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CN114963688B - Hydrogen liquefaction system adopting low-temperature turbine compression cycle - Google Patents

Hydrogen liquefaction system adopting low-temperature turbine compression cycle Download PDF

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Publication number
CN114963688B
CN114963688B CN202110404058.2A CN202110404058A CN114963688B CN 114963688 B CN114963688 B CN 114963688B CN 202110404058 A CN202110404058 A CN 202110404058A CN 114963688 B CN114963688 B CN 114963688B
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hydrogen
low
heat exchanger
temperature
stage
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CN202110404058.2A
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CN114963688A (en
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吴英哲
姜伟
钱佚
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Henan Zhongke Qingneng Technology Co ltd
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Henan Zhongke Qingneng 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
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    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0005—Light or noble gases
    • F25J1/001—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
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    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0032—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
    • F25J1/004—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by flash gas recovery
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    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/005—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by expansion of a gaseous refrigerant stream with extraction of work
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    • F25J2250/02—Bath type boiler-condenser using thermo-siphon effect, e.g. with natural or forced circulation or pool boiling, i.e. core-in-kettle heat exchanger
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/14—External refrigeration with work-producing gas expansion loop
    • F25J2270/16—External refrigeration with work-producing gas expansion loop with mutliple gas expansion loops of the same refrigerant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
    • F25J2270/908—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration by regenerative chillers, i.e. oscillating or dynamic systems, e.g. Stirling refrigerator, thermoelectric ("Peltier") or magnetic refrigeration

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

Abstract

The invention provides a hydrogen liquefaction system adopting low-temperature turbine compression circulation, which is characterized in that a low-temperature hydrogen reflux branch is arranged, a shaft driving compressor is arranged on a pipeline of the reflux branch, a driving shaft of the compressor is connected with an output shaft of a turbine expander in a main refrigeration system, so that the expansion work generated when the turbine expander expands and refrigerates a refrigeration working medium is recycled, and the total energy consumption of the hydrogen liquefaction system is reduced; and the main flow of hydrogen flowing in each stage of the para-hydrogen catalytic reactor is further refrigerated through low-temperature hydrogen in the reflux branch. Meanwhile, a mixing ejector is arranged to realize the mixing of the hydrogen in the reflux branch and the hydrogen flowing out of the hydrogen source; the bypass ejector is arranged to realize the backflow of saturated hydrogen in the liquid hydrogen storage tank, so that the pressure in the liquid hydrogen storage tank is reduced, meanwhile, the cold quantity of the flowing saturated hydrogen is recovered, the energy consumption is further reduced, the process of overpressure discharge of the saturated hydrogen in the liquid hydrogen storage tank is avoided, the working efficiency is improved, and the cost is reduced.

Description

Hydrogen liquefaction system adopting low-temperature turbine compression cycle
Technical Field
The invention belongs to the technical field of low-temperature engineering equipment, and particularly relates to a hydrogen liquefaction system adopting a low-temperature turbine compression cycle.
Background
In recent years, with the implementation and structure adjustment of clean energy strategy in China, the development and utilization of various new energy sources attract a lot of attention. Among them, hydrogen energy is one of the long-term solutions important for the current energy problem as an energy source for efficient cleaning. How to safely and effectively store and transport hydrogen energy is a key technical challenge for large-scale applications. The high-pressure normal-temperature hydrogen storage is the hydrogen storage technology which is most widely applied and mature at present. However, with the increasing maturity of cryogenic, adiabatic and vacuum technologies, the storage and transportation mode of low-temperature liquid hydrogen has higher storage density and lower operating pressure, reduces the energy consumption and space cost of unit mass transportation, and is expected to become an effective mode for long-distance transportation and large-scale storage of hydrogen.
The liquefaction of hydrogen is the most critical link in the liquid hydrogen storage and transportation industry chain, and has the characteristics of complex technical process, high energy consumption ratio and high investment cost. Over the past decades, many studies have been underway on how to increase the efficiency of hydrogen liquefaction. The improvement of the efficiency of the hydrogen liquefaction can effectively reduce the operation cost of the hydrogen liquefaction equipment and indirectly reduce the equipment investment cost.
The hydrogen liquefaction system in the prior art generally comprises a main refrigeration system, a liquefaction system and a low-temperature heat exchanger group, wherein the main refrigeration system is provided with a compressor and an expander, and exchanges heat with hydrogen in the liquefaction system through the low-temperature heat exchanger group to refrigerate the hydrogen so as to finally form a liquid hydrogen product. The compressor is used for compressing the high-pressure refrigerant to provide high-pressure refrigerant for the circulating pipeline of the main refrigerating system, and the expander is used for expanding and refrigerating the high-pressure refrigerant to provide cold for the liquefying system. In the low-temperature heat exchanger group, each low-temperature heat exchanger is provided with a normal-para-hydrogen catalytic reactor (an isothermal continuous reactor or an adiabatic step reactor can be adopted) so as to catalyze hydrogen into equilibrium hydrogen at the temperature of the current heat exchanger. Raw material hydrogen provided by a hydrogen source sequentially passes through the secondary hydrogen reactors in the multistage heat exchangers, finally enters the liquid hydrogen storage tank in a liquid state form and flows out from the product outlet.
However, the hydrogen liquefaction plants currently operatedThe efficiency is still relatively low, only 20-30%. The main irreversible losses of the hydrogen liquefaction process mainly come from the compressor, heat exchanger and expander. The isothermal efficiency of helium screw compressor and hydrogen piston compressor adopted in the current mainstream hydrogen liquefaction process is not ideal, only about 40-50%.
The process adopting helium or helium-neon mixed gas as main refrigeration cycle working medium has larger heat exchange temperature difference when exchanging heat with the heat exchanger, especially in a temperature zone near the critical point of near hydrogen; the technology adopting hydrogen as the main refrigeration cycle working medium has the advantages of complex technology, more flow channels, small hydrogen density, large resistance and the like, and the efficiency of the technology in the heat exchanger part in actual engineering is not ideal.
The isentropic efficiency of the low-temperature turbine expander in the current hydrogen liquefaction process can reach more than 70%, but the hydrogen has small molecular weight, and has a plurality of technical challenges for a large-scale high-speed low-temperature hydrogen low-temperature turbine expander, such as bearing rigidity and stability of a large turbine, high stress of turbine tip blades and the like.
Disclosure of Invention
The invention starts from improving compression efficiency, recovering expansion work and optimizing process flow, and provides a hydrogen liquefying system with higher energy efficiency. For this purpose, the invention adopts the following technical scheme:
The hydrogen liquefaction system adopting the low-temperature turbine compression cycle comprises a liquefaction system, a low-temperature heat exchanger group, a precooling system and a main refrigeration system for providing a cold source for the low-temperature heat exchanger group;
the liquefaction system comprises a positive para-hydrogen catalytic reactor I and n-level positive para-hydrogen catalytic reactors connected with the positive para-hydrogen catalytic reactor I in series in sequence; the low-temperature heat exchanger group comprises n-level low-temperature heat exchangers which respectively perform refrigeration and heat exchange on n-level normal-para-hydrogen catalytic reactors; the precooling system provides precooling cooling capacity for the primary and secondary hydrogen catalytic reactor I and the main refrigeration system respectively;
the device also comprises a mixing ejector, a one-shaft driving compressor and a throttling element;
the main refrigeration system comprises at least one turboexpander, and an output shaft of the turboexpander is in transmission connection with the shaft-driven compressor;
a reflux branch is led out from a pipeline of a discharge port of the n-1-level normal-para-hydrogen catalytic reactor, and working medium in the reflux branch sequentially passes through throttling element throttling, at least one low-temperature heat exchanger for heat exchange, a shaft-driven compressor for compression and precooling system for precooling and then enters the mixing ejector as high-pressure fluid; or the working medium of the reflux branch sequentially passes through throttling element throttling and at least one low-temperature heat exchanger for heat exchange to be used as low-pressure fluid to enter the mixer;
When the working medium is used as high-pressure fluid, the material at the outlet of the normal-para-hydrogen catalytic reactor I is used as low-pressure fluid to enter the mixing ejector, and the material is mixed and then sequentially enters the n-level normal-para-hydrogen catalytic reactor; when the working medium is used as low-pressure fluid, the material at the outlet of the normal-para-hydrogen catalytic reactor I is used as high-pressure fluid to enter the mixing ejector, and the mixed material is compressed by the shaft-driven compressor and precooled by the precooling system and then sequentially enters the n-level normal-para-hydrogen catalytic reactor.
