Equipment and method for cooling a fluid

Abstract

Disclosed is an installation for cooling a fluid to cryogenic temperatures, comprising a circuit (2) for the fluid to be cooled, comprising an upstream end connected to a source (21) and a downstream end connected to a cooled and / or liquefied fluid collection member (22), and comprising at least one exchanger (3) for pre-cooling the fluid leaving the upstream end (21), the pre-cooling exchanger (3) exchanging heat with a pre-cooling circuit (9) consisting of a flow of vaporized gas from a user (10), the installation (1) further comprising a heat exchanger assembly (4, 5) for cooling by heat exchange with the circuit (2) of the fluid to be cooled downstream of the pre-cooling exchanger (3), the installation (1) cooling by heat exchange with at least a part of the cooling heat exchanger assembly (4, 5). The cooling device (6, 11) comprises a first cooler (6) with a cooling cycle of a cycle gas in an operating circuit, the cycle gas preferably comprising hydrogen and / or helium, the operating circuit of the first cooler (6) comprising a member (7) for compressing the cycle gas, a member (5) for cooling the cycle gas, a member (8) for expanding the cycle gas, and a member (5) for heating the cycle gas, and the pre-cooling exchanger (3) is made of at least one of the following materials: stainless steel or a grade of stainless steel suitable for use at cryogenic temperatures, Inconel, nickel, titanium, or a plastic material.

Description

[Technical Field]

[0001] The present invention relates to a plant and process for cooling a fluid.

[0002] The present invention more particularly relates to a plant for cooling a fluid to a very low temperature, in particular for liquefying hydrogen, comprising a circuit of the fluid to be cooled, with an upstream end connected to a supply source and a downstream end connected to a means for collecting the cooled and / or liquefied fluid, and at least one exchanger for pre-cooling the fluid leaving the upstream end, said pre-cooling exchanger exchanging heat with a pre-cooling circuit consisting of a stream of vaporized gas of a user, the plant additionally comprising a set of heat exchangers for cooling the circuit of the fluid to be cooled downstream of the pre-cooling exchanger, the plant comprising at least one device for cooling by heat exchange with at least a part of the set of cooling heat exchangers, said cooling device comprising a first cooler having a cycle of cooling a cycle gas in its working circuit, the cycle gas preferably comprising hydrogen and / or helium, the working circuit of the first cooler comprising a member for compressing the cycle gas, a member for cooling the cycle gas, a member for expanding the cycle gas and a member for reheating the cycle gas. [Background technology]

[0003] Gas liquefaction plants are designed to deliver saturated liquefied gas (Tout = Tsat(Pout)). A certain amount of gas is therefore produced by evaporation of the generated liquid (evaporation losses). To limit this, the produced gas can be subcooled during its production by the liquefaction unit. This does not regulate or partially regulate the management of the return of evaporated gas (which for example occurs in empty tanks, typically mobile tanks, during their filling).

[0004] The thermal integration of cold gas resulting from the decompression, the so-called "piston" effect of preferentially liquid hydrogen or other liquid vaporization, is complicated to integrate in plants for the production of liquefied gases.

[0005] The recovery of cold energy from these vapors is known, see for example US Patent Application Publication No. 2009158774A.

[0006] This solution is unsatisfactory because these returns of vaporized gas vary over time and depending on thermodynamic conditions (variable temperature / pressure / molar amounts etc.).

[0007] For this reason, known facilities are not suited to these variations as a result of thermal gradients.

[0008] One known solution involves returning this vaporized gas through elements for distribution at different thermal levels in the plant, but the production of the plant can be interrupted due to these variable returns as a result of inaccurate measurements of temperature or local trapping of impurities in the exchange blocks, which can be swept away by these return gases.

[0009] Another solution involves providing local recondensation of this vaporized gas, however this either requires an additional cold source or, due to its inconsistent requirements, requires oversized production units, resulting in potential instability and significant extra costs. Summary of the Invention [Problem to be solved by the invention]

[0010] One object of the present invention is to overcome all or some of the above-mentioned drawbacks of the prior art. [Means for solving the problem]

[0011] For this purpose, the plant according to the invention, and further according to the generic definition provided in the preamble above, is essentially characterized in that the precooling exchanger is made of at least one of the following materials: stainless steel or a grade of stainless steel suitable for use at cryogenic temperatures, Inconel, nickel, titanium or plastic.

[0012] Furthermore, embodiments of the invention may include one or more of the following features: - the pre-cooling exchanger is of the plate, tube or shell and tube type; - The pre-cooling exchanger must also exchange heat with a circuit of refrigerant, e.g., liquefied nitrogen.

