US2467149A

US2467149A - Handling finely divided materials

Info

Publication number: US2467149A
Application number: US457384A
Authority: US
Inventors: John C Munday
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1940-11-02
Filing date: 1942-09-05
Publication date: 1949-04-12
Anticipated expiration: 1966-04-12

Description

J. c. MUNDA-Y 2,467,149

April 12, 1949.

HANDLING FINELY 'DIVIDED MATERIALS Original Filed Nov. -2, 1940 aiented Apr. 12, 1949 2,467,149 use mm nrvInEn MATERIALS John C. Munday, Cranford, N. J., assignor to Standard Oil Development Company, a corporation oi Delaware Original application November 2, 1940, Serial No.

364,085, now Patent No. 2,311,564, dated Februan 16, 1943. Divided and this application September 5, 1942, Serial No. 457,384

4 Claims.

This invention relates to a method of handling finely-divided materials and pertains more particularly to a method of imposing a pressure on such material. Y

The present invention forms a division of application Serial No. 364,085, filed November 2, 1940, which issued to Patent No. 2,311,564 on February 16, 1943.

In many types of industrial processes in which powdered materials are involved, it is desirable to place the powder under susbtantial pressure. One example is catalytic operations in which powdered catalysts are employed. In such operations, suflicient pressure must be imposed on the powder to feed the same into the stream of reactant gases which in turn must be under a pressure adequate toforce the resulting mixture through the reaction zone. Also, it may be desirable in many instances to carry out the operation under a substantial pressure.

The main object of the present invention is to provide an improved method of building up pressure on powdered material.

It has heretofore been proposed to place powdered material under a positive pressure by mechanical means, such as, for example, by the use of a compression screw. However, this method gives rise to certain inherent mechanical dimcu-lties. Perhaps the most serious objection to this method is the amount of power required to build up the pressure. The power required increases at a disproportionately greater rate with increase of pressure across the compression screw. In many instances the compression screw becomes seriously eroded or abraded by the powdered material which necessitates frequent replacements. In other cases the application of mechanical pressure may adversely affect the character of the powder being compressed. For example, in catalytic operations involving the use of acid treated clay, it has been found that the use of compres-@ sion screws tends to agglomerate the clay particles into spheres.

In lieu of a compression screw or other similar mechanical devices, it has also been a practice in some cases to build up the required pressure by means of pressure hoppers in which the powdered material is placed and the required pressure built up by means of a gas imposed above the level of the material in the hopper. This method, however, is objectionable in many cases. For example, in processes which operate continuously requiring continuous removal of the material from the hopper, additional receptacles must be provided so 2 that some may be placed under pressure while the material is being withdrawn from others.

It has also been proposed in isolated cases to build up the required pressure on powdered ma- 5 terial by means of a vertical column of said powder. By maintaining the powder within the column in a freely flowing state, a static pressure similar to hydrostatic pressure in the case of liquids may be developed at the, bottom of the column. However, there are practical limitations with respect to the height of the column which may be employed for building up pressure in this manner.

In accordance with the present invention, a plurality of columns or standpipes is provided and a substantial portion of the static pressure developed from one column is carried over or transferred intoa second column in which further pressure is built up. Therefore, by provision of sufflcient number of such columns any desired pressure may be imposed on the powder. The present invention is made possible by the fact that finely-divided powdery materials under certain conditions may be made to behave as a liquid.

For a more complete understanding, the invention will be now described in more detail in which reference will be made to the accompanying drawing which is a diagrammatic illustration of an apparatus which may be employed for carrying the invention into effect.

For illustrative purposes, the invention will be described as applied to catalytic processes employing powdered catalysts and more specifically to catalytic cracking of oils in which the invention has found particular application. It will be understood, however, that the invention in its broader phases is not so limited.

Referring to the drawing, the reference character ll designates a hopper for the powdered,

material employed in the process. The powdered catalyst from the hopper I I discharges into a ver=- tical standpipe I2 of a height sufiicient to develop a substantial pressure at the bottom thereof. To insure that the powdered material in the standpipe I2 is in freely flowing condition so that the pressure is transmitted to the bottom of said column, a fluidizlng gas from the manifold line l3 may be introduced into the standpipe l2 through v one or more lines l4, l5 and I6.

