US2935466A

US2935466A - Method and apparatus for contacting gaseous fluids with solids

Info

Publication number: US2935466A
Application number: US561881A
Authority: US
Inventors: Pieter J Schoenmakers
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1955-01-31
Filing date: 1956-01-27
Publication date: 1960-05-03
Anticipated expiration: 1977-05-03

Description

1960 P. J. SCHOENMAKERS 2,935,466

METHOD AND APPARATUS FOR CONTACTING GASEOUS FLUIDS WITH SOLIDS Filed Jan. 27, 1956 6 Sheets-Sheet 1 I23 INVENTOR: E 7 AK RS A PIETER J SCHOENM E 4 B W FIG. 5 8 HIS A TORNEY May 3, 1960 P. J. SCHOENMAKERS 2,935,455

METHOD AND APPARATUS FOR CONTACTING GASEOUS mums WITH souns Filed Jan. 27, 1956 6 Sheets-Sheet 2 INVENTOR:

PIETER J. SCHOENMAKERS ma Mm ms A TORNEY May 3, 1960 P. J. SCHOENMAKERS 3 6 METHOD AND APPARATUS FOR CONTACTING GASEOUS FLUIDS WITH SOLIDS Filed Jan. 27, 1956 s Sheets-Sheet s INVENTOR PIETER J. SCHOENMAKER? BY WM fl W HIS ATTORNEY May 3, 1960 P. J. SCHOENMAKERS 2,935,466

METHOD AND APPARATUS FOR CQNTACTING GASEOUS FLUIDS WITH SOLIDS Filed Jan. 27, 1956 6 Sheets-Shegt 4 I NVENTOR PIETER J. SCHOENMAKERS BY ms ATTORNEY May 3, 1960 P. J. SCHOENMAKERS METHOD AND APPARATUS FOR CONTACTING GASEOUS FLUIDS WITH SOLIDS Filed Jan. 27, 1956 WASTE HEAT RECOVERY FLUlD-BED-4l 3/ l5 REACTOR QUENCH AIR LIFT POT 6 Sheets-Sheet 5 PRODUCT I N VENTOR PIETER J. SCHOENMAKERS HIS ATTORNEY y 1960 P. J. SCHOENMAKERS 2,935,466

METHOD AND APPARATUS FOR CONTACTING GASEOUS FLUIDS WITH SOLIDS Filed Jan. 27, 1956 6 Sheets-Sheet 6 FIG. 2| FIG. 22

' INVENTORZ PIETER J. SCHOENMAKERS HIS ATTORNEY METHOD AND APPARATUS ron CONTACTING GASEOUS FLUIDS wrrn SOLIDS Pieter .l'. Schoenmakers, Delft, Netherlands, assiguor to Shell Oil Company, a corporation ofDelaware Application January 27, 1956,Serial No. 561,881 Claims priority, application Netherlands January 31, 1955 17,.Claims. (Cl. mas-176i This invention relates to a new method and apparatus for the contacting of gaseous fluids with fiuidizable solids. One aspect of the invention relates to a process and ap- "paratus for continuously eflecting a rapid change in temperature in a gaseous fluid, or the rapid vaporization of a vaporizable liquid, by contact with a fluidizable solid of ditferent temperature. Q

The process of the invention is particularly applicable in the treatment of gaseous fluids (by which I mean to include true gases, vapors, and also liquids which are immediately vaporized upon contact under the conditlons) at high temperatures where undesired reactions tend to' or treatments which proceed and takeplace in less than 0.5 second. Onthe other hand, the process and apparatus of the invention are advantageous for the rapid cooling of a' vaporous high temperature reaction product whereby side reactions are repressed and/ or the reaction product is frozen at or near a high temperature equilibrium state. By applying both of these simultaneously it is possible to obtain both a very rapid heatingand a very rapid cooling after a very short or relatively long residence time at the high temperature or in other words a substantially square temperature versus time curve.

In many cases it is desirable or necessary, to contact one or more gaseous fluids with a solid material and in many of these cases the efliciency and duration of such contact are quite important. I

t In the past it has been the usual practice to pass the gaseous fluid through a bed of pieces of the solid which Were either in a fixed position or slowly moved through the contacting zone. In these cases the solid is in the form of relatively large particles upwards of inch in diameter since otherwise the pressure drop through the bed of particles becomes inordinately large.

