FR3043164A1 - PUMP FOR TRANSFERRING A LIQUEFIED GAS - Google Patents

Abstract

The invention relates to a liquefied gas transfer pump (15) comprising a pump body and a impeller (41) rotatably mounted inside the pump body and provided with magnets (42) arranged the periphery of the wheel, the pump further comprising an inductor (120) arranged to drive the wheel in rotation through the magnets.

Description

Pump for the transfer of a liquefied gas TECHNICAL FIELD

The present invention applies in particular to a device for transporting and / or storing a liquefied gas and to a process for transferring - or delivering - liquefied gas from this device.

The present invention is particularly applicable to containers and tanks for transporting or storing refrigerated gases, such as oxygen, nitrogen, argon, or liquefied natural gas, for example, which are stored at a pressure of 10% or more. About 10 to 20 bar, for example.

STATE OF THE ART

The transfer of a liquefied gas contained in a pressurized container to a gas storage tank, usually referred to as "unloading", can be carried out using a pressure difference - this transfer mode being usually described as " gravitational dumping "- or by pumping.

Gravity debiting requires that the pressure in the container is sufficiently greater than the pressure in a "client" reservoir to be filled, so that the liquefied gas moves in a transfer circuit connecting the container to the tank, under the sole effect of the difference between these two pressures.

During the transfer, the pressure in the container decreases due to the escape of the liquid phase present in the lower part of the container, in the transfer circuit, so that the flow of transferred gas also decreases.

To (partially) compensate for these decreases in pressure and flow rate, it is known to equip the container with a recirculation circuit which connects the bottom of the container to the upper part of the container, and in which a heat exchanger is provided. arranged to heat the liquid phase escaping from the container by this circuit, and to cause the boiling of this liquid phase, the gas phase resulting from this boiling returning to the gaseous surface of the container by this circuit, thus causing an increase in the pressure in the container. The heat exchanger ensures a heat exchange between the gas flowing in the heat exchanger and a hot source which may for example be ambient air, this heat exchanger then being qualified as an atmospheric heater.

The (partial) compensation of the pressure drop in the container by the recirculation (and reheat) circuit also decreases during the transfer due to the (progressive) lowering of the level of the liquid phase in the container.

Consequently, the unloading is carried out most often by pumping, with the aid of a pump provided in the transfer circuit serving to supply the tank with liquefied gas.

A liquefied gas transfer pump - or cryogenic pump - generally includes a pump body and a rotatably mounted impeller within the pump body.

As described in the patent FR2822927, part of the liquid phase discharged by the pump can circulate in an exchanger ensuring the evaporation of this liquid phase to compensate for the pressure drop in the container, as well as the condensation of a gaseous phase withdrawn in the gaseous sky of a tank fed by the container.

As described in the patent FR2439881, such a pump must be cooled ("cold setting") before the pump starts, by "natural" circulation ("gravity") of the liquefied gas through the pump, which generally requires a tedious wait, which can in some cases last one or more hours before you can start the pump.

In addition, despite the use of methods and devices for starting the pump as described in that patent FR2439881, the correct startup and operation of the pump remain significant sources of difficulties for a normally qualified operator.

Indeed, in particular, the transfer pumps only work properly in a reduced range of pressure: below a minimum pressure, the sealing members of the pump leak, and beyond a maximum pressure little greater than the minimum pressure, these organs and / or the pump wear prematurely.

Moreover, the transfer pumps usually driven by an electric motor consume significant energy.

STATEMENT OF THE INVENTION

An object of the invention is to provide a pump for the circulation of a liquefied gas, which is improved and / or which remedies, in part at least, the shortcomings or disadvantages of known pumps for transferring a liquefied gas.

An object of the invention is to provide a pump for transferring a liquefied gas, which requires little - or does not require - cooling prior to startup.

An object of the invention is to propose a device for transporting and / or storing a liquefied gas and a method for transferring - or delivering - liquefied gas from this device, which are improved and / or which remedy, in part at least, to the shortcomings or disadvantages of known systems for transporting, storing, and / or delivering a liquefied gas.

According to one aspect of the invention, there is provided a device for transporting or storing a liquefied gas under pressure, which comprises: a container for containing the liquefied gas under pressure; - A liquefied gas transfer circuit in the liquid phase which is connected to the lower part of the container and which comprises a connecting member to a tank or a gas transport network to be supplied; a circuit for recirculating the liquefied gas which is connected to the upper part of the container and which comprises a heater and a recirculation pump connected in series with the heater, upstream of the heater, and is arranged to pump pumped liquefied gas into the heater; which is taken from the lower part of the container, so as to accelerate the circulation of liquefied gas in the heater, to increase the heat exchange in the heater and to maintain - or increase - the gaseous pressure of the container.

