CN108759301B

CN108759301B - Hydrogen liquefaction process

Info

Publication number: CN108759301B
Application number: CN201810524157.2A
Authority: CN
Inventors: 况开锋; 倪中华; 严岩; 魏蔚; 郭道峰; 邬海强; 王秋霞
Original assignee: Jiangsu Guofu Hydrogen Energy Technology Equipment Co Ltd
Current assignee: Jiangsu Guofu Hydrogen Energy Technology Equipment Co Ltd
Priority date: 2018-05-28
Filing date: 2018-05-28
Publication date: 2020-06-02
Anticipated expiration: 2038-05-28
Also published as: CN108759301A

Abstract

The invention discloses a hydrogen liquefaction process, which comprises the following steps: firstly, compressing and purifying raw material hydrogen; then the compressed and purified gaseous hydrogen is subjected to normal-secondary conversion of the gaseous hydrogen; then the mixed liquid hydrogen is subjected to liquid hydrogen positive-secondary conversion, the liquid hydrogen is stored in a liquid hydrogen storage tank, and the gasified low-temperature gaseous hydrogen in the liquid hydrogen storage tank is recycled in the liquefaction process flow, so that the energy consumption for hydrogen liquefaction is reduced, and the cost is reduced. The high-purity liquid hydrogen can be obtained by adopting the hydrogen liquefaction process, the concentration of parahydrogen in the liquid hydrogen is not lower than 98 percent, the concentration of orthohydrogen which can spontaneously generate orthohydrogen and parahydrogen conversion in the liquid hydrogen is effectively reduced, the evaporation loss of the liquid hydrogen is small, and the potential safety hazard is small.

Description

Hydrogen liquefaction process

Technical Field

The invention relates to a hydrogen liquefaction technology, in particular to a hydrogen liquefaction process.

Background

With the development of industry and the improvement of people's living standard of matter, the demand of energy is increasing day by day. As the fossil energy such as coal, petroleum and the like inevitably pollutes the environment when being used and the reserves thereof are limited, people face a great challenge of developing efficient and clean secondary energy, so that the search for renewable green energy is urgent. Hydrogen is an ideal energy carrier which can be obtained from various ways, is one of important bridges for the transition from fossil energy to renewable energy, and provides a new important form for terminal energy utilization.

The utilization of hydrogen energy needs to solve a series of problems of preparation, storage and transportation, which are important keys for the application of hydrogen energy, and application. Current hydrogen energy utilization is generally "produced on site, consumed on site" due primarily to hydrogen storage and transportation difficulties. At present, there are two main ways of hydrogen storage: high-pressure gaseous storage and low-temperature liquid storage, the high-pressure gaseous storage is the most common and direct hydrogen storage method, and hydrogen is stored in a storage tank under pressure, but the hydrogen storage capacity of the hydrogen storage method is small, a thick and heavy pressure-resistant storage tank is required, and the transportation cost is very high. The cryogenic liquid storage technology is still immature at present, and since the past half century, many researchers have conducted a great deal of theoretical and experimental research around improving the efficiency of hydrogen liquefaction and reducing the cost of liquefaction. However, in the aspect of large-scale industrial demand, the main problems of the current hydrogen liquefaction technology are low liquefaction efficiency and large investment.

Disclosure of Invention

The liquid hydrogen is obtained by cooling hydrogen gas, is a colorless, tasteless, high-energy and low-temperature liquid fuel, and is a mixture of parahydrogen (p-H2) and orthohydrogen (o-H2). Orthohydrogen and parahydrogen are two spin isomers of molecular hydrogen, which are caused by two possible couplings of nuclear spins of two hydrogen atoms. The spins of the two nuclei in orthohydrogen are parallel, and the spins of the two nuclei in parahydrogen are antiparallel. The magnetic moment of para-hydrogen molecules is zero and the magnetic moment of ortho-hydrogen molecules is twice the magnetic moment of protons. Para-hydrogen is chemically identical to ortho-hydrogen, while the physical properties are different, as para-hydrogen has a lower ground state energy than ortho-hydrogen. At or above room temperature, the equilibrium composition of normal and para-hydrogen is 75:25, referred to as normal hydrogen (n-H2) or normal hydrogen. Below ambient temperature, the equilibrium composition of para-ortho will change and the percentage of para-para increases. The ortho-para conversion of gaseous hydrogen occurs in the presence of a catalyst, while liquid hydrogen spontaneously undergoes ortho-para conversion from ortho-hydrogen to para-hydrogen in the absence of a catalyst. The positive-secondary conversion of liquid hydrogen is an exothermic reaction, and the heat evolved during the conversion is related to the temperature at which the conversion takes place. In order to reduce the evaporative loss of liquid hydrogen due to the exothermic heat of conversion of ortho-para-hydrogen, it is desirable that the para-hydrogen content of all liquid hydrogen products be at least 95% or greater, i.e., that essentially all ortho-hydrogen be catalytically converted to para-hydrogen upon liquefaction.

The technical problems to be solved by the invention are as follows: the hydrogen liquefying process is safe and reliable, can recycle low-temperature gaseous hydrogen gasified in a liquid hydrogen storage tank, and has low energy consumption, and the concentration of parahydrogen in the liquid hydrogen obtained by adopting the hydrogen liquefying process is not lower than 98%.

In order to solve the problems, the invention adopts the technical scheme that: the hydrogen liquefaction process comprises the following specific steps:

(1) compressing and purifying the raw material hydrogen: firstly, raw material hydrogen is compressed into gaseous hydrogen with the pressure of 2.5 +/-0.25 MPa by a first compressor unit; then adsorbing the oil in the gaseous hydrogen by an oil purification adsorber to ensure that the volume content of the oil in the gaseous hydrogen is not more than 10 ppbV; carrying out catalytic refining on the gaseous hydrogen to remove oxygen impurities in the gaseous hydrogen, so that the volume content of the oxygen impurities in the gaseous hydrogen is not more than 2 ppbV; drying gaseous hydrogen to ensure that the volume content of water in the gaseous hydrogen is not more than 1ppmV, and controlling the temperature of the gaseous hydrogen obtained after drying treatment to be between-100 ℃ and-70 ℃ condensation point temperature; then CO in the gaseous hydrogen is treated by an adsorber capable of removing high boiling point impurities₂、H₂S and high boiling point impurities are adsorbed to ensure that CO in the gaseous hydrogen₂、H₂The total volume content of S and high boiling point impurities is not more than 1 ppmV;

(2) carrying out normal-secondary conversion on the compressed and purified gaseous hydrogen: precooling the compressed and purified gaseous hydrogen to 102.7 +/-10K by a heat exchanger A, then entering a first hydrogen channel of a first reactor, then outputting the gaseous hydrogen from an air outlet of the first hydrogen channel, and returning the gaseous hydrogen to enter a first positive-secondary conversion channel of the first reactor for positive-secondary conversion of the gaseous hydrogen to obtain mixed liquid hydrogen with the temperature of 81.2 +/-5K and the concentration of secondary hydrogen of 46.3-55 percent; wherein, the cold energy in the heat exchanger A is provided by liquid nitrogen and low-temperature circulating hydrogen;

(3) performing liquid hydrogen positive-secondary conversion on the mixed liquid hydrogen: the mixed liquid hydrogen output from the gas outlet of the first positive-secondary conversion channel of the first reactor returns to the first liquid hydrogen channel of the first reactor, then is output from the gas outlet of the first liquid hydrogen channel, is sequentially subjected to stepped cooling to 23.6 +/-10K through a heat exchanger B, a heat exchanger C, a heat exchanger D, a heat exchanger E, a heat exchanger F and a throttling expansion valve, enters a second liquid hydrogen channel of the second reactor, is output from the gas outlet of the second liquid hydrogen channel, and then returns to the second positive-secondary conversion channel of the second reactor for liquid hydrogen positive-secondary conversion, so that liquid hydrogen with the temperature of 2.13K-5K and the secondary hydrogen concentration of not less than 98% is obtained;

