US2352775A - Generation of gaseous co2 - Google Patents

Description

chamber 8 of a heater element 9, suc

being connected at its top'by one or more valve- Patented July 4, 1944 l UNITED STATES PATENT OFFICE GENERATION oF GAsEoUs cos Joseph c. Dittmer, st. Albans, N. Y., assigner te National Lead Company,- New York, N. Y., a corporation of New Jersey Appliestien December s, 1939, serial Ne. 303,324`

(ci. (s2-91.5)

14 Claims.

thereof in the form at. present preferred; but.

without limitation thereto.

In this drawing, which isV essentially diagram-v matic, the space marked I symbolizes the place of delivery or consumption of the generated gas and may be taken to be any tank or a carbonating process or other system requiring a continuous or intermittent supply of gas herein referred to as the load demand. c

The gas isfurnished to this process by a delivery line 2, including a. main valve 3 and chamber 4, from a closed reservoir 5. 'I'his reservoir may be of ordinary tank or boiler design capable compartment s is vvertically disposed inside the heater jacket and so relatively dimensioned as to provide a heating chamber of thin annular lsection and relatively small' capacity as compared to the much'larger reservoir. The lower end of the steam compartment depends well below the chamber 8 where it may be provided with, or connected to a compartment extension or sump 'I5which is connected to the waste by a drain line and steam trap I6 as indicated. 'I'he dioxide contents of the heating chamber being normally colder than 32 F., this downwardl extension of the steam compartment aiords the advantage that water condensing out of the steam falls or Yflows quickly out of the cold region be- `fore it can freeze, and into the warmer region below, whence it escapes by the drain. The jet pipe I3. has a drain hole I'I near its bottom so that any water in it, `as on a cessation of the steam supply, may also drainpromptly away. The shape and position of the condensate part of the steam compartment,` whether it includes of pressures of the order of, say, 400 pounds vor less, with an appropriate safety factor and may be large enough to hold, for example, 4000 pounds or more of carbon'dioxide which may be placed therein in solid form, that is, in the form of cakes of dry-ice, indicated at 6. It is closed by a standard manhole cover 'I at its top and is well heatinsulated by appropriate lagging as indicated.

If such insulated reservoir were subject externally only to atmospheric temperatures, the dryice therein wouldv convert to vapor too slowly for practical purposes and heating is therefore necessary. According to this invention .such

. heating is effected by convection to, the reset-- a connected sump as indicated or whether it is directly connected to steam trap, or otherwise, is.

of no special consequence so long as this impor-` tant effect is preserved. Connecting the sumpv to the condensate part of the steam compartment by a narrow conduit, vsuch as suggested at I8, af-

fords an additional safeguard against the freezing of any accumulated condensate because such a connection offers but a small metallic cross- Ysection for the flow of .heat from it to the colder voir contents from a heat source/which is removed from the reservoir. For this purpose the reservoir 5 is included in a circuit with the jacket chamber controlled pipe connections I0 and I l, oi.' ample dimensions, to one or more-points above the bottom of the reservoir, and by a pipe connection I2 with the very bottom of the reservoir.

Any source of heat can be used but steam vis preferred, because' of its convenience and economy, `in which case the heating element 9 is a steam compartment receiving steam from a jet pipe I3 therein under the control of an electric steam valve I! presently referred to.

'parts above.. Still further safety from the `freezing of the condensate may be had by jacketing the sump and connecting the jacket directly t or between the steam supply and the steam trap. so that a small amount of steam will continuously pass through the jacket keeping the sump warm and radiating a slight amount of heat to the uninsulated bottom of the lower or condensate part of the steam compartment directly above it. By A the above. method of steam-heating the carbon dioxide, which is obviously quite independent of vthe nature of the chamber inwhich such dioxide is contained, the danger of stoppage or delay from freezing iscompletely and simply eliminated.

Onv starting up the system, steam-heated gas rises from the chamber 8 into one or-the other or both of the pipe connections. or II, assuming their valves to be open, and flows 'over the dry-ice in the reservoir IWarming it, while cooler 'gas in the reservoir passes into the heater through the bottom connection, thus forming a This steam gas circulation. The heat thus carried by the gas consumption. Any excess from the steam to the dry-ice causes it to sublime more rapidly and increases thereby the pressure in the reservoir. The rate of heat transfer is dependent on the size and temperature of the heater element and to some extent on the dimensions of the circulatory path and these factors can of course be adjusted according to the needs in hand.