The normal-para-hydrogen catalytic reactor and the corresponding low-temperature heat exchanger can adopt an integrated structure or a mutually independent structure. The former belongs to an isothermal continuous reactor, and is characterized in that a low-temperature heat exchanger flow channel is filled with a catalyst, and the reactor is a heat exchanger, namely, the normal para-hydrogen catalytic reaction is completed and the cooling of inflow hydrogen is realized; the latter is an adiabatic step reactor, essentially a single adiabatic container is filled with catalyst, hydrogen is cooled by a corresponding low-temperature heat exchanger and then enters the reactor for catalytic reaction, the temperature rises to some extent, and then the hydrogen is cooled by a subsequent low-temperature heat exchanger again; the isothermal continuous reactor has higher efficiency and more compact structure than the adiabatic step reactor; however, the former is difficult to manufacture, while the latter is simple to manufacture, and both structures can be applied to the technical scheme of the invention.
In the technical scheme, the precooling system precools the hydrogen passing through the primary and secondary hydrogen catalytic reactor I and the working medium in the main refrigerating system, and the precooling temperature is generally 70-120K. The shaft driven compressor is a low temperature turbine compressor. The turboexpander is a low-temperature turboexpander.
In the technical scheme, a plurality of low-temperature turboexpanders can be arranged, one or a plurality of shaft-driven compressors can be arranged according to the requirement, and the transmission shaft of each shaft-driven compressor is connected with the output shaft of one low-temperature turboexpander, so that the expansion work of the low-temperature turboexpander can be fully recovered, and the energy utilization is improved.
Preferably, the liquefaction system further comprises a hydrogen low-temperature purification system connected with the inlet of the normal para-hydrogen catalytic reactor I, and the hydrogen low-temperature purification system is used for removing impurities and purifying hydrogen entering the normal para-hydrogen catalytic reactor I.
The hydrogen low-temperature purification system is a low-temperature purification adsorber. The hydrogen cryogenic purification system may be a single cryogenic purification adsorber or two or more cryogenic purification adsorbers arranged in parallel.
As a further preferable mode, the low-temperature purification system for hydrogen comprises two low-temperature purification adsorbers which are switched through valves and are alternately connected into a pipeline, the two low-temperature purification adsorbers are connected in parallel to form a typical temperature swing adsorption device, and when one low-temperature purification adsorbers are connected into the pipeline, the low-temperature purification adsorbers which are not connected into the pipeline purge and heat clean inert hot gas to realize regeneration, so that the working efficiency of the low-temperature purification system for hydrogen is improved.
Preferably, the low-temperature heat exchanger group is a heat exchanger group consisting of plate-fin type or coiled tube type multi-path convection type heat exchangers.
Preferably, the main refrigeration system comprises a compression system, a main refrigeration working medium low-temperature purification and filtration system and a low-temperature stage. The compression system, the precooling system, the main refrigeration working medium low-temperature purification and filtration system and the low-temperature stage are sequentially connected through pipelines, and a loop is formed. The circulating pipeline of the low-temperature stage at least comprises a low-temperature turboexpander, and the main refrigeration working medium is expanded and refrigerated through the low-temperature turboexpander. The low-temperature stage is coupled with the liquefaction system through the low-temperature heat exchanger group to cool the hydrogen in the liquefaction system, and the lowest cooling temperature is about 20K.
As a further preferable mode, the main refrigerant low-temperature purification and filtration system adopts a low-temperature adsorption filter to realize purification and filtration of the refrigerant.
As a further preference, the compression system comprises at least one working medium compressor, at least one water cooler and an oil removal system. The working medium compressor is used for compressing the working medium circulated back in the main refrigerating system into high-pressure gas, compression heat is taken away by the water cooler, oil gas impurities in the high-pressure working medium are removed through the oil removing system, and then the working medium enters the precooling system for precooling.
Preferably, the main refrigeration system is a brayton cycle refrigeration system or a claude cycle refrigeration system according to the capacity of the hydrogen liquefaction system.
The Brayton cycle refrigerating system adopts helium or helium-neon mixture as working medium, the working medium is compressed by a compression system, precooled to 70-120K by a precooling system, then further sequentially enters an n-level low-temperature heat exchanger to be cooled to about 40K by the reflowed low-temperature working medium, further enters a one-level or multi-level low-temperature turbine expander for expansion refrigeration, the temperature of the working medium is reduced to below 20K, then sequentially returns to the n-level low-temperature heat exchanger in a reverse direction (from the n-th low-temperature heat exchanger to the first-level low-temperature heat exchanger), and cools the inflowing high-temperature working medium and hydrogen of a liquefying system. The technical scheme avoids the hydrogen-related equipment with higher technical difficulty such as a high-pressure hydrogen pipeline, a hydrogen compressor, a hydrogen low-temperature turbine expander and the like, has simpler process flow, and is more suitable for medium and small hydrogen liquefaction devices with the capacity below 5 tons/day.
The Claude circulation refrigerating system adopts hydrogen as a working medium, the working medium is compressed by a compression system, the working medium is precooled to 70-120K through a precooling system, then the working medium further sequentially enters a multi-stage low-temperature heat exchanger and is cooled to about 40K by the reflowed low-temperature working medium, one part of the hydrogen is sequentially and reversely returned to the multi-stage low-temperature heat exchanger to cool inflow hydrogen after expansion refrigeration through a hydrogen expander (a low-temperature turbine expander), the other part of the hydrogen continuously enters a low-temperature heat exchanger with lower temperature, finally isenthalpic flow is reduced by a throttling device to generate cold energy, and then the hydrogen is sequentially and reversely returned to an n-stage low-temperature heat exchanger (from an n-th low-temperature heat exchanger to a first-stage low-temperature heat exchanger) to cool inflow hydrogen. The claude cycle has various variations depending on the different temperature levels and series arrangements of the low temperature turboexpander and the series arrangement of the compression system. The technical scheme has more complex process flow, but the hydrogen working medium has higher heat exchange performance, and can obtain higher efficiency in the low-temperature heat exchanger, so that the energy efficiency is better than that of a brayton cycle refrigerating system adopting helium or helium-neon mixed working medium, and the method is more suitable for medium-large hydrogen liquefaction devices with the capacity of more than 5 tons/day.
Preferably, the throttling element is an expander, a throttle valve or a bypass injector.
As a further preference, the liquefaction system further comprises a liquid hydrogen storage tank connected to the nth stage normal para-hydrogen catalytic reactor through a pipeline;
the throttling element is a bypass ejector, and the backflow branch is connected with a high-pressure inlet of the bypass ejector; and a gas phase outlet of the liquid hydrogen storage tank is connected with a low pressure inlet of the bypass ejector through a gas phase loop.
As a further preferable scheme, a pipeline is led out from the bottom of the liquid hydrogen storage tank to a liquid hydrogen product outlet for outputting liquid hydrogen.
