exchange by the first heat exchanger 29 may continue to enter CH along the first air guide pipeline 354In the rectifying tower 31, a part of the LNG flash steam enters the heating branch 310, and the LNG flash steam entering the heating branch 310 is mixed with CH at the reboiler 394Liquid CH in rectifying column 314Heat exchange, can utilize liquid CH in the reboiler4Pre-cooling the LNG flash vapor in the heating branch 310, and the LNG flash vapor continues to enter the first air guiding pipeline 35 along the heating branch 310. The flow rate of the corresponding flow path can be controlled by adjusting the opening degrees of the first and second regulating valves 311 and 312, so as to control the heating amount of the reboiler 39. In addition, CH4CH separated in the rectifying column 314The cold energy is firstly recovered through the second heat exchanger 22 and the first heat exchanger 29 after being throttled and expanded through a throttle valve 313, and finally collected by the LNG liquefaction system.
Further, from CH4The mixed gas (residual N of LNG flash steam) discharged from the top of the rectifying tower 312He and H2) Through the second air guide pipeline 36 and N2The inlet of the condensing tower 32 is connected to introduce the mixed gas into N2N is separated in the condensation column 322Of course, a throttle 314 is provided in the second air guide line 36 to control the pressure. The mixed gas in the second air guide pipeline 36 is subjected to heat exchange by the third heat exchanger 23 and is cooled to 65K, so that the mixed gas is changed into a gas-liquid two-phase mixture, wherein the liquid is liquid N2At entry into N2The mixture is separated out after the condensation tower 32, the purity of the mixture can reach more than 99 percent, and the rest mixed gas is N2The top of the condensation column 32 is discharged. Separated liquid N2And the cold energy is also recovered through the third heat exchanger 23, the second heat exchanger 22 and the first heat exchanger 29 in sequence after being expanded by a throttle valve 315, and the cold energy can be provided for a condenser in the rectifying tower 31.
Further, N2The mixed gas discharged from the condensing tower 32 enters the third gas guide pipeline 37, and enters the H after being subjected to heat exchange and temperature reduction by the fourth heat exchanger 24 and the fifth heat exchanger 2112Separation of H in the condensation column 332. But due to N2The mixed gas discharged from the condensing tower 32 usually contains trace nitrogen, and an I-stage low-temperature adsorber 316 is connected in series to the third gas guiding pipeline 37, and the adsorption temperature is 65K, so that the trace nitrogen can be adsorbed and removed by the I-stage low-temperature adsorber 316. In a preferred embodiment, there are two groups of I-stage low-temperature adsorbers 316, and two groups of I-stage low-temperature adsorbers 316 are connected in parallel, and the two groups are switched to work, and when one group of I-stage low-temperature adsorbers 316 adsorbs and removes trace nitrogen, the other group of I-stage low-temperature adsorbers 316 is regenerated. In this way, the mixed gas entering the fourth heat exchanger 24 is mainly He and a small amount of H2. The bottoms of the two groups of I-stage low-temperature adsorbers 316 are connected with a flow path for discharging regeneration purge gas to a flare blow-down pipe, and the flow path is also provided with a regulating valve 317.
To completely separate H2To obtain high purity He, a two-stage expander 210 in series on the low pressure line 26 can bring the temperature down to 15K. He collecting tube 34 is connected with the secondThe high-purity low-temperature He in the He collecting pipe 34 is collected and recovered by the sixth heat exchanger 212, the fifth heat exchanger 211, the fourth heat exchanger 24, the third heat exchanger 23, the second heat exchanger 22 and the first heat exchanger 29 in sequence. In this way, the mixed gas in the third air guide pipeline 37 exchanges heat in the fifth heat exchanger 211 and is cooled to 20K, so as to form a gas-liquid two-phase mixture, and the gas-liquid two-phase mixture enters H through a regulating valve 3182In the condensation column 33, in H2Most of the liquid hydrogen is separated in the condensing tower 33 as H2When the liquid hydrogen level in the condensing tower 33 reaches a certain value, it is discharged to the flare vent pipe through a regulating valve 319.
At H2The mixed gas discharged from the condensing tower 33 is He and trace hydrogen, the mixed gas enters the II-stage low-temperature adsorber 320 after being subjected to heat exchange and temperature reduction through the sixth heat exchanger 212, the adsorption temperature of the II-stage low-temperature adsorber 320 is 15K, the trace hydrogen in the mixed gas can be removed by adsorption, and finally the high-purity low-temperature He enters the He collecting pipe 34. Wherein, the two groups of II-stage low-temperature adsorbers 320 are connected in parallel, the two groups of II-stage low-temperature adsorbers 320 are switched to work, when one group of II-stage low-temperature adsorbers 320 adsorbs and removes trace hydrogen, the other group of II-stage low-temperature adsorbers 320 is regenerated. Of course, both sets of stage II cryogenic adsorbers 320 are also provided with a flow path for the regeneration purge gas to be discharged to the flare stack and a regulator valve 321 is provided in the flow path.
