US2012361A

US2012361A - Apparatus for handling liquefied gases

Info

Publication number: US2012361A
Application number: US565154A
Authority: US
Inventors: Rosswell W Thomas; Frederick J Harlow
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1931-09-25
Filing date: 1931-09-25
Publication date: 1935-08-27
Anticipated expiration: 1952-08-27

Description

R. W. THOMAS El' Al..

APPARATUS FOR HANDLING LIQUEFIED GASES Filed Sept. 25, 1931 m .um

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Patented Aug. 27, 1935 PATENT OFFICE APPARATUS Fon HANDLING IJQUEFIED -GAsEs f BoaIwell W. Thomas and Frederick J. Harlow,

' Detroit, Mich., as sign'ors to Phillips Petroleum Company, Bartlesville, 0kb., a corporation of Delaware Application September 25, 1931, Serial No. 565,154

6 Claims. (Cl. 158-53) K will be seen that a cu. ft. of the same liqueed This invention relates to a method of and apparatus for vaporizing volatile liquids and particularly liquened petroleum gases.

One of the' objects of the present invention is to providean apparatus wherein the pressure of the. liquefied gas is reduced before the same enters that portion of the apparatus in which the latent heat of vaporization is restored to the liquefied gas, and to control the feed so as to maintain substantially constant the pressure at that point, regardless of the temperature of the h a `-1 safety appliances are incorporated w tus and also an automatic device the delivery of the gas to the 1 l 1 apparatus after the same has been 1 t from a liquid to a gas. The invention also contemplates the automatic supplyoi' the heating medium used, to supply the latent heat of vaporizing, by using the pressure o r temperaf ture ofthe gas which is passed through the heat exchange unit cfthe apparatus. Further pro-' vision is made for the manual operation of the apparatus when, for any reason, the automatic elements of the apparatus cease to function.

v It has been found desirable to liquefy certain of the volatile petroleum gases used for commercialpurposes so that the same can be disftrlbuted to the'trade for consumption in an economical manner. For example, to iiquefy these gases by the compression and cooling method; the following steps mustbe taken. The gas is first compressed slightly above the vapor pressure of the liquid at the temperature of the coolmedium, which is to be used in cooling the compressed gas.' v.After compression, the gas is subjected to contact with the cooling medium by means of a tube condenser or the like, and the heat of compression removed from vthe compressed gas. However, Aat this point, the gas is not condensedv or liqueiled until an additional amount oi heat is removed, this additional amount being the latent heat of vaporization or the heat of state of change. After this amount of, heat has been removed, the compressed gas will condense and shrink in volume. .To show the many problems involved, all of iwhich must be taken into consideration in constructing a device of this kind,l we will show certain specifications of one of the petroleum gases, i. e. commercial butane, which has proven most satisfactory in a machine of this kind.

Commercial butane gas at 60 F. will shrink in volume so that 1 cu. ft. of liquid will contain 240 cu. ft.fof gas at the same temperature. vAs 'l cu. ft. of butane gas contains 3200 B. t. u.s, it

gas contains 768,000 B. t. u.s, which is an enormous concentration of heat. For this reason, it is usually impractical to utilize the liquefied gas because of the amount of heat contained within the same. The greatest utilization of this gas demands that the liqueed gas be restored to its natural state, i. e. a gas. The vapor pressure of the same commercial gas at 70 F. is about 33 pounds per sq. in. which pressure increases until at; 130 F. the premure is about 110 pounds per sq. in. This change in vapor pressure, with temperature change, must also be taken into consideration in a vaporizing device, so that regardless of the temperature of the atmosphere, the vaporizer will function in `a uniform way.

To vaporize the liquefied gas, steps must be takenwhich vare the reverse of thefliquefying process pointed out above. This invention, there- `fore, contemplates a method-and/or apparatus for the different parts of the apparatus, all of which will be described more fully hereinafter.

Referring to the accompanying drawing, the figure represents a diagrammatic elevation of an apparatus embodying our invention, certain parts of which are shown in section.

The following description, charted by arrows, shows the normal course of the gas in a liquid state until the same arrives at the place of consumption as a gas. In the arrangement shown, gas enters the pipe A in a liquid state by vapor pressure from a source of supply, usually a storage tank. The normal path of the gas from the storage tank is through the pipes A, B, C, D and strainer 3 to the heat exchange unit P, wherein the liquid gas is finally returned to a true gas. In the unit P, the expanded liquid or vapor, which has not yet become a true gas because the latent heat of vaporization has not been supplied, becomes a true gas. From the heat exchange unit through which it is preferably conducted around a series of pipes I2, to be treated by a heating medium, the true gas passes through thc line J to the safety trap i3 which will hereafter be described. From the safety trap, the gas is con ducted through the lines K, W and G, and through the strainer 24 into the gas regulator I1. After the gas leaves the regulator, it traverses the remainder of the line G, lines V, T and S to the place of consumption. It takes this course because the valves 8, 9, i0, Il, i8 and i! are closed, and l, 2, l, 2|, 1,14, 22 and 23 are open..