(4) liquid hydrogen storage: the liquid hydrogen output from the gas outlet of the second positive-secondary conversion channel of the second reactor returns to a third liquid hydrogen channel of the second reactor, and then the liquid hydrogen output from the gas outlet of the third liquid hydrogen channel is stored in a liquid hydrogen storage tank; the low-temperature gaseous hydrogen gasified in the liquid hydrogen storage tank enters the previous process in two paths: the first path of low-temperature gaseous hydrogen is converged with the mixed liquid hydrogen entering the throttle expansion valve through the throttle expansion valve; the second path of low-temperature gaseous hydrogen is compressed into low-temperature gaseous hydrogen with the pressure of 2.5 +/-0.25 MPa by a second compressor unit, then sequentially enters a heat exchanger A, a first reactor, a third compressor unit and a heat exchanger B, and then is divided into two paths of circulating hydrogen to enter a previous process: one path of circulating hydrogen sequentially passes through the heat exchanger C, the heat exchanger D, the heat exchanger E, the heat exchanger F and the second reactor and then returns to the heat exchanger F, and then sequentially passes through the heat exchanger E, the heat exchanger D, the heat exchanger C, the heat exchanger B and the heat exchanger A and then is merged with a second path of low-temperature gaseous hydrogen to enter a second compressor unit to form a first path of hydrogen refrigeration circulating loop; the other path of circulating hydrogen enters a heat exchanger D after being compressed and expanded by a second turbo expansion unit, then enters a heat exchanger E after being compressed and expanded by a third turbo expansion unit, then returns to the heat exchanger D, the heat exchanger C, the heat exchanger B and the heat exchanger A in sequence, is converged with the second path of low-temperature gaseous hydrogen and then enters the second compressor unit to form a second path of hydrogen refrigeration circulating loop; the circulating hydrogen in the first hydrogen refrigeration circulating loop, the circulating hydrogen in the second hydrogen refrigeration circulating loop and the second low-temperature liquid hydrogen are converged to form low-temperature circulating hydrogen, and the low-temperature circulating hydrogen provides cold for the heat exchanger A, the first reactor, the heat exchanger B, the heat exchanger C, the heat exchanger D, the heat exchanger E, the heat exchanger F and the second reactor; the expansion pressure at the outlet of the second turboexpander set is 1.58mpa, and the expansion pressure at the outlet of the third turboexpander set is 0.25 mpa.

Further, in the hydrogen liquefaction process, the first compressor set in the step (1) is composed of a first low-pressure compressor and a first high-pressure compressor, the raw material hydrogen is compressed into gaseous hydrogen with the pressure of 0.29 ± 0.029MPa by the first low-pressure compressor, and then compressed into gaseous hydrogen with the pressure of 2.5 ± 0.25MPa by the first high-pressure compressor; the second compressor set in the step (4) is composed of a second low-pressure compressor and a second high-pressure compressor, low-temperature circulating hydrogen is compressed into low-temperature circulating hydrogen with the pressure of 0.29 +/-0.029 MPa by the second low-pressure compressor, and then compressed into low-temperature circulating hydrogen with the pressure of 2.5 +/-0.25 MPa by the second high-pressure compressor; the third compressor set is composed of a third low-pressure compressor and a third high-pressure compressor, low-temperature circulating hydrogen output from the first reactor is compressed into low-temperature circulating hydrogen with the pressure of 0.29MPa +/-10% by the third low-pressure compressor, and then compressed into low-temperature circulating hydrogen with the pressure of 2.5 +/-0.25 MPa by the third high-pressure compressor.

Further, in the hydrogen liquefaction process, the first low-pressure compressor in the step (1) is a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the first high-pressure compressor is a high-pressure unit-dry piston multi-stage compressor; the second low-pressure compressor in the step (4) is a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the second high-pressure compressor is a high-pressure unit-dry piston multi-stage compressor; the third low-pressure compressor is a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the third high-pressure compressor is a high-pressure unit-dry piston multi-stage compressor.

Further, in the hydrogen liquefaction process, the adsorbent of the absolute oil adsorber in the step (1) is activated carbon; the catalyst used for catalytic refining is a metal catalyst, and the metal catalyst is one of platinum, nickel and palladium.

Further, in the hydrogen liquefaction process, the adsorbent of the adsorber capable of removing the high boiling point impurities in the step (1) is thermally regenerable fine pore zeolite, and the gaseous hydrogen is dried by the thermally regenerable fine pore zeolite.

Further, in the aforementioned hydrogen liquefaction process, the compressed and purified gaseous hydrogen is continuously sampled and analyzed in step (1).

Further, in the hydrogen liquefaction process, the gaseous hydrogen compressed and purified in the step (2) is precooled to 102.7 ± 10K by the heat exchanger a, enters the first hydrogen channel of the first reactor, is output from the gas outlet of the first hydrogen channel, is adsorbed by the low-temperature dual-unit conversion adsorber, and is returned to the first positive-secondary conversion channel of the first reactor for positive-secondary conversion of the gaseous hydrogen, so that mixed liquid hydrogen with the temperature of 81.2 ± 5K and the secondary hydrogen concentration of 46.3% -55% is obtained; the low-temperature double-unit conversion adsorber consists of a first adsorber and a second adsorber, and the adsorbents in the first adsorber and the second adsorber can be thermally regenerated; when the compressed and purified gaseous hydrogen is subjected to adsorption treatment by the first adsorber, the second adsorber is thermally regenerated; when the compressed and purified gaseous hydrogen is subjected to adsorption treatment by the second adsorber, the first adsorber is thermally regenerated; and (4) compressing the low-temperature circulating hydrogen in the step (4) into low-temperature circulating hydrogen with the pressure of 2.5MPa +/-10% through a second compressor unit, and then sequentially entering a heat exchanger A, a first reactor and a third adsorber and then entering a third compressor unit.

Further, in the hydrogen liquefaction process, the liquid nitrogen in the step (2) is prepared by a liquid nitrogen precooling process, and the liquid nitrogen precooling process specifically includes the following steps:

(1) the raw material nitrogen is preliminarily pressurized to gaseous nitrogen with the pressure of 0.9Mpa and the temperature of 300K-313K through a compressor;

(2) conveying the preliminarily pressurized gaseous nitrogen to a K loop in a KT turbine expansion compressor for secondary pressurization, expansion throttling and cooling to obtain gaseous nitrogen with the pressure of 0.128-0.13 MPa and the temperature of 120K +/-5K;

(3) feeding the gaseous nitrogen subjected to secondary pressurization, expansion throttling and temperature reduction into a first heat exchanger for primary cooling liquefaction treatment to obtain a gas-liquid mixture of the gaseous nitrogen and liquid nitrogen at the temperature of 79.2K +/-2K; conveying unliquefied gaseous nitrogen in the gas-liquid mixture into a T loop in a KT turbine expansion compressor for expansion throttling and cooling, then converging the unliquefied gaseous nitrogen with the gaseous nitrogen separated from the gas-liquid separator, and then conveying the unliquefied gaseous nitrogen into a second heat exchanger and a first heat exchanger in sequence to provide cold energy for the second heat exchanger and the first heat exchanger and then returning the unliquefied gaseous nitrogen into the compressor again for preliminary pressurization; conveying liquefied liquid nitrogen in the gas-liquid mixture to a second heat exchanger for secondary cooling liquefaction treatment, and conveying the liquefied liquid nitrogen to a gas-liquid separator for gas-liquid separation to obtain liquid nitrogen with the pressure of 0.123-0.128 MPa and the temperature of 70K-79.2K;

(4) conveying the liquid nitrogen obtained after gas-liquid separation into a first cold box in a hydrogen gasification device, providing cold energy for the first cold box, and returning the cold energy to the compressor again for preliminary pressurization; wherein the temperature of the liquid nitrogen entering the first cold box is 70K-79.2K;

(5) and circulating the steps.

