US2234407A - Apparatus for vaporizing liquid fuel - Google Patents

Description

March 11, 1941. W H p-{OAGLAND` I 2,234,407

APPARATUS FOR VAPORIZING LQUIDIFUEL Filed July 25, 1939 To urnmion y fF rVnpor Vapor/ Liquid Level Confrd Patented Mar. ll, 1941 PATENT oFFicE APPARATUS FORl VAPORIZING LIQUID FUEL Walter H. Hoagland, Webster Groves, Mo., as-

signor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application July 25, 1939, Serial No. 286,393

s Clarins.

The present invention relates to the vaporization of liquid fuel and may be employed in connection with various fuel-consuming devices, such as internal combustion engines, heaters,

stoves, furnaces and the like.

It has been found desirable to liquefy certain normally gaseous petroleum hydrocarbons, as for example propane and butane, so that the same may be distributed to the trade in an economical l0 manner. It then becomes necessary to provide a unit capable of revaporizing these 1iqueled gases in order to efliciently burn the same. This is due to the fact that liquid propane, for example, contains 690,000 B. t. u.s per cubic foot and the same liquid cubic foot will yield approximately 275 cubic feet of gas at the same temperature (0 F.) Obviously, the problem of eilicient combustion will be much simpler if the hydrocarbon is utilized in the gaseous state.

an improved unit for carrying out the vaporization of liquefied fuel gases prior to utilization.

It is a further object of this invention so provide an arrangement whereby advantage is taken of changes in prevailing atmospheric temperatures to decrease the operating expenses of the unit.

Generally speaking, vaporizing units of this type comprise basically three elements; a storage place for the liquefied gas, means for reducing the pressure on the liquefied gas, means for vaporizing the liquefied gas by heat exchange and some method of regulating the pressure of the vaporized liquid issuing from the heat exchanger.

Another object of this invention is to provide an arrangement whereby only a portion of the demand for hydrocarbon vapors is supplied A through'the heat-exchanger, a large portion being supplied directly from the top of the storage o tank, automatic controls being provided whereby the supply of vapors ready for combustion will never be exceeded by any sudden and unusual demand upon the unit. l

Referring to the accompanying drawing. the gure represents a schematic plan of the invention.

In the drawing, a pressure storage tank I is provided with a-liquid line A, incorporating two shut-off valves 2 and 3, and leading to a conventional -type vaporizer 4 of the heat-exchanger type. A vapor line B leads from the top of the vaporizer 4 to a gas pressureregulator 5 and thence through vapor line C toa point of utilization. In vapor line B is a pressure relief An object of the present invention is to provide valve 6 and shut-off valve 1. Between valves 6 and 'I is a third valve level control 9.

The vaporizer 4 is provided with a steam line D including a limit pressure control device as designated by I0 and II. j 5 A vapor line E leads from the top of the storage tank I through a diaphragm valve I2 and a shut-off valave I3 to vapor line B.

A vapor line F provided with shut-off valves I4 and I5 and pressure relief valve I6 leads from 10 the top of tank car 22 to vapor line B. A liquid line G leads from the bottom of tank car 22 to the bottom of storage tank I, this line embodying a shut-o valve I'I, pressure relief valve 23, liquid pump I8, shut-01T valve I9, and shut-ofi valve 15 2|.

s operated by a uquid The operation of the system is as follows: For purposes of illustration it will be assumed that propane is the fuel being used. In this case it has been determined that the following conditions 20 were, in a particular installation, preferable for satisfactory operation; the limit control valve I0, II is set to open at a pressure of' 30 pounds per square inch to admit steam to the vaporizer 4 and close at 40 pounds per square inch, the dia- 25 phragm valve I2 is set to close at pressures below 25 pounds per square inch, opening again. at 35 pounds per square inch, and valves I4 and 2| are closed to eliminate tank car 22 and connecting lines from the system. The gas pres- 30 sure regulator 5 is set to deliver propane vapors to vapor line C at 10 pounds per square inch or at any other desired utilization presure. Valves 2, 3, I and I3 are open.

Assuming that the vaporizer is not in operation, 35

` i. e. there is a xvapor pressure in the storage tank in excess of 40 pounds per square inch, this pressure, being transmitted to the'limit control valve I0, II and preventing admittance of steam to the vaporizer, and that further the vaporizer 40 is lled to a predetermined level with liquid propane whereby the liquid level control 9 will operate to close valve 8, then, vapor is supplied to the gas pressure regulator solely from the top of the storage tank through vapor lines E and 45.l

As the storage tank I which is situated at a higher level than the vaporizer 4 and preferably of a dark color for heat absorption purposes cools, .due to changes in outslde'fatmospheric 50 temperature and latent heat of vaporization losses, there will be a corresponding pressure drop throughout the system on the upstream (high pressure) side of the gas pressure regulator 5.

