CN112284038B - Mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation and method thereof - Google Patents

Mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation and method thereof Download PDF

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CN112284038B
CN112284038B CN202011077219.3A CN202011077219A CN112284038B CN 112284038 B CN112284038 B CN 112284038B CN 202011077219 A CN202011077219 A CN 202011077219A CN 112284038 B CN112284038 B CN 112284038B
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heat exchanger
main heat
refrigerant
gas
separator
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CN112284038A (en
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章有虎
韦小雄
苟文广
陈环琴
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Hangzhou Zhongtai Cryogenic Technology Corp
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Hangzhou Zhongtai Cryogenic Technology Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
    • F25J3/0219—Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0281—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc. characterised by the type of prime driver, e.g. hot gas expander
    • 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
    • F25B41/00—Fluid-circulation arrangements
    • 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
    • F25B43/00—Arrangements for separating or purifying gases or liquids; Arrangements for vaporising the residuum of liquid refrigerant, e.g. by heat
    • 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
    • F25J3/0242—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 3 carbon atoms 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
    • F25J3/0247—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 4 carbon atoms 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
    • F25J3/0252—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 hydrogen
    • 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
    • F25J3/0295—Start-up or control of the process; Details of the apparatus used, e.g. sieve plates, packings
    • 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
    • F25J5/00—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants
    • 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
    • F25J2200/70—Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • 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
    • F25J2210/12—Refinery or petrochemical off-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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/02—Mixing or blending of fluids to yield a certain product
    • 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
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/60—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being (a mixture of) 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/18—External refrigeration with incorporated cascade 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
    • F25J2270/66—Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of 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
    • 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

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

Abstract

The invention discloses a mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation and a method thereof, wherein the device comprises a mixed refrigerant circulating compressor, a first main heat exchanger, a second main heat exchanger, a reaction product primary separator, a reaction product secondary separator, a liquid product pump, a flash tank, a matched throttling valve and other equipment; the invention replaces the common expansion refrigeration process or cascade refrigeration process in alkane dehydrogenation with the mixed refrigerant refrigeration cycle process with advanced technology, and the product gas meets the high purity requirement, meanwhile, the energy consumption of the device is greatly reduced, the equipment quantity is correspondingly reduced, the investment cost and the operation cost are also greatly reduced, and the economic performance is greatly improved.

Description

Mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation and method thereof
Technical Field
The invention relates to a chemical cryogenic separation system, in particular to a mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation and a method thereof.
Background
The cold box separation device is one of the most critical devices in the alkane dehydrogenation plant, particularly in the working condition of reaction feed gas with low hydrogen content, whether the process technology of the cold box separation device is advanced or not can directly influence the most important product yield and quality in the plant and the energy consumption of the plant, and the cold box separation device with the advanced process technology can bring excellent economic benefits to the plant.
Most of the process technologies in the existing domestic alkane dehydrogenation plants adopt reaction raw material gas with high hydrogen content, the flow of circulating hydrogen in the system accounts for the proportion, and a power generation type turbine expansion machine refrigeration process is used. Wherein, 2 hydrogen expansion units with high price are arranged in the cold box separation system, so that the investment cost is high and the maintenance cost is not low. Although the process technology is widely applied, the power of a feed gas compressor cannot be reduced due to the high hydrogen content of the feed gas, and the process has the defects of large equipment number, complex equipment operation procedures, complex maintenance and operation and the like.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation and a method thereof.