Further, in the hydrogen liquefaction process, the oil-free centrifugal compressor, the first compressor unit, the second compressor unit and the third compressor unit are respectively cooled by water or air.

Further, in the aforementioned hydrogen liquefaction process, the heat exchanger a, the first reactor, the heat exchanger B, the heat exchanger C, the heat exchanger D, the heat exchanger E, the heat exchanger F, and the second reactor are respectively provided with a temperature sensor, a pressure sensor, and a flow sensor; a hydrogen safety sensor and a smoke sensor are arranged in the hydrogen liquefaction process environment, and the hydrogen safety sensor and the smoke sensor are respectively connected with a control device for controlling the hydrogen liquefaction process flow.

③ the ③ hydrogen ③ liquefying ③ process ③ has ③ the ③ advantages ③ that ③ high ③ - ③ purity ③ liquid ③ hydrogen ③ can ③ be ③ obtained ③ by ③ the ③ hydrogen ③ liquefying ③

process

③, ③ the ③ concentration ③ of ③ para ③ - ③ hydrogen ③ in ③ the ③ liquid ③ hydrogen ③ is ③ not ③ lower ③ than ③ 98 ③% ③, ③ the ③ concentration ③ of ③ normal ③ hydrogen ③ which ③ can ③ spontaneously ③ generate ③ normal ③ - ③ secondary ③ conversion ③ in ③ the ③ liquid ③ hydrogen ③ is ③ effectively ③ reduced ③, ③ the ③ evaporation ③ loss ③ of ③ the ③ liquid ③ hydrogen ③ is ③ small ③, ③ the ③ blockage ③ phenomenon ③ of ③ each ③ gas ③

channel

③, ③ liquid ③

channel

③ and ③ pipeline ③ in ③ the ③ hydrogen ③ liquefying ③ device ③ depending ③ on ③ the ③ hydrogen ③ liquefying ③ process ③ is ③ not ③ easy ③ to ③ occur ③, ③ the ③ potential ③ safety ③ hazard ③ is ③ reduced ③, ③ the ③ low ③ - ③ temperature ③ gaseous ③ hydrogen ③ gasified ③ in ③ the ③ liquid ③ hydrogen ③ storage ③ tank ③ can ③ be ③ recycled ③, ③ the ③ potential ③ safety ③

hazard

③ and ③ energy ③ waste ③ caused ③ by ③ directly ③ releasing ③ the ③ low ③ - ③ temperature ③ gaseous ③ hydrogen ③ can ③ be ③ avoided ③, ③ cold ③ energy ③ can ③ be ③ provided ③ for ③ hydrogen ③ liquefying ③, ③ the ③ energy ③ consumption ③ required ③ by ③ hydrogen ③ liquefying ③ is ③ reduced ③, ③ the ③ cost ③ is ③ reduced ③, ③ the ③ cold ③ energy ③ is ③ provided ③ for ③ the ③ first ③ reactor ③ through ③ the ③ nitrogen ③ refrigerating ③ circulation ③

loop

③, ③ the ③ first ③ hydrogen ③ refrigerating ③ circulation ③

loop

③ and ③ the ③ second ③ hydrogen ③ refrigerating ③ circulation ③

loop

③, ③ the ③ liquid ③ nitrogen ③ consumption ③ is ③ reduced ③ by ③ about ③ 30 ③% ③ compared ③ with ③ the ③ traditional ③ nitrogen ③ refrigerating ③ circulation ③

loop

③, ③ and ③ the ③ energy ③ consumption ③ required ③ by ③ hydrogen ③ liquefying ③ is ③ further ③ reduced ③, ③ and ③ the ③ cost ③ is ③ reduced ③. ③

Drawings

Fig. 1 is a schematic configuration diagram of a hydrogen liquefying apparatus.

Fig. 2 is a schematic diagram of a connection structure of the first compressor unit, the purification device, the liquid nitrogen pre-cooling device and the first cold box in fig. 1.

Fig. 3 is a schematic structural view of the first cold box of fig. 2.

Fig. 4 is a schematic structural diagram of the liquid nitrogen precooling apparatus in fig. 1.

Fig. 5 is a schematic view of a connection structure of the second cooling box, the liquid hydrogen storage tank and the throttle expansion valve in fig. 1.

Fig. 6 is a schematic view showing a connection structure of the heat exchanger B, the heat exchanger C and the second turbo expander set in fig. 5.

Fig. 7 is a schematic view showing a connection structure of the heat exchanger D, the heat exchanger E and the third turbo-expander set in fig. 5.

FIG. 8 is a schematic view showing a connection structure of the heat exchanger F to the second reactor in FIG. 5.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to the accompanying drawings and preferred embodiments.

The hydrogen liquefaction process depends on a hydrogen liquefaction device, so the hydrogen liquefaction device needs to be designed and manufactured firstly. As shown in fig. 1, the hydrogen liquefying apparatus has the following structure: the system comprises a first compressor set, a purification device, a first cold box 101, a second cold box 102, a throttle expansion valve, a liquid hydrogen storage tank, a liquid nitrogen precooling device, a second compressor set and a third compressor set 9.

The first compressor unit comprises: the first low-pressure compressor can adopt a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the first high-pressure compressor can adopt a high-pressure unit-dry piston multi-stage compressor.

The purification device comprises: a clean oil adsorber, a catalytic refining device, a drying device and an adsorber capable of removing high boiling point impurities. In the oil purification adsorber, the adsorbent is activated carbon, and the activated carbon cannot be regenerated, so that the activated carbon needs to be replaced periodically. The catalyst used in the catalytic refining device is a metal catalyst, the metal catalyst is one of platinum, nickel and palladium, and the surface of the carrier subjected to catalytic refining is usually set as an extended surface, and the extended surface is uniformly coated with the metal catalyst. The pore zeolite is arranged in the drying device, can be heated and regenerated, and can be used for drying the gaseous hydrogen through the pore zeolite which can be thermally regenerated, wherein the pore zeolite can be heated in a mode of indirect electric heating such as a heat carrier, and the like, so that the potential safety hazard can be reduced.

As shown in fig. 2 and 3, the first cold box 101 includes: heat exchanger a1, first reactor 2, first adsorber 301 capable of purging impurities, second adsorber 302 capable of purging impurities, and third adsorber 303 capable of purging impurities. The heat exchanger A1 is provided with a hydrogen channel A11, a first liquid nitrogen channel 12, a circulating hydrogen channel A13, a first circulating hydrogen return channel A14 and a second circulating hydrogen return channel A, wherein the hydrogen channel A11, the first liquid nitrogen channel 12, the circulating hydrogen channel A13, the first circulating hydrogen return channel A14 and the second circulating hydrogen return channel A are independent and do not interfere with each other. The first reactor 2 is provided with a second liquid nitrogen channel, a first hydrogen channel 21, a first positive-secondary conversion channel 22, a first liquid hydrogen channel 23 and a first circulating hydrogen channel 24, wherein the second liquid nitrogen channel, the first hydrogen channel 21, the first positive-secondary conversion channel 22, the first liquid hydrogen channel 23 and the first circulating hydrogen channel 24 are mutually independent and do not interfere with each other.

