FR3119883A1 - Hydrogen liquefaction method and apparatus - Google Patents

Abstract

Title: Hydrogen Liquefaction Process and Apparatus In a process for the liquefaction of hydrogen, a hydrogen-rich gas (27) is sent from a separation device (102) by distillation and/or stripping and/or partial condensation, the gas leaving the separation device at a temperature of at most 103K containing at least 99.9% mol of hydrogen and at a pressure between 20 and 30 bars in a hydrogen liquefier, without having heated the hydrogen-rich gas to a temperature above 0°C. Abstract Figure: FIG.2

Description

Hydrogen liquefaction method and apparatus

The present invention relates to a process and an apparatus for the liquefaction of hydrogen, preferably integrated with the cryogenic separation of a mixture of carbon monoxide and hydrogen.

Hydrogen liquefaction is described in “Engineering Techniques”, chapter by Jean Gallarda, J3603.

The hydrogen is cooled and then liquefied in three stages:

• From ambient temperature up to 230K by a refrigeration unit
• From 230K to about 80K by a first refrigeration cycle
• From about 80K to about 20K by a second refrigeration cycle

The heat exchange between 300K and 20K is done through brazed aluminum multi-passage plate heat exchangers.

The passages corresponding to the flow of gas to be liquefied contain catalyst and allow continuous conversion of hydrogen until a para-hydrogen content greater than 95% is reached.

The cooling down to approximately 80K is carried out in an enclosure thermally insulated with perlite. This cooling, called pre-cooling, is carried out using a closed nitrogen cycle or with the cold of an addition of cryogenic liquid (generally liquid nitrogen) called in French "biberonnage", both consuming lot of energy.

Cooling from approximately 80K to 20K takes place in a vacuum enclosure maintained at approximately 10 ^-6 mm Hg, with the equipment in the enclosure surrounded by multi-layer insulation. This cooling, which includes liquefaction, is carried out using a hydrogen or helium cycle. A nitrogen cycle, in particular, could not be used at such low temperatures.

An object of the present invention is to reduce the energy consumption of the process and possibly to eliminate part of the equipment by eliminating the precooling step.

According to one object of the invention, there is provided a hydrogen liquefaction process in which:

1. A hydrogen-rich gas is sent from a separation apparatus by distillation and/or exhaustion and/or partial condensation, the gas leaving the separation apparatus at a temperature of at most 103K containing at least 99.9% mol of hydrogen, preferably at least 99.99%, mol of hydrogen or even at least 99.999% mol of hydrogen and at a pressure between 20 and 30 bars to a hydrogen liquefier, without having heated the hydrogen-rich gas to a temperature above 0°C, preferably above -50°C, or even above -100°C.
2. The hydrogen-rich gas is cooled from the temperature of at most 103K and at the pressure between 20 and 30 bars in a first heat exchanger of the liquefier and liquefied to form liquid hydrogen.

According to one object of the invention, there is provided a process for the liquefaction of hydrogen integrated with the cryogenic separation of a mixture of hydrogen and of another component in which the mixture is cooled in an auxiliary heat exchanger until at least 120K, the cooled mixture is separated by partial condensation and/or by distillation and/or by exhaustion at a temperature below 120K to produce a flow rich in hydrogen containing at least one impurity at between 20 and 30 bars and purifies the hydrogen-rich stream at a cryogenic temperature of at most 103K to reduce its content of the at least one impurity to form the hydrogen-rich gas of step i).

