US3011321A - Apparatus for the maintenance of liquefied petroleum products - Google Patents

Description

Dec. 5, 1961 F. A. CLAUSON 3,011,321

APPARATUS FOR THE MAINTENANCE OF LIQUEFIED PETROLEUM PRODUCTS Filed Dec. 2, 1957 2 Sheets-Sheet 1 Dec. 5, 1961 F. A. CLAUSON 3,011,321

APPARATUS FOR THE MAINTENANCE OF LIQUEF'IED PETROLEUM PRODUCTS Filed Dec. 2, 1957 2 Sheets-Sheet 2 United States Patent Ofifice 3,011,321 Patented Dec. 5, 196 1 This invention relates generally to the maintenance of low temperature liquefied gases and in one of its more specific aspects is concerned wit-h an apparatus for the storage and transportation of liquefied petroleum gases.

Among the problems encounteredin petroleum production is that of the presence of large quantities of petroleum gases, which include the butanes, propane, ethane and methane. Not only are these gases suitable for use in petro-chemical production and for fuel purposes, but also they are a valuable source, with but slight processing, for the enrichment of manufactured gases to be used for heating purposes. In domestic oil field production, utilization is accomplished at nearby facilities, while the transportation of petroleum gases from the fields to relatively distant points is largely by transcontinental pipelines.

'Ihe shipment of liquefied petroleum gases for considerable distances is feasible in containers which are built to withstand elevated pressures. However, the cost of manu facture of such containers, due to the amount of material required, and the expense of transportation of the heavy containers, restrict the quantity and shipment to nearby localities. At the same time, because of the maximum allowable metal wall thickness permitted without stress accompanying drawings wherein:

relief, the size of these containers is limited. The larger Y container would require a wall thickness that wouldneed stress relieving, so that its dimensions would be determined by the size of the annealing furnaces available.

Other means for transporting liquefied petroleum gases at extremely low temperatures and at substantially atmospheric pressure, which have been suggested but not proven successful in commercial operation, include the use of insulated tanks mounted on barges or in vessels, the tanks being considerably larger than the pressurized containers and employing balsa wood for the heat insulation. Because of the amount of such insulation required, the usable dimensions and so the sizes of the tanks are reduced considerably. Furthermore, the refrigeration energy requirement to reach and :maintain the low tem- I peratures is very great. In addition, there is the danger of low temperature embrittlement of carbon steel tank walls which might occur should the insulation drop off and expose tank wall surface to the liquefied petroleum gas. In the absence of the use of high cost alloy steels for constructing the tanks, the shipment of liquefied petroleum gases is restricted by safety standards to the relatively heavier petroleum gases which have the higher boiling points, such as the butanes and propane.

Among the richest sources in the world of petroleum and petroleum gases are the Middle East oil fields of the Persian Gulf area. In this region, the amount of petroleum gas available is fabulous and since it cannot be exploited fully, either by further processing or by shipment through pipelines to areas where such can be accomplished,.because of long distances or political unrest, it is allowed to be exhausted to the atmosphere or burned.

Over 70 percent of the petroleum and petroleum products exported from the Middle East oil fields are shipped to the energy deficient areas of Western Europe. Should petroleum gas become available economically, the energy deficiency can be reduced. Among the problems encountered in shipping liquefied petroleum gases is that of the transportation and storage of these gases at their atmospheric pressure boiling points. While it is known to transport and store liquefied gases, such as nitrogen and oxygen,

in Dewar type'containers consisting of spaced inner and outer receptacles, the problems involved in the construction of such type containers for the shipment of the large amounts of liquefied petroleum gas required to justify their economical transportation prevents the use of the same.

Accordingly, it is an object of the present invention to provide a novel'rneans for maintaining low temperature liquefied gases.

It is another object of the invention to provide .a new and improved apparatus by which liquefied petroleum gases may be shipped economically over long distances.

