WO2019137359A1 - 一种基于氩循环的lng冷能利用系统及方法 - Google Patents

一种基于氩循环的lng冷能利用系统及方法 Download PDF

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Publication number
WO2019137359A1
WO2019137359A1 PCT/CN2019/070799 CN2019070799W WO2019137359A1 WO 2019137359 A1 WO2019137359 A1 WO 2019137359A1 CN 2019070799 W CN2019070799 W CN 2019070799W WO 2019137359 A1 WO2019137359 A1 WO 2019137359A1
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argon
heat exchanger
cold energy
lng
circulating
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PCT/CN2019/070799
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English (en)
French (fr)
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毛文军
舒伟
张敏卿
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毛文军
舒伟
张敏卿
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Publication of WO2019137359A1 publication Critical patent/WO2019137359A1/zh

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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
    • F25J3/04—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 for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04278—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using external refrigeration units, e.g. closed mechanical or regenerative refrigeration units
    • 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
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B27/00—Machines, plants or systems, using particular sources of energy
    • 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
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B27/00—Machines, plants or systems, using particular sources of energy
    • F25B27/02—Machines, plants or systems, using particular sources of energy using waste heat, e.g. from internal-combustion engines
    • 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
    • F25J3/04—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 for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04157—Afterstage cooling and so-called "pre-cooling" of the feed air upstream the air purification unit and main heat exchange line
    • 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
    • F25J3/04—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 for air
    • F25J3/044—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 for air using a single pressure main column system only
    • 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
    • F25J2200/72—Refluxing the column with at least a part of the totally 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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/62—Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
    • 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
    • F25J2270/58—Quasi-closed internal or closed external argon refrigeration 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
    • F25J2270/904—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration by liquid or gaseous cryogen in an open loop

Definitions

  • the invention belongs to the technical field of cold energy utilization of liquefied natural gas (LNG), and relates to an LNG cold energy utilization system and method based on argon circulation.
  • LNG liquefied natural gas
  • LNG is formed by liquefying gaseous natural gas by a low-temperature cooling process. In addition to its combustion calorific value or amount of hydrocarbons, it also contains a large amount of high-grade cold energy (-140 ° C - 70 ° C). If direct gasification is used as a fuel or chemical raw material, the cold energy of LNG will be wasted.
  • LNG gasification cold energy is mainly used for refrigeration and freezing (-20 ° C), low temperature power generation (-40 ° C), preparation of dry ice (-80 ° C), low temperature crushing (-140 ° C) and cryogenic air separation (-183- -173 ° C) and other processes.
  • the closer the cold energy utilization temperature is to the LNG gasification temperature the smaller the irreversibility of the process and the higher the utilization efficiency of the cold energy.
  • the LNG cold energy utilization efficiency of the cryogenic air separation is the highest.
  • the LNG cold energy space can save 40%-60% of the electric energy consumption and save about 70% of the cooling. Water consumption has significant economic benefits.
  • the main difference between LNG cold energy air separation and conventional full liquid air separation is that the conventional air separation process completes the nitrogen compression cooling and expansion refrigeration cycle through the work of the motor, which is mainly consumed as electric energy, while the LNG cold energy air separation is to gasify the LNG.
  • the process's cold energy is directly supplied to the air separation system, which significantly reduces the circulating nitrogen compression power and cooling condensation energy consumption of the nitrogen cycle refrigeration system compared to conventional air separation.
  • the LNG gasification and the generation of cold energy are simultaneous, so that the air separation plant can obtain a large amount of cold in a short time, greatly shortening the startup time, that is, opening and stopping, improving the production efficiency, and achieving system miniaturization and armoring. Chemical.
  • the advantages of LNG air separation are significant. There are more and more related research work and industrial devices at home and abroad. The process organization is developing in a more energy-saving direction.
  • the system operating pressure and the maximum operating pressure can be as low as 0.35 MPa and 1.5 MPa, respectively.
  • the LNG cold energy air separation system has only two ways to utilize LNG cold energy. One directly uses LNG gasification cold energy to exchange heat with the tower to purify the air, and the other is through LNG-nitrogen heat exchange. Nitrogen cycle refrigeration.
  • CN101532768A and CN201387202Y describe a space division system utilizing cold energy of liquefied natural gas.
  • the system is characterized by: an LNG-nitrogen heat exchanger and a nitrogen-nitrogen heat exchanger, with pressurized nitrogen as a closed circulation medium.
  • nitrogen has a low latent heat value, a large amount of compression, and a high energy consumption.
  • CN101943512A describes a space division method utilizing cold energy of liquefied natural gas.
  • the method is characterized in that low-temperature low-pressure nitrogen is compressed to form pressure nitrogen, which has a large pressure loss during heat exchange, and requires multiple compressors, which raises the operating pressure of the circulating pipeline and pipeline equipment. Requirements.
  • This method does not consider the leakage problem of heat exchange between nitrogen and LNG. LNG leakage will enter the pressure pipeline for circulation, causing serious safety problems.
  • CN101033909A discloses an air separation system for obtaining liquid oxygen and liquid nitrogen.
  • the system features: a three-stage nitrogen compressor with low pressure, medium pressure and high pressure.
  • the process of compressing and utilizing nitrogen in the circulating medium is cumbersome, high in operation and maintenance, and no specific operating standard is given.
  • CN202675796U discloses a device for producing a liquid air separation product using LNG cold energy.
  • the device is characterized in that the pressure of the liquid nitrogen in the nitrogen-nitrogen heat exchanger is lower than the pressure on the nitrogen side to ensure the safety of the air separation device.
  • the heat exchanger needs to be connected with a nitrogen medium interface of different pressures, which puts high requirements on the operating pressure of the equipment.
  • LNG gasification at atmospheric pressure has a boiling point of -162 ° C.
  • the pressure of N 2 corresponding to this temperature is 1.6 MPa, that is, only when nitrogen gas is pressed to 1.6 MPa or more, LNG cold energy can be directly utilized, and N 2 cycle pressure is high. Big.
  • the air separation tower needs to operate at a lower pressure, generally not exceeding 1.0 MPa.
  • the LNG space fraction with N 2 as the cold circulation medium is low.
  • LNG cold energy space utilization rate of LNG cold energy is currently 15%-20%, and a large amount of LNG cold energy is wasted. Therefore, how to effectively improve the LNG cold energy utilization rate is a technical problem that needs to be solved at present.
  • the technical problem to be solved by the present invention is to provide an LNG cold energy utilization system and method based on an argon cycle in view of the deficiencies of the prior art.
  • the LNG cold energy utilization system based on argon circulation adopts LNG-argon heat exchanger, uses argon gas as working medium to recover LNG cold energy through heat pump, and uses argon Joule-Thomson effect to improve cold energy grade and transfer cooled medium. It can effectively improve the utilization rate of LNG cold energy, increase the utilization rate of LNG cold energy to over 90%, and better realize the concept of green environmental protection.
