US3123983A

US3123983A - Means for removal of liquefied gas

Info

Publication number: US3123983A
Authority: US
Priority date: 1961-01-16
Publication date: 1964-03-10
Anticipated expiration: 1981-03-10
Also published as: FI41163C; BE612585A; FR1312710A; NL273426A; ES273584A1; FI41163B; GB959493A

Abstract

959,493. Pumping systems for liquefied gases. CONCH INTERNATIONAL METHANE Ltd. Dec. 1, 1961 [Jan. 16, 1961], No. 43101/61. Headings F1C, F1G, F1R and F1T. [Also in Division B8] A pumping system for liquids such as liquefied natural gases comprises a turbine 16 driving a pump 10 near the bottom of the liquid container and the working fluid has a solidification temperature below the temperature of the liquid 18 in the container 14. The turbine 16 may be driven by a combination of liquid and gas in which case the turbine exhaust fluid passes through a condenser 40 below the liquid level. After passing through the pump, the pressurised liquid is vaporised in a heat exchanger 50 and led to the turbine in an insulated pipe. If the turbine working fluid has a liquefaction temperature below the temperature of the liquid 18 then the pressurised working fluid passes through a pressure regulator fitted externally of the tank. The working fluid may be the vapour from the liquid in which case it is drawn off from the interior of the container (Fig. 4). Vapour from the container may pass into a separator (Fig. 3 not shown) or directly to the turbine 16 via a compressor 68. The exhaust from the turbine may pass into the line 22 and assist the flow of the effluent from the pump 10 in which case the vapour and liquid pass into the separator, the vapour passing to the compressor or back to the container and the liquid passing to a delivery line. In the event of a pump failure, or to assist the pump, compressed vapour may be passed through the delivery line. This pumping system ensures that vapour is returned to the container to counteract any pressure drop as the liquid level falls. In a modified form of this embodiment, (Fig. 4), the turbine exhaust is led directly to an accumulator 82, which also serves as a separator, and the line 70 has a by-pass 82 leading directly to the delivery line 22 the liquid being pumped direct to a separator 102. When the turbine 16 and pump 10 are inoperative the valve 78 and valves 84, 88 may be opened and liquid is pumped by vapour pressure into the accumulator 82, which has a relief valve 98. The liquid drains through lines 90, 92, 106 to a delivery reservoir.

Description

March 10, 1964 c. M. suEPcEvlcl-i MEANS FOR REMOVAL OF' LIQUEFIED GAS 2 Sheets-Sheet 1 Filed Jan. 16, 1961 T1 M a u 102 w 1w T M/ m ell 2 Sheets-Sheet 2 C. M. SLIEPCEVICH MEANS FOR REMOVAL OF LIQUEFIED GAS March 10, 1964 Filed Jan. 16, 1961 l /f//f/f l United States Patent O 3,123,933 MEANS FOR REMOVAL OF LTQUEFIED GAS Cedomir M. Sliepcevieh, Nnrman, Okla., assigner to Couch International Methane Limited, Nassau, Bahamas, a corporation of Bahamas Filed Jan. 16, 1951, Ser. No. 33,036 8 Claims. (Cl. 62-55) This invention relates to a system for the displacement of fluids from within an enclosure and it relates more particularly to a means for the displacement of extremely cold liquids, and especially a liquefied gas such as liquefied natural gas.

Some of the problems confronted in a displacement means of the type described will be set forth with reference to the displacement of liquefied natural gas housed within a large insulated storage container at about atmospheric pressure at a temperature of about 240 F. to 258 F., depending upon the amount of heavier hydrocarbons present in the natural gas. It will be understood that corresponding problems will be found to exist in the removal of other extremely cold liquids such as liquefied air, liquefied nitrogen, liquefied oxygen and the like, from insulated storage containers of large capacity. In the following description of the invention, use will be made of liquefied natural gas as representative of the cold liquids with which this invention is adapted to be practiced. It will be understood that instead of liquefied natural gas, the material displaced can be liquefied air, liquefied nitrogen, etc.

