US3107494A - Catch and burn tank assembly - Google Patents

Description

Oct. 22,1963 'r. H. KING 3,107,494

CATCH AND BURN TANK ASSEMBLY Filed April '7, 1960 2 Sheets-Sheet l FIG.I

Oct. 22, T H KlNG CATCH AND BURN TANK ASSEMBLY Filed April 7, 1960 2 Sheets-Sheet 2 United States Patent 3,107,494 CATCH AND BURN TANK ASSEMBLY Thomas H. King, Midland, Tex., assignor to Socony Mobil Oil Company, Inc, a corporation of New York Filed Apr. 7, 1960, Ser. No. 20,602 Uaims. (Cl. 61-.5)

The present invention relates to improved apparatus for use in the operation of underground storage wells and more particularly to apparatus for the controlled destruction of volatile product inadvertently discharged from the storage Wells, and has for an object the confinement of accidently discharged volatile product to a limited area and the controlled destruction thereof in that area during the course of the discharge.

In the operation of petroleum product storage wells formed in salt beds or in salt domes the petroleum products, usually volatile liquified petroleum gas, hereinafter referred to as LPG, are added and removed to and from the wells by a displacement method. More particularly in the storage of LPG over brine, the LPG is added to a Well at relatively high pressure to displace the brine. On the other hand the brine is returned to the well to remove the LPG.

Care must be exercised during the addition of the LPG product to avoid overfilling the storage Well. In such event the LPG will overflow into a surface storage pit and begin to volatize. In this state it easily is ignited to cause damage to the storage facilities and to the surrounding area. Accordingly, it has been the practice to try to avoid filling the cavity to capacity with the attendant loss of storage capacity. However, due to human error and the occasional pipe ruptures, particularly failure of the brine pipe within the well, product does escape into the surface pit.

In accordance with the present invention there is provided a means in the brine pipe line between the well and the surface storage pit for catching all the product accidentally discharged from the well and for confining the escaping volatile product to a limited area where it is safely destroyed by burning. The burning of the escaped product indicates the condition to the operator of the storage facility and provision is made to give him adequate time to shut in the well before greater damage is done. More particularly there is provided in a brine storage pit for a subsurface storage well, a catch and burn tank, comprising a container having a closed bottom end and an open top end for receiving the discharge from the well. The container is provided with at least one discharge port formed in wall structure thereof intermediate its ends. Conduit means interconnects the discharge port with the interior of the container at a point near the bottom thereof for maintaining in the container a substantially constant level of liquid independent of a lower level of liquid or brine in the pit. An igniting means is provided adjacent the open end of the container for burning of LPG product discharged into the container.

The structure of the catch and burn tank is such that the flow of brine from the container to the pit follows a path from the top of the container toward the bottom thereof, thence by way of the interconnecting conduit to the discharge port. Since the LPG product is lighter than brine, the flow from the discharge port is limited to brine. Thus the LPG product discharged with brine into the container is held within the confines of the container for controlled destruction.

For other objects and attendant advantages of the present invention reference may be had to the following detailed description taken in conjunction with the accompanying drawings where:

FIG. 1 schematically illustrates a salt dome storage facility embodying the present invention;

FIG. 2 is a top view of the catch and burn tank of the present invention; and

FIG. 3 is a cross-sectional view of the catch and burn tank taken along a line substantially corresponding with line 33 of FIG. 2.

Referring now to the drawings and particularly to FIG. 1, there is illustrated a salt dome storage facility employing the present invention. The facility 10 comprises a storage well 11 formed in a salt bed or dome 12 by means well known in the art. In this form of storage facility, a LPG product such as butane or pentane 13 is stored over brine 18. The LPG is added to or removed from the storage well 11 by means of displacement techniques. The displacement medium usually employed is the brine 18, which during operation of the well is transferred between the well and a surface storage pit 19 by way of pipe 20. In accordance with the present invention, the return flow of the brine 18 from the well 11 to the pit 19 is by way of a catch and burn tank assembly 30, which provides a safety function for the storage system.

Operators of such storage facilities have in the past experienced the inadvertent discharge of LPG product 13 from the well 11 into the brine storage pit 19. The discharge has occured in any number of ways but in each instance it has created a condition hazardous to both equipment and personnel in the area. For example, many operators in attempting to employ the full capacity of the storage well 11 have added LPG product until the interface 23 between the brine 18 and the product 13 has passed the lower end 2011 of the pipe 20. The product then moves up the pipe 20 and is discharged directly into the brine pit 19. An even more dangerous condition results when for one reason or another the pipe 2il= becomes ruptured at some point intermediate its length and within the well, whereupon the LPG product 13 will, due to pressure release, flow at a great rate into the brine pit 19.

