Method and facility for cooling hydrogen

Abstract

To provide a method and facility for cooling a gas to be cooled, using a hydrogen liquefaction facility.SOLUTION: A method includes, during a start-up phase of a hydrogen liquefaction facility 100, supplying liquefied natural gas 1 to a natural gas circuit, vaporizing at least a portion of the liquefied natural gas in a vaporizer H to obtain vaporized natural gas 26, sending at least a portion of the vaporized natural gas into a natural gas heat exchanger in order to cool the natural gas heat exchanger E1, and starting the cooled natural gas heat exchanger and cooling an intermediate fluid circulating in an intermediate cycle circuit by heat exchange with the liquefied natural gas in the natural gas heat exchanger in order to obtain a cooled intermediate fluid 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [1] The field of the invention is that of installations for liquefying gases to be cooled, in particular hydrogen. The invention also relates to a method for cooling gases to be cooled, in particular hydrogen. [Background technology]

[0002] [2] Hydrogen is an energy carrier that is playing an increasingly important role in the decarbonization of various sectors, particularly transport and industry. Liquefaction of hydrogen makes it possible to store and transport it over long distances.

[0003] [3] It is known practice to liquefy hydrogen in two steps: a first step of pre-cooling hydrogen to a first temperature in a pre-cooling circuit using a cycle gas such as nitrogen or a mixed refrigerant gas, followed by a second step of cooling the pre-cooled hydrogen in a cooling circuit to a second temperature lower than the first temperature using a cycle gas such as hydrogen, helium or a mixed refrigerant comprising a noble gas.

[0004] [4] The hydrogen to be liquefied is therefore circulated in a circuit of hydrogen to be cooled.

[0005] [5] During the pre-cooling step, heat exchanges take place between the cycle gas circulating in the pre-cooling circuit and the gas to be cooled in the gas to be cooled circuit. These heat exchanges take place in a cold box, called an 80K box, in which heat exchangers are positioned to cool the gas to be cooled circuit to a predetermined temperature, in particular a temperature of 80 Kelvin.

[0006] [6] It is known practice to optimize such processes by making them more efficient by using cold from liquefied natural gas (LNG) during the step of pre-cooling the hydrogen to be cooled. In such processes, the cold from the LNG is transferred to an intermediate fluid and ultimately to the gas to be cooled. However, during transient operational phases (start-up, commissioning, mode changes, etc.), the equipment used in such processes (especially heat exchangers and compressors) can be sensitive to significant temperature fluctuations. Steps for cooling the equipment and circuits that allow the cold from the LNG to be transferred are therefore important to ensure the durability of the installation. Summary of the Invention

[0007] [7] The present invention relates to a method for cooling a gas to be cooled, in particular hydrogen, using a hydrogen liquefaction plant, the method comprising, during the start-up phase of the hydrogen liquefaction plant: -supplying liquefied natural gas to a natural gas circuit; - vaporizing at least a portion of the liquefied natural gas in a vaporizer to obtain vaporized natural gas; - passing at least a portion of the vaporized natural gas through a natural gas heat exchanger to cool the natural gas heat exchanger; -activating a cooled natural gas heat exchanger to obtain a cooled intermediate fluid, and cooling the intermediate fluid circulating in the intermediate cycle circuit by heat exchange with the liquefied natural gas in the natural gas heat exchanger; - sending a flow of cooled intermediate fluid into the stopped cryogenic compressor in order to cool the cryogenic compressor, in particular to control the cooling rate of the hydrogen liquefaction plant by monitoring the temperature at the inlet of the cryogenic compressor, in which in particular the cooling rate is, for example, 1°C / min to -50°C at the start and then the cooling rate becomes faster; -activating a cryogenic compressor and compressing the cooled intermediate fluid in the activated cryogenic compressor to obtain a compressed intermediate fluid; - passing the compressed intermediate fluid to a natural gas heat exchanger to obtain a compressed and cooled intermediate fluid, and cooling the compressed intermediate fluid in the natural gas heat exchanger; - pre-cooling the gas to be cooled circulating in the gas to be cooled circuit by heat exchange between at least the compressed and cooled intermediate fluid in the pre-cooling heat exchanger and the gas to be cooled; The present invention relates to a method comprising:

[0008] [8] The compressor, natural gas heat exchanger, and pre-cooling heat exchanger are therefore slowly cooled during start-up of the equipment to avoid thermal shock. Additionally, such a method allows for sequencing the start-up of these thermal shock sensitive items of equipment, thus simplifying start-up of the equipment for the operator.

[0009] [9] In the present application, the term “start-up phase of the liquefaction installation” is given to mean the phase between switching on the installation (for example when the installation is at ambient temperature or at a temperature higher than −50° C.) and the moment when the temperature of the gas to be cooled, measured at the outlet of the pre-cooling heat exchanger, is at a predetermined temperature between 60 Kelvin and 90 Kelvin, preferably between 70 Kelvin and 80 Kelvin.

[0010]

[10] In one aspect according to the invention, the flow rate of the cooled intermediate fluid sent to the shut down cryogenic compressor is less than 60% of the normal operating flow rate of the cryogenic compressor.

[0011]

[11] Such a cooled intermediate fluid flow during a shutdown cryogenic compressor, i.e., when the cryogenic compressor is not providing compression, allows the cryogenic compressor to slowly cool, which in turn allows the material from which the cryogenic compressor is made, e.g., metal, to slowly cool.

[0012]

[12] In one embodiment according to the invention, the flow rate of cooled intermediate fluid sent to the shut down cryogenic compressor is at most equal to 5% of the normal operating flow rate of the cryogenic compressor.

[0013]

[13] Such a flow rate makes it possible to prevent any thermal shock during the slow cooling of the material from which the cryogenic compression is made.

[0014]

[14] In one embodiment according to the present invention, at least a portion of the liquefied natural gas is vaporized in an atmospheric vaporizer.

[0015]

[15] In one aspect according to the invention, liquefied natural gas is supplied to the vaporizer by a liquefied natural gas bypass line configured to divert the liquefied natural gas from the natural gas circuit during a start-up phase of the installation.

[0016]

[16] Liquefied natural gas is a cryogenic fluid that can damage liquefied natural gas heat exchangers if they are not pre-cooled. The vaporizer vaporizes the liquefied natural gas without overheating it before it enters the natural gas heat exchanger, thus allowing the natural gas heat exchanger to cool gradually while avoiding sudden vaporization of the natural gas in the natural gas heat exchanger, which could damage the natural gas heat exchanger due to thermal fatigue.

[0017]

[17] In one aspect according to the invention, the method comprises controlling the flow rate of the portion of the liquefied natural gas sent to the vaporizer, thereby protecting the natural gas heat exchanger from temperature fluctuations.

[0018]

[18] In one aspect of the invention, the flow rate of the portion of the natural gas delivered to the vaporizer is controlled by at least one liquefied natural gas diversion control member configured to control the flow rate of the liquefied natural gas delivered to the vaporizer, the control member being located on the bypass line upstream of the vaporizer.

[0019]

[19] In one aspect of the present invention, when the liquefied natural gas diversion control member is in an open position, at least a portion of the liquefied natural gas is sent to the vaporizer at a flow rate of 5% to 50% of the liquefied natural gas flow rate, and when the liquefied natural gas diversion control member is in a closed position, it prevents the liquefied natural gas from being sent to the vaporizer.

[0020]

[20] In one aspect of the invention, the method comprises controlling a flow rate of liquefied natural gas delivered to a natural gas heat exchanger.

[0021]

[21] In one aspect of the invention, the step of controlling the flow rate of liquefied natural gas delivered to the natural gas heat exchanger is performed by a liquefied natural gas flow control member located on the natural gas circuit upstream of the natural gas heat exchanger.

[0022]

[22] In one aspect of the invention, the liquefied natural gas diversion control element and / or the liquefied natural gas flow control element are control valves or valves provided with positioners. In general, any type of valve that allows the opening rate to be selected may be used.

