US3030780A - Refrigerated container for liquefied gases - Google Patents

Description

April 24, 1962 P. E. LOVEDAY REFRIGERATED CONTAINER FOR LIQUEFIED GASES Filed May 12, 1958 2 Sheets-Sheet 1 INVENTOR PAUL E. LOVEDAY ATT RNEY April 24, 1962 P. E. LOVEDAY 3,030,730

REFRIGERATED CONTAINER FOR LIQUEFIED GASES Filed May 12, 1958 2 Sheets-Sheet 2 H\\\\ I w L INVENTOR 'PAUL E. LOVEDAY M ATTO NEY Unite res 3,ti30,780 REFRIGERATED CUNTAINER non LHQUEFHED GASES This invention relates to improvements in containers for handling and storing low temperature commercial products, such as liquefied gases having boiling points below 233 K. at atmospheric pressure, and more particularly concerns containers for liquefied gases, such as oxygen, nitrogen or argon.

In the past, several difiiculties have been encountered in the delivery of low temperature, liquefied gas containers to small users who desire to use the gas in the gaseous state. One of the most important of these dlfficulties concerns the vaporization and loss of oxygen from liquid oxygen containers as a result of heat leakage such as might occur over periods of no demand or shutdown of the gaseous oxygen consuming operation.

For example, in the conventional double walled liquid oxygen container, the heat energy absorbed by the liquid oxygen as a result of heat leakage through the container walls is manifested by an increase in the temperature ofv the liquid oxygen body, and also an increase in the oxygen gas pressure corresponding to that increased temperature. In effect, this action creates excessive pressure conditions within the oxygen container which heretofore could only be alleviated by an oxygen release valve, with a consequent loss of gaseous oxygen to the atmosphere.

To the end that the above set forth difficulty may be avoided, there is provided herein an improved liquid container, wherein an auxiliary refrigeration conserving system is used in conjunction with the liquid oxygen storage system, and wherein the refrigerant used such system is eifective in attenuating any rise in temperature and pressure Within the oxygen container in a withdrawal schedule by absorbing heat directly from the liquid oxygen, as by the melting or vaporization of the refrigerant, within the range of liquid oxygen temperatures to be encountered during shut-down.

It is, therefore, an important object of the present invention to provide a container for valuable liquefied gas products, the container being capable of storing such products for comparatively long periods of no withdrawal from the container without loss of material through vaporization.

A further object of the present invention is to provide a novel container for holding liquefied gases, such as oxygen, argon or the like, and having an auxiliary refrigeration system so constructed and arranged as to decrease the rate of vaporization of the liquefied gas due to heat leakage, and consequently reduce the rate of increase in gas pressure in the container, thereby to elfect longer periods of storage of such liquefied gases with the development of only moderate pressures.

Still another object of the present invention is to provide equipment for warming liquid or gaseous oxygen issuing from the liquid oxygen container before it reaches its point of use, so that gaseous oxygen at a suitable temperature and pressure will be available for use.

Yet another object of the present invention is to provide a portable liquid container which is relatively light in weight and easily handled, small in size, and efiicient in operation.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of certain embodiments thereof taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a vertical sectional view of an exemplary container illustrating the principles and novel features of this invention;

FIG. 2 is a sectional view of the apparatus shown in FIG. 1 taken along the line 2-4;

FIG. 3 is a partial sectional view of a container similar to FIG. 1, but showing a modified auxiliary refrigeration compartment fill pipe;

FIG. 4 is a partial sectional view of a container similar to FIG. 1, but showing a modified inner vessel fill line; and

FIG. 5 is a sectional view similar to FIG. 1, but showing a modified cold converter or superheater unit construction.

In FIG. 1 is shown a gas material holding container or double Walled cylinder it) embodying features of the present invention. By the term gas material is meant a 'low temperature product, such as oxygen, in the solid,

liquid or gaseous state. The cylinder 10 may be of more or less conventional construction for stationary or portable use of the type having an elongated receptacle or inner pressure vessel 11 of impervious metal which is not embrittled at low temperatures, such as stainless steel, for holding liquefied gas material, preferably oxygen, and having normal liquid and gas spaces, L and G, therein. The inner vessel 11 is surrounded by a larger gas-tight shell or jacket 12 of suitable metal material, for example, carbon steel, completely encompassing the inner vessel, and providing an intervening evacuable insulating space 13 to provide substantial resistance to heat leakage therethrough. Any suitable means for supporting and centering the inner vessel 11 in the jacket 12 may be used, an example of one embodiment being illustrated in FIG. 1.

