CN108036585B - Heat pump air separation system for LNG cold energy utilization - Google Patents

Heat pump air separation system for LNG cold energy utilization Download PDF

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Publication number
CN108036585B
CN108036585B CN201810013002.2A CN201810013002A CN108036585B CN 108036585 B CN108036585 B CN 108036585B CN 201810013002 A CN201810013002 A CN 201810013002A CN 108036585 B CN108036585 B CN 108036585B
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nitrogen
air
passage
liquid
inlet
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CN108036585A (en
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董学智
许剑
赵洪雷
陈仕卿
高庆
张华良
谭春青
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Institute of Engineering Thermophysics of CAS
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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
    • F25J3/04406—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 dual pressure main column system
    • F25J3/04424—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 dual pressure main column system without thermally coupled high and low pressure columns, i.e. a so-called split columns
    • 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
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • 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
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04012—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling
    • F25J3/0403—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling 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
    • F25J3/04—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
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04048—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams
    • F25J3/0406—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams 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
    • F25J3/04—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
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • F25J3/0426—The cryogenic component does not participate in the fractionation
    • F25J3/04266—The cryogenic component does not participate in the fractionation and being liquefied hydrocarbons
    • 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
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/04872—Vertical layout of cold equipments within in the cold box, e.g. columns, heat exchangers etc.
    • F25J3/04878—Side by side arrangement of multiple vessels in a main column system, wherein the vessels are normally mounted one upon the other or forming different sections of the same column
    • 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
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/04872—Vertical layout of cold equipments within in the cold box, e.g. columns, heat exchangers etc.
    • F25J3/04884—Arrangement of reboiler-condensers
    • 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
    • F25J2215/42—Nitrogen or special cases, e.g. multiple or low purity N2
    • 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
    • F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

The invention discloses a heat pump air separation system for utilizing LNG cold energy, which adopts LNG cold energy to cool raw material low-pressure air and utilizes a heat pump rectification mode to perform air separation, and compared with the traditional air separation system, the heat pump rectification system is adopted to only pressurize part of nitrogen in the raw material air to about 0.56MPa, so that the total power consumption of compression parts in the air separation system is reduced; the LNG is adopted to cool raw material air in the main heat exchanger, part of cold energy can be converted into separation work of oxygen and nitrogen, liquid oxygen products do not need to absorb heat and release cold through the main heat exchanger, and the liquid preparation device can be omitted; the LNG is adopted to cool the raw material air, so that the starting time of the air separation system can be greatly reduced; because the pressure is reduced, the equipment cost of the rectifying tower is greatly reduced compared with that of the traditional air separation system, the equipment investment of the nitrogen booster is lower than that of the traditional air compressor system, and the rectifying tower is not different from the traditional air separation system, so that the total system investment is reduced.

Description

Heat pump air separation system for LNG cold energy utilization
Technical Field
The invention belongs to the field of air separation, and relates to a heat pump air separation system, in particular to a heat pump air separation system for utilizing LNG cold energy.
Background
Air separation systems have important roles in the fields of steel, chemical, semiconductor, food processing, and medical. The low-temperature rectification air separation system is a main scheme for realizing large-scale preparation of high-purity nitrogen, oxygen and argon. The low temperature rectification air separation system consumes a great deal of energy, especially in the process of preparing products of liquid oxygen and liquid nitrogen. Liquefied Natural Gas (LNG) is a low-temperature (about 111K) mixed liquid obtained by liquefying natural gas by cryogenic process, and its main component is methane (CH) 4 ) Has the advantages of high combustion heat value, small pollution of emissions, low storage and transportation cost, and the like. LNG cold energy is huge in quantity and high in energy level, and common application mainly comprises direct power generation, air liquefaction and separation, liquefied dry ice preparation, cryogenic crushing, low-temperature refrigeration houses and the like. Taking into account space division systemsThe process temperature is about 78-100K, which is lower than the temperature of LNG, so that the condition of low-temperature cold energy high-temperature use can be avoided, and the efficient utilization principle of 'temperature opposite-mouth and cascade utilization' energy is met, so that the cold energy utilization scheme is also considered as the most reasonable utilization mode in the prior art.