As a further preferable scheme, the gas phase loop is connected with a low-pressure inlet of the bypass ejector after heat exchange of the nth-stage low-temperature heat exchanger.
In the scheme, gaseous hydrogen in the liquid hydrogen storage tank flows out from a gas phase outlet to enter the bypass ejector after heat exchange of the nth-stage low-temperature heat exchanger, so that the pressure in the liquid hydrogen storage tank can be reduced, and the cold energy of the gaseous hydrogen can be recovered to further cool the hydrogen in the nth-stage normal-para-hydrogen catalytic reactor.
Furthermore, the working medium at the outlet of the bypass ejector exchanges heat with the n-1 st low-temperature heat exchanger in sequence. The cold energy of the reflux working medium is fully utilized.
As a further preferred embodiment, the gas phase circuit is connected directly to the low pressure inlet of the bypass injector.
In the scheme, gaseous hydrogen in the liquid hydrogen storage tank flows out from the gas phase outlet and is mixed with the reflowed working medium in the bypass ejector, and then the mixture is subjected to heat exchange through the nth-stage low-temperature heat exchanger, so that the pressure in the liquid hydrogen storage tank can be reduced, and the cold energy of the gaseous hydrogen can be recovered to further cool the hydrogen in the nth-stage normal-para-hydrogen catalytic reactor.
Furthermore, the working medium at the outlet of the bypass ejector sequentially passes through the nth-level to 1-level low-temperature heat exchangers to exchange heat.
As a further preferable mode, a throttling device is arranged on a pipeline of the liquid hydrogen storage tank and the nth-stage cryogenic heat exchanger so as to further decompress and refrigerate the hydrogen at the outlet of the nth-stage cryogenic heat exchanger. Preferably, the throttle device is a throttle valve.
Preferably, a compensation driving motor is arranged on a shaft connecting the expander and the compressor. The compensation drive motor is used for providing additional power to drive the low-temperature turbine compressor so that the low-temperature turbine compressor obtains enough compression driving force.
As a further preferred aspect, the compensation driving motor is a high-speed superconducting motor to reduce motor loss and motor size.
Preferably, the shaft driven compressor comprises a low temperature turbine compressor.
Preferably, the working medium in the reflux branch is sequentially subjected to heat exchange with the n-1 st low-temperature heat exchanger, so that the cooling and refrigerating efficiency is further improved.
Preferably, the pre-cooling system comprises a pre-cooling heat exchanger and a cooling system for providing a cold source for the pre-cooling heat exchanger, the cooling system is coupled with the main refrigerating system and the liquefying system through the pre-cooling heat exchanger, and the pre-cooling heat exchanger provides cold for the normal-para-hydrogen catalytic reactor I and the main refrigerating system respectively.
According to different conditions of the site where the hydrogen liquefaction system is located, as a further preferable mode, the cooling system is an open type low-temperature frozen liquid precooling system or a closed type low-temperature refrigeration precooling system. The open type low-temperature frozen liquid precooling system adopts liquid nitrogen or liquefied natural gas as a cold source working medium, the former is particularly suitable for the situation that stable and cheap liquid nitrogen can be obtained on site, and if an air separation device is arranged nearby, stable and cheap liquid nitrogen resources can be provided; the latter is especially suitable for the occasion of liquefied natural gas harbor and the like needing to recover the liquefied natural gas vaporization cold energy.
The closed low-temperature refrigeration precooling system is a turbine brayton cycle refrigeration system, a self-cascade mixed working medium refrigeration system or a regenerative refrigeration system, and is suitable for the scenes that the electricity price is low or low-temperature liquid such as liquid nitrogen, liquefied natural gas and the like is not easy to obtain on site.
As a further preference, the pre-cooling heat exchanger is a plate-fin or tube-around multi-path convection heat exchanger.
Unlike the conventional hydrogen liquefying device, the hydrogen liquefying system of the invention adopts a refrigeration liquefying cycle with low-temperature compression, and the basic idea is that:
1. the circulating hydrogen flow (reflux hydrogen, namely working medium in a reflux branch) is compressed by adopting a low-temperature turbine compressor running at the precooling temperature (70-120K), and the precooling system is utilized to take away the compression heat;
or the circulating hydrogen flow and the raw material hydrogen flow are mixed in a mixing ejector to form a main flow of hydrogen, and then enter a low-temperature turbine compressor for compression: the normal-para-hydrogen catalytic reactor I positioned in the pre-cooling heat exchanger is connected with a high-pressure inlet of the mixing ejector, an outlet of the mixing ejector is connected with a low-pressure inlet of the low-temperature turbine compressor, and a reflux circulating hydrogen outlet of the low-temperature heat exchanger (a first-stage low-temperature heat exchanger) with the highest temperature is connected with a low-pressure inlet of the mixing ejector.
2. The low-temperature turbine compressor is driven by expansion work generated by a low-temperature turbine expander in the main refrigeration system;
3. mixing the circulating hydrogen flow and the raw material hydrogen flow by adopting a mixing ejector to form a main hydrogen flow;
4. Before the main flow of hydrogen enters the cryogenic heat exchanger with the lowest temperature (the nth stage cryogenic heat exchanger), the main flow of hydrogen is divided into two paths of circulating hydrogen flow and liquefied hydrogen flow:
4.1, circulating hydrogen flows into a bypass ejector, on one hand, the circulating hydrogen flows are used for pumping and recovering low-pressure saturated gaseous hydrogen from the top of a liquid hydrogen storage tank, on the other hand, the hydrogen is subjected to isenthalpic throttling to generate a refrigeration effect, and the hydrogen after mixed cooling sequentially returns to each stage of low-temperature heat exchanger (from an nth stage of low-temperature heat exchanger to a first stage of low-temperature heat exchanger) to cool the inflowing hydrogen;
or the saturated hydrogen from the liquid hydrogen storage tank firstly passes through the nth-stage low-temperature heat exchanger to exchange heat, then is mixed with the circulating hydrogen flow in the bypass ejector, and then sequentially passes through the nth-1-stage low-temperature heat exchanger to the first-stage low-temperature heat exchanger: and a gas phase pipeline (gas phase loop) is led out from the top of the liquid hydrogen storage tank and is connected with a low-pressure inlet of a bypass ejector, and an outlet of the bypass ejector is connected with an n-1 level low-temperature heat exchanger.
And 4.2, cooling the liquefied hydrogen flow in a normal para-hydrogen catalytic reactor in a final-stage heat exchanger (an nth-stage low-temperature heat exchanger), and performing isenthalpic throttling through a throttling device to realize liquefaction and entering a liquid hydrogen storage tank.
The invention provides a hydrogen liquefaction system adopting low-temperature turbine compression circulation, which is characterized in that a low-temperature hydrogen reflux branch is arranged, a shaft driving compressor is arranged on a pipeline of the reflux branch, a driving shaft of the compressor is connected with an output shaft of a turbine expander in a main refrigeration system, so that the expansion work generated when the turbine expander expands and refrigerates a refrigeration working medium is recycled, and the total energy consumption of the hydrogen liquefaction system is reduced; and the main flow of hydrogen flowing in each stage of the para-hydrogen catalytic reactor is further refrigerated through low-temperature hydrogen in the reflux branch. Meanwhile, a mixing ejector is arranged to realize the mixing of the hydrogen in the reflux branch and the hydrogen flowing out of the hydrogen source; the bypass ejector is arranged to realize the backflow of saturated hydrogen in the liquid hydrogen storage tank, so that the pressure in the liquid hydrogen storage tank is reduced, meanwhile, the cold quantity of the flowing saturated hydrogen is recovered, the energy consumption is further reduced, the process of overpressure discharge of the saturated hydrogen in the liquid hydrogen storage tank is avoided, the working efficiency is improved, and the cost is reduced.