The invention adopts the following specific technical scheme:
a mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation comprises a mixed refrigerant compressor, a first main heat exchanger, a second main heat exchanger, a first separator, a second separator, a flash tank, a rectifying column, a liquid product pump, a first refrigerant separator and a second refrigerant separator;
the pipeline is connected with the first main heat exchanger through a feed gas feed inlet and then connected with the first separator; the top of the first separator passes through the second main heat exchanger through a pipeline and then is connected into the second separator, and a pipeline connected from the bottom of the first separator passes through a throttling valve and then is connected into a flash tank; a pipeline connected to the bottom of the flash tank is connected to the first main heat exchanger through a liquid product pump and is connected out of a liquid product outlet of the first main heat exchanger, and the top of the flash tank is communicated with the rectifying column through a pipeline; a pipeline connected with the top of the second separator is divided into a dry gas product branch and a circulating hydrogen branch; the dry gas product branch passes through the second main heat exchanger and then is connected into the first main heat exchanger and communicated with a dry gas product outlet of the first main heat exchanger; the circulating hydrogen branch passes through the second main heat exchanger and then is connected to the first main heat exchanger and is communicated with the combined feed outlet of the first main heat exchanger; a pipeline connected to the bottom of the second separator is divided into two branches, one branch passes through a throttle valve and then passes through the second main heat exchanger and is connected to the flash tank, and the other branch passes through the throttle valve and then is connected to the rectifying column; the bottom of the rectifying column is connected with the flash tank through a pipeline, and the top of the rectifying column passes through the second main heat exchanger through a pipeline, then is connected into the first main heat exchanger and is connected out of a flash evaporation gas outlet of the first main heat exchanger;
the pipeline is connected with the first main heat exchanger through an alkane feed inlet and is respectively communicated with an upper outlet and a lower outlet which are arranged on the first main heat exchanger; a pipeline connected from the upper outlet is connected into the first main heat exchanger through a throttle valve and communicated with a circulating hydrogen branch positioned in the first main heat exchanger to form a first alkane injection branch; the pipeline connected from the lower outlet is divided into a second alkane injection branch and a third alkane injection branch; the second alkane injection branch is connected into the first main heat exchanger through a throttling valve and communicated with a circulating hydrogen branch in the first main heat exchanger; the third paraffin injection branch is connected with the second main heat exchanger and then is connected out, and is connected with the second main heat exchanger again after passing through the throttle valve and is communicated with a circulating hydrogen branch in the second main heat exchanger;
the pipeline is connected to the first main heat exchanger through the gas-phase refrigerant feeding hole, passes through the second main heat exchanger, then passes through the throttle valve and is communicated with the second refrigerant separator; the top of the second refrigerant separator is connected to a second main heat exchanger through a second refrigerant separation gas path, the bottom of the second refrigerant separator is connected to the second main heat exchanger through a second refrigerant separation liquid path, and the second refrigerant separation gas path and the second refrigerant separation liquid path are communicated in the second main heat exchanger and combined into a second refrigerant separation pipeline; the second refrigerant separation pipeline is connected with the first refrigerant separator after passing through the second main heat exchanger; the pipeline is connected to the first main heat exchanger through the liquid-phase refrigerant feed port, passes through the throttle valve and is connected with the first refrigerant separator;
the top of the first refrigerant separator is connected to a first main heat exchanger through a first refrigerant separation gas path, the bottom of the first refrigerant separator is connected to the first main heat exchanger through a first refrigerant separation liquid path, and the first refrigerant separation gas path and the first refrigerant separation liquid path are communicated in the first main heat exchanger and combined into a first refrigerant separation pipeline; the first refrigerant separation pipeline passes through the first main heat exchanger and then is connected with the mixed refrigerant compressor and is connected into the mixed refrigerant separator; the top of the mixed refrigerant separator is communicated with the gas-phase refrigerant feed port through a pipeline, and the bottom of the mixed refrigerant separator is communicated with the liquid-phase refrigerant feed port through a pipeline.
Preferably, the mixed refrigerant compressor is a centrifugal compressor; the first separator, the second separator, the first refrigerant separator and the second refrigerant separator are all gas-liquid separators.
Preferably, the first main heat exchanger and the second main heat exchanger are both plate-fin heat exchangers; the liquid product pump is a vertical barrel bag pump.
Another object of the present invention is to provide a separation process for dehydrogenating alkane by using any one of the above devices, which comprises the following steps:
the gas-phase refrigerant enters the first main heat exchanger through the gas-phase refrigerant feeding hole and then enters the second main heat exchanger, and both the gas-phase refrigerant and the second main heat exchanger are used for cold exchange; the gas-phase refrigerant flows out of the second main heat exchanger, is reduced in pressure through a throttling valve and enters a second refrigerant separator; gas separated by the second refrigerant separator enters the second main heat exchanger through a second refrigerant separation gas path, separated liquid enters the second main heat exchanger through a second refrigerant separation liquid path, the gas and the liquid are mixed to form a first mixed refrigerant, and cold energy is provided for the second main heat exchanger through reheat evaporation; then the first mixed refrigerant flows out of the second main heat exchanger through a second refrigerant separation pipeline and enters a first refrigerant separator for gas-liquid separation; liquid-phase refrigerant enters the first main heat exchanger through the liquid-phase refrigerant feeding