US2983409A - Means for the storage and transportation of a liquefied gas - Google Patents

Description

May 9, 1961 J. J. HENRY 2,983,409

MEANS FOR THE STORAGE AND TRANSPORTATION OF A LIQUEFIED GAS Filed July 2, 1958 FIG, 1

IN VEN TOR.

m 24 7 flziorneys 2,983,409 V MEANS FOR THE STORAGE AND TRANSPORTA- TION OF A LIQUEFIED GAS James J. Henry, New York, N.Y., assignor, by nlesne assignments, to Conch International Methane Limited, Nassau, Bahamas, a corporation of the Bahamas Filed July 2, 1958, Ser. No. 746,138

3 Claims. Cl. 222-399 This invention relates to the storage and/or transportation of liquefied natural gas and it relates more particularly to means employed in combination with a liquefied methane storage tank for controlling the flow of liquid into and out of the tank. I

As is well known, natural gas is available in excessive supply in some areas while a deficiency of natural gas or an equivalent fuel exists in many other areas. Where the twoareas are connected by land, transmission from the area of plentiful supply to an area where a deficiency exists can economically be effected by pipe line. Where the areas are connected by water, pipe line transmission is not so practical and other means must be devised for making such gas economically available to such areas where the deficiency exists.

Transportation in a gaseous state is impractical because of the small amount of gas that can be housed per unit volume of the container. Almost 600 times as much gas can be housed in an equivalent space at an equivalent pressure when the gas is reduced to a liquefied state. As a result, it becomes practical and economically feasible to liquefy the natural gas at the sourceof supply for transportation by ship in a liquefied state to the Patented May 9, 1961 operation of equipment. The extreme cold must be 1 kept out of contact with the steel walls of the ship since such walls lose their ductility at such low temperatures. For these and various other reasons, it is desirable to have means available which avoid the necessity of moving parts for removal of the liquid from the tanks in the event of failure or an emergency or a like situation where it is desirable to eflect removal'of the liquid from the tanks by means other than the conventional extemal 'pumps. It is an object of this invention to provide means in the storage and transportation of liquid which'has to be maintained at extremely'low temperature whereby the liquid can be. removed from the storage container without the necessity to make use of a power operated means or moving parts and it is a related object to provide emergency means forremoval of a cold boiling liquefied gas from storage tanks.

These and other objects and advantages of this in vention will hereinafter appear and for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawings in Figure 'l is a plan view of storage tanksmounted in the hold space of a ship and elements employed in com-' bination therewith in accordance with the practice of fill the ships tanks at the liquefaction'site and for conarea where a deficiency exists where the liquid is reformed to the gaseous state for use.

In commercial. practice, shipment will be made of the liquefied gas in large volume housed in suitable containers. Such containers of large capacity cannot economically be fabricated to withstand high pressures. As a result,the liquefied gas will be housed in the containers at about atmospheric pressure and at a temperatureat or-below its 'critical'temperature. For liquefied natural gas composed mostly of methane, the critical temperature level will be somewhat below 240 F. depending upon the amount of heavy hydrocarbons in the liquefied gas.

Thus use will be made of large tanks, such as tanks of 30 x 60 x 100 feet, formed of a metal such as aluminum, alloy of aluminum, copper, stainless steel or the like metal capable of retaining its ductility at the cold temperature of the liquid. The tanks will be mounted in the hold space of the ship substantially completely to fill the hold with the exception of a relatively thick lining of insulation material for minimizing heat transfer.

Oils, gasolines, and the like petroleum products and other liquids have been transported in tanks or tankers but such materials are usually housed in the storage containers at about ambient temperature. Thus, no particular problems are raised in the storage of a liquid or its flow into and out of the storage tanks. Where, however, the liquid to be transported comprises a liquefied gas having a critical vaporization temperature at its storage temperature of about 240 F., the problems arising are entirely diflFerent than those of the transportation of a liquid at ambient temperature.

The extreme cold of the liquid and vapor raises certain problems such as condensation and solidification of moisture from the atmosphere which may interfere with the nection with the shoretanks for" discharging the liquid ingtherefrom for communicating the main header with spray heads located within the tanks for wetting down the walls and cooling down the tanks before flowing the liquid at'a more rapid-fate through thelines 18 for'filling' the. tanks. Each of the branch lines is provided with a gate valve 22 and 24 for controlling the flow of liquid. The liquid is discharged from each of the tanks through a downpipe having its inlet at the bottom of the tank. The opposite end of the pipe communicates the inlet with a pump 26 located outside of the tank and the pumps outlet communicates with a branch pipe 28 leading into the header 16. A check valve 30 and a gate valve 32 are provided in each of the branch pipes. The foregoing comprises the normal means for filling and discharging the tanks with the liquefied natural gas.