[0023]

[23] In one aspect of the invention, the natural gas heat exchanger has an operating temperature, particularly an operating temperature between −150° C. and 30° C. For example, in continuous operation the cold end of the heat exchanger is −150° C. and the hot end is ambient temperature.

[0024]

[24] Here, "operating temperature" is given to mean the temperature at which an item of equipment is rated to operate without risk of being damaged, especially by thermal shock. The operating temperature depends on the specifications of the equipment.

[0025]

[25] The present invention is specifically aimed at gradually lowering the temperature to the nominal temperature of the heat exchanger. For example, everything must be initially at ambient temperature and slowly cooled at a maximum rate of 1°C / min to avoid thermal shock. This would not be possible if LNG at -150°C were sent directly into the heat exchanger, even at low flow rates, as this would cause significant local thermal stresses.

[0026]

[26] In one aspect according to the invention, the flow rate of natural gas sent to the liquefied natural gas heat exchanger depends on the temperature of the liquefied natural gas or a mixture of liquefied natural gas and vaporized natural gas measured at the inlet of the natural gas heat exchanger. Advantageously, the invention allows for controlling the temperature so that it is gradually decreased at a maximum rate of 1°C / min.

[0027]

[27] In one aspect of the invention, the temperature of the natural gas heat exchanger is substantially the same as the temperature of the liquefied natural gas or mixture of liquefied natural gas and vaporized natural gas at the inlet of the natural gas heat exchanger.

[0028]

[28] In one aspect of the invention, the operating temperature of the natural gas heat exchanger is reached when the temperature of the liquefied natural gas or the mixture of liquefied natural gas and vaporized natural gas reaches the operating temperature of the natural gas heat exchanger.

[0029]

[29] In one aspect of the invention, once the operating temperature of the natural gas heat exchanger is reached, the method comprises closing the liquefied natural gas diversion control member to prevent vaporization of the liquefied natural gas in the vaporizer, and opening the liquefied natural gas flow control member to admit the flow of liquefied natural gas into the natural gas heat exchanger.

[0030]

[30] In one aspect of the invention, the closing of the diverted flow control member and the opening of the liquefied natural gas flow control member are gradual.

[0031]

[31] In one aspect of the invention, vaporized natural gas is passed through a natural gas heat exchanger until the operating temperature of the natural gas heat exchanger is reached.

[0032]

[32] In one aspect of the invention, the natural gas heat exchanger is cooled as follows: 1. Open the liquefied natural gas flow control element to vaporize a portion of the liquefied natural gas in the vaporizer, and close the liquefied natural gas flow control element to send only the vaporized natural gas to the natural gas heat exchanger; 2. Opening the liquefied natural gas flow control member, mixing the liquefied natural gas and the vaporized natural gas upstream of the natural gas heat exchanger, and sending the mixture of the vaporized natural gas and the liquefied natural gas into the natural gas heat exchanger; 3. When the operating temperature of the natural gas heat exchanger is reached, the liquefied natural gas diversion control member is closed and the liquefied natural gas flow control member is fully opened to allow only liquefied natural gas to pass through the natural gas heat exchanger.

[0033]

[33] In one aspect of the invention, the natural gas heat exchanger is activated once it reaches its operating temperature.

[0034]

[34] In one aspect of the invention, once the natural gas heat exchanger has reached its operating temperature, the method comprises cooling the intermediate fluid by heat exchange between the liquefied natural gas in the activated natural gas heat exchanger and the intermediate fluid, thereby obtaining a cooled intermediate fluid.

[0035]

[35] In one aspect of the invention, during the start-up phase, the cooled intermediate fluid in the natural gas heat exchanger is sent to the cryogenic compressor before being sent to the pre-cooling heat exchanger.

[0036]

[36] In one aspect of the invention, the cryogenic compressor has an operating temperature, specifically, an operating temperature of -150°C to -100°C at the compressor inlet during normal operation. At start-up, the temperature is preferably -50°C to -70°C.

[0037]

[37] In one aspect of the invention, the cooled intermediate fluid at the outlet of the natural gas heat exchanger is diverted from the pre-cooling heat exchanger by a cooled intermediate fluid bypass line and sent upstream of the cryogenic compressor without passing through the pre-cooling heat exchanger.

[0038]

[38] In one aspect of the invention, the method includes controlling the flow rate of an intermediate fluid delivered to a cryogenic compressor.

[0039]

[39] In one aspect of the invention, the step of controlling the flow rate of the intermediate fluid delivered to the cryogenic compressor is performed by at least one cooled intermediate fluid flow control member.

[0040]

[40] In one aspect according to the present invention, the cooled intermediate fluid flow control member comprises at least one valve for discharging the cooled intermediate fluid.

[0041]

[41] In one aspect of the invention, the intermediate fluid flow control member comprises two valves for discharging the intermediate fluid, one of which is positioned upstream of the cryogenic compressor and the other of which is positioned downstream of the cryogenic compressor.

[0042]

[42] In one aspect of the invention, the method comprises measuring the temperature of the cooled intermediate fluid at the inlet of the cryogenic compressor.

[0043]

[43] In one aspect of the invention, the temperature of the cryogenic compressor corresponds to the temperature of the cooled intermediate fluid measured at the inlet of the cryogenic compressor.

[0044]

[44] In one aspect according to the present invention, cooled intermediate fluid discharge valves are positioned upstream and downstream of the cryogenic compressor and configured to control the flow rate of cooled intermediate fluid delivered to the cryogenic compressor depending on the temperature of the cryogenic compressor.

[0045]

[45] In one embodiment according to the present invention, the flow rate of cooled intermediate fluid sent to a shut-down cryogenic compressor is less than 60% of the cryogenic compressor's normal operating flow rate. The low flow rate of cooled intermediate fluid through the cryogenic compressor allows the cryogenic compressor to slowly cool. Preferably, in situations where the compressor is shut down (i.e., the compressor is not providing compression), only a maximum flow rate of 5% of the nominal flow rate (the cryogenic compressor's normal operating flow rate) is allowed through the compressor to avoid driving the compressor wheels at high speed. The purpose is to slowly cool the metal from which the compressor is made.

[0046]

[46] Herein, a "deactivated" cryogenic compressor is given to mean a cryogenic compressor that is not activated and therefore does not compress fluid passing through it.

[0047]

[47] In one aspect of the invention, cooled intermediate fluid not sent to the cryogenic compressor upstream of the cryogenic compressor is discharged from the intermediate cycle circuit, in particular to the atmosphere.

[0048]

[48] ​​In one aspect of the invention, the cryogenic compressor is located on the intermediate cycle circuit.

[0049]

[49] In one aspect of the invention, at least one cooled intermediate fluid discharge valve, particularly a valve for discharging cooled intermediate fluid located upstream of the cryogenic compressor, is configured to send a cooled intermediate fluid flow rate to the compressor that is less than 60%, preferably less than 50%, preferably less than 40% (or even lower) of the cryogenic compressor's normal operating flow rate. This valve, in particular, allows for cooling the interconnecting pipe between the natural gas supply (particularly the natural gas storage unit) and the compressor inlet, which pipe may in some cases be very long, for example, approximately 1.5 km long. Cooling this interconnecting pipe is therefore essential. However, a high flow rate of cryogenic fluid should not be sent to a shut-down compressor. In a situation where the compressor is shut down (i.e., the compressor is not providing compression), only a maximum flow rate of 5% of the nominal flow rate (the cryogenic compressor's normal operating flow rate) is allowed to pass through the compressor to avoid driving the compressor's wheels at high speed. The purpose is to slowly cool the metal from which the compressor is made.