Still another object of the invention is to provide an economical apparatus for the maintenance of low temperature liquefied gases in which the dangers of construction failure and of accumulation of explosive gas mixtures are virtually eliminated.

And another object of the invention is to provide a novel apparatus for the shipment of liquefied gaseous hydroearbons in which the cost is negligible as compared with other means. I

Another object of the invention is to provide an apparatus for the shipment and for the storageof low temperature liquefied gases which are segregated for selective use as desired.

IAndstill another object oft-he invention is to provide means for the shipment and/or storageof liquefied gases with minimum refrigeration requirements.

I These and other objects, advantages and features of the present invention will become apparent from the following description of the invention and by reference to the FIG. 1 is a partial diagrammatic, plan view pet a means for the shipment of low temperatureliquefied gases;

FIG. 2 is a general showing of an elevation cross section taken through a cargo compartment of the means of FIG. 1, disclosing .a specific embodiment;

FIG. 2a is a partial elevation cross'section through a liquefied gas container; 2

FIG. 2b is an enlarged partial cross sectionalviewof means for the support of a liquefied gas container;

FIG. 3 is a partial elevation cross section of another means for the shipment and for storage of liquefied gases; and

FIG. 4 is a diagrammatic showing of a meansfor unloading a liquefied gas container.

In accordance with the illustrated embodiments of my invention, low pressure tanksfor low temperature products are installed in the center tanks, also containing low temperature products, of a standard tanker, with thecenter tanks surrounded by a petroleum pro-duct. This construction has been found to be most applicable in shipment Where the gases available for the low temperature tanks are approximately equal in volume. r f

Referring to FIG. 1 of the drawing, there'isdisclosed in diagrammatic form, a partial plan view of an ocean going tanker indicated as T, showing separate compartments or wing cargo tanks, one of which is indicated at K, formed by the longitudinal and transverse bulkheads L and V respectively and .the outer shell E of the tanker. Each of the center cargo tanks R, shown as cubical, contains a tank or container C for a low temperature liquetied gas, e.g., a petroleum gas such as propane, and is immersed in and surrounded by the cargo of another low temperature liquefiedgas, e.g., a petroleum gas which'has a higher boiling temperature, e.g., butane, than that carcargo compartment showing analternate form for the ried in the center cargo tanks C. These containers may 3 formed of a pair of metallic angle members N and separated by a block of wood or similar insulating material I. The outlet for the spherical tank or container C is indicated generally at A, FIG. 2, While a similar outlet for the center cargo tank or compartment is not shown, the cargo O in the wing tanks K and double bottom compartment U being discharged in the conventional manner through conduits (not shown) leading to and from the pump room. Alternately, unloading the containers C and center cargo compartments K may be accomplished through the conventional tanker unloading system.

In the practice of the invention, each center liquefied gas tank or container C is cooled at initial loading or after cleaning of the cargo'tanks by flash vaporization of liquefied gas,-compressing, condensing and recyling the evaporated gas in order to conserve the same, with the evaporation process reducing the interior temperature of the containers C.

The liquid loading line is shown at 10, FIG. 2 and the vapor line, leading to the refrigerant compressor (or to the power plant for use as fuel) is shown at 11. A pressure relief valve for the spherical container C is shown at 12, leading into the cubical center tank R and is shown immersed in the liquefied gas carried therein, for tank design purposes.

The center tanks R and the wing tanks K are enclosed by the deck indicated at D. The relief valve for the cubical center tank is shown at 13 leading to the vent, although it may be connected to a fuel line. A vacuum relief valve for each spherical container C is indicated at 14 and for use with extremely low pressure spherical tanks, a second or bottom vacuum relief valve is indicated at 15.

