US 2522026 A
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Sept. 12, 1950 E. w. EVANS 2,522,026
APPARATUS FOR VAPORIZING LIQUEFIED GAS Filed Dec. 26, 1945 LPG VAPOR O 00 n 9006 L\\\\\\\\\\\\\\\\\\\ INVENTOR. E. W. E VA N 5 "www ATTORNEYS Patented Sept." 12, 1950 APPARATUS FOR VIRIZING LIQUEFIED Edmond W. Evans, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Application December 26, 1945, Serial No. 637,279
8 Claims. 1
This invention relates to evaporators. In one of its more specific aspects it relates to evaporators for use in the evaporation of liquefied normally gaseous materials. My evaporator has special utility in the liquefied petroleum gas field and in many installations relatively large quantities of such material need to be transformed from the liquid state to the gaseous state. Such hydrocarbons as propane or butane are compressed and liquefied and transported and stored in the liquefied condition. Then prior to use of the hydrocarbon as fuel, it must be vaporized. It is in this vaporization step that my particular evaporator finds special utility.
Further, such hydrocarbon gases are usually processed and handled in a dry condition, that is, substantially free from moisture. Public utilities distributing propane, either in the diluted or undiluted form, complain that because propane as conventionally vaporized is extremely dry, and because their metering and rate schedules are based on a water saturated gas, there is a loss of about 3% in volume. To state the problem conversely, the consumer receives a dry gas whereas the B. t. u. requirements are based upon a water saturated gas. r
Such public utilities frequently have occasion to vaporize these liquefied hydrocarbons at rather rapid rates and under such conditions heat exchange problems may be acute. Vaporization of liquids is, of course, endothermic. For a conventional evaporator or heat exchanger there is a definite limitation on the rate of heat transfer through metal tubes. A further limitation exists on the rate of heattransfer through metal tubes due to the formation of an insulating iilm of vapor adjacent exchanger tube surfaces when certain temperature diierentials are exceeded.
An object of my invention is to provide an evaporator which overcomes the above mentioned difficulties.
Another object of my invention is to provide a liquefied gas evaporator which is capable of evaporating such liquid at high rates.
Still another object of my invention is to provide a liquefied petroleum gas evaporator which is adapted to the evaporation of such liquids at high rates and at the same time is adapted to moistening the gases for metering purposes.
Still other objects and advantages will be apparent to those skilled in the art from a careful study of the following disclosure and the attached drawing which respectively describes and illustrates a preferred embodiment of my invention.
The drawing illustrates in sectional elevation a preferred form of my apparatus.
Referring now to the figure of the drawing, a liquefied gas from a source, not shown, and dowing through a line I and a pressure reducing valve 2, enters my evaporator by way of an inlet line 3. The evaporator body is merely a cylindrical tank 4, vertically disposed and about half filled with water 6. The liquefied gas inlet tube 3 extends into the lower portion of the tank some llttle distance so that liquid entering the tank may be discharged well into the body of the water.
`Steam from a source, not shown, and flowing through a line 6 passes a ilow control valvel and enters the tan through an inlet line l. The steam, also, is p eferably discharged well into the body of the water and at a point more or less near the inlet point of and substantially countercurrent to the iiow of liquid from conduit 3. To prevent overheating or underheating of the water, a temperature responsive device t is inserted into the body of water as shown. A connection from this temperature responsive device connects with the motor valve 'l for controlling the now of steam. This device is so operated that as the water in the vessel becomes cooled to below a certain predetermined temperature more steam is admitted through valve 1. In case the water becomes too warm or is heated to a temperature higher than a predetermined value. the temperature responsive device operates to throttle or to close oif the flow of steam. Such a condition as the latter might exist at times when the ow of liquefied gas to be evaporated stops for one reason or another.
An outlet pipe Il is provided for removing excess water from the vessel at times when condensation of steam to water is more rapid than the evaporation of the water into the vaporized gas. A liquid level controller Il is responsive to the level of the water within the vessel and functions to open or to close a motor valve I2 in the water line Il. This assembly is so acliusted that when the water level reaches a certain maximum height the oat controller I I operates to open the motor valve I2 and permit water to flow in the direction indicated by the arrow since the pressure within the vessel is at all times greater than atmospheric. In like manner when the waterslevel reaches a certain minimum stage the float II operates to close valve I2. As a second minimum level is reached controller II operates to open valve Il to admit additional water into the system through line Il, pump Il and line Il. As the desired water level withinV the tank is reached controller I I once more actuates valve I1 to close it.