The energy-saving effect of the existing LNG cold energy utilization air separation system can be mainly classified into the following two factors: (1) The temperature of the working medium at the inlet of the LNG cold energy cooling air compressor or the nitrogen compressor can reduce the requirement of an air system on electric power energy consumption; (2) LNG cold energy can replace the high-purity liquid oxygen/liquid nitrogen cold energy released by the main heat exchanger to reduce the temperature of raw material air, and the power energy consumption required by extra low-temperature liquid product cold energy preparation is reduced. Compared with a conventional air separation system, the air separation system adopting LNG cold energy can reduce the energy consumption for preparing unit liquid products by about 50 percent through the calculation of related documents and patents.
However, the operation pressure of the rectifying tower of the prior air separation system scheme for utilizing LNG cold energy is close to 0.6MPa, and the addition of cold energy only reduces the energy consumption for producing liquid products without any beneficial influence on the separation work of the air separation system. There are 2 main reasons for this: (1) The rectification units of the traditional air separation system all adopt double-stage rectification towers, the reflux gas-liquid of the upper tower and the lower tower is realized through the heat exchange of low-pressure liquid oxygen and high-pressure nitrogen, and the boiling point of the nitrogen is far lower than that of oxygen under the same pressure, so that the lower rectification tower needs to operate at high pressure; (2) The working temperature of the two-stage rectifying tower is 78-100K, the storage temperature of LNG is 112K, if LNG cold energy acts on the rectifying process, raw material air still needs to be pressurized, and lower working temperature is generated through expansion or throttling. The method for adjusting the two reasons only reduces the pressure of the rectifying tower by changing the traditional two-stage rectifying cold-hot coupling mode, converts partial LNG cold energy into separation work, and further reduces the energy consumption of the air separation system for utilizing the LNG cold energy.
Disclosure of Invention
Aiming at the defects and shortcomings of the prior art, the invention aims to provide a heat pump air separation system for utilizing LNG cold energy, which adopts the LNG cold energy to cool raw material low-pressure air and utilizes a heat pump rectification mode to perform air separation, thereby reducing the total power consumption of a compression part in an air separation system, reducing the starting time of the air separation system and reducing the total investment cost of the system.
The invention adopts the technical proposal for solving the technical problems that:
the heat pump air separation system for utilizing LNG cold energy comprises an air compressor, a water cooling tower, a molecular sieve, a main heat exchanger, a subcooler I, a rectifying tower, a subcooler II, a stripping tower, a booster, a condensation evaporator, an LNG storage device, a cryogenic pump and a liquid oxygen storage device, and is characterized in that,
the main heat exchanger comprises an air passage, an LNG passage, a nitrogen passage and a polluted nitrogen passage; the subcooler I comprises an air passage, a nitrogen passage I, a polluted nitrogen passage and a nitrogen passage II; the rectifying towers are provided with tower plates in a staggered manner in the height direction, the bottoms of the rectifying towers are provided with air inlets and liquid air outlets, and the tops of the rectifying towers are provided with liquid nitrogen inlets and nitrogen outlets; the subcooler II comprises a liquid air passage, a nitrogen passage, a polluted nitrogen passage and a liquid nitrogen passage; the stripping tower is provided with tower plates in a staggered manner in the height direction, the bottom is provided with a liquid oxygen outlet I, a liquid oxygen outlet II and a liquid oxygen inlet, the upper part is provided with a liquid air inlet, a liquid nitrogen inlet, a pure nitrogen outlet and a polluted nitrogen outlet, wherein,
the outlet of the LNG storage device is communicated with the LNG passage of the main heat exchanger through a pipeline by the cryopump; the air inlet of the air compressor is communicated with the outside air, and the air outlet of the air compressor is communicated with the air inlet at the bottom of the rectifying tower through a pipeline sequentially through the water cooling tower, the molecular sieve, the air passage of the main heat exchanger and the air passage of the subcooler I; the liquid air outlet at the bottom of the rectifying tower is communicated with the liquid air inlet at the upper part of the stripping tower through a liquid air passage of the subcooler II by a pipeline, and the nitrogen outlet at the top of the rectifying tower is communicated with the liquid nitrogen side inlet of the condensing evaporator through a nitrogen passage II of the supercharger and the subcooler I in sequence by a pipeline; the liquid nitrogen side outlet of the condensing evaporator is divided into two paths, one path is communicated with a liquid nitrogen inlet at the top of the rectifying tower, and the other path is communicated with a liquid nitrogen inlet at the upper part of the stripping tower through a liquid nitrogen passage of the subcooler II; the liquid oxygen side inlet of the condensing evaporator is communicated with a liquid oxygen outlet I at the bottom of the stripping tower, and the liquid oxygen side outlet of the condensing evaporator is communicated with a liquid oxygen inlet at the bottom of the stripping tower; the liquid oxygen outlet II at the bottom of the stripping tower is communicated with the inlet of the liquid oxygen storage device through a pipeline; the pure nitrogen outlet at the upper part of the stripping tower is communicated with the nitrogen passage of the subcooler II, the nitrogen passage I of the subcooler I and the inlet of the nitrogen passage of the main heat exchanger in sequence through pipelines, and the dirty nitrogen outlet at the upper part of the stripping tower is communicated with the dirty nitrogen passage of the subcooler II, the dirty nitrogen passage of the subcooler I and the inlet of the dirty nitrogen passage of the main heat exchanger in sequence through pipelines.
