Method and apparatus for cooling a flow of hydrogen gas
The process recovers cold from LNG vaporization using an intermediate fluid to cool hydrogen, addressing high electrical consumption in hydrogen liquefaction by optimizing the liquefaction process and reducing compressor needs, thus enhancing energy efficiency and maintenance simplicity.
Patent Information
- Application Number
- FR2023005090
- Authority / Receiving Office
- FR · FR
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2023-05-23
- Publication Date
- 2025-04-25
- Estimated Expiration
- 2033-05-23
AI Technical Summary
Hydrogen liquefaction processes consume a significant amount of electricity, and existing methods do not effectively utilize the cold energy released during the vaporization of liquefied natural gas (LNG) to reduce this energy consumption.
A process and device that recover cold from LNG vaporization using an intermediate fluid to cool hydrogen, involving a dedicated heat exchanger and a secondary heat exchanger with a compressed cycle fluid, reducing the need for direct contact between LNG and hydrogen, and utilizing an intermediate fluid like nitrogen or argon to enhance energy efficiency.
Reduces electrical consumption in hydrogen liquefaction by leveraging the cold from LNG vaporization, minimizing compressor usage, and optimizing the hydrogen liquefaction process through an intermediate fluid cycle, enhancing energy efficiency and reducing maintenance complexity.
Smart Images
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Abstract
Description
Title of the invention: Method and apparatus for cooling a flow of gaseous hydrogen
[0001] The present invention relates to a method and apparatus for cooling a flow of hydrogen gas, in particular such a method and apparatus using cold from a flow of low temperature natural gas.
[0002] An object of the invention is to reduce the electrical consumption of hydrogen liquefaction by recovering the cold from the vaporization of LNG or a flow of natural gas at less than -100°C, or even less than -150°C.
[0003] The recovery of frigories from liquefied natural gas or LNG and its integration with a hydrogen liquefier is known from US3347055, US3398545, 'Integration design for demonstration of efficient liquefaction of hydrogen' by Berstad, IdealHy report D2.4, March 2013, EP1580506, WO05080892, JPS1140777A, JP2005241232, WO07144078 and 'Large scale hydrogen liquefaction in combination with LNG re-gasification' by Kuendig et al. 16th World Hydrogen Energy Conference 2006 (WHEC 2006), Lyon, France, 2006: 3326-3333.
[0004] The Kuendig process uses several heat exchangers to each cool two fluids, including LNG and cycle nitrogen, LNG and hydrogen at two pressures and LNG and hydrogen intended for liquefaction. Thus the nitrogen and hydrogen cycle compressors operate at a temperature below 0°C.
[0005] Hydrogen liquefaction is also known as a two-step process: pre-cooling with a nitrogen cycle or a mixed refrigerant cycle followed by the liquefaction of the hydrogen itself with typically a hydrogen or helium or mixed refrigerant cycle including noble gases.
[0006] At a liquefied natural gas (LNG) terminal, ships arrive loaded with liquid natural gas at around -150°C. In order to reinject the gas into the network, the LNG must be gasified and heated to ambient temperature. In the best case, the gas is heated with seawater in an exchanger (called an "Open Rack Vaporizer"); in the worst case, gas is burned to provide the calories needed for vaporization. The amount of LNG that can be gasified can range from a few tons to several hundred per day. This means that a very large amount of fatal cold is released during this operation.
[0007] Hydrogen liquefaction is an operation that occurs after its production in order to store and transport as much hydrogen as possible while occupying as little space as possible. The liquefaction process consists of cooling hydrogen to its dew point at -252 °C. The electrical consumption of the liquefaction of Hydrogen occupies a significant share of the energy used in the hydrogen value chain.
[0008] The two systems have complementary needs for heating and cooling, a symbiosis between the two installations can be imagined in order to reduce the energy cost of hydrogen liquefaction while satisfying the heating needs of the LNG terminal.
[0009] It is known to reduce the energy consumption of H2 liquefaction by exploiting the cold available at the LNG terminal. The hydrogen liquefier is based on a pre-cooling cycle (typically nitrogen and / or mixed refrigerants) which acts on the 80 K cold box and a liquefaction cycle (typically hydrogen or helium) which acts on the 20 K cold box.