In a preferred embodiment, the recovery system further includes a cold box 5, which is a relatively sealed box structure, and most of the structures are disposed in the cold box 5, specifically, the first heat exchanger 29, the second heat exchanger 22, the third heat exchanger 23, the fourth heat exchanger 24, the fifth heat exchanger 211, the sixth heat exchanger 212, the primary expander 25, the secondary expander 210, the low-pressure pipeline 26, the high-pressure pipeline 213, and the recovery flow path 3 are all located in the cold box 5, and correspondingly, a high-pressure pipeline 213 interface, a low-pressure pipeline 26 interface, and a CH interface are disposed on the cold box 54Interface, N2Interface, H2A connector, a He collecting pipe 34 connector and a first air guide pipeline 35 connector, wherein a high-pressure pipeline 213 passes through the high-pressure pipeline 213 interface with the high pressure outlet of the first compressor 21, the low pressure line 26 interface with the low pressure inlet of the first compressor 21 via the low pressure line 26, the first air guide line 35 interface with the outlet of the second compressor 11 via the first air guide line 35, CH4Interface connection CH4CH of rectifying column 314Outlet, N2Interface connection N2N of the condensation column 322Outlet, H2Interface connection H2H of condensing tower 332An outlet, the He collection tube 34 interfaces with an outlet of the He collection tube 34. From this, recovery system is except compressor and storage tank, and most structures all integrate to cold box 5 in, when the gas of separating in the LNG flash distillation vapour is collected to needs, only need with the interface connection that corresponds, and is very convenient, plays the guard action to above-mentioned each structure through cold box 5 simultaneously.
The embodiment of the invention also provides an LNG flash steam recovery method, and by adopting the recovery system, CH in the LNG flash steam volatilized in the LNG storage tank 1 can be recovered4、N2、H2And He is effectively recovered, so that the recovery rate is very high, and the purity is also very high.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (7)

  1. LNG flash distillation vapour recovery system, including the LNG storage tank, its characterized in that: comprises a refrigeration cycle flow path and a recovery flow path;
    the refrigeration cycle flow path comprises a first compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger, a primary expander, a secondary expander, a control valve, a low-pressure pipeline and a high-pressure pipeline, wherein a high-pressure outlet of the first compressor is sequentially connected with the first heat exchanger, the second heat exchanger, the third heat exchanger, the fourth heat exchanger, the primary expander, the fifth heat exchanger and the secondary expander through the high-pressure pipeline, and a low-pressure outlet of the secondary expander is sequentially connected with low-pressure inlets of the sixth heat exchanger, the fifth heat exchanger, the fourth heat exchanger, the third heat exchanger, the second heat exchanger, the first heat exchanger and the first compressor through the low-pressure pipeline;
    the recovery flow path comprises CH4Rectification column, N2Condensation column, H2The system comprises a condensing tower, a He collecting pipe, a I-level low-temperature adsorber, a II-level low-temperature adsorber, a first air guide pipeline, a second air guide pipeline, a third air guide pipeline and a fourth air guide pipeline; the gas outlet of the LNG storage tank is connected to the CH sequentially through the second compressor, the first heat exchanger and the second heat exchanger along the first gas guide pipeline4Gas inlet of the rectifying column, CH4The gas outlet of the rectifying tower is sequentially communicated with the third heat exchanger and the N through the second gas guide pipeline2Inlet of a condensation column, N2The gas outlet of the condensing tower is communicated with the I-grade low-temperature adsorber, the fourth heat exchanger, the fifth heat exchanger and the H-grade low-temperature adsorber in sequence through the third gas guide pipeline2A condensation column, said H2And the gas outlet of the condensing tower is sequentially communicated with the sixth heat exchanger, the II-grade low-temperature adsorber and the He collecting pipe through the fourth gas guide pipeline.
  2. 2. The LNG flash vapor recovery system of claim 1, wherein: the recovery flow path further comprises a reboiler and a heating branch;
    the gas inlet of heating branch road is connected the gas outlet of first heat exchanger, the gas outlet of heating branch road is connected the gas inlet of second heat exchanger, just the gas outlet of first heat exchanger with be provided with first governing valve between the gas inlet of second heat exchanger, the reboiler establish ties in on the heating branch road, just be provided with the second governing valve on the intake pipe way of heating branch road.
  3. 3. The LNG flash vapor recovery system of claim 1, wherein: the I-stage low-temperature adsorbers are divided into two groups, the two groups of I-stage low-temperature adsorbers are connected in parallel, the two groups of I-stage low-temperature adsorbers are switched to work, one group of I-stage low-temperature adsorbers adsorbs the waste water, and the other group of I-stage low-temperature adsorbers regenerates; the two groups of II-stage low-temperature adsorbers are connected in parallel, and the two groups of II-stage low-temperature adsorbers are switched to work, one group of II-stage low-temperature adsorbers is used for adsorbing, and the other group of II-stage low-temperature adsorbers is used for regenerating.