Preferably, the outlet of the nitrogen passage of the main heat exchanger is in communication with the inlet of a nitrogen storage or utilization device.
Preferably, the outlet of the dirty nitrogen passage of the main heat exchanger is in communication with an air cooling system of the molecular sieve.
Preferably, a control valve is arranged at the liquid nitrogen inlet at the top of the rectifying tower.
Preferably, the liquid air inlet and the liquid nitrogen inlet at the upper part of the stripping tower are respectively provided with a control valve.
Preferably, the outlet pressure of the air compressor is about 0.2 MPa.
Preferably, the high-purity nitrogen led out from the top of the rectifying tower is pressurized to about 0.56MPa by the pressurizer.
Preferably, the air after passing through the main heat exchanger and the subcooler I is cooled to a temperature near the bubble point and fed to the bottom of the rectifying column.
The invention relates to a heat pump air separation system for utilizing LNG cold energy, which mainly adopts LNG cold energy to cool raw material low-pressure air and utilizes a heat pump rectification mode to perform air separation, and the specific working process is as follows:
the air is firstly boosted to 0.2MPa by an air compressor and cooled by a water cooling tower, the boosted pressure is used for compensating the pressure loss in the molecular sieve, the main heat exchanger, the subcooler I, the rectifying tower and the stripping tower, and the air cooled by the water cooling tower enters the molecular sieve to remove the impurities such as water, carbon dioxide and the like; the pressurized normal temperature air purified by the molecular sieve enters a main heat exchanger and is cooled to a temperature close to the bubble point by LNG, reflux nitrogen and dirty nitrogen, and is sent to the bottom of a rectifying tower, rising air and reflux liquid nitrogen injected from the top are repeatedly condensed and evaporated on tower plates which are arranged in a staggered manner in the height direction in the rectifying tower, so that oxygen-enriched liquid air with higher oxygen concentration is concentrated at the bottom of the rectifying tower, and high-purity nitrogen is concentrated at the top of the rectifying tower; the oxygen-enriched liquid air pumped out from the bottom of the rectifying tower passes through a cooler II and enters the upper part of the rectifying tower to carry out the oxygen stripping process; the high-purity nitrogen led out from the upper part of the rectifying tower is pressurized to about 0.56MPa by a pressurizer, then cooled by a cooler I, enters a condensing evaporator for condensation, returns to the tops of the rectifying tower and the stripping tower as reflux liquid, absorbs heat in the condensing evaporator for evaporation and returns to the stripping tower; the liquid oxygen at the bottom of the stripping tower is directly output as a product, pure nitrogen at the top of the stripping tower is rewuped by a cooler II and a main heat exchanger and then is output as a nitrogen product, and polluted nitrogen is rewuped by the cooler II and the main heat exchanger and then is sent to a molecular sieve purification system and an air cooling system.
Compared with the prior art, the heat pump air separation system for LNG cold energy utilization has the remarkable technical effects that: (1) Compared with the traditional air separation system, the invention adopts the heat pump rectification system to only pressurize part of nitrogen in the raw material air to about 0.56MPa, thereby reducing the total power consumption of the compression part in the air separation system; (2) The LNG is adopted to cool raw material air in the main heat exchanger, part of cold energy can be converted into separation work of oxygen and nitrogen, liquid oxygen products do not need to absorb heat and release cold through the main heat exchanger, and the liquid preparation device can be omitted; (3) The LNG is adopted to cool the raw material air, so that the starting time of the air separation system can be greatly reduced; (4) In the invention, because the pressure is reduced, the equipment cost of the rectifying tower is greatly reduced compared with that of the traditional air separation system, the equipment investment of the nitrogen booster is lower than that of the traditional air compressor system, and the stripping tower is not different from the traditional air separation system, so the total system investment is reduced.