[0010] The invention consists of a method for recovering the cold from natural gas by an intermediate fluid which is cooled opposite the LNG.
[0011] A dedicated heat exchanger (hereinafter referred to as "LNG exchanger") is used to exchange heat between the intermediate fluid and the liquefied natural gas and / or at a temperature of less than -100°C, or even less than -150°C coming from the LNG terminal. The liquefied or non-liquefied natural gas is heated against the intermediate fluid to cool the intermediate fluid to <-50°C (preferably <-120°C).
[0012] According to an object of the invention, there is provided a method for cooling a flow of gaseous hydrogen in which: i. A flow of natural gas at less than -100°C, or even less than -150°C, or a flow of liquefied natural gas heats up, or even vaporizes, in a first heat exchanger by heat exchange with an intermediate fluid which cools down ii. The hydrogen gas flow is cooled in a second plate and fin type heat exchanger by heat exchange with the intermediate fluid cooled in step i), at least a portion of the intermediate fluid arriving in the second heat exchanger at a first temperature Tl, the hydrogen gas flow entering the second heat exchanger at a first end thereof and exiting the second exchanger at a second end thereof. iii. The at least part of the intermediate fluid cools in the second exchanger a first cycle fluid compressed in at least a first compressor, at least part of the first cycle fluid leaves the second exchanger at a second temperature T2, is expanded in a turbine and is sent to the second heat exchanger at a third temperature T3 lower than T2, heats up in the second heat exchanger to a fourth temperature T4 higher than the third temperature T3 and is sent at this fourth temperature to the inlet of at least one first compressor iv. The at least a portion of the intermediate fluid heats up in the second exchanger, exits the first end thereof and is returned to the first heat exchanger to cool against the natural gas and v. At least one second cycle fluid heats up in the second heat exchanger, is compressed in at least one second compressor having a suction temperature that is a fifth temperature T5, is sent to the first end of the second heat exchanger and cools to the second end of the second heat exchanger.
[0013] According to other optional aspects of the invention, it is provided: • the flow of natural gas at less than -100°C, or even less than -150°C or the flow of liquefied natural gas heats up in the first heat exchanger to a temperature above 0°C. • at least one of the first, second, third, fourth and fifth temperatures is below -100°C, or even below -120°C. • the first temperature T1 is higher than the second temperature T2 and / or the fourth temperature T4. • the second temperature T2 is greater than -150°C. • another part of the intermediate fluid cooled in the first exchanger of heat is sent to another second heat exchanger where it is used to cool another flow of hydrogen and another first cycle fluid before being returned to the first heat exchanger. • the first heat exchanger and the second heat exchanger are located at least 500 meters from each other. • the first heat exchanger is of the shell and tube type or printed plate exchangers. • the first cycle fluid is nitrogen or a mixed refrigerant. • the second cycle fluid is hydrogen and / or helium and / or neon and / or a mixed refrigerant. • the intermediate fluid is nitrogen or argon or propane. • the intermediate fluid contains between 40 and 50% mol methane, between 0 and 10% mol propane or propylene, between 5 and 20% pentane and between 40 and 50% ethylene or ethane. • the composition of the intermediate fluid is such that it is in the dense phase after cooling in the first exchanger and circulates by means of a pump.
[0014] According to another object of the invention, there is provided an apparatus for cooling a flow of gaseous hydrogen comprising a first heat exchanger, a second plate and fin type heat exchanger, at least a first compressor, at least a second compressor, a turbine, a pipe for sending a flow of natural gas at less than -100°C, or even less than -150°C or a flow of liquefied natural gas to heat up, or even vaporize, in the first heat exchanger by heat exchange with an intermediate fluid which cools, a pipe for sending the cooled intermediate fluid to the second heat exchanger, a pipe for sending the flow of hydrogen gas to a first end of the second heat exchanger to cool in the second heat exchanger by heat exchange with the intermediate fluid cooled in step i), at least a portion of the intermediate fluid arriving in the second heat exchanger at a first temperature Tl, a pipe for leaving the flow of hydrogen from the second exchanger at a second end thereof,means for sending a first cycle fluid compressed in the at least one first compressor to the second heat exchanger, a pipe for leaving at least a portion of the first cycle fluid from the second exchanger at a second temperature T2 connected to the turbine, a pipe for sending the expanded fluid in the turbine to the second heat exchanger at a third temperature T3 lower than T2, a pipe for sending the expanded fluid heated in the second heat exchanger up to a fourth temperature T4 higher than the third temperature T3 at the inlet of the at least one first compressor, a pipe for sending at least a portion of the intermediate fluid heated in the second exchanger from the first end thereof to the first heat exchanger to cool against the natural gas,a conduit for sending at least one second cycle fluid heated into the second heat exchanger to be compressed in the at least one second compressor having a suction temperature which is a fifth temperature T5, a conduit for sending the second compressed fluid from the at least one second compressor to the first end of the second heat exchanger and a conduit for leaving the second cooled fluid from the second end of the second heat exchanger.
