US2068119A - Method and apparatus for generating gas - Google Patents

Description

Jail. 19, 1937.

.1. T. WHITFIELD METHOD AND APPARATUS FOR GENERATING GAS Filed Feb. 4, 1935 3 Sheets-Shet 1 I INVENTOR (fa/52v! A5912 w Jan. 19, 1937. .1. T. WHITFIELD METHOD AND APPARATUS FOR GENERATING GAS 3 Sheets-Sheet 2 Fi led Feb. 4, 1935,

Jan. 19, 1937. J. T. WHITFIELD METHOD AND APPARATUS FOR GENERATING GAS s Shets-Sheet 3 Filed Feb. 4, 1935 o a Y v 7 o m MW 7 N 2 Z 7 Patented Jan. 19, 1937 METHOD AND APPARATUS FOR GENERATING GAS John T. Whitfield, Boston, Mass.

Application February 4, 1935, Serial No. 4,980

28 Claims.

This invention relates to a method and apparatus for generating a gas from its solid and particularly above its critical temperature. In a more specific aspect the invention relates to a method and apparatus for extinguishing fires.

It has heretofore been known that carbondioxide gas is useful for many purposes and particularly for the extinguishing of fires. Its use, however, has been limited by the difiiculty of conveying it quickly in large quantities to the places at which it is needed. Thus, in the fighting of fires carbondioxide gas has been used to a small extent in portable fire extinguishers which are filled with a strong solution of a carbonate or bicarbonate and are also supplied with a small container of an acid which is spilled into the carbonate solution when the fire extinguisher is in use. Liquid carbondioxide has also been used to some extent for extinguishing fires but in either go form, whether chemically combined or liquid, the

bulk and particularly the unwieldy apparatus required, places a very narrow limit on the extent to which the carbondioxide may be used in the fighting of fires.

Although it has been recognized for some time that carbondioxide gas is one of the most effective agencies for combatting fire and that a concentration as low as 17% in the atmosphere surrounding a fire will prevent combustion, nevertheless its application has been very limited and fire fighting is still done almost entirely with water orwith such non-inflammable and more or less volatile liquids as carbon tetrachloride.

I have now discovered a way in which solid '35 carbondioxide may be made to supply carbondioxide gas in large quantities and I have invented an apparatus which is no more cumbersome and extremely more eflective than the present fire fighting apparatus designed for use with 40 water.

. In the accompanying drawings,

Figure 1 illustrates diagrammatically an apparatus built in accordance with my invention; Figure 2 illustrates a modified form of a similar 45 apparatus; and

Figure 3 illustrates diagrammatically an apparatus which is designed to combine the functions of a refrigerating apparatus and a fire extinguishing apparatus.

60 Figure 4 illustrates anothermodified form of .the apparatus.

Figures 5 and 6 show diagrammatically one application of my invention to structures such as ships, storage buildings, etc.

55 Figure"! shows in vertical section a modification of my invention adapted for use as a portable fire extinguisher.

Referring particularly to the drawings in which I have illustrated an embodiment of my invention which I now believe to be the most satis- 5 factory form as applied to fire fighting apparatus. The reference character 5 indicates a pressure chamber or gas generator. In the bottom of this chamber a grating ii is secured several inches from the bottom; for example, about 10 3 inches will ordinarily be sufiicient. Blocks 1 of solid earbondioxide commercially known as dry ice" are piled on the grating. The generator is then filled with a. suitable liquid having a low freezing point which surrounds at least a part of 15 the dry ice on the grating. The liquid is heated by a suitable heating means 8 positioned in heatexchange relation to the generator. I have in dicated such a heating means diagrammatically in the drawings as a. gas burner under the gen- 20 erator, but it will be understood, of course, that any other well known type of heating device could be provided instead of ,the gas burner. Above the liquid level in the generator is a bubblescreen 9 which, in the present instance, I have 5 shown as consisting of two screens holding between them a dehydrating agent such as dry calcium chloride; and above the bubble scren is a valved pipe connection i0 adapted to receive a. hose or other pipe. 30

A supplementary storage tank II is provided adjacent the gas generator 5 and is connected thereto by a valved pipe I2 extending from its bottom to the bottom of the generator. A relief valve I3 is providedon the tank H for relieving excessive gas pressures and a valved connection l4 leads from the bottom of the tank I l to a pump IS. The pump is connected by a pipe It to a heating coil IT or other suitable heat exchanger,

,from which a valved pipe l8 leads back to the gas generator 5.

