CN217357804U - Cryogenic rectification helium extraction device for liquefied natural gas flash gas - Google Patents

Cryogenic rectification helium extraction device for liquefied natural gas flash gas Download PDF

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CN217357804U
CN217357804U CN202221242436.8U CN202221242436U CN217357804U CN 217357804 U CN217357804 U CN 217357804U CN 202221242436 U CN202221242436 U CN 202221242436U CN 217357804 U CN217357804 U CN 217357804U
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channel
heat exchanger
inlet
outlet
helium
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高婷
张菲
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Nisa Shanghai Energy Technology Co ltd
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Nisa Shanghai Energy Technology Co ltd
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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
    • F25J3/0228—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
    • F25J3/02—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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
    • 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
    • F25J2200/40—Features relating to the provision of boil-up in the bottom of a 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the 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
    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/08—Cold compressor, i.e. suction of the gas at cryogenic temperature and generally without afterstage-cooler
    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/30—Compression of the feed stream
    • 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
    • F25J2270/04—Internal refrigeration with work-producing gas expansion loop
    • 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
    • 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
    • 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
    • F25J2270/902—Details about the refrigeration cycle used, e.g. composition of refrigerant, arrangement of compressors or cascade, make up sources, use of reflux exchangers etc.

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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 utility model discloses a liquefied natural gas flash distillation gas cryogenic rectification carries helium device, the device mainly include precooling heat exchanger, liquefaction heat exchanger, cryrogenic heat exchanger, demethanization rectifying column and denitrogenation rectifying column, and two rectifying column are inside to be provided with reboiler and condenser respectively. The utility model discloses a two tower ultra-low temperature rectification and reasonable matching utilize cold, heat, have realized extracting high-purity helium from liquefied natural gas flash distillation gas with lower energy consumption, and not only the helium rate of recovery can reach 99.9%, and the nitrogen content of helium product gas can drop to 1% in addition, and follow-up catalytic dehydrogenation and the load of absorption denitrogenation refined helium that has significantly reduced have saved the cost and the degree of difficulty for follow-up helium is refined.

Description

Liquefied natural gas flash evaporation gas cryogenic rectification helium extraction device
Technical Field
The utility model relates to a liquefied natural gas field especially relates to the device that draws helium from liquefied natural gas flash distillation gas.
Background
Helium is a colorless, odorless noble gas, is also known to have the lowest boiling point, and has the properties of being difficult to liquefy, good stability, strong diffusivity, low solubility, and the like. The helium has wide application, can be used in the fields of medical scientific research, aerospace military industry and the like, and is an important scarce strategic resource which cannot be replaced and is related to the national security and the development of high and new technology industries.
The helium-containing natural gas mainly comprises a gas reservoir from a natural gas field, a gas reservoir of an oil and gas field, natural gas in the oil and gas reservoir, natural gas in an oil reservoir and the like. China is a poor helium country, the content of helium in natural gas is very low (about 0.04-0.1%), the cost for directly extracting helium is extremely high, and most helium depends on imports. Therefore, the helium is extracted from the natural gas, so that the helium resource of China can be guaranteed, and the comprehensive utilization efficiency of the natural gas and the economic benefit of a liquefied natural gas plant can be improved.
In the process of Liquefied Natural Gas (LNG) production, the last stage throttle valve generates a large amount of flash gas (BOG) in the throttling process. The flash gas mainly comprises gas entering the LNG storage tank from the LNG cold box, gas generated by throttling and pressure reduction, and part of gas gasified by heat leakage of the LNG storage tank, and is a gas phase discharged from the top of the LNG storage tank. The flash evaporation gas contains helium, hydrogen, nitrogen and methane. Under normal pressure, the liquefaction temperatures of helium, hydrogen, nitrogen and methane are-269 ℃, 253 ℃, 196 ℃ and-162 ℃ respectively; under the pressure of the storage tank, helium, hydrogen and part of nitrogen are volatilized from LNG, and at the moment, compared with the raw material natural gas, the difficulty and the cost for extracting helium from BOG are relatively low because gases such as hydrocarbons are liquefied and non-condensable gases such as helium can be enriched at one time. In addition, the removal of helium is also very beneficial to the liquefied natural gas process, the phenomenon of liquid rolling vaporization caused by the density difference of LNG in the large LNG storage tank can be greatly reduced, and the large-scale emission of BOG tail gas and the safety accidents of the large LNG storage tank are avoided.