  • the present invention adopts the following technical solutions:
  • An LNG cold energy utilization system based on an argon cycle includes a natural gas cold energy recovery system, an argon circulation system, and a cold energy utilization system;
  • the natural gas cold energy recovery system includes LNG-argon a gas heat exchanger;
  • the argon circulation system includes a series circuit composed of a liquid argon pipe, a circulating argon throttle expansion valve, a circulating argon heat exchanger, an argon gas pipeline, a circulating argon compressor, and an LNG-argon heat exchanger
  • the cooled medium in the cold energy utilization system is connected to the heat release pipeline in the circulating argon heat exchanger for heat exchange with the argon in the return argon heat exchanger return line to realize the LNG cold energy exchange process.
  • the natural gas cold energy recovery system further includes an LNG feed pipe, an NG (natural gas) compressor, an NG cooler, and an NG user pipe;
  • the NG cooler includes an NG heat release pipe and a cooling water heat recovery pipe;
  • the feed pipe, the heat recovery pipe of the LNG-argon heat exchanger, the NG compressor, the NG heat release pipe and the NG user pipe are sequentially connected to form a series passage, and the cooling water return heat pipe is connected with the cooling water circulation system;
  • the circulating argon heat exchanger comprises a circulating argon-nitrogen heat exchanger, the inlet of the circulating argon-nitrogen heat exchanger is connected to the outlet of the circulating argon throttle expansion valve, the outlet of the circulating argon-nitrogen heat exchanger and the circulating argon gas
  • the inlets of the compressor are connected;
  • the cold energy utilization system includes a nitrogen cooling system including a gas nitrogen inlet pipe and a liquid nitrogen outlet pipe, and the gas nitrogen inlet pipe is connected to an input end of the circulating argon-nitrogen heat exchanger heat release pipe, and the liquid nitrogen outlet The pipe is connected to the output of the heat release line of the circulating argon-nitrogen heat exchanger.
  • the circulating argon heat exchanger further includes a circulating argon-air heat exchanger, and an inlet of the circulating argon-nitrogen heat exchanger is connected to a circulating argon throttle expansion valve outlet, the circulating argon-nitrogen heat exchanger An outlet connected to the inlet of the circulating argon-air heat exchanger, the outlet of the circulating argon-air heat exchanger being connected to the inlet of the circulating argon compressor;
  • the cold energy utilization system further includes a clean air cooling system including a clean air inlet duct and a cold air outlet duct, the purifying air inlet duct and an input end of the circulating argon-air heat exchanger radiating duct The connection, the cold air outlet pipe is connected to the output of the circulating argon-air heat exchanger heat release pipe.
  • the cold energy utilization system further comprises an air separation system, the outlet end of the cold air outlet pipe is connected to the air inlet end of the air separation system, so that the cold air enters the air separation system for separation, and the separated gas nitrogen passes.
  • the gas-nitrogen inlet pipe enters the heat exchange in the circulating argon-nitrogen heat exchanger.
  • liquid nitrogen outlet pipe is divided into two paths, one is connected to the product liquid nitrogen storage tank, and the other is connected to the air separation system to fractionate the return port of the upper tower.
  • the argon circulation-based LNG cold energy utilization system of the invention uses the argon gas as the working medium to recover the LNG cold energy through the heat pump, and uses the argon Joule-Thomson effect to improve the cold energy grade and then transfers it to the nitrogen for the cryogenic air separation.
  • the cryogenic separation of air (or liquid nitrogen) oxygen (or liquid oxygen) and argon (or liquid argon) system cold gas is produced by LNG gasification.
  • the invention also provides a cold energy utilization method of the LNG cold energy utilization system based on the above argon circulation, comprising the steps of: heat exchange of LNG with argon gas in LNG-argon heat exchanger, gasification of LNG, condensation of argon gas, Liquid argon is formed, and then enters the throttle expansion valve through the liquid argon line to cool down, and then enters the circulating argon heat exchanger, becomes a gaseous argon after the heat exchange between the circulating argon heat exchanger and the cooled medium, and then enters the argon compression.
  • the machine is pressurized, and then re-entered into the LNG-argon heat exchanger to condense and absorb the LNG cold energy, and reciprocate to realize the LNG cold energy exchange process.
  • the gasification pressure of the LNG in the LNG-argon heat exchanger is from 0.1 MPa to 1.0 MPa, and the corresponding temperature is from -162 ° C to -124 ° C.
  • the pressure of the argon gas after circulating the argon compressor is in the range of 0.7 MPa to 4.8 MPa, and the corresponding temperature is: -162 ° C - 122 ° C.
  • the cyclic argon is subjected to throttling expansion and has a pressure of 0.1 MPa to 1.6 MPa and a temperature of -186 ° C to 148 ° C.
  • the preferred pressure range is from 0.1 MPa to 0.7 MPa and the temperature is from -186 ° C to 163 ° C.
  • the cooled medium comprises nitrogen
  • the circulating argon heat exchanger comprises a circulating argon-nitrogen heat exchanger.
  • the nitrogen pressure is 0.1 MPa to 3.4 MPa
  • the temperature is -186. °C - 147 ° C.
  • the pressure ranges from 0.1 MPa to 1.5 MPa
  • the temperature ranges from -186 ° C to 163 ° C.
  • the cooled medium further comprises purified air
  • the circulating argon heat exchanger further comprises a circulating argon-air heat exchanger, wherein the corresponding cooling process is: the LNG feed pipe is exchanged with the LNG-argon gas through the pipeline The heat exchanger is connected, LNG is gasified in the LNG-argon heat exchanger, argon gas is condensed, and LNG exchanges cold energy to the circulating argon gas.
  • the NG enters the NG compressor and the NG cooler for compression and cooling, and is delivered to each user through the pipeline according to the pressure required by the user; the liquid argon formed by the LNG low-temperature cold energy is obtained in the LNG-argon heat exchanger.
  • liquid argon will be high grade Cold energy is transferred to gaseous nitrogen.
  • the gaseous argon of the circulating argon-nitrogen heat exchanger is connected to the circulating argon-air heat exchanger through a pipeline to further recover the circulating argon cold energy, then enters the argon compressor for pressurization, and then re-enters the LNG-argon gas exchange.
  • the heat exchanger condenses and absorbs LNG cold energy and circulates back and forth. Through this process, the LNG cold energy is upgraded and passed to the air separation system;
  • the gaseous nitrogen (GN 2 ) from the air separation system enters the circulating argon-nitrogen heat exchanger, and the argon cold energy is condensed into liquid nitrogen (LN 2 ), and the LN 2 is returned to the air separation system, and is partially used for reflux.
  • the rest is used as a product; the purified air passes through the circulating argon-air heat exchanger, absorbs the circulating argon cold energy and then enters the air separation tower for separation; the circulating cooling water passes through the NG cooler to cool the compressed NG, and then returns To the circulating cooling water system.