Suitable gages areprovided, e. g., a gage I!) to indicate the gas pressure and a gage to indicate the water-level, etc. The gage 20 is shown diagrammatically as a dial indicator and may be any desired type of liquid level indicator. A safety valve 2| is preferably provided on the gas generator 5.

' In the embodiment illustrated in Figure 1 the generator is split horizontally and is clamped together by the flanges 22 and 23 which preferably includes a sealing gasket 34 between them so as to form a gas-tight joint. The upper section in the embodiment illustrated in Figure 1 is counterbalanced by the weight 24 through chains or cables 25 which pass over pulleys 26 on a framework (not shown) above the upper section. This counterbalancing assists in lifting and lowering the upper section for charging the pressure container with solid carbondioxide.

In operation the flanges 22 and 23 are unclamped and the upper section lifted from the lower section, after which the blocks of solid carbondioxide are placed on the grating 6. The upper section of the generator is then replaced and the flanges 22 and 23 securely clamped together so as to form a gas-tight seal and one which will withstand the operating pressure of 300 to 100 pounds per square inch.

Calcium chloride brine is then pumped into the generator 5 from the source of supply (not shown) until the solid carbondioxide is substantiaily covered with brine. In the meantime the burner 8 has been lighted so that the brine is being heated. This heat, however, is immediate- 1y absorbed by the gas which is liberated and by the solid C02, a large part of which gas is dissolved in the aqueous brine. The heat supplied to the brine should be suflicient to maintain its temperature well above its freezing point since a freezing of the brine would render the device temporarily inoperative. Above this requirement the amount of heat supplied will-be to a certain extent controlled by the rate at which it is desired to generate the gas.

So long as the solid carbondioxide is completely covered with the liquid the rate at which the gas is generated will be controlled by the temperature of the liquid. Since, however, the liquid cannot be allowed to freeze without interferring with the operation of the apparatus, the control possible by varying the temperature of the liquid is limited to temperatures above its freezing point. When it is desired to further reduce the rate of gas production a different method of control must be adopted and to meet this need I provide for withdrawing liquid from the generator so that a smaller amount of the solid carbondioxide is covered with the liquid. This method obviously is also applicable to control over the entire range without changing the temperature of the liquid. In order to avoid building up of excessive pressures while the full capacity of the generator is not required, I provide the supplemental tank ll into which the brine may be withdrawn when the working pressure isexceeded in the generator.

Thus, assuming that the valve in the pipe "I is temporarily closed the continued evolutionof gas from the solid CO2 would very rapidly build up pressure in the generator 5. In order to prevent this from becoming excessive the valve in the connection I 2 is opened and the brine or a portion thereof is permitted to escape into the supplemental tank I I. No circulating means is required to eifect this removal of brine into the tank ll since the generation of gas in the generator 5 will of itself tend to force the brine out of the generator. If the pressure in the tank II should be too high to permit this escape of liquid from the generator 5 the relief valve l3 on the tank I I may be opened so as to reduce the pressure therein and permit a further amount of brine to escape into the tank from the generator. If the pipe I0 is completely closed the brine should be entirely withdrawn from contact with the solid CO2. If, however, a continuing but smaller supply of CO2 gas is required the level of the brine may be lowered without removing all of the brine from the generator.

aoeana In the parts of the generator where the solid CO2 is not in contact with brine the heat contained in the gas which surrounds the solid CO2 is very quickly consumed inthe evaporation of some of the solid so that an insulating blanket of gas at a very low temperature covers the solid CO2 and renders further evaporation of the solid extremely slow.

When all of the brine has been withdrawn from the generator the heating means under the generator may be cut off; but in practice, where the flow of the gas is only temporarily interrupted, it is not necessary to cut off the heating means since the blanket of gas forms such a poor conductor and the heat requirements for the generation of gas are so great that there will be relatively little effect on the solid C02 from the heating means in the absence of brine to conduct the heat into contact therewith.