Also, the so-called fluidized solid technique has come into wide-spread use for these purposes. This technique is not applicable for all solids but is applicable andoften advantageous when the solid is one which can be fluidized, i.e. be brought into a fluidized (pseudo liquid) state by suitable aeration with a gaseous fluid. The first requirement of the solid in this respect is that it be in powdered form, i.e. have a range of particle sizes from a minimum of a fraction of 21. micron up to a miximum of about 2 millimeters mean diameter. Although it is not necessary that this full range of particle sizes be present it is generally necessary that the particles have a substantial range of sizes, i.e. 'a factor of 3 or more, within these limits. Thesecond requirement of the solid is that the shape and/or electrical properties of the solid particles be such as to allow fluidization. Flake material, needle shaped particles, flocculant precipitates, some powders F atented May 3,1960

igcg I 5.2O microns, most magnetic solids, and solids consisting of only large particles, e.g. greater than about 2 millimeters, are diflicult or impossible to fluidize with. a gaseous fluid. The suitability of powdered solids in this 5 respect is best indicated by their angle of repose. Thus,

the above named materials, and others which cannotzbe properly fluidized, have a high angle of repose, e.g. 80 or more for burnt gypsum andtalcum powder. Solids which may befluidized generally'have an angle of repose 1 of 55 or less and the better ones an. angle of repose of about 45 or less. 1 a When the above requirements are met the solid may be fluidized. In the fluidized state the powdered solid acts in many ways like .a true'liquid, e.g. it seeks its own level; it is capable. of exerting a hydrostatic head; it can be pumped or poured much like amolten metal.

One of the characteristics of a fluidized powder is its cohesiveness For example, in contacting a gaseous fluid with a fluidized solid it is common, eg in conventional fluidized catalyst catalytic cracking, to pass'thegaseous fluid up through a bed of the fluidized powder at a superficial gas velocity which is considerably above the free fall velocity of the particles of the powder as calculated small amount of the powder is torn away from the fluidized bed and carried. by the issuing gaseous fluid. For various reasons the individual particles tend to approach or become closely associated with others, as a re-' consisting entirely of'very small particles, e.g. less than sult of which the particles do not behave as individual particles and the mass behaves much like a liquid.

vOn'the other hand, since this cohesive tendency increases with decreasing particle size (which accounts for the difficulty in fluidizing powders in which all of the particles are of extremely small and uniform size, e.g., less than 5 microns, and also large particles) the solid may contain, or even consists mainly of, quite small particles, e.g. average V/ S diameter less than 500 microns.

In the past this fluidized state has been obtained by passing a gas, or vapor, or in some cases a liquid which is rapidly vaporized upon contact with the solid, up through a bed of the powdered solid.

If a gas is introduced into the bottom of a settled bed of fluidizable solid at very low rate, the gas simply passes through the minute interstices and out of the top of the bed without affecting the bed itself. If the gas velocity is increased slowly a point is reached at which the bed expands somewhat and the particles move about. The point at which this occursmay be called the minimum .fiuidization gas velocity. This minimum 'fluidization: gas

fiuidization-gas velocity the bed has usually expanded by approximately 12% of its original, i.e. settled, volume. If the gas velocity is further increased the bed of powder expands somewhat further with no appreciable increase in pressure drop through the bed until a maximum limiting velocity is reached above which the powder is blown upward with the gas. Beyond this point a fluidized state no longer exists and the powder is simply dispersed as a suspension of individual particles in the gas. In the region of gas velocities giving a fluidized state the gas passes through the somewhat expanded interstices, although in many cases, due to maldistribution oi the gas, bubbles form and pass up through the pseudo liquid powder.

Thus, in the case of fluidized solids, the expansion of the interstices, within the limitations allowing the fluidized state, is produced by the energy of the gas forced up through the bed of powder. Y

The phenomenon of fluidization of powders has long .been known and the cohesive behavior has been qualitatively recognized. The magnitude of this cohesion, however, has, to the best of my knowledge, not been measured nor appreciated.

The present invention is based on the discovery that it is in'many cases advantageous with astounding .results to pass the gaseous fluid to be contacted horizontally (or approximately so), through a free falling body of the fluidized solid. 1

. It has hitherto been proposed to pass various gaseous fluids through a free falling shower of solid material, but in these prior instances the conditions were such that the particles of the solid behaved as individual or discrete particles. For example, if a fine powder is passed through a sieve into a free falling space the particles behave as a shower of discrete particles rather widely spaced as, for example, in arain. Passage of a gaseous fluid horizontally through such a'shower affords only a very mediocre contact efficiencyand if the velocity of the gaseous fluid is appreciable, the individual particles are carried with the gaseous fluid.