Compared with the prior art, the invention has the beneficial effects that:
the hydrogen liquefaction system adopting the low-temperature turbine compression cycle fully utilizes the expansion work of the turbine expander of the main refrigeration cycle to drive the liquefaction system to form own refrigeration cycle, and has higher energy efficiency. The low-temperature turbine compression cycle process adopted by the invention compresses hydrogen at a low temperature of 77-100K, and has higher efficiency than the compression at room temperature due to higher hydrogen density and lower adiabatic compression coefficient at the low temperature.
Compared with the traditional Joule-Thomson circulating refrigeration process, the process for carrying out bypass expansion on the main hydrogen flow by adopting the bypass ejector has higher compressor return air pressure under the condition of same throttling expansion pressure, reduces the power consumption of the compressor and has higher energy efficiency; compared with the bypass process adopting the turbine expander, the method avoids using a complex and expensive low-temperature hydrogen expander, has simple process flow and can recover vapor phase hydrogen of the liquid hydrogen storage tank.
Drawings
FIG. 1 is a schematic diagram of a first embodiment of a hydrogen liquefaction plant employing a cryogenic turbine compression cycle according to the present invention;
FIG. 2 is a schematic diagram of a second embodiment of a hydrogen liquefaction plant employing a cryogenic turbine compression cycle according to the present invention;
FIG. 3 is a schematic diagram of a third embodiment of a hydrogen liquefaction plant employing a cryogenic turbine compression cycle according to the present invention;
FIG. 4 is a schematic diagram of a fourth embodiment of a hydrogen liquefaction plant employing a cryogenic turbine compression cycle according to the present invention, wherein the pre-cooling system employs an open liquid nitrogen pre-cooling system and the main refrigeration system employs a helium Brayton cycle refrigeration system;
fig. 5 is a schematic diagram of a fifth embodiment of a hydrogen liquefaction plant employing a cryogenic turbine compression cycle according to the present invention, wherein the precooling system employs a closed turbine brayton refrigeration system and the main refrigeration system employs a hydrogen claude cycle refrigeration system.
The correspondence between the reference numbers and the component names in the figures is:
100. cold supply system, 101, liquid nitrogen storage tank, 102, liquid nitrogen source, 103, cryogenic turbine compressor I, 105, cryogenic turbine expander I, 106, high speed motor, 200, primary refrigeration system, 210, compression system, 211, screw compressor, 212, water cooler I, 213, oil removal system, 214, primary compressor, 215, primary water cooler, 216, secondary compressor, 217, secondary water cooler, 220, primary refrigerant cryogenic purification filtration system, 221, cryogenic adsorption filter, 230, cryogenic stage, 231, cryogenic turbine expander, 232, primary cryogenic turbine expander, 233, secondary cryogenic turbine expander, 234, throttle valve, 300, liquefaction system, 301, hydrogen gas source, 302, hydrogen cryogenic purification system, 302a, hydrogen cryogenic purification adsorber A, 302B, hydrogen cryogenic purification adsorber B, 303, normal para-hydrogen catalytic reactor I. A hybrid ejector, 305, low temperature turbine compressor, 306, offset drive motor, 307, first stage positive-to-para-hydrogen catalytic reactor, 308, n-1 stage positive-to-para-hydrogen catalytic reactor, 309, bypass ejector, 310, n-1 stage positive-to-para-hydrogen catalytic reactor, 311, throttle device, 312, liquid hydrogen storage tank, 313, liquid hydrogen product outlet, 314, second stage positive-to-para-hydrogen catalytic reactor, 315, third stage positive-to-para-hydrogen catalytic reactor, 316, throttle valve, 317, fourth stage positive-to-para-hydrogen catalytic reactor, 318, fifth stage positive-to-para-hydrogen catalytic reactor, 319, sixth stage positive-to-para-hydrogen catalytic reactor, 400, pre-cooling heat exchanger, 500, cryogenic heat exchanger set, 501, first stage cryogenic heat exchanger, 502, n-1 stage cryogenic heat exchanger, 503, n-stage cryogenic heat exchanger, 504, second stage cryogenic heat exchanger, 505, third stage cryogenic heat exchanger, 506. Fourth-stage low-temperature heat exchanger, 507, fifth-stage low-temperature heat exchanger, 508 and sixth-stage low-temperature heat exchanger.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be described in further detail below with reference to the embodiments of the present invention and the accompanying drawings, but the described embodiments are some, but not all, embodiments of the present invention. Other embodiments that are not creatively labor by those of ordinary skill in the art based on the embodiments of the present invention are all within the protection scope of the present invention.
Example 1:
as shown in fig. 1, a hydrogen liquefaction system employing a cryogenic turbine compression cycle includes a refrigeration system 100, a main refrigeration system 200, a liquefaction system 300, a pre-chill heat exchanger 400, and a cryogenic heat exchanger bank 500. The cooling system 100 is coupled to the main refrigeration system 200 and the liquefaction system 300 through a pre-cooling heat exchanger 400, and pre-cools the working medium of the main refrigeration system 200 and the hydrogen of the liquefaction system 300, and the pre-cooling temperature is generally about 70 to 120K.
The main refrigeration system 200 includes a compression system 210, a main refrigerant cryogenic purification filtration system 220, and a cryogenic stage 230. The compression system 210, the pre-cooling heat exchanger 400, the main refrigerant low-temperature purification and filtration system 220 and the low-temperature stage 230 are sequentially connected through pipelines, and form a loop. The circulation pipeline of the low-temperature stage 220 comprises a low-temperature turboexpander 231 (the first-stage low-temperature turboexpander is selected in the embodiment), and the gas working medium is expanded and refrigerated by the low-temperature turboexpander 231. The low-temperature stage 230 is coupled to the liquefaction system 300 through the low-temperature heat exchanger group 500, and cools the hydrogen in the liquefaction system 300, and the minimum precooling temperature is about 20K.
The liquefaction system 300 comprises a hydrogen gas source 301, a hydrogen low-temperature purification system 302, a normal para-hydrogen catalytic reactor I303, an n-stage normal para-hydrogen catalytic reactor, a mixing ejector 304, a low-temperature turbine compressor 305, a bypass ejector 309, a throttling device 311, a liquid hydrogen storage tank 312 and a compensation driving motor 306.
The hydrogen gas source 301, the pre-cooling heat exchanger 400, the hydrogen low-temperature purification system 302, the normal para-hydrogen catalytic reactor I303 and the low-pressure inlet of the mixing injector 304 are sequentially connected through pipelines; the outlet of the mixing ejector 304, the n-level positive para-hydrogen catalytic reactors in each low-temperature heat exchanger group are sequentially connected through pipelines from high temperature to low temperature (from the first-level positive para-hydrogen catalytic reactor 307 to the n-level positive para-hydrogen catalytic reactor 310), a throttling device 311 and a liquid hydrogen storage tank 312, wherein a pipeline (reflux branch) is led out from the pipeline between the two positive para-hydrogen catalytic reactors with the lowest temperature and the second lowest temperature (the n-level positive para-hydrogen catalytic reactor 310 and the n-1-level positive para-hydrogen catalytic reactor 308) to be connected with a high-pressure inlet of the bypass ejector 309.
A pipeline is led out from the bottom of the liquid hydrogen storage tank 312 to a liquid hydrogen product outlet 313 for outputting liquid hydrogen, and a gas phase pipeline (gas phase loop) is led out from the top of the liquid hydrogen storage tank 312, returns to pass through a low-temperature heat exchanger (an nth-stage low-temperature heat exchanger 503) with the lowest temperature and then is connected with a low-pressure inlet of the bypass ejector 309; the outlet of the bypass eductor 309 and the remaining (n-1 stage cryogenic heat exchanger 503-first stage cryogenic heat exchanger 501) cryogenic heat exchangers are connected sequentially from low temperature to high temperature and then to the low pressure inlet of the cryogenic turbine compressor 305.