When it is desired to reintroduce the brine into the generator this may be done automatically by maintaining the pressure in the supplementary tank ll slightly above that desired in the generator and' leaving the valve in the connection I! open. With the apparatus operated in this manner the brine will be automatically forced from the generator into the supplementary tank when the desired pressure is exceeded in the generator and will be again forced back into the generator when the pressure therein again falls to or below the desired working pressure. when operated in this manner, an automatic, e. g., ordinary safety valve set to operate slightly above the desired working pressure of the generator may be used in place of the valve l3. An apparatus arranged for this automatic method of operation without the forced circulation is illustrated in Figure 2. The expansion of the gas in the tank H which is required to drive a large volume of the liquid back into the generator will ordinarily be taken care of by the heat which is absorbed from the atmosphere and such difference in pressure on the liquid as is caused by the expansion of the gas inthe tank II will ordinarily not be beyond the permissible variation in working pressure of the gas delivered from the generator 5. In some cases, however, it' may be desirable to supply some additional heat to the brine in the tank H.

In some cases it may be desired to control the reintroduction of brine so that additional brine is supplied to the generator 5 from the supplemental tank although the pressm'e in the latter is below that of the former. of course, it is necessary to provide a positive circulating means such as the pump ii. In the embodiment of my invention which is illustrated in Figure 1, I have arranged this sequence of apparatus, that is, the generator, the supplemental tank and the pump, inseries with a mpplemental brine heater I]. With this systema continual circulation may be. maintained so that heated brine is introduced near the surface of the liquid in the generator 5 and the level in the generator may be controlled by the relative regulation of the relief valve I3 and the valve in the connection II. The introduction'of heated brine near the surface of the brine in the generator is very important in case the generator is operated at a, temperature near the freezing point of the brine. In this case the heat added to the brine near the bottom of the generator will often be completely consumed in the evaporation of the solid 00: before itreaches the upper part of the brine and unless additional heat is supplied adiacent the In such cases,-

"60 i agent is absolutely eliminated. and even without r H I '2,oe s,11o r surface the upper portion of the brine may be- 7 cumference of the generator may be provided as illustrated at "a in Figure 2, or instead of such external heating coil heating means may be provided around the exterior of the generator or through the space occupied by the liquid in the generator. Thus as shown in Figure4, a flue from the main heater 8 might be arranged so as to supply heat to the liquid, as for example at 36, or fire tubes might be arranged through the pressure chamber of the generator so as to heat.

the liquid preferably adjacent its surface, e. g., as shown at 3'|, other heating means might be provided in the space normally occupied by the liquid. Although such means as are shown in Figures 1 and 2 are ordinarily suflicient to prevent freezing and provide for emcient operation if carefully controlled, it is advantageous to pro-v vide some heating means within the space indicated for the liquid in order that the brine may be quickly thawed in case it should become frozen because of-fcareless operation.

In use it is desirable to regulate the intensity of heating, both at the main heater 8 and at theauxiliary heaters ll,. Ila and/or. and 31, according to the pressure produced by the gas within the generator, until the temperature drops to a point substantially above the freezing point. Thereafter the heating should be controlled-to maintain the temperature above the minimum and the level of the liquid should thereafter be controlled to maintain the desired'pressure. The heater lla.in Figure 2 should preferably be shut ofi when the liquid level drops below the intake of its heating coil, and all heaters should ordinarilyshutofi when the chamber 5 is emptied of itsv liquid.

When the apparatus is used in fire fighting it is preferably set to operate at a pressure of around .300 to 400 pounds per square inch and one or more rubber hose which are adapted to carry such high pressure are connected to the generator and manipulated by the firemen in the. same manner as the water hose are at present manipulated except, of course, that the gas is always directed at the base of the flame a should not be used to soak adiacent'material to prevent it from catching fire. When the bubble screen I is used and particularly when a dehydrating agent is used in connection with the.

- bubble screen either in the generator or at a separate point in the gas delivery line the possibility of injury from the use of the fire extinguishing due not to the smoke or the fiames or the fire itself but to the water or chemical agent which is used to extinguish the fire. with the use of my invention; all of'this damage amounting to millions of dollars annually may be saved and in addition many fires may be brought under conmi one apparatus presentso that, one may be is practically ne8l1s1'-' trol or completely, extinguished which would be hopeless of control by, present fire fighting methods.