If large particles are allowed to drop through an orifice into a free falling space, the particles again behave as individual particles and also give only an open shower, again much like rain, which likewise aflords only a mediocre contact with a gaseous fluid passed horizontally therethrough. In the case of large particles this is due mainly to two factors. The first is that if large particles such as granules, spheres, pellets, etc. which are not fluidized are allowed to flow through an orifice into a free fall space, the mass flow of solid through the orifice does not obey the laws which apply to fluids and is considerably smaller. Even with orifices withdiameters many times the diameter of the particles, the resulting shower of particles is loose, non-coherent, and totally diiferent from the close coherent nature of a fluidized solid. The second factor is the natural tendency of individual free falling granules to separate. It is a well known fact of elementary physics of free falling bodies that if two particles are released into a free falling space, one immediately after the other, the distance between them continues to increase up until the. time where they attain their maximum or terminal free fall velocity. This is due to the fact that the distance of fall is a function of the square of the time of fall. If one passes a stream of pellets, for example, through an orifice into a free falling space the pellets separate. However, for the case of fluidized powders, within wide limits, this separation does not take place to any appreciable extent even over a considerable and practical distance of free falling height. This is due to the cohesive nature mentioned and to the relative low limiting free fall velocities of particles of the small size range in question.

There is a distinct difference in the behavior of a free falling mass of fluidized solids and free falling discrete particles of either large or small size when a gaseous fluid is passed horizontally therethrough. If one has an annular orifice and passes through this orifice into a free falling space powdered solid at such a mass rate that the particles act more or less as an annular shower of discrete particles, and if a gas is passed horizontally outward through the free falling annular shower at :1 velocity less than the terminal free fall velocity of the particles of the powder, the particles tend to move with the gas so that the shower of particles increases considerably in diameter a short distance below the orifice giving a cone shaped shower.

In the case of a free falling mass of fluidized powder, on the other hand, the cohesion mentioned is quite ap parent. The annular sheet does not become conical but remains substantially cylindrical even when the horizontal velocity of the gas passing therethrough approaches the terminal free fall velocity of the individual particles. If the velocity of the gas passing through the sheet is further increased the sheet retains this substantial cylindrical shape until at quite high velocities of the gas the 4 sheet bulges and then suddenly ruptures into a number of incoherent masses. In other words, it acts like a liquid.

In the case of a shower of large particles, e.g. above 1 mm. diameter, the spreading into a cone does not occur at'nominal gas velocities due firstly to the fact that the terminal free fall velocity of the such larger particles is much higher than the horizontal gas velocity and hence little angular horizontal displacement results, and secondly to the fact that due to the above-described separation phenomenon the shower offers practically no resistance to even considerable horizontal flows of gas; in other words, there is only a mediocre contact between the free falling relatively widely separated granules of solids and the gas. If the gas velocity is substantially increased, however, even these comparatively large particles behave just as described for discrete particles of powder. Thus, a conical configuration results and the angle of the cone increases with increasing gas velocity without any rupture as described above.

In the manner of contacting according to the invention, the effluent gaseous fluid passing through the mass of free falling solid entrains an unexpectedly small amount of this solid at gas velocities below that at which the sheet mass is ruptured.

I have found that by passing a gaseous fluid through such a coherent free falling stream of fluidized powder an unexpectedly excellent contact can be obtained with an extremely short contact time. Thus, for instance, I have passed vapors through such a free falling stream of fluidized solid of only about 7 millimeters thickness and have thereby increased the temperature of the vapors from a low temperature to within 5 C. of the temperature of the solid in the 900 C. temperature range. This far surpasses any other method known to me for effecting extremely rapid heating of a gaseous fluid in a continuous manner. 7

According to the invention the gaseous fluid to be contacted is passed horizontally through a free falling mass of the fluidized solid. As will be described in more detail below, certain conditions are essential and others are highly desirable in order to obtain this sort of contact.

Firstly, the solid must be one which meets the abovedescribed requirements and is therefore fluidizable. One suitable material which has been extensivelyused in various studies leading tothe invention and in pilot plant operation in the production of olefins from paraflin wax, is a fine silica sand having the following properties:

Volume/surface mean particle diameter=l microns;

True specific gravity=2.660 g./cc.;

Specific gravity in the fluidized state at minimum fiuidization gas velocity=l400 kg./m.