  • the critical temperature of argon and the boiling point at the same pressure are higher than nitrogen, between nitrogen and methane.
  • the use of argon as the circulating medium solves the stringent requirements of nitrogen pressure in the direct heat transfer of LNG-nitrogen.
  • the argon cycle can recover LNG cold energy in a wide range of LNG gasification pressure, and the compression ratio of circulating argon refrigeration is lower than that of the nitrogen cycle, thereby saving compressor power consumption and maximizing LNG cold energy utilization efficiency;
  • the LNG cold energy can be increased from -162 ° C under normal pressure to above -184 ° C, which improves the cold energy grade.
  • the high grade cold energy can be directly used in the low pressure air separation system. Dividing the separation efficiency of the distillation column and reducing the investment amount of the air separation system;
  • the argon latent heat is higher than that of nitrogen. Compared with the nitrogen circulation in the general LNG cold energy air separation system, the argon gas circulation has less gas and low energy consumption;
  • Argon gas circulation can avoid direct heat exchange between LNG and air medium, prevent safety problems caused by natural gas leakage into air separation system, and make the whole system safer.
  • 1-LNG feed pipe 2-LNG-argon heat exchanger, 3-NG compressor, 4-NG cooler, 401-cooling water inlet pipe, 402-cooling water outlet pipe, 5-NG user pipe , 6-cycle argon throttle expansion valve, 601-liquid argon pipeline, 7-cycle argon-nitrogen heat exchanger, 701-GN 2 inlet piping, 702-LN 2 outlet piping, 8-cycle argon-air heat exchanger, 801-purified air inlet pipe, 802-cold air outlet pipe, 9-cycle argon compressor, 901-argon pipe, 10-space splitter, 1001-vacuum tower nitrogen product outlet pipe, 1002-space splitter Nitrogen outlet pipe, 1003-vacant tower oxygen product outlet pipe.
  • 1 is an LNG cold energy utilization system based on an argon cycle, including a natural gas cold energy recovery system, an argon circulation system, and a cold energy utilization system; a natural gas cold energy recovery system including an LNG-argon heat exchanger 2; and an argon circulation system including a liquid a series circuit composed of an argon pipe 601, a circulating argon throttle expansion valve 6, a circulating argon heat exchanger, an argon gas pipe 901, a circulating argon compressor 9 and an LNG-argon heat exchanger 2;
  • the cooling medium is connected to the heat release line in the circulating argon heat exchanger for heat exchange with the argon in the return argon heat exchanger return line to realize the LNG cold energy exchange process.
  • the natural gas cold energy recovery system further includes an LNG feed pipe 1, an NG compressor 3, an NG cooler 4, and an NG user pipe 5;
  • the NG cooler 4 includes an NG heat release pipe and a cooling water heat recovery pipe;
  • the regenerative pipeline of the LNG-argon heat exchanger 2, the NG compressor 3, the NG heat release pipe and the NG user pipe 5 are sequentially connected to form a series passage, and the cooling water return heat pipe is respectively passed through the cooling water inlet pipe 401 and the cooling water outlet pipe 402.
  • the cooling water circulation system is connected; LNG in the present application refers to liquefied natural gas, and NG refers to natural gas.
  • the circulating argon heat exchanger comprises a circulating argon-nitrogen heat exchanger 7 and a circulating argon-air heat exchanger 8, and an inlet of the circulating argon-nitrogen heat exchanger 7 is connected to the outlet of the circulating argon throttle expansion valve 6, circulating argon - the outlet of the nitrogen heat exchanger 7 is connected to the inlet of the circulating argon-air heat exchanger 8, the outlet of the circulating argon-air heat exchanger 8 is connected to the inlet of the circulating argon compressor 9;
  • the cold energy utilization system comprises a nitrogen cooling system
  • the nitrogen cooling system includes a gas nitrogen inlet pipe 701 and a liquid nitrogen outlet pipe 702.
  • the gas nitrogen inlet pipe 701 is connected to the input end of the heat release pipe of the circulating argon-nitrogen heat exchanger 7, and the liquid nitrogen outlet pipe 702 is exchanged with the circulating argon-nitrogen gas.
  • the output of the heat release line of the heat exchanger 7 is connected.
  • the cold energy utilization system further includes a clean air cooling system including a purified air inlet pipe 801 and a cold air outlet pipe 802, and the purified air inlet pipe 801 is connected to an input end of the heat release pipe of the circulating argon-air heat exchanger 8.
  • the cold air outlet conduit 802 is connected to the output of the heat release line of the circulating argon-air heat exchanger 8.
  • the cold energy utilization system further includes an air separation system, and the outlet end of the cold air outlet pipe 802 and the air separation system are empty.
  • the air inlet ends of the sub-column 10 are connected to allow cold air to enter the air separation system to separate the fractions, and in the air separation column 10, the nitrogen gas at the top of the tower enters the condenser 7 through the conduit 701 to be condensed into liquid nitrogen, and then through the liquid nitrogen.
  • the return pipe 702 is returned to the air separation tower, and is divided into two paths, one is connected to the product liquid nitrogen storage tank, and the nitrogen product is turned into the nitrogen product through the air separation tower nitrogen product outlet pipe 1001, and the other is connected to the air separation system. After the sub-column is cooled, the nitrogen of the air separation tower is discharged through the air separation tower sewage nitrogen outlet pipe 1002, and finally the oxygen product 1003 is obtained through the air separation tower oxygen product outlet pipe at the bottom of the air separation tower.
  • the air separation system of the present invention is the same as the prior art.
  • the working principle of the argon circulation-based LNG cold energy utilization system of the present invention is as follows: LNG cold energy release system, LNG enters LNG-argon heat exchanger 2 through feed pipe 1, and LNG in LNG-argon heat exchanger 2 Gasification, argon condensation, LNG exchanges cold energy for circulating argon. After the cold energy is released, the NG enters the NG compressor 3 and is compressed to the user's required pressure, and then enters the NG cooler 4 for cooling and cooling, and then sent to the user through the NG user pipe 5.
  • the NG cooler 4 uses circulating cooling water for heat extraction, and the circulating cooling water is connected to the circulating water treatment system through the cooling water inlet and outlet; the circulating argon refrigeration system, circulating argon gas to obtain LNG in the LNG-argon heat exchanger 2
  • the low temperature cold energy forms liquid argon, enters the throttle expansion valve 6 through the liquid argon pipe 601, and is cooled by the Joule-Thomson effect, and then enters the circulating argon-nitrogen heat exchanger 7, where the liquid argon gas is vaporized, nitrogen gas Condensation, liquid argon transfers high grade cold energy to liquid nitrogen.