hole, is subjected to pressure reduction through the throttle valve and then enters the first refrigerant separator for gas-liquid separation; gas separated by the first refrigerant separator enters the first main heat exchanger through a first refrigerant separation gas path, separated liquid is connected to the first main heat exchanger through a first refrigerant separation liquid path, the gas and the liquid are mixed to form second mixed refrigerant, and cold energy is provided for the first main heat exchanger through reheat evaporation; then, the second mixed refrigerant flows out of the first main heat exchanger through a first refrigerant separation pipeline, enters a mixed refrigerant compressor for supercharging and cooling, and enters a mixed refrigerant separator; gas separated by the mixed refrigerant separator is injected into the gas-phase refrigerant feed port through a pipeline, and separated liquid is injected into the liquid-phase refrigerant feed port through a pipeline, so that refrigeration cycle of the gas-phase refrigerant and the liquid-phase refrigerant is realized;
feeding the raw material gas into a first main heat exchanger from a raw material gas feeding hole for condensation, and feeding the liquefied raw material gas into a first separator through a pipeline for gas-liquid separation; the gas separated by the first separator enters a second main heat exchanger from a pipeline at the top to be further condensed, and then enters a second separator for gas-liquid separation; the liquid separated by the first separator is depressurized by a throttling valve and then enters a flash tank, the flash liquid of the flash tank enters a first main heat exchanger after being pressurized by a liquid product pump, and flows out from a liquid product outlet of the first main heat exchanger after being subjected to heat exchange and reheating; the flash steam of the flash tank enters a rectifying column through a pipeline at the top, and alkane and olefin components in the flash steam are recovered after washing and rectifying; gas in the rectifying column flows through the second main heat exchanger from a pipeline at the top, enters the first main heat exchanger, and flows out from a flash evaporation gas outlet of the first main heat exchanger after heat exchange and reheating; the gas separated by the second separator flows out along a dry gas product branch and a circulating hydrogen branch at the top respectively; gas flowing out along the dry gas product branch enters the second main heat exchanger and the first main heat exchanger in sequence, and flows out from a dry gas product outlet of the first main heat exchanger after heat exchange and reheating; gas flowing out along the circulating hydrogen branch successively enters the second main heat exchanger and the first main heat exchanger, and flows out from a combined feeding outlet of the first main heat exchanger after heat exchange and reheating; the liquid separated by the second separator is divided into two branches along a bottom pipeline to flow out, the liquid in one branch enters a second main heat exchanger after being subjected to pressure reduction through a throttling valve, enters a flash tank after being subjected to heat exchange and reheating, and the liquid in the other branch enters a rectifying column after being subjected to pressure reduction through the throttling valve; the liquid in the rectification column flows into the flash tank again through a pipeline;
sending alkane from an alkane feeding hole into a first main heat exchanger to be matched with feed gas for dehydrogenation treatment, and then respectively flowing out of an upper outlet and a lower outlet of the first main heat exchanger; alkane flowing along the upper outlet connecting pipeline is subjected to pressure reduction through a throttling valve, enters the first main heat exchanger and is mixed with gas in a circulating hydrogen branch in the first main heat exchanger; alkane circulating along the lower outlet connecting pipeline respectively enters a second alkane injection branch and a third alkane injection branch, and the alkane in the second alkane injection branch enters the first main heat exchanger after being subjected to pressure reduction through the throttle valve and is mixed with gas in the circulating hydrogen branch in the first main heat exchanger; and the alkane in the third alkane injection branch enters the second main heat exchanger to be further cooled, is depressurized through the throttling valve and then reenters the second main heat exchanger, and is mixed with the gas in the circulating hydrogen branch in the first main heat exchanger.
Preferably, the flash steam pressure is in the range of 0.05-0.3 MPag, and the temperature after reheating is 30-47 ℃.
Preferably, the mixed refrigerant compressor has an inlet pressure of 0.1 to 0.5MPag, an outlet pressure of 2.5 to 4MPag, and an inlet temperature of 30 to 47 ℃.
Preferably, the outlet pressure of the liquid product pump is 3-5 MPag, and the reheating temperature before flowing out of the liquid product outlet is 30-47 ℃.
Preferably, the reheating temperature before the dry gas product flows out from the dry gas product outlet and the combined feeding outlet is 30-47 ℃; the pressure at the dry gas product outlet is 0.4-0.8 MPag, and the pressure at the combined feed outlet is 0.1-0.5 MPag.
Preferably, the intake pressure of the raw material gas is 0.8-1.1 MPag, and the temperature is 35-50 ℃.
Preferably, the alkane is fed at a pressure of 1.2-1.8 MPag and at a temperature of 35-50 ℃.
Compared with the prior art, the invention has the following beneficial effects:
aiming at the reaction raw material gas with low hydrogen content, the cold energy is supplemented to the cold box separation device by adopting the mixed refrigerant, and the cold-hot temperature difference curve in the first main heat exchanger and the second main heat exchanger of the cold box separation device is perfected by adjusting the ratio of different components of the mixed refrigerant, so that the excellent heat exchange efficiency of the two multi-strand material flow heat exchangers is finally exerted; meanwhile, the multiple separators in the device adopt efficient gas-liquid separators, so that the size of the equipment can be greatly reduced. Compared with the traditional cold box separation device, the cold box separation device has the advantages that the occupied area of the cold box is reduced, the total energy consumption of the whole device is greatly reduced, the equipment investment is reduced, the operation cost can be greatly reduced, and the olefin product with high cost performance is produced.
Drawings
FIG. 1 is a schematic diagram of the apparatus of the present invention;
in the figure: the system comprises a mixed refrigerant compressor 1, a first main heat exchanger 2, a second main heat exchanger 3, a first separator 4, a second separator 5, a flash tank 6, a rectifying column 7, a liquid product pump 8, a first refrigerant separator 9 and a second refrigerant separator 10.