[0013] The present invention also relates to a process for cooling a fluid to a very low temperature using a cooling device according to any one of the above or below characteristics, in which the fluid to be cooled is circulated in a circuit of the fluid to be cooled and, before being cooled by a first cooler in a set of cooling heat exchangers, the fluid is pre-cooled in a pre-cooling exchanger by heat exchange with a stream of vaporized gas in a pre-cooling circuit.

[0014] According to other possible distinctive features: the vaporized gas stream of the pre-cooling circuit is circulated intermittently in the pre-cooling circuit, i.e. the pre-cooling exchanger is not continuously cooled by the vaporized gas stream; the pre-cooling exchanger withstands an average temperature difference of 50-100 K between, on the one hand, the situation in which the vaporized gas stream is circulated in the pre-cooling circuit and, on the other hand, the situation in which the vaporized gas stream is not circulated in the pre-cooling circuit; The pre-cooling exchanger also exchanges heat with a circuit of refrigerant, for example liquefied nitrogen, which circulates in said circuit to cool the pre-cooling exchanger when it is not cooled to a predetermined cooling level by the stream of vaporized gas.

[0015] The invention may also relate to any alternative device or method including any combination of the above or below mentioned features within the scope of the claims.

[0016] Other particular features and advantages will become apparent upon reading the following description and upon reference to the drawings. [Brief explanation of the drawings]

[0017] [Figure 1] 1 shows a schematic partial view illustrating an example of the structure and operation of an exemplary embodiment of a cooling plant according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0018] The illustrated refrigeration plant 1 is designed for the liquefaction of a gas, such as for example hydrogen.

[0019] The plant 1 comprises a circuit 2 of a fluid to be cooled, the circuit 2 comprising an upstream end connected to a gas source 21. The source 21 may comprise, for example, a hydrogen network, an electrolyzer, a steam methane reforming (SMR) system or any other source of production of gas (in particular hydrogen) that is liquefied or cooled to a temperature close to its normal liquefaction temperature in the core of the plant.

[0020] The circuit 2 includes a downstream end connected to a member 22 for collecting the cooled and / or liquefied fluid, for example a liquefied gas storage vessel.

[0021] The plant 1 comprises an exchanger 3 for pre-cooling the fluid leaving the upstream end 21. This pre-cooling exchanger 3 performs heat exchange with a pre-cooling circuit 9 in which a stream of vaporized gas of a user 10 can circulate. The vaporized gas can be, for example, hydrogen coming from a tank 10 to be filled, a fixed or mobile storage vessel or any other part of the plant or from an element external to the plant 1.

[0022] The plant 1 additionally includes a set of heat exchangers 4, 5 for exchanging heat with and cooling the circuit 2 of the fluid to be cooled, positioned in series downstream of the pre-cooling exchanger 3. The separate exchangers 4, 5 shown may be joined for any useful purpose to provide a single exchanger.

[0023] The plant 1 includes devices 6, 11 for exchanging heat with at least part of the set of cooling heat exchangers 4, 5 to provide cooling.

[0024] The cooling device includes a first cooler 6 having a cycle for cooling a cycle gas in an operating circuit, the cycle gas preferably containing hydrogen and / or helium. The operating circuit of the first cooler 6 includes a member 7 for compressing the cycle gas (e.g., one or more compressors), a member 5 for cooling the cycle gas (e.g., one or more heat exchangers), a member 8 for expanding the cycle gas (e.g., one or more turbines and / or valves), and a member 5 for reheating the cycle gas (e.g., one or more heat exchangers).

[0025] The pre-cooling exchanger 3 is constructed from at least one of the following materials: stainless steel or a grade of stainless steel suitable for use at very low temperatures (for example below -150°C), Inconel, nickel, titanium or plastic. The return of the chilled vapor gas of the plant 1 is therefore carried out in at least one pre-cooling exchanger 3 preferentially made of stainless steel or any other material presenting very good mechanical characteristics that allow it to withstand thermal gradients much greater than those normally managed in known facilities.

[0026] This structure makes it possible to withstand cold bursts that vary in quantity and time.

[0027] In the case of hydrogen, the material is compatible with operating temperatures below -196°C.

[0028] This therefore makes it possible to take advantage of the cold energy available from the cold gas return in pre-cooling the gas flow to be cooled. In the absence of cold gas return, the pre-cooling exchanger 3 can remain cold for insulation, if necessary, and its cold energy can be recovered when the vapor gas flow arrives. If cold return is not available or is not available at the expected design flow level, the pre-cooling need can be temporarily met by liquid nitrogen or another cold gas or liquid available on site. The exchanger 3 must in this case be sized with three passages and should preferably benefit from an existing utility.