According to other optional aspects of the invention which may be combined in any manner compatible with science and logic:

• the hydrogen-rich gas is purified by adsorption to remove the at least one impurity which is carbon monoxide and/or nitrogen and/or methane.
• the mixture comprises as main components hydrogen and carbon monoxide and possibly methane and/or nitrogen.
• the hydrogen-rich gas is withdrawn from a distillation or stripping column or from a phase separator, said column or separator operating at between 20 and 30 bars abs.
• the process is kept cold at least partially by a refrigeration cycle, the cycle fluid being heated and cooled in the first heat exchanger and optionally in a second heat exchanger.
• the liquefied hydrogen is stored in a storage whose boil-off gas is heated in the first and second heat exchangers.
• the hydrogen-rich gas liquefies in the first heat exchanger or downstream thereof inside a first insulated enclosure and the mixture is separated and optionally the hydrogen-rich flow is purified inside a second insulated enclosure.
• the hydrogen-rich gas is mixed with a hydrogen-rich stream having substantially the same pressure, temperature and composition and the mixture is liquefied in the first heat exchanger or after cooling in the first heat exchanger.
• the hydrogen-rich stream cools in the second heat exchanger and then is mixed with the hydrogen-rich gas.
• the hydrogen-rich gas is not mixed with another gas upstream of the first heat exchanger.

According to another object of the invention, there is provided a hydrogen liquefaction apparatus comprising a liquefier comprising a first heat exchanger, a separation apparatus by distillation and/or exhaustion and/or partial condensation, means for sending a hydrogen-rich gas originating from the apparatus for separation by distillation and/or stripping and/or partial condensation at a temperature of at most 103K containing at least 99.9% mol of hydrogen, preferably at least 99.99%, mol of hydrogen or even at least 99.999% mol of hydrogen and at a pressure between 20 and 30 bars in the hydrogen liquefier, without having heated the hydrogen-rich gas to a temperature above 0°C and means for sending the hydrogen-rich gas will be cooled from the temperature of at most 103K and at the pressure between 20 and 30 bars in the first heat exchanger and means for liquefying the cooled gas to form liquid hydrogen.

The liquefier may include a second heat exchanger to cool another flow of hydrogen which will be mixed with that coming from the separation device or may only include the first heat exchanger to cool a gas to be liquefied.

By feeding the liquefaction process with a hydrogen-rich gas available at the required pressure and temperature, it is possible to reduce the size of the precooling heat exchanger or even eliminate it altogether if all the feed gas comes from an external source already the right pressure and the right temperature.

The means for liquefying the cooled gas to form liquid hydrogen can be constituted by the first heat exchanger and/or by expansion means downstream of the latter.

The expansion means are preferably located in the same insulated enclosure as the heat exchanger but may be in a dedicated thermally insulated enclosure.

The invention will be described in more detail with reference to the figures.

illustrates a cryogenic separation process to produce hydrogen.

And very schematically illustrate hydrogen liquefaction processes originating, for example, from the process of .

shows a process using a phase separator 9, a methane washing column 15, a stripping column 25 and a carbon monoxide and methane separation column 45, containing for example structured packings for the columns and capable of operate at cryogenic temperatures.

The syngas 1 containing carbon monoxide, methane and carbon monoxide is purified into water and/or carbon dioxide in the purification unit 3 before arriving at the heat exchanger 7 where it cools to cryogenic temperature and partially condenses.

The two phases are separated in a phase separator 9, to form a gas 11 enriched in hydrogen and a liquid depleted in hydrogen 13. The gas 11 is sent to the bottom of the methane scrubbing column 15 which produces a gas 19 enriched in hydrogen which heats up in the exchanger. Part of this gas 19 is used to regenerate the purification unit 3.

At least one intermediate gas 210, 211 withdrawn from column 15 is cooled in a heat exchanger 23 by heat exchange with a process fluid, here the liquid 51.

Bottom liquid 17 from column 15 joins liquid 13 from separator 9 and mixture 91 containing between 1 and 3% mol of hydrogen is sent to the top of a stripping column 25. A top gas 27 from the stripping column contains at least 95% mol of hydrogen as well as carbon monoxide, nitrogen and methane. It is between 20 and 30 bars which is the operating pressure of column 25 and has a temperature between 103 and 120K. The gas 27 is not heated but is purified in an adsorption unit 29 operating at cryogenic temperatures to remove carbon monoxide and/or methane and/or nitrogen to provide a gas 31 capable of being liquefied. containing at least 99.9% mol of hydrogen, preferably at least 99.99% mol of hydrogen or even at least 99.999% mol of hydrogen. A purification of this type is described in "The low temperature removal of small quantities of nitrogen or methane from hydrogen gas by physical adsorption on a synthetic zeolite", Kidnay et al, AIChE Journal, Vol 12, no. 1, January 1966.