  • the low-temperature air argon of the circulating argon-nitrogen heat exchanger 7 is connected to the circulating argon-air heat exchanger 8 through a pipeline, where the purified air is cooled, and the circulating argon cold energy is further recovered, and the reheated argon gas passes through the argon gas.
  • the gas pipe 901 enters the compressor 9 to be pressurized, and then re-enters the LNG-argon heat exchanger 2 to cool down, condense and absorb the LNG cold energy, and recirculates and recirculates, then the LNG cold energy can be upgraded and passed to the air separation system; the nitrogen condensation and The air pre-cooling system, the GN 2 from the air separation system enters the circulating argon-nitrogen heat exchanger 7 through the pipeline 701, absorbs the liquid argon cold energy and condenses into LN 2 , and the LN 2 passes through the pipeline 702 and returns to the air separation system; The air enters the circulating argon-air heat exchanger through the purified air inlet pipe 801, further absorbs the circulating argon cold energy, and then enters the air separation tower through the cold air outlet pipe 802 for rectification and separation.
  • the nitrogen gas passes through the top of the tower.
  • the GN 2 inlet pipe 701 enters the condenser 7 to be condensed into liquid nitrogen, and then returns to the air separation column through the liquid nitrogen outlet pipe 702, and partially serves as a reflux for the remaining nitrogen product, and the nitrogen of the air separation tower is discharged through the pipe, in the air separation tower Bottom oxygen product
  • the cold energy utilization method of the argon circulation-based LNG cold energy utilization system of the present invention adopts the LNG cold energy utilization system of the implementation 1, which is specifically as follows: LNG atmospheric pressure (0.1 MPa) gasification: LNG enters LNG-argon through the feed pipe The gas heat exchanger is subjected to atmospheric pressure gasification at a temperature of -162 ° C. After gasification, heat is further exchanged with the gas and argon. After the cold energy is released, the reheated NG enters the NG compressor and is compressed to the user's required pressure. The NG cooler is cooled by circulating cooling water and sent to the user through the pipeline.
  • LNG atmospheric pressure (0.1 MPa) gasification LNG enters LNG-argon through the feed pipe The gas heat exchanger is subjected to atmospheric pressure gasification at a temperature of -162 ° C. After gasification, heat is further exchanged with the gas and argon. After the cold energy is released, the reheated NG enters the NG compressor and is compressed to the user's required pressure.
  • the argon gas from the circulating argon compressor has a pressure of 0.8 MPa, and is exchanged with LNG in the LNG-argon heat exchanger to obtain liquid argon which is cooled by LNG cold energy to -160 ° C, and enters the throttle expansion valve through the pipeline. After cooling by the Joule-Thomson effect, liquid argon cold energy is transferred to liquid nitrogen in a circulating argon-nitrogen heat exchanger.
  • the pressure after circulating argon through the throttle expansion valve depends on the operating pressure of the air separation column.
  • the operation pressure of the air separation column is 0.35 MPa
  • the nitrogen temperature at the top of the column is -182 ° C
  • the pressure after circulating the argon through the throttle expansion valve can be 0.15 MPa
  • the corresponding circulating argon gasification temperature is -184 ° C, thereby realizing The transfer of LNG cold energy to the air separation system after the grade (lower temperature) is improved.
  • the LNG atmospheric pressure gasification adopts other patented nitrogen circulation methods, it is necessary to compress the nitrogen gas to 1.7 MPa or more in order to absorb the gasification cold energy of the atmospheric pressure LNG.
  • the argon circulation mode of the patent the argon compression pressure only needs to be 0.8 MPa, and since the latent heat of argon gasification is larger than that of nitrogen, the circulation amount of argon gas is relatively small, and the efficient utilization of LNG cold energy is realized.
  • the cold energy utilization method of the argon circulation-based LNG cold energy utilization system of the present invention adopts the LNG cold energy utilization system of the implementation 1, which is specifically as follows: LNG gasification pressure 0.3 MPa: pressure LNG 0.3 MPa enters LNG through the feed pipe - Argon heat exchanger, where gasification is carried out at a temperature of -146 ° C, after heat exchange with circulating argon, releasing cold energy and reheating, then entering the NG compressor to be compressed to the user's required pressure, and then circulating cooling water through the NG cooler After cooling, send it to the user through the pipeline.
  • LNG gasification pressure 0.3 MPa pressure LNG 0.3 MPa enters LNG through the feed pipe - Argon heat exchanger, where gasification is carried out at a temperature of -146 ° C, after heat exchange with circulating argon, releasing cold energy and reheating, then entering the NG compressor to be compressed to the user's required pressure, and then circulating cooling water through the NG cooler After cooling, send it to the user through the pipeline
  • the argon gas from the circulating argon compressor has a pressure of 1.9 MPa, and is exchanged with LNG in the LNG-argon heat exchanger to obtain liquid argon which is cooled by LNG cold energy to -144 ° C, and enters the throttle expansion valve through the pipeline.
  • the liquid argon cold energy is transferred to the liquid nitrogen in the circulating argon-nitrogen heat exchanger, and the pressure after circulating the argon through the throttle expansion valve depends on the operating pressure of the air separation column.
  • the operating pressure of the air separation column is 0.8 MPa
  • the nitrogen temperature at the top of the column is -172 ° C
  • the pressure after circulating the argon through the throttle expansion valve can be 0.3 MPa
  • the corresponding circulating argon gasification temperature is -174 ° C
  • the LNG gasification temperature of -130 °C at a pressure of 0.3 MPa is close to the critical point of nitrogen (pressure 3.35 MPa, temperature -147 ° C), and it is impossible to recover LNG cold energy by other patented nitrogen circulation methods.
  • the argon circulation mode of the patent can recover LNG gasification cold energy (corresponding temperature -162 ° C - 124 ° C) in the range of pressure 0.1 MPa - 1.0 MPa, and realize high efficiency of LNG cold energy in a wide range of low temperature. use.
  • the cold energy utilization method of the argon circulation-based LNG cold energy utilization system of the present invention adopts the LNG cold energy utilization system of the implementation 1, which is specifically as follows: LNG gasification pressure 1.0 MPa: pressure of 1.0 MPa of LNG enters LNG through the feed pipe - Argon heat exchanger, where gasification is carried out at a temperature of -124 ° C, after heat exchange with circulating argon, releasing cold energy and reheating, then entering the NG compressor to be compressed to the user's required pressure, and then circulating cooling water through the NG cooler After cooling, send it to the user through the pipeline.
  • LNG gasification pressure 1.0 MPa pressure of 1.0 MPa of LNG enters LNG through the feed pipe - Argon heat exchanger, where gasification is carried out at a temperature of -124 ° C, after heat exchange with circulating argon, releasing cold energy and reheating, then entering the NG compressor to be compressed to the user's required pressure, and then circulating cooling water through the NG cooler After cooling, send it to the
  • the argon gas from the circulating argon compressor has a pressure of 4.8 MPa, and is exchanged with LNG in the LNG-argon heat exchanger to obtain liquid argon which is cooled by LNG cold energy to -123 ° C, and enters the throttle expansion valve through the pipeline.