[0029] The large temperature difference in the exchanger 3 makes it possible to have a very compact exchange block (e.g., logarithmic mean temperature difference of 50-100 K). Taking into account the ratio of the hot gas to be cooled to the cold vaporized gas, it is possible to carry out pre-cooling down to a level of about -40°C via a simple pre-cooling heat exchanger 3. This requires neither a power contribution nor complex specific controls and has very low installation costs.

[0030] In the illustrated example, a single pre-cooling heat exchanger 3 is provided. Of course, several pre-cooling exchangers 3 may be provided. For example, two separate pre-cooling heat exchangers 3 may be provided. The first pre-cooling heat exchanger 3 receives vaporized gas (e.g., return from a liquefied gas tank truck) at a temperature typically around 30 K up to 80 K or 100 K, for example, to pre-cool the hydrogen stream in the cycle, and the second pre-cooling heat exchanger 3 is further upstream to use the remaining cold energy (e.g., 80 K to 300 K) to pre-cool the stream to be cooled coming from source 21.

[0031] The fact that the return vapor gas stream is reheated if it is contaminated with any impurities makes it possible to eliminate the traditional operational problems associated with recondensation techniques (in this particular case, there is a risk of freezing of impurities and their storage in the process cold heat exchanger, with potential clogging or possibly the creation of an explosive atmosphere).

[0032] As indicated by the dotted lines, the pre-cooling heat exchanger 3 may, if appropriate, also exchange heat with a circuit 12 of a refrigerant, for example liquefied nitrogen (or any other cooling source). This refrigerant circuit 12 makes it possible, if appropriate, to keep the pre-cooling exchanger 3 cooled when the vapor gas flow is insufficient or zero. This refrigerant circuit 12 may therefore be used alone or in addition to the circuit 9 through which the vapor stream may pass on its way, to cool the pre-cooling heat exchanger 3.

[0033] As also shown, the cooling device may include another member 11 for heat exchange and cooling with part of the set of heat exchangers 4, in particular between the pre-cooling exchanger 3 and the cooling provided by the first cooler 6. This additional cooling member 11 may be a second cooler providing intercooling between the pre-cooling exchanger 3 and the first cooler 6.

[0034] This second cooler 11 may, for example, use another fluid, for example nitrogen, and for example make it possible to pre-cool the fluid to a temperature of 70-100 K. After this cooling, the first cooler 6 provides additional cooling of the circuit 2 to a target temperature (for example the temperature for liquefaction of hydrogen).

[0035] The present structure and process allow for easy recovery of intermittently generated vaporized gas cold energy in a relatively inexpensive manner without constraints.

[0036] The solution is advantageously applied to the liquefaction of hydrogen, but may also be applied to the liquefaction of helium, methane, nitrogen, oxygen or any other fluid.

[0037] The pre-cooling exchanger 3 is configured to withstand temperature changes of more than 200K or 150K, for example.

[0038] This exchanger 3 may be provided to initially pre-cool the hydrogen at ambient temperature through heat exchange with a cryogenic stream, in particular below 80K. The following is a summary of the claims as originally filed: [1] A plant for the liquefaction of hydrogen for cooling a fluid to a very low temperature, comprising a circuit (2) of a fluid to be cooled, having an upstream end connected to a source (21) and a downstream end connected to a member (22) for collecting the cooled and / or liquefied fluid, and a single exchanger (3) for pre-cooling the fluid leaving the upstream end (21), the pre-cooling exchanger (3) exchanging heat with a pre-cooling circuit (9) consisting of a stream of vaporized gas of a user (10), the plant (1) additionally comprising a set of heat exchangers (4, 5) for exchanging heat with the circuit (2) of the fluid to be cooled downstream of the pre-cooling exchanger (3), the plant (1) being connected to at least a part of the set of cooling heat exchangers (4, 5). 1. A plant comprising a device (6, 11) for heat exchange and cooling, said cooling device (6, 11) comprising a first cooler (6) having a cycle for cooling a cycle gas in an operating circuit, said cycle gas comprising hydrogen and / or helium, said operating circuit of said first cooler (6) comprising a member (7) for compressing said cycle gas, a member (5) for cooling said cycle gas, a member (8) for expanding said cycle gas and a member (5) for reheating said cycle gas, said pre-cooling exchanger (3) being made of at least one of the following materials: stainless steel or a grade of stainless steel suitable for use at cryogenic temperatures, Inconel, nickel, titanium or plastic. [2] The plant according to [1], characterized in that the pre-cooling exchanger (3) is of the plate, tube or shell and tube type. [3] The plant according to [1] or [2], characterized in that the pre-cooling exchanger (3) also exchanges heat with a circuit (12) of a refrigerant, for example, liquefied nitrogen. [4] A process for cooling a fluid to a very low temperature using the cooling device according to any one of [1] to [3], wherein the fluid to be cooled is circulated in the circuit (2) of the fluid to be cooled and, before being cooled by the first cooler (6) in the set of cooling heat exchangers (4, 5), the fluid is pre-cooled in the pre-cooling exchanger (3) by heat exchange with a stream of vaporized gas in the pre-cooling circuit (9). [5] The process according to [4], characterized in that the vaporized gas stream of the pre-cooling circuit (9) is circulated intermittently in the pre-cooling circuit (9), i.e. the pre-cooling exchanger (3) is not continuously cooled by the vaporized gas stream. [6] The process according to [4], characterized in that the pre-cooling exchanger (3) withstands an average temperature difference of 50 to 100 K between, on the one hand, a situation in which the vaporized gas stream is circulated in the pre-cooling circuit (9) and, on the other hand, a situation in which the vaporized gas stream is not circulated in the pre-cooling circuit (9). [7] The process according to [5], characterized in that the pre-cooling exchanger (3) also exchanges heat with a circuit (12) of a refrigerant, for example liquefied nitrogen, which circulates in the circuit (12) to cool the pre-cooling exchanger (3) when it is not cooled to a predetermined cooling level by the vaporized gas stream.