Having described the course of theliquid and gas through the apparatus, we will take up and describe the automatic devices which control and distribute the gas throughout its course through the apparatus. Connecting the lines B and C is the expansion valve 4, of any standard make, the position of which is controlled by a diaphragm 5 of the weight and lever or spring control type. The valve 4 functions as follows:-

The volatile liquid arrives at the intake of valve 4 by virtue of the 'vapor pressure of the liquid in the storage tank at a pressure higher than that desired in the heat exchange unit P. In the body of' the valve 4, thereis a valve head attached to the lower end of a valve stem; the upper end of the stem being connected to the center of the diaphragm 5 in the diaphragm chambenwhich is part of the valve proper. As liquid gas passes through the body of the valve 4 from B to C when the

valves

1, 8, 9, I and II in the lines D, H, I, E and F respectively are closed, there will be a back pressure built up on the line C, part of lines D, I, E and the whole of O', all of these lines being beyond the expansion valve 4. This pressure will correspond to the vapor pressure in the storage tank, minus the pressure required to conduct the gas through these lines. Now, if the weight. 4 is removed from the lever arm 4b, pivoted at 4 intermediate the ends thereof and forming part of the valve mechanism 4, the pressure on the top side of the diaphragm 5 will cause the stem to force downwards thereby closing valve 4. If the weight 4n is returned to the lever arm 4b, it will be readily-seen that by balancing the correct pressure on the top side of the diaphragm 5, any desired pressure in the closed systemlbeyond the seat of the valve 4 can be obtained. It will be seen that any variations in demand-on the heat exchange unit P will also vary the pressure in the lines D, C, part of lines I and E, and all of O.

Finally, through line 0 any variation in back pressure will be transmitted to the top of the diaphragm which is now counter-balanced by the weight on the lever arm and any drop in pressure in line O will cause the valve to open as the balancing pressure to the weight has been lessened. 'I'he valve will then`remain open until the pressure in line O again builds up to a pressure which will close the valve to a point consistent with the discharge pressure of the valve 4. 'Ihe control of the liquid passing through the valve 4 is therefore automatic and maintainedA expanded fluid enters the heat exchange unit Pv at about 5 lbs. pressure. Not only does the valve 4 feed fluid to the heat exchange unit so as to maintain constant the feed as governed by conditions around the heat exchange'unit, but it also reduces the pressure produced by the source of supply to a proper pressure so that the liquid can be properly treated. I'he pressure of the liquid as it reaches the valve 4 is considerably over 5' lbs.

The heat exchange unit P is of the multi-tubular type and comprises a series of pipes I2 around which the gas flows so as to increase the area of the gas exposed to the eiect of the heating medium. The heating medium which enters the heat exchange unit through the control valve IB. or IB", depending on which directionV it is passed through the exchanger, can be either hot water, steam, hot oil or the like. Electrical resistance elements can be used to supply the latent heat of vaporization, in which case they would be used instead of the tubes I2, and might be controlled by a rheostat instead of the valve I6 or I6, which controls the ow of the heating medium to the heat exchange unit. The output of the rheostat would be governed by a'. thermostatic element I5 in the pipe J. Provision has been made to permit draining the gas chamber of the heat exchange unit P through the drain 30,' which is located in the lowest point of this unit. Through the drain 32, the heat supplying medium can be drained away from the pipes when it is desired to eliminate all possibility of the heating medium freezing around the pipes, when the apparatus is closed down in cold weather.

In the line J between the valve I4 and the safety trap I3, is the automatic control device I5 for regulating by temperature the supply of the heating medium to supply the latent heat of vaporization. This control is through the valve I8 in the line carrying the heating medium to the heat exchange unit. It will be thus seen that the temperature in the line J controls the amount of the heating medium which enters the heat exchange unit P, in which the liquefied gas is changed into a true gas. The thermostatic control IE is not absolutely essential to the successful operation of the apparatus, and, when employed, may be of any suitable and desirable conventional or standard construction. A thermostatic control device suitable for our purposes is disclosed in U. S. Patent No. 1,278,749 dated September 10, 1918.