  • the liquid argon cold energy is transferred to the liquid nitrogen in the circulating argon-nitrogen heat exchanger, and the pressure after circulating the argon through the throttle expansion valve depends on the operating pressure of the air separation column.
  • the operation pressure of the air separation column is 1.5 MPa
  • the nitrogen temperature at the top of the column is -162 ° C
  • the pressure after circulating the argon through the throttle expansion valve can be 0.6 MPa
  • the corresponding circulating argon gasification temperature is -164 ° C, thereby realizing The transfer of LNG cold energy to the air separation system after the grade (lower temperature) is improved.

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Abstract

提供一种基于氩循环的LNG冷能利用系统及其方法。LNG冷能利用系统包括天然气冷能回收系统、氩循环系统和冷能利用系统；天然气冷能回收系统包括LNG-氩气换热器（2）；氩循环系统包括由循环氩节流膨胀阀（6）、循环氩换热器、循环氩气压缩机（9）和LNG-氩气换热器（2）组成的串联回路；冷能利用系统中的被冷却介质与循环氩换热器中的放热管路连接，用于与循环氩换热器回热管路中的氩换热，实现LNG冷能交换。

Description

一种基于氩循环的LNG冷能利用系统及方法 技术领域
本发明属于液化天然气(LNG)冷能利用技术领域，涉及一种基于氩循环的LNG冷能利用系统及方法。
背景技术
我国是能源消费在国，每年都需要进口大量的清洁能源天然气作为燃料或原料。为运输方便，相当比例的进口天然气是以LNG形式进行海运。LNG是通过低温冷却工艺将气态天然气液化而成，除其本身所含的燃烧热值或碳氢物质的量外，还附带了大量高品位冷能(-140℃--70℃)。若直接气化作为燃料或化工原料利用，则LNG的冷能会白白浪费。
目前LNG气化冷能主要用于冷藏冷冻(-20℃)、低温发电(-40℃)、制取干冰(-80℃)、低温粉碎(-140℃)及深冷空分(-183--173℃)等过程。从热力学角度讲，冷能利用温度与LNG气化温度越接近，其过程的不可逆性越小，冷能的利用效率越高。与上述其它过程相比，深冷空分LNG冷能利用效率最高，LNG冷能空分与传统全液体空分相比，可节约40％--60％的电能消耗，节约70％左右的冷却水消耗，经济效益显著。
LNG冷能空分与常规全液体空分的主要区别在于，常规空分流程通过电机做功完成氮的压缩冷却及膨胀制冷循环，主要消耗为电能，而LNG冷能空分则是将LNG气化过程的冷能直接提供给空分系统，与常规空分相比，显著减少了氮循环制冷系统循环氮压缩功耗及冷却冷凝能耗，流程得以简化。另外LNG气化与产生冷能是同时的，可使空分设备在很短时间内得到大量冷量，大大缩短启动时间，即开即停，提高了生产效率，可实现系统小型化、撬装化。
LNG空分优势显著，国内外的相关研究工作及工业装置越来越多，流程组织向更节能的方向发展，系统操作压力及最高操作压力可分别低至0.35MPa、1.5MPa。然而到目前为止，LNG冷能空分系统对LNG冷能利用只有两种方式，一种直接以LNG气化冷能与进塔净化空气换热，另外一种是通过LNG-氮换热，采用氮循环制冷。
CN101532768A、CN201387202Y介绍了一种利用液化天然气冷能的空分系统。该系统的特点是：设有LNG—氮换热器和氮—氮换热器，以压力氮气作为封闭循环介质。氮气作为循环介质，氮潜热值较小、所需压缩量大、耗能较高，存在氮气的温位与LNG冷能利用温度存在不匹配的现象。
CN101943512A描述了一种利用液化天然气冷能的空分方法。该方法的特点是：将低温 低压的氮气进行压缩形成压力氮气，其在换热的过程中压力损失较大，需要多个压缩机，这对于循环管路和管道设备的运行压力提出了较高的要求。该方法没有考虑氮气与LNG换热所存在的泄漏问题，LNG泄漏会进入压力管道进行循环，引起严重的安全问题。
CN101033909A公开了一种获得液氧和液氮的空气分离系统。该系统的特点是：配有低压、中压、高压的三级氮气压缩机。其对于循环介质氮气的压缩和利用的工序繁琐、运行和维护成本高，没有给出具体的运行标准。
CN202675796U公开了利用LNG冷能生产液体空分产品的装置。该装置的特点是：其氮—氮换热器中液氮的压力低于氮气侧压力，保证空分装置的安全性。但该换热器需要与不同压力的氮气介质接口进行连接，对于设备运行压力提出了较高要求。
根据甲烷物性，LNG常压气化，其沸点-162℃，该温度所对应N 2的压力为1.6MPa，即只有将氮气压到1.6MPa以上才能直接利用LNG冷能，N 2循环压力高能耗大。另外为降低空分能耗，提高分离效率，空分塔需要在较低压力下操作，一般不超过1.0MPa。以N 2为取冷循环介质的LNG空分效率较低。对于以LNG气化冷能直接预冷进塔空气流程，LNG效率更低，并且不安全。无论何种流程，目前LNG冷能空分对LNG冷能利用率在15％－20％，大量LNG冷能被浪费。因此，如何有效提高LNG冷能利用率是目前需要解决的技术问题。
发明内容
本发明所要解决的技术问题是针对现有技术的不足，提供一种基于氩循环的LNG冷能利用系统及方法。本发明基于氩循环的LNG冷能利用系统采用LNG-氩气换热器，以氩气为工质通过热泵回收LNG冷能，利用氩气焦耳-汤姆逊效应提高冷能品位后传递被冷却介质，可以有效提高LNG冷能利用率，使LNG冷能利用率提高到90％以上，更好的实现绿色环保理念。