Detailed Description
The invention will be further elucidated and described with reference to the drawings and the detailed description. The technical features of the embodiments of the present invention can be combined correspondingly without mutual conflict.
As shown in fig. 1, the mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation of the present invention comprises a mixed refrigerant compressor 1, a first main heat exchanger 2, a second main heat exchanger 3, a first separator 4, a second separator 5, a flash tank 6, a rectification column 7, a liquid product pump 8, a first refrigerant separator 9, a second refrigerant separator 10, and regulating valves and pipelines which are matched with each other.
The first main heat exchanger 2 is provided with a raw material gas feed inlet for introducing a raw material gas with low hydrogen content into the first main heat exchanger 2. The pipeline is connected into the first main heat exchanger 2 through a feed gas inlet, and then connected into the first separator 4, so that the first main heat exchanger 2 is communicated with the first separator 4. The top of the first separator 4 is provided with a gas phase outlet and is communicated with the second main heat exchanger 3 through a pipeline, and the second main heat exchanger 3 is communicated with the second separator 5. The bottom of the first separator 4 is provided with a liquid phase outlet, is externally connected with a pipeline provided with a throttle valve, and is communicated with the flash tank 6 after the pressure reduction effect of the throttle valve. The liquid phase outlet is arranged at the bottom of the flash tank 6, is communicated with a liquid product pump 8 after being externally connected with a pipeline, is connected into the first main heat exchanger 2 and is connected out from the liquid product outlet arranged on the first main heat exchanger 2. The top of the flash tank 6 is provided with a gas phase outlet which is communicated with the rectifying column 7 through a pipeline. The top of the second separator 5 is provided with a gas phase outlet, and an external pipeline is divided into a dry gas product branch and a circulating hydrogen branch. Wherein, the dry gas product branch is connected out from the gas phase outlet of the second separator 5, passes through the second main heat exchanger 3 and is connected into the first main heat exchanger 2, and finally is communicated with the dry gas product outlet arranged on the first main heat exchanger 2. And after being connected out from a gas phase outlet of the second separator 5, the circulating hydrogen branch passes through the second main heat exchanger 3 and is connected into the first main heat exchanger 2, and finally is communicated with a combined feeding outlet arranged on the first main heat exchanger 2. The bottom of the second separator 5 is provided with a liquid phase outlet which is communicated with an external pipeline, and the pipeline is divided into two branches. One branch passes through the second main heat exchanger 3 and is connected to the flash tank 6 after passing through the throttling valve, the other branch is connected to the rectifying column 7 after passing through the throttling valve, and the throttling valve arranged on the pipeline is used for throttling and depressurizing fluid in the pipeline. The bottom of the rectifying column 7 is provided with a liquid phase outlet which is externally connected with a pipeline and is connected with the flash tank 6 through the pipeline. The top of the rectifying column 7 is provided with a gas phase outlet which is externally connected with a pipeline, passes through the second main heat exchanger 3 through the pipeline, is connected into the first main heat exchanger 2, and is finally connected out from a flash evaporation gas outlet arranged on the first main heat exchanger 2.
The pipeline is connected to the first main heat exchanger 2 through an alkane feed inlet arranged on the first main heat exchanger 2 and is respectively communicated with an upper outlet and a lower outlet which are arranged on the first main heat exchanger 2. The pipeline connected from the upper outlet is connected to the first main heat exchanger 2 after passing through the throttle valve and is communicated with the circulating hydrogen branch in the first main heat exchanger 2, so that the gases in the two pipelines can be mixed with each other, and the first alkane injection branch is formed jointly. The pipeline connected from the lower outlet is divided into two pipeline passages of a second alkane injection branch and a third alkane injection branch. And a throttle valve is arranged on the second alkane injection branch, and the second alkane injection branch is connected into the first main heat exchanger 2 after passing through the throttle valve and is communicated with a circulating hydrogen branch in the first main heat exchanger 2. The third paraffin injection branch is connected with the second main heat exchanger 3 and then is connected out, and is connected with the second main heat exchanger 3 again through a pipeline provided with a throttle valve and communicated with a circulating hydrogen branch in the second main heat exchanger 3.
The first main heat exchanger 2 is provided with a gas-phase refrigerant feed port, a pipeline is connected into the first main heat exchanger 2 through the gas-phase refrigerant feed port, passes through the second main heat exchanger 3, then passes through the throttle valve, and is communicated with the second refrigerant separator 10. The top of the second refrigerant separator 10 is provided with a gas phase outlet, is externally connected with a second refrigerant separation gas path, and is connected to the second main heat exchanger 3 through the gas path. The bottom of the second refrigerant separator 10 is provided with a liquid phase outlet, is externally connected with a second refrigerant separation liquid path, and is connected to the second main heat exchanger 3 through the liquid path. The second refrigerant separation gas circuit and the second refrigerant separation liquid circuit respectively extend into the second main heat exchanger 3 and then are communicated and combined into one circuit in the second main heat exchanger 3, namely a second refrigerant separation pipeline. The second refrigerant separation pipeline passes through the second main heat exchanger 3 and then is connected with the first refrigerant separator 9. A liquid-phase refrigerant feeding hole is formed in the first main heat exchanger 2, and a pipeline is connected into the first main heat exchanger 2 through the liquid-phase refrigerant feeding hole and connected with the first refrigerant separator 9 through a throttling valve.