As shown in fig. 4, 5, 6 and 7, the second cold box 102 includes: heat exchanger B3, heat exchanger C4, heat exchanger D5, heat exchanger E6, heat exchanger F7, second reactor 8, a second turboexpander train, and a third turboexpander train. The heat exchanger B3 is provided with a liquid hydrogen channel B31, a circulating hydrogen channel B32, a first circulating hydrogen return channel B33 and a second circulating hydrogen return channel B, and the liquid hydrogen channel B31, the circulating hydrogen channel B32, the first circulating hydrogen return channel B33 and the second circulating hydrogen return channel B are independent and do not interfere with each other. The heat exchanger C4 is provided with a liquid hydrogen channel C41, a circulating hydrogen channel C42, a first circulating hydrogen return channel C43 and a second circulating hydrogen return channel C, and the liquid hydrogen channel C41, the circulating hydrogen channel C42, the first circulating hydrogen return channel C43 and the second circulating hydrogen return channel C are independent and do not interfere with each other. The heat exchanger D5 is provided with a liquid hydrogen channel D51, a circulating hydrogen channel D52, a first circulating hydrogen return channel D53, a second circulating hydrogen return channel D and a hydrogen expansion channel 54, wherein the liquid hydrogen channel D51, the circulating hydrogen channel D52, the first circulating hydrogen return channel D53, the second circulating hydrogen return channel D and the hydrogen expansion channel 54 are mutually independent and do not interfere with each other. The heat exchanger E6 is provided with a liquid hydrogen channel E61, a circulating hydrogen channel E62, a first circulating hydrogen return channel E63 and a second circulating hydrogen return channel E, and the liquid hydrogen channel E61, the circulating hydrogen channel E62, the first circulating hydrogen return channel E63 and the second circulating hydrogen return channel E are mutually independent and mutually noninterfere. The heat exchanger F7 is provided with a liquid hydrogen channel F71, a circulating hydrogen channel F72 and a first circulating hydrogen return channel F, and the liquid hydrogen channel F71, the circulating hydrogen channel F72 and the first circulating hydrogen return channel F are independent and do not interfere with each other. The second reactor 8 is provided with a second liquid hydrogen channel 81, a second positive and secondary conversion channel 82, a third liquid hydrogen channel 83 and a first circulating hydrogen gas return channel G, and the second liquid hydrogen channel 81, the second positive and secondary conversion channel 82, the third liquid hydrogen channel 83 and the first circulating hydrogen gas return channel G are independent and do not interfere with each other.

As shown in fig. 4, the liquid nitrogen precooling apparatus includes: a compressor 601 and a nitrogen liquefaction cold box 600. The nitrogen liquefaction cold box 600 comprises: a KT turboexpansion compressor 602, a first heat exchanger 603, a second heat exchanger 604 and a gas-liquid separator 605. Here, the compressor 601 may be an oil-free centrifugal turbo compressor.

The first heat exchanger 603 is provided with a nitrogen gas channel and a first circulation channel, which are independent from each other and do not interfere with each other. The second heat exchanger 604 is provided with a liquid nitrogen channel and a second circulation channel, which are independent and do not interfere with each other.

As shown in fig. 4, the raw material nitrogen is connected to the K loop of the compressor 601 and the KT expansion compressor 602 in sequence through the first nitrogen connecting pipe 701 and the inlet of the nitrogen channel in the first heat exchanger 603, the first branch nitrogen pipe 702 and the second branch nitrogen pipe 703 are arranged at the outlet of the nitrogen channel, and the gas-liquid mixture output from the nitrogen channel in the first heat exchanger 603 enters the subsequent process in two paths, wherein one path is: the liquefied liquid nitrogen in the nitrogen channel is sequentially connected with the liquid nitrogen channel in the second heat exchanger 604 and the gas-liquid separator 605 through a first branch nitrogen pipeline 702, and the liquid nitrogen outlet of the gas-liquid separator 605 is sequentially connected with the first cold box 101 and the compressor 601 through a second nitrogen connecting pipeline 704 to form a first nitrogen refrigeration cycle loop. The other path is as follows: the unliquefied gaseous nitrogen in the nitrogen channel is sequentially connected with a T loop of the KT turbine expansion compressor 602, a second circulation channel in the second heat exchanger 604, a first circulation channel in the first heat exchanger 603 and the compressor 601 through a second branch nitrogen pipeline 703 to form a second nitrogen refrigeration circulation loop. In actual use, gaseous nitrogen separated by gasification from the gas-liquid separator 605 is also recycled to the liquid nitrogen precooling apparatus, and the nitrogen outlet of the gas-liquid separator 605 is connected to the inlet of the second circulation passage of the second heat exchanger 604 through the third connecting nitrogen pipe 705.

In actual use, in order to facilitate control of the liquid nitrogen precooling apparatus, a third stop valve 606 is provided on the first branch nitrogen gas pipe 702 between the gas outlet of the liquid nitrogen passage in the second heat exchanger 604 and the gas-liquid separator 605, and the third stop valve 606 is used for adjusting the flow rate, shutting off the first branch nitrogen gas pipe 702 between the liquid nitrogen passage and the gas-liquid separator 5, and the like. A fourth stop valve 607 is arranged on the second connecting nitrogen pipe 704 between the liquid nitrogen outlet of the gas-liquid separator 605 and the first cold box 101, and the fourth stop valve 607 can be used for adjusting the flow rate, cutting off the second connecting nitrogen pipe 704 between the liquid nitrogen outlet of the gas-liquid separator 605 and the first cold box 101, and the like.

In the practical use process, a third branch nitrogen pipeline is further arranged on the second connecting nitrogen pipeline 704 between the liquid nitrogen outlet of the gas-liquid separator 605 and the first cold box 101 and is connected with at least one liquid nitrogen storage tank, so that sufficient cooling medium, namely liquid nitrogen, can be supplied to the first cold box 101 even if the liquid nitrogen precooling device is shut down briefly.

The second compressor unit comprises: the second low-pressure compressor can adopt a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the second high-pressure compressor can adopt a high-pressure unit-dry piston multi-stage compressor.

The third compressor unit comprises: the third low-pressure compressor can adopt a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the third high-pressure compressor can adopt a high-pressure unit-dry piston multi-stage compressor.

Referring to fig. 1 and 2, a raw material hydrogen is connected to a first low-pressure compressor, a first high-pressure compressor, an oil purification adsorber, a catalytic refining device, a drying device, an adsorber capable of removing high-boiling impurities, a hydrogen channel a11 in a heat exchanger a1, and an air inlet of a first hydrogen channel 21 in a first reactor 2 in sequence through a hydrogen conveying pipeline 201, an air outlet of the first hydrogen channel 21 is connected to an air inlet of a first positive-secondary conversion channel 22 through a first connecting pipeline 202, an air outlet of the first positive-secondary conversion channel 22 is connected to an air inlet of a first liquid hydrogen channel 23 through a second connecting pipeline 203, an air outlet of the first liquid hydrogen channel 23 is connected to a liquid hydrogen channel B31 in a heat exchanger B3, a liquid hydrogen channel C41 in a heat exchanger C4, a liquid hydrogen channel D51 in a heat exchanger D5, a liquid hydrogen channel E61 in a heat exchanger E6 in a sequence through, A liquid hydrogen channel F71 in the heat exchanger F7, a throttle expansion valve and an air inlet of a second liquid hydrogen channel 81 in the second reactor 8 are connected, an air outlet of the second liquid hydrogen channel 81 is connected with an air inlet of a second positive secondary conversion channel 82 through a third connecting pipeline 205, an air outlet of the second positive secondary conversion channel 82 is connected with an air inlet of a third liquid hydrogen channel 83 through a fourth connecting pipeline 206, and an air outlet of the third liquid hydrogen channel 83 is connected with a liquid hydrogen storage tank through a fifth connecting pipeline 207.

Referring to fig. 1 and 2, a low-temperature duplex shift adsorber is further provided on the first connection pipe 202, and is composed of a first adsorber 301 and a second adsorber 302, and the first adsorber 301 and the second adsorber 302 can remove low-boiling impurities such as N₂CO and fine purification of high boiling point impurities. The adsorbents in the first adsorber 301 and the second adsorber 302 are fine-pore zeolite capable of thermal regeneration; when the low-temperature double-unit conversion adsorber works normally, if the first adsorber 301 works normally, the second adsorber 302 is thermally regenerated; conversely, if the second adsorber 302 is operating normally, the first adsorber 301 is thermally regenerated. The first adsorber 301 and the second adsorber 302 may employ a sleeve structure for supplying a heat carrier, and in order to improve the regeneration strength of the adsorbents in the first adsorber 301 and the second adsorber 302, thermal vacuum regeneration may be employed, such as using separate high vacuum shields or multi-layered vacuum shielding insulation shields. In order to ensure that the adsorbents in the first adsorber 301 and the second adsorber 302 are not affected by the mechanical damage substances of the adsorbents during the actual use, a filter (not shown) is usually disposed on the first connecting pipe 202 at the air inlet end of the low-temperature dual-unit switching adsorber, and the filter can be a mechanical filter, wherein the filter precision of a metal filter element in the mechanical filter does not exceed 40 micrometers, and a filter element with the filter precision not exceeding 10 micrometers can be generally used. The mechanical filter may be self-cleaning by regeneration in a warm/pre-cool manner.