为解决上述问题，本发明采用如下技术方案：
一种基于氩循环的LNG冷能利用系统，所述基于氩循环的LNG冷能利用系统包括天然气冷能回收系统、氩循环系统和冷能利用系统；所述天然气冷能回收系统包括LNG-氩气换热器；所述氩循环系统包括由液氩管道、循环氩节流膨胀阀、循环氩换热器、氩气管道、循环氩气压缩机和LNG-氩气换热器组成的串联回路；所述冷能利用系统中的被冷却介质与循环氩换热器中的放热管路连接，用于与循环氩换热器回热管路中的氩换热，实现LNG冷能交换过程。
进一步地，所述天然气冷能回收系统还包括LNG进料管、NG(天然气)压缩机、NG冷却器和NG用户管道；所述NG冷却器包括NG放热管和冷却水回热管；所述LNG进料管、 LNG-氩气换热器的回热管路、NG压缩机、NG放热管和NG用户管道依次相连组成串联通路，所述冷却水回热管与冷却水循环系统连通；
所述循环氩换热器包括循环氩-氮气换热器，所述循环氩-氮气换热器的入口与循环氩节流膨胀阀出口相连，循环氩-氮气换热器的出口与循环氩气压缩机的入口相连；
所述冷能利用系统包括氮气冷却系统，所述氮气冷却系统包括气氮进口管道和液氮出口管道，气氮进口管道与循环氩-氮气换热器放热管路的输入端连接，液氮出口管道与循环氩-氮气换热器放热管路的输出端连接。
进一步地，所述循环氩换热器还包括循环氩-空气换热器，所述循环氩-氮气换热器的入口与循环氩节流膨胀阀出口相连，所述循环氩-氮气换热器的出口与循环氩-空气换热器的入口相连，所述循环氩-空气换热器的出口与循环氩气压缩机的入口相连；
所述冷能利用系统还包括净化空气冷却系统，所述净化空气冷却系统包括净化空气进口管道和冷空气出口管道，所述净化空气进口管道与循环氩-空气换热器放热管路的输入端连接，冷空气出口管道与循环氩-空气换热器放热管路的输出端连接。
进一步地，所述冷能利用系统还包括空分系统，所述冷空气出口管道的出口端与空分系统的空气入口端相连，使冷空气进入空分系统进行分离，分离出的气氮通过气氮进口管道进入循环氩-氮气换热器内换热。
进一步地，所述液氮出口管道分为两路，一路连接产品液氮储槽，另一路连接空分系统内分馏上塔的回流口。
本发明的基于氩循环的LNG冷能利用系统，以氩气为工质通过热泵回收LNG冷能，利用氩气焦耳-汤姆逊效应提高冷能品位后传递给氮气，用于深冷法空气分离，空气深冷分离得到氮气(或液氮)氧气(或液氧)及氩气(或液氩)系统的冷能由LNG气化产生。
本发明还提供了基于上述氩循环的LNG冷能利用系统的冷能利用方法，包括以下步骤：将LNG在LNG-氩气换热器内与氩气换热，LNG气化，氩气冷凝，形成液氩，然后通过液氩管路进入节流膨胀阀进行降温，再进入循环氩换热器，在循环氩换热器与被冷却介质实现热交换后成为气态氩气，随后进入氩气压缩机加压，再重新进入LNG-氩气换热器冷凝吸收LNG冷能，循环往复，实现LNG冷能交换过程。
进一步地，LNG在LNG-氩气换热器中的气化压力为0.1MPa—1.0MPa，对应的温度为：-162℃—-124℃。
进一步地，氩气经循环氩气压缩机后压力范围为0.7MPa—4.8MPa，对应的温度为：-162℃—-122℃。
进一步地，循环氩经过节流膨胀后压力为0.1MPa—1.6MPa，温度为-186℃—-148℃。优 选压力范围为0.1MPa—0.7MPa，温度为-186℃—-163℃。
进一步地，所述被冷却介质包括氮气，所述循环氩换热器包括循环氩-氮气换热器，在循环氩-氮气换热器中，氮气压力为0.1MPa—3.4MPa，温度为-186℃—-147℃。优选压力范围为0.1MPa—1.5MPa，温度为-186℃—-163℃。
进一步地，所述被冷却介质还包括净化空气，所述循环氩换热器还包括循环氩-空气换热器，其对应的冷却过程为：LNG进料管通过管路与LNG-氩气换热器进行连接，在LNG-氩气换热器内LNG气化，氩气冷凝，LNG将冷能交换给循环氩气。释放冷能后的NG进入NG压缩机及NG冷却器进行压缩和冷却，按用户需要的压力通过管道输送至各用户处；在LNG-氩气换热器内获得LNG低温冷能形成的液氩，通过管路进入节流膨胀阀通过焦耳-汤姆逊效应进行降温，然后进入循环氩-氮气换热器，在循环氩-氮气换热器中液氩气化，氮气冷凝，液氩将高品位冷能传给气态氮气。出循环氩-氮气换热器的气态氩气则通过管路连接进入循环氩-空气换热器，进一步回收循环氩冷能，然后进入氩气压缩机加压，再重新进入LNG-氩气换热器冷凝吸收LNG冷能，循环往复。通过这一过程将LNG冷能提高品位后传递给空分系统；
进一步地，来自空分系统的气氮(GN 2)进入循环氩-氮气换热器吸收液氩冷能后冷凝为液氮(LN 2)，LN 2再回到空分系统，部分用于回流，其余作为产品；经过净化的空气经循环氩-空气换热器，吸收循环氩气冷能后进入空分塔进行分离；循环冷却水经过NG冷却器，对压缩后的NG进行降温，然后回到循环冷却水系统。
有益效果
(1)氩气的临界温度及相同压力下沸点均高于氮气，介于氮气和甲烷之间。以氩作为循环介质，解决了LNG-氮气直接换热对氮气压力的苛刻要求。相对于氮循环，氩循环可在较宽的LNG气化压力范围内回收LNG冷能，并且循环氩制冷的压缩比比氮循环低，从而节省压缩机功耗，实现LNG冷能利用效率最大化；
(2)通过循环氩制冷，可以将LNG冷能由常压下的-162℃提高到-184℃以上，提高了冷能品位，该高品位冷能可直接用于低压空分系统，提高空分精馏塔分离效率，降低空分系统的投资额；
(3)氩气潜热比氮气高，相比一般LNG冷能空分系统中的氮气循环，氩气循环的气量少，能耗低；
(4)采用氩气循环，可避免LNG与空气介质直接换热，防止天然气泄漏进空分系统引起的安全问题，使整个系统更安全。
附图说明
图1为本发明基于氩循环的LNG冷能利用系统；
图2为本发明带有空分系统的基于氩循环的LNG冷能利用系统；
其中，1-LNG进料管、2-LNG-氩气换热器、3-NG压缩机、4-NG冷却器、401-冷却水进口管、402-冷却水出口管、5-NG用户管道、6-循环氩节流膨胀阀、601-液氩管道、7-循环氩-氮气换热器、701-GN 2进口管道、702-LN 2出口管道、8-循环氩-空气换热器、801-净化空气进口管道、802-冷空气出口管道、9-循环氩气压缩机、901-氩气管道、10-空分塔、1001-空分塔氮产品出口管道、1002-空分塔污氮出口管道、1003-空分塔氧产品出口管道。
