US2641450A

US2641450A - Method of transferring heat by a powdered thermophore in a state of dense phase fluidization

Info

Publication number: US2641450A
Application number: US704416A
Authority: US
Inventors: Paul W Garbo
Original assignee: Hydrocarbon Research Inc
Current assignee: Hydrocarbon Research Inc
Priority date: 1946-10-19
Filing date: 1946-10-19
Publication date: 1953-06-09
Anticipated expiration: 1970-06-09

Description

June 9, 1953 P. w. GARBO 2,641,450

METHOD OF TRANSFERRING HEAT BY A POWDERED THERMOPHORE IN A STATE OF DENSE PHASE FLUIDIZATION Filed 001;. 19, 1946 2 Sheets-Sheet 1 INVENTOR. faui 2 7 [iarfia Patented June 9, 1 953 LIETHOD OF TRANSFER/RING HEAT BY A POWDERED THERMOPHORE IN A STATE OF DENSE PHASE FLUIDIZATION Paul W. Garbo, Freeport, N. Y., assignor to Hydrocarbon Research, Inc., New York, N. 1., a corporation of New Jersey Application October 19, 1946', Serial No. 704,416

13 Claims. 1

This invention relates to a novel process of transferring heat or cold from one gaseous medium to another. The term gaseous medium is used in a broad sense, to include gases and vapors.

Two procedures have heretofore been chiefly used for the transfer of heat or cold from one gaseous medium to another. One procedure involves the alternate flow of the two gaseous media over a stationary bed of heat or cold absorbing material; during one eriod of operation this bed is either heated or chilled by the gaseous medium flowing thereover, and during a succeeding period of operation the heat or cold content of the stationary bed is removed therefrom by the other gaseous medium flowing thereover. The well-known regenerator exemplifies this method of transferring heat or cold from one gaseous medium to another. The other conventional method involves the simultaneous flow in indirect heat exchange relationship of the two gaseous media to effect a transfer of heat or cold from one to the other. The well-known recuperator exemplifies this method of transferring heat or cold from one gaseous medium to another. In both of these methods, in order to obtain relatively high heat or cold transfer efliciencies',r

it is important to use a maximum of heat or cold absorbing surface area per unit of volume through which the gaseous media flow. 'Thus, for example, in one type of cold exchanger suggested for recovering the cold content of the outgoing oxygen and nitrogen products of rectification formed in the liquefaction of air to produce oxygen, which products may be at a temperature of'about 280' F., it has been found desirable to use passages, through which the oxygen, nitrogen and air flow in cold exchange relationship, of relatively small cross-sectional area, which passages are provided with closely spaced fins of foil-like metal'of high heat conductivity to provide a high surface "area of cold exchanger surface per unit of volume of exchanger space.

It is an object of this invention to provide a method of transferring heat or cold from one gaseous medium to another, in which the eifective heat or cold exchanger surface area per unit of volume of exchanger is materially greater than in prior known procedures.

Another object is to provide such process of exceptionally high heat or cold transfer efficiency and which process requires relatively simple equipment for its practice.

Other objects and advantages of this invention will :be apparent :from the following detailed description thereof.

In accordance with this invention, a stream of powdered thermophore is passed through a multiplicity of longitudinally extending channels in one zone in a generally downward direction and in a state of dense phase fluidization, countercurrent to a stream of gaseous medium from which heat-or cold is to be abstracted, the gaseous medium maintaining the thermophore in the aforesaid state of dense phase fluidization, so that, inefiect, each solid particle of thermophore is vigorously agitated by the gaseous medium,.thereby insuring intimate contact be-- tween the powdered thermophore particle and the gaseous medium and promoting maximum heat or cold exchange therebetween while maintaining temperature gradients in opposite directionsthroughout the streams of gaseous medium and thermophore. Thus, for example, if the temperature gradient in the thermophore stream ascends, the temperature gradient in the gas stream descends, and vice versa. From this first zone, the thermophore stream is passed through a multiplicity of"long"itudinally extending channels in a second zone, countercurrent to a second gaseous medium, while maintaining temperature gradients 'in opposite directions in the two streams stream in 'a state of dense'phase fluidiz'at-ion.

The character" of the temperature gradient, i. 'e., whether ascending or descending, in each-of the two zones will depend on whether the process is used to abstract heat-or cold from one fluid medium and transfer it to another medium. All

references herein to the character of the gradient are .in terms .of the direction of flow of the medium in question. For examplein the practice of this invention for recovering the cold content; of the oxygen and nitrogen products of rectification in the liquefaction of air to produce oxygen, nitrogen or oxygen or both may be passed upwardly through the first zonein cold exchange relationship with a down flowing stream of thermophore in a state of dense phase fluidizatio-n, soas to main'tainan ascendingftempemture gradient in the gas stream and'a descending temperature gradient in the thermophore stream, and'the' thus c'hilled thermophore passed downwardly in a state of dense phase fluidization. in countercurrent relationship to an lip-flDWing air strea-rn'in the second zone so as to maintain an ascending temperature gradient in the thermophore stream andadescending temperature gradient in the' air stream.- On the other hand,

"and maintaining the thermophore:-

temperature gradient maintained in the gaseous stream passing through'the second ZOIle and a descending temperature gradient in the thermophore stream passing through the second zone.