According to another aspect of the invention, there is provided a method for transferring pressurized liquefied gas contained in a container to (in) a tank or a gas transport network, wherein, the container being connected to a fuel circuit. recirculation which comprises a heater and a recirculation / heating pump connected in series with the heater, upstream of the heater, and arranged to discharge into the heater liquefied gas taken from the lower part of the container: - the container is connected to the tank or network to supply, by a liquefied gas transfer circuit (in the liquid phase) which is devoid of pump; the transfer circuit is allowed to transfer or transfer the liquefied gas to the reservoir or to the network under the effect of the overpressure prevailing in the container (compared with the pressure in the reservoir or the reservoir). network); and - operating the recirculation pump to compensate, at least partially, the pressure drop in the container during the transfer.

The recirculation pump may for example be provided to provide a recirculation flow rate of liquefied gas which is in a range of about 10 liters per hour (10 1 / h) to about 1000 (1) / h, and to ensure a pressure rise (head) which is in the range of about one tenth of a bar (bar) to about one bar.

To maintain a sufficient pressure in the container during the transfer of the liquefied gas, in particular to maintain a substantially constant pressure in the container during this transfer, the pressure in the container can be measured and the operation of the pump as a function of measured pressure. For this purpose, the transport or storage device may comprise a pressure measuring sensor arranged to measure the pressure in the container, and a control unit connected to the pump and to the pressure measuring sensor and arranged / configured - in particular programmed - to control the operation of the pump according to the pressure measured by the sensor. The invention is particularly applicable to storage containers which are thermally insulated and which are supported by a transport structure forming part of the gas transport or storage device, in particular by a road transport trailer or by a transport structure by road, by rail, or by boat, which usually includes frames in the format of ISO standards.

The container may have an elongate shape along a horizontal axis.

The recirculation circuit may comprise a non-return valve disposed downstream of the exchanger and serving to prevent the escape of the gas (container) in this circuit when the pump is stopped.

To circulate the liquid phase in the recirculation circuit, according to another aspect of the invention, it is possible to use a pump in which the impeller comprises magnets arranged at the periphery of the impeller, the pump further comprising an inductor arranged to drive the rotating wheel through the magnets.

The gas transport or storage device may comprise electrical energy storage means, such as a battery, for supplying the pump, in particular the inductor of the pump.

In this case in particular, the gas transport or storage device may comprise energy capture means, such as photovoltaic cells, for supplying the energy storage means and / or the pump.

The energy storage and collection means can be secured to and supported by the transport structure and / or the container. The inductor of the pump can be powered by a power supply and control unit which is connected to to the inductor.

This unit and the inductor may be arranged to drive the pump impeller at a rotational speed in the range of about 1000 rpm (rpm) to about 5000 rpm, particularly in a range of from 1500 or 2000 t / m approximately to 4000 or 4500 t / m approximately. Training the wheel by magnetic effect allows in particular to limit - or avoid - the heating of the wheel when the pump is stopped, and therefore facilitates its subsequent start. The inductor is preferably disposed outside the pump body. In particular, the inductor - and / or the coil of the inductor - can extend facing the magnets and the periphery of the wheel.

The coil of the inductor may be embedded in a dielectric and / or thermal insulating material such as a polymeric material, so that heating of the pump body by the inductor can be reduced. The invention makes it possible to produce and use a compact and efficient pump for circulating liquefied gas, which requires little or no cold setting and whose control by a low-skilled operator is facilitated.

At least part of the impeller, in particular a structure or peripheral part connecting the peaks - or heads - of blades - or blades -, in particular a peripheral structure of substantially annular shape, can be made of a magnetic material, in particular a stainless steel (ferro) -magnetic (martensitic or ferritic steel in particular), to promote the drive of the wheel by a magnetic field produced by the inductor. For this purpose also, the magnets can be secured to such a peripheral portion of the wheel and can be arranged substantially flush with the envelope - or envelope surface - peripheral wheel.

The magnets may in particular have a cylindrical cap portion shape, the radius of curvature of which is adapted - in particular substantially equal - to the outer radius of the wheel, in order to minimize the gap separating the magnets from the inductor.