The catch and burn tank system 30 provides a solution to the problem of accidental discharge either by personnel error or equipment failure. The function of the catch and burn tank system is to contain the discharged LPG product Within a limited area for its controlled destruction. In carrying out this function, the catch and burn tank system 30- is comprised of a container 31 having a closed end 32, resting at the bottom of the storage pit 19 and open end 33. The container 31 has provided in wall structure thereof at least one discharge port 34 interconnected by way of a con duit structure 35 to an inlet port 36 located near the bottom of the container 31.

The flow path between the discharge port 34 and the inlet port 36 is a closed one. The flow of liquid out of tank or container 31 into pit 19 must follow a path including inlet port 36, structure 35 and port 34. It is thus evident that such an arrangement will cause to be maintained a susbtantially constant level 37 of brine in the container 31; a level determined by the location or height of the discharge port 34.

The fiow of brine from the well :11 to pit 19 may be traced by way of a path including pipe 20, valve 21 and pipe 22 into the catch and burn tank system 30. The brine then effectively travels by way of the inlet port 36, the conduit 35 and the discharge port 34 into the pit 19. Because the density of the LPG product is less than that of the brine, it is impossible for the LPG product to flow out of the container 31 and into the pit 19 by way of the discharge port 34. Any LPG flowing into the container 31 remains on the surface of the brine where it accumulates, tending to fill the container and to flow over the upper edge of the container 31, a condition never attained for the following reasons.

The capacity of the container 31 above the liquid level 37 is designed to accumulate a predetermined volume of LPG discharged from the well. One factor to be considered is the maximum flow rate of LPG that would occur should the pipe 20 rupture within the well -11. Another factor is the rate at which the LPG will be burned. Assuming the flow rate to be a thousand gallons an hour, the container 31 can be designed to hold at least five-hundred gallons and preferably one thousand gallons of LPG product. Thus it would take at least from one-half hour to one hour before the LPG would begin to over flow. The time for filling the tank 31 to overflow is increased by means, including burner 40, provided to ignite the LPG product accumulated within the container 31, and there to destroy it by burning. The burning of the LPG will also serve as a signal to the operator of the accidental discharge of product, and he will have sufiicient time to shut in the well as by closing valves 16 and 21.

The burner or igniter 40 is located adjacent the top of the container 31, and preferably is effective at all times. One form of igniter may be provided by the continuous burning of a fuel conveniently stored in tank 4 1, and connected to the igniter 40 by pipe 4-2. While only one igniter or burner 40 has been illustrated, it will be understood that additional bumers may be employed and arranged around the periphery of the tank 31. In one embodiment now in use, four burners are arranged in spaced relationship about the upper edge of the tank.

The invention will be better understood from the following description of the operation of the system 10. A LPG product from some source, for example a processing facility such as a refinery (not shown), is added to well 11 by way of pipe line 14, pump 11S, valve 16, and casing 17. With the addition of the product to the well 11, the brine 1S begins to flow out of the well through pipe 29, valve 21 and pipe 22 into the tank 31. The flow of the brine from tank 31 into the pit 19 is by way of inlet port 36, conduit structure 35 and discharge ports 34.

In the event of an accident or human error, LPG product begins to flow into the container 31 and will begin to vaporize and immediately will be ignited by the continuously burning igniter 40. As discussed above, the accidental discharge of LPG into tank 31 may occur when interface 23 moves below the bottom 20:: of pipe 20, or when the pipe 20 ruptures in the well above interface 23.

Due to the construction of the catch and burn system 30, the LPG product is confined therein and the burning of the LPG will provide a visual signal to the operator who will take steps necesssary to shut in the well i l.

The system is also provided with the usual pump 43 employed for displacing with brine the LPG and initiate its removing LPG from the storage facility transfer for utilization. More particularly, the pump 43 draws brine from the pit 19 by way of pipe 44, and forces it through valve 21 and pipe 20 into the bottom of the well :11. The LPG is thus displaced from well 1 1 by way of casing 17 and pipe line 14.

Referring now to FIG. 3, there is illustrated in cross section a preferred embodiment of the catch and burn tank asembly 30. The tank asembly 39 is comprised of the outer tank 31, preferably formed of steel. The closed end 32 of the tank 31 rests upon a concrete foundation 50 on the bottom of the storage pit 19. The upper end 33 of the tank 31 is open to the atmosphere. A plurality of outlet ports 34 are spaced about the outside of the tank 31, and are located a predetermined height above the bottom 32 of the tank. The outlet ports 34 are connected by way of conduits 35a to a cylinder or manifold 35b concentrically mounted within the tank 3 1 and resting on the bottom thereof. The upper end of the manifold is sealed, and the bottom, or opposite end, is

4 provided with a plurality of inlet ports 36 spaced about the lower end to provide for the flow of brine from the tank 31 into the manifold or cylinder 35]).