The structure as disclosed heretofore is of particular advantage forthe transportation of petroleum gases from the Persian Gulf region. In order to overcome the poor space utilization of a sphere, in which propane, indicated as C is to be shipped, the sphere in the cubical center tank will be surrounded by butane, indicated at C or other petroleum products. The gas production from this Middle East region is such that the recovery of propane and butane is approximately equal in volume, which corresponds to the volume distribution of a sphere and the remainder of the enclosing cube. The butane surrounding the sphere would be carried in a refrigerated liquid condition under existing cargo regulations which permit the use of IO# relief valves with essentially no change in the s'hips hull structure.

The propane or spherical container or tank C would be designed to assure a minimum temperature of 30 F. in the surrounding butane, the minimum allowable in contact with the ships hull structure. To obtain this minimum temperature in the surrounding butane, the operating temperature at the top of the propane container would be 20 F. to result in a 30 F. boiling point at its bottom, because of increased static head. Such temperatures would require designing the spherical container for an operating pressure of 55# absolute. This is a relatively low pressure for a spherical design since tanks can be built .to meet the 60' diameter size requirement of the largest tankers without exceeding the maximum allowable steel thickness of 1%". With a suitable insulation for the propane tank, lower design pressures are possible.

With the propane tank surrounded by the butane tank, the propane relief valve may be vented into the butane tank, thereby reducing the working pressure on the spherical tank. By. venting below the liquid level in the butane tank, further reduction in design pressures are possible.

The vacuum relief valve 14 is provided to insure that pressure in the cubical (butane) tank is never higher than in the spherical (propane) container. With such a safety device it is necessary only to provide for protection against the static head of butane in the event the propane tank were empty and under no pressure. If low pressure designs are used, it is necessary to install the second or bottom vacuum relief valve 15 to prevent tank collapse from external pressure. This bottom relief valve can be placed in series with a rupture disc to prevent contamination due to leakage.

By raising the boiling point in the spherical (propane) tank and introducing an additional barrier to heat transfer, by surrounding the cubical center tanks by the wing cargo tanks for petroleum products such as fuel oil, the insulation problem has been reduced greatly and insulation is not a necessity for safety but merely a means for reducing refrigeration energy requirements through reduced heat pickup. The wax film formed in the wing tanks furnishes considerable insulation as disclosed in my copending application for Patent Serial No. 614,838, filed October 9, 1956, now issued as Patent No. 2,929,- 221, dated March 22, 1960. And if necessary, an insulationlayer of the type disclosed in my copending application, Serial No. 695,904, filed November 12, 1957, now issued as Patent No. 2,952,987, dated September 20, 1960, can be used on the interior of the center tank and/or the exterior of the spherical container.

The modified liquefied gas container disclosed in FIG. 2a is substantially the same as that disclosed in FIG. 2, with identical elements having identical numeration in each'figure. The inner liquefied gas container, now indicated as C; has a compound ellipsoidal form, in the shape of the commonly known Hortonspheroid, the volume of which is substantially that of the enclosed'sphere of FIG. 2, so that the volume relationship between the gas container and the surrounding tank is still maintained. The

spheroidal construction is used where economy in steel requires it, the load supporting structures at S reducing the overall steel plate thickness requirements. The spheroid is insulated from the double bottom compartment by the structure indicated at I, e.g., a wooden platform. When this platform is bolted down, together with the supporting structure at S, the need for the spacer elements S disappears although these elements can be used in addition, as indicated in this figure. p,

The procedure thus far described can be extended to other liquefied petroleum gases having lower boiling points, e.g., ethane and methane, although this would necessitate the use of low nickel alloy steel or other low temperature alloys. Such a modification is disclosed in FIG. 3, where the enumeration is the same as that for identical structural features disclosed in FIG. 2, with the inclusion of an additional spherical container G within the outer spherical container C. The inner container holds a lower boiling point product such as ethane indicated as C For purposes of clarity, the support means for the additional container G as well as the valving and related piping are omitted, since they would be similar to that shown in FIG. 2, the internal spherical containers being relieved successively into the immediately outer container or tank.