The joining of the magnets to the wheel can be obtained by friction and / or abutment, in particular by mechanical locking or by crimping, in order to avoid the use of an adhesive product capable of reacting with the liquefied gas passing through the pump.

The impeller can be mounted free to rotate on a fixed shaft - or pivot - which is rigidly connected to the pump body by a connecting structure provided / pierced with openings allowing the passage of liquefied gas through this structure.

This connecting structure may comprise - or essentially consist of - a fixed blade grid which may be arranged downstream of the wheel and may form a rectifier to improve the efficiency of the pump.

This connecting structure may have a thermal conductivity lower than the thermal conductivity of the pump body, so as to limit the heating of the wheel by conduction during periods of stopping the pump, and reduce the need for cooling of the pump before a start. For this purpose, at least part of this connecting structure may be non-metallic, in particular made of a synthetic or plastic material such as PTFE.

The connection structure may in particular have a thermal conductivity lower than the thermal conductivity of the wheel, and / or the thermal conductivity of the shaft.

The pump, in particular this connecting structure, may comprise a static sealing member capable of sealing the pump body.

This sealing member may comprise - or essentially consist of - a thin structure of annular shape, such as a thin ring forming a flat seal, which is arranged to seal between two parts of the pump body each provided with a flange, when these two flanges are disposed opposite each other and pinch the thin sealing structure.

The connection between the wheel and the fixed shaft can be achieved by a single bearing, for example by a needle bearing or by a metal / polymer composite bearing such as bronze coated with PTFE, contributing to the compactness of the pump.

The pump body may comprise a central tubular structure delimiting a chamber in which the wheel is housed. Line portion at least of this tubular structure, which extends between the inductor and the periphery of the wheel, may be made of a non-magnetic material, in particular non-magnetic stainless steel.

The chamber may have a cylindrical shape of suitable diameter (little greater) than that of the wheel.

The pump body may further comprise two flared portions, for example of substantially frustoconical shape, disposed on either side of the central tubular structure, in the extension of - ie substantially coaxially with - this tubular structure, so that the together delimits a fluid vein with few accidents or asperities and / or having a passage section substantially continuously variable, to avoid promoting the formation of gas bubbles in the pump body. Other aspects, features, and advantages of the invention appear in the following description which refers to the appended figures and illustrates, without any limiting character, preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 schematically illustrates a device for transporting and storing liquefied gas.

Figure 2 schematically illustrates, in perspective and exploded view, a pump for transferring / circulating liquefied gas.

FIG. 3 schematically illustrates, in perspective view according to another angle of view, and exploded, the pump illustrated in FIG. 2.

FIG. 4 schematically illustrates, in a longitudinal sectional view on an enlarged scale, the central part of a pump similar to that of FIGS. 2 and 3;

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise expressly or implicitly stated, elements or members - structurally or functionally - identical or similar, are designated by identical references in the different figures.

Unless explicitly stated or implied otherwise, the terms "upstream" and "downstream" are used by reference to the flow direction of the liquefied gas.

With reference to FIG. 1, the device 10 serves for the transport and, where appropriate, storage of a liquefied gas 29, 30 under pressure. For this purpose, the device 10 comprises a container 12 of elongate shape along a substantially horizontal axis 13, which is thermally insulated.

For the transport of gas, the container 12 is movable to be moved to near a tank 25 to fill with liquefied gas.

In the embodiment illustrated in FIG. 1, the reservoir 25 has an elongated shape along a substantially vertical axis 26, and is connected to the device 10 by a connection member 24 consisting essentially of a conduit 24 for transporting the liquefied gas, which can be a flexible / flexible conduit.

For the (temporary) storage of the gas, the container 12, which can be fixed, can be connected to a gas transport network 24 to be supplied.

In the container 12, the gaseous phase 30 overcomes the liquid phase 29 of the liquefied gas which can be maintained in this container at a temperature in the range of minus about 200 degrees Celsius (-200 ° C) to -50 ° C about, for example.

The container 12 is mounted on a road transport trailer for moving the container 12, this trailer being schematically shown in Figure 1 in the form of wheels 14.

Alternatively, the container 12 can be secured to a structure (not shown) for transport by boat, which can be part of the volume of an ISO container, for example.

To supply liquefied gas tank 25 or a gas transport network, the device 10 comprises a liquefied gas transfer circuit in the liquid phase.

This circuit comprises a conduit 17 which is connected in the lower part of the container 12 and opens into this container through a first end of the conduit 17.

The transfer circuit also comprises an isolation valve 18 provided at a second end of the conduit 17 and for closing this conduit.