At present, the helium is extracted from natural gas by a condensation method. The condensation method generally adopts a cryogenic separation process or a cryogenic separation and pressure swing adsorption process. Because the normal pressure boiling points of the hydrogen and the helium are-252.6 ℃ and-268.9 ℃ respectively, the process medium needs to be cooled to an extremely low temperature by adopting a cryogenic separation method, a circulating refrigeration system is needed for maintaining the cold quantity balance of the cold box, and the energy consumption cost is very huge. Particularly, in small and medium-sized plants, helium of liquefied natural gas belongs to non-condensable gas, and when part of BOG circulates to a natural gas raw material inlet of an LNG plant, the non-condensable gas is increased and gathered, the heat exchange efficiency is influenced, the liquefaction amount of the natural gas is reduced, the productivity of the LNG plant is partially influenced, the LNG recovery rate is reduced, the BOG gas amount is increased, and the operation fluctuation of a BOG compressor is increased. For example, chinese patent application publication No. CN111692837A discloses a "system for co-producing helium gas using an LNG production apparatus", in which a part of BOG is subjected to helium extraction, another part of BOG is subjected to helium gas enrichment, and a raw material gas from the LNG production apparatus is sequentially subjected to compression, dehydrogenation, dehydration drying, temperature reduction condensation, and low temperature adsorption separation to obtain helium gas. The method for separating nitrogen from helium by partial condensation in the low-temperature section has limited separation effect and low helium recovery rate and purity; in addition, the low-temperature section refrigeration of the system is provided by negative-pressure liquid nitrogen, and the equipment and operation cost is high.
At present, a rectification method is also adopted to extract helium from flash evaporation gas. For example, chinese patent application publication No. CN107228526A discloses a "helium extraction, denitrification, and reliquefaction apparatus for LNG flash gas", which performs rectification separation at a higher temperature (about-190 ℃), first denitrogenates, then demethanizes, and finally obtains a crude helium product containing more nitrogen (more than 20%) and hydrogen, which increases the load and difficulty of subsequent catalytic dehydrogenation and adsorption denitrification.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model is to provide a liquefied natural gas flash distillation gas low temperature rectification carries helium device, its simple structure, the energy consumption is low, can obtain the helium product of higher purity.
In order to solve the technical problem, the cryogenic rectification helium extraction device for liquefied natural gas flash evaporation gas mainly comprises a precooling heat exchanger, a liquefying heat exchanger, a cryogenic heat exchanger, a demethanizing rectifying tower and a denitrification rectifying tower; wherein:
the pre-cooling heat exchanger at least comprises A, B, C channels, the liquefaction heat exchanger at least comprises F, G, H channels, and the cryogenic heat exchanger at least comprises L, M channels;
an inlet of the channel A of the precooling heat exchanger is connected with an air inlet pipeline of the raw material flash evaporation gas;
a reboiler and a condenser are arranged in the demethanizing rectifying tower; the inlet of the reboiler of the demethanizer-rectifier is connected with the outlet of the channel A, and the outlet of the reboiler of the demethanizer-rectifier is connected with the inlet of the channel F of the liquefaction heat exchanger; the outlet of the F channel is connected with the inlet of the demethanizer rectification tower; the bottom liquid phase outlet of the demethanizer-rectifying tower is connected with the inlet of the condenser of the demethanizer-rectifying tower; an outlet of a condenser of the demethanizer-rectifying tower is connected with an inlet of a G channel of the liquefaction heat exchanger, an outlet of the G channel is connected with an inlet of a B channel of the precooling heat exchanger, and an outlet of the B channel is connected with a natural gas exhaust pipeline with methane content reaching 95%; a top gas phase outlet of the demethanizing rectifying tower is connected with an inlet of an L channel of the cryogenic heat exchanger, and an outlet of the L channel is connected with an inlet of the denitrification rectifying tower;
a reboiler and a condenser are arranged in the denitrification rectifying tower; the bottom liquid phase exit linkage of denitrogenation rectifying column the entry of M passageway of cryrogenic heat exchanger, the exit linkage of M passageway the entry of the H passageway of liquefaction heat exchanger, the exit linkage of H passageway the entry of the C passageway of precooling heat exchanger, the vent pipe line of the exit linkage tail gas of C passageway.