For some purposes, the rate of sublimation thus produced might be suflicient to supply the gas required by the process I, but in many c'ases a higher delivery rate is required and to that end, according to this invention, the main valve 3 is kept closed until continued sublimation, under the effect of the circulatory heating, has raised the reservoir pressure to about 70 pounds absolute and the temperature of at least some of the dry-ice, from its natural temperature (about 110 F.) -to a temperature of -69.83 F. at/ which so-called triple-point, the dry-ice begins to melt into liquid carbon dioxide. The heating chamber 8 is installed at a lower level than the reservoir so that the liquid flows into it by gravity and at once, and as soon as this occurs, gas is produced by evaporation in the heated chamber, supplementing that produced by the sublimation and at a much greater rate, the gas circulation being of course interrupted when the bottom pipe I2 becomes 'more or less filled with liquid. Main valve 3 can presently be opened and delivery of gas begun.

This is not done until some selected delivery pressure, above '70 pounds absolute, h-as been attained, say about 200 pounds gauge, and thereafter the application of heat to the vchamber 8 isregulated to evaporate the liquid therein at such rate as to satisfy the load demand and at the same time maintain about that pressure in the reservoir. Such lrate is deslrably so ordered that the temperature of the delivery gas is above 32 F., as this avoids objectionable atmospheric frosting on the delivery line.

The gas may go to the demand directly from the riser pipe 1I I if there is suillcient liquid reserve in reservoir 5, but is preferably ledthrough the tank, as illustrated, so that some oi' its heat may be imparted to the reservoir contents to continue the heating and melting of enough of the remaining dry-ice therein to keep chamber 8 supplied with just suiilcient liquid CO2 for'conervoir as required while maintaining an abundant delivery at about 200 pounds. Under the gas circulation only about 6500 B. t. u'. are exchanged. Since the liquid boils violently in the evaporating chamber at the pressure stated, much of it, according to the principle of the air'. lift, will be carried upwardly to or above and through the connection I 0. Circulation begins at once on opening the valve I0, which valve may then be verting into the' CO2 gas at the desired rate of is unnecessary and undesirable.

This method of continuing the supply of heat to therreservoir contents, after gas circulation has ceased, may suillce to convert gradually all of the remaining dry-ice to liquid and at a vrate required to keep the heater constantly supplied with liquid, but in the event that this rate is not sufilcientiy accomplished, as might be the case', for example, with a very tall and narrow reservoir, a furtherheating means is available, withinthe scope of this inventlon, by opening the chamber connection III which is located at suchv level`as` to be capable of returning liquid dioxide,

warmed by ,theheaten back into the reservoir through which it may then circulate in the same manner as the gas initially circulated.4 Liquid dioxide is a moreenective heat carrier than gaseous dioxide so that the transfer of heat/is accelerated, in fact, increased many fold. For

instance, with a heater element of two feet radiation and steam at 85 pounds, about 400,000 B. t. u.

per hour can be exchanged, with steam flowing' continuously and this will sumce to heat the S- regulated to control the rate of transfer, Thus the reservoir, which is heavily insulated against absorbing heat from atmosphere, is arranged to receive heat from the small chamber either by gas or liquid convection, but only to the extent voper-ation serves to keep any liquid therein so cold that evaporation of such4 liquid is sluggish, and in fact occurs only as the heat insulation leaks atmospheric heat to the interior of the reservoir.

It is possible when there is much cold dry-ice (at o'r about -110 F.) present and the steam has been shut off, for some of the liquid to .freeze again in the reservoir by the heat absorption of the dry-ice in warming up to the equilibrium temperature. Whatever gas is evolved therein as the result of insulation leakage or of heat derived from the evaporatins chamber passes to the delivery line to supply part of the demand.

Chiefiy, the load demand. is carried by the evaporation in the small chamber which, because. of its small capacity, is peculiarly suited to sensitive regulation, by control of the heating medium. 'I'his may be done by graduating the steam admission or by intermittently cutting it in and out as preferred for the case in hand and similarly for any other form of heating medium.

During standby periods when there is no withdrawal for consumption and no refrigeratins effect incident to a falling pressure in the system and perhaps no residual ice in the reservoir to exert a refrigerating effect, excessive reservoir pressure (due to absorption of atmospheric heat)` is avoided and rendered impossible by several means: first, ,by a spring-loaded blow-off or safety valve, indicated, at I9, which is'set to open.

for example, at 325 pounds. A momentary venting of gas by this 4valve checks any rising tendency of the reservoir pressure by stimulating evaporation of the Aliquid therein, and correspondingly chilling the remaining` liquid, so that the pressure is at once restored to a lower value.

