US2035399A

US2035399A - Cascade system and method of operating the same

Info

Publication number: US2035399A
Application number: US752993A
Authority: US
Inventors: John J Murphy
Original assignee: Linde Air Products Co
Current assignee: Linde Air Products Co
Priority date: 1934-11-14
Filing date: 1934-11-14
Publication date: 1936-03-24
Anticipated expiration: 1953-03-24

Description

March 24, 1936. J. J. MURPHY 2,035,399

CASCADE SYSTEM AND METHOD 0? OPERATING THE SAME Filed Nov. 14, 1954 4 Sheets-Sheet l Z I NTOR M AT g EY3 March 24, 1936. J. J. MURPHY 2,035,399

CASCADE SYSTEM AND METHOD OF OPERATING THE SAME Filed. Nov. 14, 1934 4 Sheets-Sheet 2 March 24, 1936. J, J, MURPHY. 2,035,399

cgscws sism'm AND METBOD OF- orzauine THE SAME I I Filed Nov; 14; 1934 4 Sheets- Sheet :5

XNVENTOR wmnw f ggy March 1936. J. J. MURPHY 2,035,399

CASCADE SYSTEM AND METHOD OF OPERATING THE SAME Filed Nov. 14, 1934 Y 4 Sheets-Sheet 4 INVENTOR ATTORNEY5 Patented Mar.v 24, 1936 PATENT orgies CASCADE SYSTEM AND METHOD OF OPERATING THE SAME John J. Murphy, Mount Vernon, N. Y., assignor to The Linde Air Products Company, New York,

N. Y., a corporation of Ohio Application November 14', 1934, Serial No. 152,993

47 Claims.

This invention relates to a method and apparatus for transferring a volatile liquid, that has been produced at some expense and evolves a gas phaseduring transfer, from a regionof rela tively low pressure to a region of relatively high pressure with a relatively small evaporation loss of the material.

More specifically, the invention relates to a system of vessels and method of operation whereby charges of precious liquid material, that is highly volatile at normal atmospheric pressure, for example, a liquefied gas, such as certain liquefied hydrocarbons, liquid oxygen, liquid nitrogen, and the like, are economically and expeditiously transferred from a supply vessel at a relatively low pressure to a receiving vessel at a relatively high pressure, in a manner which induces substantial recondensation of gas phase into liquid within the transfer apparatus so as to augment the net amount of liquid transferred.

The invention has for its object generally the provision of an improved system and arrangement of vessels, together with a method of operation, for transferring successive charges of relatively cold liquid material of the character indicated from a supply vessel at a relatively low pressure to a final vessel at a relatively high pressure in a manner which preserves the con: densing capacity of the liquid at a high value and uses it to reconvert a major portion of gas phase into liquid thereby reducing the losses when, venting the'gas phase, to an extent which is commercially important.

More specifically, the invention has for its object the provision of a system of transfer vessels, together with a cycle of operating events therefor for effecting the transfer of a volatile liquid, in a succession of uniform charges, from a supply vessel to a receiving vessel through a plurality of stages of increasing pressure environment while the gas phase is passed countercurrentwise; the transfer being effected in a manner which provides condensing capacity in-a series of increments in order that the refrigeration of the liquid phase with respect to the gas phase may be utilized with a high practical efficiency for the purpose of effecting a very large amount of condensation of residual gas phase into the liquid phase whereby losses from the gas'phase when venting an initial transfer vessel may be reduced to substantially airy low value desired.

It is also an object to effect the desired transfer'of charges'of such material in a manner which effectively excludes substantially all heat of external origin from the material beingtrau's- 10 It 18 afurther ob ect to provide a system of transfer vessels, and cycle of operation, adapted for effecting the rapid transfer of liquefied gases intended for industrial consumption, notably liquid oxygen, from a transport container, which 15 is at a relatively low pressure, to areceiving device, such as a vaporizer or storage receptacle, at a relatively high pressure in order that industrial consumers may be quickly serviced in a manner which reduces the so-called blow-down to the atmosphere to a negligible value and permits the economical delivery of either liquid or gas at widely separated points in varying amounts with ease and dispatch.

Other" objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

85 For a fuller understanding of the nature and objects of theinvention reference should be had to the following detailed description taken in connection with the accompanying drawings in which: I

Fig. l-is a view partly in section and partly in elevation showing an embodiment of the invention upon a vehicle and adapted for commercially transporting a liquefied gas, such as liquid oxygen, and transferring the same means of what is herein termed cascade connected vessels to a transportable vaporizer for the servicing of industrial consumers with oxygen Fig. 2 is a view partly in section and partly in 50 elevation showing a simple system comprising vessels connected in cascade for transferring a liquefied gas in accordance with the invention;

Fig. 3 is a similar view showing a more elaborate system of vessels connected to embody the predetermined point, such as This exclusion is 5 cascade principle in accordance with the invention;

Fig. 4 is a similar view showing a still more elaborate system of vessels, part of which are connected in series and part in parallelfor transferring a liquefied gas in accordance with the invention;

Fig. 5 is a view partly in elevation and partly in section showing still another system comprising vessels, connected partly in'series and partly in parallel, embodying the cascade principle and adapted for rapidly effecting a transfer of liquefied gas in accordance with the invention; and

Figs. 6 and '7 are explanatory dfiigrams.

Heretofore, it has been proposed to transfer liquid material of low volatility that is practically stable at normal atmospheric temperature and pressure, from regions of low pressure to regions of high pressure by means of vessels interconnected in a manner capable of imposing successively increased pressures, somewhat analogous to the use of locks in ship canals connecting different water levels. Such prior arrangements, however, neither encountered nor solved the problems met by the present invention.

By the present invention a system of constant volume transfer vessels and a cycle of operating events for effecting communication therebetween are provided by which substantially uniform charges of liquid are subjected to a succession of increased pressures until passed to the desired high pressure, the gas phase occurring in the vessels being passed counterwise in a heat exchanging relation with the liquid and subjected to a reversed succession of pressures so that a substantial portion of the gas phase is recondensed into liquid at each of the successively lower pressures. The number of stages employed is preferably such as to utilize the total condensing capacity of the liquid to as large an extent as practical; the condensation increments to the transferred liquid being effected to a point where the material in the gas phase in an initial vessel which is blown-down to the atmosphere is reduced to a value that is practically negligible. A system of communicable vessels which receives charges of liquid and effects the countercurrent passage of such material in the gas and'liquid phases 'by stages in a manner such that the liquid phase passes from a region of low pressure to a region of high pressure, for brevity, is termed a cascade system.

The exclusion of heat from the cascade system of the present invention is preferably ace complished, in the first instance, by providing means associated with the transfer vessels for insulating the vessels against heat from outside the system. Any suitable heat insulating agent -may be employed for this purpose, for example,

an envelope of magnesium carbonate.

'There is, of course, a certain amount of heat that may be additionally communicated to the liquid from parts of the system, such as that remaining in the walls of the transfer 'vessels,

due to their heat capacity, and retained after each passage of gas and equilization of pressure. Such heat is communicable-to the next liquid charge entering the vessel, since the walls are heated by the gas phase and are at a temperature slightly above the temperature of the next charge. To exclude substantially the entry of this heat into the liquid, when thus admitted, the heat capacity of the liquid holding means is made relatively small. This is preferably accomplished by providing thetransfer vessels, or a desired portion of them, with linings of a character that substantially retard the conduction of heat between the vessel walls and contents; a preferred form comprises thin-metal receptacles or baskets which have relatively little mass and a low specific heat and make contact with and hold the liquid. Such a'basket is preferably shaped to conform to the interior of the vessel and is supported in spaced relation to the interior walls by means of spacers having relatively poor heat conductivity. 'A suitable construction of vessels, basket and spacing means is taught in U. 5. Letters Patent No. 1,948,477, issued February 20, 1934 in the name of Zenner. The piping used to connect the vessels here employed may be similarly lined when desired.

The exclusion of heat, as here proposed, is important in effecting the transfer of volatile liquids of the character indicated by reason of the relatively large temperature differences encountered and the generally small latent heats of the materials that are vaporized. Otherwise, heat entering from the exterior and that communicable from the parts of the system may produce undue evolution of a gas phase during the transfer effected. Liquid oxygen has a very small latent heat which becomes smaller as the critical pressure is approached. Hence, it is seen that it is desirable to make the heat exclusion here practiced the more rigorous for the vessels which are associated with the higher pressures. Where the pressures are low, 'i. e., in the neighborhood of a few atmospheres, or where transferring certain liquefied hydrocarbons, the use of baskets may be dispensed with.