Drawings
Fig. 1 is a schematic diagram of a heat pump air separation system for LNG cold energy utilization according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below by referring to the accompanying drawings and examples. It should be noted that the following description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereby.
As shown in fig. 1, the heat pump air separation system for LNG cold energy utilization of the present invention comprises an air compressor 1, a water cooling tower 2, a molecular sieve 3, a main heat exchanger 4, a subcooler i 5, a rectifying tower 6, a subcooler ii 7, a stripping tower 8, a supercharger 9, a condensing evaporator 10, an LNG storage device 11, a cryopump 12, and a liquid oxygen storage device 13. Wherein the main heat exchanger 4 comprises an air passage, an LNG passage, a nitrogen passage and a polluted nitrogen passage; the subcooler I5 comprises an air passage, a nitrogen passage I, a polluted nitrogen passage and a nitrogen passage II; the rectifying tower 6 is provided with tower plates in a staggered manner in the height direction, the bottom is provided with an air inlet and a liquid air outlet, and the top is provided with a liquid nitrogen inlet and a nitrogen outlet; the subcooler II 7 comprises a liquid air passage, a nitrogen passage, a polluted nitrogen passage and a liquid nitrogen passage; the stripping tower 8 is provided with tower plates which are staggered in the height direction, a liquid oxygen outlet I, a liquid oxygen outlet II and a liquid oxygen inlet are arranged at the bottom, and a liquid air inlet, a liquid nitrogen inlet, a pure nitrogen outlet and a polluted nitrogen outlet are arranged at the upper part.
The outlet of the LNG storage 11 is connected to the LNG path of the main heat exchanger 4 via a pipeline through a cryopump 12. The air inlet of the air compressor 1 is communicated with air, and the air outlet of the air compressor 1 is communicated with the air inlet at the bottom of the rectifying tower 6 through a pipeline sequentially through the water cooling tower 2, the molecular sieve 3, the air passage of the main heat exchanger 4 and the air passage of the subcooler I5; the liquid air outlet at the bottom of the rectifying tower 6 is communicated with the liquid air inlet arranged at the upper part of the stripping tower 8 through a liquid air passage of a subcooler II 7, the nitrogen outlet at the top of the rectifying tower 6 is communicated with the liquid nitrogen side inlet of a condensing evaporator 10 through a pipeline sequentially through a booster 9 and a nitrogen passage II of a subcooler I5, the liquid nitrogen side outlet of the condensing evaporator 10 is divided into two paths, one path is communicated with the liquid nitrogen inlet at the top of the rectifying tower 6, and the other path is communicated with the liquid nitrogen inlet at the upper part of the stripping tower 8 through a liquid nitrogen passage of the subcooler II 7; the liquid oxygen side inlet of the condensation evaporator 10 is communicated with a liquid oxygen outlet I at the bottom of the stripping tower 8, and the liquid oxygen side outlet of the condensation evaporator 10 is communicated with a liquid oxygen inlet at the bottom of the stripping tower 8; the liquid oxygen outlet II at the bottom of the stripping tower 8 is communicated with the inlet of the liquid oxygen storage device 13 through a pipeline; the pure nitrogen outlet at the upper part of the stripping tower 8 is communicated with the inlet of a nitrogen storage device (not shown in the figure) through a pipeline sequentially passing through the nitrogen passage of the subcooler II 7, the nitrogen passage I of the subcooler I5 and the nitrogen passage of the main heat exchanger 4, and the dirty nitrogen outlet at the upper part of the stripping tower 8 is communicated with the air cooling system of the molecular sieve 3 through a pipeline sequentially passing through the dirty nitrogen passage of the subcooler II 7, the dirty nitrogen passage of the subcooler I5 and the dirty nitrogen passage of the main heat exchanger 4.