In addition to, or 4substitution for, this means of refrigerating the reservoir contents, a mechanical refrigerating unit can be employed, and' is .preferably employed, as represented by the refrigerator coil 20 located within the chamber I connectedin the supply line. This is merely the expansion coil of an ordinary refrigerating unit 2| conventionally shown. By its useithc gas in vthe chamber 4 is condensed and liqueed and returned back to the main body of liquid with of course an attendant lowering of the pressure inthe reservoir, and with no venting of gas. 'l

Final safeguard against excessive pressures in carbon dioxide. Valved connection 23 represents a branch delivery line or a manifold to which other generators lmay be connected and' also a means of exhausting residual gas in order to drop the pressure to atmospheric so that 'reservoir 5 can be opened for refilling.

The coordination of the rate of heating to the voir, thereafter maintaining the liquid'in the reservoir at a temperature adapted to restrain evaporation thereof at said pressure, and-coincirate of gas\delivery s o as to maintain substanl tially constant pressure conditions in the reservoir, is accomplished automatically and preferably by means of two mercoid pressure switches,`

24 and 25, bothconnected by pipe line 26 to the. reservoir or its delivery line 2, to be operated by pressure iiuctuations therein and having appropriate electrical connections as indicated. Pressure switch 24 controls the steam valve il,

through a solenoid `or equivalent motor device, shown as incorporated in the valve, and is ordi. narily set tov close its circuit and open that valve at, say, 200 pounds, and to open its circuit to close the valve at, say, 225 pounds, or as desired. This will sufllce to keep a suiciently constant reservoir pressure for many uses, but the reguto the reservoir until some of the solid dioxide` lation can be set to as close a margin as the pounds;

As thus set, the refrigerating unit will not be likely to be often called into action during normal operation but is available if needed. During overnight or standby periods when refrigeration from residuary dry-ice is insufllcient, it may come more frequently into operation, depending of course on the efficiency of the heat insulation applied to the reservoir.

It may be obse'rved that the system described is competent to produce a controlled delilvery of gaseous carbon dioxide at a constant or variable rate from a reservoir kept always at moderate pressure, not in lany event higher than commonly found in steam boilers and which can be safely accommodated in reservoirs oi commensurate cost. In carbon dioxide gas generators hereto fore commercially used, 'so far as I am aware, the supply reservoirs have consisted Leither of the familiar ,high pressure flasks or cylinders of liquid CO2 of a maximum of 'l5 pounds capacity, or of specially strong and yeryexpensive tanks also of small capacity in which dry-ice has been dently dellveringgas from said heatingchamber to the load demand at a temperature higherthan that of any gas evaporating vfrom said reservoir liquid. 4

2. The method of deriving gaseous carbon dioxide from a reservoir containing` and confining such material in solid form, which comprises rst circulating the gas present with the solid dioxide through a separate heating chamber and back has melted to liquid, and the reservoir then contains both liquid and solid dioxide, then circulating this liquid from the reservoir through a heating chamber vand back to the reservoir thereby carrying heat to the reservoir by liquid convection to melt more of the solid dioxide and,

while thus melting the solid dioxide in the reservoir, withdrawing directly from said chamber thev gas produced by the effect of the heat applied in said chamber.`

3. The method of deriving Agaseous carbon di-- oxide from a reservoir containing thatmaterial in' s olid form, which comprises rst circulating f the gas present in the reservoir through a separate, small heating chamber and back to the reservoir until some o f the solid therein has melted to liquid form, then circulating this liquid from the reservoir, instead f the gas therein, through the same heating chamber and back to the reservoir,thereby transferring heat by liquid convection to the solid therein, and withdrawing gas developed during such liquid circulation to the place of use.

4. The method of deriving gaseous carbon dioxide from a reservoir containing that material in solid form, which comprises first establishing a thermal circulation of the gas present in the reservoir through a separate, small heating chamber and back to the reservoir until some of the solid therein has .melted to liquid form, then establishing a thermal circulation of this liquid through the'samenheating chamber untilmore of the solid has been melted and a desired delivery pressure has been developed in the reservoir, coincidently withdrawing. gas froml the circulatin to satisfy the load demand and in the meantime varying the application of heat to said 'n heating chamber to maintain said reservoir presconfined and caused to sublime or melt, by heat directly applied'to the tanks. In these receptacles the expected pressures are high and variable and the rate of gas generation is not satisfactorily controllable, or the delivered gas is too cold, and the cost in any event is sohigh Aas to be prohibitive for many commercialuses for which carbon dioxide is desirable. The new system herein described and below broadly claimed,

because of its larger reservoir and sensitive evap' circulating carbon dioxide gas or liquid'from such reservoir through a separate steam-heated heat-l ing chamber and back into the reservoir to melt sure during such withdrawal. i

5. The method of deriving carbon dioxide gas fromv a. low pressure reservoir containing carbon dioxide in non-vapor phase which comprises constantly maintainingsuch reservoir by means ofadequate insulation and refrigeration `under desired low temperature and pressure conditions,

any solid carbon dioxide therein, passing liquid carbon dioxide by gravity from the reservoir to the separate heating chamber to gasify it at-a predetermined rate to meet the required demand for gas, and allowing some of the generated gas .to flow into the reservoir.