[0015] The invention will be described in more detail with reference to the figure.
[0016] [Fig-1] represents a method of cooling hydrogen according to the invention.
[0017] A hydrogen cooling process according to the invention is typically part of a hydrogen liquefaction process, the process according to the invention serving to reduce the temperature of the hydrogen to a temperature below 120K, typically less than 90K.
[0018] Cooling is carried out by sending the hydrogen gas 1 at between 20 and 30 bar abs into a brazed aluminum plate and fin heat exchanger E2. The hydrogen cools first in the exchanger E2 and then in exchanger E3 forming flow 3 at approximately 80K, using the cold coming from a nitrogen cycle and heating, or even vaporization of a flow of natural gas 23, which may be a flow of natural gas in gaseous form at less than -150°C or a flow of liquefied natural gas.
[0019] In the nitrogen cooling cycle a. Nitrogen 21 is compressed via a compressor C3 and a booster C4 in series to between 14 and 18 bar abs and sent to the cold box B for cooling. b. The high-pressure nitrogen stream 11 compressed in compressors C3, C4 is sent to the hot end of heat exchanger E2 and then divided into two streams 13, 15 at a temperature T2. Stream 15 is cooled in heat exchanger E2 until the nitrogen liquefies and then expanded via a valve JT VL. Stream 13 is expanded via a turbine T from temperature T2. c. The liquefied nitrogen 15 is sent to a phase separator SI where the gas 17 and a liquid 19 separate. The liquid 19 is vaporized in an exchanger E3 against the hydrogen cooled in the heat exchanger E2 and then joins the gas 17 and the nitrogen 13 expanded in the turbine T forming a flow 21 d. The nitrogen gas 21 is then heated in the cold box against the other fluids (generally hydrogen, helium, MR ...) in the exchanger E2. e. Gaseous nitrogen is extracted from the main exchanger at a cryogenic temperature (<-100°C) to be sent to the suction of the nitrogen compressor C2.
[0020] Alternatively, liquid nitrogen can also be created within turbine T in which case all the nitrogen 11 is sent to turbine T, in this case streams 15, 17, 19 are absent from the diagram, as well as exchanger E3 and separator SL
[0021] A liquefaction cycle having hydrogen, helium or mixed refrigerants as cycle fluid provides cold for the liquefaction part of a liquefier. Now the compressors of this cycle operate with a suction temperature consistent with the temperatures of the hydrogen cooling part upstream of the liquefaction part and are therefore supplied with a gas heated in the exchanger E2. The figure shows the low pressure (LP) 6 and medium pressure (MP) 8 flows coming from the 20K box which are sent to the 80K box B to be heated against the other fluids 13, 15, 17 of the box.
[0022] The BP 6 and MP 8 streams heated in the exchanger E2 are extracted from the exchanger E2, each at a temperature T5 lower than -100°C) to be sent each to the suction of one of the cycle compressors C1, C2 in series. A flow of high pressure hydrogen or helium 9 is then sent into the exchanger E2 at the hot end to be cooled there by completely passing through the E2 exchanger before being sent to the 20K box.
[0023] Unlike the prior art, the method comprises a heat exchanger E1 where the heat exchange takes place between either a flow of natural gas in gaseous form at no more than -150°C or with a liquefied natural gas 23 and an intermediate fluid 4 which may be liquid, gaseous or two-phase, single or multi-compound. This intermediate fluid must be chemically inert and may be, for example, nitrogen or argon.
[0024] The intermediate fluid 4 is cooled opposite the fluid 23 forming an intermediate fluid 5 cooled to a temperature T1 below -100°C and natural gas 24 to a temperature above 0°C.