As soon as the pressure falls to 30 pounds per 55 square inch in the system on the upstream side of the gas pressure regulator, the limit control valve IU, Il will open, admitting steam to the vaporizer. The admittance of steam, and subsequent vaporlzation of liquid propane in the vaporizer 4 will force the liquid level down and cause the liquid level control 9 to open valve 8 in vapor line B. When this occurs, artificially vaporized propane from the heat exchanger 4 will pass through vapor line B and join the vapors coming from the storage tank I through vapor line E If at this time, a large amount of vapor is being used, the pressure on the upstream side of the gas pressure regulator will continue to drop; when a pressure of pounds 'persquare inch is reached, the diaphragm valve I2 will close. At this stage, propane will pass only through liquid line A, vaporizer 4 and vapor line B to gas pressure regulator 5. The closing of diaphragm valve I2 will prevent further utilization of material vaporizing from the surface oi.' the liquid in the storage tank I and thus cause the pressure therein to slowly rise as heat is absorbed from the outside atmosphere. As soon as a pressure of pounds per square inch is reached anywhere in the system, diaphragm valve I2 will reopen and permit vapors from the top of the storage tank to join those coming from the vaporizer I. When the pressure increases to pounds per square inch, the limit control valve I0, II will shut the steam supply to the vaporizer 4 off, whereupon the liquid level of propane will rise to its predetermined maximum height and operate the liquid level control device 9 to close valve 8. At this stage, the starting point of the above description is again reached, i. e., propane vapor is being supplied from the top of the storage tank I only. 'Ihe 5 pound pressure ,differential between diaphragm valve I2' and limit control valve I0, I I is maintained to ensure a positive supply of vapors in the system under any operating conditions.

With the present arrangement it is also possible to rell the storage tank without interfering with the operation of the unit. This is accomplished in the following manner: Valves I4, I5, I1, I9 and 2| are opened and pump I 8 put into operation. Liquid propane will thus be pumped from the tank car 22 through line G to the storage tank I, while pressure in the system is equalzed by vapor line F connecting with vapor line B and indirectly with vapor line E.

It is to be understood that the above description is for illustrative purposes only, cer-tain obvious modifications being included within the scope of the invention, as for example a group of vaporizers may be supplied from a series of storage tanks and vaporized fuels fed to a pressure manifolding system rather than as in the simplified unit described. Obviously this valve could also be used to control other heating media than steam for thevaporizers, as for example gas flames, heated liquids or an electric current. Any

of the commonly utilized, normally gaseous fuels or mixtures of the same that may be satisfactorily stored in a liquid state under pressure may be substituted for propane. Other obvious and useful modifications will undoubtedly be apparent to those skilled in the art.

The advantages of present invention over existing units of this type are numerous, as for example the use of liquid regulators is entirely eliminated. Such regulators have in the past caused considerable trouble and annoyance due to their tendency to freeze when handling 10W boiling point materials. A further particular improvement is the economy of operation of the unit, the necessary heat input to the system being greatly reduced from that required in conventional vaporising systems. The present unit is inherently flexible enough in operation to meet any sudden and unusual demands placed upon it. Simplicity of construction and the safety features embodied are also factors that may be considered as distinct advantages.

I claim as my invention:

1. In apparatus for vaporizing liquefied gas of the class described, a vaporizer for liquefied gas, a storage tank for liquefied gas, an inlet liquid line for conducting liquefied gas, from said storage tank to said vaporizer, gas pressure regulating means, an outlet vapor line for conducting vapors from said vaporizer to said gas pressure regulatin'g means, a valve interposed in said last-named line, a liquid level control whereby the liquid level may be maintained within predetermined limits in said vaporizer, said liquid level control and said last-named valve being arranged and adapted to operate conjunctively, a-vapor line leading from the top of said storage tank to said previously mentioned vapor line, means for supplying heat to said vaporizer and pressure responsive means for controlling the flow of heat to said vaporizer incorporated in said apparatus on the upstream side of said gas pressure regulating means.

2. In apparatus for vaporizing liquefied gas of the class described and including a storage tank and vaporizer for liquefied gas, an inlet liquid line for conducting liquefied gas from said storage tank to said vaporizer, a rst vapor line leading from said vaporizer, a second vapor line leading from the top of said storage tank to said rst vapor line, a diaphragm valve in said second vapor line operable over a predetermined pressure range, means for supplying heat to said vaporizer, a limit control valve operable over a predetermined pressure range incorporated in said apparatus, said limit control valve being arranged and adapted to control the heat input to said vaporizer.

3. Apparatus according to claim 2 wherein a pressure differential operating range between the diaphragm valve and the limit control valve is maintained.

4. In apparatus for vaporizing liquefied gas of the character described, a vaporizer for liquefied gas, a storage tank for liquefied gas, said storage tank being so positioned that gravity flow of liquefied gas to said vaporizer will take place.

means for supplying heat to said vaporizer, gas

pressure regulating means, a liquid inlet line from said storage tank to said vaporizer, a vapor outlet line from said vaporizer to said gas pressure regulating means, liquid level controlling means including a valve in said l-ast-named line whereby the liquid level may be maintained within predetermined limits in said vaporizer, a' vapor line leading from the top of-v said storage tank to said first-named vapor line, a diaphragm valve operable over a predetermined pressure range located in said last-named vapor line and a limit control valve located in the top of said vaporizer, operable over a predetermined pressure range and arranged and adapted to control the heat input to said vaporizer.y

5. Apparatus according to claim 4 wherein the upper limit of operation of the diaphragm valve is lower than the upper limit of the operating pressure range of the limit control valve and higher than the lower limit of the operating pressure range of said limit control valve.

veying vapors from said source of liqueiied gas supply to said rst line, means automatically responsive over a given pressure range of said apparatus for controlling the heat input to said vaporizer, means for maintaining a liquid level within predetermined limits in said vaporizer and a pressure responsive diaphragm valve. in said 5 second line operable over a gven'pressure range.

WALTERH. HOAGLAND.

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