The invention relates to a heat pump air separation system for utilizing LNG cold energy, which mainly adopts LNG cold energy to cool raw material low-pressure air and utilizes a heat pump rectification mode to perform air separation, and the specific working process is as follows:
the air is firstly boosted to 0.2MPa by an air compressor 1 and is cooled by a water cooling tower 2, the boosted pressure is used for compensating the pressure loss in a molecular sieve 3, a main heat exchanger 4, a subcooler I5, a rectifying tower 6 and a stripping tower 7, and the air cooled by the water cooling tower 2 enters the molecular sieve 3 to remove impurities such as moisture, carbon dioxide and the like; the pressurized normal temperature air purified by the molecular sieve 3 enters the main heat exchanger 4 and is cooled to be close to the bubble point temperature by LNG, reflux nitrogen and dirty nitrogen, and is sent to the bottom of the rectifying tower 5, rising air and reflux liquid nitrogen injected from the top are repeatedly condensed and evaporated on tower plates which are arranged in a staggered manner in the height direction in the rectifying tower 6, so that oxygen-enriched liquid air with higher oxygen concentration is concentrated at the bottom of the rectifying tower 6, and high-purity nitrogen is concentrated at the top of the rectifying tower 6; oxygen-enriched liquid air pumped out from the bottom of the rectifying tower 6 passes through a cooler II 7 and enters the upper part of the stripping tower 8 to carry out an oxygen stripping process; the high-purity nitrogen led out from the upper part of the rectifying tower 6 is pressurized to about 0.56MPa by a pressurizer 9, then cooled by a cooler I5, enters a condensing evaporator 10 for condensation, returns to the tops of the rectifying tower 5 and the stripping tower 8 to be used as reflux liquid, and liquid oxygen generated at the bottom of the stripping tower 8 absorbs heat in the condensing evaporator 10 for evaporation and returns to the stripping tower 8; the liquid oxygen at the bottom of the stripping tower 8 is directly output as a product, pure nitrogen at the top of the stripping tower 8 is output as a nitrogen product after being rewuped by the cooler II 7 and the main heat exchanger 4, and polluted nitrogen is sent to the molecular sieve 3 purification system and the air cooling system after being rewuped by the cooler II 7 and the main heat exchanger 4.
Further, a control valve is arranged at the liquid nitrogen inlet at the top of the rectifying tower 6, and a control valve is arranged at the liquid air inlet and the liquid nitrogen inlet at the upper part of the stripping tower 8.
Compared with the traditional air separation system, the invention adopts the heat pump rectification system to only pressurize part of nitrogen in the raw material air to about 0.56MPa, thereby reducing the total power consumption of the compression part in the air separation system; the air compressor 1 is adopted to boost the raw material air in advance, and then the raw material air enters the molecular sieve 3 to remove impurities, so that the problem of icing generated by heat exchange between the raw material air and LNG, nitrogen and dirty nitrogen in the main heat exchanger 4 can be solved; the LNG is adopted to cool raw material air in the main heat exchanger 4, partial cold energy can be converted into oxygen-nitrogen separation work, the liquid oxygen product does not need to absorb heat through the main heat exchanger to release cold, and the liquid preparation device can be omitted.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (4)

1. The heat pump air separation system for utilizing LNG cold energy comprises an air compressor, a water cooling tower, a molecular sieve, a main heat exchanger, a subcooler I, a rectifying tower, a subcooler II, a stripping tower, a booster, a condensation evaporator, an LNG storage device, a cryogenic pump and a liquid oxygen storage device, and is characterized in that,
the main heat exchanger comprises an air passage, an LNG passage, a nitrogen passage and a polluted nitrogen passage;
the subcooler I comprises an air passage, a nitrogen passage I, a polluted nitrogen passage and a nitrogen passage II;
the rectifying towers are provided with tower plates in a staggered manner in the height direction, the bottoms of the rectifying towers are provided with air inlets and liquid air outlets, and the tops of the rectifying towers are provided with liquid nitrogen inlets and nitrogen outlets;
the subcooler II comprises a liquid air passage, a nitrogen passage, a polluted nitrogen passage and a liquid nitrogen passage;