To the present attempts have been made to use submerged displacement pumps located in the bottom of the tank with an elongate drive shaft extending upwardly from the pump through the height of the tank for actuation by a driving motor located outside of the tank. One of the difficulties encountered in an arrangement of the type described resides in the means for sealing the shaft to prevent the escape of vapors from the tank and the means for preventing distortion of the elongate shaft to prevent binding with the tubular housing in which it operates for the displacement of liquid upwardly therethrough. Aside from the basic problems enumerated above, one of the most annoying problems resides in the freezing of the shaft to prevent operation thereof just at the time that it is desired to effect removal of the liquid for unloading at the station of use. Freezing of the shaft appears to result, in part, from foreign material in or about the shaft, which material becomes Stiffened at the low temperature to which the shaft and parts thereof are exposed when the tank is filled with the liquefied gas. Once the shaft becomes frozen, it is thereafter incapable of operation to effect liquid removal until the liquid is otherwise removed or hot gases are passed downwardly through the shaft to enable the shaft and parts associated therewith to become heated up to unfreezing temperature.

One of the means that has been devised to overcome the problem of freezing is continuously to rotate the shaft While the tank is being cooled down and loaded with the liquefied gas so that the shaft will remain free to rotate when reduced to the cold temperature of the liquid. Thereafter, the shaft can be occasionally rotated but it is preferred to continue rotation of the shaft to insure its freedom until placed into operation for removal of liquefied gas from the storage tank.

It will be obvious that considerable risk is entailed in the use of a displacement means for the type described and it will be further apparent that the continuous rotation of the pump shaft is an unreasonable and impractical means for insuring the operation of the pump when it is desired to effect liquid removal.

It is an object of this invention to provide a means for ice the safe and efficient removal or displacement of cold liquids from a storage container.

Another object is to provide a means for fluid displacement which does not make use of an elongate drive shaft extending through the liquid and which would thus be subject to distortion or binding due either to load or ternperature change or both.

A further object is to provide a means for the displacement of a cold liquid, such as liquefied natural gas, wherein use is made of relatively few simple parts which are readily available and easily installed into position of use; which are not subject to wide temperature changes between stages of operation or in operation and therefore free of becoming frozen or otherwise rendered inoperative due either to load or temperature change; which ernbodies an auxiliary means for effecting liquid removal in the event of failure of the pump; which is efficient and economical in operation; which generates sufficient vapor for displacement of the volume of liquid removed, otherwise it would be necessary to make use of a vapor return line from land storage to supply vapor for the liquid being displaced to avoid the development of subatmospheric conditions Within the container, and which can make use of the vapors of the liquids displaced as a driving force thereby to avoid the necessity for maintaining a sealing relationship between the elements and thereby also to make available an endless supply of the driving medium.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings, in which FIG. l is a flow diagram schematically setting forth the arrangement of elements and flow of materials in accordance with the practice of this invention;

FIG. 2 is a flow diagram similar to that of FIG. 1 showing a modification in the means and method for fluid displacement;

FIG. 3 is another flow diagram showing a still further modification;

FIG. 4 is a flow diagram showing still another modification;

FIG. 5 is a flow diagram showing still another modification; and

FIG. 6 is a schematic illustration in section of a still further modification in the liquid flow diagram.

In accordance with the practice of this invention, fluid displacement for the removal of the liquid from the container is effected by a submerged pump lll located adjacent the bottom side 12 of the container le and in which the means 16 for actuating the pump is similarly located so that all of the moving parts are maintained essentially at about the same temperature with very little distance separating the pump and its interconnected actuating means. An imporant concept of this invention resides in the means for operation of said actuating means whereby moving parts subject to temperature differentials are substantially completely avoided and whereby the arrangement is substantially free of elements which might be subject to distortion or binding in a manner to cause failure of the displacement means.

Another important concept of this invention resides in the transmission of power for operation of the pump through liquids or vapors which can be selected to remain free of interferences from the cold liquid adapted to be displaced or else which can be intermixed with said liquid thereby not only to avoid the necessity for seals and problems of handling in use but also to make available new and novel concepts in liquid displacement and replacement of the volume of liquid displaced from the container as well as making available substantially limitless supplies of fluid for use in such power transmission.

This invention can best be described with reference to a displacement pump 10 adapted to be operated by an expansion turbine 16. The pump 10 which is adapted removably to be secured to the bottom side 12 of the tank 14 is of the conventional rotary type having an inlet in communication with the liquid 18 within the tank and an outlet 20 in communication with a delivery pipe 22 which extends upwardly to the top of the tank for connection to other facilities for storage or use of the liquid 18 displaced from the tank.