Further, a compressor can be arranged on the gas inlet line of the raw material flash evaporation gas.
Further, throttle valves may be respectively disposed on the bottom liquid phase outlet pipelines of the demethanizer-rectifier and the denitrogenation-rectifier.
Further, the pre-cooling heat exchanger may further include a channel D, the liquefaction heat exchanger may further include a channel I, and the cryogenic heat exchanger may further include a channel N; an outlet of a reboiler of the denitrification rectifying tower is connected with an inlet of a condenser of the denitrification rectifying tower, and an expander is arranged on a pipeline between the outlet of the reboiler of the denitrification rectifying tower and the inlet of the condenser of the denitrification rectifying tower; the outlet of the condenser of the denitrification rectifying tower is connected with the inlet of the N channel of the cryogenic heat exchanger; the outlet of the N channel is connected with the inlet of the I channel of the liquefaction heat exchanger; an outlet of the channel I is connected with an inlet of a channel D of the precooling heat exchanger, and a pipeline between the outlet of the channel I and the inlet of the channel D is provided with a compressor; and the outlet of the channel D is connected with the inlet of a reboiler of the denitrification rectifying tower.
Further, the pre-cooling heat exchanger may further include a channel E, the liquefaction heat exchanger may further include J, K two channels, and the cryogenic heat exchanger may further include O, P two channels; the top gas phase outlet of the denitrification rectifying tower is connected with the inlet of the O channel of the cryogenic heat exchanger; the outlet of the O channel is connected with the inlet of the J channel of the liquefaction heat exchanger; an outlet of the J channel is connected with an inlet of a P channel of the cryogenic heat exchanger, and an expander is arranged on a pipeline between the outlet of the J channel and the inlet of the P channel; the outlet of the P channel is connected with the inlet of the K channel of the liquefaction heat exchanger; the outlet of the K channel is connected with the inlet of the E channel of the precooling heat exchanger; and the outlet of the E channel is connected with a helium product gas discharge pipeline.
The utility model also discloses a liquefied natural gas flash distillation gas cryogenic rectification carries helium method, this method flow is simple, and the helium rate of recovery is high.
According to the method for extracting helium from the liquefied natural gas flash gas through cryogenic rectification, methane in the flash gas is removed through cryogenic rectification, and nitrogen in the flash gas is removed through cryogenic rectification, so that a helium product containing only hydrogen (if any) and about 1% of nitrogen is obtained.
The temperature of rectification demethanization is preferably-160 ℃ to-150 ℃; the temperature of the rectification denitrification is not lower than-210 ℃, and is preferably-210 ℃ to-200 ℃.
Preferably, the cold energy required by the rectification demethanization can be provided by the latent heat generated after throttling refrigeration of high-pressure (15-30 bar) liquefied methane.
Preferably, the helium obtained by rectification can be subjected to heat exchange and expansion refrigeration in sequence, then heat exchange is carried out again to normal temperature and normal pressure, and the helium product is obtained after the refrigeration capacity is fully utilized and discharged.
Preferably, the cold energy required by the rectification denitrification can be provided by gas refrigerant expansion cycle refrigeration. The gaseous refrigerant is preferably pure helium.
