Patent ID: 12203700

DETAILED DESCRIPTION OF THE INVENTION

The cooling and/or liquefaction system in [FIG.1] comprises a refrigeration device1that supplies cold (a cooling capacity) at a cooling exchanger8. The system comprises a duct25for circulation of a flow of fluid to be cooled placed in heat exchange with this cooling exchanger8. For example, the fluid is liquid natural gas pumped from a tank16, then cooled (preferably outside the tank16), then returned to the tank16(for example raining down in the gas phase of the tank16). This makes it possible to cool or subcool the contents and to limit the occurrence of vaporization. To this end, the circulation duct25comprises an upstream end connected to the inside of the tank, in particular in the lower part in order to take liquid therefrom, and an upstream end connected to the tank to return the fluid thereto, for example in the upper part. For example, the liquid from the tank16is subcooled below its saturation temperature (drop in its temperature of several K, in particular5to20K and in particular14K) before being reinjected into the tank16. In a variant, this refrigeration can be applied to the vaporization gas from the tank16in order in particular to reliquefy it.

The low-temperature refrigeration device comprises a working circuit10(preferably closed) forming a circulation loop. This working circuit10contains a working fluid (helium, nitrogen, neon, hydrogen or another appropriate gas or mixture, for example helium and argon or helium and nitrogen or helium and neon or helium and nitrogen and neon).

The working circuit10forms a cycle comprising, in series: a mechanism2,3for compressing the working fluid, a mechanism6for cooling the working fluid, a mechanism7for expanding the working fluid, and a mechanism6for heating the working fluid.

The device1comprises a cooling heat exchanger8intended to extract heat at at least one member25by heat exchange with the working fluid circulating in the working circuit10.

The mechanisms for cooling and heating the working fluid conventionally comprise a common heat exchanger6through which the working fluid passes in countercurrent in two separate passage portions of the working circuit depending on whether it is cooled or heated.

The cooling heat exchanger8is situated for example between the expansion mechanism7and the common heat exchanger6. As illustrated, the cooling heat exchanger8may be a heat exchanger separate from the common heat exchanger6.

However, in a variant, this cooling heat exchanger8could be made up of a portion of the common heat exchanger6(meaning that the two exchangers6,8can be in one piece, i.e. may have separate fluid circuits that share one and the same exchange structure).

Thus, the working fluid which leaves the compression mechanism2,3in a relatively hot state is cooled in the common heat exchanger6before entering the expansion mechanism7. The working fluid which leaves the expansion mechanism7and the cooling heat exchanger8in a relatively cold state is, for its part, heated in the common heat exchanger6before returning into the compression mechanism2,3in order to start a new cycle.

Conventionally, in a normal operating mode (the working gas undergoes the cycle of compression, cooling, expansion and heating and produces cold at the cooling exchanger8), an equal mass flow rate circulates in the two passage portions in the common heat exchanger6.

Thus, as illustrated, in the normal operating mode, a flow of fluid (liquefied natural gas or the like, in particular hydrogen) can be cooled in the cooling exchanger8. In the event that this fluid contains impurities (carbon dioxide or the like) that are likely to solidify as they are cooled, a blockage17or an obstruction may arise in the cooling exchanger8.

To evacuate these impurities created during use (for example after several hours or days of cooling), the system may automatically take up or be disposed manually in a cleaning mode for cleaning away impurities that have solidified in the cooling exchanger8. According to this configuration, the refrigeration device1is stopped and simultaneously, a flow of user fluid is made to circulate in the cooling exchanger8.

The stopping of the refrigeration device1will interrupt the production of cold at the refrigeration heat exchanger8. This heat exchanger8will heat up compared with its cooling configuration. This heating combined with the flow of user fluid will evacuate the solidified impurities by sublimation or vaporization and mechanical evacuation. Specifically, the impurities will dissolve in the flow that sweeps them.

This making of a flow of user fluid circulate in the cooling exchanger8can be realized by the same circulation duct25as feeds the fluid to be cooled, for example by being pumped from a tank16to be cooled.