A liquid 33 taken from the bottom of the stripping column 25 is cooled in the exchanger 7 and is sent to the separation column 45. Another part of the same liquid 35 vaporizes in a bottom reboiler 37 and is returned to the bottom. of the exhaustion column.

The separation column comprises several distillation separation sections and optionally a capacity 99. It has a bottom reboiler 73 which is used to heat the bottom liquid 75, the gas formed being returned to the bottom. The bottom liquid 77 enriched in methane is divided into two. Part 83 vaporizes in exchanger 7 to form fuel. The rest 85 is pressurized by a pump 87 and is sent to the top of the washing column 15.

The overhead gas from column 43 enriched in carbon monoxide is sent to a product compressor 57 which produces a gas enriched in carbon monoxide 57. A portion of the gas enriched in carbon monoxide 61 is cooled and splits into two. Part 65 is expanded in a turbine 67 to supply cold. The expanded gas 89 is returned to the inlet of the compressor 57. The rest of the gas 69 continues its cooling in the exchanger 7 and is used to heat the reboilers 73 and 37 (flows 93 and 73). The gas used for the reboiling is thus partially condensed and supplies as flow 97 capacity 99 at the top of separation column 45. Gas 41 from capacity 99 supplies compressor 57. Liquid 47 from capacity 99 is sent to a phase separator 49, the liquid 51 from the separator serves as refrigerant in the heat exchanger 23 to cool the intermediate gases 21A, 21B, 21C as well as the top gas 27 of the stripping column.

A liquid withdrawn from the separation section of the separation column can replace liquid 47 or another process liquid.

It will be understood that there are many methods for separating a mixture of hydrogen and carbon monoxide as main components, possibly also containing nitrogen and/or methane. If these processes make it possible to produce hydrogen at a cryogenic temperature and at a pressure compatible with those of the liquefier, the hydrogen produced may be purified at cryogenic temperature and sent to the liquefier as feed gas, possibly as the only supply gas. feed.

For example, hydrogen 27 can be produced by a phase separator at between 20 and 30 bar abs in a partial condensation process associated or not with distillation.

Other separation processes are also capable of supplying hydrogen at cryogenic temperature and pressure between 20 and 30 bar, for example the separation of purge gas from an ammonia production process.

As the hydrogen leaves the enclosure of the cold process at low temperature, additional cold will have to be provided compared to a process where the hydrogen heats up to ambient temperature. This is achieved by increasing the production of frigories. For the case of a cryogenic separation of carbon monoxide and hydrogen, it is necessary to increase the flow rate of the CO (or N2) cycle.

The hydrogen produced at low temperature and at a pressure between 20 and 30 bars can be purified in the thermally insulated enclosure in which the separation column and/or the phase separator from which it comes is located. Otherwise, and in particular in the case of the modification of an existing apparatus, the hydrogen can leave the enclosure where the separation column and/or the phase separator from which it comes and be sent by at least one pipe thermally insulated in an enclosure 102 containing the purification device to reduce its content of impurities, for example at least one of carbon monoxide, methane and nitrogen.

The “cold” purification is a necessary step in order to eliminate all the impurities which could freeze along the exchange line which goes down to approximately 20K, and consequently clog the heat exchangers.

[tab. 1] Average molar purity before purification Range of possible purities before purification Purity after purification _H2 98% 95% to 99% > 99.999% CO 0.4% ppm at 1% < 10 ppb CH ₄ 1.2% 0.5% to 3% < 10 ppb # ₂ 0.4% ppm to 1% < 10 ppb

Purification of hydrogen gas with a TSA (Temperature Swing Adsorption) type temperature swing adsorption unit is normally possible at 80K (where the adsorption capacity is high. Removing 2% or even 1% of impurities involves short cycles (a few hours) and a high regeneration rate.

shows a first variant of the method according to the invention where the flow rate 27 of the feeds a liquefaction process as the only feed fluid.