The utility model discloses a two towers ultra-low temperature rectification take off methane earlier, denitrogenation gas again, and reasonable matching utilizes cold, heat simultaneously, has realized extracting high-purity helium from liquefied natural gas flash distillation gas with lower energy consumption. Compared with the prior art of helium extraction, the utility model discloses a liquefied natural gas flash distillation gas cryogenic rectification carries helium device and carries helium method has following advantage and beneficial effect:
1. the external helium expansion refrigeration provides the cold energy of a condenser of a low-temperature section rectifying tower (a denitrogenation rectifying tower), and nitrogen and partial hydrogen can be separated as far as possible at the temperature of-210 ℃ to-200 ℃, so that the high recovery rate of helium and the low nitrogen content of a crude helium product (the recovery rate of helium can be as high as 99.9%, and the nitrogen content of crude helium can be reduced to about 1%) are ensured, the load of preparing refined helium by subsequent catalytic dehydrogenation and adsorption denitrification is greatly reduced, and the cost and the difficulty are saved for subsequent helium refining;
2. the utility model recovers helium, and simultaneously recovers natural gas with 95 percent of methane content, and the methane recovery rate can reach 99 percent; in addition, the cold volume of demethanization rectifying column condenser is provided by the low temperature latent heat that produces behind this tower bottom high pressure liquefied methane throttle refrigeration, has saved outside refrigeration energy consumption greatly, has reduced the overall energy consumption (the utility model discloses a total energy consumption of carrying the helium device is about 4kWh/Nm 3 Helium) simplifies the helium extraction process.
Drawings
Fig. 1 is a schematic diagram of a cryogenic rectification helium extraction device and a process for liquefied natural gas flash gas according to an embodiment of the present invention.
The reference numerals in the figures are illustrated as follows:
1. 14: compressor with a compressor housing having a plurality of compressor blades
2: precooling heat exchanger
3: liquefied heat exchanger
4: demethanization rectifying tower
5. 9: reboiler device
6. 10: condenser
7: cryogenic heat exchanger
8: denitrification rectifying tower
11. 12: throttle valve
13. 15: expansion machine
16-46: pipeline
A to P: channel
Detailed Description
In order to understand the technical contents, characteristics and functions of the present invention more specifically, the technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the cryogenic rectification helium extraction apparatus for flash evaporation gas of liquefied natural gas of this embodiment mainly includes 3 heat exchangers, 2 rectification columns, 2 compressors, 2 expanders, and 2 JT throttle valves. Wherein:
the pre-cooling heat exchanger 2 at least comprises five channels A-E. The liquefaction heat exchanger 3 at least comprises six channels from F to K. The cryogenic heat exchanger 7 at least comprises five passages from L to P.
Channel a of pre-cooling heat exchanger 2 is arranged at the bottom of pre-cooling heat exchanger 2, the inlet of channel a being connected to line 17. Line 17 is connected to the outlet of compressor 1 and the inlet of compressor 1 is connected to feed gas (i.e. natural gas flash) inlet line 16 and compressor 1 is used to compress the feed gas.
The demethanizer rectification column 4 is used for removing methane in the flash gas by low-temperature rectification. The reboiler 5 is arranged inside the tower bottom of the demethanization rectifying tower 4, and the condenser 6 is arranged inside the tower top. The inlet of reboiler 5 is connected to the outlet of channel a of pre-cooling heat exchanger 2 via line 18; the outlet of the reboiler 5 is connected to the inlet of the bottom pass F of the liquefaction heat exchanger 3 via line 19. The outlet of passage F of the liquefaction heat exchanger 3 is connected to the middle inlet of the demethanizer rectification column 4 via line 20. The bottom liquid phase outlet of demethanizer rectification column 4 is connected to the inlet of throttle valve 11 via line 21. The outlet of the throttle valve 11 is connected to the inlet of the condenser 6 via line 22. The outlet of condenser 6 is connected via line 23 to the inlet of channel G of liquefaction heat exchanger 3, and the outlet of channel G of liquefaction heat exchanger 3 is connected via line 24 to the inlet of channel B of pre-cooling heat exchanger 2. The outlet of channel B of pre-cooling heat exchanger 2 is connected to line 25 for discharging nitrogen-containing natural gas based on methane. The gas phase outlet at the top of demethanizer rectifier 4 is connected to the inlet of the bottom pass L of cryogenic heat exchanger 7 via line 26.
The outlet of the bottom channel L of the cryogenic heat exchanger 7 is connected with the middle inlet of the denitrification rectifying tower 8 through a pipeline 27.
