US3109295A

US3109295A - System and method for filling closed containers with volatile liquids

Info

Publication number: US3109295A
Application number: US170406A
Authority: US
Inventors: Reid F Stearns
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1962-02-01
Filing date: 1962-02-01
Publication date: 1963-11-05
Anticipated expiration: 1980-11-05

Description

Nov. 5, 1963 s s 3,109,295

SYSTEM AND METHOD FOR FILLING CLOSED CONTAINERS WITH VOLATILE LIQUIDS Filed Feb. 1, 1962 Mi 4| 24 26 3o 34 Reid F. Steurns Inventor /ZMXCW Patent Attorney United States This invention relates to a system and method wherein and whereby volatile liquids such as liquid propane or liquid butane may .be transferred from one container to another container. It relates particularly to a system and method of the kind described employing a closed storage container and a closed receiving container; that is, a system and method wherein the materials being transferred are maintained in the liquid state at substantially atmospheric temperature by the application of pressure.

When a volatile liquid is admitted into a closed container, the space within the container for vapor originally present therein and vapor resulting from evaporation of the admitted volatile liquid inside the container will decrease progressively as the quantity of liquid Within the container increases; consequently, the vapor will be compressed, resulting in a temperature rise in the vapor. A part of this vapor is condensed upon coming into contact with the surface of the liquid Within the container, and as the heat of condensation resulting therefrom cannot be distributed extremely rapidly throughout the entire liquid mass by natural heat flow the temperature prevailing at the liquid surface is higher than the temperature of the liquid below the surface. This compression of vapor and the resulting non-uniform temperature distribution in the liquid tend to cause the pressure of the vapor within the container to exceed the vapor pressure of the liquid corresponding to the mean liquid temperature. Pressure in the container may rise so high as to impair seriously the rate of or even completely block liquid delivery from the pump whereby the container is being filled, leaving the container only partially charged with liquid, possibly to no more than fifty percent of its volumetric capacity.

Various techniques have been proposed to reduce if not "atent "ice drawn from the receiving container, compressed, cooled, and condensed, and the condensate returned to the receiving container. This technique, While effective, is obviously one which requires at least some additional and expensive equipment.

Still another technique makes use of a vapor balance system where-in a vapor line is employed to equalize pressures between the receiving container and the storage container where-from the receiving container is filled. This technique, although simple, may be costly due to the length of vapor line required in some installations.

Even still another technique makes use of a condensing system wherein a heat exchanger, a condensate collector, and a condensate pump are employed. This technique, like that making use of a gas compression system, requires at least some additional and expensive equipment.

An object of the present invention is to improve upon existing techniques for transferring volatile liquids from one closed container to another by simplifying the equipment needed to effect such transfer eiiiciently, reducing the cost of this equipment, or achieving both a simplification and a cost reduction.

According to the present invention, a container filling or volatile liquid transtfer system is provided which includes conduit means extending from the bottom of a storage container or other source of volatile liquid material to a receiving container into which volatile liquid is intended to be loaded, this means being so connected to the receiving container that liquid may be introduced into this container at or near both its top and bottom simultaneously. Said in other words, and with particular relation to at least many em'sting receiving containers, the

7 present invention provides for using as an entry point of eliminate the aforedescribed pressure rise in the vapor space of a closed container being filled with a volatile liquid, that is, techniques other than that of simply permitting the vapor to escape to the atmosphere through a suitably adjusted relief or safety valve. Such escape is usually undesirable not only because the vapors involved are often hazardous due to their flammability as in the cases of propane and butane, but also because of the attendant loss of valuable materials.

One transfer and/or filling technique known to the prior art consists of the step of spray loading of volatile liquid directly into a receiving container from the top thereof, so as to obtain contact and heat transfer between the liquid being introduced and the vapor already present in the container. This results in some degree of cooling of the latter owing to the falling of the introduced liquid through the vapor and onto the liquid surface, particularly because in issuing through the spray fittings the introduced liquid has fallen in pressure and, correspondingly, in temperature on account of the Joule-Thomson effect. The spray loading technique generally works fairly well in respect of allowing a receiving container to be charged Within volatile liquid material to substantially its full capacity. This technique does, however, tend to be of limited utility because not many existing receiving containers are provided internally with spray fittings, and the overall cost of installing such fittings in a container initially lacking them is rather high.