The turbine drive 16 is also removably secured to the bottom side 12 of the tank 14 with the drive shaft 24 of the turbine operatively connected to the rotor of the pump for actuation thereof. As is conventional of turbine operation, it is provided with an inlet 26 at one end in cornmunication with a feed line 2S through which high pressured iiuid, liquid or gas can be introduced and an outlet 30 at the other end for exhaust of the spent gases, vapors, or liquid into the exhaust line 32.

By placing the pump and its power operating means within the container, many of the problems associated with submerged pumps for displacement of cold liquids can be substantially eliminated. By submerging all of the mechanical elements for fiuid displacement, the pump and moving parts associated therewith will be maintained at a temperature within a few degrees of the temperature of the liquid on which it is adapted to operate. By thus maintaining the pump and its associated parts at uniform temperature during period of use as well as non-use, there is little tendency for the metal parts to deform or to become inoperative due to temperature differentials.

The invention of applicant is capable of a number of novel combinations from the standpoint of construction and operation, as will hereinafter be described. Such novel combinations stem from the possibilities of operating the expansion turbine either by means of a vapor or gas or by means of a liquid or by means of a combination of liquid and gas. Various novel ramifications also stern from the possibility of use of a liquid or a gas which is the same as the liquid or gas with which the container is lled or a liquid or gas other than that which is adapted to be displaced from the container.

FIG. l of the drawings illustrates a system which would be employed in the use of a driving liquid other than the liquid adapted to be displaced from the container, hereinafter referred to as liquefied natural gas, as representative. Suitable driving liquids may be represented by liquid ethane, liquid propane, and liquefied triiiuorochloromethane and other liquids having a boiling point obove and a freezing point below the temperature of the liquefied natural gas.

Under such circumstances, the driving liquid 34 would be made available in a reservoir 36 located outside of the container. From the reservoir, the driving liquid would be fed to a pump 38 where it would be raised in pressure to the level desired for introduction into line 28 communieating the pump 3S with the expansion turbine 16. The spent driving liquid exhausted from the expansion turbine at lower pressure would be returned through line 32 to the accumulator or reservoir 36.

In a system operating over a period of time, it will be apparent that the driving liquid would rapidly approach the temperature of the liquefied natural gas since the driving liquid would be operating within a closed cycle during a large part of which it would be submerged below the liquid level. The heat given up to the liquefied natural gas would stem primarily from ineiiiciencies of the turbine and pump units, including the heat of compression from the compression pump which in a way would be nullified by the cold of expansion during passage through the expansion turbine 16.

In practice, delivery of about 500 gallons of liquefied natural gas per minute couldbe achieved with a pump 20 of about l horsepower and a compressor 38 of about 20 horsepower. The amount of heat lost to the liquefied natural gas due to the inefficiencies previously pointed out would cause the boiling off of about l pound of liquefied natural gas per 1000 pounds of displacement. This would be an amount sufficient to replace the volume of liquid removed from the tank thereby to avoid the necessity of bleeding foreign vapors into the tank to prevent the build-up of sub-atmospheric conditions or else vaporizing additional liquid from product for replacement of the volume of liquid removed from the tank.

FiG. 2 of the drawings represents a system operating on the principles of a heat engine wherein the driving medium is a combination of liquid and gas. Representative are such media as a higher boiling gas such as ethane, propane, butane, isobutane and the like, or other working medium which has a condensation point at a temperature above the temperature of the liquid in the tank but a freezing point at a temperature below the temperature of the liquid in the tank.

Starting with the driving medium exhausted from the turbine lr6, the medium in the form of a vapor is advanced through a condenser 40 in heat exchange relationship with the cold liquefied natural gas in the container to condense the driving medium to a liquid. It will be apparent that the body of cold liquid 18 will be able to condense the vapors exhausted from the expansion turbine l6 so that the exhaust line 42 may itself serve as the condenser. For best practice, the condenser 40 should operate to produce a sub-cooled liquid. The absolute pressure in the condenser should be greater than Hd/ 1444-1 Where H is the height of the line 44, d is the density of the liquid in line 44 and P is the absolute pressure of the inlet side of the pump 46.