The high-pressure outlet of the low-temperature turbine compressor 305 is connected with an interface in the middle of the pre-cooling heat exchanger 400 through a pipeline, and is connected with a high-pressure inlet of the mixing ejector 304 after being pre-cooled by the pre-cooling heat exchanger 400; the low-temperature turbocompressor 305 is mechanically coupled to the low-temperature turboexpander 231 in the main refrigeration system 200 via a shaft, and a compensation driving motor 306 is disposed on the shaft, so that the expansion generated by the low-temperature turboexpander 231 in the main refrigeration process is used for driving the low-temperature turbocompressor 305, and the compensation driving motor 306 is used for providing additional power to drive the low-temperature turbocompressor 305.
The working principle of implementing the hydrogen liquefaction by adopting the embodiment is as follows:
the cooling system 100 is coupled to the main refrigeration system 200 and the liquefaction system 300 through a pre-cooling heat exchanger 400, and pre-cools the working medium of the main refrigeration system 200 and the hydrogen of the liquefaction system 300, and the pre-cooling temperature is generally about 70 to 120K. The low-temperature working medium generated by the cooling system 100 enters a cold end inlet of the pre-cooling heat exchanger 400, and the working medium of the main refrigeration system 200 and the hydrogen of the liquefaction system 300 are pre-cooled in the pre-cooling heat exchanger 400; the working medium is re-warmed to about room temperature in the pre-cooling heat exchanger 400, leaves the hot end outlet of the pre-cooling heat exchanger 400, and then leaves the whole hydrogen liquefying device (for an open low-temperature refrigerating liquid cooling system) or returns to the cooling system 100 (for a closed low-temperature refrigerating cooling system) according to the type of the cooling system 100.
The main refrigeration system 200 is coupled to the liquefaction system 300 through the pre-cooling heat exchanger 400 and the cryogenic heat exchanger bank 500, and pre-cools the hydrogen in the liquefaction system 300, and the pre-cooling temperature is typically about 20K. After the working medium of the main refrigeration system 200 is compressed into high pressure by the compression system 210, the working medium enters the pre-cooling heat exchanger 400 to be pre-cooled to about 70-120K, and then further enters each stage of low-temperature heat exchangers (sequentially enters from the first stage of low-temperature heat exchanger 501 to the nth stage of low-temperature heat exchanger 503) in sequence, and the reflowed cold working medium (working medium of the main refrigeration system 200) is cooled. During the period, the working medium is expanded through the low-temperature turbine expander 231 to generate a refrigeration effect, and finally the working medium with low pressure and low temperature sequentially returns to each stage of low-temperature heat exchangers (sequentially returns from the nth stage of low-temperature heat exchanger 503 to the first stage of low-temperature heat exchanger 501) to cool the high-pressure high-temperature working medium and the hydrogen of the liquefaction system 300.
In the liquefaction system 300, the raw material hydrogen gas flow from the hydrogen gas source 301 firstly enters the pre-cooling heat exchanger 400 for pre-cooling, and sequentially passes through the hydrogen low-temperature purification system 302 and the normal para-hydrogen catalytic reactor I303 which are arranged in the pre-cooling heat exchanger 400, so that impurity gas and particulate matters in the hydrogen are removed, the primary normal para-hydrogen catalytic reaction is completed, and the para-hydrogen content reaches a state close to an equilibrium state (for example, the pre-cooling temperature is 77.4K of liquid nitrogen, and the para-hydrogen content of the equilibrium state hydrogen is 50.2%).
Next, the raw hydrogen stream (pressure p feed ) A low pressure inlet pumped into the mixing eductor 304 and a high pressure recycle hydrogen stream (pressure p) compressed via the low temperature turbine compressor 305 and cooled by the pre-cooling heat exchanger 400, entering the high pressure inlet of the mixing eductor 304 compr ) Is mixed into the main flow of hydrogen (pressure p main ) Exiting the outlet of the mixing eductor 304. In the mixing injector 304, p compr ＞p main ＞p feed The pressure potential energy of the high-pressure circulating hydrogen gas stream is utilized to change the pressure of the raw material hydrogen gas stream from p reed Lifting to p main . The main flow of hydrogen further enters the normal para-hydrogen catalytic reactor in each stage of low-temperature heat exchanger along the temperature decreasing direction, is cooled to about 35K by the reflux working medium of the main refrigeration system 200 and the reflux cold hydrogen circulation flow, and simultaneously the normal para-hydrogen reaction occurs, and the para-hydrogen content reaches a nearly equilibrium state.
Before entering the cryogenic heat exchanger with the lowest temperature (the N-stage cryogenic heat exchanger 503), the main flow of hydrogen is divided into two paths, one path is a circulating hydrogen flow (a return hydrogen branch) and enters the high-pressure inlet of the bypass ejector 309; the other path is liquefied hydrogen gas flow, and the liquefied hydrogen gas flow further enters an n-stage normal para-hydrogen catalytic reactor 310 in a low-temperature heat exchanger (n-stage low-temperature heat exchanger 503) with the lowest temperature, is cooled to about 20-25K by a reflux working medium of a main refrigeration system 200 and low-temperature saturated hydrogen from a gas phase pipeline of a liquid hydrogen storage tank 312, and simultaneously, normal para-hydrogen reaction occurs to enable the para-hydrogen content to reach more than 95%.
The liquefied hydrogen gas flow leaves the nth-stage cryogenic heat exchanger 503 and enters a throttling device 311 to perform isenthalpic throttling, so that the liquefied hydrogen gas is liquefied, and then enters a liquid hydrogen storage tank 312. In the liquid hydrogen storage tank 312, the liquid hydrogen at the bottom flows out as a product from a liquid phase pipeline arranged at the bottom of the liquid hydrogen storage tank 312, and the saturated hydrogen at the top returns through a gas phase pipeline arranged at the top of the liquid hydrogen storage tank 312, enters the nth-stage cryogenic heat exchanger 503 to pre-cool the flowing liquefied hydrogen flow, and then enters a low-pressure inlet of the bypass injector 309.
In the bypass eductor 309, the return hydrogen is branched (pressure p main ) With saturated hydrogen flow (pressure p sat Typically 1-2 bar) to form a recycle hydrogen stream (pressure p return ) Wherein p is main ＞p return ＞p sat Low pressure saturated hydrogen vapor is pumped from the liquid hydrogen storage tank 312 using pressure potential energy from the circuit hydrogen branch of the main flow of hydrogen (pressure from p main Lifting to p sat ). The back-flowing hydrogen circulation flow sequentially enters each stage of low-temperature heat exchanger (sequentially returns from the nth stage of low-temperature heat exchanger 503 to the first stage of low-temperature heat exchanger 501) along the increasing temperature direction, cools the main flow of the hydrogen, and finally enters the low-temperature turbine compressor 305 to be compressed to high pressure (the pressure is p compr )。
Example 2:
as shown in fig. 2, the hydrogen liquefaction system employing the low-temperature turbine compression cycle is different from embodiment 1 in that:
the normal-para-hydrogen catalytic reactor I303 positioned in the pre-cooling heat exchanger 400 is connected with the high pressure inlet of the mixing ejector 304, the outlet of the mixing ejector 304 is connected with the low pressure inlet of the low-temperature turbine compressor 305, and the reflux hydrogen circulation outflow port of the low-temperature heat exchanger (the first-stage low-temperature heat exchanger 501) with the highest temperature is connected with the low pressure inlet of the mixing ejector 304. In this example, the returned hydrogen recycle stream (pressure p return ) And a feed hydrogen stream (pressure p feed ) Is mixed in a mixing injector 304 to form a main flow of hydrogen (pressure p main ) Then enters the low temperature turbine compressor 305 for compression to high pressure (pressure p compr )。
In the mixing injector 304 of the present embodiment, p feed ＞p main ＞p return Recycle of reflux lower pressure hydrogen recycle stream from p using pressure potential energy of feed hydrogen stream return Lifting to p main . This embodiment is suitable for hydrogen gas pressure provided by the hydrogen gas source 301 having a relatively high pressure,and higher than the pressure of the hydrogen recycle stream at reflux.