The conduit 24 connecting the device 10 to the reservoir 25 extends the conduit 17 beyond the valve 18.

The device 10 also comprises a liquefied gas recirculation circuit which is connected to the upper part of the container and opens into this container through an end of a duct 22 forming part of this circuit.

The recirculation circuit comprises, successively connected two by two (that is to say in series): i) a conduit 19 connected to the conduit 17; alternatively, the conduit 19 may be connected in the lower part of the container 12 by opening into this container; ii) a recirculation pump 15 connected to the duct 19 by its suction port and provided for drawing liquefied gas in the liquid phase transported by this duct; iii) a conduit 20 connected to the discharge port of the pump 15; iv) a heater 11 connected to the conduit 20 for receiving the liquefied gas pumped by the pump and transported by the conduit 20, and to cause evaporation of the gas, by heat exchange with a hot source such as ambient air; v) the conduit 22 for conveying the gas escaping from the heater 11, generally in gaseous form, to the container 12, which may be equipped with an anti-return valve 21 preventing the escape of the gas head 30 from the tank 12 towards the heater 11.

As detailed below with reference to FIGS. 2 to 4, the pump 15 comprises a pump body, a rotor wheel rotatably mounted inside the pump body, and an electric motor for driving the wheel in rotation.

The motor comprises a permanent magnet armature integral with the wheel and an inductor disposed outside the pump body.

The impeller is of the "helix" or "axial" type, ensuring a displacement of the liquefied gas pumped substantially along the axis of rotation of the wheel which is substantially coincidental with an axis of axial symmetry of the pump body.

The motor of the pump can be supplied with electrical energy by an electrical distribution network to which the motor of the pump 15 is connected.

Alternatively or in addition, the motor can be supplied with electrical energy by a battery 32 for storing electrical energy that can be secured to the transport structure and / or the container 12, and which is connected to the motor of the pump 15.

In this case in particular, the device 10 may comprise photovoltaic solar cells 31 serving to supply the storage battery 32 and / or the pump 15, which may be integral with the transport structure and / or the container 12.

In order to make it possible to control the operation of the pump so as to ensure a determined pressure in the container 12 during the filling of the reservoir 25, the device 10 may comprise a pressure measurement sensor 23 arranged to measure the pressure prevailing in the air. container 12, and a control unit 16 connected to the pump 15 and the sensor 23 and arranged - in particular programmed - to control the operation of the pump 15 as a function of the pressure measured in the container 12.

With reference to FIGS. 2 to 4, the cryogenic pump comprises a pump body 70, 80, 100 and a impeller 41 rotatably mounted inside the pump body, along an axis of rotation 40 which is an axis general symmetry of the pump and most of the parts that form it.

The pump body comprises a central tubular structure 100 delimiting a cylindrical chamber 110 in which is housed the wheel 41, the chamber 110 having a cylindrical shape, with an axis 40 and an inside diameter little greater than the outside diameter of the wheel.

The wheel 41 has magnets 42 arranged at the periphery of the wheel and regularly spaced.

The wheel 41 comprises an annular peripheral ring 44 connected to the apices of the blades 45 which the crown encircles.

The magnets 42 are secured to the peripheral ring 44 of the wheel and are arranged substantially flush with the peripheral envelope of the wheel.

The magnets 42 have a cylindrical cap portion shape whose radius of curvature is adapted to the outer radius of the ring 44 and / or the wheel 41.

The ring 44 has, on its outer face, notches 43 of identical shape and dimensions adapted to that of the magnets, which are regularly spaced along the contour of the wheel.

The magnets 42 are inserted in the notches 43 and are held in place by means of a second ring 46 whose diameter is adapted to that of the first ring 44, so that the ring 46 can be secured to the first ring 44 by crimping for example, so as to ensure the mechanical attachment of the magnets at the periphery of the wheel.

At least part of the wheel 41, in particular the rings 44, 46, is (are) preferably made of a magnetic material such as a ferromagnetic stainless steel.

The wheel 41 is rotatably mounted along the axis 40, inside the chamber 110, on a fixed shaft 50. The shaft 50 comprises a cylindrical bearing surface 51, of axis 40, on which is engaged a bearing 90, for example a needle bearing, which forms a bearing for the wheel 41, allowing the free rotation of the wheel on the shaft 50.