The gaseous purified hydrogen 27 leaves either the thermally insulated enclosure E in which the separation column and/or the phase separator C is located, from which it comes, or from a dedicated purification enclosure 102 at a pressure between 20 and 30 bar abs.

Without being heated to a temperature above 0°C, preferably above -50°C, or even above -100°C, or even without having been heated at all and preferably without being compressed, it passes through at least one thermally insulated pipe into another thermally insulated enclosure 104 where it will be liquefied.

This enclosure 104 contains a brazed aluminum multi-passage plate heat exchanger 101 .

The passages corresponding to the flow of gas to be liquefied contain catalyst and allow continuous conversion of hydrogen until a para-hydrogen content greater than 95% is reached.

The enclosure 104 is under vacuum maintained at approximately 10 ^-6 mm Hg, the equipment inside the enclosure being surrounded by multilayer insulation. This cooling that takes place there includes liquefaction and is carried out using a hydrogen or helium cycle.

The exchanger 101 may simply contain at least one passage for cooling and liquefying the hydrogen, all the hydrogen being produced in liquid form and removed as product 111, as well as the passages necessary for the refrigeration cycle or cycles.

The purified hydrogen can be introduced at the hot end of the heat exchanger 101.

It will therefore be understood that if the purified hydrogen is the only source of hydrogen to be liquefied or if all the hydrogen to be liquefied is available at the temperature of the hydrogen to be purified, no precooling will be necessary and the second conventional exchanger to cool hydrogen up to around 120K with its nitrogen cycle or other refrigerant will not be required.

In other cases, as illustrated in , the second exchanger 103 will be present but preferably the purified hydrogen 27 coming from the low temperature separation will be mixed with the hydrogen 127 cooled in the second exchanger outside the enclosure 106 of the second exchanger 103 and then the mixture formed will be cooled in the liquefaction heat exchanger 101 inside the enclosure 104.

The detail of the cooling cycles is not given for the exchangers 101, 103 of the figures, these cycles being abundantly described in the literature for example "Principles for the liquefaction of hydrogen with emphasis on precooling processes" by Walnum et al, IIR Conference , 2012, Berstad, D.O., J.H. Stang, and P. Nekså, Large-scale hydrogen liquefier using mixed-refrigerant pre-cooling. International Journal of Hydrogen Energy, 2010. 35(10): p. 4512-4523, Quack, H. Conceptual design of a high efficiency large capacity hydrogen liquefier. in ADVANCES IN CRYOGENIC ENGINEERING: Proceedings of the Cryogenic Engineering Conference - CEC. 2002. Madison, Wisconsin (USA): AIP, EP3339605, EP3368630, EP3368631, EP3368844, EP3368845 and EP3759192.

Hydrogen liquefaction as such, usually driven by the H2 cycle, can be:

• a) either made directly with the excess hydrogen gas which will not be liquefied (approximately 5000 Nm ³ /h at 29 bars can be liquefied by 50000 Nm ³ /h of hydrogen at the same pressure). In this case, this excess hydrogen (and ultra pure → no PSA required) can be returned to the customer at low pressure or partially at medium pressure at 6 bara for example or, by adding a hydrogen compressor, at pressures of at least 20+bara)
• b1) or via an independent H2 cycle, for example where a large quantity of liquid hydrogen is desired
• b2) or via an independent He cycle

The invention can also be used by modifying an existing synthesis gas separation apparatus. Consideration should be given to increasing the size of the refrigeration cycle, the size of the turbines and the size of the cycle compressor coolers.

The use of liquid nitrogen bottle feeding can provide the cold temperatures necessary to extract one of the main products at subambient temperature.

Possibly the synthesis gas 1 can be cooled at least partially in the heat exchanger 103 upstream of the separation.