The jacket 12 includes a neck portion 14 which supports the inner vessel 11 by a vacuum sealing closure 15 constructed of metal, preferably of bronze or brass plate. The inner vessel 11 may be centered and held against side sway by means of a three legged support or tripod 16 having a central guide opening 17 for receiving theretlhrough a vertical pin 18 attached to the lower wall of the vessel 11.

The intervening space 13 may be evacuated by means of a vacuum pump (not shown) attached to a vacuum valve outlet 19 in the closure 15, or the space may be filled with thermal insulation through an opening in the jacket wall and capped by a metal sealing disc 26 made of brass, or the space may preferably be filled with a comminuted insulating material and evacuated to reduce heat leakage from the outside to the body of liquid oxygen in.

the vessel 11..

The absolute pressure within the intervening space 13 may be further reduced and maintained at a low value by attaching an adsorbent container 21 having therein a noncombustible adsorbent material, preferably silica gel, or a synthetic zeolite of the type described by Robert M. Milton in abandoned US. application Serial Number 400,385 filed December 24, 1953, and US. Patent Number 2,882,243 dated April 14, 1959; to the lower outer surface of the inner vessel 11 for removing air and water traces.

Means are provided for filling or replenishing the supply of liquid oxygen in the inner vessel, and for discharging liquid therefrom. As illustrated, such means comprise a suitable liquid phase pipe 22, controlled at its upper end by a fill valve 23. The pipe 22 preferably extends through suitable gas-tight openings in the closure and the inner vessel wall 11, and terminates in the liquid space L of the inner vessel 11 somewhat short of the lower wall thereof.

For the purpose of relieving any excessive gas pres sures that may develop in the inner vessel 11, a gas phase pressure relief pipe 24 formed of a metal possessing high strength and relatively low heat conductivity, such as stainless steel, in communication with the gas space G in the inner cylinder 11 is connected gas tightly through the upper wall of said vessel. This relief pipe projects upwardly through an appropriate gas-tight opening in the closure plate 15. The outer end of the relief pipe 24 terminates in a pressure relief valve 25, which may be preset to open when a specified pressure condition obtains in the vessel 11 to allow gaseous oxygen to escape into the atmosphere.

The inner vessel 11 is customarily filled with liquid oxygen to the proper liquid level to form the usual proportionate liquid and gas spaces L and G. To ascertain when the liquid body has reached the desired level, the inner vessel is provided with a small diameter vent or trycock line 26 constructed of stainless steel pipe or like material, and passing through gas-tight openings in the inner vessel 11 and the sealing plate 15. This trycock line 26 has a trycock valve 27 at its outer end for exposing the line to atmospheric pressure. The other end of the trycock line 26 communicates with the inside of the liquid oxygen vessel, preferably disposed with its lower end portion extending down into the normal gas space G, but terminating slightly below the normal liquid-gas line. Thus in the process of filling the inner vessel, as the liquid level reaches the lower end of the trycock line 26, the liquid oxygen will be forced upwardly into the trycock line by the oxygen vapor pressure within the gas space G, and escape into the atmosphere and through the open trycock valve 27.

This allows the operator or attendant sufficient time to shut off the supply of liquid oxygen, and stop the filling operation at approximately the desired liquid level.

As an alternative method of filling the inner vessel 11, the trycock line 26 may be replaced with suitable vent means, and the inner vessel filled by means of weight differential. Thus, by simply placing the cylinder to be filled on a preset scale balance and filling the cylinder until the scale balance indicates completion of the filling operation, a quick and convenient means for replenishing or filling the cylinder may be consummated. This method is preferred as it eliminates the trycock valve 27.

The modification shown in FIG. 4 shows a practical arrangement that might be used in filling the inner vessel 11 according to the weight differential method. In lieu of the trycock line 26 and relief pipe 24, the pipe 22 is constructed within a vent pipe 26 which functions in the capacity of a vent line. The pipe 22 extends into the liquid space L and reaches the bottom of the inner vessel 11, but the vent pipe 26 extends slightly into the gas space G at the top of the inner vessel 11. In charging the inner vessel 11, liquid oxygen is admitted through a charging connector line 27 into the pipe 22. A fill valve 23 in the charging connector line 27' controls the flow of supply liquid oxygen into the inner vessel 11, and a vent or relief valve 25' at the upper end of the vent pipe 26' allows vapors to escape as the vessel is being filled.