[0050]

[50] In one aspect of the invention, after circulating through the shut-down cryogenic compressor, at least a portion of the cooled intermediate fluid is sent back upstream of the cryogenic compressor, for example by means of a discharge valve positioned downstream of the cryogenic compressor, in order to isolate the cryogenic compressor in a closed circuit when it is shut down, in other words until it reaches its operating temperature. In this situation, it must be ensured that the flow rate of the fluid allowed to circulate through the shut-down compressor does not exceed 5% of the nominal flow rate (normal operating flow rate of the cryogenic compressor).

[0051]

[51] The discharge valve therefore allows a low flow rate of cooled intermediate fluid to be passed through the cryogenic compressor during the start-up phase of the liquefaction plant when the compressor is not yet started, so that the cooling rate of the cryogenic compressor is controlled until it reaches its operating temperature.

[0052]

[52] In one aspect according to the invention, during the step of cooling the compressor, as long as the temperature of the compressor is higher than the operating temperature of the compressor, at least one discharge valve, in particular at least the discharge valve upstream of the cryogenic compressor, is at least partially opened so that at least a portion of the cooled intermediate fluid is discharged.

[0053]

[53] Preferably, during the step of cooling the cryogenic compressor, both cooled intermediate fluid discharge valves, i.e., the discharge valve upstream of the cryogenic compressor and the discharge valve downstream of the cryogenic compressor, are at least partially open as long as the temperature of the cryogenic compressor is higher than the operating temperature of the cryogenic compressor.

[0054]

[54] In the present invention, the cooling rate of the plant is advantageously controlled by monitoring the temperature at the inlet of the compressor (in particular, the cooling rate is 1 degree / min to -50°C at the start, and then the cooling rate can be substantially faster).

[0055]

[55] In one aspect of the invention, the method comprises supplying an intermediate fluid downstream of the cryogenic compressor when the discharge valve is at least partially open, thereby maintaining a stable intermediate fluid velocity in the intermediate fluid circuit.

[0056]

[56] In one aspect according to the invention, once the cryogenic compressor has reached its operating temperature, the method comprises starting the cryogenic compressor. The cooled intermediate fluid may be compressed in the compressor.

[0057]

[57] In one aspect of the present invention, when the cryogenic compressor is activated, it compresses the cooled intermediate fluid to obtain a compressed intermediate fluid.

[0058]

[58] In one aspect of the invention, when the cryogenic compressor is started, the intermediate fluid discharge valve is closed so that the cooled intermediate fluid is not discharged but circulates through the compressor and is compressed therein.

[0059]

[59] In one aspect according to the invention, during the step of starting the cryogenic compressor, at least one cooled intermediate fluid discharge valve positioned upstream of the cryogenic compressor is gradually closed so as to allow progressively higher flow rates of cooled intermediate fluid to be passed through the compressor.

[0060]

[60] In one aspect according to the present invention, when the cryogenic compressor is started, the flow rate of the cooled intermediate fluid circulating through the cryogenic compressor is greater than 60% of the normal operating flow rate of the compressor, preferably greater than 80% of the normal operating flow rate of the compressor, and preferably equal to 100% of the normal operating flow rate of the compressor.

[0061]

[61] In one aspect of the invention, the cooled intermediate fluid flow rate is controlled such that the intermediate fluid temperature measured at the inlet of the cryogenic compressor is reduced by approximately 1°C / min. In other words, the cooled intermediate fluid discharge valve is configured such that the cooled intermediate fluid flow rate sent into the cryogenic compressor reduces the temperature measured at the inlet of the cryogenic compressor by 1°C / min. This first cooling rate (e.g., approximately 1°C / min) is maintained until a predetermined temperature, e.g., -50°C, is reached. Then, once this predetermined temperature is exceeded, cooling occurs at a second cooling rate faster than the first cooling rate, e.g., 50°C to 100°C below the predetermined temperature.

[0062]

[62] In one aspect according to the invention, once the cryogenic compressor reaches its operating temperature, the cryogenic compressor is started and cooled intermediate fluid is delivered to the operating cryogenic compressor until 100% of the cooled intermediate fluid flow is delivered to the cryogenic compressor for compression in the cryogenic compressor.

[0063]

[63] In one aspect of the invention, during the start-up phase of the facility, the intermediate fluid is first cooled in a natural gas heat exchanger, then compressed in a cryogenic compressor, and then sent back into the natural gas heat exchanger without circulating through a pre-cooling heat exchanger.

[0064]

[64] In one aspect of the invention, during the start-up phase of a hydrogen liquefaction facility, the method comprises heating the cooled intermediate fluid in a start-up heat exchanger.

[0065]

[65] In one aspect of the invention, the step of heating the cooled intermediate fluid is performed by exchanging heat between the cooled intermediate fluid and a hotter heat transfer fluid in a start-up heat exchanger. For example, the step of heating the cooled intermediate fluid is performed by exchanging heat between the cooled intermediate fluid and water in a water heat exchanger.

[0066]

[66] The start-up heat exchanger may be used only during start-up to replace the heat supply from the pre-cooling heat exchanger.

[0067]

[67] In one aspect of the invention, the start-up heat exchanger is bypassed during stable operation of the method.

[0068]

[68] Such a step of heating the intermediate fluid allows for consuming cold from the liquefied natural gas transferred to the intermediate fluid to maintain a stable intermediate fluid temperature until the pre-cooling heat exchanger is switched on.

[0069]

[69] In one aspect of the invention, the cooled intermediate fluid is sent to a start-up heat exchanger, and then, once heated, the heated intermediate fluid is sent back to the natural gas heat exchanger and cooled therein again.

[0070]

[70] In one aspect of the invention, once the natural gas heat exchanger is started and then the cryogenic compressor is started, the method comprises cooling the pre-cooling heat exchanger.

[0071]

[71] In one aspect of the invention, the pre-cooling heat exchanger has an operating temperature.

[0072]

[72] In one aspect of the invention, the step of cooling the pre-cooling heat exchanger is performed by: 1. Heat is exchanged between the compressed and cooled intermediate fluid in the pre-cooling heat exchanger and a secondary heat transfer fluid having a higher temperature than the intermediate fluid; 2. When the temperature of the gas to be cooled at the outlet of the gas to be cooled circuit is close to the temperature of the cooled intermediate fluid at the inlet of the pre-cooling heat exchanger, gradually reduce the flow rate of the compressed and cooled intermediate fluid sent into the starting heat exchanger, and gradually increase the flow rate of the compressed and cooled intermediate fluid sent into the pre-cooling heat exchanger; 3. Activating an expansion member configured to expand the cooled and compressed intermediate fluid upstream of the pre-cooling heat exchanger, the expansion member being in particular a booster cooled turbine configured to expand the compressed and cooled intermediate fluid.

[0073]

[73] In one aspect of the invention, an expansion element is arranged in the intermediate cycle circuit downstream of the compressor in the direction of circulation of the intermediate fluid. Compression and expansion of the cooled intermediate fluid makes it possible to optimize the cooling of the pre-cooling heat exchanger and thus the pre-cooling of the gas to be cooled.

[0074]

[74] In one aspect of the invention, the pre-cooling heat exchanger is activated once it reaches its operating temperature.

[0075]

[75] In one aspect of the invention, the secondary heat transfer fluid comprises a portion of the gas to be cooled at the outlet of the pre-cooling heat exchanger.

[0076]

[76] In one aspect of the invention, a portion of the gas to be cooled at the outlet of the pre-cooling heat exchanger is sent to the secondary heat transfer fluid circuit by a branch duct of the circuit of the gas to be cooled.

[0077]

[77] In one aspect of the invention, once the natural gas heat exchanger, cryogenic compressor, and pre-cooling heat exchanger are at their operating temperatures, the equipment is started up and operates in a steady mode.

[0078]

[78] In one aspect according to the invention, the natural gas heat exchanger is a brazed aluminum plate and fin heat exchanger (BAHX), or a stainless steel heat exchanger, or a printed circuit board heat exchanger, or a shell and tube heat exchanger.