'It is an additional important advantage that carbondioxide gas under pressures at which it is supplied by the apparatus of my invention can be conducted to any conceivable location at which a fire might occur. Thus on the upper fioors of vtall buildings where it would be impossible to provide water from any modern fire fighting apparatus, it is a simple matter to conduct a gas such as carbondioxide, the only problem being that of supporting the necessary length of hose, which problem can obviously be overcome with comparative ease as by suitably The blast which is delivered from the-hose when my invention is usedis not only under a pressure-generated by the gas itself but is at a very low temperature due to its evaporation and its expansion when released from the hose. Thus there is combined with the smothering effect of the gas a cooling eifect andthe cooling effect is due both to the blast, of which the blowing out ofa candle is an example, and to the very low temperature of the gas which in effect substantially freezes the fire out of existence.

In the operation of the apparatus a single charge of "c'arbondioxide would be suflicient for any but the most serious fires. 'If, however, it is necessary to recharge the apparatus during its use;

'this may readily be done by bringing additional blocks of solid CO: on trucks to the fire and no extraordinary precautions are necessary in transporting these blocks since theheat required to convert them into gas is so great that merely carrying them in anyclosed container, as in the body of a closed truck surrounds them with a blanket,

of low temperature air which so greatly retards the further evaportion-as to make it unnecessary to. use any additional insulating means.

These blocks of solid carbondioxide are at present supplied as an article of commerce .the form of'a compressed snow in blocks abou 12 inches on-an edge and weighing about'36 blocks to a ton more or lessaccordin'g to the extent to which they are compressed. If it is necessary to recharge at the fire there ordinarily would be more than continued when annther is being used and fl pp r section maybe unciamped and lifted and the generator charged in the same manner as at [the beginning of the operation.

For keeping the solid :carbohdioxide over long periods as, for example,- before ahialar'm is. received for a firm-it isnecessary to provide special insulated chambers -or vaults such as are ordinsrily used in storing. solid carbondioxide'injthe factories where it-is made. On fireboats it be desirable and practicable .to provide [such vaults in the hold so that a relatively large 1 supply will always be on hand. but with fire trucks Ion which my apparatus may be mounted, it will,

ordinarily be preferable. to carry only a supply of solid carboiidioxide which is contained in the generator and torely on'additional supplies brought by truck from the factory or from a storage vault if required for continued operation.

"@At'ligure 3 I have illustrated an u e which may be used as a stationary equipment inbuildings or on shipboard, etc. The supply of I solid carbondioxide may be contained in a chamconnected with the atmosphere through a relief valve 29 which maintains a pressure suitable for fire fighting, e. g., of about 400 pounds per square inch. The vent pipe may pass through the building or ship .with connections .30 at suitable points to which fire hose is or may be attached.

. In this manner a refrigerating system and a fire prevention system are combined. During -ordinary conditions when there-is no fire the solid carbondioxide gradually evaporates, cooling the brine and thus serving as a refrigerator and the r gas which is formed in the storage chamber is vented to the atmosphere. In case of a small fire the pressure in the chamber may be sufficient and a hose may simply be taken 'from a pipe and cold carbondioxide gas directed against the burning material utilizing the pressure which already exists in the storage chamber. -In case of a more serious fire calcium chloride brine or other suitable liquid would be run intothe storage chamber and heating means applied so that it would operateas a gas generating chamber in the same manner as described above.

In the embodiment illustrated in Figure 3 I have shown the. chamber I lb as built around the generator band connected at its bottom with the bottom of the generator by means of openings or pipes I21). In this embodiment I have .also provided a relief valve l3b at the top of the chamber l'lb which is adapted to permit sufiicient escape of gas so that the pressure in thechamber' llb will be maintained sufilciently below that of the chamber 51) to keep the liquid from flowing back into contact with the solid carbondioxide. Pipes Nb and I8?) connect the chamber llb with a refrigerating 0011]"). In the operation of this device the'solid carbondioxide .in the chamber 51) normally serves as the refrigerant, absorbing heat constitute an automatic fire protection system 'is required. The heat absorbed in the refrigerating system serves to evaporate more carbondioxide and thus the refrigerating system to a certain extent replaces the auxiliary heater II or llausedlnFiguresland-2.