[0025] The cooled fluid 5 is compressed via a compression member (pump or compressor, not shown).
[0026] The fluid 5 can be nitrogen or argon or propane. Otherwise the
[0027] Intermediate fluid 5 may be a three or four component mixed refrigerant containing or being composed of between 40 and 50 mol% methane, between 0 and 10 mol% propane or propylene, between 5 and 20% pentane and between 40 and 50% ethylene or ethane. The composition of the intermediate fluid is preferably such that it is in the dense phase after cooling in the first exchanger and circulates by means of a pump (not shown).
[0028] This compression can be located before or after the EL exchanger.
[0029] If the compression is located after the exchanger El, the cooled fluid can be returned to the exchanger El to be cooled again.
[0030] Once cooled, the intermediate fluid 5 is then sent to the cold box B to be reheated to room temperature against the other fluids of the hydrogen, helium or mixed refrigerant cycle 9 and the hydrogen to be cooled 1. The intermediate fluid 5 is sent to the heat exchanger E2 at a temperature higher than the inlet temperature T2 of the turbine T, for example higher than -150°C and lower than -100°C.
[0031] The main advantages of the installation are as follows: • Use of “free” cold from ~-140°C to room temperature by sending the intermediate fluid into the heat exchanger where the hydrogen cools • Absence of “hot” turbine in the nitrogen cycle • Mixed refrigerant cycle not required in case of large liquefier • Reduction in the size of the pre-cooling cycle • Reduction of compressor consumption thanks to compressions cryogenic (nitrogen and hydrogen / helium) • Vaporization and superheating of liquefied natural gas to room temperature in the El exchanger • Use of only two pipes between the cold box B containing the heat exchanger E2 and the heat exchanger El, these pipes having to transport an inert fluid 4, 5 • Use of an intermediate cycle between the natural gas and the cold box where the hydrogen is cooled to avoid direct injection of natural gas or LNG into the exchanger where the hydrogen is cooled and thus overcome problems of compatibility of design pressures, leakage between fluids, the risk of freezing, • The El exchanger where the natural gas is heated is subject to accelerated fatigue, the use of two El, E2 exchangers makes maintenance or replacement of part of the El unit easier if necessary or an exchanger technology different from that of the E2 and more adapted to the operating conditions of LNG (shell and tube exchanger or printed plate exchangers, in English: “Printed Circuit Heat Exchangers (PCHE)”) • This arrangement makes it possible to exploit the cold of natural gas or LNG on several units by limiting the number of devices in which the natural gas or LNG circulates: the cold is distributed by the intermediate fluid.
[0032] The first exchanger E1 may be located elsewhere than the second exchanger E2, for example in a port.
[0033] The flow 5 sent to the heat exchanger E2 may constitute only a part of the intermediate fluid cooled in the heat exchanger EL. In this case, another part of the intermediate fluid cooled in the first heat exchanger El is sent to another second heat exchanger where it is used to cool another flow of hydrogen and another first cycle fluid before being returned to the first heat exchanger EL.
[0034] The first heat exchanger E1 and at least one of the second heat exchangers E2 may be located at least 500m, or even at least 1 km, from each other.
[0035] The intermediate fluid line 5 will need to be thermally insulated but the intermediate fluid line 4 is preferably at a temperature above 0°C and does not need thermal insulation.
Claims
Claims
1. A method of cooling a flow of hydrogen gas (1) wherein: i. A flow of natural gas at less than -100°C or a flow of liquefied natural gas (23) heats up, or even vaporizes, in a first heat exchanger (El) by heat exchange with an intermediate fluid (4) which cools ii. The flow of hydrogen gas is cooled in a second heat exchanger (E2) of the plate and fin type by heat exchange with the intermediate fluid (5) cooled in step i), at least a portion of the intermediate fluid arriving in the second heat exchanger at a first temperature T1, the flow of hydrogen gas entering the second heat exchanger at a first end thereof and leaving the second exchanger at a second end thereof iii. The at least part of the intermediate fluid cools in the second exchanger a first compressed cycle fluid (11) in at least one first compressor (C3, C4), at least one part (13) of the first cycle fluid leaves the second exchanger at a second temperature T2, is expanded in a turbine (T) and is sent to the second heat exchanger at a third temperature T3 lower than T2, heats up in the second heat exchanger to a fourth temperature T4 higher than the third temperature T3 and is sent at this fourth temperature to the inlet of the at least one first compressor iv. The at least a portion of the intermediate fluid heats up in the second exchanger, exits the first end thereof and is returned to the first heat exchanger to cool against the natural gas and v. At least one second cycle fluid (6) heats up in the second heat exchanger, is compressed in at least one second compressor (Cl, C2) having a suction temperature which is a fifth temperature T5, is sent to the first end of the second heat exchanger and cools down to the second end of the second heat exchanger.