Size Distribution Sieve Aperture in Mierous 420 210 177 150 125 Percent Weight Undersize 07. 6 64. 0 30. 2 14. 6 5.0 3. l

ia/E wherein:

=mass velocity in kg./m. sec. C=a proportionality factor 1 p=density of the fluidized solid in kg./m. g=gravity acceleration in m./sec. h=depth of fluidized bed above the orifice in meters Thus, the mass flow is proportional to the 0.5 power of the pressure drop and very large mass flows may be ob- 7 by about 2 to 10 sheet thicknesses. Such shielding forces contacted gaseous fluid to flow downward parallel to the sheet.

When the gaseous fluid to be contacted is initially in the form of a forceable liquid which quickly vaporizes on contacting the sheet, it is best injected at a relatively high point near the top of the sheet as illustrated. However, when the gaseous fluid is initially in vapor form it may be introduced at a plurality of points of different elevation as well as in the horizontal arrangement illustrated. If the gaseous fluid to be contacted is introduced at a plurality of points, its jet head is less and there is considerably less tendency to rupture the sheet.

The sheet 1 in the apparatus according to Figures" 1 and 2 is formed by flow of fluidized solid through slit 2 provided at the top of the vessel 3 which houses the sheet. The fluidized solid is introduced via a pipe 4 to the fluidized bed in the upper vessel 5 which bed is maintained in the pseudo-liquid state by aeration gas supplied via the line 9. The solid material comprising the free falling sheet is collected in the collecting device 6 in which a fluidized bed of the solid is maintained. Aeration gas to maintain this lower fluidized bed in a pseudo-liquid state is introduced by line 8. In the arrangement illustrated this collecting device is integral with the lower part of the vessel 3. The fluidized solid particles are withdrawn from the collecting device 6 by pipe 7. By altering the level of the fluidized bed in the upper section the mass of fluidized material passing through the slit orifice 2 can be regulated. The gaseous fluid which is to be contacted with the solid is supplied by one or

more lines

10, 11, and 12 to one side of the sheet 1. In place of the separate lines a single distributing means extending over the whole width of the sheet may be used. The gaseous fluid, after passing through the sheet, is withdrawn on the other side thereof through line 13.

If the sheet consists of material which has a temperature considerably lower than that of the gaseous fluid to be contacted the gaseous fluid is cooled very rapidly on passing through the sheet.

If, on the other hand, the temperature of the sheet is considerably higher than the temperature of the gaseous fluid supplied through

lines

10, 11, and 12, the gaseous fluid is heated very rapidly on passing through the sheet. The heated gases being withdrawn byline 13 may be quenched by means of a quenching medium introduced via line 14. a

The described arrangement is quite suitable for many reactions which may be carried out either thermally or catalytically. For instance, the thermal cracking of paraflin waxes to produce olefins, and the thermal coking of tars or pitches are examples of treatments for which this system is suited. The system may also be used to carry out reactions between two or more gases which have to be raised rapidly to the desired reaction temperature. Thus, for example, separate reactants may be supplied separately via the

lines

10, 11, and 12. The mixture is rapidly heated to the reaction temperature upon being passed through the sheet 1 and the vapors afterwards react in the space downstream with respect to the sheet 1. The reaction product is removed by line 13 as before. If two separate reactant gases are mixed first and then supplied by

lines

10, 11, and 12, the reaction is at least initiated and in some cases may be substantially completed during the exceedingly short time that the mixture is passing through the sheet.

a In the arrangement illustrated in Figures 3 and 4 the orifice is an annular slit 15. The fluidized solid particles in the supply means 5 flowthrough this annular slit to form a cylindrical sheet 16 in vessel 3.

Any closed figure may be chosen for the cross section of the sheet. This cross section is preferably a circle (annulus) (as illustrated in Figure 4) since in this case the gaseous fluid to be contacted may be more evenly distributed when introduced centrally via the nozzle 17. If

the gaseous fluid to be contacted is initially in the gaseous state it will be introduced simply through an open ended pipe or through a conventional gas distributing nozzle. If the gaseous fluid to be contacted is initially a liquid which is easily and rapidly vaporized upon contact with the solid, the nozzle 17 is preferably one which will atomize the liquid such, for example, as a swirl chamber atomizer.