The powdered catalyst from the bottom of the standpipe I2 is fed through any suitable valve l1 into a return leg l8 into which a carrier gas is introduced through line l9 leading from the manifold lin 20. The amount of carrier gas introduced into the return leg [8 should be suffl- 3 cient to considerably reduce the bulk .density of the stream flowing therein. The diluted stream of powder and gasof low bulk density is transferred from the bottom of the standpipe I2 through ascending leg I8 into the top section 2| of a second standpipe 22. The upper portion of the hopper section 2| may be provided with a suitable separator for segregating solids from gases. such as a cyclone separator 23. The fluidizing gas separated from the catalyst in the cyclone separator 23 is removed therefrom through line 24. The catalyst from the hopper section 2I feeds into the vertical column or standpipe 22 through which a fiuidizing gas from manifold line 25 may be introduced through one or

more lines

26, 21 and 28 so as to maintain the powder in the second standpipe 22 in a freely flowing state. If desired, a portion of the fluidizing gas from manifold 25 may be introduced at one or more spaced points in return leg I8 through lines 21' and 28'. Additional pressure is developed by the catalyst at the bottom of the standpipe 22. The bottom of the second standwill reduce the bulk density of the material therein. It is generally preferred to introduce the minimum amount of fluidizing gas which ensures perfect fluidity, since the density under freely flowing conditions determines the pressure developed per linear foot of standpipeior any given material. Similarly, since the back pressure developed in the up-fiowing leg depends on the density of the powder, it is advantageous to employ a large amount of gas therein. The amount of pressure produced in each U-tube may be conveniently controlled by the relative amounts of gas introduced into the two legs. It has been found that in the case of activated clays the maximum density under freely flowing conditions may be of the order of to 35 pounds per cubic foot. In such case, from 4 to 6 linear feet of standpipe may be required for each pound per square inch of pressure developed. It will thus'be apparent that forbuilding a pressure of only a few atmospheres in a single standpipe,

, towers of extreme height would be required.

pipe 22 is also provided with a suitable valve 29 through which the catalyst is fed into a return leg 30 in which it intermingles with additional carrier gas introduced through line 3|. By reducing the density of the. powdered material in the return leg 30, the catalyst may be returned. to another separator 34 in hopper 32 located at the top of a third standpipe 33. The fiuidizing gas separated from the catalyst in the cyclone separator 34 is removed therefrom through line' 35 and may be rejected from the system through line 36. However, this gas is normally at a higher return leg I8. .In accordance with one of the specific features of the present invention, the

gas separated in the cyclone separator 34 may be used as a carrier for the catalyst in the return leg I8 and, if desired, it may also be used for maintaining thecatalyst in the initial standpipe I2 in a freely flowing condition. To this end, a part or all of the gas withdrawn from the cyclone separator 34 through line 35 may be passed through

lines

31 and 38 into line I9 leading to the leg I8. Also, a portion of this gas may be fed through line 39 into manifold line I3, from whence it may be passed into the initial standpipe I2 at one or more spaced points through lines I4, 15 and I6.

The catalyst from the third cyclone 34 feeds into another standpipe 33 which develops additional static pressure. To, insure maintaining the catalyst in the standpipe 33 under freely flowing conditions, a fluidizing gas from line 40 may be introduced at one or more spaced lines 4|, 42 and 43.

The apparatus hereinbefore described forms in effect a series of U-tubes with the powdered material flowing downwardly in one leg of the tube and upwardly in the other. The progressive building up of pressure on the catalyst is obtained by reducing the density of the catalyst in the up-flowing leg of the U-tubes. The pres sure developed by each of the standpipes I2, 22 and 33 depends upon the height and density of the powder in turn depends upon the specific gravity of the material and to some extent upon the size of the particles. In order for the column to transmit its pressure throughout its length, it must be maintained in a fluidized state. This, in most cases, requires the addition of a fiuidizing gas to prevent packing of the column. This therein. The density. of the powder .35 pressure than the gas introduced into the first However,.by building up the pressure progressively ina series of standpipes as described, a material saving in structural steel and other materials may be realized.

The carrier gas used for reducing the density in return legs I8 and 30 and the gas introduced at various points in the standpipes I2, 22 and 33 may be an inert carrier gas or it may be an active gas capable of undergoing reactions in the presence of the powder or capable of modifying the character of the powder. For example, it may be an oxidizing gas capable of reacting with carbonaceous deposits formed on the catalyst during may be passed through a suitable valve 44 into' a stream of gases introduced into the system through line 45. These gases may be of any type which it is desired to contact with the powdered material from the column 33. In many cases, it is desirable to subject catalyst following a treating operation to a conditionin treatment with a gas or vapor before returning the same to the reaction zone. In other cases it may be desirable to add or extract heat from the catalyst before returning it to the reaction zone. In the latter instance the gas introduced through line 45 may be a relatively inert gas utilized as a carrier gas for conveying the catalyst through a heat exchange zone.