具体实施方式
下面结合具体实施方式，进一步阐述本发明。应理解，这些实施例仅用于说明本发明而不用于限制本发明的范围。此外应理解，在阅读了本发明讲授的内容之后，本领域技术人员可以对本发明作各种改动或修改，这些等价形式同样落于本申请所附权利要求书所限定的范围。
实施例1
图1是基于氩循环的LNG冷能利用系统，包括天然气冷能回收系统、氩循环系统和冷能利用系统；天然气冷能回收系统包括LNG-氩气换热器2；氩循环系统包括由液氩管道601、循环氩节流膨胀阀6、循环氩换热器、氩气管道901、循环氩气压缩机9和LNG-氩气换热器2组成的串联回路；冷能利用系统中的被冷却介质与循环氩换热器中的放热管路连接，用于与循环氩换热器回热管路中的氩换热，实现LNG冷能交换过程。
进一步地，天然气冷能回收系统还包括LNG进料管1、NG压缩机3、NG冷却器4和NG用户管道5；NG冷却器4包括NG放热管和冷却水回热管；LNG进料管、LNG-氩气换热器2的回热管路、NG压缩机3、NG放热管和NG用户管道5依次相连组成串联通路，冷却水回热管分别通过冷却水进口管401、冷却水出口管402与冷却水循环系统连通；本申请中的LNG指的液化天然气，NG指代的是天然气。
进一步地，循环氩换热器包括循环氩-氮气换热器7和循环氩-空气换热器8，循环氩-氮气换热器7的入口与循环氩节流膨胀阀6出口相连，循环氩-氮气换热器7的出口与循环氩-空气换热器8的入口相连，循环氩-空气换热器8的出口与循环氩气压缩机9的入口相连；冷能利用系统包括氮气冷却系统，氮气冷却系统包括气氮进口管道701和液氮出口管道702，气氮进口管道701与循环氩-氮气换热器7放热管路的输入端连接，液氮出口管道702与循环氩-氮气换热器7放热管路的输出端连接。
冷能利用系统还包括净化空气冷却系统，净化空气冷却系统包括净化空气进口管道801和冷空气出口管道802，净化空气进口管道801与循环氩-空气换热器8放热管路的输入端连接，冷空气出口管道802与循环氩-空气换热器8放热管路的输出端连接。
进一步地，为图2所示的带有空分系统的基于氩循环的LNG冷能利用系统；冷能利用系统还包括空分系统，冷空气出口管道802的出口端与空分系统中的空分塔10的空气入口端相连，使冷空气进入空分系统中空分，进行精馏分离，在空分塔10中，塔顶氮气通过管道701进入冷凝器7冷凝成液氮，然后通过液氮回流管道702回到空分塔，分为两路，一路连接产品液氮储槽，通过空分塔氮产品出口管道1001成为氮气产品，另一路连接空分系统内分馏上塔的回流口对空分塔进行冷却后，空分塔的污氮通过空分塔污氮出口管道1002排出，最后在空分塔塔底通过空分塔氧产品出口管道取得氧产品1003。本发明的空分系统与现有技术相同。
本发明的基于氩循环的LNG冷能利用系统的工作原理如下：LNG冷能释放系统，LNG通过进料管1进入LNG-氩气换热器2，在LNG-氩气换热器2内LNG气化，氩气冷凝，LNG将冷能交换给循环氩气。释放冷能后的NG进入NG压缩机3压缩至用户要求压力，再进入NG冷却器4进行冷却降温，然后通过NG用户管道5送至用户处。NG冷却器4采用循环冷却水进行取热，循环冷却水通过冷却水进水口及出水口与循环水处理系统连接；循环氩制冷系统，循环氩气在LNG-氩气换热器2内获得LNG低温冷能形成液氩，通过液氩管道601进入节流膨胀阀6通过焦耳-汤姆逊效应进行降温，然后进入循环氩-氮气换热器7，在此换热器中液氩气化，氮气冷凝，液氩将高品位冷能传给液氮。出循环氩-氮气换热器7的低温气氩则通过管路连接进入循环氩-空气换热器8，在此将净化空气冷却，进一步回收循环氩冷能，复热后的氩气通过氩气管道901进入压缩机9加压，再重新进入LNG-氩气换热器2降温、冷凝吸收LNG冷能，循环往复，即可将LNG冷能提高品位后传递给空分系统；氮气冷凝及空气预冷系统，来自空分系统的GN 2通过管道701进入循环氩-氮气换热器7吸收液氩冷能后冷凝为LN 2，LN 2通过管道702再回到空分系统；经过净化的空气经净化空气进口管道801进入循环氩-空气换热器，进一步吸收循环氩气冷能后通过冷空气出口管道802进入空分塔进行精馏分离，在空分塔10中，塔顶氮气通过GN 2进口管道701进入冷凝器7冷凝成液氮，然后通过液氮出口管道702回到空分塔，部分作为回流其余为氮气产品，空分塔的污氮通过管道排出，在空分塔塔底取得氧产品。
实施例2
本发明的基于氩循环的LNG冷能利用系统的冷能利用方法，采用实施1的LNG冷能利用系统，具体如下：LNG常压(0.1MPa)气化：LNG通过进料管进入LNG-氩气换热器，在 此进行常压气化，温度为-162℃，气化后再进一步与气氩换热，释放冷能后复热的NG进入NG压缩机压缩至用户要求压力，再经NG冷却器用循环冷却水降温后通过管道送至用户处。来自循环氩压缩机的氩气，压力为0.8MPa，在LNG-氩气换热器中经过与LNG换热，取得LNG冷能冷凝为-160℃的液氩，经过管路进入节流膨胀阀通过焦耳-汤姆逊效应进行降温后，在循环氩-氮气换热器内将液氩冷能传给液氮。循环氩经过节流膨胀阀后的压力取决于空分塔的操作压力。若空分塔操作压力为0.35MPa，则其塔顶氮温-182℃，则循环氩经过节流膨胀阀后的压力可取为0.15MPa，对应的循环氩气化温度为-184℃，从而实现了将LNG冷能提高品位(使温度更低)后向空分系统的传递。
对比例1
作为对比，LNG常压气化若采用其它专利的氮循环方法，则需要将氮气压缩至1.7MPa以上，才能吸收常压LNG的气化冷能。本专利的氩循环方式，氩气压缩压力只需至0.8MPa即可，并且因为氩气化潜热比氮气大，氩气循环量相对小，实现了LNG冷能的高效利用。
实施例3
本发明的基于氩循环的LNG冷能利用系统的冷能利用方法，采用实施1的LNG冷能利用系统，具体如下：LNG气化压力0.3MPa:压力为0.3MPa的LNG通过进料管进入LNG-氩气换热器，在此进行气化，温度为-146℃，经与循环氩换热，释放冷能复热后进入NG压缩机压缩至用户要求压力，再经NG冷却器用循环冷却水降温后通过管道送至用户处。来自循环氩压缩机的氩气，压力为1.9MPa，在LNG-氩气换热器中经过与LNG换热，取得LNG冷能冷凝为-144℃的液氩，经过管路进入节流膨胀阀通过焦耳-汤姆逊效应进行降温后，在循环氩-氮气换热器内将液氩冷能传给液氮，循环氩经过节流膨胀阀后的压力取决于空分塔的操作压力。若空分塔操作压力为0.8MPa，则其塔顶氮温-172℃，则循环氩经过节流膨胀阀后的压力可取为0.3MPa，对应的循环氩气化温度为-174℃，从而实现了将LNG冷能提高品位(使温度更低)后向空分系统的传递。