The exclusion of heat here practiced preserves the condensing capacity of the liquid in addition to the reduction in mass of the gas phase evolved. The refrigeration of the liquid is thus preserved in a highly eflicient manner so that a very large amount of condensate results which is added to the liquid phase transferred.

It will also be seen that a liquefied gas such as liquid oxygen contains a store of so-called available energy due to its low temperature and 4 high density. .This available energy can be utilized in a suitable apparatus to cause self-compression of the fluid from a liquid at low pres- I sure to a gas at high' pressure, and deliver it to a suitable point outside the system. This is effected, it will be noted, without input of additional energy other than heat from the environ ment, such as that from the surrounding atmmphere, and without appreciable loss of material. It is proposed, however, to introduce heat controllably' when desired to accomplish the ultimate conversion into gas. This is done when the material being transferred reaches a predetermined point, for example, a vaporizer. It may be done, however, at other points particularly in a vessel in which the material passes through the critical temperature and pressure. At such pressures, transfer under the operative forces of a system which depends on difference in densities, becomes relatively ineffective. To this end, it is contemplated providing such transfer vessel with means for controllably introducing heat. 1

The essential nature of the present cascade system may be ascertained from the simple system indicated in Fig. 2. Here, a pair of interconnected transfer vessels 4; and b, that are shown as lined and provided with heat insulating envelopes, is arranged for effecting a transfer ofcharges of the characterindicated in two stages from a supply vessel 0, which serves as a source at a relatively low pressure, to a re ceiving vessel, here shown as a vaporizer d, to which the controlled supply of heat energy is applied for converting the material into gas at a desired high pressure. While the transfer vessels a and b are arranged for passing the charges of the material being transferred through each vessel successively, and are hence termed a series arrangement, it-is also contemplated using an arrangement in which the material passes through a transfer vessel but once, the material from being fed into the'vessels alternately. Such an arrangement is termed a parallel arrangement. It is also contemplated using vessels connected partly in series and partly in parallel in systems using three or more vessels.

In the arrangement shown in Fig. 2, a predetermined quantity of liquid, comprising a charge, is caused to pass through an inlet conduit l0 into initial vessel 0. under the influence of a force, such as that had from pressure operative in the system, when admitted'by the opening of control valve II. To admit the charge, the gas in vessel a is displaced. This is arranged to take place through an outlet, or blow-down conduit l2 that is controlled by a valve l3. This conduit, when open, permits gas to discharge directly to the atmosphere, while liquid enters through conduit it. To admit a substantially uniform quantity 'of liquid at each charge, a metering device is associated with vessel a so that-flow is stopped when a desired quantity of liquid has entered. Any suitable metering device may be employed to this end, for example, a liquid. level operated seal for conduit I 2 which automatically closes the same when the desired quantity has entered. In the arrangement here illustrated, this is accomplished byextending conduit H, as shown at H, into the vessel a so that the mouth is at the liquid level attained when the desired quantity has entered. The fiow of liquid from vessel 0 is arrested as soon as the predetermined level, shown by liquid rising in conduit i2, is attained in vessel a. The material thus admitted to vessel a expands" when warmed by heat exchanged with the gas phase. Consequently, the

proper filling of vessel (1 is determined by the character of the liquid being transferred, as it is desired to have a gas space in vessel a sufficient to permit such expansion to take place without overflowing the lining or basket. The blow-down of residual gas from vessel 0. here contemplated, need only reduce the pressure P of vessel a sufficiently below that in vessel 0 to accomplish the desired flow.

When it is desired to transfer the material from vessel. a. to vessel b, the valve M in connection i5 is opened to permit at first a flow of gas that may have remained in vessel b, as a residue of a previous operation, into the charge of liquid in vessel 11. Heat exchange by direct contact occurs between the gas and the liquid whereby a portion of the gas is condensed while the temperature of the liquid is elevated and there is finally reached an equilibrium condition of pressure and temperature which is above the original conditions of the charge of liquid and which is below the pressure originally in vessel b. Liquid is thereupon discharged from vessel a to vessel b by utilizing the force of gravity. This flow is facilitated by providing the gas communication conduit l6 controlled by valve II, which when opened permits the displacement of gas from vessel b to vessel :1 by the liquid that flows from vessel 11 to vessel 2). The volume of vessel b may not be the same as vessel a; for example, it may be larger, in order to provide a gas and liquid space therein which will accommodate therein by reason of the condensing capacity thereof, with resulting condensation from the gas phase into the liquid phase. There is, in consequence, a redistribution of the internal energy in the system comprising vessels 0. and b without a substantial change in the total internal energy of the system since heat of external origin is rigorously excluded and no external work is done. This series of operative events may therefore be ideally termed an adiabatic equalization of pressure, although in practice there may be some heat leakage into the system.

The charge of liquid, now in vessel b, is dis- I charged to the vaporizing vessel (1 which is shown as a coil of tubing disposed within a casing 24 and exposed to a heating medium circulating through the casing. The discharge is eflected by utilizing a force of external origin such as the force of gravitywhen the valve i8 controlling the discharge conduit l9 leading into the vaporizer is opened and the gas pressures equalized by opening valve in conduit 2!. Liquid-moving forces of external origin other than the force of gravity may also be utilized as will appear from the description of Figs. 3.and 4.

Liquid which flows into the vaporizer d is vaporized ,by heat supplied thereto and the pressure in the system comprising vessels b and it rises toa desired relatively high value. A desired quantity of the gas so produced is discharged to storage receivers and/or consuming apparatus which are coupled to the system at e by flow through the conduit 22 when valve 23 is opened. The heat which builds the pressure for efiecting the discharge is controllably supplied at vaporizer d and the major portion thereof is contained in the material discharged through conduit 22. However, a considerable amount of heat in the form of internal energy remains in the gas left in vessel b after the. discharge. It is this energy as well as the material containing it that may be returned to the liquid being transferred to any-desired extent by application 01' the cascade principle. In the example of Fig. 2, a. large portion of such energy is retained in the system by condensation of gas from vessel 1 i t a fresh charge of liquid in vessel a.

The actual discharge-from the system leaving at e is less in mass'than the mass of the charge supplied from the supply vessel by the mass of the blow-down, and, therefore, the net discharge represents the material passing through the eascade system in the direction from the initial to the final vessels while the net blow-down or netv loss represents the net material passing in the reverse direction in the system.

The principle of this operation may be more 'rious liquids have been and pressure lines.

tween vessels; as will appear from the detailed description of these figures given hereinafter.

' In the condensation here effected, the volumes of vessels a. and b (denoted below as m and vs) are of course constant. For purposes of analysis itisassumed that these condensations occur so quickly and that the vessels are so well insulated that no heat enters or leaves the material in. vessels a and b during the condensation process. Then for the system, comprising vessels a. and b, the first law of thermodynamics states:

. dQ=dU+dW (1) in which vlQ denotes heat added to the system from outside.

dU denotes changes of internal energy of the system.

dW denotes work done by the system'to the outside.

Now evidently dQ=0, and since the volume of the system is constant, dW=0, hence dU= which means that the change in internal energy of the system before and after the condensation is zero, or the internal energy remains constant. Internal energy of a gas is a function of the temperature only for a perfect gas but is also a function of the pressure for liquids and imperfect gases.

Let

m1 denote mass of liquid and gas invessel a,

m denote mass of gas in vessel b prior to the equalization flow,

w denote internal energy per vessel a,

unit mass in "and fl 4+mafla=Uk (a constant, giving the internal energy before and after mixing) (2) V ml+m =mo (a constant) (3) Since the gas or vapor condensed into the .a liquid is warmer and at a higher pressure than the liquid, heat is added to the liquid by condensing gas into it. Hence the pressure, temperature, mass and specific volume of the liquid will rise. It is theoretically possible to predict the final state of the liquid in a and the gas in b as a result of the condensation of the latter into the former. To do this, it is necessary to know the initial conditions, such as mass, "pressure and temperature of the gas and liquid, the volumes of the vessels, and the thermodynamic properties of liquid and gas, particularly the internal ener y as a function of pressure and temperature or volume. a

In general, thermodynamic diagrams for yaprepared which give a thermal quantity or quantities as a function of the so-called volumetric variables, 3:, t, and v. For example, in the temperature-entropy diagram, there are usually given constant total heat In the pressure-total heat chart, constant temperature and constant entropy lines are given. It is important to note that the functions entropy and total heat are'unique for any state of a substance. 7, For example, at any 'pressureand temperature, a given fluid has one and only one value for the entropy, or the total heat. Internal energy is also such a function which is defined by the state of the substance. If a substance is changed by any process from one state to another, the change in internal energy entropy, or total heat. is independent of the path and is a definite value. In the present discussion, the physical significance of these quantities does not enter. Mathematically, they are functions which are used to ascertain the conditions of pressure and temperature which result in a liquid phase when a gas phase is condensed into it under the conditions here imposed. It should be noted that internal energy is a fundamental concept whereas total heat and entropy are derived. For a perfect gas, the change in internal energy is equal to the specific heatat constant volume times the change in temperature, whereas the change in total heat-is equal to the specific heat at constant pressure times the change in temperature. In other words, internal energy is related to Cv exactly as total heat is to 09. Since the operations here practiced involve constant volume relations, the internal energy function is fundamental.