FIG. 4 discloses a structure for unloading the low pump propane ashore from the refrigeration plant accumulator drum. In the set up as shown, closed valves are indicated at V and open valves are indicated at V The loading and vapor vent lines are shown at 10 and 11 respectively, as in FIG. 2. A pressure by-pass is shown at 16, the refrigeration compressor is at 17, the condenser at 18 and the indicating pressure controller at 19. Since the pressure in the spherical tank C holding the propane C is held at a higher pressure than the liquefied gas in the accumulator drum 20, because the pressure in the drum is reduced by the refrigeration compressor 17, the liquefied gas flows into the accumulator drum and is discharged by pump 21 and unloading line 22. The vapor pressure in the spherical container is maintained by means of the pressure by-pass leading off downstream'of the compressor;

, Thus, there has been disclosed an apparatus by which the cost of maintenance of low temperature liquefied products is negligible'as compared'with other such insulation. In almost all the remote petroleum producing areas where petroleum gases-could be liquefiedat low price, there would alsobeavailable crude oil or processed petroleum products for transportation to the consumer markets sothat the disclosed apparatus would be economically attractive,

The improved structure has a minimum steel requirement for carbon steel and does not require high cost.

nickel or other low temperature alloy steels except when "used with the lower boiling point gases. The spherical container holding propane is normally fioating in butane (of slightly higher density than propane) so that support stresses are practically eliminated during normal operation, and in general, the support problems are simplified greatly because of the symmetry of spherical design and smaller stresses as a result of lower temperature differentials.

In addition, the system is safe in the event of insulation failure, the insulation requirement being for reduction of refrigeration load, the minimum surface area and temperature differences for heat transfer even reducing these requirements. The propane in the center tank provides the refrigeration for the butane so that only a single propane refrigeration system is required, thus eliminating multi-component refrigeration. And the nested positioning of the liquefied gases eliminates coffer dam spaces containing water vapor, which, upon condensation, may lead to excessive corrosion.

In the event of a structural failure in either of the liquefied petroleum gas containers, the liquefied petroleum gas will be vaporized by the surrounding liquefied gas or the cargo oil and cool the same, but not to the point that the shell of the tanker is cooled to an extremely low temperature and be subject to embrittlement and failure.

In addition, the complete cargo space of a tanker is utilized either by the liquefied petroleum gas in the spherical or spheroidal and cubical containers or the cargo of oil in the surrounding wing tanks resulting in minimum shipping cost. Also, there are no large void spaces subject to the accumulation of hazardous explosive gas mixtures.

Although the foregoing description has been directed to the use of my invention for the transport of liquefied petroleum gas in an ocean-going tanker, it can be adapted quite readily to permanent shore installations for storage purposes and can be used in railroad tank cars for transport purposes.

Furthermore, the invention is not limited to usage with liquefied hydrocarbons such as petroleum gases, but is applicable also to the storage, transport and usage of gases in a low temperature liquefied state including hydrogen, nitrogen, oxygen, ammonia and other common gases. And the shape of the liquefied gas containers need not be restricted, to the preferred spherical or ellipsoidal forms disclosed herein, or to a single innermost liquefied gas container.

Obivously, other modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations shouldbe imposed as are indicated in the appended claims.

I claim:

1. Means for the maintenance of a plurality of normally gaseous hydrocarbons in liquefied form comprising a plurality of nested containers, the innermost container thereof being adapted to contain a liquefied normally gaseous hydrocarbon having the lowest boiling point of said plurality of hydrocarbons and having a spherical configuration and the succeeding v outermost containers being nested withinfeach other and having substantially rectangular configurations, the spherical container being disposed within and being substantially completely enclosed by a surrounding cubical tank whereby the volume of said spherical container and the volume difference between said surrounding cubical tank and said spherical container enclosed therebyare substanstially equal, said container and tank being interconnected by pressure control means. i 1

2., In the means as defined in claim 1, said cubical tank enclosing a plurality of nested spherical containers each being substantially completely enclosed by an immediately surrounding spherical container, said tank and containers being interconnected successively with the immediately preceding outer'container except for the outermost.