[0079]

[79] In one embodiment according to the present invention, the pre-cooling heat exchanger is located in a first cold box, referred to as the 80K box.

[0080]

[80] In one aspect of the invention, when the installation is operating in a stable mode, the method comprises the steps of: The natural gas heat exchanger recovers cold from the liquefied natural gas using an intermediate fluid, and the intermediate fluid is cooled by the liquefied natural gas in the natural gas heat exchanger; the heated intermediate fluid then enters a pre-cooling heat exchanger configured to exchange the cold of the heated intermediate fluid with the cold of the gas to be cooled, the heated intermediate fluid is compressed in a cryogenic compressor, the flow rate of the heated intermediate fluid passing through and compressed therein being greater than 60% of the nominal molar flow rate, preferably greater than 80% of the nominal molar flow rate, preferably 100% of the nominal molar flow rate; the compressed intermediate fluid is sent to a natural gas heat exchanger and cooled therein to a temperature below 90°C, for example to -140°C, to form a cooled intermediate fluid which is sent to a pre-cooling heat exchanger at a temperature of -140°C; the cooled intermediate fluid is thus heated in a pre-cooling heat exchanger and then cooled again in a natural gas heat exchanger to form an intermediate fluid; the intermediate fluid enters the turbine at a temperature at which it leaves the natural gas heat exchanger, the turbine being configured to expand the intermediate fluid and obtain an expanded intermediate fluid; the expanded intermediate fluid is two-phase and is sent to a phase separator where it forms a liquid and a gas; The liquid is vaporized in a heater and combined with the gas to be heated in a second heat exchanger to form a stream to be sent to the cold compressor. All of the gas is compressed in the cold compressor and then in a booster coupled to a turbine. It is the gas compressed in the booster that is sent to the heat exchanger to recover cold.

[0081]

[81] The intermediate fluid then circulates in a closed cycle, removing refrigeration from the liquefied natural gas.

[0082]

[82] The gas to be cooled, e.g., gaseous hydrogen, at ambient temperature, e.g., 20°C, enters the hot end of the pre-cooling heat exchanger, and the gas passes through the pre-cooling heat exchanger from one end to the other, cooling it to a temperature below -150°C, e.g., -180°C. It is then cooled in a heater against liquid from the phase separator to form a gas cooled to -190°C.

[0083]

[83] The cooled gas is then cooled and liquefied in another heat exchanger in known manner. A mixed refrigerant cycle containing hydrogen, helium, or a noble gas provides the required refrigeration.

[0084]

[84] The liquefied natural gas thus provides at least some of the cold required to pre-cool the gaseous hydrogen to −190° C. This may be at least 50%, at least 75%, or at least 99% of the cold required to cool the gaseous hydrogen to −190° C.

[0085]

[85] The invention further relates to an installation for producing a gas to be cooled, in particular a cryogenic fluid, in particular liquefied hydrogen, comprising: a circuit for the gas to be cooled, having an upstream end intended to be connected to a gas source and a downstream end intended to be connected to at least one receiving system, such as a cryogenic storage unit and / or a means of transport; a natural gas circuit in which natural gas, in particular liquefied natural gas, circulates; a natural gas heat exchanger configured to exchange heat of the liquefied natural gas with an intermediate fluid circulating in an intermediate cycle circuit; at least one cryogenic compressor configured to compress the cooled intermediate fluid during a start-up phase of the installation; at least one element for controlling the flow rate of an intermediate fluid located upstream and / or downstream of the cryogenic compressor, wherein the control element is configured to control the flow rate of a cooled intermediate fluid coming from the natural gas heat exchanger, which can circulate in the cryogenic compressor when the latter is stopped during the start-up phase of the installation; at least one pre-cooling heat exchanger configured to exchange heat between at least the cooled intermediate fluid and the gas to be cooled; The present invention relates to an installation for generating a gas to be cooled, comprising:

[0086]

[86] In one aspect according to the invention, an apparatus is configured to implement the method described above.

[0087]

[87] In one aspect according to the invention, the facility comprises a control unit, for example a microprocessor or microcontroller, configured to implement the method described above.

[0088]

[88] In one aspect of the invention, the facility includes a vaporizer configured to vaporize a portion of the liquefied natural gas, the vaporizer being positioned, for example, upstream of the natural gas heat exchanger.

[0089]

[89] In one aspect of the invention, the facility includes a liquefied natural gas bypass line configured to divert liquefied natural gas from the natural gas circuit during a start-up phase of the facility.

[0090]

[90] In one aspect of the invention, the vaporizer is located on the liquefied natural gas bypass line.

[0091]

[91] In one aspect of the invention, the installation includes at least one liquefied natural gas diversion control member configured to control a flow rate of liquefied natural gas delivered to the natural gas vaporizer, the control member being disposed on the bypass line upstream of the vaporizer.

[0092]

[92] In one aspect of the invention, the installation includes a liquefied natural gas flow control member disposed on the natural gas circuit upstream of the natural gas heat exchanger.

[0093]

[93] In one aspect of the invention, the liquefied natural gas diversion control member is configured, in an open position, to direct a flow of vaporized natural gas to the natural gas heat exchanger.

[0094]

[94] In one aspect of the invention, the liquefied natural gas flow control member is configured, in the open position, to direct a flow of liquefied natural gas to the natural gas heat exchanger.

[0095]

[95] In one aspect of the invention, the vaporizer is an atmospheric vaporizer.

[0096]

[96] In one aspect of the invention, the liquefied natural gas diversion control member is configured to direct a flow of vaporized natural gas to the vaporizer in response to a temperature of the natural gas heat exchanger.

[0097]

[97] In one aspect of the invention, the liquefied natural gas flow control member is configured to direct a flow of liquefied natural gas to the heat exchanger in response to a temperature of the natural gas heat exchanger.

[0098]

[98] In one aspect of the invention, the operating temperature of the natural gas heat exchanger is reached when the temperature of the liquefied natural gas or the mixture of liquefied natural gas and vaporized natural gas reaches the operating temperature of the natural gas heat exchanger.

[0099]

[99] In one aspect of the invention, the liquefied natural gas diversion control member is configured to prevent vaporization of the liquefied natural gas in the vaporizer when the operating temperature of the natural gas heat exchanger is reached, and the liquefied natural gas flow control member is configured to admit the flow of the liquefied natural gas into the natural gas heat exchanger.

[0100]

[0100] In one aspect of the present invention, the natural gas heat exchanger is started up once it reaches its operating temperature.

[0101]

[0101] In one aspect of the invention, once the natural gas heat exchanger reaches its operating temperature, it is configured to cool the intermediate fluid by heat exchange between the liquefied natural gas in the natural gas heat exchanger and the intermediate fluid, thereby obtaining a cooled intermediate fluid.

[0102] In one aspect of the invention, the cryogenic compressor is configured to receive a cooled intermediate fluid.

[0103]

[0103] In one aspect of the invention, the cryogenic compressor has an operating temperature, particularly an operating temperature of -150°C to -100°C.

[0104]

[0104] In one aspect of the present invention, the equipment includes a cooled intermediate fluid bypass line configured to divert cooled intermediate fluid from the pre-cooling heat exchanger through the cooled intermediate fluid bypass line and send the cooled intermediate fluid upstream of the cryogenic compressor.

[0105]

[0105] In one aspect of the present invention, the intermediate fluid flow control member comprises two valves for discharging the intermediate fluid, one of which is positioned upstream of the cryogenic compressor and the other of which is positioned downstream of the cryogenic compressor.

[0106] In one aspect of the invention, the method includes a device for measuring the temperature of the cooled intermediate fluid, the measuring device being positioned at the inlet of the cryogenic compressor.

[0107] In one aspect of the invention, the temperature of the cryogenic compressor corresponds to the temperature of the cooled intermediate fluid measured at the inlet of the cryogenic compressor.