The reduction of blow-down loss from an initial transfer vessel by condensation in the next charge of liquid is an advantageous result accomplished by the use of the present cascade system. This is essentially a thermal process. As with most thermal processes, the physical limitations of the system are determined from heat and material balances. This balance for the present cascade system differs from that involving a steady flow where material of the same characteristics may be found flowing in the same direction at any instant of time, since the vessels in the cascade system are successively charged and discharged. The heat balance for the present system according to the first law of thermodynamics, from the above, gives the internal energy, Us, of the system as constant for the equalization step since there is no thermal or mechanical contact with the outside. For the mawrial respectively in vessels a and b, when passing from state (1) to state (2) Equation (2) above becomes t=mi i+mi i=mi i+mi i where m: is the mass of material in vessel a before the equalization and, aEis the internal en'- ergy per unit of mass in b, after the flow. The other terms use the symbols in like manner.

The matter balance, set forth in Equation (3) for the change of state in the two vessels, no ma- .terialentering from the outside, in likemanner ized and made to compress itself to gas at relatively high pressure without the input of energy other than heat from the surroundings; this being accomplished by the present method without appreciable loss of material.

In order to determine the available energy, re-' course is had to the second law of thermodynamics, remembering that the total heat. by definition, for any system is:

I=U+Apv (6) where I denotes total heat,

U denotes internal energy, and

possibilities and Am; denotes the work, in terms of heat units determined from the volume '0 through which a piston moves at a pressure p, A being the reciprocal of. the mechanical equivalent of heat. Then, by diiferentiating Equation (6) we have dI=dU+Apdv+Avdp (7) But by definition, from the first law of thermodynamics, as stated above, we have By the second law of thermodynamics and for a reversible process, this last expression is equal to the temperature (T) times the change in entropy (dS). By substitution we have The quantity Avdp is seen tobe positive for an increasing pressure.

The assumption of strictly reversible processes in accordance with the second law of thermodynamic's requires that heat exchanges here considered also be reversible. In order to achieve ultimate reversibility, all heat exchanges are here assumed to take place, under infinitesimal temperature difierences, at room temperature, To, (taken hereinafter as 20 C. or 293 K.). temperature for heat exchange is possible by assuming reversible adiabatic compressions or expansions as necessary to reach To. With this limitation the last term in Equation. (8) becomes hence TodS. Then by integrating both sides we have is seen to be the work of an ideal reversible compressor or expansion engine operating on continuous flow and supplied with a medium entering at state (1) and leaving at state (2).

-with one pound of gas at atmospheric pressure and 20 C. may be found, from tables now published. Equation (10), in terms of British thermal units, then becomes:

Similarly, the available energy of one pound of gaseous oxygen at 2000 psi. and 20 C., for example, is found to be 160.3 B. t. u./lb. This value is less than the available energy in one pound of liquid, and therefore, it follows that a reversible, frictionless apparatus could utilize the available energy in the liquid to produce 2000 psi. gas at 20 C., and at the same time deliver the excess available energy in the form of work. In' any practical apparatus, some losses are inevitable. That the value for available energy of 2000 psi. gaseous oxygen is lower than that of the liquid shows that an apparatus may be provided in which the available energy This Nega tive values for the integral show the amount of of liquid oxygen is largely'utilized to produce high pressure gaseous oxygen without doing external work or incurring substantial loss of material and requires only abstraction of heat from the surrounding atmosphere. tageous arrangements of apparatus which accomplish the abstraction and utilization of this heat are disclosed herein.

The energy transfer from vessel b to vessel (1' given above in Equation (4), is graphically represented in an illustrative flow diagram as depicted in Fig. 6. Here the energy originally in the material in vessel a is arbitrarily taken as substantially zero and is represented by the vertical line drawn downwardly at the upper left, and entering the system which is denoted by'the enclosing rectangle; movement of liquid being assumed downward While movement of gas is shown upward. The amount of heat or internal energy carried is denoted by the width of the streams. The stream] of liquid first receives a substantial increment of energy from the gas transferred from vessel b as shown by the stream g joining from the right. The uncontrolled input of heat due to heat leak, etc., is represented by the stream 72 entering the system from the left and joining, the downward stream. The controlled 'input of heat is represented by the large stream is entering from the left. At the bottom, the leaving of stream 1, representing internal energy of the discharge, is shown, which carries a major part of the heat energy that entered the system. Branching off from the downward stream to the right .within the system is shown a stream 111. representing the internal energy in the gas remaining in the'final vessel b after liquid discharge, and which flows upward when transferred to vessel a. The larger portion of the internal energy in the upward stream is transferred to the left to form stream 9 which joins the liquid stream 1, while the remainder escapes from the system with the blow-down as shown by the stream 11. issuing at the upper right. A

balance requires that the sum of all heat energy entering the system equal the sum of all heat energy leaving the system. That is:

The diagram of Fig. 7 similarly shows the mass balance of Equation (5) and the flow of materials in a two-step cascade system, liquid flowbeing downward and gas flow upward as before while the width of the stream indicates quantity by weight. The liquid stream enters at the upper left, the width p indicating the weight of a charge. The blow-down is represented by the stream leaving at the upper right having a width q indicating the weight of the gas blown down per charge. The weight of discharge is shown by the width 1' of the stream leaving at the bottom. The relation between these quantities is seen to be given by the following equation:

This equation simply states that the charge equals the net discharge plus the net blow-down. Within the system the upflowing gas stream represents the gas transferred to vessel a from vessel b, the portion flowing to the left to join theliquid stream being the portion condensed while the remainder flows out at the upper right as the blow-down.

In Fig. 1, there is shown a commercial application employing an arrangement of transfer vessels for applying the present method for the Various advanpurpose of effecting a transfer of liquid oxygen to industrial consuming apparatus. Here 25 represents the chassis of a motor vehicle which transports a supply vessel 0 holding a supply of liquid oxygen at a relatively low pressure that is to be delivered as gas to a consumer at a relatively high pressure. The vessel 0 is supported within an insulating casing 26 which protects the liquid from the inflow of undesired heat of the atmosphere. Adjacent to the vessel 0 is disposed a casing 21 which contains a cascade system of vessels arranged for effecting the transfer of liquid oxygen from the vessel 0 to a high pressure vaporizer d indicated as present on the truck within a casing .28 and having a discharge connection or exit 6 for servicing a customer. The casing 21 is made substantially airtight so that apparatus disposed within it may be protected from the influence of the heat of the atmosphere by evacuating the air from the casing or by filling the space not occupied by the apparatus with heat insulating material.

The system of vessels within the casing 21 may be any cascade system according to the present invention, for example, as shown in Figs. 2, 3, 4 or 5. Specifically, that intended to be shown as mounted on the truck in Fig. 1 is illustrated in Fig. 5. The liquid charging connection is shown at I0 in Fig. 1, leading from the bottom of the supply vessel 0, having therein a liquid measur ing device, indicated at l0. and passing into the top of an initial vessel, denoted 13, for the purpose of supplying metered charges of liquid oxygen at a relatively low pressure to the system.

The transfer of liquid oxygen from vessel 0 to the coils d is accomplished by first causing a flow of liquid through the connection ||l into such initial transfer vessel which operates at the lowest pressure level in the system. This flow may take place under the influence of a pressure built in the vessel c, which is relatively low, for example, five pounds per square inch gage, but exceeding that in the initial transfer vessel. The building of this pressure in the supply vessel may be accomplished in any suitable manner, for example, by means of an auxiliary evaporating coil,

such as 29, arranged as disclosed in Heylandt Patent Reissue No. 18,876, dated June 20, 1933. The transfer of liquid from supply vessel 0 into the coil d may be effected by any one of the cascade systems herein set forth in connection with descriptions of Figs. 2, 3, 4 and 5; the connection III for supplying liquid to the several series of vessels depicted being shown in each of the several figures. A cascade system, when thus arranged on a motor truck and utilized for delivering desired quantities of regasified material to consuming devices at various locations, has very low net operating losses in delivering gas at desired pressures.