The top of the first refrigerant separator 9 is provided with a gas phase outlet, is externally connected with a first refrigerant separation gas path, and is connected to the first main heat exchanger 2 through the gas path. The bottom of the first refrigerant separator 9 is provided with a liquid phase outlet, is externally connected with a first refrigerant separation liquid path, and is connected to the first main heat exchanger 2 through the liquid path. The first refrigerant separation gas path and the first refrigerant separation liquid path respectively extend into the first main heat exchanger 2 and then are communicated and combined into a pipeline in the first main heat exchanger 2, namely a first refrigerant separation pipeline. The first refrigerant separation pipeline passes through the first main heat exchanger 2, is connected with the mixed refrigerant compressor 1, and enters the mixed refrigerant separator. The top of the mixed refrigerant separator is provided with a gas phase outlet, is externally connected with a pipeline and is communicated with a gas phase refrigerant feeding hole through the pipeline. The bottom of the mixed refrigerant separator is provided with a liquid phase outlet, is externally connected with a pipeline and is communicated with a liquid phase refrigerant feeding hole through the pipeline.
In the present embodiment, the mixed refrigerant compressor 1 is a centrifugal compressor. The first separator 4, the second separator 5, the first refrigerant separator 9, and the second refrigerant separator 10 are all gas-liquid separators. The first main heat exchanger 2 and the second main heat exchanger 3 are both plate-fin heat exchangers. The liquid product pump 8 is a vertical cartridge pump.
The separation process for preparing olefin by dehydrogenation of the feed gas with low hydrogen content (namely alkane dehydrogenation) by using the device comprises the following specific steps:
the gas-phase refrigerant enters the first main heat exchanger 2 through the gas-phase refrigerant feeding hole and then enters the second main heat exchanger 3, and the gas-phase refrigerant and the second main heat exchanger are used for cold exchange. The gas-phase refrigerant flows out of the second main heat exchanger 3, is reduced in pressure by the throttle valve, and enters the second refrigerant separator 10. And the gas separated by the second refrigerant separator 10 enters the second main heat exchanger 3 through a second refrigerant separation gas path, the separated liquid second refrigerant separation liquid path enters the second main heat exchanger 3, the gas and the liquid are mixed to form a first mixed refrigerant, and cold energy is provided for the second main heat exchanger 3 through reheat evaporation. And then the first mixed refrigerant flows out of the second main heat exchanger 3 through a second refrigerant separation pipeline and enters the first refrigerant separator 9 for gas-liquid separation. The liquid-phase refrigerant enters the first main heat exchanger 2 through the liquid-phase refrigerant feed inlet, is reduced in pressure through the throttle valve, and then enters the first refrigerant separator 9 for gas-liquid separation. The gas separated by the first refrigerant separator 9 enters the first main heat exchanger 2 through the first refrigerant separation gas path, the separated liquid is connected to the first main heat exchanger 2 through the first refrigerant separation liquid path, the gas and the liquid are mixed to form a second mixed refrigerant, and cold energy is provided for the first main heat exchanger 2 through reheat evaporation. And then the second mixed refrigerant flows out of the first main heat exchanger 2 through a first refrigerant separation pipeline, enters the mixed refrigerant compressor 1 for supercharging and cooling, and enters the mixed refrigerant separator. The gas separated by the mixed refrigerant separator is injected into the gas-phase refrigerant feed port through a pipeline, and the separated liquid is injected into the liquid-phase refrigerant feed port through a pipeline, so that the refrigeration cycle of the gas-phase refrigerant and the liquid-phase refrigerant is realized.