对比例2
作为对比，压力0.3MPa的LNG气化温度-146℃，已接近氮气临界点(压力3.35MPa，温度-147℃)，采用其它专利的氮循环方法已不可能回收LNG冷能。本专利的氩循环方式，可以在压力0.1MPa—1.0MPa范围内对LNG气化冷能(对应温度-162℃—-124℃)进行回收，在较宽的低温范围内实现LNG冷能的高效利用。
实施例4
本发明的基于氩循环的LNG冷能利用系统的冷能利用方法，采用实施1的LNG冷能利用系统，具体如下：LNG气化压力1.0MPa:压力为1.0MPa的LNG通过进料管进入LNG-氩气换热器，在此进行气化，温度为-124℃，经与循环氩换热，释放冷能复热后进入NG压缩机压缩至用户要求压力，再经NG冷却器用循环冷却水降温后通过管道送至用户处。来自循环氩压缩机的氩气，压力为4.8MPa，在LNG-氩气换热器中经过与LNG换热，取得LNG冷能冷凝为-123℃的液氩，经过管路进入节流膨胀阀通过焦耳-汤姆逊效应进行降温后，在循环氩-氮气换热器内将液氩冷能传给液氮，循环氩经过节流膨胀阀后的压力取决于空分塔的操作压力。若空分塔操作压力为1.5MPa，则其塔顶氮温-162℃，则循环氩经过节流膨胀阀后的压力可取为0.6MPa，对应的循环氩气化温度为-164℃，从而实现了将LNG冷能提高品位(使温度更低)后向空分系统的传递。
本发明公开和提出的方法，本领域技术人员可通过借鉴本文内容，适当改变条件路线等环节实现，尽管本发明的方法和制备技术已通过较佳实施例子进行了描述，相关技术人员明显能在不脱离本发明内容、精神和范围内对本文所述的方法和技术路线进行改动或重新组合，来实现最终的制备技术。特别需要指出的是，所有相类似的替换和改动对本领域技术人员来说是显而易见的，他们都被视为包括在本发明精神、范围和内容中。

Claims (10)

  1. 一种基于氩循环的LNG冷能利用系统，其特征在于：所述基于氩循环的LNG冷能利用系统包括天然气冷能回收系统、氩循环系统和冷能利用系统；所述天然气冷能回收系统包括LNG-氩气换热器；所述氩循环系统包括由液氩管道、循环氩节流膨胀阀、循环氩换热器、氩气管道、循环氩气压缩机和LNG-氩气换热器组成的串联回路；所述冷能利用系统中的被冷却介质与循环氩换热器中的放热管路连接，用于与循环氩换热器回热管路中的氩换热，实现LNG冷能交换过程。
  2. 根据权利要求1所述的一种基于氩循环的LNG冷能利用系统，其特征在于：所述天然气冷能回收系统还包括LNG进料管、NG压缩机、NG冷却器和NG用户管道；所述NG冷却器包括NG放热管和冷却水回热管；所述LNG进料管、LNG-氩气换热器的回热管路、NG压缩机、NG放热管和NG用户管道依次相连组成串联通路，所述冷却水回热管与冷却水循环系统连通；
    所述循环氩换热器包括循环氩-氮气换热器，所述循环氩-氮气换热器的入口与循环氩节流膨胀阀出口相连，循环氩-氮气换热器的出口与循环氩气压缩机的入口相连；
    所述冷能利用系统包括氮气冷却系统，所述氮气冷却系统包括气氮进口管道和液氮出口管道，气氮进口管道与循环氩-氮气换热器放热管路的输入端连接，液氮出口管道与循环氩-氮气换热器放热管路的输出端连接。
  3. 根据权利要求2所述的一种基于氩循环的LNG冷能利用系统，其特征在于：所述循环氩换热器还包括循环氩-空气换热器，所述循环氩-氮气换热器的入口与循环氩节流膨胀阀出口相连，所述循环氩-氮气换热器的出口与循环氩-空气换热器的入口相连，所述循环氩-空气换热器的出口与循环氩气压缩机的入口相连；
    所述冷能利用系统还包括净化空气冷却系统，所述净化空气冷却系统包括净化空气进口管道和冷空气出口管道，所述净化空气进口管道与循环氩-空气换热器放热管路的输入端连接，冷空气出口管道与循环氩-空气换热器放热管路的输出端连接。
  4. 根据权利要求3所述的一种基于氩循环的LNG冷能利用系统，其特征在于：所述冷能利用系统还包括空分系统，所述冷空气出口管道的出口端与空分系统的空气入口端相连，使冷空气进入空分系统进行分离，分离出的气氮通过气氮进口管道进入循环氩-氮气换热器内换热。
  5. 根据权利要求4所述的一种基于氩循环的LNG冷能利用系统，其特征在于：所述液氮出口管道分为两路，一路连接产品液氮储槽，另一路连接空分系统内分馏上塔的回流口。
  6. 根据权利要求1-5任一所述的基于氩循环的LNG冷能利用系统的冷能利用方法，其特征在于，包括以下步骤：将LNG在LNG-氩气换热器内与氩气换热，LNG气化，氩气冷凝， 形成液氩，然后通过液氩管路进入节流膨胀阀进行降温，再进入循环氩换热器，在循环氩换热器与被冷却介质实现热交换后成为气态氩气，随后进入氩气压缩机加压，再重新进入LNG-氩气换热器冷凝吸收LNG冷能，循环往复，实现LNG冷能交换过程。
  7. 根据权利要求6所述的基于氩循环的LNG冷能利用系统的冷能利用方法，其特征在于，LNG在LNG-氩气换热器中的气化压力为0.1MPa—1.0MPa，对应的温度为：-162℃—-124℃。
  8. 根据权利要求6所述的基于氩循环的LNG冷能利用系统的冷能利用方法，其特征在于，氩气经循环氩气压缩机后压力范围为0.7MPa—4.8MPa，对应的温度为：-162℃—-122℃。
  9. 根据权利要求6所述的基于氩循环的LNG冷能利用系统的冷能利用方法，其特征在于，循环氩经过节流膨胀后压力为0.1MPa—1.6MPa，温度为-186℃—-148℃。
  10. 根据权利要求6所述的基于氩循环的LNG冷能利用系统的冷能利用方法，其特征在于，所述被冷却介质包括氮气，所述循环氩换热器包括循环氩-氮气换热器，在循环氩-氮气换热器中，氮气压力为0.1MPa—3.4MPa，温度为-186℃—-147℃。
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