Outlets." maybe provided in the pipe llb to somewhat similar to the'well known sprinkler systems used in connection. with a water stand- 1 tions such that one or another would supply carpipe. Such outlets 3|, maybe arranged in posibondioxide gas to extin sh a fire in any possible location and these outlets may be controlled thermostatically, e. g., as in; theme of sprinkler systems. Such a protection system would not only bemore 'eflectivxevjhan water sprinkler 'sys-- 'tems but would also bid the possibility of damage which sometimes occurs with the water sprinkler systems when an outlet is accidentallyopenei- In-order to avoid any possibilityot sup chamber Sc is provided, 1 Go into which the solid carbon dioxide is red when focation by excessive escape of carbondioxide in the rooms intended for human occupancy theoutlets could be constructed, e. g., as shown at 32, to give a warning whistle when the carbondioxide gas is escaping therefrom. This would serve not only as a warning against suflocation to the human occupants oi; the building but would also serve as a fire alarm.

Figures 5 and 6 show an arrangement embodying my invention which is particularly applicable to ships, storage buildings and the like. In this arrangement, the pressure storage chamber may be essentially as shown in any of Figures 1 to 4, but ispreferably heavily insulated, e. g., as shown in Figure 4, from the atmosphere and/or any other source of heat except that used for generating the gas. The bottom of the chamber 50 is connected through the pipe I to the insulated storage tank He in which it is kept hot by means of the indirect h ater He connected to the boiler "of the ship or uilding.

The gases generated in the chamber 50 are cold storage space' 42 and finally through the conduits 43 to the closed storage rooms or hold 44.

In Figure 6 I have shown the same arrangement as in Figure 5 except that in this case an air cooler 46 has been included between the chamber 5c and the valved portion of the conduit llc. In this figure I have also shown an air intake and stack which are closed fromthe lower parts or the ship so that with a suitable oil or gas firing the fire fighting apparatus could remain operaled oil through the conduit I00, which is provided tive even after the engine room had filled with water, steam or smoke.

With the arrangements just described I have provided for constant utility of the device with in the air cooler 46 or the cold storage space 42,

rooms 44- or 50 or into partitions or other inflammable closed spaces, where it prevents fire .by'providing an atmosphere'incapable of sup-I porting combustion. I

In case or fire a supply of hot brine is always ready to begin the rapid generation ot gas and will be automatically ted to theber 50 as it is needed, because of the reduction or pressure therein. But even before the hot brine is used there is alwaysa maintained pressure ofiihe' extinguishing gas in the system so that there can be no delay in its; effectiveness. v v

In Figure 7 I have shown a still simpler form of the apparatus intended for useas an emergency extinguisher. In this case the pressure generator with a movable basket the generator isto be used- I I The basket Se is carried upon a ,1 pp'ort rod 4! which in turn is secured to the; cross-bar 4|.

conduit lilc where its low temperature is utilized and eventually passes into the hold or storage Branch rods 42 provided at opposite. sides so 1 that the cross-bar ll may be held by any of the branches 4 3 and the basket 60 thereby supported pressure by a cover 46 held in place by clamping means not shown.

Otherwise the generator illustrated in Figure 7 may be substantially the same in construction and operation as those already discussed above, the numerals 80, "lo. I20, l8 c, we and He corresponding to the corresponding parts 8, l0, l2, l8,

' l9 and 2| on Figure 1.

. Although I have illustrated and described my invention with particular reference to fire fighting, in which application my invention is capable of saving millions of dollars of destruction annually, nevertheless it is to be understood that my invention is alsoalpplicable wherever it is desirable to obtain-a gas in quantity fromits solid form. Thus it may be used in the chemical industries or in other situations which will at once suggest themselves to-those skilled in the art.

Similarly, although I have described the apparatus as a large unit suitable to be mounted on a truck or in a boat or bpilding, it will be understood that it may be made. in small units suitable to be carried by one man for fighting fires or for other purposes and. such a 'unit may be made so that the cooling effect of the gas-generator mayserve to protect the operator from the heat of the fire which he is working against. Y Similarly many changes in the construction of the apparatus and of the particular materials used may be resorted to without departing from the scope or the spirit of my invention. Thus circulation instead of. piling the solid carbondioxide directly onto the grating, the solid carbon dioxide may be loaded into a basket 38 which can be loweredinto or removed from the generator chamber.