In Fig. 3, a set of transfer pressure vessels 3|, 32 and 33 are shown, each connected to a common manifold of the liquid phase charging conduit I0,

through which liquid is supplied to each of the vessels 3 32 and 33. These three vessels are also connected to be vented through a common manifold by way of the escape conduit 30. A common withdrawal conduit 34 is provided communicating with each of the vessels for discharging the same, this conduit leading to the coils 35 of a high pressure vaporizer. In this arrangement,

the transfer vessels are hereinafter referred to While three vessels as connected in parallel. only have been shown, it is obvious that four or more could be employed.

In order to equalize the pressures and tempera tures in the vessels prior to discharging liquid, a conduit 36 is provided leading from the coils 35 and connected through a common manifold 36a to the gas space of each of the vessels 3|, 32 and 33, such connection being shown as afforded by the branch conduits 36', 36", 36. In conduit 36 there is interposed a means for mechanically assisting the flow of fluid therethrough which is here shown as a centrifugal blower 31 having its inlet at 38 and outlet at 39 being driven by an pendent conduit 4| connected by way of the branch conduit 4| with the lower end of vessel .3| and by way of the branch conduit 4|" with the lower end of vessel 32 and by means of the branch conduit 4|"' to the lower end of vessel 33. The connections to each of the vessels are preferably controlled by valves. Accordingly, the

communication of connection l0 with vessel 3| is shown as controlled by valve 42, while a valve 43 is shown as controlling the connection with the venting conduit 30. A valve 44' controls the outlet to withdrawal conduit 34, while valve 45' controls the branch connection 36' to conduit 36. A valve 46' controls the branch connection 4| leading to the conduit 4|, there being similar valves associated with the

vessels

32 and 33. A valve 41 is also shown controlling the exit e from the vaporizing coils.

In operation, the cycle of events may be assumed to start when the valves are closed, the vessels devoid of liquid but containing gas,.and the vaporizing coils full of gas at a relatively high pressure. To start the system, the vessels are filled successively with charges of liquid drawn from the conduit ID by opening the corresponding valves controlling the manifold connection, for example, vessel 3| is filled with a desired charge by opening valves 42' and 43'. The pressure in the vessel 3| is first equalized with that of an adjacent vessel that is full of gas, for example, with vessel 32, by opening

valves

46 and 46" which results in a pressure in vessels 3| and 32 that is intermediate that initially in vessel 3| and that in vessel 32 and a condensation of a part of the gas in vessel 32- into liquid in vessel 3|. When this first stage of equalization is accomplished, a second is effected at a somewhat higher pressure with another vessel, in this case with vessel 33 by opening valve 46" after valve 46" has been closed. When these intermediate equalizations are completed a final equallzation with coil 35 is effected by opening valve Thereafter, valve 46 is opened, and the blower 37 started which creates a pressure difference that results in accelerating the flow of liquid from the transfer vessel into the vaporizer. When all the liquid is discharged the vessel 3| will be filled with gas having a pressure equal to or slightly higher than that in the vaporizer.

The practice of thus efiecting the equalization in a plurality of stages prior to that finally attained before discharge, achieves a greater amount of condensate'from the gas phase than would otherwise be attained, since in each stage of the intermediate equalizations, a succession of pressures is applied, each making available further condensing capacity of the liquid, since each higher pressure applied to the liquid raises the boiling point and utilizes further the condensing capacity thereby utilizing the available energy of the liquid in a highly efllcient manner.

While vessel 3| is discharging, vessel 32 should be filling so that at the conclusion of the discharge it may be equalized first with vessel 33 vessels partly in series and partly in parallel is shown, whereby a relatively rapid discharge may be efiected and a relatively continuous operation of the vaporizer may be maintained. Here, 48 denotes a lined pressure vessel disposed above a second lined pressure vessel 49 and adapted to discharge liquid thereinto, there being two vessels 50 and 5| each communicatingwith a common liquid transfer manifold 52 leading. from the vessel 49. The thin metal linings of the vessels, such as basket 48' of vessel 48, substantially retards the flow of heat from the heavy walls of the pressure vessels into the liquid charges placed therein. Ventholes in the upper portion of the baskets provide pressure. equalization with the shell- -like space between the basket and pressure vessel walls. This space may be maintained by supporting the basket with strips of low heat conducting material, which enhances theheat insulating efiect desired and enables the transfer to take place under conditions approaching the ideal adiabatic conditions desired. These vessels also communicate at their lower ends with a common liquid discharge manifold 53, which leads to the vaporizer 54. A gaseous interconnecting means 55 between the vaporizer and the vessels 50 and 5| has branches 55' and 55 connecting respectively with the gas space of vessels 50 and 5|. An equalizing conduit 56 projects into the vessel 49 reaching nearly to the top thereof and has branches 55' and 56 communicating re-- leads from the upper portion of the vessel 48,

which is controlled by a valve 59.

A valve 60 is arranged in the conduit ID to control the inlet. A valve 6| controls the connection whereby vessel 48 discharges liquid into the vessel 49, a valve 62 controlling the connection 51. Valves 63"and 63" control the entrances respectively to the vessels 50 and 5| in the liquid discharge manifold 52. Similarly, valves 64' and 94" control the outlet branches to the withdrawal conduit 53. Valves B5 and 65" control respectively the communication of the branches 55' and 55" with the conduit 55.

Valves

65 and 66" similarly control the depending branches 56' and 56" of conduit 56 whichenter vessels 50 and 5|, respectively.

In order to condense gas from vessel 49 into liquid held in vessel 48 a conduit 6'! controlled by valve 68 is arranged to lead from the gas space of vessel 49 into the lower portion of the liquid uid, such as distributor 61 having a plurality of small openings therein. Such means effectsthe rapid and extensive condensation of gas passed between vessels; similar means being provided for efiecting cross-equalization between vessels 50 and 5| in the form of a distributor connecting conduit 69 having a control valve 10. This conduit interconnects the lower portions of the liquid spaces of both vessels when the valve I0 is opened.

Discharge of liquid through conduit 53 into vaporizer 54 is accelerated and effected against a head causedby the location of the vaporizer by means of a rotary pump H having its inlet connected to conduit53 and its discharge communicating with the vaporizer. The pump is mechanically driven by any desired means, such means being here shown as an electric motor 12.

I In operation, the cycle of events which takes place normally may be assumed to start when the coils 54 are full of gas at high pressure and the valves closed. Vessel 48 is filled by opening

valves

59 and 60 to admit a predetermined quantity of liquid, a desired gas space being preserved in the top of the vessel 48, .to avoid overflow of the basket 48' and allow for subsequent expansion. When filled, the valves are again 48 may be quickly dropped into vessel 49 by opening valves 6| and 62; after which the valves 6|,

62 and 68 are closed. Liquid may now be transferred from the vessel 49 to the vessel 50 by opening valve 63'. This isaccomplished by permitting gas at high pressure first to flow from the vessel 50 and bubble through the liquid in vessel 49 through conduit 52 until substantial equalization results, whereupon valve- 65' is opened to complete quickly the transfer of liquid to vessel 50. When vessel 50 is filled, valves 63 and66' are closed and valve Ill opened so that there is a stage of cross-equalization of the vessels 59 and 5| before filling of the latter takes place, a portion of the gas which remained in vessel 5| from a previous operation flowing through the conduit 69 into the liquid in vessel 50 to be partially condensed thereby. After closing valve 10, vessel 50 is discharged into 0011s 54 by opening valves 64 and 65' and starting the pump H which applies mechanical force sufficient to cause the material to flow against the head due to the elevation of the vaporizer. Valve '23 is opened when discharge to receiving apparatus occurs.

Dependent upon the rate of heat input, vessel 50 is ordinarily discharged relatively slowly to the vaporizer, so that vessel 48 can not only be recharged for the beginning of a new cycle, but the charge may be transferred to vessel 49 by repeating the steps described above. Upon the completion of the recharging of vessel 49, while the vessel 50 is still discharging, the vessel 5| may be filled. Accsrdingly, valve 63" is opened to accomplish gas condensation and substantial v equalization of pressures, whereupon valve 66" is opened and the transfer completed.