[0108]

[0108] In one aspect of the present invention, the cooled intermediate fluid discharge valves are positioned upstream and downstream of the cryogenic compressor and are configured to control the flow rate of cooled intermediate fluid sent to the cryogenic compressor depending on the temperature of the cryogenic compressor.

[0109] In one aspect according to the invention, the flow rate of the cooled intermediate fluid sent to the shut down cryogenic compressor is less than 60%, for example about 5%, of the normal operating flow rate of the cryogenic compressor. The low flow rate of the cooled intermediate fluid in the cryogenic compressor allows for slow cooling of the cryogenic compressor.

[0110]

[0110] Herein, a "deactivated" cryogenic compressor is given to mean a cryogenic compressor that is not activated and therefore does not compress fluid passing through it.

[0111]

[0111] In one aspect of the invention, the discharge valve is configured, in an open position, to direct the cooled intermediate fluid outside the intermediate fluid circuit.

[0112]

[0112] In one aspect of the invention, the exhaust valve is configured to direct the cooled intermediate fluid to the atmosphere in the open position.

[0113]

[0113] In one aspect of the present invention, at least one cooled intermediate fluid discharge valve, in particular a valve for discharging cooled intermediate fluid positioned upstream of the cryogenic compressor, is configured to send intermediate fluid flow to the compressor.

[0114]

[0114] The discharge valve therefore allows a low flow rate of cooled intermediate fluid to be passed through the cryogenic compressor during the start-up phase of the liquefaction facility when the compressor is not yet started, so that the cooling rate of the cryogenic compressor is controlled until it reaches its operating temperature.

[0115]

[0115] Preferably, during the step of cooling the cryogenic compressor, as long as the temperature of the cryogenic compressor is higher than the operating temperature of the cryogenic compressor, both cooled intermediate fluid discharge valves, i.e., the discharge valve upstream of the cryogenic compressor and the discharge valve downstream of the cryogenic compressor, are at least partially opened.

[0116] In one aspect of the invention, the installation comprises an intermediate fluid supply duct downstream of the cryogenic compressor, the duct being configured to supply intermediate fluid downstream of the cryogenic compressor when the discharge valve is at least partially open, thereby making it possible to maintain a stable intermediate fluid velocity in the intermediate fluid circuit.

[0117]

[0117] In one aspect according to the present invention, the cryogenic compressor is configured to be activated when the cryogenic compressor reaches its operating temperature, and the cooled intermediate fluid may be compressed in the compressor.

[0118]

[0118] In one aspect of the invention, when the cryogenic compressor is activated, it is configured to compress the cooled intermediate fluid to obtain a compressed intermediate fluid.

[0119]

[0119] In one aspect of the present invention, when the cryogenic compressor is started, the intermediate fluid discharge valve is in a closed position so that the cooled intermediate fluid is not discharged but circulates through the compressor and is compressed therein.

[0120]

[0120] In one aspect of the present invention, during the step of starting the cryogenic compressor, at least one cooled intermediate fluid discharge valve positioned upstream of the cryogenic compressor is configured to be gradually closed so that the cooled intermediate fluid flow rate passed through the cryogenic compressor becomes gradually higher.

[0121]

[0121] In one aspect according to the present invention, when the cryogenic compressor is started up, the intermediate fluid flow control member is configured to allow a cooled intermediate fluid flow rate into the cryogenic compressor that is greater than 60% of the normal operating flow rate of the compressor, preferably greater than 80% of the normal operating flow rate of the compressor, and preferably equal to 100% of the normal operating flow rate of the compressor.

[0122] In one aspect of the invention, the cooled intermediate fluid flow control member is configured to control the cooled intermediate fluid flow rate such that the intermediate fluid temperature measured at the cryogenic compressor inlet drops by approximately 1°C / min. In other words, the cooled intermediate fluid discharge valve is configured to cause the cooled intermediate fluid flow rate sent into the cryogenic compressor to drop the temperature measured at the cryogenic compressor inlet by 1°C / min. This first cooling rate (e.g., approximately 1°C / min) is maintained until a predetermined temperature, e.g., -50°C, is reached. Then, once this predetermined temperature is exceeded, cooling occurs at a second cooling rate faster than the first cooling rate, e.g., to drop the predetermined temperature by 50°C to 100°C.

[0123]

[0123] In one aspect according to the present invention, once the cryogenic compressor reaches its operating temperature, the cryogenic compressor is started and cooled intermediate fluid is sent to the operating cryogenic compressor until 100% of the cooled intermediate fluid flow is sent to the cryogenic compressor so as to be compressed in the cryogenic compressor.

[0124]

[0124] In one aspect of the invention, during the start-up phase of the facility, the facility is configured so that the intermediate fluid is first cooled in a natural gas heat exchanger, then compressed in a cryogenic compressor, and then sent back into the natural gas heat exchanger without first circulating through a pre-cooling heat exchanger.

[0125]

[0125] In one aspect of the invention, the facility includes a start-up heat exchanger configured to heat the cooled intermediate fluid in the natural gas heat exchanger during a start-up phase of the facility.

[0126]

[0126] In one aspect of the present invention, the start-up heat exchanger is configured to exchange heat between the cooled intermediate fluid and a heat transfer fluid having a temperature higher than that of the cooled intermediate fluid, for example, the heat exchanger is a water heat exchanger configured to exchange heat between the cooled intermediate fluid and water.

[0127]

[0127] The start-up heat exchanger may be used only during start-up to replace the heat supply from the pre-cooling heat exchanger.

[0128] In one aspect of the invention, the start-up heat exchanger is bypassed during stable operation of the method.

[0129]

[0129] In one aspect of the invention, the start-up heat exchanger is configured so that the cooled intermediate fluid is sent to the start-up heat exchanger and then, once heated, sent back to the natural gas heat exchanger and cooled therein again.

[0130]

[0130] In one aspect of the invention, the facility includes a cooled and compressed intermediate fluid expansion member located upstream of the pre-cooling heat exchanger and downstream of the cryogenic compressor.

[0131]

[0131] In one aspect of the invention, an expansion element is arranged in the intermediate fluid circuit downstream of the compressor in the direction of circulation of the intermediate fluid. Compression and expansion of the cooled intermediate fluid makes it possible to optimize the cooling of the pre-cooling heat exchanger and thus the pre-cooling of the gas to be cooled.

[0132]

[0132] In one aspect of the present invention, the pre-cooling heat exchanger has an operating temperature.

[0133]

[0133] In one aspect of the present invention, the pre-cooling heat exchanger is activated once it reaches its operating temperature.

[0134]

[0134] In one aspect of the invention, the facility comprises a heat transfer fluid circuit in which a secondary heat transfer fluid, which is hotter than the cooled intermediate fluid, circulates.

[0135]

[0135] In one aspect of the invention, the secondary heat transfer fluid comprises a portion of the gas to be cooled at the outlet of the pre-cooling heat exchanger.

[0136]

[0136] In one aspect of the present invention, the equipment comprises a branch duct of the circuit of the gas to be cooled configured to send a portion of the gas to be cooled at the outlet of the pre-cooling heat exchanger to the secondary heat transfer fluid circuit.

[0137]

[0137] In one aspect of the present invention, once the natural gas heat exchanger, cryogenic compressor, and pre-cooling heat exchanger are at their operating temperatures, the unit is started up and operates in a steady mode.

[0138]

[0138] In one embodiment according to the present invention, the natural gas heat exchanger is a brazed aluminum plate and fin heat exchanger (BAHX), or a stainless steel heat exchanger, or a printed circuit board heat exchanger, or a shell and tube heat exchanger.

[0139]

[0139] In one embodiment according to the present invention, the pre-cooling heat exchanger is located in a first cold box, referred to as the 80K box.