By thermophore is meant a comminuted solid material of high heat absorbing and heat transfer capacity. It is advantageous in the practice of this invention that the thermophore be in the form of a powder, substantially all of which passes a 100 mesh screen. For best results, the powder will usually contain at least 85% of particles passing through a 200 mesh screen and contain particles as small as 400 mesh or smaller. The particle size in any given system will depend upon the density of the material of the particles. the shape of the particles, the density and velocity of the gaseous fluidizing medium, etc.; the optimum particle size for any such system is readily determinable by simple preliminary experiments conducted under conditions simulating those of actual operation.

The material used as the thermophore will depend upon the particular application to which the invention may be put. Thus, for example,

in the recovery of the cold content of the oxygen and nitrogen products of rectification in the liquefaction of air to produce oxygen, a material of exceptionally high heat absorbing and trans fer capacity should be used. Copper, aluminum and other metals and alloys of high heat absorbing and transfer capacity will be found eminently satisfactory for this purpose. If the process is employed to transfer heat at high temperatures from one gaseous medium to another, ma-

terials of high heat absorbing and transfer cau per surface of the bed or mass a sumes a level substantially above the normal level of the settled thermophore, which level is commonly known as a pseudo-liquid level.

During the flow of the gaseous medium through the bed or mass of thermophore in each of the zones, the individual particles rise and fall, the general direction of movement of the part cles, however, being downwardly so that as the operation of the process progresses, fresh incoming particles of thermophore form the upper surface of the mass and these particles gradually progress downwardly until they reach the exit, where they are withdrawn.

This state of fluidization, in which the particles are maintained in a vigorous and intense state of agitation, i. e., in a condition resembling boiling, with the upper surface of the mass or bed thereof substantially above the normal level of the settled thermophore, is herein designated [as dense phase fiuidization.

The process of this invention is particularly applicable to the recovery of the cold content of oxygen and nitrogen products of rectification in theliquefaction of air in the production of oxygen. However, the invention is not limited to this application but ha numerous other applications, such, for example, as the transfer of heat fromone fluid medium to another. Thus, it may be employed to transfer heat from synthesis gas to the gaseousreactants. For example, oxygen and a mixture of steam and natural gas may be heated by the heat removed from the carbon monoxide and hydrogen synthesis gas produced therefrom, or the invention may be employed to abstract heat from line gases or other products of combustion or waste gases and transfer this heat to any desired medium, for example, to preheat air used to support combustion or to superheat steam.

In the accompanying drawings forming a part of this specification and showing, for purposes of exemplification, preferred forms of apparatus for practicing this invention: M

Fig. 1 is a layout of equipment for recovering the cold content of oxygen and nitrogen products of rectification in the liquefaction of air to'pro duce oxygen;

Fig; 2 is a preferred layout of equipment for practicing the process of this invention in effect ing transfer of heat from synthesis gas to the gaseous reactants;

Fig. 3 is a horizontal section through a rectangular chamber and shows one arrangement of partitions forming longitudinal passages or cells;

Fig. 4 is a horizontal section through a cylindrical chamber showing a modified arrangement of longitudinally extendingpassages or cells;

Fig. 5 is a horizontal section through a rectangular chamber showing a third-arrangement of longitudinally extending passages or cells; I

Fig. 6 Ba horizontal section througha cylindrical chamber showing still another arrangement of longitudinally extending passages or cells; and

Fig. '7 is a modified form of apparatus for prac ticing this invention in which apparatus the chambers are arranged in side by side relation-. ship rather than superimposed relationship as in the modifications of Figs. 1 and 2.

Fig. 1- of the drawing shows a chamber I I), having a conical base ii, the chamber being provided with a gas inlet I2 at the apex of the conical base H. A plurality of closely spaced partitions l3 are disposed within chamber Hi to divide this chamber into a multiplicity of longitudinally extending passages i3, which substantially prevent top-to-bottom intermingling and mixin of the thermophore, such as would interfere with the maintenance of the desired temperature gradient in the mass of thermophore particles passing through chamber ID, as hereinafter described. As hereinafter more fully disclosed, partitions I 3 may be in the form of tubes, parallel partitions or intersecting partitions forming longitudinally extending cells or passages of any desired cross-sectional configuration. These longitudinally extending passages l3 may be elliptical, circular, square or other polygonal shape in cross-section and should be so dimensioned that they have an effective size of a pipe having an internal radius falling within the range of from about A to about 2", preferably from to about 1". Thus, if a passage has an effective 5 pipe size corresponding to an internal-radiusof say 1/ no thermophore particle will be spaced from a wall by a distance more than 2 and thedistance between a -:thermophoreparticle and the wall farthest away will be 1''. With the partitions spaced within the range above indicated, and passing a gaseous medium therethrough at a suitable velocity, readily determined by trial, depending on the density and particle size of the thermophore, intermingling of the thermophore particles is prevented from top to bottom of the passages to an extent 's'ufiicient to maintain desired temperature gradient conditions.