  4. 4. The LNG flash vapor recovery system of claim 1, wherein: the He collecting pipe is sequentially connected with the sixth heat exchanger, the fifth heat exchanger, the fourth heat exchanger, the third heat exchanger, the second heat exchanger and the first heat exchanger.
  5. 5. The LNG flash vapor recovery system of claim 1, wherein: the refrigerator is characterized by further comprising a cold box, wherein the cold box is provided with a high-pressure pipeline interface, a low-pressure pipeline interface and a CH4Interface, N2Interface, H2The first heat exchanger, the second heat exchanger, the third heat exchanger, the fourth heat exchanger, the fifth heat exchanger, the sixth heat exchanger, the primary expander, the secondary expander, the low-pressure pipeline, the high-pressure pipeline and the recovery flow path are all located in the cold box; the high-pressure pipeline is connected with a high-pressure outlet of the first compressor through the high-pressure pipeline interface, the low-pressure pipeline is connected with a low-pressure inlet of the first compressor through a low-pressure pipeline interface, the first gas guide pipeline is connected with an outlet of the second compressor through the first gas guide pipeline interface, and the CH4Interface with the CH4CH of rectifying column4Outlet, said N2Interface with the N2N of condensation tower2An outlet, said H2Interface with the H2H of condensing tower2And the He collecting pipe interface is connected with the outlet of the He collecting pipe.
  6. 6. The LNG flash vapor recovery system of claim 1, wherein: the He storage tank is connected with a low-pressure inlet of the first compressor, and a control valve is arranged on a flow path between the He storage tank and the low-pressure inlet of the first compressor.
  7. The LNG flash steam recovery method is characterized by comprising the following steps: compressing LNG flash steam in the LNG storage tank and then feeding the compressed LNG flash steam into a recovery flow path;
    the LNG flash steam entering the recovery flow path sequentially carries out gradual heat exchange and cooling through a plurality of heat exchangers on the refrigeration circulating flow path; CH is sequentially arranged along the flow direction of LNG flash steam in the recovery flow path4Rectification column, N2Condensing tower, I-stage low-temperature adsorber and H2A condensing tower, a II-stage low-temperature adsorber and a He collecting pipe which are sequentially arranged on the CH4Separating CH in LNG flash steam at the rectifying tower4In said N2Separation of N by condensation column2In said H2Separation of H by condensation column2And the rest He enters the He inlet collecting pipe.
CN202011418604.XA 2020-12-07 2020-12-07 LNG flash steam recovery method and system Pending CN112393527A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113983759A (en) * 2021-10-29 2022-01-28 四川空分设备(集团)有限责任公司 Integrated internal purification helium liquefying device
CN113983760A (en) * 2021-10-29 2022-01-28 四川空分设备(集团)有限责任公司 Helium ultra-low temperature purification and liquefaction system
CN114777349A (en) * 2022-06-16 2022-07-22 中海油能源发展股份有限公司采油服务分公司 Expansion refrigeration cycle system for preparing supercooling medium
CN115127304A (en) * 2022-06-30 2022-09-30 四川帝雷蒙科技有限公司 BOG reliquefaction and recovery system and method capable of improving helium purity
CN115140717A (en) * 2022-05-30 2022-10-04 杭氧集团股份有限公司 Device for producing hydrogen-helium mixed gas by flash distillation, rectification and adsorption combination

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113983759A (en) * 2021-10-29 2022-01-28 四川空分设备(集团)有限责任公司 Integrated internal purification helium liquefying device
CN113983760A (en) * 2021-10-29 2022-01-28 四川空分设备(集团)有限责任公司 Helium ultra-low temperature purification and liquefaction system
CN115140717A (en) * 2022-05-30 2022-10-04 杭氧集团股份有限公司 Device for producing hydrogen-helium mixed gas by flash distillation, rectification and adsorption combination
CN115140717B (en) * 2022-05-30 2023-08-22 杭氧集团股份有限公司 Device for producing hydrogen helium mixed gas by flash distillation, rectification and adsorption combination
CN114777349A (en) * 2022-06-16 2022-07-22 中海油能源发展股份有限公司采油服务分公司 Expansion refrigeration cycle system for preparing supercooling medium
CN114777349B (en) * 2022-06-16 2022-09-06 中海油能源发展股份有限公司采油服务分公司 Expansion refrigeration cycle system for preparing supercooling medium
CN115127304A (en) * 2022-06-30 2022-09-30 四川帝雷蒙科技有限公司 BOG reliquefaction and recovery system and method capable of improving helium purity
CN115127304B (en) * 2022-06-30 2023-11-17 四川帝雷蒙科技有限公司 BOG reliquefaction recovery system and method capable of improving helium purity

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