[0140]

[0140] Further features, details and advantages of the present invention will become more clearly apparent from reading the following description and some illustrative embodiments provided as non-limiting examples, with reference to the attached schematic drawings. [Brief explanation of the drawings]

[0141] [Figure 1]

[0141] Figure 1 is a schematic diagram of the method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0142]

[0142] The features, variations, and various embodiments of the present invention may be combined with one another in various combinations, provided they are not mutually incompatible or mutually exclusive. In particular, where the selection of features is sufficient to give the present invention a technical advantage over the prior art and / or to distinguish the present invention from the prior art, it is possible to envision variations of the present invention comprising only a selection of the features described below, independently of the other features described.

[0143]

[0143] During stable operation, the method for cooling hydrogen operates as follows: The natural gas heat exchanger E1 serves to recover cold from the liquefied natural gas 1 at -150°C using an intermediate fluid cooled by the liquefied natural gas 1 in the natural gas heat exchanger E1. The natural gas heat exchanger E1 can be a brazed aluminum plate and fin heat exchanger, or a stainless steel heat exchanger, or a printed circuit heat exchanger. Alternatively, the natural gas heat exchanger E1 can be a shell and tube heat exchanger.

[0144]

[0144] Liquefied natural gas 1 is heated, for example to 15°C, and optionally vaporized to cool intermediate fluid 5 to a temperature below -50°C, preferably below -120°C. Intermediate fluid 5 is cooled in natural gas heat exchanger E1 to a temperature above -145°C. In this example, it is cooled to -140°C.

[0145]

[0145] Liquefied natural gas 1 enters the cold end of natural gas heat exchanger E1 and exits the hot end as fluid 3.

[0146]

[0146] In this example, the intermediate fluid 5 is nitrogen. It may be, for example, natural gas or methane, or may have another suitable composition. Preferably, the intermediate fluid 5 is inert. The intermediate fluid 5 is preferably at a pressure of 3 to 70 bar abs.

[0147]

[0147] Intermediate fluid 13 leaves pre-cooling heat exchanger E2 at a temperature between -90°C and -150°C, for example -120°C, and is compressed in a first compressor C, for example a centrifugal compressor, to approximately 20 bar. The intermediate fluid compressed to 20 bar is then cooled and compressed in another compressor C1 to a pressure higher than 20 bar. Intermediate fluid 15, above 20 bar, is then sent to the hot end of natural gas heat exchanger E1 at 20°C and cooled therein to a temperature below 90°C, for example -140°C, to form cooled intermediate fluid 27, which is sent to pre-cooling heat exchanger E2 at a temperature of -140°C. Cooled intermediate fluid 27 is heated in heat exchanger E2 to 20°C (forming stream 6), and stream 6 is then cooled against liquefied natural gas in natural gas heat exchanger E1 to form intermediate fluid 5. Intermediate fluid 5 enters turbine E at the temperature it left natural gas heat exchanger E1. The expanded fluid 7 in turbine E at 1.5 bar is two-phase and is sent to a phase separator where it forms a liquid 9 and a gas 11. The liquid is vaporized in heater E3 and joins with the gas 11 to be heated in pre-cooling heat exchanger E2 to form a stream 13 to be sent to cold compressor C. All the gas 13 is compressed in cold compressor C and then in a booster C1 coupled to turbine E. It is the gas compressed in booster C1 that is sent to heat exchanger E1 to recover cold from LNG 1.

[0148]

[0148] The gas to be cooled 23, here gaseous hydrogen, at ambient temperature, for example 20°C, enters the hot end of pre-cooling heat exchanger E2, which it passes through from one end to the other and is cooled to a temperature below -150°C, for example -180°C. It is then cooled in heat exchanger E3 against liquid from the phase separator to form gaseous hydrogen 25 at -190°C.

[0149]

[0149] The cooled gas 25 is then cooled and liquefied in another heat exchanger in known manner. A mixed refrigerant cycle containing hydrogen, helium, or a noble gas provides the required refrigeration.

[0150]

[0150] The liquefied natural gas thus provides at least some of the cold required to pre-cool the gaseous hydrogen to -190°C. This proportion may be at least 50%, at least 75%, or at least 99% of the cold required to cool the gaseous hydrogen to -190°C.

[0151]

[0151] During start-up of the installation, the gas 23 to be cooled is not sent to the pre-cooling heat exchanger E2, which must first be cooled. During start-up of the installation, the method - supplying liquefied natural gas 1 to a natural gas circuit 24; - vaporizing at least a portion of the liquefied natural gas in a vaporizer H to obtain a vaporized natural gas 26; - sending at least a portion of the vaporized natural gas 26 through a natural gas heat exchanger E1 to cool the natural gas heat exchanger; - starting the cooled natural gas heat exchanger E1 and cooling the intermediate fluid 5 circulating in the intermediate cycle circuit by heat exchange with the liquefied natural gas 1 in the natural gas heat exchanger E1 in order to obtain a cooled intermediate fluid; - sending a flow of cooled intermediate fluid 5 into the stopped cryogenic compressor C in order to cool it; - starting a cryogenic compressor C and compressing the cooled intermediate fluid 5 in the cryogenic compressor C in order to obtain a compressed intermediate fluid 15; - sending the compressed intermediate fluid to a natural gas heat exchanger E1 and cooling the compressed intermediate fluid 15 in the natural gas heat exchanger E1 in order to obtain a cooled intermediate fluid 27; pre-cooling the gas to be cooled 23 circulating in the gas to be cooled circuit by heat exchange at least between the cooled intermediate fluid 27 and the gas to be cooled 23; Equipped with.

[0152]

[0152] At least a portion of the liquefied natural gas is vaporized in an atmospheric vaporizer. The liquefied natural gas 1 is supplied to the vaporizer by a liquefied natural gas bypass line 14, which is configured to divert the liquefied natural gas 1 from the natural gas circuit during the start-up phase of the installation. The flow rate of the portion of the liquefied natural gas sent to the vaporizer is controlled by a liquefied natural gas diversion control member 2, which is configured to control the flow rate of the liquefied natural gas sent to the natural gas vaporizer H, the control member being arranged on the bypass line 14 upstream of the vaporizer H. When the liquefied natural gas diversion control member 2 is in the open position, at least a portion of the liquefied natural gas 1 is sent to the vaporizer H at a certain flow rate, and when the liquefied natural gas diversion control member 2 is in the closed position, it prevents the liquefied natural gas 1 from being sent into the vaporizer. The liquefied natural gas can thus be sent directly to the natural gas heat exchanger E1 without being partially vaporized.

[0153]

[0153] The flow rate of the liquefied natural gas 1 sent to the natural gas heat exchanger E1 is also controlled by a liquefied natural gas flow control member 4 arranged on the natural gas circuit upstream of the natural gas heat exchanger E1.

[0154]

[0154] In this example, the natural gas heat exchanger has an operating temperature. The flow rate of natural gas sent to the natural gas heat exchanger E1 depends on the temperature of the natural gas heat exchanger E1, which temperature corresponds to the temperature of the liquefied natural gas 1 or a mixture of the liquefied natural gas 1 and the vaporized natural gas 26 measured at the inlet of the natural gas heat exchanger E1. When the operating temperature of the natural gas heat exchanger is reached, the method comprises the steps of closing the liquefied natural gas diversion control member 2 to prevent vaporization of the liquefied natural gas in the vaporizer H, and opening the liquefied natural gas flow control member 4 to admit the flow of the liquefied natural gas 1 into the natural gas heat exchanger E1. The closing of the diversion control member and the opening of the liquefied natural gas flow control member are gradual. The vaporized natural gas 26 is sent to the natural gas heat exchanger E1 until the operating temperature of the natural gas heat exchanger E1 is reached.