From the condenser 40 the condensed driving liquid is passed through line 44 to a pump 46 located outside of the container where the condensate is pressurized to a high level with very little expenditure of power. The pressurized working liquid is passed through line 48 to a heat exchanger 50 for passage in heat exchange relationship with an elevated temperature medium such as air, water or steam tov heat the compressed working liquid to vaporize the compressed liquid to produce a large amount of gas at high pressure for passage through line 52 to the inlet of the expansion turbine 16. In order to minimize condensation of the high pressure gas during passage through the body of the liquid 18 to the turbine lo, the portionof the line 28 submerged in the iiquid is adapted to be insulated.

The principle of operation is to transfer heat from a high temperature driving medium to the always present low pressure liquid in storage whereby enough work can be made available to pump the liquefied gas for removal from the container. The cycle described is one that embodies high eliiciency, especially from the standpoint of power requirements. Again the amount of heat transferred is suiiicient to boil off an amount of liquid in storage to replace the volume of liquid displaced by the pump.

The system shown in FIG. 3 is a modification of the system of FIG. l with the exception that the motive fluid is a gas preferably having a liquefaetion temperature and a freezing point temperature below the temperature of the liquid I8 within the container 14. If the liquid 18 comprises liquefied natural gas, the driving gas can be selected of such media as nitrogen, helium or the like. The driving gas is fed from a reservoir 5S through line 59 to a compressor pump 60 wherein the gas is raised t0 a high pressure for advancement through line 6l to a pressure regulator in the form of a surge pot 62. From the surge pot, the pressurized gas is fed through line 28 to the inlet of the expansion turbine 16. The expanded gas is exhausted from the turbine into line 32 for return to the accumulator 5S.

In FIG. 4 there is illustrated a system operating on a gaseous phase similar to that of the flow diagram of FIG. 3 but in which the gaseous driving fluid is the same as the gas from the liquid being displaced from the container. In the illustrated modification, wherein the liquid displaced from the container is liquefied natural gas, the

working medium would comprise natural gas. When use is made of natural gas as the driving fluid, the various novel ramilications are possible including utilization of the exhaust as a gas lift for discharge of the liquelied natural gas from the container either alone, in the event of failure of the pump, or in combination therewith. Further, the driving fluid can be exhausted into the container thereby to avoid the closed circuit necessary when strange materials are employed and thereby also to make driving lluid available from the vapor always present in the portion of the container above the liquid level.

In the system illustrated in FlG. 4, vapor within the container above the liquid level can be withdrawn for use as a driving lluid through line dltiittted with a two-way check valve 65. The vapor withdrawn is passed through line 66 to a compressor 63 wherein the vapor is raised to a high pressure for passage through line '70 to the inlet of the expansion turbine lo which operates to drive the centrifugal pump lll for the displacement of liquid 13 through the line 22. The expanded vapors exhausted from the turbine lr6 are passed through line '72 into the line 22 whereby the exhausted gas rises through the line 22. to function as a gas litt which is eiective to raise the liquefied gas in line 22 to function as a removal means. Since the material removed through the delivery line 22 will contain both the vapor and liquid, it communicates with a separator 74 wherein the vapor phase is separated from the liquid phase. The liquid product drains from the separator into the line 76 for delivery while the vapor may be utilized to supply the working medium in line 66 or else returned to the vapor space within the tank in the event that an amount of vapor beyond that required for operation of the expansion turbine is available. It is for this reason that a two-way valve 65 is en ployed in line 6ft, in one position to admit vapor from the separator into the tank and in another position to permit withdrawal of vapor from the tank in the event that more is needed as a working medium.

The system shown in FIG. 4 is capable of further modification to eliect liquid removal in the event of failure of the displacement pump. For this purpose, line 76 has one end which communicates with line 7d between the compressor SS and a shut-oil valve 7S. The other end ot line 7d communicates with the line 22 for the passage of compressed vapors from the compressor to the line 22 whereby the gas litt principle can be adapted for liquid removal. Line 7e is provided with a shut-off valve titl for blocking the passage of compressed vapors therethrough until such time as the gas lift is desired to be placed into operation.