Chamber I is provided with an exit pipe 14 communicating with a filter, "cyclone separator "01' other dustremo vin'g device 1 5, through which the gaseous medium passes, the device 1'5 removing substantially all entrained thermophore particles carried by the gaseous stream. This chamber is also provided with an inlet pipe l6 extending below the pseudo-liquid :level H of the thermophore particles and a sta'ndpipe I8 flow through which is controlled by slide valve I8A or its equivalent. A line 1 8' leads from the main nitrogen line 41 into standpipe 18. Valve 1'8" regulates the flow of nitrogen through pipe 18; this valve being adjusted to provide a'nitrogen fiow sufiicient to maintain the thermophore particles passing through 18 in a free flowing condition. I V

In the embodiment of the 'inve'ntien shown" in the drawing, the partitions I 3 are desirably tapered in cross-section to form channels '13" also tapered in cross-section, i; e., channels l3 have 'a varying cross-sectionalarea, the crosssectional area at the top being greater than that at the bottom. Hence, the volumetric space of the channels per unit length thereof progressively increases from bottom to top, thereby compensating for gas expansion with increase in the temperature of the gas stream flowing upwardly there'through. If chamber I0 were used as the heating zone 'for the thermophore, the taper of the partitions would be reversed so that the channels defined thereby'would have their great-.

est cross-sectional areas at their bases.

A second chamber 2!] is provided similar in construction to chamber 10, except that the partitions 21 therein taper from top to-bottom rather than from bottom to top, so that the cross-sectienal area of the cells or longitudinal passages 22 formed by these partitions decreases from bottom to top to compensate for the decrease in volume of the gas stream passing therethrough, due to its decrease in temperature. This chamber is provided with a filter, cyclone separator or other dust-removing member 23 communicating with a gas exit pipe 24. A gas inlet pipe 25 at the base of this chamber'communicates with the conical portion 26. A thermophore exit pipe 21 having a regulating valve 21A therein,

discharges into a main 28 through which the.

thermophore is carried in suspension in a high velocity gas stream, e. g., some of the nitrogen leaving vessel It) by way of pipe I4 may be used for this purpose, to the inlet pipe 16 dipping below the pseudo-liquid level in chamber I 0. Pipe l8, supplying the thermophore withdrawn from chamber ID' discharges the thermophore at 29 below the pseudo-liquid level '30.

In the embodiment of the invention shown on the drawings, a bank of tubes 3| is-disp'osed Within chamber H) for flow of oxygen therethrough to recover the cold content of the outgoin'g' oxyg'e'n product of rectification, along with the cold con would be used. The bank of tubes 3|, or .a 'sim- I ilar bank 'of tubes disposed in chamber '20 may be employed for the purpose of having. an external refrigerant, such as ethylene, passed therethrough to introduce into the processan amount of cold adequate "to compensate for cold lossesresulting from the difference in "enthalpy between the air introduced into-and the products of rectification withdrawn from the process, and

for heat leaksinto the system. Thebank-of tubes 3| is preferably of-a metal'of high heat conductivity; copper is a "satisfactory material of con-- struction.

The-rectification system with which the exchanger of this invention may b-e-employed', when used "for recovering the cold content of oxygen and nitrogen products of rectification in the liquefaction of air to produce oxygen, comprises,- for example, a two-stage rectification column 32, the lower section 33 of which is operated at a pressure of about '72 pounds gauge and the upper section 34 of which is operated at a pressure of from about 4 to about 10 pounds gauge, prefer: ably at about 5 poundsg'auge. This column, as iscustom'ary, is provided with rectification plates of the. bubble cap'or'other desired type. The lower section 33' of the column 32 communicates with a condenser 3 5'and hasa liquid collecting shelf 33 disposed immediately below the condenser 35 for collecting liquid nitrogen. Pipe-31 leads from this shelf 36 to a heat exchanger 38, which in turn communicates through a pressurere'ducingvalve 39 with the top portion of the upper section 34. Condenser 35 acts-as a reboiler for the upper section 34 of the column 32.

From the base portion of the lower section 33, a pipe line .40 for the flow of crude oxygen (containing approximately 40% oxygen) passes to a heat exchanger 4| which communicates through pipe line '42 having a pressure-reducing valve 43 therein, with the low-pressure section 34 at an intermediate point 44. A line '45- having a pres sure-reducing valve '46 therein leads from condenser 35 to a nitrogen line 41 communicating by way'of heat exchanger "54 with the inlet l2 to chamber l0. A line 48 leads from the top'of low-pressure section 34 to the heat exchanger 38, the nitrogen flowing through this line passing through the heat exchanger 38, then through line 49 and heat exchanger 4 into line 50 which communicates with line 41. Oxygen line 5| leads from the lower part of the low pressure section '34 to the inlet 52 of the bank of tubes 3| disposed within chamber i 0,'this bank of tubes being provided with an exit line 53. As above indicated, the bank of tubes in chamber 1'3 may be omitted, in whichcase the oxygen line 5| may communicate with an exchanger independent of cham ber H].

Pipe 24 has two branches, one identified as '24 leading through heat exchanger 54to lower section 33 and the other identified by 51 communicating with branch line. '58 having valve 58A therein leading through a tube '59 disposed within chamber 28 and thence through line to which joins line 51 having valve til-A therein at 61. From 61, line 51 enters ex ander 61" which dis-- charges through line 62 into low pressure section 34.