[0155]

[0155] The natural gas heat exchanger E1 is cooled as follows: 1. The liquefied natural gas flow control element 2 is opened to vaporize a portion of the liquefied natural gas in the vaporizer H, and the liquefied natural gas flow control element 4 is closed to send only the vaporized natural gas 26 to the natural gas heat exchanger E1; 2. The liquefied natural gas flow control member 4 is opened, the liquefied natural gas 1 and the vaporized natural gas 26 are mixed upstream of the natural gas heat exchanger E1, and the mixture of the vaporized natural gas and the liquefied natural gas is sent into the natural gas heat exchanger E1; 3. When the operating temperature of the natural gas heat exchanger E1 is reached, the liquefied natural gas diversion control member 2 is closed and the liquefied natural gas flow control member 4 is fully opened to send only liquefied natural gas into the natural gas heat exchanger E1.

[0156]

[0156] When the natural gas heat exchanger reaches its operating temperature, it is started up and the intermediate fluid 5 is cooled by heat exchange between the liquefied natural gas 1 in the natural gas heat exchanger E1 and the intermediate fluid 5. From this, a cooled intermediate fluid is obtained.

[0157]

[0157] During the start-up phase of the hydrogen liquefaction plant 100, the cooled intermediate fluid in the natural gas heat exchanger E1 is then sent to the cryogenic compressor C before being sent to the pre-cooling heat exchanger.

[0158]

[0158] The cryogenic compressor C has an operating temperature, in particular at the inlet of the compressor during normal operation, of -150°C to -100°C. At start-up the temperature is preferably -50°C to -70°C.

[0159]

[0159] The cooled intermediate fluid 5 at the outlet of the natural gas heat exchanger E1 is diverted from the pre-cooling heat exchanger E2 by a cooled intermediate fluid bypass line 5A and sent upstream of the cryogenic compressor C without passing through the pre-cooling heat exchanger E2.

[0160]

[0160] The flow rate of the intermediate fluid 5 sent to the cryogenic compressor C is controlled by at least one cooled intermediate fluid flow control member 8, 10. Here, the member for controlling the flow rate of the cooled intermediate fluid 5 comprises two intermediate fluid discharge valves 8, 10, one of which is positioned upstream of the cryogenic compressor (valve 8) and the other of which is positioned downstream of the cryogenic compressor (valve 10).

[0161]

[0161] During the start-up phase of the hydrogen liquefaction plant 100, the method comprises the step of measuring the temperature of the cooled intermediate fluid 5 at the inlet of the cryogenic compressor C. The temperature of the cryogenic compressor corresponds to the temperature of the cooled intermediate fluid measured at the inlet of the cryogenic compressor.

[0162]

[0162] The cooled intermediate fluid discharge valves 8, 10 are positioned upstream and downstream of the cryogenic compressor C and are configured to control the flow rate of the cooled intermediate fluid 5 sent to the cryogenic compressor C depending on the temperature of the cryogenic compressor C.

[0163]

[0163] The flow rate of cooled intermediate fluid sent to the shut-down cryogenic compressor C during the start-up phase of the installation is less than 60%, for example 5% or less, of the normal operating flow rate of the cryogenic compressor. The low flow rate of cooled intermediate fluid in the cryogenic compressor allows the cryogenic compressor to cool slowly. The cooled intermediate fluid 5 not sent to the cryogenic compressor upstream of the cryogenic compressor C is discharged from the intermediate cycle circuit, in particular to the atmosphere.

[0164]

[0164] After circulating through the shut-down cryogenic compressor C, at least a portion of the cooled intermediate fluid 5 is sent back upstream of the cryogenic compressor by a discharge valve 10 positioned downstream of the cryogenic compressor to isolate the cryogenic compressor in a closed circuit when it is shut down, in other words until it reaches its operating temperature.

[0165]

[0165] The discharge valve therefore allows a low flow rate of cooled intermediate fluid to be passed through the cryogenic compressor during the start-up phase of the liquefaction facility when the compressor is not yet started, so that the cooling rate of the cryogenic compressor is controlled until it reaches its operating temperature.

[0166]

[0166] As long as the temperature of the compressor is higher than the operating temperature of the compressor, at least one discharge valve 8, 10, in particular at least the discharge valve 8 upstream of the cryogenic compressor C, is at least partially opened to discharge at least a portion of the cooled intermediate fluid 5. Both cooled intermediate fluid discharge valves, i.e. the discharge valve upstream of the cryogenic compressor and the discharge valve downstream of the cryogenic compressor, may also be open.

[0167]

[0167] The method comprises the step of supplying an intermediate fluid downstream of the cryogenic compressor C when the discharge valves 8, 10 are at least partially open, so that a stable intermediate fluid velocity can be maintained in the intermediate fluid circuit. This supply is performed by an intermediate fluid supply valve 12.

[0168]

[0168] Once the cryogenic compressor has reached its operating temperature, the method comprises the step of starting the cryogenic compressor. The cooled intermediate fluid can be compressed in the started compressor C. When the cryogenic compressor C is started, the intermediate fluid discharge valves 8, 10 are closed so that the cooled intermediate fluid is not discharged but circulates through the compressor and is compressed therein. The cryogenic compressor C therefore compresses the cooled intermediate fluid 5 to obtain a compressed intermediate fluid 15.

[0169]

[0169] For example, at least the cooled intermediate fluid discharge valve 8 positioned upstream of the cryogenic compressor C is gradually closed so that the flow rate of cooled intermediate fluid 5 passed into the cryogenic compressor C becomes increasingly higher.

[0170]

[0170] When the cryogenic compressor C is started, the flow rate of the cooled intermediate fluid 5 circulating through the cryogenic compressor is greater than 60% of the normal operating flow rate of the compressor, preferably greater than 80% of the normal operating flow rate of the compressor, and preferably equal to 100% of the normal operating flow rate of the cryogenic compressor.

[0171]

[0171] During the start-up phase of the installation 100, the intermediate fluid 5 is first cooled in the natural gas heat exchanger E1, then compressed in the cryogenic compressor C, and then sent back into the natural gas heat exchanger E1 without circulating through the pre-cooling heat exchanger E2.

[0172]

[0172] During the start-up phase of the hydrogen liquefaction plant 100, the method comprises the step of heating the cooled intermediate fluid 5 in the start-up heat exchanger W. This step of heating the cooled intermediate fluid 5 is carried out by exchanging heat between the cooled intermediate fluid 5 in the start-up heat exchanger W and a higher temperature heat transfer fluid. For example, the step of heating the cooled intermediate fluid 5 is carried out by exchanging heat between the cooled intermediate fluid 5 and water in the water heat exchanger W. The start-up heat exchanger W may only be used during start-up to replace the heat supply from the pre-cooling heat exchanger. The start-up heat exchanger W is bypassed during stable operation of the method.

[0173]

[0173] Such a step of heating the intermediate fluid makes it possible to consume cold from the liquefied natural gas that is transferred to the intermediate fluid in order to maintain a stable intermediate fluid temperature until the pre-cooling heat exchanger is switched on.

[0174]

[0174] The cooled intermediate fluid 5 is sent to the start-up heat exchanger W and then, once heated, the heated intermediate fluid is sent back to the natural gas heat exchanger E1 and cooled therein again.

[0175]

[0175] Once the natural gas heat exchanger E1 has been started and then the cryogenic compressor C, the method comprises the step of cooling the pre-cooling heat exchanger E2.

[0176]

[0176] The pre-cooling heat exchanger has an operating temperature.

[0177]

[0177] The step of cooling the pre-cooling heat exchanger E2 is carried out by: 1. Exchanging heat between the compressed and cooled intermediate fluid 5 in the pre-cooling heat exchanger E2 and the secondary heat transfer fluid 27 having a higher temperature than the compressed and cooled intermediate fluid 5; 2. When the temperature of the gas 25 to be cooled at the outlet of the gas circuit to be cooled is close to the temperature of the compressed and cooled intermediate fluid 5 at the inlet of the pre-cooling heat exchanger E2, gradually reduce the flow rate of the compressed and cooled intermediate fluid sent into the starting heat exchanger W and gradually increase the flow rate of the compressed and cooled intermediate fluid 5 sent into the pre-cooling heat exchanger E2; 3. Activating an expansion member E configured to expand the compressed and cooled intermediate fluid upstream of the pre-cooling heat exchanger E2, the expansion member E being in particular a booster cooled turbine configured to expand the compressed and cooled intermediate fluid 5.