At this stage} vessel 59 is now empty of liquid, but full of gas at a relatively high pressure. Cross-equalization is thereupon efiected by opening valve ill, the flow-being now from vessel 50 into vessel 5|. When valve 10 is again closed,

the vessel 5| is now discharged to the coils 54 by opening valve 84" and valve 65" and operating the pump "II; the cycle being continued by the alternate recharging and discharging of vessels 50 and 5| and those associated with them as above described. In this manner, substantially continuous operation of the vaporizing device may be had.

In Fig. 5, a set is provided having vessels denoted 'I3', 13', I4, 14 and I5 respectively arranged partly in series and partly in parallel. The vessel 15 is here constructed to be of a different character from the first-named vessels,

in order that a certain amount of heat may be;

supplied to the contents thereof under certain conditions during discharge to the vaporizer as hereinafter more particularly pointed out. In the arrangement shown, the vessels l3 and '13" are connected in parallel through a common manifold to receive charges of liquid from the conduit ID. The vessel'l3' is arranged to discharge liquid under the force of gravity into vessel 14, which in turn is arranged to discharge into vessel I5. In a parallel manner, vessel 13" is arranged to discharge 'into vessel 14" which in turn discharges into vessel 15. Vessel I5 is thus seen to be a common vessel interposed between a heating coil I8 of vaporizerd and the two sets of series vessels 'I3'--'Il' and 'I3"-'I4". The vessels I8 and 13" are blown-down through a common manifold or conduit 11. The vaporizer d discharges through conduit I8 leading to exit e. Connections 80' and 80 convey the discharge respectively from vessels I3 and-13" into vessels I4 and 14". Similarly, connections 8| and 8|" discharge from the vessels I4 and 'l4" into the upper portion of vessel I5. Withdrawal conduit 82 leads from the lower portion of the vessel I5 to the coil 18. An equalizing connection 88 leads from an intermediate point in the coil. I8 and has branch connections 8|. and 85 leading respectively to manifolds communicating with vessels I3' I4' and with vessels I3"I4". interconnecting conduits are also provided for the cross-equalization of pressures between cor-- checl-rvalve 88 is preferably introduced in the conduit I8 to insure one-way fiowthroughtheconduit to exit 2. A connection 89 isalso provided leading from a point in conduit I8 beyond the valve88 to the upper portion of the vessel I5, a

valve 93 being arranged to control this latter connection. A by-pass is also preferably provided between conduits 83 and 89 as shown at IIII controlled by valve I02. Valves 9| and 92 control respectively the liquid inlet and venting connections of the vessel I3. A valve 93' controls the connection 80' and a valve 94' controls the connection. BI. A valve 95 controls the connection 82 to the vaporizing coil I8; Valve 98' controls the communication between the upper portions of vessels 1-3 and I4, while valve 91 controls the connection of the vessel I4 with the conduit 84. The cross-equalizing connection 85 is controlled by valve 98, while the cross-equalizing connection 81 is similarly controlled by valve 99. Valves 9|" and 82 are similar to valves 9| and-92' 'and control the inlet and venting connections of vessels 13", valves 93", 94", 96" and .91" being similarly located with respect to the vessels 13" and l8" and performing the same functions as valves 93', 94', 96' and 91', respectively.

In operation, the cycle of events whichnormally occurswill be assumed to start when the initial vessels are empty and the vaporizer d and vessel I5 are full of gas at a relatively high pressure. Before filling, the system is first purged of air by opening valves 96' and 91 and 9B" and 91", the. valves 96' and 96" being closed before the pressure has equalized in the coils I6 and the vessels I3, I4, T3" and 14'. When the system is thus made ready, liquid is introduced into the vessel I3 by opening valves SI and 92'. Instead of blowing down all of the gas in the vessel 13" by way of the conduit 11, the valve 98 -is first opened so as to permit the exit of some gas through the connection 86 from the vessel It" into the vessel I3 to be condensed in the liquid therein. By opening valve 93' gradually,

.gas in vessel I4 passes up through liquid in vessel I3, a portion condensing until the pressures equalize, after which liquid is passed directly from the vessel I3 into the vessel I4, the fiow being eifected by opening valve 96. This passage of liquid preferably takes place while vessel 13" is filling. Accordingly, as soon as valve 98 is closed, valves SI" and 92" are opened.

When the vessel I4 is filled and before filling of the vessel "I4" begins, cross-equalization is effected between these latter vessels, by closing valves 93' and 98 and opening valve 99 in the connection 81. When this equalization is completed and valve 99 closed, valves 94', 91' and I02 may be opened and an exchange of gas and .liquid takes place between the vessels I4 and I5,

the gas displaced flowing up through conduits IDI, 83 and 84. In this arrangement, the filling of vessel I4 from the vessel I3 and of vessel 18" from the connection I0 takes place substantially simultaneously. The opening of valve 94' accordingly is accompanied by an opening of valves 9| and 92' for refilling and blowing-down vessel I3 while the vessel 14" is at the same time filled from the vessel 13" by opening first valve 98" and finally valve 96".

Vessel I5 is, of course, filled from vessel 18' upon the completion of the above-filling step and after cross-equalization of the pressure in vessels I8 and "I4" has been effected by the opening of valve 99. Vessel I5 is thereupon discharged to coil 16 by opening valves 95 and I02. When the charge in the vessel I5 has been fully discharged, valves 95 and I02 are again closed and the vessel recharged from vessel 14'', to be ready for another discharge to the vaporizer.

From the arrangement shown, it is seen that I arate steps of condensation in the transfer of a charge of liquid either from the vessels I3 to 15 or from the vessels 13" to I5, the gas flow being countercurrent to the pressure increments on the liquid.

The thick-walled vessel I5 performs an additional function where the charge therein is to be discharged at or above the critical pressure.

-Where the heating coil I6 is supplying gas at a pressure materially above the critical pressure, for example, oxygen at 2100 lbs. per square inch gage, the material in the vessel 15 passes through the critical temperature before it is fully discharged through the valve 95. When the critical temperature is reached, flow under the influence of gravity becomes much impeded, since there is no sharp separation of phases. It is desired to force this gas material out of vessel 15 by causing it to expand dueto an increase of its temperature, which expansion may be efiected by suitably adding heat to the material in vessel 15, for example, by applying a heating medium, such as steam, in heat exchanging relation with the walls of vessel 15, by means of a conduit I disposed in thermal conducting relation with the wall of vessel 15. This causes the gas material in the vessel 15 to become heated with consequent expansion which forces the material rapidly out of the vessel. The normal flow through the valve 95 continues to the vaporizing coil which serves the purpose of heaters for raising the temperature of and superheating the gas. The check valve at 88 is seen to be a convenient means for preventing backflow from the line into the vaporizer d after initial equalization of pressure with that in vessel 15 takes place. The gas connection 89 serves to admit gas directly from the line to the vessel 15 when it is desired to withdraw liquid to supply the vaporizing coil immediately,

without waiting for pressure to build up to linedisplaced gas to a high degree by limiting the blow-down to a relatively low value while at the same time supplying vaporized liquefied gas to industrial consumers at pressures beyond the critical pressure, the servicing being effected in relatively short periods of time. Where the series of vessels are built in sufiiciently small units, the arrangement is readily adapted to be mounted and housed on a truck, as shown in Fig. l, for the servicing of industrial consumers, which may be at relatively great distances, from a central production plant. 1

The cascade system, according to the present invention, is also used in connection with stationary plants, for example, the servicing of consumin'g devices including a pipe lineconnecting several users withgas material under desired pressure from a low pressure storage container holding the liquefied gas and for filling containers at the liquefied gas production plant in which case the liquefied gas may be received directly from the production apparatus and gas vented from the initial vessel may be returned to the production apparatus for reliquefaction.

In cases where the liquid supply source is located above the initial transfer vessel, it .is contemplated that the gas vented from the initial vessel at the inception of a cycle may be conducted into the supply vessel to assist the flow of liquid.