The heat exchangers 38, III and 54 and the two-stage fractionating column 32 may be of any conventional type. Two separate fractionating columns suitably interconnected maybe used in place'of the two-stage column 32 shown. It will be understood that'the equipment throughout, including chambers I9 and 2t and all piping connections, is heat insulated to minimize. loss of cold.

Chambers I and 28 may be square-shaped in section, as shown, for example, in Figs. 3 and 5, or cylindrical as shown in Figsp i and 6. The longitudinally extending channels I3 and 22 may be shaped as shown in thesefigures. In Fig. 3 these channels are defined by

partition walls

63, 64 at right anglesto each other forming substantially square-shaped channels. Alternatively, the channels or passageways may be defined by a cylindrical outer wall 65 having a plurality'of concentric inner walls I56, 61, 68, 69, III and II defining annular channels. Radial partitions I2 are provided in these annular channels to form longitudinallyextending passageways of the desired cross-sectional extent, i. e., having an effective pipe size, the internal radius of which is within the range of from about to about 2", preferably from about A2" to about I".

Fig. shows still another arrangement of longitudinally extending passages in which longitudinally extending cylindrical-pipes I3. are arranged in the pattern shown withina'irectangular housing toprovide cylindrical, longitudinallyextending passageways I4 defined by the inner walls of the pipes and longitudinally extending passageways: I5 of somewhat larger cross-sectional extent, defined by the outer walls of. the pipes as well as a series of triangular shaped-longitudinally extending passageways I6 defined by the outer walls of a pair of pipes contiguous to the inner wall of the rectangular housing. The modification of Fig. 6 involves a cylindrical housing TI cooperating with cylindrical pipes I8 disposed therein and longitudinally extending bafiles or partitions I9, 89, bafiles '19 and 8!} being at right angles to each other and cooperating with the pipes I8 to define longitudinally extending passageways 8i, 82. It will be understood that Figs. 3 to 6 represent a few of the many possible arrangements of partitions to form longitudinally extending passageways for flow of fluidized thermophore therethrough under conditions such that desired temperature gradient conditions are maintained.

If desired, longitudinally extending passages in any of the modifications hereinabove described may be arranged in two or more groups. Thus, for example, in the modification of Fig. 5, some of the pipes 13, say the corner pipes 73A of each rectangular arrangement of eight pipes, may be used for flow of oxygen therethrough in lieu of the separate bank'of tubes corresponding to bank 3i in *Fig. 1 while'the remaining longitudinally extending passages within the chamber are used for the upward flow of nitrogen and the downward. flow of thermophore.

The arrangement of the apparatus of Fig. 2 is particularly designed for recovering the heat content of synthesis gas and imparting this heat to'the reacting gases; This equipment involves a chamber 83 having partitions 86 therein to form longitudinally extending passages 85. These longitudinally extending passages may be of any of the shapes hereinabove disclosed in connection with Figs. 3 to '6 inclusive. Chamber 83 has a conical base 86 from which lines 87, 88 lead to

chambers

89, 90. Lines 8'! and 88 are provided with slide valves SH, 92', respectively. Chamber has at its base a gas line 93 for introduction thereinto of a methane and steam mixture; this chamber is of greater volumetric capacity than chamber 89 and has therein partitions 9d forming longitudinally extending passages 84'. Chamber 89 has partitions 95 forming longitudinally extending passages 96 and has at its base an oxygen inlet line 91.. These longitudinally extending passages, as hereinabove disclosed. may be of any desired cross-sectional configuration.

Conical

base portions'of chambers

89 and 99 are provided with thermophore discharge lines 98, 99, respectively, which lead into a common line I00 communicating with the upper portion of chamber 83. Rotary valves IOI, I02 are provided in the lines 98, 99, respectively. The rotary valves IOI, I92, and the slide valves 9!, 92 may be of any well-known type. If desired, all rotary valves may be employed or all slide valves, thefunction of these valves'being to permit flow of thermophore through the lines in which they are disposed without unduly disturbing the pressure conditions in the chambers with which these lines communicate. I

Each of the

chambers

83, 89 and 91! is provided with a filter or other dust-removing device I93. Filter we in chamber 83 has leading therefrom a discharge pipe- Illd. A line I05 leads from filter element I 53 of chamber 89 and lineIIlE leads from filter element I93 of chamber 90, the lines I95 and I06 entering a reactant nozzle IG'I disposed in the base of reaction chamber I 98. Synthesis gases leave reaction chamber IIIB through line I09 leading into the conical base portion of chamber 83.

The modification of Fig. 7. involves chambers III], III arranged in side-by-side relationship instead of superimposed relationshipas in the modifications of Figs. 1 and 2. As in the case of the othermodifications hereinabove disclosed, the top of each chamber I I 9, I I I is provided with a filter or a dust-removing device I I5 from which lead the gas exit pipes II 6, III. The conical bases of chamber IIfi,- I II are provided with gas inlet lines I I8, H9 and thermophore withdrawal lines I 20, HI in which rotary valves I 22, I23 are disposed. A conveyor I24 leads from the rotary valve I22 for flow of the thermophore into container I25 communicating through rotary valve I 29and line I21 with the chamber II I. Conveyor I28 leads from rotary valve I23 to chamber I29 communicating through a line Isl having a rotary valve I32 therein with chamber IIB.