[0178]

[0178] Compression and expansion of the cooled intermediate fluid makes it possible to optimize the cooling of the pre-cooling heat exchanger and therefore the pre-cooling of the gas to be cooled.

[0179]

[0179] When the pre-cooling heat exchanger E2 reaches its operating temperature, the pre-cooling heat exchanger is activated.

[0180]

[0180] As shown here, the secondary heat transfer fluid 27 comprises a portion of the gas to be cooled at the outlet of the pre-cooling heat exchanger E2, which portion of the gas to be cooled at the outlet of the pre-cooling heat exchanger E2 is sent to the secondary heat transfer fluid circuit by a branch duct 28 of the circuit of the gas to be cooled.

[0181]

[0181] Once the natural gas heat exchanger E1, the cryogenic compressor C, and the pre-cooling heat exchanger E2 are at their operating temperatures, the plant is started up and operates in steady mode.

Claims

1. 1. A method for cooling a gas to be cooled, in particular hydrogen, using a hydrogen liquefaction plant, said method comprising, during a start-up phase of said hydrogen liquefaction plant, - supplying liquefied natural gas (1) to a natural gas circuit; - vaporizing at least a portion of said liquefied natural gas (1) in a vaporizer (H) to obtain a vaporized natural gas (26); - sending at least a portion of said vaporized natural gas through a natural gas heat exchanger (E1) to cool said natural gas heat exchanger (E1); - starting the cooled natural gas heat exchanger (E1) and cooling the intermediate fluid circulating in the intermediate cycle circuit by heat exchange with the liquefied natural gas (1) in the natural gas heat exchanger (E1) in order to obtain a cooled intermediate fluid (5); - sending a flow of cooled intermediate fluid (5) into the stopped cryogenic compressor (C) in order to cool it, in particular to control the cooling rate of the hydrogen liquefaction plant by monitoring the temperature at the inlet of the cryogenic compressor, in particular, said cooling rate being, for example, 1°C / min to -50°C at the start and then becoming faster; - starting the cryogenic compressor (C) and compressing the cooled intermediate fluid (5) in the started cryogenic compressor to obtain a compressed intermediate fluid (15); - sending the compressed intermediate fluid (15) to the natural gas heat exchanger (E1) and cooling the compressed intermediate fluid (15) in the natural gas heat exchanger to obtain a compressed and cooled intermediate fluid (5); - pre-cooling the gas to be cooled (23) circulating in the circuit of the gas to be cooled by heat exchange between at least the compressed and cooled intermediate fluid (5) and the gas to be cooled (23) in a pre-cooling heat exchanger (E2); A method comprising:

2. 2. The method according to claim 1, characterized in that the method comprises the steps of controlling the flow rate of the portion of liquefied natural gas sent to the vaporizer (H), performed by at least one liquefied natural gas diversion control element (2) configured to control the flow rate of the liquefied natural gas sent to the vaporizer (H), and controlling the flow rate of the liquefied natural gas (1) sent to the natural gas heat exchanger (E1), performed by at least one liquefied natural gas flow control element (4) arranged on the natural gas circuit upstream of the natural gas heat exchanger (E1).

3. 3. The method according to claim 1 or 2, characterized in that the flow rate of the liquefied natural gas (1) sent to the natural gas heat exchanger (E1) depends on the temperature of the liquefied natural gas (1) or a mixture of the liquefied natural gas (1) and the vaporized natural gas (26) measured at the inlet of the natural gas heat exchanger (E1).

4. 4. The method according to claim 2 or 3, characterized in that the natural gas heat exchanger (E1) has an operating temperature, and when the operating temperature of the natural gas heat exchanger (E1) is reached, the method comprises the steps of closing the liquefied natural gas diversion control member (2) to prevent vaporization of the liquefied natural gas (1) in the vaporizer (H) and opening the liquefied natural gas flow control member (4) to admit a flow of the liquefied natural gas (1) into the natural gas heat exchanger (E1).

5. 5. The method according to claim 1, wherein during the start-up phase of the hydrogen liquefaction plant, the cooled intermediate fluid (5) in the natural gas heat exchanger (E1) is sent to the cryogenic compressor (C) before being sent to the pre-cooling heat exchanger (E2).

6. 6. The method according to any one of claims 1 to 5, characterized in that the method comprises a step of controlling the flow rate of an intermediate fluid sent to the cryogenic compressor (C), the step of controlling being performed by at least one intermediate fluid flow control member (8, 10) for controlling the flow rate of a cooled intermediate fluid (5), the intermediate fluid flow control member comprising two intermediate fluid discharge valves (8, 10), one of which is positioned upstream of the cryogenic compressor and the other of which is positioned downstream of the cryogenic compressor (C).

7. 7. Method according to claim 5 or 6, characterized in that the method comprises a step of measuring the temperature of the cooled intermediate fluid (5) at the inlet of the cryogenic compressor (C).

8. 8. The method according to any one of claims 5 to 7, characterized in that the flow rate of cooled intermediate fluid (5) sent to the stopped cryogenic compressor (C) is less than 60% of the normal operating flow rate of the cryogenic compressor.

9. 9. The method according to claim 1, wherein during a start-up phase of the hydrogen liquefaction facility, the method comprises a step of heating the cooled intermediate fluid (5) in a start-up heat exchanger (W), wherein the step of heating the cooled intermediate fluid is performed by exchanging heat between the cooled intermediate fluid (5) in the start-up heat exchanger (W) and a hotter heat transfer fluid.

10. 10. The method according to any one of claims 1 to 9, characterized in that the flow rate of cooled intermediate fluid sent to the shut down cryogenic compressor is less than 60% of the normal operating flow rate of the cryogenic compressor.

11. An installation (100) for producing a gas to be cooled, in particular a cryogenic fluid, in particular liquefied hydrogen, comprising: a circuit for the gas to be cooled (23) having an upstream end intended to be connected to a gas source and a downstream end intended to be connected to at least one receiving system, such as a cryogenic storage unit and / or a means of transport; - a natural gas circuit in which natural gas (1), in particular liquefied natural gas, circulates; a natural gas heat exchanger (E1) configured to exchange heat of said liquefied natural gas (1) with an intermediate fluid (5) circulating in an intermediate cycle circuit; at least one cryogenic compressor (C) configured to compress said cooled intermediate fluid (5) during the start-up phase of said installation; at least one control element (8, 10) for controlling the flow rate of an intermediate fluid (5) located upstream and / or downstream of said cryogenic compressor (C), wherein said control element is configured to control the flow rate of cooled intermediate fluid (5) coming from said natural gas heat exchanger (E1) that can circulate in said cryogenic compressor (C) when said cryogenic compressor is stopped, in order to control the cooling rate of said installation during the start-up phase of said installation, in particular by monitoring the temperature at the inlet of said cryogenic compressor, in particular said cooling rate being, for example, 1°C / min to -50°C at the start and then becoming faster; at least one pre-cooling heat exchanger (E2) adapted to exchange heat between at least said compressed and cooled intermediate fluid (5) and said gas (23) to be cooled; 1. An installation (100) for generating a gas to be cooled, comprising:

12. 12. An installation (100) for generating a gas to be cooled according to claim 11, characterized in that said installation comprises a vaporizer configured to vaporize a portion of said liquefied natural gas.

13. An installation (100) for generating a gas to be cooled according to claim 11 or 12, characterized in that the installation comprises a control unit configured to implement the method according to any one of claims 1 to 10.

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