At least several bailles Il are provided in the upper gas containing portion of the vessel to assist in preventing or at least minimizing entrainment oi' liquid in the vapors or gas passing out from the top of the vessel. A gas outlet line Il leads from the vaporizer tank above the bellies to a gas main, service lines. or other disposal or use, not shown.
In the operation of my apparatus and system as herein described, liquid propane, or other liqueiied petroleum gas, enters my evaporator by way of line I. pressure reducer 2 and inlet line I from such a source as a storage tank or transportation tank car, not shown. Liquid propane-has a vapor pressure of about 180 to 190 pounds per square inch at about 100 F., and in the summer season storage pressure may frequently approach this value or even exceed it depending upon the location of storage tanks. The liqueed gas at storage pressure then passes through the pressure reducer 2 in which pressure may be reduced to that necessary to force the gas through a gas main or even a network of gas mains, as in the case of a municipal distribution system. Such gas main pressures are comparatively low, as for example from a few pounds pressure up to as high as 10 to 20 or even 25 pounds per square inch. The exact value of a given gas main pressure for pressure reduction purposes through reducer is immaterial since the pressure reduction may be to any desired value.
Any pressure reduction in valve 2 will cause considerable cooling, and under some conditions it might be advisable to supply heat to the valve.
The liquefied gas then at a reduced pressure enters my evaporator through line 3 and the liquefied gas comes directly in contact with the warm water 5. By maintaining the temperature of the water at any desired value by the addition of steam from the steam inlet line 8, heat exchange directly from the warmed water to the evaporating liquefied petroleum gas is rapid and efcient. In order to maintain the water temperature at any optimum value, I use a temperature responsive device 9 which functions to open the steam valve 1 when the temperature of the water decreases below a predetermined value or to close the valve when the water temperature exceeds this value. Such a temperature controller may be set to control the temperature at any desired value. 'I'his type of equipment is standard and commercially available and its use is understood by those skilled in the art.
The desired operating temperature of the water is a result of several considerations. It is obvious that the higher the water temperature the more rapid will be the evaporation of the liquefied gas. A second consideration is the amount or relative proportion of water vapor desired to be added to the gas for metering purposes. The amount of water vapor carried by the evaporating gas is a direct function of temperature, the higher the temperature the faster is the rate of water evaporation. The specific temperature carried will probably be determined largely from the water vapor pressure consideration and the amount of water vapor desired to be added to the gas. The exact amount of water vapor to be added to a gas forms in reality no part of my invention since the water vapor will be added in each installation according to local conditions, and these may vary from place to place and even in one location from time to time. One important function of my apparatus is that I can add water vapors to the gas in substantially any desired amount by merely controlling the heat exchanger water temperature.
In my evaporator I accomplish a direct heat exchange between the water and the evaporating liquefied gas which type of exchange operation is very eillcient. Indirect heat exchange through metal is at best considerably slower than the direct exchanging as herein described. Other disadvantages of indirect exchanging have been hereinbefore mentioned. Under certain conditions, as for example, at summertime tempera-- tures, steam condensation may not provide suiiicient water to maintain a desired liquid level in tank 4, and water may need be added through a water inlet line I6, pump I8, and by the float controller H-valve I1 assembly.
The particular means as herein described for carrying out the heat exchange-evaporation process of my invention is not critical since varil ations and modifications may be made and yet employ direct heat transfer. For example, the water may be withdrawn from the evaporator tank and passed through a heating coil, then back to the tank again. In this case no steam condensate will increase the water volume as in my detailed example, and water will then need be added to maintain a constant level within the evaporator vessel. A float controller-motor valvewater pump assembly can be used. When the water level drops as indicated by the float, this latter opens a valve and starts a pump. Then as the water level increases to a predetermined value, the float operates to stop the pump and close the valve so the water will not back iiow in any manner.
A safety valve I5 of any desired type and adjustable to flow off at any desired pressure should be used for obvious reasons.
Still other means of heating the water may be employed, as for example, use of a steam coil in the bottom of the vessel 4, but even in this case the hot water is the medium for transferring heat to the vaporizing gas.
Apparatus and materials to be used in such an installation is standard and may be purchased on the market. No special equipment is needed.
From the above explanation it will be obvious to those skilled in the art that many variations and modifications of my preferred embodiment may be made and yet remain within the intended spirit and scope of my invention.
Having disclosed my invention, I claim:
1. A method for simultaneously vaporizing a liquefied petroleum gas and adding moisture to the extent of a maximum of approximately 3% by volume of the evaporated gas comprising passing the liquefied petroleum gas into direct heat exchange relation with steam and water at such a temperature as will evaporate the liquefied gas and will vaporize sufcient water to produce about 3% moisture in the vaporized petroleum gas; and removing the vaporized gas containing moisture as the product of the process.