The denitrification rectifying tower 8 is used for removing nitrogen in the flash evaporation gas by low-temperature rectification. The inside at the bottom of denitrogenation rectifying column 8 is provided with reboiler 9, and the inside condenser 10 that is provided with at the top of the tower. The inlet of reboiler 9 is connected to the outlet of channel D of pre-cooling heat exchanger 2 via line 41. The outlet of reboiler 9 is connected to the inlet of expander 15 via line 42. The outlet of the expander 15 is connected to the inlet of the condenser 10 via line 43. The outlet of condenser 10 is connected to the inlet of channel N of cryogenic heat exchanger 7 by line 44. The bottom liquid phase outlet of the denitrification rectification column 8 is connected with the inlet of the throttle valve 12 through a pipeline 28, and the outlet of the throttle valve 12 is connected with the inlet of the channel M of the cryogenic heat exchanger 7 through a pipeline 29. The top gas phase outlet of the denitrification rectifying tower 8 is connected with the inlet of the channel O of the cryogenic heat exchanger 7 through a pipeline 33.
The outlets of the channel M, the channel N, the channel O and the channel P of the cryogenic heat exchanger 7 are respectively connected with the inlets of the channel H, the channel I, the channel J and the channel K of the liquefaction heat exchanger 3 through a pipeline 30, a pipeline 45, a pipeline 34 and a pipeline 37. Outlets of the passage H and the passage K of the liquefaction heat exchanger 3 are connected to inlets of the passage C and the passage E of the precooling heat exchanger 2 through a line 31 and a line 38, respectively. And the channel C and the channel E of the precooling heat exchanger 2 are respectively connected with a pipeline 32 for discharging tail gas and a pipeline 39 for discharging crude helium products. The outlet of channel I of the liquefaction heat exchanger 3 is connected to the inlet of the compressor 14 by means of a line 46. The outlet of compressor 14 is connected to the inlet of channel D of pre-cooling heat exchanger 2 by line 40. The outlet of passage J of the liquefaction heat exchanger 3 is connected to the inlet of the expander 13 via a line 35. The outlet of expander 13 is connected to the inlet of pass P at the top of cryogenic heat exchanger 7 by line 36.
The pre-cooling heat exchanger 2, the liquefaction heat exchanger 3 and the cryogenic heat exchanger 7 are tube-wound heat exchangers, and in other embodiments, other types of heat exchangers, such as plate-fin heat exchangers, may also be used.
The demethanizer/rectifier 4 and the denitrogenation/rectifier 8 may be packed or plate towers. The reboiler 5 and the condenser 6 in the demethanizer-rectifier 4 and the reboiler 9 and the condenser 10 in the denitrogenating-rectifier 8 may be assembled to the rectifier or may be provided separately from the rectifier.
The following is a detailed description of a method for extracting helium from liquefied natural gas flash gas by using the flash gas cryogenic rectification helium extraction device.
The raw material gas, i.e. flash evaporation gas (BOG), is compressed to 20-30 barg by a compressor 1 and cooled to normal temperature, sequentially cooling to-110 to-130 ℃ through a precooling heat exchanger 2, a reboiler 5 at the bottom of a demethanizer rectifying tower 4 and a liquefying heat exchanger 3 to form a gas-liquid two phase, then entering the demethanizer rectifying tower 4 through a pipeline 20, the nitrogen-containing natural gas with about 95 percent of methane content is obtained at the bottom of the tower through low-temperature rectification (the rectification temperature is minus 160 ℃ to minus 150 ℃) in a demethanizer rectification tower 4 and leaves the demethanizer rectification tower 4 through a pipeline 21, the low temperature close to the boiling point of methane of-160 ℃ to-155 ℃ is obtained after throttling and pressure reduction to the normal pressure through the throttle valve 11, the cold energy is sequentially provided for the condenser 6, the liquefaction heat exchanger 3 and the precooling heat exchanger 2 at the top of the demethanizer rectifying tower 4, the temperature is restored to the normal temperature, the cold energy is discharged through a pipeline 25, and the cold energy can be subsequently returned to an inlet of an LNG device for recycling or used as fuel gas of the whole device for balancing.