Since certain changes in carrying out the above process and in the constructions set forth, which I embody the invention, may be made without departing from its scope, it is intendedthat all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent,is: l. A method of transferring a volatile liquid material, that has a gas phase evolved due to heat gained in the transfer, from a region of relatively low pressure to a region of relatively high pressure, which methodcomprises causing the passage of said material in a succession of metered charges in countercurrent relation to the gas phase, excluding substantially all heat of external origin from said material prior-to the passing of a predetermined point, and utilizing available energy of the liquid material to condense a portion of the gas phase whereby the ultimate loss of material in the gas phase is substantially reduced. v v

2. A method of transferring a volatile liquid material, that has a gas phase evolved due to heat gained in the transfer, from a region of relatively low pressure to a region of relatively high pressure, which method comprises causing the passage of said material in a succession of metered charges in countercurrent relation to the gas phase through a succession of stages of increased pressures, excluding substantially allheat of external origin from said material prior to the passage of a predetermined point, utilizing the successive increments of condensing capacity made available by increased pressure in said stages to condense a relatively large portion of said gas phase into the liquid phase, and augmenting the liquid phase being passed by adding thereto such condensate, whereby the internal energy of the gas phase is reduced substantially during its passage countercurrent to the advancement of the liquid.

3. A method of transferring a volatile liquid material that has a gas phase evolved due to heat gained in the transfer, from a region of relatively low pressure to a region of relatively high pressure from one vessel to another in cascade relation, which method comprises causing a succession of metered charges of liquid to pass under the influence of a gravity field from a vessel at a relatively low pressure into a vessel at a relatively high pressure while the gas phaseis displaced and passes counter thereto in heat exchanging relation therewith, converting a portion of said gas phase into the liquid phase and adding the same to the liquid transferred whereby the ultimate loss of material in the gas phase is substantially reduced.

4. A method of transferring a volatile liquid material that has a gas phase evolved due to heat gained in the transfer, from one vessel to another in cascade relation, which method comprises-introducing a metered charge of material inthe liquid phase into one vessel while another vessel contains material in the gas phase at a relatively high pressure, equalizing the pressures between said vessels'while effecting condensation of gas material, drawn from the high pressure vessel, at the expense of the available energy of the liq- .uid phase, then passing the liquid material into in the transfer from one vessel to another in cascade relation, which method comprises introducing a metered charge of material in the liquid phase into one vessel while another vessel contains material in the gas phase at a relatively high pressure, equalizing the pressures between said vessels while effecting condensation of gas material drawn from the high pressure vessel and passed into the low pressure vessel, and interchanging under the influence of gravity the liquid and gas phases between said vessels.

6. A method of transferring a liquefied gas of low boiling point which evolves a gas phase due to heat gained in the transfer from a supply vessel at a. relatively low pressure to a receiver at a relatively high pressure, which comprises effecting the passage of a metered charge of liquefied gas from the supply vessel in a cycle through regions of successively higher pressures until' the desired high pressure is obtained, effecting a counter passage of the material in the gas phase with the liquefied gas while passing from said low pressure to high pressure regions whereby condensation of a major portion of the gas phase is efiected, substantially excluding heat of external origin during said passage, and venting gas material in substantially reduced amounts from the region of low pressure at the inception of a cycle.

7. A method of forcing gas material, that is received in the liquid phase but has a gas phase evolved due to the addition of heat, into a receiving vessel byself-compression, which method comprises segregating bodies of liquefied gas, forcing a desired portion of one ofsaidbodies into said receiving vessel by displacing the body of liquefied gas with gas having a relatively high pressure, generating said displacing gas by passing at least a portion of another body of liquefied'gas in thermal contact with a source of heat through the action of force of external origin, and distributing the internal energy of the gas used for effecting displacement among a plurality of other segregated bodies ofliquefied gas previous to displacing said bodies into said receivers whereby the available energy of the liquid phase is used to recover a portion of the material in the gas phase.

8. A method of forcing gas material, that is received in the liquid phase but has a gas evolved due to the addition of heat, into a receiving vessel by self-compression, which method comprises providing a segregated body of liquefied gas, causing desired portions ofsaid body to traverse successive stages of increasing pressure by displacement with gas under the influence of gravity, subsequently causing said portions to come into thermal contact with a source of heat, and distributing the internal energy of the gas used for displacing said portions in succeeding por-' tions whereby the available energy of the liquid phase is' used to recover a portion of the material in the gas phase. l

9. A method of supplying gas material that is received in the liquid phase but has a gas phase evolved due to the addition of heat, to a receiving vessel at a predetermined superatmospheric pressure, which method comprises isolating a charge of liquefied gas in one of a plurality of transfer vessels into which it has been introduced under a pressure less than said predetermined pressure, raising the pressure environment of said charge to a value exceeding said predetermined pressure by flowing said charge under the influence of a force of external origintluough a heated region for heating and vaporizing said charge, discharging a desired portion thereof to said receiving vessel whereby a gas phase remainder is left in said transfer vessel having a pressure value equal to said predetermined pressure, isolating a second charge of liquefied gas introduced at a pressure less than said predetermined pressure in a second transfer vessel where it is maintained substan-' tially insulated against the inflow of heat for a desired period of time, and conducting a portion of the gaseous remainder of said first charge into said second charge whereby a portion of said gaseous remainder is condensed in and augments said second charge while the pressure of the remainder is reduced, and completing the cycle by transferring said second charge to said first named intermediate vessel.

10. A method of transferring a liquefied gas that is volatile at normal atmospheric pressure and has a gas phase evolved from a supply vessel, where it is held at relatively low pressure and temperature, to, a receiving vessel at relatively high pressure and elevated temperature by means of transfer vessels arranged in cascade relation and including a vaporizer vessel, which method comprises delivering a metered charge of liquefied gas from the supply vessel into a selected one of said transfer vessels while'another contains as under a higher pressure, reducing the pressure difference between said vessels by effecting heat exchange between the li'quid in said selected vessel and the gas whereby a portion of said gas is condensed, and discharging gas material under the influence of a force of origin external l to said receiving vessel against relatively high pressure from said selected vessel while excluding substantially all heat of external origin prior to said vaporizer vessel.

11., A method of transferring liquefied gas from a supply vessel where it is held at relatively low pressure and temperature to a receiving vessel at relatively high pressure and elevated temperature by means of transfer vessels arranged in cascade relation and including a vaporizer vessel, which method comprises delivering a metered charge of liquefied gas from the supply vessel into a, selected one of said transfer vessels while other transfer vessels contain gas at successively higher pressures, reducing the F pressure difference between said selected vessel and said other vessels by effecting heat exchange between said charge and the gas of said other vessels successively whereby portions of said gas are condensed, combining the portions of gas condensed with liquefied gas to be transferred, and discharging against a relatively high pressure gas material from said selected vessel to said receiving vessel by flowing liquefied gas under the influence of a force of external origin into said vaporizer with resultant equalization of gas pressure at relatively high pressure between said selected vessel and said vaporizer.

12. A method of transferring liquefied gas from a supply vessel where it is held at relatively low pressure and temperature to a receiving vessel at relatively high pressure and elevated temperature by means of transfer vessels arranged in cascade relation and including a vaporizer vessel which comprises delivering a metered charge of liquefied gas from the supply vessel into a selected one of said transfer vessels while other transfer vessels contain gas at successively higher pressures, reducing the pressure difference between said selected vessel and said other vessels by conducting gas successively at higher pressures from said other transfer vessels into the charge of liquid in said selected vessel whereby portions of gas are condensed and combined with said charge, and discharging against a relatively high pressure gas material from said selected vessel to said receiving vessel by flowing liquefied gas under the influence of a force of external origin into said vaporizer with resultant equalization of gas pressure at relatively high pressure between said selected vessel and said vaporizer.

13. A method of transferring gas, material which has a boiling point materially below 273 K. from a region of relatively low pressure to a region of relatively high pressure, which method comprises isolating a metered charge of said material in the liquid phase in an initial transfer vessel of a series selected from a group of series that are arranged in parallel, increasing the pressure environment of said isolated charge in stages preparatory to transfer to a succeeding vessel of the selected series by first-transferring to said charge internal energy from the gas phase in a vessel at higher pressure in parallel with said selected series and then efiecting a further transfer thereto of internal energy from the gas phase in said succeeding vessel, and thereafter discharging said material when at a desired high pressure. v

14. A method of transferring gas material which has a boiling point materially below 273 K. from a region of relatively low pressure to a region of relatively high pressure, which method comprises isolating a metered charge of said material in the liquid phase in an initial transfer vessel of a series selectedfrom a group of series that are arranged in parallel, increasing the pressure environment of said isolated charge in stages preparatory to transfer to a succeeding vessel in said selected series by first cross-equalizing the pressure of the materialin the gas phase between the filled vessel and one at higher pressure in parallel with said selected series, and

then effecting equalization with the pressure in a succeeding vessel of the selected series, augmenting thecharge of liquid being transferred by adding the condensate thereto, and discharging said material when at the desired high p'ressure to .a. common receiver. I

15. A method of transferring gas material which has a boiling point materially below'273 K. from a region of relatively low pressure to a passage of material in the gas phase from a vessel at higher pressure in parallel with said selected series, and then effecting a further counter passage of material in the gas phase from the succeeding vessel of said selected series whereby partial condensation of said gas material is-effected by stages, augmenting the charge of liquid being transferred by adding the condensate thereto, excluding substantially all heat of external origin during said transfer and equalizations prior to a predetermined point, and discharging said augmented charge when at a desired high pressure to a common receiver.