Example 3:
as shown in fig. 3, the hydrogen liquefaction system employing the low temperature turbine compression cycle is different from example 1 in that:
A gas phase pipeline (gas phase loop) led out from the top of the liquid hydrogen storage tank 312 is connected with a low-pressure inlet of the bypass ejector 309, and an outlet of the bypass ejector 309 is connected with a low-temperature heat exchanger (an nth-stage low-temperature heat exchanger 503) with the lowest temperature.
In this embodiment, saturated hydrogen from liquid hydrogen tank 312 (pressure p sat ) In the bypass eductor 309 with the recycle hydrogen stream (return hydrogen branch) (pressure p main ) First mixed and throttle expanded to a lower pressure to form a reflux hydrogen recycle stream (pressure p return ) The incoming liquefied hydrogen stream is then cooled by entering the cryogenic heat exchanger with the lowest temperature (the nth stage cryogenic heat exchanger 503).
In the bypass eductor 309 of the present embodiment, p main ＞p return ＞p sat Low pressure saturated hydrogen is pumped from the liquid hydrogen storage tank 312 using the pressure potential of the recycle hydrogen stream from the main stream of hydrogen (pressure from p main Lifting to p sat )。
Example 4:
as shown in fig. 4, a hydrogen liquefaction system employing a cryogenic turbine compression cycle, liquid nitrogen pre-cooling, and helium brayton cycle is illustrated in more detail, including a refrigeration system 100, a main refrigeration system 200, a liquefaction system 300, a pre-cooling heat exchanger 400, and a cryogenic heat exchanger.
The cooling system 100 includes a liquid nitrogen source 102 and a liquid nitrogen storage tank 101. The main refrigeration system 200 includes a screw compressor 211 (working medium compressor), a water cooler I212, an oil removal system 213, a low temperature adsorption filter 221, a first stage low temperature turbo-expander 232, and a second stage low temperature turbo-expander 233. The liquefaction system 300 includes a hydrogen gas source 301, a hydrogen cryogenic purification adsorber a302a, a hydrogen cryogenic purification adsorber B302B, a normal para-hydrogen catalytic reactor I303, a mixing injector 304, a first stage normal para-hydrogen catalytic reactor 307, a second stage normal para-hydrogen catalytic reactor 314, a third stage normal para-hydrogen catalytic reactor 315, a throttle valve 316, a liquid hydrogen storage tank 312, a liquid hydrogen product outlet 313, a bypass injector 309, a low temperature turbine compressor 305, and a make-up drive motor 306. The low temperature heat exchanger group 500 includes three convection heat exchangers from high to low temperature: a first stage cryogenic heat exchanger 501, a second stage cryogenic heat exchanger 504 and a third stage cryogenic heat exchanger 505.
The connection sequence of the components in the cooling system 100 is as follows: the liquid nitrogen source 102 is connected with the liquid nitrogen storage tank 101, a liquid phase pipeline led out from the bottom of the liquid nitrogen storage tank 101 is connected with a cold end inlet of the pre-cooling heat exchanger 400, then a pipeline led out from the middle of the pre-cooling heat exchanger 400 is connected with the top of the liquid nitrogen storage tank 101, another gas phase pipeline on the top of the liquid nitrogen storage tank 101 is connected with an inlet in the middle of the pre-cooling heat exchanger 400, cold nitrogen in the liquid nitrogen storage tank 101 is led into the pre-cooling heat exchanger 400, and finally the cold nitrogen is discharged from the hot end of the pre-cooling heat exchanger 400.
The cooling system 100 operates on the principle that: the liquid nitrogen source 102 supplements liquid nitrogen into the liquid nitrogen storage tank 101, and keeps the liquid level in the liquid nitrogen storage tank 101 not lower than a set height; saturated liquid nitrogen led out of the liquid nitrogen storage tank 101 firstly enters the cold end of the pre-cooling heat exchanger 400 to pre-cool the working medium of the main refrigeration system 200 and the hydrogen of the liquefaction system 300, the liquid nitrogen is heated and evaporated to form saturated gas which leaves from the middle part of the pre-cooling heat exchanger 400 and enters a gas phase space at the top of the liquid nitrogen storage tank 101 to form a typical self-pressurization flow; the saturated liquid nitrogen gas flows out from the other gas phase outlet (gas phase pipeline) at the top of the liquid nitrogen storage tank 101 under the action of the self-pressurization process, enters the middle part of the pre-cooling heat exchanger 400 and continuously flows towards the hot end, pre-cooling is provided for working medium of the main refrigeration system 200 and hydrogen of the liquefaction system 300, and finally the nitrogen is heated to about room temperature and leaves at the hot end of the pre-cooling heat exchanger 400.
In this embodiment, the open type low-temperature frozen liquid cooling system 100 using liquid nitrogen as the cold source working medium can provide a precooling temperature of about 77-100K according to the difference of the pressure of the liquid nitrogen storage tank 101.
The connection sequence of the components in the main refrigeration system 200 is as follows: the high-pressure outlet of the screw compressor 211, the water cooler 212, the oil removal system 213, the pre-cooling heat exchanger 400, the low-temperature adsorption filter 221, the first-stage low-temperature heat exchanger 501, the first-stage low-temperature turboexpander 232, the second-stage low-temperature heat exchanger 504 and the second-stage low-temperature turboexpander 233 are sequentially connected, and an outlet pipeline of the second-stage low-temperature turboexpander 233 sequentially passes through the third-stage low-temperature heat exchanger 505, the second-stage low-temperature heat exchanger 504 and the first-stage low-temperature heat exchanger 501 from low temperature to high temperature and is finally connected with a low-pressure inlet of the screw compressor 211.
Wherein the working fluid in the main refrigeration system 200 is helium. The principle of operation of the main refrigeration system 200 is: the helium working medium is compressed to high pressure through a screw compressor 211, compression heat generated by compression is taken away by a water cooler 212 and cooled to about room temperature, and then enters an oil removal system 213 to remove most of oil gas impurities in the working medium; the compressed, cooled and deoiled high-pressure helium gas enters a pre-cooling heat exchanger 400 to be pre-cooled to about 77-100K, and then residual particulate impurities solidified at low temperature are removed through a low-temperature adsorption filter 221; after leaving the low-temperature adsorption filter 221, helium enters the first-stage low-temperature heat exchanger 501 to be precooled to about 40-50K by the reflowed cold helium, then enters the first-stage low-temperature turbine expander 232 to be expanded and refrigerated, the temperature is reduced to about 5-10K, and the pressure is reduced to medium pressure; helium gas enters a second-stage low-temperature heat exchanger 504 after leaving a first-stage low-temperature turboexpander 232 and is further precooled to about 25-30K; then enters a second-stage low-temperature turbine expander 233 for expansion refrigeration, the temperature is reduced to about 17-20K, and the pressure is reduced to low pressure; subsequently, the helium gas with low temperature and low pressure reversely passes through the third-stage cryogenic heat exchanger 505, the second-stage cryogenic heat exchanger 504 and the first-stage cryogenic heat exchanger 501 in turn to provide cold for the inflow helium gas and the hydrogen gas of the liquefaction system 300, and after passing through the pre-cooling heat exchanger 400, the helium gas is re-warmed to about room temperature and finally returns to the low pressure inlet of the compressor.
