US2378077A - Method of and system for dispensing liquefied fuel - Google Patents

Description

June 12, 1945. o. L. GARRETSON METHOD OF AND SYSTEM FOR DISPENSING LIQUEFIED FUEL Filed June 22, 1942 INVENTOR L. GARRETSON Patented June 12, 1945 UNITED STATES PATENT OFFICE METHOD OF AND srsrau Foa' msrnnsnva uommnn run.

of Delaware Application June 22, 1942, Serial No. 448,023

6 Claims.

My present invention relates to improved apparatus for vaporizing a volatile liquefied fuel.

More specifically, my invention discloses an improved liquid feed system for utilizing liquefied petroleum gases, such as propane, butane, and mixtures thereof. In my system as herein disclosed, the fuel is stored in large tanks, preferably underground. The fuel is withdrawn from storage in the liquid form, in order to avoid the variation in composition and heating value which occurs when such fuels are withdrawn as vapors. The comparative virtues of liquid versus vapor withdrawal are well known to the art, both types of operation having been used extensively in the Past.

In the past, however, the liquid feed type dispensaries have had a common drawback in the matter of vaporizing the liquid after withdrawal from the storage vessel. This is a particular obstacle where straight commercial or normal butane is to be used, because of the low vapor pressure (or, conversely stated, the high boiling point) of this particular hydrocarbon. The condition is of course most troublesome in localities where the climate is relatively cold. Early systems for this service have employed Vaporizers heated by water from a gas-fired water heater. Other proposals, some of which were actually placed in operation, included extensive underground piping networks to absorb heat of the earth for vaporization; earth vaporizers augmented by circulating water from a city water system; atmospheric or air-heated vaporizer coils. sometimes placed in a heated dwelling or else in a separate vaporizer house. above methods of vaporizing have obvious disadvantages from the standpoints of equipment cost, excavating cost, personal hazard and often a combination of these factors.

My invention is a practical answer to the above ou lined problem, as it employs the free heat of the earth for vaporization, and does it in a manner which is safe, eflicient and economical of execution.

An object of my invention is to provide a most economical system for vaporization of a liquefied fuel gas.

It is a further object to provide a system of the above class which is entirely safe in operation.

It is an object to attain adequate vaporization capacity in such a system without resort to artificial heating means, or to extensive excavation for installation of heat absorbers.

Other objects and advantages will be recogl8 closure.

Each of the 3 transverse sectional view of a portion of Figure 1,

taken about the line 2-2.

Referring now to Figure 1, the numeral It indicates a buried storage tank suitable for liquefled petroleum gases. The tank is equipped with 10 the usual servicing and safety appliances, which may include a filler valve, a pressure relief valve, a liquid level gauge, etc. These appliances are indicated collectively by the numeral II and are not shown in detail, being apart from my dis- It is suflicient, for present considerations, to state that the accessories referred to are usually connected in a common riser as indicated by numeral l2, and are protected by a casing IS, the interior of which is accessible from ground level through a hinged or removable cover It. The structure thus far described is, of itself, old and common in the art.

Within the tank I0, I provide a \pair of riser pipes l5 and it, which are joined at a point 95 outside the tank by a horizontal conduit l1. Connected to an opening in the top side of conduit I! is a pressure regulator l8, provided with an outlet conduit It. The outlet conduit passes through a suitable aperture in the housing l3,

as at point 20, and enters the horizontal conduit at 2| and emerging at 22, from whence it proceeds eventually to the point of use. At or near such point of use, a second stage regulator (not shown) may be provided if desired.

The conduit I9 is located concentrically within the casing or conduit I'l, forming a continuous and imperforate channel therein. The juncture of the conduits l1 and I9 at points 2| and 22 may be made by welding, by threaded pipe fittings, bolted flanges, or whatever means may be most expedient and economical. The important consideration here is that two parallel pressure-tight channels be defined, with due provision made to prevent leakage between the channels or to the ground or other surrounding medium.

While a plain tube would serve in many cases, it is more conducive to good operation to provide longitudinal fins arranged radially about the portion of tube l9 which lies within the casing I I. Figure 2 illustrates the essential features of the fin arrangement. It is immaterial whether the fins are a part of the conduit I9 or of the casing l1; indeed they might be attached to both members, or the whole conduit assembly including the radiating fins between points 2| and 22 could be formed of a single metal casting. Figure 2 illustrates the cast type of construction, in which the fins 24 are joined integrally with the conduit I9 and casing l'l, forming a plural- It is understood ity of elongated chambers 25. that the fins 24 are to be either perforated or cut out entirely in the region of the extremities of casing I1, so that the risers l5 and IE will have common access to all of the chambers 25.