Claims

1. A process for cooling a fluid to cryogenic temperatures using a plant for liquefaction of gases, comprising: The plant comprises a fluid circuit (2) for a fluid to be cooled, the fluid circuit (2) comprising an upstream end connected to a supply source (21) and a downstream end connected to a liquefied gas storage vessel (22) for collecting the cooled and / or liquefied fluid, The plant (1) comprises a single pre-cooling exchanger (3) for pre-cooling the fluid leaving the upstream end (21), the single pre-cooling exchanger (3) exchanging heat with a pre-cooling circuit (9) consisting of a stream of vaporized gas in a tank or storage vessel (10); The plant (1) comprises a set of cooling heat exchangers (4, 5) for exchanging heat with the fluid circuit (2) of the fluid to be cooled downstream of the single pre-cooling exchanger (3) to cool it, The plant (1) comprises a cooling device (6, 11) for cooling by heat exchange with at least a part of the set of cooling heat exchangers (4, 5), the cooling device (6, 11) comprising a first cooler (6) having a cooling cycle for cycle gas in an operating circuit; the cycle gas comprises hydrogen and / or helium; The operating circuit of the first cooler (6) comprises, in order along the circulation of the cycle gas, a member (7) for compressing the cycle gas, a member (5) for cooling the cycle gas, a member (8) for expanding the cycle gas, and a member (5) for reheating the cycle gas; said single pre-cooling exchanger (3) being constructed from at least one of the following materials: stainless steel or a grade of stainless steel suitable for use at cryogenic temperatures, Inconel, nickel, titanium or plastic; The fluid to be cooled flows through the fluid circuit (2) of the fluid to be cooled, and the fluid exchanges heat with the vaporized gas stream of the pre-cooling circuit (9) in the single pre-cooling exchanger (3) before being cooled by a first cooler (6) in the set of cooling heat exchangers (4, 5), the vaporized gas stream of the pre-cooling circuit (9) is circulated intermittently in the pre-cooling circuit (9), i.e., the single pre-cooling exchanger (3) is not continuously cooled by the vaporized gas stream; and the single pre-cooling exchanger (3) also exchanges heat with a refrigerant circuit (12) of a refrigerant, e.g., liquefied nitrogen, which refrigerant is circulated in the refrigerant circuit (12) to cool the single pre-cooling exchanger (3) when the single pre-cooling exchanger (3) is not cooled to a predetermined cooling level by the vaporized gas stream.

2. 2. A process according to claim 1, characterized in that the single pre-cooling exchanger (3) is of the plate, tube or shell and tube type.

3. 3. A process according to claim 1 or 2, characterized in that the single pre-cooling exchanger (3) also exchanges heat with a refrigerant circuit (12) of a refrigerant, for example liquid nitrogen.

4. 4. The process according to claim 1, wherein the single pre-cooling exchanger (3) withstands an average temperature difference of 50 to 100 K between, on the one hand, the situation in which the vaporized gas stream is circulated in the pre-cooling circuit (9) and, on the other hand, the situation in which the vaporized gas stream is not circulated in the pre-cooling circuit (9).

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