By using a wider orifice the sheet may be made up to any desired thickness. However, since the contact is so efficient it will rarely be necessary to have the sheet more than a few inches thick. 7

Greater throughput capacity may be obtained by in creasing the height of the sheet and by increasing the diameter of the cylinder, preferably the latter. If the diameter of such a cylindrical sheet is greatly increased, e.g. to several feet, the space within the cylinder becomes rather large. In order to decrease the residence time of the gaseous fluid in this space an axially placed dummy of cylindrical or conical shape somewhat smaller than the space may be provided. The gaseous fluid is thereby caused to occupy only that part of the space between the dummy and the sheet.

In this arrangement also one or more gaseous fluids may be supplied either separately or in admixture and contacted by passage through the sheet. Also, as in the arrangement shown in Figures 1 and 2, an additional gaseous reactant may be supplied into the space (by means not shown) downstream with respect to the sheet ll; order to react this gas with the gases issuing from the seet.

The quenching of the contacted gaseous fluid may be eifected as described by injection of a suitable quenching liquid via line 14 into the product line 13. The quenching may, however, be effected even more promptly by passing the gaseous reactant product issuing from the sheet directly through a second sheet having a low temperature. A very rapid cooling of the gaseous fluid can thereby be effected immediately following the rapid heating. Thus, an arrangement similar to that illustrated in 'Figure 1 may be provided with a second sheet of relatively cold material as illustrated in Figures 5 and 6.

Referring to these figures the second sheet 18 is at a relatively short distance from the hot sheet 1. Cooled solid is supplied into an upperfluidized bed 20 by means of line 19. As before, the solid is maintained in a wellfluidized state by the injection of a suitable aeration medium introduced by line 21. The orifice for this second sheet is the slit 22. This sheet is collected in the lower collecting device 23 which is filled with the solid maintained in a fluidized state by injection of a suitable aeration medium via line 24. The hot and cold fluidized materials are withdrawn from their respective collecting devices by

lines

7 and 25, respectively.

In a similar manner the hot and cold sheets may take the form of two concentric cylinders as illustrated in Figures 7 and 8. The gaseous fluid to be contacted is supplied at a point or points in the interior of the inner sheet 16 through the nozzle 17. The gaseous fluid passes through this sheet whereby it is rapidly raised to a high temperature after which the hot gaseous product passes through the outer sheet 53 whereby it is rapidly cooled.

In the arrangement illustrated in Figures 9 and 10, there are two sheets, both of which are relatively hot. This arrangement is suitable for reacting gaseous fluids which have to be raised separately to the required reaction temperature. Thus, one of the fluids is supplied on the left of sheet 1 via the

lines

10, 11, and 12 and the second gaseous fluid is supplied to the right of the sheet 1' via

lines

26, 27 and 28. After these respective fluids pass through the sheets they react in the space within vessel 3 which is defined by the two sheets. The reaction product is removed through line 29 either with or without quenching.

In the arrangement illustrated in (Figures 11 and 12,

H e. V there are likewise two hot-Isheets' 16 and 16* in the form of concentric cylinders. One of the. gaseous fluidsis introduced on the outside of the outer-cylinder and passes inward. The other gaseous fluid is introduced invthe space within the inner r cylinder and passes outward; The two pre-heated gaseous'reactants react in theannular space betweenthe two cylinders and are-withdrawn by line. 29. l I p I Figure liq shows an apparatus operating on the principle illustrated in Figure 3. The"hot sheet 16 is supplied from the upper'fluidized'bed in chamber through an annular slit. The sheet is therefore in the form of a cylinder. The solid material invesselS is maintained in the fluidized state by supplying'an aeration medium through line 9 the outlet of which is positioned below the level of the slit 15. This arrangement insures a regular supply of thefluidized solid according 'to the laws for liquid .flo w. The sheet falls into the collecting device 6 in which a bed of the solids is maintained fluidized is spaced some distance from the sheet.