For simplicity of illustration and in order that the drawings may be more'easily understood, I have shown gages and indicators directly upon the apparatus. It will be readily appreciated, however,-'-by those skilled in the art that because of the low temperatures involved and the resulting likelihood of frosting, it will ordinarily be more satisfactory to have thesegages positioned at points remote from the generator.

' Many different liquids may be used in the generator andthese may or may not be aqueous solutions, for example, alcohol or even such liquids as carbon tetrachloride or trichlor-ethylene might be used. In general, however, it is desirable to use a liquid which is a solvent of carbondioxide as since if the gas does not dissolve in the liquid it tends to form a blanket over the solid carbondioxide which prevents the liquid from coming into contact with,it.. Furthermore when the liquid is a solvent a considerable ,portion'of the gas is conducted through the liquid in solution and evaporated from its surface, thus reducing the violent'bubbling through the liquid. The dissolved gas also tends to be driven out from the solution at the heating surfaces from .which bubbles rise through the liquid, thus promoting in the liqiiid and helping to prevent any freezing due'tt local stagnation. The liquid which is chosen must, of course, having a freez- 4. An apparatus as ing point substantiallybelow the temperature at which the apparatus is designed to operate and should preferably have a relatively high specific heat. For these-reasons it is ordinarily desirable to-use aqueous liquids and to control the melting point by the use of a suitable solute such as calcium chloride, g r

The above alternatives are not, ,of course, exhaustive but are merely cited as exemplary of the many ways in which my apparatus could be changed within the scope of my invention.

What I claim is: I

1. A fire extinguishing apparatus which comprises a pressure storage chamber with a portion thereof removable for supplying to the interior thereof a charge of solid volatile fire extinguishing substance, means for heating said charge -whereby to effect rapid generation of fire extinguishing gas in said chamber, a body of liquid adapted to serve as a heat exchange medium in said'chamber and a conduit adapted to deliver said gas from said chamber to locations at which fire protection is desired.

2. A fire extinguishing apparatus which ,comprises a. pressure storage chamber with aportion thereof removable for supplying to the interior thereof a charge of solid volatile fire extinguishing' substance, means for heating said charge matically discharged therefrom into the atmosphere as required to relieve said chamber and conduit from pressure in excess of said predetermined value. I

3. An apparatus as defined in claim 2 in which the relief valve is at the end of the conduit beyond the valve which controls delivery of the gas at the protected location, whereby'clogging'of the line whichwould render it inoperative to deliver the fire extinguishing gas may be immediately made apparent by increasing pressure inthe chamber.

defined in claim' 2 in which.

a heat-exchange member is provided between the relief valveis discharged into the atmosphere whereby gas cold from evaporation in the chamber may be warmed before passing into the at- Y chamber and the point at which the gas from the mosphere and excessive condensation or frosting at the point at which gas is discharged into the atmosphere thereby avoided.

5. An apparatus as defined in claim 2 in which an air cooling heat-exchanger is provided between the chamber and the valved portion of the conduit, whereby the necessary evapoffiion in said chamber serves constantly for conditioning them in a structure protected against fire thereby.

6.411 a. structure subject to fire hazards and A comprising spaces occupied by living persons, and closed spaces notoccupied by living persons, the combination as-vdefined in claim 1 in which the conduit normally discharges into said closed spaces whereby to maintain therein an atmosphere incapable of supportingcombustion, but includes means for divertingv the gas discharge 7. An apparatus as defined in claim 2 in which the means for heating the charge is automatically regulated in response to pressure within the chamber whereby to maintain'the desired pressure for instant and continued use in emergency. v

8. A fire extinguishing apparatus which comprises a pressure storage chamber with a portion thereof removable for supplying to the interior thereof a charge of solid volatile fire extinguishing substance, means for normally storing a heat exchange liquid out of contact with the charge and for raising the level of the liquid in the chamber so as to surround said charge therein when fire extinguishing gas is required, and means for heating said liquid.