Each chamber III), I II has longitudinally extending channels or passageways I I 2 interrupted laterally at II3, IIfl by narrow spaces which should be less than 12" wide, preferably about two inches wide. These lateral spaces function to equalize flow conditions through the several streams of thermophore, each in a state of dense phase fiuidization passing through the channels I I2. The interrupted channels [I2 in chamber IIQ are defined by walls I35, I36, I37 of different thickness, the thickest walls being at the top of chamber H9, and the thinnest at the base, so that the cross-sectional area of the channels is smallest at the top and largest at the base, thereby compensating for volume decrease due to temperature decrease of gas flowing upwardly throughchamber IIQ, In chamber III the thickest wall [as is at the base, the thinnest wan Isa direction of gas flow upwardly through chamber-' Ill to accommodate increasing gas volume due to rising temperature. It will be understood any desired number of wall sections in the chamber may be used to define interrupted, longitudinally extending channels having the cross-sectional area thereof gradually increase or decrease to provide for optimum flow conditions. It'will be appreciated the arrangement-of Fig. '7 provides an alternative method of obtaining substantially the same effect as the tapered walls [3 and 2t in chambers l and 20-, respectively, and that either of these modifications may be employed. in forming the longitudinally extending channels in chambers 83-, 89 and 9B of Fig. 2. In heat exchange procedures in which the volume change in the gas flowing through the channels is notlarge, channels of substantially uniform cross.- sectional area from top to bottom of the exchanger may be employed.

Example 1' The following example is illustrative of theoperation of the process of this invention in re-' covering the cold content of the outgoing nitrogen and oxygen products of rectification in the liquefaction of air employing powdered copper as the thermophore. It is to be understood the inventionlis not limited to this example.

All temperatures herein given are in degrees F. and pressures are in pounds per square inch gauge.

. Air at a pressure of about 75 pounds gauge and a temperature of 100 F. is admitted through line 25 at a rate suflicient to maintain the powdered thermophore circulating through the longitudinall extending channels 22 in chamber 2'0, constituting zone 2 of the process, in a state of densephase fluidization. The temperature of the air. as it flows countercurrent .to the thermopho're stream gradually decreases to 2'73 F. at the point the air leaves the pseudo-liquid level '30. The thermophore stream enters at a temperature of 276 F. and flows downwardly through the longitudinally extending passages 12 in chamber 20 in a state of dense phase fluidization, the

temperature'thereof gradually increasing to 98 F. at the point where the stream leaves chamber 20 and is passed through main 28 by a suitable conveyor gas, for example, nitrogen,. into the chamber I0. Most of the air (say 80% by volume) from chamber 20 at a temperature of -2'73 F. flows through heat exchanger 54 in heat-exchange relation with nitrogen and enters high pressure section 33 of column 32 at a temperature of -2'75" F. and a pressure of about 72 pounds.

Y Crude oxygen at a temperature of -278? F. and pressure of 12 pounds leaves the'base-of column section 33' through line 40, flows through heat" exchanger 4! where .its temperature is reduced to -286 F. and upon flow through the pressure reducing valve 43 is flashed, enterin lowerpres sure column section 34 at a temperature of 310;' Pure to -315 F. and a pressure of pounds. oxygen is withdrawn through line 51 at a temperature of -292 F. and a pressure of 5 poundsand flows through bank of tubes 3| in the cham- 1'0 bank of tubes at a temperature of 90 F. at a pressure of about 1 pound.

Nitrogen at a temperature of about -286 F. and. a pressureof 12 pounds is withdrawn through line 45 and passes through valve 46, its temperature being reduced to atemperature of about -3l5 F. as a result of the expansion through the pressure reducing valve '46. Nitrogen at a temperature of 3l5 F. and a pressure of 5 pounds is withdrawn through line 48 and flows through heat exchanger 38, where its temperature is raised to about l F. The nitrogen flows from heat exchanger 38 through heat exchanger 4! and mixes with that in line the nitrogen stream thus produced at a temperature of -294 F. flows through line 41, into heat exchanger 54 where the temperature of the nitrogen is raised to -278 F. The'nitrogen at this temperature and a pressure of about 5 pounds enters inlet I2 to chamber Ill.

The nitrogen flows upwardly through the longitudinally extending passages 13 maintaining the thermophore powder in a state of dense phase fluidization, the nitrogen leaving through exit line 14 at a temperature of about 95 F. Thus an ascending temperature gradient is maintained in the nitrogen stream flowing through chamber ll] constituting the first zone of the process. The thermophore particles enter this zone at a temperature of 98 F. and leave through pipe I8 at a temperature of approximately -276 F., a descending temperature gradient in the direction of the thermophore flow being maintained in the stream of thermophore passing through this zone, which temperature gradient it will be noted is in the opposite direction from that maintained in the nitrogen stream passing through this zone.