The radially extending conduits 35a terminate in their outer ends at elbows 45 which may be regulated to any attitude or variw in length to determine the level 37 of brine maintained within the tank 31. The elbows 45 provide a means for maintaining the level of liquid or brine above the upper end of the manifold 35b and above the conduits 35a, thus to provide an insulation of brine between burning LPG and these elements.

The return line 22 from the well 11 terminates at the outside of the tank 3:1 and near the upper end thereof in the manifold 22a, best illustrated in FIG. 2. The manifold 22:: extends around the outside of the tank and is provided at spaced intervals with brine discharge ports 22b located within the tank 31. Any number of ports 22b may be employed. And while the manifold is shown to extend only part way around the tank 3 1, it may extend completely around the tank.

A catwalk 52 extends completely around the tank 31 to provide access for visual inspection of the tank assembly 30 and to ignite the burners 40, FIG. 1. Access to the catwalk 52 is gained by way of a bridge structure 53 extending to the shore.

The catch and burn tank assembly 30 is provided with a number of manholes and ports for maintenance purposes. Thus, when it is determined from a visual inspection some maintenance is required of the interior of the tank 36, the storage pit 19 may be drained and at the same time valve 54 opened also to drain the interior of the tank 31. Entry to tank 31 may now be had by way of manhole 55. Similarly, access may be had to the interior of the manifold 35b by way of manhole 56.

Now that the invention has been described, modifications will become apparent to those skilled in the art and it is intended to cover such modifications as fall within the scope of the appended claims.

What is claimed is:

1. In a system for the storage of hydrocarbons over brine in a plurality of underground salt cavities, wherein the hydrocarbons are pumped therein at relatively high pressure to displace brine to an open pit for storage therein by way of a discharge line and subsequently are removed therefrom by returning brine to the cavities by way of an intake line having an open end in the pit, the corn bination which comprises a tank having an open end and a closed end located in said pit, a fiow channel for connection with the discharge line to discharge liquids from the cavities into the open end of said tank, at least one discharge port formed in wall structure in said tank intermediate said ends for discharging brine from said tank into said pit, and conduit means interconnecting the discharge port with the interior of the tank at a point near the bottom thereof to provide a flow path from said point to said port.

2. In a system for the storage of hydrocarbons over brine in a plurality of underground salt cavities, wherein the hydrocarbons are pumped therein at relatively high pressure to displace brine to an open pit for storage therein and subsequently are removed therefrom by returning brine to the cavities, the combination which comprises a tank having a closed end and an open end located in said pit, means for introducing liquids including brine into said tank at a point adjacent said open end, means for discharging brine from said tank into the pit while maintaining the level of liquid within said tank at a predetermined level independent of lower levels of liquid outside of said tank and within the pit, said discharging means comprising at least one inlet port located within said tank and near the bottom thereof, at least one outlet port located outside said tank and open to the atmosphere, and conduit means providing a closed path interconnecting said inlet port and said outlet port.

3. The combination of claim 2 wherein said discharging means comprises a plurality of outlet ports spaced about the outside of said tank, a manifold positioned Within said tank and provided near a bottom portion thereof with a plurality of inlet ports, conduits interconnecting the interior of said manifold with said outlet ports.

4. The combination of claim 3 wherein said outlet ponts comprise means for maintaining the level of brine within said tank above said conduits and said manifold.

5. In an open brine storage reservoir for receiving liquid including brine displaced from underground hydrocarbon storage facilities when hydrocarbons are added to said storage facilities and for receiving and confining hydrocarbons accidentally discharged with the liquid from said underground facilities, the combination which comprises a tank having an open end and a closed end located in said reservoir, at least one inlet port located within said tank and near the bottom thereof, at least one outlet port formed in Wall structure of said tank intermediate said ends and at a point above the level of said inlet port, conduit means interconneotingsaid ports for discharging only the brine into the reservoir and for maintaining the level of the liquid within said tank at a predetermined level independent of the level of the liqold in the brine storage reservoir, and at least one burner associated with said tank for disposing of the hydrocarbons confined therein.