Referring to fig. 1, 5, 6, 7 and 8, a first branch pipe 401 and a second branch pipe 402 are arranged at an evaporation gas outlet of the liquid hydrogen storage tank, the first branch pipe 401 is connected with a throttle expansion valve, and the low-temperature gaseous hydrogen gasified in the liquid hydrogen storage tank enters the previous process in two paths: the first path of low-temperature gaseous hydrogen enters the throttle expansion valve through the first branch pipeline 401 and is merged with the mixed liquid hydrogen entering the throttle expansion valve.

The second branch pipe 402 is connected to a second low-pressure compressor, which is connected to the second high-pressure compressor, a circulating hydrogen passage a13 in the heat exchanger a1, a first circulating hydrogen passage 24 in the first reactor 2, a third low-pressure compressor, a third high-pressure compressor, and an air inlet of a circulating hydrogen passage B32 in the heat exchanger B3 in this order through a circulating pipe 403. A third branch pipe 404 and a fourth branch pipe 405 are provided at the gas outlet of the circulating hydrogen passage B32:

the third branch conduit 404 is connected to a circulating hydrogen passage C42 in the heat exchanger C4, a circulating hydrogen passage C42 in the heat exchanger C4 is connected to an air inlet of a first circulating hydrogen return passage G in the second reactor 8 through a first circulating conduit 406 in turn with a circulating hydrogen passage D52 in the heat exchanger D5, a circulating hydrogen passage E62 in the heat exchanger E6, and a circulating hydrogen passage F72 in the heat exchanger F7, an air outlet of the first circulating hydrogen return passage G is connected to an air inlet of a first circulating hydrogen return passage G in the second reactor 8 through a first circulating hydrogen return conduit 407 in turn with the first circulating hydrogen return passage F in the heat exchanger F7, the first circulating hydrogen return passage E63 in the heat exchanger E6, the first circulating hydrogen return passage D53 in the heat exchanger D5, the first circulating hydrogen return passage C43 in the heat exchanger C4, the first circulating hydrogen return passage B33 in the heat exchanger B3, the first circulating hydrogen return passage a14 in the heat exchanger a1 and then is connected to the second branch conduit 402, and then connected to a second compressor string.

The fourth branch pipeline 405 is connected to a second turbo-expander set, the second turbo-expander set is connected to the hydrogen expansion channel 54 in the heat exchanger D5, the third turbo-expander set is connected to the air inlet of the second recycle hydrogen return channel E in the heat exchanger E6, the air outlet of the second recycle hydrogen return channel E is connected to the second recycle hydrogen return channel D in the heat exchanger D5, the second recycle hydrogen return channel C in the heat exchanger C4, the second recycle hydrogen return channel B in the heat exchanger B3, and the second recycle hydrogen return channel a in the heat exchanger a1 through the second recycle hydrogen return pipeline 409, then the fourth branch pipeline 405 is connected to the second turbo-expander set, and the second turbo-expander set is connected to the second compressor set.

As shown in fig. 5, the low-temperature gaseous hydrogen gasified in the liquid hydrogen storage tank enters the previous process in two paths: the second path of low-temperature gaseous hydrogen enters a circulating hydrogen channel B32 in a heat exchanger B3 through a second low-pressure compressor, a second high-pressure compressor, a circulating hydrogen channel A13 in a heat exchanger A1, a first circulating hydrogen channel 24 in a first reactor 2, a third low-pressure compressor and a third high-pressure compressor, and the low-temperature gaseous hydrogen output from an air outlet of the circulating hydrogen channel B32 is circulated in two paths of circulating hydrogen:

one path of circulating hydrogen enters a first circulating hydrogen return channel G in the second reactor 8 through a circulating hydrogen channel C42 in a heat exchanger C4, a circulating hydrogen channel D52 in a heat exchanger D5, a circulating hydrogen channel E62 in a heat exchanger E6 and a circulating hydrogen channel F72 in a heat exchanger F7, then, the gas outlet of the first circulating hydrogen return channel G sequentially passes through a first circulating hydrogen return channel F of a heat exchanger F7, a first circulating hydrogen return channel E63 of a heat exchanger E6, a first circulating hydrogen return channel D53 of a heat exchanger D5, a first circulating hydrogen return channel C43 of a heat exchanger C4, a first circulating hydrogen return channel B33 of a heat exchanger B3 and a first circulating hydrogen return channel a14 of a heat exchanger a1, then is merged with the second path of low-temperature gaseous hydrogen in the second branch pipeline 402, and then enters the second low-pressure compressor again to form a first path of hydrogen refrigeration cycle.

And the other path of circulating hydrogen enters a second circulating hydrogen return channel E in a heat exchanger E6 through a second turbo-expander set, a hydrogen expansion channel in a heat exchanger D5 and a third turbo-expander set, then sequentially passes through a second circulating hydrogen return channel D in a heat exchanger D5, a second circulating hydrogen return channel C in a heat exchanger C4, a second circulating hydrogen return channel B in a heat exchanger B3 and a second circulating hydrogen return channel A in a heat exchanger A1 from an air outlet of the second circulating hydrogen return channel E, is merged with the second path of low-temperature gaseous hydrogen in the second branch pipeline 402, and then enters the second low-pressure compressor again to form a second path of hydrogen refrigeration circulating loop.

And defining the gas circulating in the first hydrogen refrigeration circulation loop and the gas circulating in the second hydrogen refrigeration circulation loop as circulating hydrogen, and converging the circulating hydrogen in the first hydrogen refrigeration circulation loop, the circulating hydrogen in the second hydrogen refrigeration circulation loop and the second low-temperature liquid hydrogen to form low-temperature circulating hydrogen.

Referring to fig. 1 and 2, a third adsorber 303 capable of removing impurities is disposed on a circulation pipeline 403 between an outlet of the first circulation hydrogen channel 24 in the first reactor 2 and the third low-pressure compressor, since the amount of impurities in the low-temperature circulation hydrogen is limited, the use requirement can be met by using one third adsorber 303, when the third adsorber 303 is regenerated, the circulation pipeline 403 between the outlet of the first circulation hydrogen channel 24 in the first reactor 2 and the third low-pressure compressor is disconnected, and after the regeneration of the third adsorber 303 is finished, the circulation pipeline 403 between the outlet of the first circulation hydrogen channel 24 in the first reactor 2 and the third low-pressure compressor is unobstructed. Of course, in the actual use process, a low-temperature double-unit conversion adsorber may be used instead of the single third adsorber 303, and the low-temperature double-unit conversion adsorber is composed of a third adsorber 303 capable of removing impurities and a fourth adsorber capable of removing impurities, and the adsorbents in the third adsorber 303 and the fourth adsorber are fine-pore zeolites capable of being thermally regenerated; when the low-temperature double-unit conversion adsorber works normally, if the third adsorber 303 works normally, the fourth adsorber is thermally regenerated; conversely, if the fourth adsorber is operating normally, the third adsorber 303 is thermally regenerated. The third adsorber 303 and the fourth adsorber may be of a sleeve structure for supplying a heat carrier, and in order to increase the regeneration strength of the adsorbents in the third adsorber 303 and the fourth adsorber, thermal vacuum regeneration may be used, such as using separate high vacuum shields or multiple vacuum-shielded insulating shields. In practical use, in order to ensure that the adsorbents in the third adsorber 303 and the fourth adsorber are not affected by the mechanical damage substances of the adsorbents, a filter (not shown in the figure) is usually disposed on the circulation pipe 403 at the air inlet end of the low-temperature dual-unit switching adsorber, the filter may be a mechanical filter, and a metal filter element in the mechanical filter has a filtering precision not exceeding 40 micrometers, and a filter element with a filtering precision not exceeding 10 micrometers may be generally used. The mechanical filter can be regenerated in a heating/precooling mode to carry out self-purification.