the stripping tower is provided with tower plates in a staggered manner in the height direction, the bottom is provided with a liquid oxygen outlet I, a liquid oxygen outlet II and a liquid oxygen inlet, the upper part is provided with a liquid air inlet, a liquid nitrogen inlet, a pure nitrogen outlet and a polluted nitrogen outlet,
wherein,
the outlet of the LNG storage device is communicated with the LNG passage of the main heat exchanger through a pipeline by the cryopump;
the air inlet of the air compressor is communicated with the outside air, the air outlet of the air compressor is communicated with the air inlet at the bottom of the rectifying tower through the air passage of the water cooling tower, the molecular sieve, the main heat exchanger and the air passage of the subcooler I in sequence by pipelines, the air subjected to heat exchange by the main heat exchanger and the subcooler I is cooled to be close to the bubble point temperature and is sent to the bottom of the rectifying tower, and the outlet pressure of the air compressor is about 0.2 MPa;
the liquid air outlet at the bottom of the rectifying tower is communicated with the liquid air inlet at the upper part of the stripping tower through a liquid air passage of the subcooler II through a pipeline, the nitrogen outlet at the top of the rectifying tower is communicated with the liquid nitrogen side inlet of the condensing evaporator through a nitrogen passage II of the supercharger and the subcooler I in sequence through a pipeline, and nitrogen led out from the top of the rectifying tower is boosted to about 0.56MPa after passing through the supercharger;
the liquid nitrogen side outlet of the condensing evaporator is divided into two paths, one path is communicated with a liquid nitrogen inlet at the top of the rectifying tower, and the other path is communicated with a liquid nitrogen inlet at the upper part of the stripping tower through a liquid nitrogen passage of the subcooler II; the liquid oxygen side inlet of the condensing evaporator is communicated with a liquid oxygen outlet I at the bottom of the stripping tower, and the liquid oxygen side outlet of the condensing evaporator is communicated with a liquid oxygen inlet at the bottom of the stripping tower; the liquid oxygen outlet II at the bottom of the stripping tower is communicated with the inlet of the liquid oxygen storage device through a pipeline;
the pure nitrogen outlet at the upper part of the stripping tower is communicated with the nitrogen passage of the subcooler II, the nitrogen passage I of the subcooler I and the inlet of the nitrogen passage of the main heat exchanger in sequence through pipelines, and the dirty nitrogen outlet at the upper part of the stripping tower is communicated with the dirty nitrogen passage of the subcooler II, the dirty nitrogen passage of the subcooler I and the inlet of the dirty nitrogen passage of the main heat exchanger in sequence through pipelines;
the outlet of the dirty nitrogen passage of the main heat exchanger is communicated with an air cooling system of the molecular sieve.
2. The LNG cold energy utilizing heat pump air separation system of claim 1, wherein the outlet of the nitrogen passageway of the main heat exchanger is in communication with the inlet of a nitrogen storage or utilization device.
3. The heat pump air separation system for LNG cold energy utilization according to claim 1, wherein a control valve is provided at a liquid nitrogen inlet at the top of the rectifying tower.
4. The heat pump air separation system for LNG cold energy utilization according to claim 1, wherein the liquid air inlet and the liquid nitrogen inlet at the upper portion of the stripping tower are both provided with control valves.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101367509A (en) * 2008-10-10 2009-02-18 上海启元空分技术发展有限公司 Apparatus and method for preparing pressure nitrogen gas with air separation
CN104236254A (en) * 2013-06-06 2014-12-24 龙勇军 Thermally coupled air separation column system
CN106885449A (en) * 2015-12-16 2017-06-23 中国石油天然气集团公司 Using the air-separating technology of cold energy of liquefied natural gas
CN207751221U (en) * 2018-01-07 2018-08-21 中国科学院工程热物理研究所 A kind of heat pump air-seperation system of LNG cold energy uses

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101367509A (en) * 2008-10-10 2009-02-18 上海启元空分技术发展有限公司 Apparatus and method for preparing pressure nitrogen gas with air separation
CN104236254A (en) * 2013-06-06 2014-12-24 龙勇军 Thermally coupled air separation column system
CN106885449A (en) * 2015-12-16 2017-06-23 中国石油天然气集团公司 Using the air-separating technology of cold energy of liquefied natural gas
CN207751221U (en) * 2018-01-07 2018-08-21 中国科学院工程热物理研究所 A kind of heat pump air-seperation system of LNG cold energy uses

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
基于㶲分析的低温热泵空分精馏研究;李健辉;《中国优秀硕士学位论文全文数据库(工程科技Ⅰ辑)》(第03期);第4-9页 *

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