As previously mentioned, for illustrative purposes, it will be assumed that the powdered material is a cracking catalyst which has been con- -taminated with carbonaceous deposits in the cracking of hydrocarbon oil and that it is desired to regenerate the catalyst by treating with an oxidizing medium such as air. The invention is especially useful in such processes because of the increased burning rate and the increased heat transfer rate which result from increase in pressure. The gas preheated to the required treating tempeature and introduced through'line 45 commingles with the contaminated cracking catalyst withdrawn from the bottom of standpipe 33 through valve 44 and theresulting mixture passes through line 46 to a conditioning vessel 41 in which the gas and catalyst are retained for a period suihcient to condition the catalyst to the desired amount. In the specific case illustrated,- this vessel constitutes a regeneration zone. However, as previously described, this vessel may be a. heating or cooling zone in which heat is added or extracted from the catalyst and may be .of any suitable construction for attaining the desired results. In most cases, to obtain intimate mixing of the powder and the conditioning gas, it is desirable to pass the reactant mixture through the treating vessel at relatively low velocities so that there is a general tendency for the powdered material to settle out of the gases during the passage therethrough. When operating inthis manner, the time of residence of the powdered material within the treating vessel will be materially greater than the time of residence of the gases therein.

The stream of powdered material suspended in the gas is withdrawn from the vessel 41 through line 48.

treating zone without any intermediate treat ment. For example, the conditioned catalyst may be cooled and recycled to the treating-zone where, by reason of its heat capacity, it is of assistance in maintaining heat control therein. The mixture may, therefore, be transferred through

lines

48, 49 and 50 or or both to the inlet of either separator 23 or 34 in the top of the

standpipes

22 and 33, depending on the pressure drop obtained in line 46, zone 41 and

lines

48 and 49. The catalyst recycled in this manner is. discharged from separator 23 or 34 directly into

standpipe

22 or 33.

A part or all of the streamof gaseous products and catalyst removed from the reaction zone 41 through line 48 may be passed through line 52 to a cyclone separator 53 or other equivalent separating devices for removing the gaseous reaction products from the powdered catalyst; The gases separated in the separator 53 are removed overhead through line 56 and may be withdrawn through line 51-, or they may be passed through In some cases it may be desirable to return a portion of the catalyst directly to the as previously described with respect to the conditioning vessel or zone 41 soas to efiect intimate mixing between the catalyst and the gas to be treated therewith. Also, as previously menpipe 12. In this case, the catalyst separated from the vapors in the separator 69 passes directly to thelinitial standpipe l2 for return to the regeneration zone.

Reaction products separated from the catalyst in separator 69 .are removed therefrom through line 10 and are subjected to further fractionation and purification of the final product in apparatus not shown.

' The catalyst removed from the cracked products in separator 69 discharges into hopper II from whence a part or all may be passed tothe conditioning vessel 41 through standpipes I2, 22

lines 58 and 3| and utilized as a fluidizin and conveying gas in the up-flowing leg 30, or by way of cross-over line 59 and

lines

38 and 19 in the up-flowing leg l8; If it is desired to allow a considerable time of contact between the gases separated in separator 53 and the up-fiowing catalyst, leg 30 may be enlarged to form a reaction vessel similar to vessel 41 in the up-

fiowing legs

46 and 48. Similarly, a reaction vessel may be built into up-leg 18. The passage of gas separated in separator 34 through

lines

31, 38 and 19 into the stream of catalyst flowing upward in leg l8 has already been described. 7

The catalyst separated in the cyclone separator 53 may feed directly into a further standpipe 55 in which a fluidizing .gas for maintaining the catalyst in freely flowing condition may be introand 33 and return legs [8 and 30. The fluidizing gas introduced into standpipes I2, 22 and 33 and the carrier gas introduced into the

return legs

18 and 36 will remove vaporizable hydrocarbons adsorbed or otherwise retained on the catalyst separated in the cyclone separator 69.

In cases where only a portion of the catalyst removed from the cracked products in septrator 69 is subjected to conditioning treatment in conditioning vessel 41, the remainder may be returned to the reaction zone 66 through line 1| having a valve 12. When employing this method, for reasons of safety the fiuidizin'g gas introduced into standpipe l2 and up-leg l8 should not be incompatible with the vapors undergoing reaction in zone 66.

Fresh makeup catalyst may be introduced into the circuit through hopper 13.

It will be understood that, whereas in the above-described example it is preferable to conduct the catalyst conditioning treatment at a higher pressure than the reaction pressure, in some cases the pressures will be substantially equal, and in other cases the reaction pressure will be the higher.

From the foregoing, it will be apparent that the present invention has provided a means for building up the desired pressure on powdered materials without the use of anymoving parts. It will also be apparent that by the present'invention it is possible to treat gas or vapor with a powder concurrently in each of several stages, the

duced at any one or more spaced points through

lines

66, 6| and 62.