6. The combination of claim 5 wherein said burner is positioned above the surface of the liquid for burning the hydrocarbons which accumulate on the surface of the brine and wherein a means outside of said tank interconnected with said conduit means is provided for maintaining the top surface of the liquid within said tank at a predetermined level above the level of said conduit means to provide an insulation of brine between the burning hydrocarbons and said conduit means.

7. A catch and burn tank assembly for use in a system for the storage of hydrocarbons over brine in a plurality of underground salt cavities, wherein the hydrocarbons are pumped therein at relatively high pressure to displace brine to an open pit for storage therein by way of a discharge line and subsequently are removed therefrom by returning brine to the cavities by way of an intake line having an open end in the pit comprising a tank having an open end and a closed end for use in said open pit, a flow channel for connection with the discharge line to discharge liquids from the cavities into the open end of said tank, means for discharging brine from the bottom of said tank into the pit While maintaining the level of liquid within said tank at a predetermined level independent of lower levels of liquid outside said tank and with in the pit, said discharging means comprising a manifold positioned within the tank at the bottom thereof and eX- tending upward to a point intermediate the ends of the tank, a plurality of inlets located at the bottom of said manifold, a plurality of discharge ports formed in wall structure in said tank intermediate said ends, a plurality of conduit means interconnecting the interior of said manifold near the top thereof with said outlet ports, and a plurality of elbows outside of said tank each having one end interconnected with one of said discharge ports and another end open to the atmosphere at a point above the level of said conduit means and said manifold with in said tank.

8. The catch and burn tank assembly of claim 7 wherein said flow channel extends around the outside of the tank near the top thereof and is provided with a plurality of discharge channels at spaced intervals leading into said tank for discharging liquid from the cavities into the open end of said tank.

9. A liquid receiving means for use in an open brine storage reservoir for receiving liquid including brine displaced from underground hydrocarbon storage facilities when hydrocarbons are added to said storage facilities and for receiving and confining hydrocarbons accidentally discharged with the liquid from said underground storage facilities, comprising a tank having an open top end and a closed bottom end, at least one outlet port formed in the Wall of said tank intermediate the ends thereof, only one conduit means at the lower end of said tank leading from a point near said tank bottom to a level intermediate the ends of said tank for forming a separate flow path from the bottom of said tank to said level, said conduit means having at least one opening near said tank bottom below said port, discharge conduit means interconnected with said port and with said conduit means at said intermediate level to provide a closed flow path from said opening to said port for discharging only the brine into said reservoir and for maintaining the level of the liquid within said tank at a predetermined level independent of the level of the liquid in the brine storage reservoir, and a burner positioned above the surface of the liquid for burning the hydrocarbons which accumulate on the surface of the brine.

10. A liquid receiving means for use in an open brine storage reservoir for receiving liquid including brine displaced from underground hydrocarbon storage facilities when hydrocarbons are added to said storage facilities and for receiving and confining hydrocarbons accidentally discharged with the liquid from said underground facilities, comprising a tank having an open end and a closed end, at least one inlet port located Within said tank and near the bottom thereof, at least one outlet port located outside said tank, conduit means providing a closed path interconnecting said inlet port and said outlet port, and a disposal means comprising at least one burner positioned above the surface of the liquid for burning the hydrocarbons which accumulate on the surface of the brine, said outlet port comprising means outside of said tank for maintaining the top surface of the liquid within said tank at a predetermined level above the level of said conduit means to provide insulation of brine between the burning hydrocarbons and said conduit means.

References Cited in the file of this patent UNITED STATES PATENTS 301,191 Westinghouse July 1, 1884 2,922,281 Brooks Iran. 26, 1960 2,942,424 Koble June 28, 1960 FOREIGN PATENTS 242,781 Germany Ian. 19, 1912 181,575 Austria Apr. 12, 1955

Claims (1)

1. IN A SYSTEM FOR THE STORAGE OF HYDROCARBONS OVER BRINE IN A PLURALITY OF UNDERGROUND SALT CAVITIES, WHEREIN THE HYDROCARBONS ARE PUMPED THEREIN AT RELATIVELY HIGH PRESSURE TO DISPLACE BRINE TO AN OPEN PIT FOR STORAGE THEREIN BY WAY OF A DISCHARGE LINE AND SUBSEQUENTLY ARE REMOVED THEREFROM BY RETURNING BRINE TO THE CAVITIES BY WAY OF AN INTAKE LINE HAVING AN OPEN END IN THE PIT, THE COMBINATION WHICH COMPRISES A TANK HAVING AN OPEN END AND A CLOSED END LOCATED IN SAID PIT, A FLOW CHANNEL FOR CONNEC-

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