Optionally at least part of the apparatus for separation by distillation and/or exhaustion and/or partial condensation can be arranged in the same thermally insulated enclosure as the second heat exchanger.

The hydrogen to be liquefied is usually expanded at the end of cooling in a turbine and/or a valve. This last step is not illustrated.

Claims (12)

Hydrogen liquefaction process in which

1. A hydrogen-rich gas (27) is sent from a separation apparatus by distillation and/or exhaustion and/or partial condensation, the gas leaving the separation apparatus at a temperature of at most 103K containing at least 99 99.99% mol of hydrogen, preferably at least 99.99% mol of hydrogen or even at least 99.999% mol of hydrogen and at a pressure between 20 and 30 bars to a hydrogen liquefier, without having reheated the rich gas into hydrogen at a temperature above 0°C.
2. The hydrogen-rich gas is cooled from the temperature of at most 103K and at the pressure between 20 and 30 bars in a first heat exchanger (101) of the liquefier and liquefied to form liquid hydrogen.

Process for the liquefaction of hydrogen according to claim 1 integrated with the cryogenic separation of a mixture (1) of hydrogen and of another component in which the mixture is cooled in an auxiliary heat exchanger (7) until at least minus 120K, the cooled mixture is separated by partial condensation and/or by distillation and/or by exhaustion at a temperature below 120K to produce a flow rich in hydrogen containing at least one impurity at between 20 and 30 bars and the hydrogen-rich flow at a cryogenic temperature of at most 103K to reduce its content of the at least one impurity to form the hydrogen-rich gas of step i). Process according to Claim 2, in which the hydrogen-rich gas (27) is purified by adsorption (102) to remove the at least one impurity which is carbon monoxide and/or nitrogen and/or methane. Process according to Claim 2 or 3, in which the mixture (1) comprises as main components hydrogen and carbon monoxide and optionally methane and/or nitrogen. Process according to Claim 2, 3 or 4, in which the hydrogen-rich gas (27) is withdrawn from a distillation or stripping column (C) or from a phase separator, the said column or separator operating at between 20 and 30 bar abs. Process according to one of Claims 2 to 5, in which the process is kept cold at least partially by a refrigeration cycle (105), the cycle fluid being heated and cooled in the first heat exchanger (101) and optionally in a second heat exchanger (103). Method according to one of Claims 2 to 6, in which the liquefied hydrogen is stored in a storage, the evaporation gas of which is heated in the first and the second heat exchanger (101, 103). Process according to one of Claims 2 to 7, in which the hydrogen-rich gas liquefies in the first heat exchanger or downstream thereof inside a first insulated enclosure (104) and the mixture is separated and optionally the hydrogen-rich flow is purified inside a second insulated enclosure (E). Process according to one of the preceding claims, in which the hydrogen-rich gas (27) is mixed with a hydrogen-rich stream (127) having substantially the same pressure, temperature and composition and the mixture is liquefied in the first heat exchanger ( 101) or after cooling in the first heat exchanger. A method according to claims 6 and 9 wherein the hydrogen-rich stream (27) cools in the second heat exchanger (103) and then is mixed with the hydrogen-rich gas. Process according to one of Claims 1 to 8, in which the hydrogen-rich gas (27) is not mixed with another gas upstream of the first heat exchanger. Hydrogen liquefaction apparatus comprising a liquefier comprising a first heat exchanger (101), an apparatus (102) for separation by distillation and/or exhaustion and/or partial condensation, means for sending a hydrogen-rich gas (27) coming from the apparatus for separation by distillation and/or exhaustion and/or partial condensation at a temperature of at most 103K containing at least 99.9% mol of hydrogen, preferably at least 99.99%, mol of hydrogen or even at least 99.999% mol of hydrogen and at a pressure between 20 and 30 bars to the hydrogen liquefier, without having reheated the hydrogen-rich gas to a temperature above 0°C and means for sending the gas rich in hydrogen will be cooled from the temperature of at most 103K and at the pressure between 20 and 30 bar in the first heat exchanger and means for liquefying the cooled gas to form liquid hydrogen.