In actual use, in order to monitor the working conditions among the components of the hydrogen liquefaction device, a temperature sensor, a pressure sensor and a flow sensor are respectively arranged in the heat exchanger a1, the first reactor 2, the heat exchanger B3, the heat exchanger C4, the heat exchanger D5, the heat exchanger E6, the heat exchanger F7 and the second reactor 8; a hydrogen safety sensor and a smoke sensor are arranged in the hydrogen liquefaction process environment, and the hydrogen safety sensor and the smoke sensor are respectively connected with a control device for controlling the hydrogen liquefaction device. The hydrogen liquefaction process flow can be controlled by arranging control components such as stop valves at each important part of the hydrogen liquefaction device, such as: the first stop valve is arranged on the hydrogen conveying pipeline 201 positioned at the air inlet end of the first compressor unit, the second stop valve is arranged on the second branch pipeline 402 positioned at the air inlet end of the second compressor unit, control components such as the first stop valve, the second stop valve, the third stop valve and the fourth stop valve are controlled by the control device, once at least one component in each temperature sensor, the pressure sensor, the flow sensor, the hydrogen safety sensor and the smoke sensor monitors abnormity, the control device can regulate and control the components, the hydrogen liquefying device is ensured to be in fault, when the problems such as hydrogen leakage and fire disasters exist, the problems can be timely found and processed, and the loss is reduced. The hydrogen liquefying device has the advantages of flexible adjustment, safety, reliability, convenient maintenance, lower energy consumption and the like.

The hydrogen liquefaction process comprises the following specific steps:

the first step is as follows: compressing and purifying the raw material hydrogen: firstly, raw material hydrogen is compressed into gaseous hydrogen with the pressure of 2.5MPa +/-10% by a first compressor unit; and then adsorbing the oil in the gaseous hydrogen by an oil purification adsorber to ensure that the volume content of the oil in the gaseous hydrogen is not more than 10ppbV, wherein an adsorbent of the oil purification adsorber is activated carbon. Then, carrying out catalytic refining on the gaseous hydrogen to remove oxygen impurities in the gaseous hydrogen, so that the volume content of the oxygen impurities in the gaseous hydrogen is not more than 2 ppbV; catalytic refiningThe adopted catalyst is a metal catalyst, and the metal catalyst is one of platinum, nickel and palladium. Then, drying the gaseous hydrogen to ensure that the volume content of water in the gaseous hydrogen is not more than 1ppmV, and controlling the temperature of the gaseous hydrogen obtained after drying to be between-100 ℃ and-70 ℃ at a condensation point; here, the gaseous hydrogen may be dried by using a fine pore zeolite which can be regenerated by heating. Finally, CO in the gaseous hydrogen is treated by an adsorber capable of removing high-boiling-point impurities₂、H₂S and high boiling point impurities are adsorbed to ensure that CO in the gaseous hydrogen₂、H₂The total volume content of S and high boiling impurities does not exceed 1 ppmV.

The second step is that: carrying out normal-secondary conversion on the compressed and purified gaseous hydrogen: precooling the compressed and purified gaseous hydrogen to 102.7 +/-10K by a heat exchanger A, then entering a first hydrogen channel of a first reactor, then outputting the gaseous hydrogen from an air outlet of the first hydrogen channel, and returning the gaseous hydrogen to enter a first positive-secondary conversion channel of the first reactor for positive-secondary conversion of the gaseous hydrogen to obtain mixed liquid hydrogen with the temperature of 81.2 +/-5K and the concentration of secondary hydrogen of 46.3-55 percent; wherein the cold energy in the heat exchanger A is provided by liquid nitrogen and low-temperature circulating hydrogen.

The liquid nitrogen is prepared by a liquid nitrogen precooling process, which comprises the following specific steps:

(1) the raw material nitrogen is preliminarily pressurized to gaseous nitrogen with the pressure of 0.9Mpa and the temperature of 300K-313K through a compressor 601; the compressor 601 described herein may be an oil-free centrifugal turbo compressor;

(2) conveying the primarily pressurized gaseous nitrogen to a K loop in a KT turbine expansion compressor 602 for secondary pressurization, expansion throttling and cooling to obtain gaseous nitrogen with the pressure of 0.128-0.13 MPa and the temperature of 120K +/-5K;

(3) feeding the gaseous nitrogen subjected to secondary pressurization, expansion, throttling and temperature reduction into a first heat exchanger 603 for primary cooling liquefaction treatment to obtain a gas-liquid mixture of the gaseous nitrogen and liquid nitrogen at the temperature of 79.2K +/-2K; delivering unliquefied gaseous nitrogen in the gas-liquid mixture into a T loop in a KT turbine expansion compressor 602 for expansion throttling and temperature reduction, then converging the unliquefied gaseous nitrogen with the gaseous nitrogen separated from a gas-liquid separator 605 to be used as cooling media of a first heat exchanger 603 and a second heat exchanger 604, then sequentially delivering the cooling media into the second heat exchanger 604 and the first heat exchanger 603, and providing cold energy for the second heat exchanger 604 and the first heat exchanger 603 and then returning the cooling media back to the compressor 601 for preliminary pressurization; conveying liquefied liquid nitrogen in the gas-liquid mixture to a second heat exchanger 604 for second cooling liquefaction treatment, and conveying to a gas-liquid separator 605 for gas-liquid separation to obtain liquid nitrogen with the pressure of 0.123-0.128 MPa and the temperature of 70-79.2K;

(4) conveying liquid nitrogen obtained after gas-liquid separation into a first cold box in a hydrogen gasification device, wherein the liquid nitrogen is used as a cold removal medium of the first cold box, and returns to a compressor again for preliminary pressurization after cold energy is provided for the first cold box; wherein said first cold box comprises: the heat exchanger A and the first reactor are used for sequentially conveying liquid nitrogen obtained after gas-liquid separation to the first reactor and the heat exchanger A so as to provide cold energy for the first reactor and the heat exchanger A; wherein the temperature of the liquid nitrogen entering the first cold box is 70K-79.2K;

(5) and circulating the steps.

And continuously sampling and analyzing the compressed and purified gaseous hydrogen to ensure that the purified and liquefied gaseous hydrogen meets the requirements of impurity components contained in the hydrogen in the first table. Of course, this is also a means of detecting whether the decontamination is satisfactory.

TABLE I gaseous Hydrogen composition requirements after purification before liquefaction

according to the standard in the industry, the volume content of nitrogen in liquid hydrogen does not exceed 200ppbV, but for continuous operation of subsequent liquefaction, as long as the volume content of concentrated nitrogen in compressed and purified gaseous hydrogen does not exceed 600ppbV, according to the reference accessory of GOST R56248-2014, the amount of nitrogen can be dissolved in liquid hydrogen with the temperature exceeding 20.64K or the equilibrium pressure exceeding 0.115 MPa (absolute), which is the minimum limit for storing liquid hydrogen.

The selection of the oxygen content requirement is detailed in table one, where the values quoted are critical values according to the standards in the industry and meet a product temperature of 22.15K or an equilibrium pressure of 0.17 mpa; if the oxygen concentration is not allowed to exceed the range, the oxygen concentration is reduced and monitored until the volume content reaches 0.5ppbV, so that the hydrogen liquefying device can be operated under the condition of no accumulated solid oxygen, and each gas, liquid channel and pipeline in the hydrogen liquefying device are not easy to block, if the blockage occurs, explosion is easy to cause, so that the arrangement effectively reduces the potential safety hazard of the hydrogen liquefying device.