It is generally known that the loss of oxygen due to heat leakage from liquid cylinders of small capacity is an important factor to be considered in the distribution of liquid oxygen to small customers. Because of this, shutdown or no demand periods lasting two or three days will result in a rise in the temperature of the liquid oxygen confined in the liquid cylinder 11, a rise in the saturation pressure of the confined gaseous oxygen, and eventually escape of gaseous oxygen from the inner vessel 11 when the oxygen gas pressure reaches the preset relief pressure of the relief valve 25 (or 25).

In accordance with this invention, means are provided for absorbing the sensible heat increase in the stored liquid oxygen clue to heat leakage as rapidly at it enters the liquid oxygen, and thus retard the build-up of oxygen gas pressure to the extent that only moderate gas pressures will develop within the liquid cylinder over prolonged periods of non-use.

As a means for accomplishing this, I have provided an auxiliary refrigeration or heat storage system for conducting sensible heat away from the body of liquid oxygen and preventing, or to a considerable extent minimizing pressure build-up within the liquid cylinder over extended periods of no-demand. As shown in FIG. 1, an elongated refrigeration compartment 28 containing an auxiliary refrigerant is disposed in thermal association with the oxygen liquid and gas material confined therein and is preferably enclosed within the inner vessel 11 and immersed with the stored liquid oxygen L, but it is to be understood that the refrigeration compartment 28 could also be formed as an annular refrigeration jacket disposed around the inner vessel in spaced relation to the outer shell 12, or in any other suitable relation permitting temperature equilibrium directly between the liquid oxygen and the refrigerant. For example, the refrigerant vessel may be positioned adjacent the liquefied gas holding vessel and have a metallic heat conducting path or paths between the refrigerant and the liquefied gas.

The auxiliary refrigeration system may be of the evaporative type, or may constitute a closed refrigeration system, the former system being preferred and illustrated herein.

in a sealed refrigeration or heat storage system, it is desirable to use an auxiliary refrigerant having a reasonably low saturation pressure at ambient temperatures, so that it can be retained within its compartment without loss when it is warmed to the ambient temperature, a high latent heat of fusion or vaporization Within the saturation temperature range of 166 C. to l45 C. expected to be encountered by the liquid oxygen, and a high specific heat capacity in the aforementioned liquid oxygen temperature range. I have found the refrigerant dichlorodifluoromethane to be satisfactory, and suitable for use in the sealed auxiliary refrigeration system, since it has a melting point of l58 C., a saturation pressure of 130 p.s.i.g. at F., and an acceptable specific heat and heat of fusion.

It is to be understood that this invention is not limited to dichlorodifiuoromethane as the auxiliary refrigerant, and that the choice of refrigerant is determined by the expected temperature operating range of the inner container 11. i

As shown in FIG. 1, a connecting fill pipe 29, made of stainless steel or other suitable metal, is gas-tightly joined to an opening in the top of the refrigeration compartment, and extends outwardly through suitable gas-tight openings in the inner vessel 11 and the jacket closure plate 15. The refrigerant fill pipe line 29 outer end is connected to a sealing cap and bursting disk assembly 30.

The pipes 22 and 26 and the refrigeration compartment 28 are suitably braced against lateral movement within the inner cylinder 11 by one or more spider type reinforcement braces 31, two being illustrated in FIG. 1. The pipes 22, 24 and 29 also function as suspension supports for the inner vessel and contents.

It is almost always necessary to supply oxygen at superatmospheric pressure, such as 50-100 p.s.i.g., for customer consumption. To this end, the oxygen material from either the liquid phase line 22 or gas phase line 24 is passed through a conversion cycle apparatus which, when combined with the container, forms an apparatus known as a cold converter.

The conversion apparatus herein illustrated in FIG. 1 comprises a discharge line conduit 33, which forms a T- junction 34 with the liquid phase line 22 located below the fill valve 23. The discharge line 33 runs downwardly in the form of a horizontal helical coil or conduit 35, enwrapped around the outer surface of the jacket 12, or suitably coiled adjacent the inner wall surface of the jacket, the former being shown in FIG. 1 by Way of illustration, and the latter being depicted in FIG. 5. The latter is preferred to minimize the danger of helical coil breakage due to rough handling. The lower end of the helical conduit 35 then continues upwardly in a vertical run 36 having interposed near the end thereof a check valve 37, at the outer end of which is a service coupling 38.