3. In an apparatus for maintaining a liquefied hydrocarbon having a low vapor pressure at a pressure not greatly in excess of atmospheric, the combination of an outer container structure and an inner container structure, said outer container structure including a series'of tanks for containing a petroleum product normally liquid at ambient temperatures, said inner container structure being surrounded by said series of tanks on the bottom and two opposite sides thereof and comprising a central container and a rectangular tank surrounding and substantially enclosing the same and held in spaced relationship therewith, the volume-of said central container being substantially one half that of the surrounding and enclosing rectangular tank.

4. In an apparatus as defined in claim 1, said central container being spherical in form.

5. In an apparatus as defined in claim 3, said central container being spheroidal in form.

6. An assembly for the loading and discharge of a liquefied gas from a container comprising conduit means leading to and from said container, said conduit means including valve means for flow control therethrough, a reservoir for liquid and vaporized gas joined in bypass relationship to one of said conduit means and including valve means for the control of fluid flow to said reservoir in said bypass relationship, means for discharging lique-fied gas from said reservoir interconnected therewith including valve control means, means for leading oif vaporized gas from said reservoir including valve control means joined therewith, said conduit means leading from said container being joined to a refrigeration system via said valve means for flow control, said refrigeration system being interconnected with the vaporized gas leading off means and said reservoir whereby vaporized gas is changed to liquid state during the refrigeration process for discharge into said reservoir, and valve means for controlling communication between said refrigeration system and the other of said conduits for pressurizing said container during its unloading.

.7. In an assembly as defined in claim 6, said liquefied gas being taken from the group including hydrogen, nitrogen, oxygen; ammonia and liquefied petroleum gases.

8. An arrangement for loading and unloading a normally gaseous hydrocarbon in liquefied form including a container therefor and comprising a liquid loading conduit leading to said container for providing liquefied hydrocarbon thereto and a vapor exhausting conduit leading from said container, each of the conduits having vapor control means therein, a reservoir for liquefied and vaporized hydrocarbon joined in bypass relationship to said liquid loading conduit, valve means in the bypass relationship for flow control through said reservoir, discharge means for liquefied hydrocarbon including vapor control means joined to said reservoir, said vapor exhausting conduit leading to a refrigeration system for liquefying vapor, vapor flow means including a flow control joining said vapor exhausting conduit and said reservoir, and means for maintaining liquefied hydrocarbon in said container 7 under pressure during finloading comprising a pressure bypass arrangement betweenthe discharge side of said refrigeration system and said vapor exhausting conduit.

References Cited in the file of this patent UNITED STATES PATENTS 662,217 Brady Nov. 20,1900 1,680,873 Lucas-Girardville Aug. 14, 1928 2,148,109 Dana et a1. Feb. 21, 1939 8 Birdall Jan. 21, 1941 Goddard Dec. 5, 1950 Clar Apr. 24, 1951 Thompson May 1, 1951 McLaughlin June 10, 1952 Bergstrom Aug. 31, 1954 Morrison 2 July 9, 1957 Johnston Dec. 9, 1958 Howard Apr. 26, 1960 UNITED STATES PATENT. OFFICE CERTIFICATE OF CORRECTION Patent No 3,011,321 I December 5 1961 I. Frank Andrew 'Claus on h It is hereby certified that error appears in the abcve numbered patent requiring correction and that the said Letters vPatent should ,readas corrected below.

Column 6, read 3 line 31, ifor tla'e claim reference numeral "1" Signed and sealed this 17th day of April 1962,

(SEAL) Attest:

G, JOHNSON v I I v 'DAVID L. LADD' I Commissioner of Patents Attesting Officer

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