The gas at the top of the demethanization rectifying tower 4 enters a cryogenic heat exchanger 7 through a pipeline 26, is further cooled to about minus 190 ℃ to form a gas-liquid two phase (helium, liquid nitrogen and hydrogen) and enters a denitrification rectifying tower 8, the gas is subjected to low-temperature rectification (the rectification temperature is minus 205 ℃ to minus 210 ℃) in the denitrification rectifying tower 8, the liquid phase (the liquid nitrogen containing about 10% of methane) leaves the denitrification rectifying tower 8 through a pipeline 28, the low temperature of about minus 190 ℃ is obtained after throttling and pressure reduction through a throttle valve 12, cold energy is sequentially provided for the cryogenic heat exchanger 7, the liquefaction heat exchanger 3 and the precooling heat exchanger 2, the gas is reheated to the normal temperature and is discharged from 32, and the gas can be subsequently discharged as purge gas for combustion or used as a torch purge gas of a natural gas liquefaction device so as to save the fuel gas consumption of the whole device.
The gas at the top of the denitrogenation rectifying tower 8 is a crude helium product, the temperature of a condenser 10 of the denitrogenation rectifying tower 8 is controlled to be not lower than-210 ℃ (in the embodiment, the temperature is-205 ℃ to-210 ℃), nitrogen in the crude helium can be condensed into liquid nitrogen, meanwhile, the nitrogen is prevented from freezing, and therefore the nitrogen in the helium can be removed to about 1%. Most of the crude helium on the top of the denitrification rectifying tower 8 leaves the denitrification rectifying tower 8 through a pipeline 33, sequentially provides cold energy for the cryogenic heat exchanger 7 and the liquefied heat exchanger 3, the temperature is restored to minus 90 ℃ to minus 80 ℃, then the crude helium is expanded to a lower pressure through the expansion machine 13, the temperature is again lowered to minus 190 ℃ to minus 180 ℃, the crude helium returns to the cryogenic heat exchanger 7, the liquefied heat exchanger 3 and the precooling heat exchanger 2 again, the cold energy is fully utilized, finally, the crude helium product (the components are helium 79%, hydrogen 20% and nitrogen 1%) at normal temperature and normal pressure is discharged from a pipeline 39, and the crude helium product can be further subjected to catalytic dehydrogenation and deoxynitrogen adsorption to prepare high-purity helium.
The cold energy required by the low temperature (the specific condensing temperature is determined by the composition of the raw material gas and the purity of the helium gas to be obtained) of about-210 ℃ to-200 ℃ provided by the condenser 10 of the denitrification rectifying tower 8 can be provided by a refrigerant, namely closed helium gas expansion circulation refrigeration from the outside of the device. The helium from the pipeline 46 is compressed to an intermediate pressure (15-25 kg) by the compressor 14 and is cooled to normal temperature, and then is sequentially cooled to-150 ℃ to-140 ℃ by the precooling heat exchanger 2 and the reboiler 9 of the denitrification rectifying tower 8 (the helium refrigerant provides heat for the reboiler 9 of the denitrification rectifying tower 8 to enable the temperature to reach a lower temperature of about-150 ℃ to-130 ℃ before expansion, so that a lower refrigeration temperature can be provided), and enters the expander 15 from the pipeline 42 to expand to near normal pressure and reach a low temperature below-210 ℃, so that cold energy is sequentially provided for the condenser 10, the cryogenic heat exchanger 7 and the liquefaction heat exchanger 3 of the denitrification rectifying tower 8, and finally low-temperature compression is carried out at a temperature of-80 ℃ to-70 ℃ (the refrigerant is compressed at a lower temperature, so that the energy consumption of the compressor can be saved).
The above-mentioned embodiments are only possible or preferred embodiments of the present invention, and are not intended to limit the scope of the invention, so that the present invention shall not be limited to the above-mentioned embodiments.