The third step: performing liquid hydrogen positive-secondary conversion on the mixed liquid hydrogen: the mixed liquid hydrogen output from the gas outlet of the first positive secondary conversion channel 22 of the first reactor 2 returns to the first liquid hydrogen channel 23 of the first reactor 2, then is output from the gas outlet of the first liquid hydrogen channel 23, and then sequentially passes through a heat exchanger B3, a heat exchanger C4, a heat exchanger D5, a heat exchanger E6, a heat exchanger F7 and a throttle expansion valve to be cooled to 23.6 +/-10K in a stepped manner, enters the second liquid hydrogen channel 81 of the second reactor 8, then is output from the gas outlet of the second liquid hydrogen channel 81, and then returns to enter the second positive secondary conversion channel 82 of the second reactor 8 to be subjected to liquid hydrogen positive secondary conversion, so that liquid hydrogen with the temperature of 2.13K-5K and the secondary hydrogen concentration of not less than 98% is obtained.

The fourth step: liquid hydrogen storage: the liquid hydrogen output from the gas outlet of the second positive-secondary conversion channel 82 of the second reactor 8 returns to the third liquid hydrogen channel 83 of the second reactor 8, and then the liquid hydrogen output from the gas outlet of the third liquid hydrogen channel 83 is stored in a liquid hydrogen storage tank; the low-temperature gaseous hydrogen gasified in the liquid hydrogen storage tank enters the previous process in two paths: the first path of low-temperature gaseous hydrogen is converged with the mixed liquid hydrogen entering the throttle expansion valve through the throttle expansion valve; the second path of low-temperature gaseous hydrogen is compressed into low-temperature gaseous hydrogen with the pressure of 2.5MPa +/-10% by a second compressor unit, then sequentially enters a heat exchanger A1, a first reactor 2, a third compressor unit and a heat exchanger B3, and then is divided into two paths of circulating hydrogen to enter the previous process: and one path of circulating hydrogen sequentially passes through a heat exchanger C4, a heat exchanger D5, a heat exchanger E6, a heat exchanger F7 and a second reactor 8 and then returns to the heat exchanger F7, and then sequentially passes through a heat exchanger E6, a heat exchanger D5, a heat exchanger C4, a heat exchanger B3 and a heat exchanger A1 and then is merged with the second path of low-temperature gaseous hydrogen to enter a second compressor unit to form a first path of hydrogen refrigeration circulating loop. And the other path of circulating hydrogen enters a heat exchanger D5 after being compressed and expanded by a second turbo expander set, then enters a heat exchanger E6 after being compressed and expanded by a third turbo expander set, then returns to the heat exchanger D5, the heat exchanger C4, the heat exchanger B3 and the heat exchanger A1 in sequence, is merged with the second path of low-temperature gaseous hydrogen, and then enters the second compressor set to form a second path of hydrogen refrigeration circulating loop. The circulating hydrogen in the first hydrogen refrigeration circulating loop, the circulating hydrogen in the second hydrogen refrigeration circulating loop and the second low-temperature liquid hydrogen are converged to form low-temperature circulating hydrogen, and the low-temperature circulating hydrogen provides cold for a heat exchanger A1, a first reactor 2, a heat exchanger B3, a heat exchanger C4, a heat exchanger D5, a heat exchanger E6, a heat exchanger F7 and a second reactor 8; the expansion pressure at the outlet of the second turboexpander set is 1.58mpa, and the expansion pressure at the outlet of the third turboexpander set is 0.25 mpa.

The first compressor unit in the first step is composed of a first low-pressure compressor and a first high-pressure compressor, raw material hydrogen is compressed into gaseous hydrogen with the pressure of 0.29MPa +/-10% through the first low-pressure compressor, and then the gaseous hydrogen with the pressure of 2.5MPa +/-10% is compressed through the first high-pressure compressor; the first low-pressure compressor can adopt a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the first high-pressure compressor can adopt a high-pressure unit-dry piston multi-stage compressor.

The second compressor set in the fourth step is composed of a second low-pressure compressor and a second high-pressure compressor, the low-temperature circulating hydrogen is compressed into low-temperature circulating hydrogen with the pressure of 0.29MPa +/-10% by the second low-pressure compressor, and then compressed into low-temperature circulating hydrogen with the pressure of 2.5MPa +/-10% by the second high-pressure compressor; the second low-pressure compressor can adopt a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the second high-pressure compressor can adopt a high-pressure unit-dry piston multi-stage compressor.

And the third compressor unit in the fourth step is composed of a third low-pressure compressor and a third high-pressure compressor, and the low-temperature circulating hydrogen output from the first reactor 2 is compressed into low-temperature circulating hydrogen with the pressure of 0.29MPa +/-10% by the third low-pressure compressor and then compressed into low-temperature circulating hydrogen with the pressure of 2.5MPa +/-10% by the third high-pressure compressor. The third low-pressure compressor can adopt a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the third high-pressure compressor can adopt a high-pressure unit-dry piston multi-stage compressor.

In order to improve the purity of the final liquid hydrogen purification, one more adsorption is usually performed in the second step, as follows: precooling the compressed and purified gaseous hydrogen to 102.7 +/-10K by a heat exchanger A1, then entering a first hydrogen channel 21 of a first reactor 2, then outputting the gaseous hydrogen from a gas outlet of the first hydrogen channel 21, adsorbing the gaseous hydrogen by a low-temperature double-unit conversion adsorber, returning the gaseous hydrogen after adsorption to enter a first positive-secondary conversion channel 22 of the first reactor 2 for positive-secondary conversion of the gaseous hydrogen to obtain mixed liquid hydrogen with the temperature of 81.2 +/-5K and the secondary hydrogen concentration of 46.3-55%; the low-temperature double-unit conversion adsorber consists of a first adsorber 301 and a second adsorber 302; when the compressed and purified gaseous hydrogen is subjected to adsorption treatment by the first adsorber 301, the second adsorber 302 is thermally regenerated; when the compressed and purified gaseous hydrogen is subjected to adsorption treatment by the second adsorber 302, the first adsorber 301 regenerates thermally; and (4) compressing the second path of low-temperature gaseous hydrogen in the step (4) into low-temperature gaseous hydrogen with the pressure of 2.5MPa +/-10% through a second compressor unit, and then sequentially entering a heat exchanger A1, the first reactor 2 and a third adsorber 303 and then entering a third compressor unit.

And respectively carrying out water cooling or air cooling heat dissipation on the oil-free centrifugal compressor, the first compressor unit, the second compressor unit and the third compressor unit. A temperature sensor, a pressure sensor and a flow sensor are respectively arranged in the heat exchanger a1, the first reactor 2, the heat exchanger B3, the heat exchanger C4, the heat exchanger D5, the heat exchanger E6, the heat exchanger F7 and the second reactor 8; a hydrogen safety sensor and a smoke sensor are arranged in the hydrogen liquefaction process environment, and the hydrogen safety sensor and the smoke sensor are respectively connected with a control device for controlling the hydrogen liquefaction process flow.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, but any modifications or equivalent variations made in accordance with the technical spirit of the present invention are within the scope of the present invention as claimed.