In operation, the tank I is filled to a desired level (26-46) with a liquefied gas such as butane, for example. Upon the first such filling, air and later a mixture of air and butane vapor will at first be withdrawn from the line l9. Upon continued purging of the air and butane vapor, liquid butane will shortly rise in the pipes I and I6, and will gain admittance to the regulator l8 through the casing II.

For normal operation subsequent to the first filling, the regulator I8 is set to deliver an outlet pressure of some 3 to 6 p. s. i. to the line l9. At normal earth temperatures (which may vary between 40 and 75 F. in various localities), the vapor pressure of the stored butane will be in the range of 15 to 35 p. s. i. Thus, at very low rates of-fiow, the liquid will be substantially vaporized at the regulator orifice where pressure reduction occurs. At any higher flow, however, at least a substantial part of the fuel will pass through the regulator valve in liquid form and vaporization will proceed in the line IS. The resultant cooling of the liquid in process of vaporization will cause an exchange of heat between the content of line I8 and the surrounding liquid in casing l1. resulting in a cooling effect upon the latter liquid also.

- Because of the change of density brought about by cooling the liquid in the casing IT, a thermosyphon action is induced, since the heavy, cooled liquid will seek a lower level and warm, lighter liquid will seek to rise and replace the cool portion. The direction of circulation in the casing l1 and the appended riser pipes l5 and I6 is of no practical consequence, but it is nevertheless evident that circulation will occur in the direction indicated by the arrows in Figure 1. This statement is based upon observations of many types of coil Vaporizers, in which it has been noted that the colder portion of the coil is near the inlet end of the coil. Thus the liquid at the left end of the heat exchange casing ll will normally be more dense than that at the right hand end, and this state of conditions is conducive to a circulation in the indicated direction.

The continuous circulation of liquid above described serves the purpose of bringing all of the stored liquid into heat exchange contact with the portion which is being vaporized. Thus the heat content of the whole stored mass of liquid is made available for vaporization of the portion to be used. Meantime, heat is transferred from the earth to the stored liquid, through the walls of the tank I 0, and the heat lost to the vaporizing process is continually replenished. Undue refrigeration of the stored fuel is thus prevented and a high enough vapor pressure for satisfactory operation is assured.

Various modifications can be densed, all within the scope of my invention. I also contemplate the use of additional vaporizer means beyond the outlet of my improved storage tank vaporizer in installations where extremely adverse conditions of use render such auxiliary devices necessary. Theprimary utility of my device, however, lies in the fact that the structure disclosed is adequate for most normal usage, and the expense of providing artificially heated or other auxiliary vaporizers is thus obviated except in very extreme service.

I claim:

1. In a fuel dispensing system of the class described which includes a, storage tank for liquefied fuel: a thermosyphon circuit associated with the storage tank which is comprised of a liquid riser, a liquid return and a communicating conduit therebetween forming a circuit; a pressure regulator associated with said circuit and adapted to tap oil a portion of the content thereof at a reduced pressure; a conduit for returning the said portion in heat exchange relationship with the said circuit.

2. A fuel dispensing system for liquefied gas which comprises a storage tank for the liquefied fuel, a first conduit for setting up a circulation of the liquid, the opposite ends of the said conduit extending below the surface of the liquid, a second conduit for withdrawing fuel from said first conduit, pressure reducing means in said second conduit, the low pressure side being in heat exchange relationship with the first conduit.

3. A fuel dispensing system for liquefied gas which comprises a storage tank for the li uefied fuel, a first conduit for setting up a circulation of the liquid, the opposite ends of the said conduit extending below the surface of the liquid, a second conduit for withdrawing fuel from said first conduit, pressure reducing means in said second conduit, said conduits being concentrically arranged.

4. The method of dispensing and vaporizing liquefied gas from a quantity of liquid gas in a storage member comprising circulating the liquid gas by thermosyphon forces through a conduit, drawing of! the gas from an upper point in the conduit, expanding the gas, and passing theexpanded gas in heat exchange relation to the conduit to increase the thermosyphon forces and to accelerate the thermosyphon circulation.

5. A fuel dispensing system comprising a storage tank for liquefied fuel, an inverted U-shaped conduit disposed with one leg of the U in communication with the tank adjacent the bottom of the tank, and the other leg of the U in communication with the tank at a point above the point of communication of the first leg but in the lower half of the tank, a dispensing line connected to the conduit at an upper portion thereof, and passing in heat exchange relation therewith, and a pressure reducing valve in said line at a point before the line passes in said heat exchanging relation to said conduit.

6. A fuel dispensing system comprising a storage tank for liquefied fuel, an inverted U shaped conduit disposed with one leg of the U in communication with the tank adjacent the bottom of the tank, and the other leg of the U incommunication with the tank at a point above the point of communication of the first leg but in the lower half of the tank, a dispensing line connected to the conduit at an upper portion thereof, and a pressure reducing valve in said line.

- OWEN L. GARRETSON.

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