By the arrangement described, an amount of vapor is retained in the system to supply the driving fluid for operation of the displacement pump and to supply the vapor space above the liquid with an amount of vapor suiiicient to replace the volume of liquid removed thereby to maintain slight positive pressure. It will be apparent also that by the use of the vapor of the liquid as a driving iiuid, the exhaust can be allowed to escape into the container thereby to minimize the necessity for seals or for an enclosed system for the driving huid. Similarly, additional amounts of driving iluid can be made available, if necessary, by adding heat to the liquid in the container for the generation of vapor. Thus a unique combination of forces are embodied in a safe system for the displacement of liquid and one that insures liquid delivery even though the principal liquid displacement means might become incapacitated.

In the modiiication illustrated in FIG. 5, the driving iluid is again the vapor of the liquid that is being pumped. The system in FIG. 5 is similar to that of FIG. 4 with the exception that means are embodied therein for the more efficient accumulation of vapors and liquids existing within the system.

In the system of FIG. 5, the exhaust vapors from the expansion turbine are returned directly through line il@ to an accumulator 81 which also functions as a separator. By Way of further modification, line '7h leading from the compressor 68 is provided with a by-pass 82 having a valve 84 for direct connection to the delivery line 22. The delivery line 22 is further fitted with a branch line 86 having a valve 88 through which the delivery line 22 communicates with the accumulator 81.

In this arrangement, when the expansion turbine and pump are inadvertently or otherwise inactivated, the valve 78 in the line 70 can be closed and

valves

84 and 88 opened whereby vapor at high pressure is transmitted from the compressor pump 68 through lines 70 and 82 to the delivery line 22 for making use of the gas lift principle in removing the liquid from the tank. During this operation, the material from line 22 is introduced into the accumulator separator 81 wherein the liquid product is separated from the vapor. The liquid is drained through line 90 into line 92 for delivery while the vapor is passed through line 94 either to the compressor or through line 96 back into the tank for filling the space previously occupied by the liquid. The accumulator is provided with a relief valve 98 for release of pressure in the event that excess pressure should be developed in the vapor system during operation.

In normal operation with the valve 7S open and the

valves

84 and 88 closed, the material in line 22 is passed through line llltl to a separator 102 wherein the liquid is separated from the vapor. The liquid product is drained through line 104 into line 106 for use while the vapor is removed through line 108 for return into line 94 which feeds either into the compressor or back into the tank or both, as previously described. In the modification illustrated in FIG. 5, the expansion turbine is shown as being formed of turbine buckets dimensioned to operate within a truncated cone which, when fed by the vapor at high presssure, seeks its own true center and thus performs as a gas bearing.

In a modification of this invention, illustrated in FIG. 6, use is made of a booster pump in the delivery line 22 outside of the tank. Such additional booster pump can be used to generate suflicient pressure for delivery 0f the liquid to storage and to divert part of the high pressure liquid back through line 2.2 and control valve 124 to the driving turbine on the submerged pump. This would relieve the submerged pump from the necessity to develop pressures sufficient not only to transfer the liquid to the top of the tank but also to the shore installation or storage. With the booster pump, the submerged pump would only be called upon to develop enough pressure to raise the liquid to the top of the tank where the more eicient booster pump would take over for delivery to storage. This enables use of a submerged turbine and pump of considerably lesser power requirement.

It will be apparent from the foregoing that I have provided various concepts which may be adapted for the eflicient and effective removal of cold liquids such as liqueed natural gas from a housing of large capacity. The system eliminates many of the problems heretofore encountered in means and methods for the displacement periodically of such cold materials. When the driving fluid is the same as the lluid from the liquid in the container, no special seals are needed since any leakage of vapors from the expansion turbine or the pump into the surrounding liquid or into the tank would not be deleterious. The liquefied natural gas is characterized by sutilcient lubricating properties for lubrication of the exposed moving parts of the expansion turbine and pump completely submerged within the liquid.

The described arrangement also embodies flexibility for conversion into a gas lift for the removal of liquid from the container in the event of breakdown or failure of the turbine-pump unit. The energy supplied to the driving fluid during compression provides heat suflicient to create vapors when transmitted to the liquid to make up the liquid withdrawn thereby to obviate the need to introduce other gases. The pumping capacity can be balanced with the required amount of vapor for replacing the liquid removed.