In'this particular. arrangement a baflle33'is provided which partly extends into the fluidized -bed in the 1 can lecting device 6. The 'top of this bathe partly surrounds as the wall 32 leaving some space. c In the arrangementillustrated in Figure 14 the wall .32 is provided with'louvers arranged in such a way? that the gas passing therethrough' is sharply deflected in an upward direction. As before, the wall 32' is spaced away. from the sheetso that the sheet falls free without wall friction. n

In some cases a small amount of the finer particles of the solid are carried with the efliuent gaseous fluid. Any

material so carried in suspension may be separated with.

a cyclone separator 35 insertedin the discharge line 13. The gaseous fluid from which any substantial solids have been separated is withdrawn through the overflow 36 and the solid particles whichhave been separated'flow by gravity down the dip leg of the cyclone'to the seal pot 37 from which they pass to .vessel'38r The fluidized solid in the collecting device 6 likewise overflows into the lower vessel 38. A line 39 leads from the vessel 38 to a heater (not shown) and a riser' (not shown) for transferring the solid particles from the level 'of the discharge line 39 at least to the level of the inlet 4 'of the upper vessel 5. The solid in the lowervessel 38 is further stripped of occluded material and maintained in a fluidized state by the injection of a suitable aeration medium. This material, as well as the aeration medium supplied by line 8 to the disengaging device 6, is removed with the product through line 13 and the cyclone over- The gaseous fluid removed by line 36 after having been contacted with the solid usually contains some gaseous by-products of side reactions. While such side reactions :are minimized by the use of the described method of contacting they usually cannotbe totally avoided. After removing the desired product from the reaction mixture this residual gas may be advantageously utilized to fluidize "the solid in the upper bed. For this purpose it may be "introduced by line 9.

The apparatus illustrated in Figure 13 was used for f th production of light olefins by short time, high temhaving the followperature cracking of a heavy cyclic oil ing properties: 7

'Molecular weight 366 Normal paIaflins percent 35 Isoparaffins-i-naphthenes do 63 'The above-mentioned sa'nd was used to form the screen which'w'as 5 centimeters internaldiaineter, 6.5 centime acumen ters external diameter, and 25 centimeters in length.

@The nominal throughput of the sand was about 12 tons per hour. The'results are given in the following tabulation:

Temperature v C-.. 750 Hydrocarbon throughput lcg./hour 40 Residence time (atomizer to quench) seconds 0.4 Conversion, weight percent on feed 80.2 Ethylene yield,.weight percent on feed. 24.4 Methane yield; weight percent on feed; 8.2

The same apparatus and sand were used for-the short contact time high temperature cracking of a brights'tock slack wax at temperatures between 750 and 850 C. and at a throughput rate of 40 kg./hour. The results are tabulated below'z' a Temperature, o r50 800 850 Residence time (atomizer to quench), seconds 0. 3 0.25 0. 2O Conversion, wt. percent on feed 76' 84 Ethylene yield, wt. percent on teed 16; 5 26. 7 Methane yield, wt. percent on feed 5.2 9. 8

-. which are led from thecollecting device 6 of the apparatus A via the riser i0 and the cyclone 41 to the supply hopper 42' of part B. Fluidization medium is supplied through the line 43 to the fluidized bed in vessel 42. The discharge nozzle is again an annular slit 44 which produces a cylindrical sheet in vessel 45.

' Fuel is supplied by line 47 and nozzle 48 together with combustion air by line 49 into the space enclosed by the sheet. The combustion gases pass through the sheet thereby heating it and are withdrawn. through line'fit) connected to vessel 45. If the solid contains carbonaceous materialthis may be partly or completely burned off through the use of excess air in the combustion mixture.

The collecting device 51 of the apparatus B for the hot material'is provided with a supply line 52 for fluidization medium and at the same time forms the supply for the lower sheet 16 in apparatus A. The gaseous fluid to' be contacted is introduced, as before, by nozzle 17 and the contacted product is removed by line 13. In this arrangement it will be noted that the sheet is housed for substantially its entire length without frictional contact by the depending baflle member 32. This baffle extends to within a short distance above the level of the fluidized bed of material in the collecting device 6. The material of the sheet 16 is collected in the fluidized bed in the collecting device 6 from which it is withdrawn by line 7 to a riser 4% wherein it is carried to the cyclone 41 and from there back to the supply chamber 42of the part B.

The apparatus shown in Figure 16 is similar to that shown in Figure 13 but differs in the arrangement of the collecting device and baflle shielding around the sheet.

The solid collected in the lower fluidized bed in vessel 38 passes by line 39 to the lift pot at the bottom of a vertical 7 riser wherein it is elevated to a point above the level of the discharge passage 4. Air introduced at the bottom of the lift pot serves as the conveying medium. The solid is separated from the air by an exceedingly simple but 1 efiectiveiseparator consisting of the large inverted hat placed directly above the exit of thevertical riser line.

better control the temperature at which the reaction occurs, and/or to limit the time at such temperature.