Claims (5)

1. The liquefied natural gas flash evaporation gas cryogenic rectification helium extraction device is characterized by comprising a precooling heat exchanger, a liquefying heat exchanger, a cryogenic heat exchanger, a demethanizing rectifying tower and a denitrification rectifying tower; wherein:
the pre-cooling heat exchanger at least comprises A, B, C channels, the liquefaction heat exchanger at least comprises F, G, H channels, and the cryogenic heat exchanger at least comprises L, M channels;
an inlet of the channel A of the precooling heat exchanger is connected with an air inlet pipeline of the raw material flash evaporation gas;
a reboiler and a condenser are arranged in the demethanizing rectifying tower; the inlet of the reboiler of the demethanizer-rectifier is connected with the outlet of the channel A, and the outlet of the reboiler of the demethanizer-rectifier is connected with the inlet of the channel F of the liquefaction heat exchanger; the outlet of the F channel is connected with the inlet of the demethanizer rectification tower; the bottom liquid phase outlet of the demethanizer-rectifying tower is connected with the inlet of the condenser of the demethanizer-rectifying tower; an outlet of a condenser of the demethanizer rectification tower is connected with an inlet of a channel G of the liquefaction heat exchanger, an outlet of the channel G is connected with an inlet of a channel B of the precooling heat exchanger, and an outlet of the channel B is connected with a natural gas exhaust pipeline; a top gas phase outlet of the demethanizing rectifying tower is connected with an inlet of an L channel of the cryogenic heat exchanger, and an outlet of the L channel is connected with an inlet of the denitrification rectifying tower;
a reboiler and a condenser are arranged in the denitrification rectifying tower; the bottom liquid phase exit linkage of denitrogenation rectifying column the entry of M passageway of cryrogenic heat exchanger, the exit linkage of M passageway the entry of the H passageway of liquefaction heat exchanger, the exit linkage of H passageway the entry of the C passageway of precooling heat exchanger, the vent pipe line of the exit linkage tail gas of C passageway.
2. The apparatus according to claim 1, wherein a compressor is arranged on the gas inlet line of the raw material flash evaporation gas.
3. The apparatus of claim 1, wherein the bottom liquid phase outlet pipelines of the demethanizer-rectifier and the denitrogenator-rectifier are respectively provided with a throttle valve.
4. The apparatus of claim 1, wherein said pre-cooling heat exchanger further comprises channel D, said liquefaction heat exchanger further comprises channel I, and said cryogenic heat exchanger further comprises channel N; an outlet of a reboiler of the denitrification rectifying tower is connected with an inlet of a condenser of the denitrification rectifying tower, and an expander is arranged on a pipeline between the outlet of the reboiler of the denitrification rectifying tower and the inlet of the condenser of the denitrification rectifying tower; the outlet of the condenser of the denitrification rectifying tower is connected with the inlet of the N channel of the cryogenic heat exchanger; the outlet of the N channel is connected with the inlet of the I channel of the liquefaction heat exchanger; an outlet of the channel I is connected with an inlet of a channel D of the precooling heat exchanger, and a pipeline between the outlet of the channel I and the inlet of the channel D is provided with a compressor; and the outlet of the channel D is connected with the inlet of a reboiler of the denitrification rectifying tower.
5. The apparatus of claim 1, wherein said pre-cooling heat exchanger further comprises channel E, said liquefaction heat exchanger further comprises J, K two channels, and said cryogenic heat exchanger further comprises O, P two channels; the top gas phase outlet of the denitrification rectifying tower is connected with the inlet of the O channel of the cryogenic heat exchanger; the outlet of the O channel is connected with the inlet of the J channel of the liquefaction heat exchanger; an outlet of the J channel is connected with an inlet of a P channel of the cryogenic heat exchanger, and an expander is arranged on a pipeline between the outlet of the J channel and the inlet of the P channel; the outlet of the P channel is connected with the inlet of the K channel of the liquefaction heat exchanger; the outlet of the K channel is connected with the inlet of the E channel of the precooling heat exchanger; and the outlet of the E channel is connected with a helium product gas discharge pipeline.
CN202221242436.8U 2022-05-23 2022-05-23 Cryogenic rectification helium extraction device for liquefied natural gas flash gas Active CN217357804U (en)

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