Operative in combination therewith is a supplemental means for eflfecting the discharge of the liquid from the tanks into the header. Such means comprises a sealed housing 34 in the bottom of each tank. Each housing is provided with an inlet 36 in a side wall adjacent the bottom of the tank having a swing check valve 38 in the line 40 which has an open end in the liquid space near the bottom of the tank 12 and communicates with the inlet 36. The check valve closes in response to pressure within the housing and opens automatically in response to release of pressure within the housing.

Extending into the housing is a tubing 42 having its inlet 44 at the bottom of the housing and which extends outwardly from the housing through the top of the tank 12 to the main header 16. A gate valve 46 and a check 3. valve 48 are provided in the part of the line 50 between the tank and the header.

The housing is also provided with an inlet opening 52. The inlet opening communicates with a compressed gas header 54 throughaa tube 56 which has athree-Way valve 58 in a portion outside of the tank and a gate valve 60 and 62 on each side of the three-way valve. In one'position, the valve communicates the inlet 52 with the compressed gas header 54 while in the other position, the valve communicates the inlet 52 with a vapor header 64.

The compressed gas in the compressed gas header can be an inert gas such as nitrogen or carbon dioxide but it is preferred to make use of vapors released from the housing or from the tank for recompression thereby to provide a complete cycle which avoids the introduction of foreign material into the system. ,The vapor removed can be recompressed to some higher pressure such as 50 p.s.i. for use in the discharge cycle.

In operation, the valve 58 can be operated to communicate the compressed gas header 54 with the inlet 52 whereby vapors at a pressure of about 50 p.s.i. enter the housing 34 to force the liquid therein through the tubing 42 to the liquid header 16 with the gate valve 46 in open position and the check valve 48 opened in response to such pressure on the liquid. When the housing 34 has been substantially completely emptied of liquid, the threeway valve 58 can be operated to communicate the inlet 52 with the vapor header whereby the housing 34 will be relieved of pressure. Under such circumstances, the head of liquid in the tank will be effective to cause the swing valve 38 to open to enable liquid to flow through the line 40 into the housing 34 to fill the housing. The vapor within the housing that is displaced by the liquid can flow through the inlet 52 into the line 56 for passage to the vapor header for recompression or disposal. When the housing 34 has becomefilled with liquid, the valve 58 can again be operated to recommunicate the compressed gas header with the inlet 52 to repeat the cycle.

Thus, the liquid can be removed from the tank substantially completely to empty the tank without relying upon plumbing means to effect displacement. The system described provides for complete control with respect to the flow of materials and it embodies, a complete cycle wherein the vapors removed can be reintroduced in a compressed state to effect the desired displacement without introduction of foreign materials.

It will be apparent that the described system for the removal of liquid will be relatively slow by comparison with the conventional means such that the removal system will be employed chiefly in the event of failure of the conventional means or in the event that such conventional means present certain dangerous situations.

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: I

1. In the storage and transportation of a liquefied gas in tanks having an inlet through which the liquid is introduced and an outlet through which the liquid is discharged from the tank including a tubing extending downwardly to the bottom portion of the tanks and a power operated means for displacement of the liquid through the tubing to the outlet, a liquid header for receiving the discharged liquid and means communicating the outlet with the header, a sealed compartment within the tank and in the bottom thereof, a source of supply of pressurized gas, a vapor header, a first opening in the compartment and means communicating said first opening with said source of pressurized gas and the vapor header, a second opening in the compartment and means communicating the second opening with a pressure responsive valve which closes in response to pressure in the compartment and opens in response to the loss of pressure within the compartment, a tubing having one end extending to the bottom portion of the compartment and communicating with the liquid header, a valve means in the first communicating means shiftable in one position to communicate the first opening with said source of pressurized gas whereby the pressure responsive valve closes and liquid is forced from the compressed gas.

References Cited in the file of this patent UNITED STATES PATENTS 1,460,389 Mauclere July 3, 1923 1,533,309 Durborow Apr. 14, 1925 1,823,406 Peaden Sept. 15, 1931 1,897,164 Endacott Feb. 14, 1933

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