Each end 52, 54 of the shaft 50, which extends respectively upstream and downstream of the wheel 41, i.e. respectively left and right of the wheel in Figures 2 and 3, has a shaped shape for guiding the liquefied gas before (respectively after) its passage in the wheel. The shaft 50 is rigidly connected to the pump body by a connecting structure 60 pierced with openings 61 allowing the passage of liquefied gas through this structure.

The connecting structure 60 is fixed to the second end 53 of the shaft 50 and extends downstream of the wheel 41.

The structure 60 comprises a grid of blades 62 fixed defining the openings 61, capable of forming a rectifier, and connecting a central portion of the structure 60 to an annular peripheral portion of the structure 60.

The pump further comprises an inductor 120 for producing a magnetic field for driving the rotating wheel through the magnets.

The tubular structure 100, which extends between the inductor and the periphery of the wheel, is made of a non-magnetic material. The inductor 120 is disposed outside the pump body, facing and around the tubular structure 100, and facing and at a short distance from the magnets located at the periphery of the wheel.

The coil of the inductor is embedded in an insulating material 121 which thus separates the winding from the tubular wall 100 forming part of the pump body.

The pump body further comprises two tubular sections 70, 80 respectively comprising two flared portions 72, 82 which are arranged on either side - and in the extension - of the central tubular structure 100.

The connecting structure 60 comprises a collar 63 extending along a plane perpendicular to the axis 40 and protruding outside the chamber 110 receiving the shaft 50, the wheel 41, and a substantial portion of the structure 60.

The flange 63 forms a static sealing member for sealing between the two parts 70, 80, 100 of the pump body which are respectively provided with a flange 71, 81, when these two flanges are arranged facing each other. and assembled by bolts 91, 92 by pinching the flange 63, as illustrated in FIG. 4.

Claims (12)

A liquefied gas transfer pump (15) - or cryogenic pump - which comprises a pump body and a impeller (41) rotatably mounted within the pump body, characterized in that the impeller comprises magnets (42) disposed at the periphery of the impeller, the pump further comprising an inductor (120) arranged to drive the impeller by means of the magnets. 2 - Pump according to claim 1 wherein the inductor is disposed outside the pump body, facing the magnets and the periphery of the wheel. 3 - Pump according to claim 1 or 2 wherein the coil of the inductor is embedded in a material (121) insulating dielectric and / or thermal. 4 - Pump according to any one of claims 1 to 3 wherein at least a portion of the impeller, in particular a structure (44) peripheral connecting the tips of the blades, is made of a magnetic material, in particular a steel stainless (ferro-) magnetic. 5 - Pump according to any one of claims 1 to 4 wherein the magnets (42) are secured to a peripheral portion of the wheel and are disposed substantially flush with the peripheral envelope of the wheel, the magnets may have a cylindrical cap portion shape whose radius of curvature is adapted to the outer radius of the wheel. 6 - Pump according to any one of claims 1 to 5 wherein the magnets are secured to the wheel by friction and / or abutment, in particular by mechanical locking or crimping. 7 - Pump according to any one of claims 1 to 6 wherein the impeller is rotatably mounted on a fixed shaft (50) rigidly connected to the pump body by a connecting structure (60) pierced with openings ( 61) allowing the passage of the liquefied gas through this structure, the connecting structure may comprise a fixed blade grid (62) disposed downstream of the wheel and forming a rectifier. 8 - Pump according to claim 7 wherein the connecting structure has a thermal conductivity less than the thermal conductivity of the wheel, the thermal conductivity of the pump body, and / or the thermal conductivity of the shaft. 9 - Pump according to claim 7 or 8 wherein the connecting structure comprises a sealing member comprising a structure (63) of annular thin form arranged to seal between two parts (70, 80) of the pump body each provided with a flange (71, 81), when these two flanges are disposed opposite one another and clamp the structure (63) thin sealing. 10 - Pump according to any one of claims 7 to 9 wherein the connection between the wheel and the fixed shaft is provided by a single bearing (51, 90). 11 - Pump according to any one of claims 1 to 10 wherein the wheel (41) provides a displacement of the liquefied gas pumped substantially along the axis (40) of rotation of the wheel, and wherein the pump body comprises a central tubular structure (100) delimiting a chamber (110) in which the wheel is housed, a portion at least of this tubular structure, which extends between the inductor and the periphery of the wheel, being made of a material nonmagnetic, the chamber having a cylindrical shape of diameter slightly greater than that of the wheel. 12 - Pump according to claim 11 wherein the pump body further comprises two portions (72, 82) flared disposed on either side and in the extension - of the central tubular structure (100).