The connection sequence of the components in liquefaction system 300 is as follows: the hydrogen source 301 is connected with the hot end interface of the pre-cooling heat exchanger 400, and after the inflow raw material hydrogen leaves the cold end of the pre-cooling heat exchanger 400, the inflow raw material hydrogen is connected with the hydrogen low-temperature purification absorber A302a and the hydrogen low-temperature purification absorber B302B which are connected in parallel. Here, the hydrogen low-temperature purification absorber a302a and the hydrogen low-temperature purification absorber B302B form a typical temperature swing adsorption device, the two absorbers are switched by valves and alternately connected to a pipeline, and the absorbers which are not connected to the pipeline are purged and heated by clean inert hot gas to realize regeneration. The hydrogen low-temperature purification absorber A302a and the hydrogen low-temperature purification absorber B302B are connected in parallel and then connected with an inlet in the middle of the pre-cooling heat exchanger 400 through a pipeline, and then enter the normal para-hydrogen catalytic reactor I303 positioned at the lower temperature end of the pre-cooling heat exchanger 400. In this embodiment, all the normal-para-hydrogen catalytic reactors (including the normal-para-hydrogen catalytic reactor I303, the first-stage normal-para-hydrogen catalytic reactor 307, the second-stage normal-para-hydrogen catalytic reactor 314, and the third-stage normal-para-hydrogen catalytic reactor 315) are isothermal reactors coupled in a heat exchanger, i.e., catalyst particles are filled in heat exchange channels of the heat exchanger, and the normal-para-hydrogen catalytic reaction is realized while heat exchange is performed.
Such isothermal reactors have a high reaction efficiency and low irreversible losses. The outlet of the low temperature end of the normal para-hydrogen catalytic reactor I303 is connected with the low pressure inlet of the mixing ejector 304. The outlet of the mixing injector 304, the first stage positive para-hydrogen catalytic reactor 307, the second stage positive para-hydrogen catalytic reactor 314, and the third stage positive para-hydrogen catalytic reactor 315 are connected in sequence, and then connected to the liquid hydrogen storage tank 312 through a throttle valve 316.
The liquid phase pipeline at the bottom of the liquid hydrogen storage tank 312 is a liquid hydrogen product output port of the hydrogen liquefier, and the gas phase pipeline (gas phase loop) at the top of the liquid hydrogen storage tank 312 is led out and is returned to pass through the third-stage cryogenic heat exchanger 505, and then is connected with the low-pressure inlet of the bypass ejector 309. The pipeline between the second stage normal para-hydrogen catalytic reactor 314 and the third stage normal para-hydrogen catalytic reactor 315 is divided into a pipeline (a loop branch) and is connected with the high pressure inlet of the bypass ejector 309. The outlet of the bypass eductor 309, the second stage cryogenic heat exchanger 504 and the third stage cryogenic heat exchanger 505 are connected in sequence and then connected to the low pressure inlet of the cryogenic turbine compressor 305.
The high-pressure outlet of the low-temperature turbine compressor 305 is connected with an interface in the middle of the pre-cooling heat exchanger 400 through a pipeline, and is finally connected with a high-pressure inlet of the mixing injector 304 after being pre-cooled by the pre-cooling heat exchanger 400; the low temperature turbo compressor 305 is mechanically coupled to a first stage low temperature turbo expander 232 in the main refrigeration system 200 via a shaft, and the expansion power generated by the first stage low temperature turbo expander 232 in the main refrigeration process is used to drive the low temperature turbo compressor 305. A supplemental drive motor 306 is provided on the shaft of the cryogenic turbine compressor 305 mechanically coupled to the primary cryogenic turbine expander 232 in the main refrigeration system 200 for providing additional power to drive the cryogenic turbine compressor 305. In this embodiment, the operation principle of the liquefaction system 300 is the same as that of the liquefaction system 300 in embodiment 1.
Example 5:
as shown in fig. 5, a more detailed schematic of a hydrogen liquefaction system using a low temperature turbine compression cycle, a turbine brayton cycle refrigeration system for the cooling system 100, and a hydrogen claude cycle refrigeration system for the main refrigeration system 200 is different from embodiment 4 in that:
in this embodiment, the cooling system 100 is a turbo brayton cycle refrigeration system, the main refrigeration system 200 is a hydrogen claude cycle refrigeration system, and the low-temperature heat exchanger group 500 includes 6 low-temperature heat exchangers (first to sixth low-temperature heat exchangers) with temperatures ranging from high to low.
The turbo brayton cycle refrigeration system used in the cooling system 100 includes a low temperature turbo compressor I103, a water cooler 104, a low temperature turbo expander 105, and a high speed motor 106. The above-mentioned parts are connected in the following order: the high-pressure outlet of the low-temperature turbine compressor I103, the water cooler 104, the hot end inlet of the precooling heat exchanger 400, the cold end outlet of the precooling heat exchanger 400, the low-temperature turbine expander I105 inlet, the low-temperature turbine expander I105 outlet, the cold end inlet of the precooling heat exchanger 400, the hot end outlet of the precooling heat exchanger 400 and the low-pressure inlet of the low-temperature turbine compressor I103 are sequentially connected to form a loop.
The low-temperature turbine compressor I103 and the low-temperature turbine expander I105 are mechanically coupled through a shaft, and a high-speed motor 106 is arranged on the shaft. In this embodiment, the working principle of the turbine brayton cycle refrigeration system is as follows: the refrigerant is compressed to high pressure by a low-temperature turbine compressor I103, compression heat generated by compression is taken away by a water cooler 104 and cooled to about room temperature, and the compressed and cooled refrigerant enters a precooling heat exchanger 400 to be precooled to about 100-120K by the reflowed refrigerant; then the working medium enters a low-temperature turbine expander I105 for expansion refrigeration, and the temperature of the working medium can be finally reduced to about 80-100K according to the difference between the working medium and the pressure after expansion; the low-temperature low-pressure working medium returns to the pre-cooling heat exchanger 400 to pre-cool the inflow high-pressure working medium, the working medium of the main refrigeration cycle and the hydrogen of the liquefying system 300, and the working medium returns to the room temperature to leave the pre-cooling heat exchanger 400, and finally returns to the low-pressure inlet of the low-temperature turbine compressor I103. The high-speed motor 106 provides a main driving force to drive the low-temperature turbine compressor I103, and the expansion work of the low-temperature turbine expander I105 is recovered through the shaft to provide an auxiliary driving force for the low-temperature turbine compressor I103.
The hydrogen claude circulation refrigeration system used in the main refrigeration system 200 includes a first compressor 214 (working medium compressor), a first water cooler 215, a second compressor 216 (working medium compressor), a second water cooler 217, an oil removal system 213, a low temperature adsorption filter 221, a first low temperature turboexpander 232, a second low temperature turboexpander 233, and a throttle valve 234. The connection relation of the components is as follows: the primary compressor 214, the primary water cooler 215, the secondary compressor 216, the secondary water cooler 217, the oil removal system 213 and the hot end inlet of the pre-cooling heat exchanger 400 are connected in sequence through pipelines; after passing through the pre-cooling heat exchanger 400, the cold end outlet of the pre-cooling heat exchanger 400 is connected with the low-temperature adsorption filter 221, and then passes through the first-stage low-temperature heat exchanger 501;
the hydrogen pipeline is divided into two paths, wherein one path is firstly connected with the first-stage low-temperature turboexpander 232, then enters the second-stage low-temperature turboexpander 233 after passing through the third-stage low-temperature heat exchanger 505, finally is connected with the cold end inlet of the fourth-stage low-temperature heat exchanger 506, and sequentially returns to pass through the fourth-stage low-temperature heat exchanger 506, the third-stage low-temperature heat exchanger 505, the second-stage low-temperature heat exchanger 504, the first-stage low-temperature heat exchanger 501 and the pre-cooling heat exchanger 400, and finally enters the pipeline between the first-stage water cooler 215 and the second-stage compressor 216;
The other path sequentially passes through a second-stage low-temperature heat exchanger 504, a third-stage low-temperature heat exchanger 505, a fourth-stage low-temperature heat exchanger 506 and a fifth-stage low-temperature heat exchanger 507 and is connected with a throttle valve 234; the outlet of the throttle valve 234 is connected with the cold end inlet of the sixth-stage cryogenic heat exchanger 508 through a pipeline, then sequentially returns to pass through the sixth-stage cryogenic heat exchanger 508, the fifth-stage cryogenic heat exchanger 507, the fourth-stage cryogenic heat exchanger 506, the third-stage cryogenic heat exchanger 505, the second-stage cryogenic heat exchanger 504, the first-stage cryogenic heat exchanger 501 and the pre-cooling heat exchanger 400, and finally is connected with the low-pressure inlet of the first-stage compressor 214.