Any known procedure may be used for compensating for heat leaks and cold losses resulting from the difierence in enthalpy between the air introduced into and the products of rectification Withdrawn from the system. The preferred method is shown in Fig. 1 and involves the diversion of a minor portion, say 20%, of the cold air from line 24 to pipe 5'! controlled by valve 51A and discharging into expansion engine or turbine iii. A minor portion, say 10%, of the diverted air is warmed by passage through pipe 58" controlled by valve 58A and through heat ex changer 59 disposed in the fluidized mass of vessel 20. This warm air flows through pipe 60 and mixes with the air stream in pipe 5? before it enters expander 6|. .In this manner, the air originally at a temperature of 273 F., as discharged intopipe 24,-is warmedup to a tempera ture of about -235-" Fflbefore expansion to increase-the amount of refrigeration produced. Thev air expanded from a pressure of about 72 pounds to a pressure of about. 5 pounds attains a temperature of about -305 F. and fiows through pipe 62' into low-pressure section 34 of column 32.

. It will be noted from theabove example that the thermophore enters chamber 26 at a temperature of +276 F., whilethe air stream leaves th1s chamber at a temperature of 273 F.; thus the temperature approach at the cold endof this chamber is 3 F. The .thermop'hore leaves chamber H] at a temperature of 276- F., whereas the nitrogen entering this chamber is'at a tem perature of 278 F., the temperature approach at the cold end of chamber lflistherefore 2 F.

The air; before introduction intochamberiil; I

should betreatedior removal of moisture and carbon dioxide to avoid deposition otfrost andsolid carbon dioxide in the cold exchanging chambers which would interfere with their operation. Any known treatment for effecting removal of moisture and carbon dioxide may be used for this purpose, for example, the air may be scrubbed with caustic soda, or other chemicals, to remove the carbon dioxide.

The production of oxygen maybe carried out in equipment of the type disclosed in Figure 2 involving two separate chambers for the flow of oxygen and nitrogen products of rectification, respectively, therethrough in cold exchange relationship with thermophore streams each in a state of dense phase fluidization. Thus the nitrogen stream may be introduced through line 93 and pass upwardly through the longitudinally extending channels in chamber 90, while the oxygen stream is introduced through line 97 and passed upwardly through longitudinal channels in chamber 89, the oxygen stream entering at a temperature of about 292 F. and a pressure of 5 lbs. and the nitrogen stream at a temperature of 278 F. and a pressure of about 5 pounds. Thermophore streams each at a temperature of about 98 F. fiow downwardly countercurrent to the rising oxygen and nitrogen streams and leave the base of

chambers

88 and 90 at a temperature of approximately 290 F. and -273 F., respectively. Thus the temperature approach at the base of

chambers

89 and 90, where the oxygen and nitrogen streams, respectively, enter and the thermophore is withdrawn, is about 2 F. in case of chamber 89 and about 5 F. in the case of chamber 90. The combined thermophore stream at a temperature of -276 F. flows downwardly in a state of dense phase fluidization through the longitudinal channels 85 in chamber 83 countercurrent to a rising stream of air which may enter at a pressure of about '75 lbs. gauge and a temperature of 100 F. and leave at substantially the same pressure and a temperature of 273 F. through line I 2. The temperature approach at the top of chamber 83 where the refrigerated air stream leaves, it will be noted, is approximately 3 F. In chamber 83 an ascending temperature gradient is maintained in the thermophore stream while a descending temperature gradient is maintained in the air stream; in

chambers

89 and 90 descending temperature gradients are maintained in the thermophore streams and ascending temperature gradients in the oxygen and nitrogen streams, respectively. I

In the operation of the equipment of Figure .7, nitrogen at a temperature of about 278 F. and a pressure of 5 lbs. may be admitted through line I I9 and passed upwardly through the longitudinally extending channels H2 in chamber Ill, leaving at H! at a temperature of approximately 95 F. A thermophore stream in a state of dense phase fluidization flows downwardly through channels H2 in chamber Ill entering this chamber at a temperature of 98 F. and leaving at a temperature of approximately 276 F. The thermophore stream at this temperature is withdrawn through valve I23 from which it is elevated through conveyor I28 to compartment i29 communicating through valve [32 with chamber H0. The thermophore stream at a temperature of about 2'76 F. in a state of dense phase fluidization flows downwardly through the longitudinally interrupted channels H2 countercurrent to a stream of air which enters through line H8 at a temperature of about 100 12 F. and a pressure of about '75 lbs. and'leaves through filter H5 and line H6 at a temperature of about 273 F. and substantially the same pressure. Thus a descending temperature gradient is maintained through the air stream passing upwardly and an ascending temperature gradient through the thermophore stream passing downwardly through chamber H0 and an ascending temperature gradient is maintained in the nitrogen stream passing upwardly and a descending temperature gradient in the thermophore stream passing downwardly through chamber HI.