The turbine-pump combination completely submerged in the liquid and adjacent the bottom side thereof for more complete delivery obviates the need for the use of long shafts in deep well pumps of the type heretofore subject to failure due to distortion or freezing. Further, the arrangement of the pump in the bottom of the container permits discharge of the liquid to levels as low as a few inches, the remainder of which can be stripped out from the tank with a gas lift pump.

It will be understood that changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

l. A system for the removal of a low boiling liquefied gas at a temperature below F. from a closed container comprising a displacement pump housed within the liquefied gas in the container and having an inlet for the liquid and an outlet, a delivery passage in communication with the pump outlet and into which the liquefied gas is pumped, an expansion turbine housed within the liquefied gas in the container having an inlet and an outlet, an operative connection between the expansion turbine and the pump for operating the pump by the turbine, a driving fluid having a solidifieation temperature below the temperature of the liquefied gas, (a means outside of the container for pressurizing the driving fluid, a passage communicating the pressurized means with the turbine inlet for delivery of the pressurized driving fluid to the expansion turbine for operation thereof, and a passage communicating with the turbine outlet for returning the expanded fiuid to the pressurizing means, the driving fluid being present at a gas in at least one stage of the cycle, the liquefied gas being liquefied natural gas housed within the container at about atmospheric pressure, and the driving fluid being a liquid at a different stage of the cycle, there being a condenser at the outlet of the turbine whereby the exhaust gases are condensed before returning to the pump.

2. A system for the removal of liquefied gas at a ternperature below 25 F. from a container comprising a displacement pump housed within the liquid in the container having an inlet for the liquid and an outlet for the delivery of liquid, a delivery pipe in connection with the pump outlet and into which the liquid is pumped, an expansion turbine housed within the container and having an inlet and an outlet, an operative connection between the eX- pansion turbine and the pump for operating the pump by the turbine, a` driving fiuid having a solidification temperature below the temperature of the liquid, a means outside of the container for pressurizing the driving fluid, a means communicating the pressurizing means with the turbine inlet for the delivery of pressurized fluid to the expansion turbine for operation thereof, a means communicating with the turbine outlet for supplying the turbine fiuid to the pressurizing means, the driving fiuid being present as a liquid in one stage of the cycle and as a gas in other stages of the cycle, and having a condensation temperature above the temperature of the liquid in the container and a freezing point temperature below the temperature of said liquid, and a condenser between the outlet of the turbine and the pressurizing means whereby the exhaust gases are condensed before return to the pressurizing means, and an evaporator between the pressurizing means and the inlet to the turbine whereby the pressurized condensate is converted to a large volume of pressurized gas prior to introduction into the expansion turbine.

3. A system as claimed in claim 2 which includes a passage communicating the evaporator with the turbine inlet for the passage of pressurized gases therethrough 8 and in which the portion of the passage within the container is insulated to minimize transfer of cold from the liquid to the gas.

4. A system for the removal of a low boiling point liquefied gas from a container comprising a displacement pump housed within the container and having an inlet for the liquid and an outiet, a delivery passage in communication with the pump outlet and into which the liquefied gas is pumped, an expansion turbine house within the container having an inlet and an outlet, an operative connection between the expansion turbine and the pump for operating the pump by the turbine, a driving fluid having a solidication temperature beiow the temperature of the liquefied gas, a means outside of the container for pressurizing the driving fluid, a passage communicating the `ressurizing means with the turbine inlet for delivery of the pressurized driving fluid to thc expansion turbine for operation thereof, a passage communicating with the turbine outlet for returning the expanded fiuid to the pressurizing means, the driving fluid being a vapor which is substantially the same as the vapor of the liquid in the container, and means communicating the outlet from the turbine with the delivery passage whereby the exhausted vapors from the turbine lift the liquid through the delivery passage for gas lifting the liquid from the container for removal.

5. A system as claimed in claim 4 which includes a separator outside of the container, means communicating the delivery passage with the separator for delivery of the liquid and vapor from the delivery passage to the scparator wherein the material is separated into a liquid phase and a vapor phase, one outlet through which the separated liquid is removed from the separator, another outlet from which the separated vapor is removed from the separator, and means communicating the second outlet with the space in the container above the liquid level and with the pressurizing means.