The discharge lines 22, 33, 35 and 36 absorb heat from the atmosphere so that as the liquid oxygen passes there-.

through, it is evaporated and superheated and ready for delivery at the conditions required for withdrawal by the consumer.

Provision is made for selectively withdrawing gaseous oxygen from the inner container 11 into the helical conduit 35 to prevent excessive gas pressure build-up in said inner container. This is accomplished by a gas phase line 40 (FIG. 1) coupling the gas phase line 24 with the discharge line 33 at T- junctures 41 and 42 respectively. Interposed in the gas phase line 40 is a one-way back pressure valve 43 set at a predetermined pressure for example, open at 60 p.s.i.g. and close at 50 p.s.i.g. Thus, at all pressures above 60 p.s.i.g., withdrawal is gas phase to reduce inner container pressure, and at pressures below 50 p.s.i.g., withdrawal is liquid phase to prevent further reduction in inner container pressure In FIG. 4 is shown a cold converter apparatus substantially similar to that shown in FIG. 1, the only difference being in the specific manner of connection. Referring to FIG. 4, discharge conduit 33 forms a T-juncture 34 with the liquid phase line 22, and the gas phase line 40 is coupled to the vent line 26' by means of a cross connector 41. The liquid line 22 is brought out concentrically through the gas phase line 26' and through a sealing bushing of the cross 41. The relief valve 25 is connected to the remaining lateral branch of the cross.

In operation, the action taking place Within the container over a two or three day period of no Withdrawal of oxygen material is as follows:

Assume that withdrawal from the cylinder is stopped for a three-day period with the liquid oxygen L initially at 50 p.s.i.g. and a saturation temperature of 166 C. Since substantial thermal equilibrium exists, the dichlorodifluoromethane in the auxiliary refrigeration compartment 28 is also at l66 C. in the frozen state. As the sensible heat and pressure in the inner vessel 11 increase due to heat leak, the warming liquid oxygen transfers heat to the frozen refrigerant as sensisible heat at rising temperature. When the liquid oxygen and the dichlorodifluoromethane reach a temperature of about 158 C., the refrigerant starts to melt. The liquid oxygen and dichlorodifluoromethane then remain at the same temperature and pressure while the heat leak is absorbed as latent heat by the refrigerant until the latter is completely melted. The saturation pressure of oxygen at 158 C. is 95 p.s.i.g., which is appreciably lower than the oxygen relief valve setting. When the refrigerant has completely changed to liquid phase, the liquid oxygen and dichlorodifluoromethane temperature and pressures resume rising until the relief valve pressure is reached. Thus, it is readily seen that a sufiicient quantity of auxiliary refrigerant with high seat capacity and heat of fusion eifectively educes the build-up of oxygen gas pressure without loss of oxygen to the atmosphere which would otherwise occur during prolonged periods of no-demand.

It is to be noted that on resumption of gaseous oxygen withdrawal after a period of no withdrawal, the back pressure valve 43 is open to provide gas withdrawal from the gas space G so that pressure in the inner cylinder 11 is reduced, causing further liquid oxygen vaporization and corresponding cooling of the oxygen, which receives sensible heat from and cools the refrigerant, the refrigerant material now acting as a heat storage body for efiecting gasification of the oxygen which is required for the consumer. When the dichlorodifluoromethane temperature drops to about 158 C., the refrigerant starts refreezing, the temperature and pressures remaining constant during the refreezing period. On completion of the refreezing process, the dichlorodifluoromethane and oxygen temperature and pressures resume dropping until the oxygen reaches a set point at which back pressure valve 43 closes, and preferential liquid oxygen withdrawal commences, the temperature and pressures then remaining substantially constant. Thus, the auxiliary refrigerants capacity to further impede the increase in oxygen gas pressure over extended periods of non-withdrawal is restored.

It is to be understood that while I have illustrated and described a sealed auxiliary refrigeration system, the auxiliary compartment could also be adapted for use with an evaporative type refrigerant.