Another technique makes use of a gas compression system wherein the vapors generated during transfer are withliquid being loaded not only a bottom connection or nozzle normally employed for liquid loading but also a top connection normally employed for vapor removal and pressure balancing. Entry of liquid through a top or normal vapor balance connection on such a receiving container furnishes at least some cooling and condensation of vapor in the container. Receiving containers themselves are contemplated to be in a variety of forms such as tanks of substantial size mounted upon highway vehicles, railway cars, and marine barges and ocean-going vessels.

Two advantages of this invention in its apparatus embodiment are that it can be fabricated of readily available materials, and adapted in use to a very great number of existing receiving containers. Another advantage is that it can be fabricated relatively inexpensively in the field for economical operation; Still another advantage is that it not only does not require long vapor balance lines but also does not require compression or heat exchange equipment, or any particular supply of cooling Water. Even still another advantage is that in operation it allows a receiving container to be loaded with volatile liquid relatively rapidly, frequently considerably more rapidly in fact than the container could be loaded by a liquid transfer apparatus of the prior art employing a vapor line or conduit for pressure balancing.

These and other advantages of the present invention as well as its nature and substance will be more clearly perceived and fully understood by referring to the folowing description and claims taken in connection with the accompanying drawing in which:

PEG. 1 represents a partially pictorial, partially schematic view of a container filling system according to this invention in which both actual external connections to the receiving container are made at the bottom of the container;

FIG. 2 represents a receiving container and segments of conduit means extending thereto according to this invention generally similar to FIG. 1 except that both amazes actual external connections to the receiving container are made at the top of the container, and

FIG. 3 represents a receiving container and segments of conduit means extending thereto according to this invention generally similar to FIG. 1 except that one actual external connection to the receiving container is made at the bottom of the container and the other is made at the top of the container.

Referring now to the drawing in detail, especially to PlG. 1 thereof, a bulk storage tank or container for volatile liquid materials under pressure such as liquefied propane or liquefied butane is designated ll). This container will have suitable fittings for filling and venting. It may be elevated on legs or stanchions 1E and 14 as shown, or it may be seated on concrete saddles. Particular details of construction and installation of storage container N do not, however, constitute any part of the present invention. Attached to and leading out of the bottom of the interior region of storage container it) is a liquid withdrawal or suction line 15, including a stop valve 17, which extends to and connects with the inlet side of product pump 18 which may be of any suitable kind. Liquid discharge line 2d including stop valve 22 extends from the outlet side of pump 18, and terminates in Y-fitting 24.

Connected to the outlet flanges of Y-fitting 24 are lines or conduits 26 and 28 including

stop valves

30 and 32, respectively. Connected to the outlet flanges of conduits 2s and 28, respectively, are conduits or lines 34 and 35. The latter two conduits preferably have some degree of flexibility, being either fully flexible or at least articulated. Conduits 34 and as having bleed valves 35 and 27 respectively teed oil of them near their outlet ends extend to tank truck 38, and are connected respectively to external flanges ill and -2 on receiving tank or container 44 of this truck. Both flanges 4t? and 42- are at the bottom of the receiving container. Flange 42 is the external connection means for the normal liquid loading or liquid inlet fitting of container 44, this fitting comprising a stop valve 4 1. Flange 4t), although located at the bottom of the receiving container, is the external connection means for the normal vapor balance or vapor outlet fitting of container 44, this fitting comprising a stop valve 43, and comprising further an open-ended tube 46 extending upwardly within the receiving container to a point close to the inside top surface of this container.

For operation of the system shown in FIG. -1, all six stop valves 17, 22, 3%, =32, ll and 43 are opened; bleed

valves

35 and 37 are closed, and pump 13 is started to withdraw liquid material from storage container it) through line 16 and discharge it through line 2i), Y-fitting Z4, and

lines

25, 28, 34 and 36. Desirably, Y-fitting 2d and lines 26, 28, 34- and as should be so designed that the flow rate through lines 26 and 34 is approximately equal to that through lines 23 and 36. In general, the flow rate through neither lines 26 and 34 on the one hand nor

lines

28 and 36 on the other hand should exceed about sixty erccnt of the total flow rate as delivered by pump 18 into line 20. By maintaining the flow rate at equal or near equal, e.g. 60-40, levels between the two discharge lines 26 and 28, the cooling eflect derived from the vapor discharge line will virtually offset the heating effect of the liquid discharge. Thus the pressure buildup will be kept at a minimum during the entire loading operation which Will allow an unintemiupted, maximum flow to be achieved. Furthermore this will eliminate the need for extensive pressure sensing devices, check valves and other paraphernalia usually associated with previous pressure filling systems.