The safety trap I3 is of any approved iioat type liquid valve control which may function as fol1ows:-'Ihe single seated unbalanced valve |00 operated by the` float IUI, closes in the direction of gas or liquid flow when the liquid in the float chamber rises to a point which is below the bottom of the line K, so that no liquid will enter the line K. This safety trap is not an absolutely essential part of the apparatus, and may or may not be used. When used, it may be of any suitable and desirable conventional or standard construction. It is a safety device of merit.

'I'he gas regulator I'I may be of the type shown in Fig. 4 of the U. S. Patent 485,386 dated November 1, 1892, and its function is to automatically reduce and maintain constant the pressure of gas for delivery to the burners or the consuming appliances, regardless of demand or rate of iiow. The gas regulator I1 may be of any suitable and desirable conventional or standard construction. 'Ihe pressure of the gas between the regulator and burners can be read on the pressure gauge or manometer 25.

The many safety features of the apparatus will now be described. At the top of the safety trap I3, there is a line L which Joinswith the lines K, U and W. In the line L is valve I9. This valve is normally closed and is placed in the line so that pressure can be equalized on both sides of the unbalancedvalve within the safety trap I3, should it close as a safety measure. Connecting the lines I-I and A is the line F in which there is check valve II, which may be of any suitable and standard positive seating type, but which preferably is of the construction disclosed in applicants copending application, Serial No. 517,337, filed Feb. 20, 1931. against the pressure of the liquid in the storage tank so that the liquid in the line F tends to keep the check valve closed under all normal operating conditions. However, should the valves I4,

This valve is set I 3, 22, l1 or 28 in the discharge lines from the heat exchange unit P, be closed and continue to stay closed, and the heating medium be left circulating in the heat exchange unit P, the tend-` ency would be to increase the pressure of the gas in the heat exchange unit pipes to above that in the storage tank, even though no more liquid were admitted by valve 4. In this case, the back pressure thus produced would cause the valve I I toopen, thus completing a direct communication through line F and the check valve to the storage tank. This check valve I I, therefore, provides an escape for high pressure liquid or gas from the vaporizing device preventing the pres.- sure therein from rising substantially above the storage tank pressure and greatly diminishing the possibility of a rupture of any of the appliances incorporated therein. By opening the valve 9,

` any liquid in the trap I3 can be passed from the gas to the liquid carrying portion of the system.

V Other safety appliances will be seen at the top of the line T where a pop valve 26 is set to blow oil when excessive pressure is built up between the regulator I1 and consuming points.- The lead from this pop valve is through the line M to the vent pipe M2 and away from the building housing the apparatus. In the end of the heat exchange unit through which the gas .passes last, is the relief valve 29, set so lthat when excessive pressure is built up in the apparatus, relief may be had.4 The lead from this safety valve 29 is through the line 'N to the vent outside of the building housing the apparatus. Besides the above mentioned safety features are the automatic expansion valve 4, the gas regulator I1, and thepressure gauge or manometer 25, all of which have been described previously. There is also the safety feature incorporated in the pressure gauge in the line A, from which pressure can be noted.

Through the control valve 4, liquid gas is automatically fed to the heat exchange unit P where it is converted into a true gas and by means of the regulator I1. this gas is reduced to the proper pressure for vdelivery and use. If, for any reason, the two above automatic appliances 4 or I1 cease to function, either or both, can be removed from the apparatus and the apparatus can be operated under manual control. After closing valves I, 2, -20 and 2|, (valve I0 is closed when liquid gas is being fed by automatic reducing valve 4), the expansion valve 4 can be removed as a unit from the apparatus after the three couplings supporting it have been undone. Thereafter, by opening ly from the heat exchanger P after the valves 22 and 23 in the line G have been closed.' The. manual control in this case is through the valve I8 in the line U. The pressure to which the gas is reduced and at which itis being fed to the burners can be read on the pressure gauge or manometer 25. From/the above, it will be seen that the apparatus is automatically controlled throughout, but can be operated by a manual control if, for any reason, any of the automatic controls do not operate properly.

Attention is called to the fact that all of the system leading to the heat exchanger P is for liquid gas, while that leading from P is for vthe true gas after it has passed through the heat exchanger unit P. Each line leading from S may include a gas regulator so that any number of burners or appliances can be supplied at different gas pressures providing the regulator for each line is set at the desired pressure, which must always be lower than the outlet pressure from I1. This is desirable because it is sometimes advisable to deliver to different points of gas use at different gas pressures.