9. The apparatus as defined in claim 8 which includes means for heating the liquid while it is held away from the charge whereby it may be maintained at all times at a temperature sumciently high so that a rapid generation of fire extinguishing gas may begin immediately when the liquid is raised to a higher level in the chamber.

10. A portable 'fire extinguisher having the combination as defined in claim 1 and which fur-.

ther comprises means providing a verticallwmov-i able false bottom within said chamber for supporting a charge of the volatile solid, and means operable from outsideof said chamber for moving to and holding at various levels, above and below the liquid level in the chamber, said false bottom whereby the charge and any desired part thereof may be raised above or submerged in th heating liquid.

11. A fire extinguishing apparatus comprising a pressure-resisting container partially filled with. a liquid, means therein for supporting a supplyof solid carbon dioxide out of contact with the walls of the container but in contact yvith the liquid, means for supplying heat to the ii'quid, and

means for conducting carbon dioxide gas'from dioxide gas partially filling said container, a supply of solid carbon-dioxide in said-container in contactwith said liquid, means'for maintaining the temperature of the liquid above the freezing point and means for conducting carbon dioxide I gas from said, container to the vicinity of a fire.-

13. apparatus as defined in which includes a means for catching. spray or bubbles and returning the liquid thereof to the container.

14. An apparatus as defined in claim 12 in which the liquid freezes substantially below C. 15. A fire extinguishing apparatus comprising a container for solid 00;, a pipe leading therefrom, a vent means vfor effecting escape of CQ:

gas to the atmosphere from the space defined by the container and the pipe 'when produced in greater quantity than is required for firefi hting and for preventing escape of gas which is required for fire fighting, valved outlets from said pipe at spaced intervals, means-responsive-to the-with-' drawal of CO: gas through. one or more of said spaced outlets for admitting a liquid into the surface.

which the valved outlets are adapted to be operated automatically when a predetermined temperature is attained.

17. An apparatus as defined in claim 15 in which the vent'means includes a relief valve adapted to maintain a super-atmospheric pressure in the container and the pipe. I

18. An apparatus as defined in claim 15 in which the vent means includes a relief valve adapted to maintain a predetermined superatmospheric pressure in the container and the pipe, and'means responsive to reduction of pres.-

. sure in said container for supplying a liquid tosaid container whenthe pressure therein falls below the predetermined normal but adapted to hold the liquid out of contact with the solid CO2 in the container when the predetermined pressure is maintained.

. 19. An apparatus for converting a solid into a gas, comprising a gas generating pressure chamber, a gas delivery opening therefrom, means in said chamber to'hold a supply of the solid in excess of the amount which-can be dissolved'by the liquid surrounding it, means for supplying aliquid thereto into direct contact with the solid,

and means for heating the liquid.

20. An apparatus as defined in claim .19 in-'- cluding a supplementary chamber connected to the first so that the liquid may be drawn thereinto, and means for controlling the flow between said supplementary chamber 'and the gas generating chamber.

21. An apparatuses defined in claim 19 in.- cluding a supplementary pressure chamber connected to the first by an opening below the supply of solid therein, and a valve adapted to release gas from thesupplementary chamber when the desired pressure is exceeded,'whereby the liquid will be forced into the supplementary chamber from the generating chamber by the greater pressure therein. a

22. An apparatus as defined in claim 19 which includes a supplementary chamber, anvope'n connection between the bottom of the supplementary chamber and the bottom of the generating chamber, and an automatic pressure cont lied valve on the supplementary chamber adapt to release gas when the desired operating pressure of the generating chamber'is exceeded.

23. An apparatusesdefined in claim 19 which includes supplemental means for heating the liquid adjacent its upper surface.

24. An apparatus as defined in claim 19 which.

includes means for regulating-the extent to which the solid is covered by. the liquid in accordance with the requirements for. delivery of the gas.

25. The method of evaporating asolid which comprises immersing the solid in a bath of a liquid and heating the liquid to maintain it at a temperature above its freezing point and above the critical temperature of the 88-8.

2s. The methodas defined in claim 25 inwihich the liquid is a solvent of the gas.

27. The method as defined in claim 25 in which the liquid is a solvent of the gas and additional heat is supplied to the liquid adjacent its evapocovered by the liquid.

HN 'L.

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