16. A method of supplying gas material to a receiving vessel at-a predetermined superatmospheric pressure which comprises isolating a metered charge of liquefied gas in one of a plurality of transfer vessels into which it has been introduced under a pressure less than said predetermined pressure, raising the pressure environment of said charge to a value exceeding said predetermined pressure by flowing. said charge under the influence of a mechanical force of external origin through a heated region for heating and vaporizing the same, discharging a desired portion of said charge to said receiving vessel leaving a gas phase remainder in said transfer vessel having a pressure'value equal to said predetermined pressure, isolating a second charge of liquefied gas introduced at a pressure less than said predetermined pressure in a second transfer vessel where it is maintained substantially insulated against the inflow of heat for a desired period of time, and conducting a portion of the gaseous remainder of said first charge into said second charge whereby a portion of the gaseous remainder is condensed in and augments said second charge while the pressure of the remainder is reduced.

17. A method of transferring a liquefied gas of a partial condensation of the gaseous material in the liquid phase is accomplished, and venting gas material in the gas phase from the region of lowest pressure at the inception of a cycle.

18. A method of transferring a liquefied gas of low boiling point, from a supply vessel at a relatively low pressure to a receiver at a relatively high pressure, which comprises passing a metered charge of liquefied gas from the supply vessel through a series of liquid locks at successively higher pressures until,the desired high pressure isattained,"causing an exchange of the gas and liquid phases of the charge when it is to pass into each lock at higher pressure, and transfer ring to the liquid phase internal energy of said gas material in the gas phase by a partial conversion of the gas phase into the liquid phase whereby at the time of the coexistence of gas and liquid phases the internal energy of said liquid phase material is at a maximum and the internal energy of the coexisting gas phase is at a minimum.

-19. A method of transferring a liquefied gas of low boiling point, from a supply vessel at a relatively low pressure to a receiver at a relatively high pressure, which comprises passing a metered charge of liquefied gas from the supply vessel there is effected a partial conversion of the gas.

phase into the liquid phase, completing said exchange when desired without conversion of the gas phase into the liquid phase, and causing an pressure region through liquid material whereby I exchange of said gas and liquid to take place with an interchange of gas material in the gas phase at relatively different pressures whereby additional conversion of the gas phase into the liquid phase is accomplished.

20. A method of transferring a liquefied gas of "low boiling point, from a supply vessel at a relatively low pressure to a receiver at a relatively high pressure, which comprises passing a metered charge of liquefiedgas from the supply vessel through a series of liquid locks at successively higher pressures until the desired high pressure is attained, causing an exchange of the gas and liquid phases of the gas material when passing in series, effecting cross-equalization of the pressures of the gas material in the gas phase in the liquid locks, transferring the gas material from the lock at highest pressure'to a receiving vessel, and causing the admission of a new charge to the liquid locks to. take place with the blow-down of gas material in the gas phase from the look at lowest pressure.

21. A method of transferring a liquefied gas of low boiling point, from a supply vessel at a relatively low pressure to a receiver at a relatively high pressure, which comprises beginning a cycle phase into the liquid phase until the critical 'temperature and pressure of said gas material is reached, converting the gas material at the critical pressure and temperature into a homogeneous vapor phase by the input of heat in sufllcient quantities to efiect the desired expansion, and

thereafter further heating the gas material in a high pressure receiving device.

22. A method of transferring liquidoxygen from a transport supply vessel at a'relatively low pressure to a receiver at a relatively high pressure, which comprises passing a metered charge of liquid oxygen ffom said container through a plurality of pressure vessels in series until the desired high pressure is attained, accompanying the passage of said charge with displacements of gas material in the gas phase from a vessel at relatively high pressure into a vessel at lower pressure, in a manner such that there is partial conversion of the gas phase into the liquid phase t0- gether with a transfer of the internal energy in the gas phase-to the liquid phase, transferring the charge from the vessel at highest pressure to the receiver without substantial phase conversion, and

venting the vessel at lowest pressure for cepticn of a new charge.

23. A method of transferring liquid oxygen from a transport container by means of associated vessels arranged in cascade, which method comprises charging a thermally insulated transport container with a body of liquid oxygenthat is maintained at relatively low pressure, discharging liquid oxygen from said container through said associated vessels to a receiver in a succession of metered charges, and passing the gas in said receiver from the same in counter-current relation to the liquidadmitted to said receiver.

24. A method of transferring liquid oxygen from a transport container by means of associated transfer vessels arranged in cascade to a receiver normally operating at a relatively high the repredetermined pressure.

- 25. A method of transferring a precious volatile liquid from a transport container to a stationary receiver, which method comprises interposing a plurality of communicable transfer vessels between said container and receiver, delivering a metered charge from said container to a selected transfer vessel, discharging the liquid contents of said selected transfer vessel through displacement by gas admitted from another vessel at a higher pressure, condensing at least a portion of the displacing gas during the interim of discharge, adding the resulting condensate to the liquid discharged, and carrying away heat of external origin with the liquid discharged that may have entered the liquid in any of the transfer vessels.

26. In a cascade system of the character described, the combination with a plurality of vessels in cascade relation adapted'to receive liquid material capable of evolving a gas phase, of means for introducing a predetermined charge of liquid material from the supply vessel into one vessel while at a relatively low pressure, means for introducing gas into said vessel from another vessel at a higher pressure, said gas introducing means being arranged to eflect a condensation of at least a part of the gas phase material into liquid material, and means utilizing. a forceof external origin forcausing a discharge of liquid material to receivers. I

27. In, a cascade system of the character described, the combination with a plurality of vesi I sels in cascade relation adapted to receive liquid material capable of evolving a gas phase, of means for selecting one of a pair of initial transfer vessels at low pressure and introducing a predetermined charge of liquid therein from a low pressure supply vessel, means for equalizing the pressure between said selected vessel and the other of said initial pair, means for interchanging gas and liquid between said first selected initial and another'selected vessel at a relatively high pressure by the passage of gas phase material in heat exchanging relation with the liquid phase material therein, and mean for displacing the liquid phase material from said'selected vessel by the application of forces of external origin on the liquid.

29. In' a cascade system of the character described, the combination with a plurality of vssels in cascade relation and adapted to receive liquid material capable of evolving a gas phase,

of means for selecting a transfer vessel at low pressure and introducing a metered charge of liquid therein from a supply vessel, means for equalizing the pressure between said selected vessel and another transfer vessel'at a relatively high pressure by the passage of gas material thereinto in heat exchanging relation with the liquid material therein, and means operative under the influence of gravity for discharging said charge to a receiving vessel.

30. In a cascade system of the character described, the combination with a plurality of vessels in cascade relation and adapted to receive liquid material capable of evolving,a gas phase, of means for introducing a metered charge of liquid into one of said vessels, means for equalizing the pressure between said first vessel and a selected one of the remaining vessels by the passage of gas from said selected vessel to said first vessel, and means for causing an interchange of gas and liquid between said first and said selected vessels.

31. In a cascade system of the character devessels, means for-equalizing pressuresbetween.

said remaining vessels, and means for discharging a desired portion of gas material from said selected vessel to a receiving vessel.

' '32. In a cascade system of the characterdescribed, the combination with a plurality of transfer pressure vessels each arranged to receive a metered chargeof a volatile liquefied gas, of means for withdrawingliquid from each of said vessels, means for effecting gas and liquid exchange associated with certain pairs of said vessels, means for efiecting equalization of pressures prior to said exchange, and means for effecting cross-equalization of the pressures of gas between other pairs of said vessels, said last named means being arranged to pass gas through liquid and efiect a partial condensation from the gas phase into the liquid phase.

33. In a cascade system of the character described, the combination with a pluralityof transfer pressure vessels each arranged to receive a metered charge of a volatile liquefied gas, of

, means for withdrawing liquid from each of said vessels, means for effecting the counter passage of gas and liquid associated with certain of said vessels whereby gas at relatively high pressure passes through liquid at a lower pressure, additional means for effecting quickly the counter passage of gas and liquid without gas passing through liquid, and means for effecting crossequalization of the pressures of gas between paraliel pairs of vessels at relatively different pressures in a manner affording a discharge. of gas through liquid.