If desired, an automatic shut-oil valve 50, which may be of the type disclosed in U. S. Patent No. 1,678,202 dated July 24, 1928 preferably of the single seated unbalanced valve type, may -be mounted in the line J posterior to the thermostatic control I5, or at any suitable point, preferably just ahead of the vapor regulator I1. This valve, which may be of any suitable and desirable conventional or standard construction, may be wired into the motor control circuit' of anair-gas plant, so that when the plant is shut down, the single seated unbalanced valve 50 is closed by means of the gas pressure, assisted by a spring, and is held closed by the spring and the unbalanced pressure. This eliminates slight seepage of gas from the vaporizer through the outlet vapor regulator I1 to the proportioning machine for the air and gas or point of use, with consequent loss of vapor and possibility of creation of a fire or explosion hazard. t

From the foregoing it is believed that the construction, operation and advantages of our invention may be readily understood by those skilled in the art, and We are aware that changes may be made in the details disclosed, without departing from the spirit of the invention, as expressed in the claims.

What we claim and desire to secure by Letters Patent is:

V1. In an apparatus ofthe character described, a vaporizer for liquefied gas, an inlet conduit for conducting liquefied gas to said vaporizer, an outlet conduit for conducting the vaporized gas from the vaporizer, automatically operating means interposed in the last mentioned conduit for reducing the pressure of said vapor and maintaining the same substantially constant,

' means interposed in the inlet conduit for automatically controlling the pressure of the liqueed gas fed to the vaporizer, means associated with the vaporizer for passing a heating medium through the latter in indirect heat exchange with the liquefied gas ilowing through the vaporizer, and thermostatic control means associated with said outlet conduit and the heating medium means for regulating the volume of the heating medium fed through the vaporizer.

2. In an apparatus of the character described, a vaporizer of the heat exchange type, a conduit for feeding liquefied gas into said vaporizer, a regulator interposed in said conduit for automatically controlling the pressure of the liquefied gas flowing to the vaporizer, and a by-pass pipe associated with the conduit and provided with an automatic check valve for by-passing liquid reversely around said regulator, whereby flow in the reverse direction can occur if the vaporizer pressure becomes higher than the pressure of the source of the liquefied gas.

3. In an apparatus for vaporizing liquefied gas, a vaporizer, an inlet conduit for conducting liquefied g'as to said vaporizer, an outlet conduit for conducting vaporized gas from said vaporizer, means interposed in the last mentioned conduit for controlling the pressure of said vaporlzed gas,

means interposed in the inlet conduit for controlling the pressure of the liquefied gas fed to the vaporizer, means for supplying heat to said vaporizer, and vaporizer control means associated with said beat-supplying means and said cutlet conduit for controlling the rate of vaporization in said vaporizex.

4. In an apparatus tor vaporizing liqueiled gas,

a vaporizer, an inlet conduit for conducting liquefied gas to said vvaporizer, an outlet'conduit for conducting the vaporized gas from the vaporizer, automatically operating means interposed in the last mentioned conduit for reducing the pressure of said vaporized gas and maintaining the same substantially1 constant, means interposed in the inlet conduit for controlling the pressure of the liqueiled gas fed to the vaporizer, means for imparting heat to said vaporizer, and thermostatic control means associated with said last named means and responsive to temperature conditions in the outlet conduit for maintaining the temperature in the vaporizer within a predetermined temperature range.

5. In a gas apparatus, the combination of a source of liquid gas supply, a heat exchange chamber, a pipe for conducting liquidvgas from said source of supply to said chamber, pressure reducing means interposed in said pipe, a conduit arranged anterior to said chamber leading from said pipe, t'o said source of liquid gas supply, a check valve arranged in said conduit and exposed on opposite sides thereof directly to the amasar liquid gas pressure from said source oi supply and to the normally relatively reduced gas pressure from said heat exchange chamber, whereby said check valve is normally held in closed position but is opened to aiIord relie! for the gas when the pressure of the gas in the heat exchange chamber becomes greater than the liquidA gas pressure at the source of supply.

6. In an apparatus of the character described. a vaporizer, a conduit for feeding a liquened gas to said vaporizer. a regulator interposed in said conduit for automatically controlling the pressure of the liquefied gas ilowing to the vaporiaer, a by-pass pipe associated with' the conduit and provided with an automatic check valve for bypassing liquid reversely around said regulator. whereby flow in the reverse direction can occur if the vaporizer pressure `becomes higher than the pressure of the source oi' the liquefied gas, an outlet conduit for conducting vaporized gas from the vaporizer, automatically operating means interposed in the last mentioned conduit for reducing the pressure of said vaporized gas and maintaining the same substantially constant, and means for imparting heat to said vaporizer.

ROSSWELL W. THOMAS. FREDERICK J. HARIDW.