As explained above, the processes and apparatuses of the invention are particularly suitable for the thermal cracking of paraflin waxes to produce olefins. This cracking is preferably carried out at-temperatures of the order of 700800 C. in the presence of steam, and in some cases oxygen. They also are suitable for the reaction of methane with steam to produce carbon monoxide and hydrogen. Oxidation reactions such as the reaction of methane with oxygen under conditions to produce acetylene or aromatic hydrocarbons can be also carried out in the manner indicated. Another application is in the oxidation of ammonia at temperatures of the order of 700-100 C.

Also, various catalytic processes may be carried out such as the dehydrogenation of alkanes to alkenes using a chromium oxide catalyst or one of the various other known dehydrogenation catalysts.

In the chlorination of propylene to produce allyl chloride it is highly desirable to eifect the reaction at a high temperature, e.g. above 500 C., with a very short contact time. The present method and apparatus are suitable for this type of reaction. The reaction between methane, ammonia, and oxygen to produce hydrogen cyanide and water using a catalyst containing platinum can also be efiected, as also the reaction of methane and nitrogen oxide to produce hydrogen cyanide at approximately 1000 C..

The rate at which heat is transmitted when operating according to the method'of the invention is very large. By way of example a heat transmission of 3 X10 KCal. per cubic meter of treating space per hour has been obtained in the apparatus illustrated in Figure 13. The solid material in this case was the above mentioned silica sand. The cylindrical sheet in this case had an annular cross section with an internal diameter of 5 centimeters, an external diameter of 6.5 centimeters and a height of 30 centimeters. The mass velocity of sand in this sheet was tons per hour. The temperature of the sand in the fluidized bed in chamber 5 was 750 C. Temperature of sand in the collecting device 6 was 700 C. The residence time of the gaseous fluid within the cylinder which had a capacity of 3 liters was .03 second. In passing through the sheet the temperature of the gaseous fluid was raised from 100 C. to 685 C. in 0.004 second.

I claim as my invention:

1. Process for effecting rapid change in temperature of a gaseous fluid in which the gaseous fluid is contacted with a fluidizable solid by passing the said gaseous fluid transversely through a free falling coherent sheet of fluidizable solid formed by passing the solid from a well fluidized body of the solid through an unrestricted slitlike orifice into a free fall space, said solid having a temperature which varies considerably from that of the said gaseous fluid to be contacted.

2. Process for efiecting rapid but intimate contact between a gaseous fluid and a fluidizable solid which comprises forming a well fluidized bed of said solid, flowing said fluidized solid from said bed through a slit-like orifice into a free fall space to thereby create a coherent sheet of the free falling solid and passing the'gaseous fluid to be contacted transversely through said sheet.

3. Process according to claim 1 further characterized in that the gaseous fluid consists essentially of hydrocarbons and the temperature of the sheet is sufiiciently high that the hydrocarbons are cracked in passing through said sheet.

4. Process according to claim 1 further characterized in that said gaseous fluid consists essentially of at least 2 reactants and that the temperature of the sheet is so chosen that reaction between the reactants takes place during passage of the reactants through said sheet.

5. Process according to claim 1 furthercharacterized 12 in that said fluidized solid is a powder which is inert chemically and catalytically with respect to the gaseous fluid with which it is contacted.

6. Process according to claim 1 further characterized in that said fluidized solid is at least in part formed of powdered substances which catalyze reactions which take place during passage of gaseous fluid through the sheet.

7. Process according to claim 1 further characterized in that the gaseous fluid contains at least 2 reactants which are allowed to react after being brought to the desired reaction temperature by contact with said sheet.

8. Process according to claim 2 wherein said sheet is in the form of a cylinder and the gaseous fluid to be contacted is introduced within the cylinder.

9. Process according to claim 2 further characterized in that there are two said fluidized beds and two said sheets, one of which is maintained at a high temperature and the other at a low temperature and that the gaseous fluid is passed serially through said sheets thereby providing a very short and substantially square temperature versus time curve.

10. Process according to claim 2 further characterized in that the said slit-like orifice is substantially of plate thickness, is at least 5 millimeters in width, and is positioned above the level of the point of introduction of fluidization gas in said fluidized bed.