6. The method ofderiving carbon dioxide gas from a. heat insulated reservoir containing such Amaterial in solid form which comprises heating the reservoir contents by circulating the gas present with the lsolid carbon dio de, through a separate heating chamber and bac into the reservoir until some liquiddioxide forms, then piping the liquid througl' the same heating chamber and reservoir in circulatory fashion, sumcient heat thus being transferred first, to convert some solid into liquid, second, to convert sufllcient of the liquid -into gas in order to build the pressure of the reservoir up to a selected range above 70 lbs.

absolute, and third, to produce suiiicient gas to s, reservoir, means for applying heat to said cham- ,ber, the outlet connection of said chamber including a passage located for returning liquidto the reservoir and another for returning ga thereto.

8. A system for supplying gaseous carbon dioxide comprising a low-pressure reservoir adapted for containing liquid dioxide and entirely encased in a heat insulating jacket and having means in addition to such insulationfor maintaining therein a low temperature at a pressure high enough' to inhibit evaporation at such temperature, a small chamber connected to said reservoir receiving liquid dioxide therefrom, a source of heat applied to said chamber for evaporating the liquid therein, and a gas delivery pipe extending from such chamber to the place ofgas consumption. 9. A system for supplying gaseous carbon dioxide comprising a reservoir adapted for containing liquid dioxide entirely encased in a heat insulating covering and having means in addition to such insulation for maintaining. a low temperatureand a pressure therein of not more than several hundred pounds suited to inhibit evaporation of the liquid at such temperature, a small chamber connected to receive liquid dioxide from said reservoir, a source of heat applied to said chamber to evaporate part of such liquid than such reservoir, piping connecting the kbottoms of said chamber and reservoir, a gas oi!- take from said chamber to the place of use having two branch communications with the reservoir, one at a low point on the latter adapted to\ permit liquid circulation from said chamber back to the liquid in the reservoir, and the other at a higher point adapted to pass heated gas into the reservoir.

12. Apparatus for supplying gaseous carbon dioxide comprising a heat insulated reservoir adapted for containing non-vapor form carbon dioxide and maintained under desired vapor pressures by means of low temperatures adapted to restrain transition to vapor form, an evaporating chamber connected to receive liquid dioxide from therein, a gas delivery pipe from saidchamber and means for returning excess liquid from said cham oer or pipe back-to the reservoir.

.10. A system for supplying carbon dioxide or v'like gas from a reservoir` containing such malike gas from a reservoir containing such ma- 4 terial in non-vapor form, compris g a separate,

small heating chamber disposed a'lower level the reservoir, and means for heating said chamber comprising a steam compartment therein having its lower part extended far enough to the outside of said chamber to avoid freezing of the condensate and a jet pipe for `delivering steam to the compartment. said compartment and iet pipe being both provided with drain communications for water of condensation also located outside said chamber.

13. A system for supplying gaseous carbon dioxide or like gas, comprising a' reservoir adapted for holding such material 1n non-vapor form and lnormally at a temperature less than 32 F., a

small chamber connected in circulatory relation to such reservoir, and means .for applying steam to heat such chamber comprising a vertical oompartment having its upper part-exposedto the temperature of the medium circulating through said chamber, and its lower part extended away `from such chamber, means associated with this steam thereto and for removing condensate therefrom.

14. A system for supplying gaseous carbonf'dioxideor like gas, comprising a reservoir adapted for holding such material in non-vapor form at a normally prevailing temperature of less than 32 F., a small chamber connected to such reservoir to receive liquid dioxide therefrom, said chamber being constituted of a casing. surrounding avertical steam compartment so as to form therewitha shallow, annular passage for the iiow of dioxide, the upper part of said compartment being exposed to the temperature of the dioxide flowing in said passage and its lower part being .extended downwardly from `such passage, means associated withl this lower part -ilor maintaining it at a temperature above 32 F., means for causing a hot vapor to ascend in said compartment and means in the lower, warmer part of said compartment for collecting the vapor condensate.

JOSEPH cfnrrriunaza.v

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