It will be seen that although both external connections to receiving container '44 are made at the bottom of this container, flow of liquid through these connections from lines 34 and 36 will cause the container to be loaded at both top and bottom simultaneously so far as actual transfer of liquid material into the main available interior lvolume of the container is concerned. Liquid material issuing from the upper end of tube 46 under any significant driving pressure will strike against and splash back downwardly from the inside top surface of receiving container This liquid descending in splash or spray form will have at least some eiieot of cooling and condensing vapor in the part of the interior region of the receiving container above the surface of the liquid body therein, this surface of course being a steadily rising one as operation of pump 13 is continued.

The system. shown in FIG. 1 has been employed for the loading of railway tank cars with butane held liquid under pressure. A our representative of the kind loaded by this system had an interior or receiving volume of about 80 cubic metres. Loading time for this car using the system of FIG. 1, that is, with both actual external 7 conduit connections to the receiving container of the tank car being made at the bottom of the container, was about /2 hour to fill the container to about ninety percent capacity using a pump having a discharge rating of about 135 cubic metres per hour. Essentially, the system allowed the pump to deliver its rated discharge. Relatively, this was an appreciably superior performance to that represented by the approximately 1 hour time obtaining with the transfer system of the prior art for loading the same size car to the same extent, the prior art system employing a vapor balance line and introducing liquid into the receiving container of the car through a bottom connection only by means of a pump having a discharge rating of about cubic metres per hour. Apparently the prior art system had significant effect to impair the pump delivery.

Referring next to FIG. 2, flexible liquid lines or

conduits

134 and 136 connected at their inlet ends to the outlet flanges of conduits 26 and 23 respectively, and having bleed valves and 137 respectively teed off of them near their outlet ends, extend to tank truck 138, and are connected respectively to

external flanges

140 and 142 on receiving tank or container 144 of this truck. Both flanges 14d and 142 are at the top of the receiving container. Flange 142, although located at the top of the receiving container, is the external connection means for the normal liquid loading or liquid inlet fitting of container 144, this fitting comprising a stop valve 141,

" and comprising further an open-ended tube 146 extending downwardly within the receiving container to a point close to the inside bottom surface of this container. Flange 114i) is the external connection means for the normal vapor balance or vapor outlet fitting of container 144, this fitting comprising a stop valve 143.

It will be seen that although both external connections to receiving container 144 are made at the top of this container, flow of liquid through these connections from

lines

134 and 136 will cause the container to be loaded at both top and bottom simultaneously so far as actual transfer of liquid material into the main available interior volume of the container is concerned. Liquid material issuing at any significant driving pressure from the normal vapor balance fitting of which flange 140 is the external connection means will assume spray form'to at least some extent, and will have at least some effect of cooling and condensing vapor in the part of the interior region of receiving container 144 above the surface of the liquid body therein, this surface of course being a steadily rising one as operation of pump 18 (not shown in FlG. 2) is continued.

Referrim next to FIG. 3, flexible liquid lines or conduits 234 and 236 connected as their inlet ends to the outlet flan es of conduits 26 and 28 respectively, andhaving bleed

valves

235 and 237 respectively teed off of them near their outlet ends, extend to tank truck 238, and are connected respectively to external flanges 240 and 2A2 on receiving tank or container 244 of this truck. Flange 249 is at the top and flange 2 52 is at the bottom of the receiving container. Flange 242 is the external connection means for the normal liquid loading or liquid inlet fitting of container 244, this fitting comprising a stop valve 241, wlule flange is the external connection means for the normal vapor balance or vapor outlet fitting of this container, this fitting comprising a stop valve 243.

It will be seen that with external connections made to receiving container 244 as shown in FIG. 3, flow of liquid through these connections from lines 234 and 235 will cause the container to be loaded at both top and bottom simultaneously. Liquid material issuing at any significant driving pressure from the normal vapor balance fitting of which flange 249 is the external connection means will assume spray form to at least some extent, and will have at least some eifect of cooling and condensing vapor in the part of the interior region of receiving container 244 above the surface of the liquid body therein, this surface of course being a steadily rising one as operation of pump 13 (not shown in FIG. 3) is continued.