To further improve the efficiency and rapidity of the process, a purge18of the cooling exchanger8with a flow of purge fluid injected into the cooling exchanger8in order to sweep and evacuate from the cooling exchanger8the impurities detached during the cleaning step can be provided simultaneously with and/or after the cleaning step.

For example, a circuit18of neutral gas or the like (nitrogen for example) may be provided to purge the heated impurities. This purge may, if necessary, replace making the flow of user fluid circulate during heating. The mixture obtained can be evacuated to a discharging zone (to the atmosphere for example).

Alternatively, this purge18may be realized with a flow of user fluid. For example, a user fluid fraction is taken from the circulation duct12(via a bypass9provided with a valve for example). The purge user fluid can vaporize in the cooling exchanger8and detach the impurities. The mixture obtained can be sent back to the outside or a collection zone and can, in particular, be reinjected into the tank16of user fluid.

The device may comprise at least one electronic controller12connected to all or part of the members of the system (motors, valves, pump, etc.). The electronic controller12may comprise a microprocessor or a computer and may be configured to control the system, in particular according to the process described above or below.

The compression mechanism2,3comprises one or more compressors and at least one drive motor14,15for rotating the compressor(s)2,3, the refrigeration capacity of the device being variable and controlled by regulating the speed of rotation of the drive motor(s)14,15(cycle speed).

In the example depicted, the refrigeration device comprises two compressors that form two compression stages and an expansion turbine. This means that the compression mechanism comprises two compressors2,3in series, preferably of the centrifugal type, and the expansion mechanism comprises a single turbine7, preferably a centripetal turbine. Of course, any other number and arrangement of the compressor(s) and turbine may be envisioned, for example three compressors in series and one expansion turbine or two compressors in series and two turbines in series or three compressors in series and two or three turbines in series.

In the example illustrated, a cooling exchanger4,5is provided at the outlet of each compressor2,3(for example cooling with heat exchange with water at ambient temperature or any other cooling agent or fluid). This makes it possible to realize isentropic or isothermal or substantially isothermal compression. Of course, any other arrangement may be envisioned (for example no cooling exchanger4,5having one or more compression stages). Similarly, a heating exchanger may or may not be provided at the outlet of all or part of the expansion turbines7to realize isentropic or isothermal expansion (before or after the cooling exchanger8). Also preferably, the heating and cooling of the working fluid are preferably isobaric, without this being limiting.

For example, the device1comprises two high-speed motors14,15(for example 10 000 revolutions per minute or several tens of thousands of revolutions per minute) for respectively driving the two compression stages2,3. The turbine7may be coupled to the motor2of one of the compression stages2,3, meaning that the device may have a turbine7forming the expansion mechanism which is coupled to the drive motor2of a compression stage2(in particular the first).

Thus, the power of the turbine(s)7can advantageously be recovered and used to reduce the consumption of the motor(s). Thus, by increasing the speed of the motors (and thus the flow rate in the cycle of the working gas), the refrigeration capacity produced and thus the electrical consumption of the liquefier are increased (and vice versa). The compressors2,3and turbine(s)7are preferably coupled directly to an output shaft of the motor in question (without a geared movement transmission mechanism).

The output shafts of the motors are preferably mounted on bearings of the magnetic type or of the dynamic gas type. The bearings are used to support the compressors and the turbines.

Moreover, all or part of the device, in particular the cold members thereof, can be accommodated in a thermally insulated sealed casing (in particular a vacuum chamber containing the cold parts: cooling exchanger8, turbine7, and optionally the common countercurrent heat exchanger).

The invention may apply to a method for cooling and/or liquefying another fluid or mixture, in particular hydrogen.

While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

The singular forms “a”, “an” and “the” include plural referents, unless the context dearly dictates otherwise.

“Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of “comprising.” “Comprising” is defined herein as necessarily encompassing the more limited transitional terms “consisting essentially of” and “consisting of”; “comprising” may therefore be replaced by “consisting essentially of” or “consisting of” and remain within the expressly defined scope of “comprising”.

“Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.