2. A method for vaporizing and humidifying liquefied petroleum gas comprising passing the liquefied petroleum gas into direct heat exchange with water at a temperature to provide rapid evaporation of the gas; maintaining the temperature of said water by direct heat exchange with steam; and removing the evaporated gas.
3. An improved process for vaporizing a liquefied petroleum gas and controllably humidifying the resulting vapor in a confined vaporizing zone containing a body of water, which comprises the steps of continuously introducing into said body of water in the lower portion of said vaporizing zone a streamof liquefied petroleum gas; simultaneously and continuously introducing into said body of water in said zone a 'stream of steam in an amount suilicient 11o-provide latent heat for vaporizing said liqueiied petroleum gas and maintaining the temperature of said body of water and said vaporized hydrocarbon at such a point that eliluent vapors contain about 3% by volume of water vapor; andremoving from said body of water and vaporizing` zonev resulting vaporous troduction will4 be substantially counter-current to the Ilow of said petroleum gas stream',l a stream of steam in an amount suilicient to provide latent heat for vaporizing said liqueiied petroleum gas and maintaining the temperature of said body of water and said vaporized hydrocarbon at such a point that eilluent vapors contain about 3% by volume of water vapor; and removing from said body of water and vaporizing zone resulting humidied vapor.
5. An improved process for vaporizing liquid propane and controllably humidifying the re' sultin'g vaporous propane in a confined vapor-- izing zone containing a body of water, which comprises the steps of continuously introducing into said body of Water in the lower portion of said vaporizing zone -a stream of liquid propane; simultaneously and continuously introducing into said body of water in said zone, at a point substantially opposite the propane introduction point and in close enough proximity that the introduction will be substantially counter-current to said liquid propane streama stream of steam in an amount sufficient to provide latent heat for.r
Avaporizing said liquid propane and maintaining of water in said chamber; `a liqueed gas conduit protruding into said body of water in said chamber on substantially lthe same level as said steam conduit and to a point so that the outlet for said gas conduit is in relatively close proximity to the outlet of said steam conduit, whereby liqueiled gas and steam are emitted from their respective conduits into said body or water to rorm amix- 1 ture oi' gas and steam; control means responsive to temperature within said chamber; Ya valve in in said drain means operatively connected to said liquid levelI responsive control means;
means for introducing water into said chamber; a valve in said water introducing means operatively connected to said liquid level responsive control means; a gas outlet from the upper portion of said chamber; and means for reducing entrainment of liquid in the gas passing out of said chamber.
7. A liquefied gas vaporizer device comprising in combination a coniined chamber; a body of waterV in a substantial portion of said chamber; a steam conduit protruding substantially into said body of water in said chamber; a liqueed gas conduit also protruding into said body of water in said chamber; control means responsive to temperature within said chamber; a valve in said steam conduit regulating steam ow therethrough and operatively'connected to said temperature responsive control means; a pressure reducing valve in --said liquefied gas conduit; control means communicating with said chamber and responsive =to the liquid level therein; means for draining water fromsaid chamber; a valve in said drain means .for reducing entrainment of liquid in the gas passing out of said chamber.
8. A liqueed gas vaporizer device comprising in combination aconned chamber; a steam conduit protruding substantially -into the lower portion of` said chamber; a liquefied gas conduit protruding into said chamber from a direction other than that in which said steam conduit is maintained and on substantially the same level as said steam conduit, the outlets of said conduits being in relatively close proximity to one. another; control meansY responsive to temperature within said chamber; a valve in said steam conduit for regulating steam flow therethrough and operatively connected to said temperature responsive control means; a pressure reducing valve in said liqueiied gas'conduit; control means communicating with said chamber and responsive to liquid level with-V in said chamber; drain means in the lower p0rtion of said chamber; a valve in said drain means operatively connected to said liquid level responsive control means; liquid inlet means communicating with the lower portion 'of said chamber; a valve insaid liquid inlet means operatively connected t'o said liquid level responsive control means; a gaseoutlet in the upper portion of said chamber and baille members in the upper portion of said chamber and below said gas outlet therein.
EDMOND W.V EVANS.
REFERENCES CITED The following references are of record in the ille o1 this patent:
said steam conduit regulating steamiow therethrough and operatively connected to said temperature responsive control means; a pressure reducing valve in said liqueiied gas conduit; control means communicatingwith said chamber and responsive to the liquid level therein; means for draining water from said chamber; a valve Hoagland ...-----.-..Mar. 1l, `194:1