The principle of operation of the main refrigeration system 200 employing the hydrogen claude cycle refrigeration system is as follows: the room temperature low pressure hydrogen working medium returned from the pre-cooling heat exchanger 400 enters the primary compressor 214 to be compressed to medium pressure, is cooled to room temperature through the primary water cooler 215, enters the secondary compressor 216 to be further compressed to high pressure, is cooled to room temperature through the secondary water cooler 217, and then enters the oil removing system 213 to remove most of oil gas impurities in the working medium; the compressed, cooled and deoiled high-pressure hydrogen enters the pre-cooling heat exchanger 400 to be pre-cooled to about 77-100K.
Then removing the residual particulate matter impurities solidified at low temperature through the low temperature adsorption filter 221; the hydrogen leaves the low-temperature adsorption filter 221 and then enters the first-stage low-temperature heat exchanger 501 for precooling, then the hydrogen is divided into two paths, one path enters the first-stage low-temperature turbine expander 232 for expansion refrigeration, the temperature is reduced by 5-10K, then enters the third-stage low-temperature heat exchanger 505 for further precooling, then enters the second-stage low-temperature turbine expander 233 for expansion refrigeration, the temperature is reduced by 5-10K again, the pressure is reduced to medium pressure, then returns to the fourth-stage low-temperature heat exchanger 506, the third-stage low-temperature heat exchanger 505, the second-stage low-temperature heat exchanger 504, the first-stage low-temperature heat exchanger 501 and the precooling heat exchanger 400 for cooling the high-pressure hydrogen and the hydrogen of the liquefaction system 300, and finally the hydrogen working medium flows between the first-stage water cooler 215 and the second-stage compressor 216;
the other path is further precooled to about 20K through a second-stage low-temperature heat exchanger 504, a third-stage low-temperature heat exchanger 505, a fourth-stage low-temperature heat exchanger 506 and a fifth-stage low-temperature heat exchanger 507, isenthalpic throttling refrigeration is finally carried out through a throttle valve 234, the temperature of hydrogen is continuously reduced to 18-20K and is partially liquefied, then the low-temperature low-pressure hydrogen is sequentially returned to the sixth-stage low-temperature heat exchanger 508, the fifth-stage low-temperature heat exchanger 507, the fourth-stage low-temperature heat exchanger 506, the third-stage low-temperature heat exchanger 505, the second-stage low-temperature heat exchanger 504, the first-stage low-temperature heat exchanger 501 and the precooling heat exchanger 400 to cool the inflowing high-pressure hydrogen and the hydrogen of the liquefaction system 300, and finally the low-pressure inlet of the first-stage compressor 214 is returned to be compressed and circulated again.
In this embodiment, the components, connection modes, and operation principles of the liquefaction system 300 are the same as those of embodiment 4.

Claims (10)

1. The hydrogen liquefaction system adopting the low-temperature turbine compression cycle comprises a liquefaction system, a low-temperature heat exchanger group, a precooling system and a main refrigeration system for providing a cold source for the low-temperature heat exchanger group;
the liquefaction system comprises a positive para-hydrogen catalytic reactor I and n-level positive para-hydrogen catalytic reactors connected with the positive para-hydrogen catalytic reactor I in series in sequence; the low-temperature heat exchanger group comprises n-level low-temperature heat exchangers which respectively perform refrigeration and heat exchange on n-level normal-para-hydrogen catalytic reactors; the precooling system provides precooling cooling capacity for the primary and secondary hydrogen catalytic reactor I and the main refrigerating system respectively;
the device is characterized by further comprising a mixing ejector, a one-shaft driving compressor and a throttling element;
the main refrigeration system comprises at least one turboexpander, and an output shaft of the turboexpander is in transmission connection with the shaft-driven compressor;
a reflux branch is led out from a pipeline of a discharge port of the n-1-level normal-para-hydrogen catalytic reactor, and working medium in the reflux branch sequentially passes through throttling element throttling, at least one low-temperature heat exchanger for heat exchange, a shaft-driven compressor for compression and precooling system for precooling and then enters the mixing ejector as high-pressure fluid; or the working medium of the reflux branch sequentially passes through throttling element throttling and at least one low-temperature heat exchanger for heat exchange to be used as low-pressure fluid to enter the mixing ejector;
When the working medium is used as high-pressure fluid, the material at the outlet of the n-stage para-hydrogen catalytic reactor I is used as low-pressure fluid to enter the mixing ejector, and the materials are mixed and then sequentially enter the n-stage para-hydrogen catalytic reactor; when the working medium is used as low-pressure fluid, the material at the outlet of the normal-para-hydrogen catalytic reactor I is used as high-pressure fluid to enter the mixing ejector, and the mixed material is compressed by the shaft-driven compressor and precooled by the precooling system and then sequentially enters the n-level normal-para-hydrogen catalytic reactor.
2. The hydrogen liquefaction system of claim 1, wherein the throttling element is an expander, a throttle valve, or a bypass eductor.
3. The hydrogen liquefaction system of claim 2, further comprising a liquid hydrogen storage tank connected to the nth stage normal para-hydrogen catalytic reactor by piping;
the throttling element is a bypass ejector, and the backflow branch is connected with a high-pressure inlet of the bypass ejector; and a gas phase outlet of the liquid hydrogen storage tank is connected with a low pressure inlet of the bypass ejector through a gas phase loop.
4. A hydrogen liquefaction system according to claim 3 wherein the gas phase circuit is connected to the low pressure inlet of the bypass eductor after heat exchange in the nth stage cryogenic heat exchanger.
5. The hydrogen liquefying system according to claim 4, wherein the working medium at the outlet of the bypass ejector exchanges heat with the n-1 st cryogenic heat exchanger in sequence.
6. A hydrogen liquefaction system according to claim 3, wherein the gas phase circuit is directly connected to the low pressure inlet of the bypass eductor.
7. The hydrogen liquefaction system of claim 6, wherein the working fluid at the outlet of the bypass ejector sequentially passes through the nth-1 cryogenic heat exchanger to exchange heat.
8. The hydrogen liquefaction system of claim 1, wherein a compensation drive motor is provided on a shaft connecting the expander and the compressor.
9. The hydrogen liquefaction system of claim 1, wherein the working fluid in the return branch is sequentially heat exchanged with an n-1 st cryogenic heat exchanger.
10. The hydrogen liquefaction system of claim 1, wherein the pre-cooling system comprises a pre-cooling heat exchanger and a cooling system for providing a cold source for the pre-cooling heat exchanger, and the pre-cooling heat exchanger provides cold for the primary and secondary hydrogen catalytic reactor i and the main refrigeration system, respectively.
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