And feeding the raw material gas into the first main heat exchanger 2 from a raw material gas feeding hole for condensation, and feeding the liquefied raw material gas into a first separator 4 through a pipeline for gas-liquid separation. The gas separated in the first separator 4 enters the second main heat exchanger 3 from the pipeline at the top to be further condensed, and then enters the second separator 5 to be subjected to gas-liquid separation. Liquid separated by the first separator 4 is depressurized by a throttle valve and then enters a flash tank 6, flash liquid of the flash tank 6 is pressurized by a liquid product pump 8 and then enters the first main heat exchanger 2, and flows out from a liquid product outlet of the first main heat exchanger 2 after heat exchange and reheating. The flash steam of the flash tank 6 enters a rectifying column 7 through a pipeline at the top, and alkane and olefin components in the flash steam are recovered after washing and rectifying. And gas in the rectifying column 7 flows through the second main heat exchanger 3 from a pipeline at the top, enters the first main heat exchanger 2, and flows out from a flash evaporation gas outlet of the first main heat exchanger 2 after heat exchange and reheating. The gas separated by the second separator 5 flows out along the dry gas product branch and the circulating hydrogen branch at the top respectively. And the gas flowing out along the dry gas product branch successively enters the second main heat exchanger 3 and the first main heat exchanger 2, and flows out from a dry gas product outlet of the first main heat exchanger 2 after heat exchange and reheating. And the gas flowing out along the circulating hydrogen branch successively enters the second main heat exchanger 3 and the first main heat exchanger 2, and flows out from the combined feed outlet of the first main heat exchanger 2 after heat exchange and reheating. The liquid separated by the second separator 5 is divided into two branches along a bottom pipeline to flow out, the liquid of one branch enters the second main heat exchanger 3 after being depressurized through a throttling valve, enters the flash tank 6 after being reheated through heat exchange, and the liquid of the other branch enters the rectifying column 7 after being depressurized through the throttling valve. The liquid in the rectification column 7 is re-flowed through a line to the flash tank 6.
Alkane is fed into the first main heat exchanger 2 from the alkane feed inlet to be matched with feed gas for dehydrogenation treatment, and then flows out from an upper outlet and a lower outlet of the first main heat exchanger 2 respectively. The alkane flowing along the upper outlet connecting pipeline is depressurized by a throttling valve, enters the first main heat exchanger 2 and is mixed with gas in a circulating hydrogen branch in the first main heat exchanger 2. And the alkane circulating along the lower outlet connecting pipeline respectively enters a second alkane injection branch and a third alkane injection branch, and the alkane in the second alkane injection branch enters the first main heat exchanger 2 after being subjected to pressure reduction through the throttle valve and is mixed with the gas in the circulating hydrogen branch in the first main heat exchanger 2. The alkane in the third alkane injection branch enters the second main heat exchanger 3 to be further cooled, is depressurized through a throttling valve and then reenters the second main heat exchanger 3, and is mixed with the gas in the circulating hydrogen branch in the first main heat exchanger 2.
In this embodiment, the flash steam pressure is in the range of 0.05 to 0.3MPag, and the temperature after reheating is in the range of 30 to 47 ℃. The mixed refrigerant compressor 1 has an inlet pressure of 0.1 to 0.5MPag, an outlet pressure of 2.5 to 4MPag, and an inlet temperature of 30 to 47 ℃. The outlet pressure of the liquid product pump 8 is 3-5 MPag, and the reheating temperature before flowing out through the liquid product outlet is 30-47 ℃. The reheating temperature before the dry gas product outlet and the combined feeding outlet are both 30-47 ℃. The pressure at the dry gas product outlet is 0.4-0.8 MPag, and the pressure at the combined feed outlet is 0.1-0.5 MPag. The gas inlet pressure of the raw material gas is 0.8-1.1 MPag, and the temperature is 35-50 ℃. The feeding pressure of the alkane is 1.2-1.8 MPag, and the temperature is 35-50 ℃.
The invention replaces the common expansion refrigeration process or cascade refrigeration process in alkane dehydrogenation with the mixed refrigerant refrigeration cycle process with advanced technology, and the product gas meets the high purity requirement, meanwhile, the energy consumption of the device is greatly reduced, the equipment quantity is correspondingly reduced, the investment cost and the operation cost are also greatly reduced, and the economic performance is greatly improved.
The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.