34. In a cascade system for transferring liquid oxygen and the like, the combination with asupply vessel for the liquid oxygen maintained at a relatively low pressure, of a heating device for the oxygen maintained at a relatively high pressure, a plurality of transfer pressure vessels certain of which discharge successively one into r atile liquid material from a supply vessel where another whereby a plurality of different intermediate pressure levels may be maintained, a conduit for supplying a charge of liquefied gas from said supply vessel to a transfer vessel at the lowest intermediate pressure, gas and liquid passage control means associated with said vessels and arranged to pass gas through the liquid and condense at least a portion of the gas whereby the net loss is reduced, and means for passing each of said vessels, me'ans associated with certain of said vessels for substantially excluding heat from said charges thereby preserving the refrigeration, condensing capacity or available energy of said charges, means for effecting, by the relative counter passage of material in gas and liquid phases associated with said vessels in heat 'exchanging relation, a condensation of portions of gas into liquid whereby the net blow-down accompanying initial charging is reduced to relatively low amount, and means for applying to the material forces of external origin for finally discharging material from the liquid phase.

36. In a cascade system for transferring a vol'-' atile liquid material from a supply vessel where it 'evolved due to heat gained in the transfer and for effecting the relativecounter passage of liquid and gas phases in heat exchanging relation,

means associated with certain of said vessels for preserving the refrigeration of material, in the liquid phase for use in condensing a desired portion of material in the gas phase during said counter passage whereby the ultimate loss of material in the gas phase is reduced to a desired low value, and means for finally discharging material from the liquid phase by the application of forces of external origin.

37. In a cascade system for transferring a volatile liquid material from a supply vessel where it is held at a relatively low pressure to a receiving device under a relatively high pressure, the combination of a plurality of transfer vessels adapted forholding a succession of charges of material at a plurality of pressure levels in both the liquid and gas phases, said gas phase comprising gas evolveddue to heat gained in the J transfer, means connecting said vessels in cascade relation for effecting relative counter passage of liquid and gas phases in heat exchanging relation, means associated with certain of said vessels for preserving the refrigeration of material in the liquid phase for use in condensing a it is held at a relatively low pressure to a receiving device under a relatively high pressure, the combination of a plurality of transfer vessels connected in series the first discharging into a second for holding charges of said material and gas evolved therefrom due to heat gained on discharge, means associated with said series of vessels for preserving the refrigeration of saidatile liquid material from a supply vessel where it is held at arelatively'low pressure to a receiving device under a relatively high pressure, the combination with means for, supplying metered charges of said material, of a plurality of transfer vessels connected in series for holding said charges together with any gas that may beevolved therefrom due to heat gained on discharge from said vessels, means associated with certain of said vessels for preserving the refrigeration of said charges of material in the liquid phase from impairment by inflow of undesired heat, means for equalizing the pressure of adjacent vessels by conducting gas in intimate contact with liquid whereby a desired portion of gas is condensed by the refrigeration of the liquid, and means for causing an interchange of gas and liquid between adjacent vessels.

40. In a cascade system for transferring liquid oxygen and the like, the combination with acoutainer for the liquid oxygen maintained at a relatively low pressure, of a heating device for the liquid oxygen maintained at a relatively high pressure, a plurality of pressure vessels certain of which discharge successively one into another whereby a plurality of different intermediate pressure levels may be maintained, a conduit for supplying a charge of liquid oxygen from said container to a. vessel at the lowest intermediate pressure, gas and liquid exchange passages connecting said vessels which discharge one into the other, additional gas exchange passages whereby gas pressure in a pair of communicating vessels may be equalized, and conduit means for transferring the charge from a pressure vessel at the highest intermediate pressure to said heating device.

41. In a cascade system for transferring liquid oxygen and the like, the combination with a container for .the liquid oxygen maintained at a relatively low pressure, of a heating device for the liquid oxygen maintained'at a relatively high pressure, a plurality of pressure vessels certain of which discharge successively one-into another whereby a plurality of different intermediate pressure levels may be obtained, a conduit for supplying a charge of liquid oxygen from said container to a vessel at the lowest intermediate pres-,

sure, gas and liquid exchange passages connecting said vessels which discharge 'one into the other, supplemental gas exchange passages connecting said vessels which'discharge one into the other, gas equalizing passages connecting vessels arranged tojbe maintained at the same pressure levels, and conduit ineans including a return connection connecting said heating device directly to a vessel in said discharge series which is at the highest pressure in the series.

42. In a cascade system for transferring liquid oxygen and the like, the combination with a container for the liquid oxygen maintained at a rel- -atively low pressure, of a heating device for the liquid oxygen maintained at a relatively high pressure, a plurality of pressure vessels certain of which discharge successively one into another whereby a plurality of different intermediate pressure levels may be maintained, a final pressure vessel arranged to receive the discharge from the series of successively charged pressure vessels and maintained at the highest pressure level intermediately maintained between said container and said heating device, means for transferring a charge of liquid oxygen from said container to a vessel at the lowest intermediate pressure, means for effecting the advance of said charge through said series accompanied by gas displacement and partial condensation of the gas displaced into liquid whereby the charge is augmented, means for supplying heating medium to'heat said final pressure vessel when the temperature and pressure of the gas material therein attains critical values, and means for transferring the charge in a' homogeneous phase from said final pressure vessel to said heating device.

43. In apparatus for transferring liquid oxygen and the like, the combination with .a portable liquid oxygen container, of a receiver, 'a plurality of communicable transfer vessels arranged .in series and interposed between said container and receiver, .means for admitting a metered charge of liquid from said container to the first of said vessels while communication with any succeeding from any selected transfer vessel.

44. In apparatus'for transferring a precious volatile liquid, the combination with a heat insulated supply container, of a receiver, a plurality of communicable transfer vessels arranged in series and interposed between said container and receiver, means for admitting a metered charge of liquid from said container to the first of said transfer vessels while communication is closed from the latter'to any succeeding vessel, meansfor delivering liquid from said first vessel to a succeeding vessel under the influence of a gravity field accompanied by gas displacement, means for venting said first transfer vessel, means for equalizing gas pressures in said transfer vessels, and means for efiecting the delivery of the liquid from the final vessel of the series to said receiver while communication is closed to the preceding vessel.

45. In apparatus for transferring a precious Zvolatile liquid, the combination with a heat insulated supply vessel, of a receiving vessel, a plurality of intermediate vessels comprising a group arranged in parallel and interposed between said sels of said group is closed, means for delivering,

said charge to said receiving vessel, said means including connections for selectively efiecting the passage of gas material from other vessels of said group having internal energy of relativelyhigh volatile liquid, the combination with a heat insulated supply vessel, of a receiving vessel, a plurality of intermediate vessels comprising a group arranged in parallel and interposed between said supply vessel and said receiving vessel, means for selecting and venting a vessel of said group,

means for transferring a metered charge of liquid from said supply vessel to said selected'vessel when vented and communication with other vessels of said group is closed, means for delivering said charge to said receiving vessel, said means including connections for selectively and successively effecting a counter passage of gas material from other vessels of said group through said liquid charge, whereby condensation of gas material into liquid is eifected and pressure equalizations with that insaid other vessels take place in stages, and means for effecting delivery of said charge from said selected vessel to said receiving vessel while communication is closed to the pre ceding vessel.

47., In apparatus for transferring gas material that has a boiling point materially below 273 K., the combination with a heat insulated supply vessel, of a receiving vessel, a plurality of transfer vessels arranged to form a group of series that are in parallel and interposed between said supply vessel and said receiving vessel, means for admitting a metered charge of liquid from said supply vessel to the initial vessel of a selected series while communication with a succeeding vessel of said seriesis closed, means for delivering said charge to a succeeding vessel of said series including c onnections for establishing gaseous communicationbetween said filled vessel and said succeeding vessel whereby a first stage of pressure equalization is effected and additional connections for establishing gaseous communication between said filled vessel and a vessel in parallel with said succeeding vessel for cross-equalization of the pressure whereby a partial condensation of material in the gas phase into the liquid phase is effected for augmenting the charge transferred, and meansfor effecting delivery of said augmented charge from a final vessel of the selected series to said receiving vessel while communication is closed to the preceding vessel in said selected series.

JOHN J. MURPHY.