Example 2 The following example is illustrative of the operation of the process of this invention in recovering the heat content of synthesis gas (H2+CO), using powdered silicon carbide (Carborundum) as the thermophore:

The reactants used in this example are oxygen of 98.5% purity, steam and natural gas having approximate composition by volume as follows: methane 82%; higher hydrocarbons 9%; hydrogen 7%; residuals, nitrogen, carbon dioxide, etc., 2%. A stream of two volumes of natural gas and one volume of steam is introduced through 93, countercurrent to the fluidiz ed thermophore flowing through channels 94 in chamber 90. The oxygen flows through line 91 countercurrent to the thermophore flowing through channels 96. The oxygen and methanesteam mixture are preheated by external means (not shown) to a temperature of about 530 F. at which temperature the gaseous reactants enter

chambers

80, 90. They leave these chambers at a temperature close to 2300 F. at which temperature they enter reaction chamber I08, which is under pressure of approximately 200 pounds per square inch gauge. Synthesis gas leaves this reaction chamber at a temperature of about 2300 F. at which temperature it enters base of chamber 83, flowing upwardly through the fluidized thermophore, passing downwardly through the channels 85 therein. The synthesis gas leaves through line I04 at the top of chamber 83 at a temperature of approximately 550 F. The thermophore enters the top of chamber 83 through line 96 at a temperature of approximately 540 F. and leaves the bottom of chamber 83 through

lines

81, 88 at a temperature close to 2300 F.

An analysis of the synthesis gas is as follows: 59.2% by Volume hydrogen, 29.9% C0, 7.8% CO2, 2.1% CH4, the remainder being chiefly nitrogen.

It will be noted that the thermophore leaves chamber 28 in the modification of Fig. 1 and the

chambers

89, 90 in the modification of Fig. 2, at a temperature closest to atmospheric, at which temperature it is transported to the chamber In in the modification of Fig. 1 or chamber 83 in the modification of Fig. 2. Thus the thermophore is moved from one chamber of the process to the other at a temperature closest to atmospheric, with consequent minimization of heat or cold losses.

It will be further noted the process of this invention involves the flow of a fluidized stream of comminuted thermophore through a plurality of heat or cold exchange zones through each of which flows a stream of gaseous medium in a direction countercurrent to the thermophore stream, while maintaining temperature gradients in opposite directions in the thermophore and gaseous streams passing through each zone.

The use of a powdered thermophore in a state of eng ne dense-phase fluidization provides exceptionally high surface areaof'heator cold absorbing ma-- terial per unit of volume of exchanger space, and exceedingly intimate contact between the gas and the thermophore. The turbulence of the thermophore particles promotes high rates Of heat transfer. This insures optimum removal of heat or cold from'the gaseous mediurn'passing through one zone and the most efficienttransfer thereof to the gaseous medium passing through the second zone. With this invention, it is feasible to maintain a temperature approach between the air leaving, for example, chamber 20' in the modification of Fig. 1 and the nitrogen entering chamber in as low as 2 or 3 F.

This compares with a temperature approach.

of the order of F. or at best 6 to 8 F. obtained in prior processes, and demonstrates the improved efliciency of the. process. of this invention- Since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not ina limitingsense. Thus, for example, while Fig. l of thedrawing discloses a single chamber for either heating or cooling the thermophore, it willbe understood that two or more of such chambers may be employed in series.

Nhat is claimedis: V

l. The method of transferring heat from. a stream of air to a stream of a product of rectification in the liquefaction and rectification of air, which comprises circulating apowdered thermophore' downwardly-through aplurality of longitudinally extending channels arranged in parallel in a first zone countercurrent to said stream of a product of rectification rising at a velocity which maintains said thermophore in said first zone in a state-of densephase fluidization, each of said channels having an effective size of a pipe having an internal radius in the range of about /4- inch toabout 2 inches which substantially prevents 'top-to-bottommixing of saidthermophore' within the channel, thereby maintaining an ascending temperature gradient in the rectification product stream and'a descending temperature gradient in the thermophore-stream passing through said first zonewhereby theathermophore stream leaves said first zone at substantially the. temperature at whichthe rectification product stream enterssai'd fi'rsthone, circulating said thermophore from the lower end of said first zone downwardly through a plurality of longitudinally extendin channels arranged in parallel in a second zone countercurrent to said stream of air rising at a velocity which maintains said thermophore in said second zone in a state of dense phase fluidization, each of said channels having an effective size of a pipe having an internal radius in the range of about inch to about 2 inches which substantially prevents topto-bottom mixing of said thermophore within the channel, thereby maintaining a descending temperature gradient in the air stream and an ascending temperature gradient in the thermophore stream passing through said second zone whereby the heat content removed from the air stream in said second zone by said thermophore is imparted to the rectification product stream, and circulating said thermophore from the lower end of said second zone downwardly through said first zone as aforesaid.

T4 The--method as defined in claim. 1,.in= which the channels have an efiectivesize o'fi a pipe having an internal radius falling 'within the range of about one-half inch to about an inch.

3. The method as definedL'i-n. claim 1, inw-hich. the rectification product stream is predominantly nitrogen and enters said-first zone at a temperature of approximately --280 F';, and'the air stream enters saidsecond zone: aha-temperature of approximately 100 F.