Claims (10)

1. A mixed refrigerant refrigeration type cold box separation device for alkane dehydrogenation is characterized by comprising a mixed refrigerant compressor (1), a first main heat exchanger (2), a second main heat exchanger (3), a first separator (4), a second separator (5), a flash tank (6), a rectifying column (7), a liquid product pump (8), a first refrigerant separator (9) and a second refrigerant separator (10);
the pipeline is connected into the first main heat exchanger (2) through a feed gas inlet and then connected into the first separator (4); the top of the first separator (4) passes through the second main heat exchanger (3) through a pipeline and then is connected into the second separator (5), and a pipeline connected from the bottom passes through a throttling valve and then is connected into the flash tank (6); a pipeline connected to the bottom of the flash tank (6) is connected to the first main heat exchanger (2) through a liquid product pump (8) and is connected out of a liquid product outlet of the first main heat exchanger (2), and the top of the flash tank (6) is communicated with the rectifying column (7) through a pipeline; a pipeline connected with the top of the second separator (5) is divided into a dry gas product branch and a circulating hydrogen branch; the dry gas product branch passes through the second main heat exchanger (3), is connected into the first main heat exchanger (2), and is communicated with a dry gas product outlet of the first main heat exchanger (2); the circulating hydrogen branch passes through the second main heat exchanger (3), is connected into the first main heat exchanger (2), and is communicated with a combined feeding outlet of the first main heat exchanger (2); a pipeline connected to the bottom of the second separator (5) is divided into two branches, one branch passes through the throttle valve and then passes through the second main heat exchanger (3) and is connected to the flash tank (6), and the other branch passes through the throttle valve and then is connected to the rectifying column (7); the bottom of the rectifying column (7) is connected with a flash tank (6) through a pipeline, and the top of the rectifying column passes through a second main heat exchanger (3) through a pipeline, is connected into the first main heat exchanger (2), and is connected out from a flash evaporation gas outlet of the first main heat exchanger (2);
the pipeline is connected with the first main heat exchanger (2) through an alkane feeding hole and is respectively communicated with an upper outlet and a lower outlet which are arranged on the first main heat exchanger (2); a pipeline connected from the upper outlet is connected into the first main heat exchanger (2) through a throttle valve and communicated with a circulating hydrogen branch in the first main heat exchanger (2) to form a first alkane injection branch; the pipeline connected from the lower outlet is divided into a second alkane injection branch and a third alkane injection branch; the second alkane injection branch is connected into the first main heat exchanger (2) through a throttling valve and communicated with a circulating hydrogen branch in the first main heat exchanger (2); the third paraffin injection branch is connected with the second main heat exchanger (3) and then is connected out, is connected with the second main heat exchanger (3) again after passing through the throttle valve, and is communicated with a circulating hydrogen branch in the second main heat exchanger (3);
the pipeline is connected to the first main heat exchanger (2) through the gas-phase refrigerant feeding hole, passes through the second main heat exchanger (3), then passes through the throttle valve and is communicated with the second refrigerant separator (10); the top of the second refrigerant separator (10) is connected to the second main heat exchanger (3) through a second refrigerant separation gas path, the bottom of the second refrigerant separator is connected to the second main heat exchanger (3) through a second refrigerant separation liquid path, and the second refrigerant separation gas path and the second refrigerant separation liquid path are communicated in the second main heat exchanger (3) and combined into a second refrigerant separation pipeline; the second refrigerant separation pipeline passes through the second main heat exchanger (3) and then is connected with the first refrigerant separator (9); the pipeline is connected to the first main heat exchanger (2) through a liquid-phase refrigerant feeding hole, passes through a throttle valve and is connected with the first refrigerant separator (9);
the top of the first refrigerant separator (9) is connected to the first main heat exchanger (2) through a first refrigerant separation gas path, the bottom of the first refrigerant separator is connected to the first main heat exchanger (2) through a first refrigerant separation liquid path, and the first refrigerant separation gas path and the first refrigerant separation liquid path are communicated in the first main heat exchanger (2) and combined into a first refrigerant separation pipeline; the first refrigerant separation pipeline passes through the first main heat exchanger (2), is connected with the mixed refrigerant compressor (1) and is connected into the mixed refrigerant separator; the top of the mixed refrigerant separator is communicated with the gas-phase refrigerant feed port through a pipeline, and the bottom of the mixed refrigerant separator is communicated with the liquid-phase refrigerant feed port through a pipeline.
2. The mixed refrigerant refrigerated cold box separation device according to claim 1, wherein the mixed refrigerant compressor (1) is a centrifugal compressor; the first separator (4), the second separator (5), the first refrigerant separator (9) and the second refrigerant separator (10) are all gas-liquid separators.
3. The mixed refrigerant refrigerated cold box separation device according to claim 1, wherein the first main heat exchanger (2) and the second main heat exchanger (3) are both plate-fin heat exchangers; the liquid product pump (8) is a vertical barrel pump.