Referring finally to FIGS. 1, 2, and 3 as a group, and especially to

tank trucks

38, 138, and 238 shown in order in these figures, the arrangement of flanges for the making of external connections to the receiving container of the tank truck shown in FIG. 1, namely, the flanges for the normal liquid inlet and the normal vapor outlet fittings both being at the bottom of the receiving container, is the preferred arrangement and the one most likely to be encountered in practice. It is preferred on a basis of convenience for two reasons, first because connections to both fittings can be made in essentially a single location, and second because no climbing to the top of the receiving container is required on the part of the man making the connections.

The next preferred arrangement of flanges is that shown in FIG. 2, namely, the flanges for the normal liquid inlet and the normal vapor outlet fittings both being at the top of the receiving container. This arrangement at least provides the convenience of allowing'connections to both fittings to be made in essentially a single location. It is to be understood in any case, however, that the present invention has utility with all receiving container fitting connection flange arrangements illustrated. It is to be understood further that the particular illustrations of various connections as being flange-type connections are exemplary only, since many other types of connections for liquid lines or conduits such as sleeve-type, screw-type, bayonet-type, etc., are well known in the art. it is to be understood still further that for any particular receiving container fitting connection arrangement encountered, suitable means in the nature of booms, chocks, derricks, etc., will be provided as needed for locating and supporting the several liquid lines or conduits involved in the utilization of the present invention. Conduit locating and supporting means of the kind contemplated are, however, well known in the art and do not form any part of this invention. Accordingly, no such means are illustrated. In this connection, however, it is to be understood that the liquid transfer and filling system of this invention will not have a requirement of locating and support means such as booms, chocks, derricks, etc., in excess of that of any system of the prior art for a given installation.

It is intended to secure protection by Letters Patent of the foregoing-described invention in all its aspects as expressed in the following claims to the broadest extent that the prior art allows.

What is claimed is:

1. A system for filling closed containers with volatile liquids, said system comprising (1) a closed storage container for liquefied product materials under pressure such as liquefied propane or liquefied butane, said storage container having a bottom interior region, (2) a product pump having an inlet side and an outlet side, (3) a liquid discharge line extending from the bottom interior region of said storage container to the inlet side of said product pump, (4) a closed receiving container, said receiving container having at least one fitting wherethrough liquid material may be introduced into it near its top and at least one fitting wherethrough liquid material may be introduced into it near its bottom, and (5) liquid discharge lines extending from the outlet side of said product pump to the fittings of said receiving container, said liquid discharge lines being so designed that the flow rates through them are approximately equal.

2. A system for filling closed containers with volatile liquids according to claim 1 in which said liquid discharge lines extending from the outlet side of said product pump to the fittings of said receiving container are so designed that the flow rate through neither line exceeds about sixty percent of the total flow rate as delivered by said pump.

3. A system for filling closed containers with volatile liquids according to claim 1 in which the actual connections of said liquid discharge lines extending from the outlet side of said product pump with the fittings of said receiving container are both made at the bottom of said receiving container.

4. A system for filling closed containers with volatile liquids according to claim 1 in which the actual connections of said liquid discharge lines extending from the outlet side of said product pump with the fittings of said receiving container are both made at the top of said receiving container.

5. A system for filling closed containers with volatile liquids according to claim 1 in which the actual connec tions of said liquid discharge lines extending from the outlet side of said product pump with the fittings of said receiving container are made one at the bottom and one at the top of said receiving container.

6. A method for filling closed containers with volatile liquids, said method including the steps of (1) discharg ing one stream of a volatile liquid into the interior region of a closed receiving container near the bottom thereof, and (2) simultaneously discharging another stream of said volatile liquid, having an approximately equal flow rate to that of the first stream, into said interior region near the top thereof.

7. A method for filling closed containers with volatile liquids according to claim 6 in which neither of said liquid streams has a flow rate exceeding about sixty per-' cent of the total flow rate of liquid discharged into the interior region of said receiving container.

References Cited in the file of this patent Reed July 25, 1961

Claims

6. A METHOD FOR FILLING CLOSED CONTAINERS WITH VOLATILE LIQUIDS, SAID METHOD INCLUDING THE STEPS OF (1) DISCHARGLIQUIDS, SAID METHOD INCLUDING THE STEPS OF (1) DISCHARGING ONE STREAM OF A VOLATILE LIQUID INTO THE INTERIOR REGION OF A CLOSED RECEIVING CONTAINER NEAR THE BOTTOM THEREOF,