4. In the method oftransferring heat from one gaseous medium'to-another wherein one gaseous medium-is passed upwardly through a mass of powdered thermophore in a. state of dense phase fluidization, another gaseous medium is passed upwardly through another mass. of. saidthermophore in a state. of dense. phase fluidization, and. said thermophore is. circulated .betwen. the '-tw0= said masses, the improvement whichcomprisesdividing each of. the two said masses in a plu-"- rality of longitudinally extending channels ar-= rangedin-parallel, each of said. channels having; an efie'ctive size oixa pipe having an. internal radiusifallingwithinthe range of from about A;- inch. to. about 2- inches, andmaintaining tem-a perature gradientsin: opposite directions along.-

thevertical. dimension of the'two said masses in a pluralityxof longitudinally extending channels 5. The method as definedin claim..4, in which the. horizontal cross-sectionzof eachof the longitudinally; extending channels gradually; increasesim the direction of increasing: temperature.-

v6; The'method as defined in'claim 4,. in which. the powdered: thermophore: is of: a particle sizev suchthat substantially all passesthrough a 100 mesh screen and at least thereof passes through:a200meshscreen= .f g H 7.;The method of transferring heatbetween a single gaseous stream and: twoseparate gaseous streams having substantially the same i-nitial temperature, which comprises circulatin f apowdered thermophore downwardly through; a: plu ralityof longitudinally extending, channels ,arranged in parallel in anfirstzone countercurrent tosaid single stream rising at a velocitywhich maintains said thermophore in said. first zone in; a. state of dense phase fluidization, each ofsaid channels having. aneffectiversizeof apipe having; an internal radius.- in the range Of.9;b0l1t /4jinch; to about 2'. inches; maintaining. in said first-zone; tem erature gradients in j opposite directions in said thermophore: andflin said. single stream; .cir-e. culatingsaid. thermophore; from the. lower endof said; first? zone. downwardly through: a, plurality of longitudinally extending channels arranged in parallel in a second zone countercurrent to one of said two separate streams rising at a velocity which maintains said thermophore in said second zone in a state of dense phase fluidization, each of said channels having an effective size of .a pipe having an internal radius in the range of about inch to about 2 inches, maintaining in said second zone temperature gradients in opposite directions in said thermophore and in said one of the two separate streams, circulating said thermophore from the lower end of said second zone downwardly through said first zone as aforesaid, and passing the other of said two separate streams in heat transfer relationship with said thermophore while maintaining temperature gradients in said other separate stream and in said thermophore in said relationship.

8. The method as defined in claim 7-, in which said heat transfer relationship is effected in a 15 third zone similar in arrangement and operation to said second zone.

9. The method as defined in claim 8, in which hot synthesis gas is said single stream, and methane and oxygen are said two separate streams.

- 10. The method as defined in claim 8, in which air is said single stream, and cold nitrogen and oxygen rectification products are said two separate streams.

11. The method .as defined in claim 7, in which the horizontal cross-section of each of said channels gradually increases in the direction of increasing temperature.

12. The method of producing synthesis gas comprising essentially carbon monoxide and hydrogen, which comprises passing separate, compressed streams of methane and oxygen upwardly through separate, downwardly moving columns of heated, powdered thermophore maintained in a state of dense phase fiuidization while maintaining temperature gradients in opposite directions in said columns and said separate streams, reacting the thus heated streams of methane and oxygen in an unobstructed reaction zone maintained at a gauge pressure of at least 200 pounds per square inch and a temperature of at least 2300 F., passing the resulting hot synthesis gas from said reaction zone upwardly through a third, downwardly moving column of said thermophore maintained in a state of dense phase fiuidization while maintaining temperature gradients in opposite directions in said third column and said synthesis gas, discharging cooled synthesis gas from the top of said third column, and moving said thermophore from the bases of the first said separate columns to the top of said third column and from the base of said third column to the tops of the first said separate columns. r

13. The method of transferring heat between a single gaseous stream and two separate gaseous streams having substantially the same initial temperature, which comprises circulating a powdered thermophore downwardly through a plurality of longitudinally extending channels arranged in parallel in a first zone countercurrent to said single stream rising at a velocity which maintains said thermophore in said first zone in a state of dense-phase fiuidization, each of said channels having a limited, horizontal crosssection which substantially prevents top-tobottom mixing of said thermophore within the channel, thereby maintaining in said first-zone temperature gradients in opposite directions in said thermophore and in said single stream, the limited, horizontal cross-section of each of said channels gradually increasing in the direction of increasing temperature, circulating said thermophore from the lower end ,of said first zone downwardly through a plurality of longitudinally extending channels arranged in parallel in a second zone countercurrent to one of said two separate streams rising at a velocity which maintains said thermophore in said second zone in a state of dense phase fluidization, each of said channels having a limited, horizontal cross-section which.

. clients in said other separate stream and in said thermophore in said relationship.

PAUL W. GARBO.

References Cited in the file of this patent UNITED STATES. PATENTS Number Name I Date 1,178,667 Niewerth Apr. 11, 1916 1,619,577 Jensen Mar, 1, 1927 1,825,321 La Mont et a1. Sept. 29, 1931 1,871,166 Fahrback Aug. 9, 1932 2,009,084 Gomonet July 23, 1935 2,359,810 Hemminger Oct. 3, 1944 2,363,274 Wolk et al Nov. 21, 1944 2,394,814 Snuggs Feb, 12, 1946 2,396,709 Lefier Mar. 19, 1946 2,415,755 Ogorzaly Feb. 11, 1947 2,448,290 Atwell Aug. 31, 1948 2,529,630 Reichl Nov. 14, 1950 2,537,044 Garbo Jan. 9, 1951' 2,550,742 Welty Jr. May 1, 1951 2,560,469 Og orzaly July 10, 1951 FOREIGN PATENTS Number Country Date Great Britain Aug. 23, 1940