4. A separation process for dehydrogenating alkane by using the device of any one of claims 1 to 3, which is characterized by comprising the following steps:
the gas-phase refrigerant enters the first main heat exchanger (2) through the gas-phase refrigerant feeding hole and then enters the second main heat exchanger (3) and is used for cold exchange; the gas-phase refrigerant flows out of the second main heat exchanger (3), is reduced in pressure through a throttling valve and enters a second refrigerant separator (10); gas separated by the second refrigerant separator (10) enters the second main heat exchanger (3) through a second refrigerant separation gas path, separated liquid enters the second main heat exchanger (3) through a second refrigerant separation liquid path, the gas and the liquid are mixed to form a first mixed refrigerant, and cold energy is provided for the second main heat exchanger (3) through reheat evaporation; then the first mixed refrigerant flows out of the second main heat exchanger (3) through a second refrigerant separation pipeline and enters a first refrigerant separator (9) for gas-liquid separation; liquid-phase refrigerant enters the first main heat exchanger (2) through a liquid-phase refrigerant feeding hole, is subjected to pressure reduction through a throttle valve and then enters the first refrigerant separator (9) for gas-liquid separation; gas separated by the first refrigerant separator (9) enters the first main heat exchanger (2) through a first refrigerant separation gas path, separated liquid is connected to the first main heat exchanger (2) through a first refrigerant separation liquid path, the gas and the liquid are mixed to form second mixed refrigerant, and cold energy is provided for the first main heat exchanger (2) through reheat evaporation; then, the second mixed refrigerant flows out of the first main heat exchanger (2) through a first refrigerant separation pipeline, enters the mixed refrigerant compressor (1) for pressurization and cooling, and enters the mixed refrigerant separator; gas separated by the mixed refrigerant separator is injected into the gas-phase refrigerant feed port through a pipeline, and separated liquid is injected into the liquid-phase refrigerant feed port through a pipeline, so that refrigeration cycle of the gas-phase refrigerant and the liquid-phase refrigerant is realized;
feeding the raw material gas into a first main heat exchanger (2) from a raw material gas feeding hole for condensation, and feeding the liquefied raw material gas into a first separator (4) through a pipeline for gas-liquid separation; the gas separated by the first separator (4) enters the second main heat exchanger (3) from the pipeline at the top to be further condensed, and then enters the second separator (5) to be subjected to gas-liquid separation; liquid separated by the first separator (4) is depressurized by a throttling valve and then enters a flash tank (6), flash liquid of the flash tank (6) enters the first main heat exchanger (2) after being pressurized by a liquid product pump (8), and flows out from a liquid product outlet of the first main heat exchanger (2) after being reheated by heat exchange; flash steam of the flash tank (6) enters a rectifying column (7) through a pipeline at the top, and alkane and olefin components in the flash steam are recovered after washing and rectifying; gas in the rectifying column (7) flows through the second main heat exchanger (3) from a pipeline at the top, enters the first main heat exchanger (2), and flows out from a flash evaporation gas outlet of the first main heat exchanger (2) after heat exchange and reheating; the gas separated by the second separator (5) flows out along a dry gas product branch and a circulating hydrogen branch at the top respectively; gas flowing out along the dry gas product branch enters the second main heat exchanger (3) and the first main heat exchanger (2) in sequence, and flows out from a dry gas product outlet of the first main heat exchanger (2) after heat exchange and reheating; gas flowing out along the circulating hydrogen branch successively enters the second main heat exchanger (3) and the first main heat exchanger (2), and flows out from a combined feeding outlet of the first main heat exchanger (2) after heat exchange and reheating; the liquid separated by the second separator (5) is divided into two branches along a bottom pipeline to flow out, the liquid in one branch enters the second main heat exchanger (3) after being depressurized through a throttling valve, enters the flash tank (6) after being reheated by heat exchange, and the liquid in the other branch enters the rectifying column (7) after being depressurized through the throttling valve; the liquid in the rectification column (7) flows to the flash tank (6) again through a pipeline;
alkane is fed into the first main heat exchanger (2) from an alkane feeding hole to be matched with feed gas for dehydrogenation treatment, and then flows out of an upper outlet and a lower outlet of the first main heat exchanger (2) respectively; alkane flowing along the upper outlet connecting pipeline is subjected to pressure reduction through a throttling valve, enters the first main heat exchanger (2), and is mixed with gas in a circulating hydrogen branch in the first main heat exchanger (2); alkane circulating along the lower outlet connecting pipeline respectively enters a second alkane injection branch and a third alkane injection branch, and the alkane in the second alkane injection branch enters the first main heat exchanger (2) after being subjected to pressure reduction through the throttle valve and is mixed with gas in a circulating hydrogen branch in the first main heat exchanger (2); the alkane in the third alkane injection branch enters the second main heat exchanger (3) to be further cooled, is depressurized through a throttling valve and then enters the second main heat exchanger (3) again, and is mixed with the gas in the circulating hydrogen branch in the first main heat exchanger (2).
5. The separation process according to claim 4, wherein the flash steam pressure is in the range of 0.05 to 0.3MPag and the temperature after reheating is in the range of 30 to 47 ℃.
6. The separation process according to claim 4, wherein the mixed refrigerant compressor (1) has an inlet pressure of 0.1 to 0.5MPag, an outlet pressure of 2.5 to 4MPag, and an inlet temperature of 30 to 47 ℃.
7. The separation process according to claim 4, wherein the outlet pressure of the liquid product pump (8) is 3 to 5MPag and the reheat temperature before exiting through the liquid product outlet is 30 to 47 ℃.
8. The separation process according to claim 4, wherein the reheat temperature before exiting through the dry gas product outlet and the combined feed outlet is in the range of 30 to 47 ℃; the pressure at the dry gas product outlet is 0.4-0.8 MPag, and the pressure at the combined feed outlet is 0.1-0.5 MPag.
9. The separation process according to claim 4, wherein the feed gas has a feed gas pressure of 0.8 to 1.1MPag and a temperature of 35 to 50 ℃.
10. The separation process of claim 4, wherein the alkane is fed at a pressure of 1.2 to 1.8MPag and at a temperature of 35 to 50 ℃.
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