In such a situation, the compartment 28 of FIG. 3 may be filled with an evaporative type refrigerant, such as liquid oxygen, liquid nitrogen, or liquid air, and the bursting disk assembly 44 be replaced with a refrigerant relief valve 44'.

In the modification shown in FIG. 3, the pipe 29 is provided with a concentrically disposed valve controlled tube 29' for supplying refrigerant liquid to the compartment 28, and the pipe 29 is terminated at its upper end with a relief valve 44', as a means for venting the compartment as it is being filled, and for use as an automatic pressure releasing valve to maintain a desired pressure on the refrigerant liquid during operation.

By setting the refrigerant relief valve at a proper value, determined by the vapor pressure of the refrigerant at the maximum temperature of the liquefied gas product inthe inner vessel 11, heat transfer to the refrigerant in the compartment 28 as sensible heat builds up the refrigerant gas pressure therein, until the refrigerant relief Valve 44' begins to function. For example, in a liquid argon product-liquid nitrogen evaporative refrigerant system, the maximum argon pressure might be 225 p.s.i.g., as limited by the setting of the product relief valve. To insure release of the nitrogen refrigerant before the valuable argon product, the refrigerant relief valve might be set at a pressure corresponding to an argon pressure of 210 p.s.i.g. The corresponding argon saturation temperature is 148 C., this temperature corresponding to a nitrogen saturation pressure of approximately 445 p.s.i.g., which is the proper setting for the evaporative nitrogen refrigerant relief valve 44' (FIG. 3). Thus, upon the opening of the relief valve 44', the liquid nitrogen refrigerant would be evaporated and discharged to the atmosphere, and in so doing conduct heat at constant temperature away from the surrounding liquid argon body in the inner vessel 11.

A principal requirement of this invention is that the liquefied gas product be kept in thermal equilibrium with the auxiliary refrigerant. This requirement must be met regardless of whether the refrigerant is of the sealed type illustrated in FIG. 1, or the evaporative type illustrated in FIG. 3. While the refrigerant compartment 11 is shown in contactwith the liquefied gas product L, there are numerous types of heat exchange equipment which can be employed to effect temperature equilibrium between the product and refrigerant. For example, the product and refrigerant vessels could be adjacent each other and heat conducting paths of metal of high conductivity such as copper may connect the vessels. The heat conducting paths may also include metal fins or projections extending into the liquid to aid in maintaining temperature equilibrium between the product and the refrigerant.

When an evaporative refrigerant is used, the desired thermal equilibrium can be maintained usually by regulating the pressure in either or both the product and refrigerant compartments as determined by their relative thermal properties. For example, liquid argon product at p'.s.ig. can be kept in thermal equilibrium with vaporizing nitrogen refrigerant at about 28 p.s.ig. pressure, thus preventing vaporization and loss of costly argon by atmospheric heat leak. On the other hand, if the refrigerant has a moderately higher boiling point than the liquefied gas product at one atmosphere pressure, the pressure on the product may be maintained at a higher value than the pressure on the refrigerant such that the refrigerant is preferentially evaporated to absorb the heat leak.

Thus in an evaporative-type refrigeration system, a storage material such as liquid argon, oxygen, or deu- 'terium, may be provided with a consumable refrigerant comprising either liquid oxygen, nitrogen, air, or hydrogen. Normally, the storage material has a pressure of at least atomspheric pressure (0 p.s.i.g.). However, the refrigerant may have a pressure lower or higher than atmospheric pressure depending generally upon whether the refrigerant has a boiling point higher or lower than the boiling point of the stored material, respectively. To illustrate the conditions under which a material may be stored, the following Table I lists some of the pressures and temperatures that are approximately suitable in the storage of liquid argon, liquid oxygen, and liquid deuterium.

A Storage Material. B =Retrigerant.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

This application is a continuation-in-part of application Serial No. 455,194, filed September 10, 1954, now Patent No. 2,834,187.