11. An apparatus for eifecting a'rapid change in the temperature of a gaseous fluid which comprises a first upper vessel adapted to maintain a bed of fluidizable solid, gas distributing means in the lower part of said vessel for the introduction of a fiuidizing gas to maintain said solid in a well fluidized condition, a slit-like orifice in the lower part of saidvessel but above the level of said distributing means, said slit-like orifice being directly above a free fall space surrounded by a wall of a lower chamber below and connected to said first vessel, a second open-topped vessel positioned directly and at some distance below said slit-like orifice, gas distributing means in the lower part of said second vessel for maintaining the; contents thereof in a fluidized condition, a third and lower vessel larger and encompassing said second vessel and sealed to said wall of said lower chamber and adapted to catch the overflow of said second vessel, gas distribution means for injecting fluidization gas into the lower part of said third vessel, means for injecting a gaseous fluid into said lower chamber on one side of said slit-like orifice and means for withdrawing contacted gaseous fluid from said lower chamber on the other side of said slit-like orifice.

12. Apparatus according to claim 11 further characterized in that said apparatus is provided with an openended shield extending from said first vessel and spaced a short horizontal distance from said orifice said shield being within said lower chamber and extending from said first vessel to a short distance above the top of said second vessel.

13. Apparatus according to claim 12 further characterized in that the apparatus is also provided with a cylindrical bafile open at both ends and positioned below said orifice at a greater horizontal distance from said orifice than the said shield, said baflie extending in height from about the. lower end of said shield to a point within and somewhat below the eflective top of said second vessel.

14. Process for effecting rapid but intimate contact between a gaseous fluid and a fluidized solid which comprises forming a well fluidized bed of said solid, flowing 7 said fluidized solid from said bed through a slit-like aperture having a minimum confined channel with substantially no constricting hydraulic radius into a free fall space to thereby create a coherent sheet of free falling solid and passing the gaseous fluid to be contacted transversely through said sheet.

15. Process according to claim 14 wherein the coherent sheet is shielded over a substantial part of its height by a baffle on the side of the sheet through which the contacted gaseous fluid emerges and at a distance from the sheet of about 2 to 10 times the thickness of the sheet.

16. Process for eifecting rapid but, intimate contact between a gaseous fluid and a fluidized solid which com- 14 to create a coherent sheet of the fluidized free falling solid and passing thegaseous fluid to be contacted transversely through the sheet, said sheet extending across prises forming a well fluidized bed of said solid, flowing said fluidized solid from said bed through a slit-like orifice into a free fall space at a mass flow rate suflicient to create a coherent sheet of the fluidized free falling solid and passing the gaseous fluid to be contacted transversely through the sheet, said sheet terminating at its lower end in a second fluidized bed of the solid and having its transverse cross-section in the form of a closed figure.

17. Process for eflecting rapid but intimate contact between a gaseous fluid and a fluidized solid which comprises forming a well fluidized bed of said solid, flowing said fluidized solid from said bed through a slit-like orifice into a free fall space at a mass flow rate sufficient the entire section of the confining chamber from wall to wall and terminating at its lower end in a second fluidized bed of solid.

References Cited in the file of this patent UNITED STATES PATENTS 1,836,325 James Dec. 15, 1931 2,259,487 Payne Oct. 21, 1941 2,347,747 Melaven c May 2, 1944 2,440,525 Roetheli Apr. 27, 1948 2,458,357 Evans Jan. 4, '1949 2,542,887 Watson Feb. 20, 1951 2,574,850 Utterback et a1 Nov. 13, 1951 2,697,686 Leflier Dec. 21, 1954 2,726,938 Lassiat Dec. 13, 1955 Letter Mar. 12, 1957

Claims

1. PROCESS FOR EFFECTING RAPID CHANGE IN TEMPERATURE OF GASEOUS FLUID IN WHICH THE GASEOUS FLUID IS CONTACTED WITH A FLUIDIZABLE SOLID BY PASSING THE SAID GASEOUS FLUID TRANSVERSELY THROUGH A FREE FALLING COHERENT SHEET OF FLUIDIZABLE SOLID FORMED BY PASSING THE SOLID FROM A WELL FLUIDIZED BODY OF THE SOLID THROUGH AN UNRESTRICTED SLITLIKE ORIFICE INTO A FREE FALL SPACE, SAID SOLID HAVING A TEMPERATURE WHICH VARIES CONSIDERABLY FROM THAT OF THE SAID GASEOUS FLUID TO BE CONTACTED.