2. A method according to claim 1 wherein the natural gas flow (23) at less than -100°C or the liquefied natural gas flow is heated in the first heat exchanger (El) to a temperature above 0°C.
3. Method according to one of the preceding claims in which at least one of the first, second, third, fourth and fifth temperatures is less than -100°C, or even less than -120°C.
4. Method according to one of the preceding claims in which the first temperature T1 is higher than the second temperature T2 and / or the fourth temperature T4.
5. Method according to one of the preceding claims in which the second temperature T2 is greater than -150°C.
6. A method according to any preceding claim wherein another portion of the intermediate fluid cooled in the first heat exchanger is sent to another second heat exchanger where it serves to cool another hydrogen flow and another first cycle fluid before being returned to the first heat exchanger.
7. A method according to any preceding claim wherein the first heat exchanger and the second heat exchanger are located at least 500 meters apart.
8. Method according to one of the preceding claims in which the first heat exchanger (El) is of the shell and tube exchanger type or printed plate exchangers.
9. Method according to one of the preceding claims in which the first cycle fluid (11, 13, 15) is nitrogen or a mixed refrigerant.
10. Method according to one of the preceding claims in which the second cycle fluid (6,8,9) is hydrogen and / or helium and / or neon and / or a mixed refrigerant.
11. Method according to one of the preceding claims in which the intermediate fluid (4,5) is nitrogen or argon or propane.
12. Method according to one of the preceding claims 1 to 10 in which the intermediate fluid (4, 5) contains between 40 and 50 mol% methane, between 0 and 10 mol% propane or propylene, between 5 and 20% pentane and between 40 and 50% ethylene or ethane.
13.
14. Method according to one of the preceding claims in which the composition of the intermediate fluid (4, 5) is such that it is in the dense phase after cooling in the first exchanger (El) and circulates by means of a pump. Apparatus for cooling a flow of hydrogen gas (1) comprising a first heat exchanger (El), a second plate-fin type heat exchanger (E2), at least one first compressor (C3, C4), at least one second compressor (C1, C2), a turbine (T), a pipe for sending a flow of natural gas at less than -100C or a flow of liquefied natural gas (23) to heat up, or even vaporize, in the first heat exchanger by heat exchange with an intermediate fluid (4) which cools, a pipe for sending the cooled intermediate fluid to the second heat exchanger, a pipe for sending the flow of hydrogen gas to a first end of the second heat exchanger to cool in the second heat exchanger by heat exchange with the cooled intermediate fluid (5) in step i),at least a portion of the intermediate fluid arriving in the second heat exchanger at a first temperature T1, a pipe for exiting the hydrogen flow from the second exchanger at a second end thereof, means for sending a first cycle fluid compressed in the at least one first compressor to the second heat exchanger, a pipe for exiting at least a portion of the first cycle fluid from the second exchanger at a second temperature T2 connected to the turbine, a pipe for sending the expanded fluid in the turbine to the second heat exchanger at a third temperature T3 lower than T2, a pipe for sending the expanded fluid heated in the second heat exchanger up to a fourth temperature T4 higher than the third temperature T3 at the inlet of the at least one first compressor,a conduit for sending the at least a portion of the heated intermediate fluid in the second exchanger from the first end thereof to the first heat exchanger to cool against the natural gas, a conduit for sending at least a second cycle fluid heated in the second heat exchanger to be compressed in the at least one second compressor having a suction temperature which is a fifth temperature T5, a conduit for sending the second compressed fluid from the at least one second compressor to the first, end of the second heat exchanger and a conduit for discharging the second cooled fluid from the second end of the second heat exchanger.