③ the ③ hydrogen ③ liquefying ③ process ③ has ③ the ③ advantages ③ that ③ the ③ high ③ - ③ purity ③ liquid ③ hydrogen ③ can ③ be ③ obtained ③ by ③ the ③ hydrogen ③ liquefying ③ process ③, ③ the ③ concentration ③ of ③ parahydrogen ③ in ③ the ③ liquid ③ hydrogen ③ is ③ not ③ lower ③ than ③ 98 ③% ③, ③ the ③ concentration ③ of ③ the ③ parahydrogen ③ which ③ can ③ spontaneously ③ generate ③ the ③ normal ③ - ③ secondary ③ conversion ③ in ③ the ③ liquid ③ hydrogen ③ is ③ effectively ③ reduced ③, ③ the ③ evaporation ③ loss ③ of ③ the ③ liquid ③ hydrogen ③ is ③ small ③, ③ the ③ blockage ③ phenomenon ③ of ③ each ③ gas ③ channel ③, ③ liquid ③ channel ③ and ③ pipeline ③ in ③ the ③ hydrogen ③ liquefying ③ device ③ which ③ is ③ depended ③ by ③ the ③ hydrogen ③ liquefying ③ process ③ is ③ not ③ easy ③ to ③ occur ③, ③ the ③ potential ③ safety ③ hazard ③ is ③ reduced ③, ③ the ③ low ③ - ③ temperature ③ gaseous ③ hydrogen ③ gasified ③ in ③ the ③ liquid ③ hydrogen ③ storage ③ tank ③ can ③ be ③ recycled ③, ③ the ③ potential ③ safety ③ hazard ③ and ③ the ③ energy ③ waste ③ caused ③ by ③ directly ③ releasing ③ the ③ low ③ - ③ temperature ③ gaseous ③ hydrogen ③ can ③ be ③ avoided ③, ③ the ③ cold ③ energy ③ can ③ be ③ provided ③ for ③ hydrogen ③ liquefying ③, ③ the ③ energy ③ consumption ③ required ③ for ③ hydrogen ③ liquefying ③ is ③ reduced ③, ③ the ③ cost ③ is ③ reduced ③, ③ the ③ cold ③ energy ③ is ③ provided ③ for ③ the ③ first ③ reactor ③ 2 ③ through ③ the ③ nitrogen ③ refrigerating ③ circulation ③ loop ③, ③ the ③ first ③ hydrogen ③ refrigerating ③ circulation ③ loop ③ and ③ the ③ second ③ hydrogen ③ refrigerating ③ circulation ③ loop ③, ③ the ③ liquid ③ nitrogen ③ consumption ③ is ③ reduced ③ by ③ about ③ 30 ③% ③ compared ③ with ③ the ③ traditional ③ nitrogen ③ refrigerating ③ circulation ③ loop ③, ③ the ③ energy ③ consumption ③ required ③ for ③ hydrogen ③ liquefying ③ is ③ further ③ reduced ③. ③

Claims

1. A hydrogen liquefaction process, characterized by: the process comprises the following steps:

(1) compressing and purifying the raw material hydrogen: firstly, raw material hydrogen is compressed into gaseous hydrogen with the pressure of 2.5 +/-0.25 MPa by a first compressor unit; then adsorbing the oil in the gaseous hydrogen by an oil purification adsorber to ensure that the volume content of the oil in the gaseous hydrogen is not more than 10 ppbV; carrying out catalytic refining on the gaseous hydrogen to remove oxygen impurities in the gaseous hydrogen, so that the volume content of the oxygen impurities in the gaseous hydrogen is not more than 2 ppbV; drying gaseous hydrogen to ensure that the volume content of water in the gaseous hydrogen is not more than 1ppmV, and obtaining the temperature of the gaseous hydrogen after dryingControlling the condensation point temperature between-100 ℃ and-70 ℃; then CO in the gaseous hydrogen is treated by an adsorber capable of removing high boiling point impurities₂、H₂S and high boiling point impurities are adsorbed to ensure that CO in the gaseous hydrogen₂、H₂The total volume content of S and high boiling point impurities is not more than 1 ppmV;

2. A hydrogen liquefaction process according to claim 1, characterised in that: the first compressor unit in the step (1) is composed of a first low-pressure compressor and a first high-pressure compressor, raw material hydrogen is compressed into gaseous hydrogen with the pressure of 0.29 +/-0.029 MPa through the first low-pressure compressor, and then compressed into gaseous hydrogen with the pressure of 2.5 +/-0.25 MPa through the first high-pressure compressor; the second compressor set in the step (4) is composed of a second low-pressure compressor and a second high-pressure compressor, low-temperature circulating hydrogen is compressed into low-temperature circulating hydrogen with the pressure of 0.29 +/-0.029 MPa by the second low-pressure compressor, and then compressed into low-temperature circulating hydrogen with the pressure of 2.5 +/-0.25 MPa by the second high-pressure compressor; the third compressor set is composed of a third low-pressure compressor and a third high-pressure compressor, low-temperature circulating hydrogen output from the first reactor is compressed into low-temperature circulating hydrogen with the pressure of 0.29 +/-0.029 MPa by the third low-pressure compressor, and then is compressed into low-temperature circulating hydrogen with the pressure of 2.5 +/-0.25 MPa by the third high-pressure compressor.

3. A hydrogen liquefaction process according to claim 2, characterised in that: the first low-pressure compressor in the step (1) is a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the first high-pressure compressor is a high-pressure unit-dry piston multi-stage compressor; the second low-pressure compressor in the step (4) is a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the second high-pressure compressor is a high-pressure unit-dry piston multi-stage compressor; the third low-pressure compressor is a low-pressure unit-spiral oil-filled compressor or a low-pressure dry piston multi-stage compressor, and the third high-pressure compressor is a high-pressure unit-dry piston multi-stage compressor.

4. A hydrogen liquefaction process according to claim 1, characterised in that: the adsorbent of the oil purification adsorber in the step (1) is activated carbon; the catalyst used for catalytic refining is a metal catalyst, and the metal catalyst is one of platinum, nickel and palladium.

5. A hydrogen liquefaction process according to claim 1, 2 or 4, characterised in that: the adsorbent of the adsorber capable of removing the high-boiling-point impurities in the step (1) is thermally-regenerated fine-pore zeolite, and the gaseous hydrogen is dried by the thermally-regenerated fine-pore zeolite.

6. A hydrogen liquefaction process according to claim 1, 2 or 4, characterised in that: and (2) continuously sampling and analyzing the compressed and purified gaseous hydrogen in the step (1).

7. A hydrogen liquefaction process according to claim 1, 2 or 4, characterised in that: precooling the gaseous hydrogen compressed and purified in the step (2) to 102.7 +/-10K by a heat exchanger A, then entering a first hydrogen channel of a first reactor, then outputting the gaseous hydrogen from an air outlet of the first hydrogen channel, adsorbing the gaseous hydrogen by a low-temperature double-unit conversion adsorber, returning the adsorbed gaseous hydrogen to a first positive-secondary conversion channel of the first reactor for positive-secondary conversion of the gaseous hydrogen to obtain mixed liquid hydrogen with the temperature of 81.2 +/-5K and the secondary hydrogen concentration of 46.3-55%; the low-temperature double-unit conversion adsorber consists of a first adsorber and a second adsorber, and the adsorbents in the first adsorber and the second adsorber can be thermally regenerated; when the compressed and purified gaseous hydrogen is subjected to adsorption treatment by the first adsorber, the second adsorber is thermally regenerated; when the compressed and purified gaseous hydrogen is subjected to adsorption treatment by the second adsorber, the first adsorber is thermally regenerated; and (4) compressing the low-temperature circulating hydrogen in the step (4) into low-temperature circulating hydrogen with the pressure of 2.5 +/-0.25 MPa through a second compressor unit, and then sequentially entering a heat exchanger A, a first reactor and a third adsorber and then entering a third compressor unit.

8. A hydrogen liquefaction process according to claim 1, characterised in that: the liquid nitrogen in the step (2) is prepared by a liquid nitrogen precooling process, which comprises the following specific steps:

(5) and circulating the steps.

9. A hydrogen liquefaction process according to claim 8, characterised in that: and respectively carrying out water cooling or air cooling heat dissipation on the oil-free centrifugal compressor, the first compressor unit, the second compressor unit and the third compressor unit.

10. A hydrogen liquefaction process according to claim 1, 2, 4 or 8 wherein: a temperature sensor, a pressure sensor and a flow sensor are respectively arranged in the heat exchanger A, the first reactor, the heat exchanger B, the heat exchanger C, the heat exchanger D, the heat exchanger E, the heat exchanger F and the second reactor; a hydrogen safety sensor and a smoke sensor are arranged in the hydrogen liquefaction process environment, and the hydrogen safety sensor and the smoke sensor are respectively connected with a control device for controlling the hydrogen liquefaction process flow.