6. A system as claimed in claim 5 which includes another separator in the delivery passage, means directing the flow in the delivery passage to said other separator when the liquid is displaced solely by the pump, and means for directing the flow through the delivery passage to the first separator when the liquid is displaced at least in part by the gas lift.

7. A system as claimed in claim 6 in which the second separator has one outlet through which the separated liquid is removed, another outlet through which the separated vapor is removed, and means communicating the vapor outlet with the space in the container above the liquid level and with the pressurizing means.

8. A system for the removal of cold liquid at a temperature below 32 F. from a closed container in which the liquid is to be maintained at about atmospheric pressure, comprising a displacement pump housed within the liquid in the container having an inlet for the liquid and an outlet for the delivery of liquid, a delivery pipe in communication with the pump outlet and into which the liquid is pumped, an expansion turbine housed within the liquid in the container and having an inlet and an outlet, an operative connection between the expansion turbine and the pump for operating the pump by the turbine, a driving iiuid having a solidiiication temperature below the temperature of the liquid, a means outside of the container for pressurizing the driving fuid, a means communicating the pressurizing means with the turbine inlet for the delivery of pressurized fiuid to the expansion turbine for operation thereof, a means communicating with the turbine outlet for supplying the turbine fluid to the pressurizing means, a storage facility separate and apart from the container to which the liquid from the container is transferred, a booster pump located outside of the container and having an inlet and an outlet, a delivery pump communicating with the inlet, means communicating the booster pump outlet with the storage facility, and means communicating the booster pump outlet with the means for delivery of fluid under pressure to the turbine, and valve control means within the last communicating means for controlling the ow of liquid therethrough.

References Cited in the le of this patent UNITED STATES PATENTS 244,603 Hill July 19, 1881 1,982,841 Taminci Dec. 4, 1984 2,061,013 Wade Nov. 17, 1936 2,149,600 Guinard Mar. 7, 1939 10

Claims

1. A SYSTEM FOR THE REMOVAL OF A LOW BOILING LIQUEFIED GAS AT A TEMPERATURE BELOW 25*F. FROM A CLOSED CONTAINER COMPRISING A DISPLACEMENT PUMP HOUSED WITHIN THE LIQUEFIED GAS IN THE CONTAINER AND HAVING AN INLET FOR THE LIQUID AND AN OUTLET, A DELIVERY PASSAGE IN COMMUNICATION WITH THE PUMP OUTLET AND INTO WHICH THE LIQUEFIED GAS IS PUMPED, AN EXPANSION TURBINE HOUSED WITHIN THE LIQUEFIED GAS IN THE CONTAINER HAVING AN INLET AND AN OUTLET, AN OPERATIVE CONNECTION BETWEEN THE EXPANSION TURBINE AND THE PUMP FOR OPERATING THE PUMP BY THE TURBINE, A DRIVING FLUID HAVING A SOLIDIFICATION TEMPERATURE BELOW THE TEMPERATURE OF THE LIQUEFIED GAS, (A MEANS OUTSIDE OF THE CONTAINER FOR PRESSURIZING THE DRIVING FLUID, A PASSAGE COMMUNICATING THE PRESSURIZED MEANS WITH THE TURBINE INLET FOR DELIVERY OF THE PESSURIZED DRIVING FLUID TO THE EXPANSION TURBINE FOR OPERATION THEREOF, AND A PASSAGE COMMUNICATING WITH THE TURBINE OUTLET FOR RETURNING THE EXPANDED FLUID TO THE PRESURIZING MEANS. THE DRIVING FLUID BEING PRESENT AT A GAS IN AT LEAST ONE STAGE OF THE CYCLE, THE LIQUEFIED GAS BEING LIQUEFIED NATURAL GAS HOUSED WITHIN THE CONTAINER AT ABOUT ATMOSPHERIC PRESSURE, AND THE DRIVING FLUID BEING A LIQUID AT A DIFFERENT STAGE OF THE CYCLE, THERE BEING A CONDENSER AT THE OUTLET OF THE TURBINE WHEREBY THE EXHAUST GASES ARE CONDENSED BEFORE RETURNING TO THE PUMP.