What is claimed is:

l. A process for storing a low boiling liquefied gas material in a closed vessel and dispensing gas therefrom, the improvement comprising enclosing a body of a high latent heat capacity, phase changeable, consumable refrigerant material in a refrigerant compartment in thermal association with said liquefied gas material, insulating said gas material and said refrigerant compartment to impede the flow of external heat therein toward the liquefied gas and refrigerant matreial, maintaining the pressure in said closed vessel between a preselected lower working pressure and correspondingly lower working temperature and a preselected higher working pressure and correspondingly higher working temperature to produce a heat ballast effect whereby said refrigerant undergoes a phase change and acts to absorb sensible heat from said liquefied gas material during the period of storage, and undergoes a reverse phase change and acts to give off heat during the period of gas discharge, withdrawing gasified liquefied gas from said vessel when the pressure therein is above said preselected lower pressure, and'withdrawing liquefied gas from said vessel when the pressure therein is at said preselected lower pressure,

2. A system according to claim 1 in which said liquefied gas material is deuterium.

3. A process according to claim 1, said liquefied gas material being argon and said consumable refrigerant being nitrogen.

4. A process according to claim 1, said liquefied gas material being argon and said consumable refrigerant being oxygen.

5. A process according to claim 1, said liquefied gas material being argon and said consumable refrigerant being dichlorodifiuromethane.

6. A process according to claim 1, said liquefied gas material being oxygen and said consumable refrigerant being nitrogen.

7. A process according to claim 1, said liquefied gas material being argon and said consumable refrigerant being air.

8. In a system for storing liquefied gas material and dispensing gas material therefrom, the combination of a thermally insulated pressure vessel for holding a supply of liquefied gas, an evaporative-type auxiliary refrigeration system within said vessel in thermally conductive relation to the body of liquefied gas material contained within said vessel and including a refrigeration compartment immersed in the liquefied gas body having therein a confined body of consumable liquefied gas refrigerant, and an apparatus for dispensing gas material from said pressure vessel, said insulated pressure vessel comprising an inner vessel, a larger outer vessel encompassing and supporting said inner vessel, and defining an intervening evacuable space therebetween for the prevention of heat leakage therethrough, means for filling said space with insulation material, a gas-tight vacuum connection in said outer vessel wall for evacuating said intervening space, adsorbent material in said intervening space for effecting efficient vacuum conditions therein, and sway prevention means for centering and holding said inner vessel in spaced concentric relation to said outer vessel.

9. A process for storing a low boiling liquefied gas material and dispensing gas therefrom, comprising storing a supply of such liquefied gas in a closed, insulated vessel, enclosing a body of a high latent heat capacity consumable refrigerant in a refrigerant compartment disposed in thermal association with said supply of liquefied gas, insulating said vessel and refrigerant compartment to impede the flow of external heat therein toward the supply of liquefied gas and refrigerant, absorbing into said refrigerant heat leakage into said vessel, withdrawing liquefied gas from said vessel as required for use when the pressure therein is below a preselected operating pressure, selectively withdrawing gasified liquefied gas from said vessel when the gas pressure within said vessel exceeds said preselected operating pressure, recooling and thereby regenerating the refrigerating capacity of the remaining refrigerant while said gasified liquefied gas is being withdrawn to prolong the period of gas withdrawal from said vessel and when said withdrawal is interrupted, maintaining said refrigerant under pressure condition such that heat inflow through the insulation is absorbed by the refrigerant for a substantial period of time before the temperature of said liquefied gas is raised to the equilibrium temperature thereof, corresponding to a predetermined maximum pressure within said vessel.

10. In a system for storing liquefied gas material, a vessel having normal liquid and gas spaces therein for holding a supply of liquefied gas, a heat insulating jacket surrounding said vessel and defining a space therebetween, a refrigeration compartment in thermal association with the body of liquid in said vessel, said compartment including a consumable refrigerant having a high heat capacity for absorbing sensible heat from said body of liquid, a gas phase line connection from said vessel and communicating with said gas space a liquid phase line connection from said vessel, and communicating with said liquid space, said gas phase line having at its outer end a pressure relief valve, said liquid phase References Cited in the file of this patent 33111 2351 5iiiii fii l fia iigiififi iii fid ai ai UNITED STATES PATENTS phase lines, a back pressure valve interposed in said con- 1680873 Lucas'Girardvine {@115 1928 necting line, a superheater coil joined to said liquid phase 5 211Af8109 Dana et a1 211 1939 and said gas phase lines, and disposed adjacent said heat 7 Bfown ,1940 insulating jacket, means for reducing heat leakage be- 2,269,172 Blrdsau 1942 tween said vessel and said jacket, and means for holding 2,396,459 1946 said jacket, vessel and compartment in assembled rela- 2,460,765 Palalth 1949 tion 10 2,463,098 Godard Mar. 1, 1949

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