The catalyst from the standpipe 55 may be fed at the desired pressure through a suitable pressure control valve 63 into a stream of fiuidizing and reactant gas introduced through line 64. This gas may, for example, be hydrocarbon vapors which it is desired to crack. The resulting "uspension of vapors and catalyst then passes through line 65 to a chamber 66 which in the specific case illustrated constitutes a reaction zone. The flow of vapor and catalyst through the reaction zone 66 may be at relatively low velocities overall flow of powder being toward increasing pressure and the overall flow of gas being toward decreasing pressure. In the regeneration of catalysts by burning with air, this ofiers a distinct advantage in that the burning is more easily controlled; since toward the end of-regcneration when the coke content is relatively low the burning rate is favored by the increase in pressure, while in the early stages of regeneration when the coke content is high the oxygen partial pressure is relatively low. This modification of the invention may also be applied in the catalytic cracking of certain hydrocarbon oils in which a higher pressure ls'employed during early stages of cracking than during later stages. Another application is in the cracking of oils wherein it is desired to treat the cracked products or the gasoline constituents thereof with additional catalyst at the same or at a lower temperature in order to reduce acid heat.

Still another application is the reforming of naphtha in the presence of hydrogen, whereinthe naphtha after being reformed in a later stage is utilized together with the hydrogen in an earlier stage as a fluidizing and conveying gas at a lower temperature whereupon the gum' content of the naphtha is reduced by hydrofining. It will of course be understood that the temperature of standpipes and of up-legs of the U-tubes can be controlled at will by suitably placed heat ex changers or by enclosure in heat exchange baths.

Having described the preferred embodiment of the invention, it will be understood that it embraces such other variations and modifications as come within the spirit and scope thereof.

What is desired to be protected by Letters Patent is:

1. A process for contacing gases with solids which comprises passing the gases to be contacted through a contacting zone, intermixing the gases passing through said contacting zone with a finely-divided solid material, continuously removing gases from said contacting zone, freeing the gases so removed of solid material, passing at least a portion of the gases so freed through a second contacting zone maintained .at a pressure materially below the pressure maintained in said firstnamed contacting zone, intermixing a, finelydivided solid material with the gases passing through said second contacting zone, continuously removing finely-divided solid material from said second-named contacting zone, passing finely-divided solid material removed from said second-named contacting zone downwardly through an elongated vertical column having a height sufiicient to develop a hydrostatic pressure at the bottom thereof greater than the pressure maintained in said first-named contacting zone, introducing a fluidizing gas into said column and thereby maintaining said finely-divided solid material during passage downwardly through said column in a freely flowing fluidized state, and transfering said finely-divided solid material from the bottom of said column into said first-named contacting zone solely by the use of said hydrostatic pressure.

2. A method of countercurrently contacting a finely divided solid with a gas or vapor which comprises introducing finely divided solid material into the lower portion of a first contacting zone, introducing a gas or vapor from the upper portion of a second contacting zone into the lower portion of said first contacting zone for maintaining a suspension of solid particles in said first contacting zone and for obtaining intimate mixing of the solid particles and gas or vapor, removing solid particles from said first contacting zone and passing the removed solid particles downwardly as a dense fluidized column for developing hydrostatic pressure at the base thereof, introducing solid particles from the bottom of said column at a pressure higher than that at the top of the column into the lower portion of said second contacting zone, introducing a gas or vapor into the lower portion of said second contacting zone for suspending the solids introduced-thereto from said column, and selecting a relatively low velocity of passage of the mixture through said second contacting zone so that the time of residence of the solid particles within said second contacting zone is materially greater than the time of residence of the gas or vapor therein and there is a general tendency for the solid particles to settle out of the gas or vapor, removing solid particles from said second contacting zone and passing the removed solidparticles downwardly as a dense fluidized column for developing hydrostatic pressure at the base thereof and withdrawing from the upper part of said first contacting zone the gas or vapor which was introduced into the lower portion of said second contacting zone and then passed through said first contacting zone.

3. A method according to claim 2 wherein the bulk density of each mixture in said contacting zones is reduced by the introduced gas or vapor and is less than the bulk density of each mixture in said columns.

4. A method of contacting gaseous fluid with finely divided solid material which comprises passing gaseous fluid into a first contacting zone, contacting the gaseous fluid with finely divided solid material, removing gaseous fluid from the upper portion of said first contacting zone, passing at least a portion of the gaseous fluid so removed to the bottom portion of a second contacting zone, contacting the gaseous fluid in said than the-pressure difierential between said second contacting zone and said first contacting zone and transferring the finely divided material from the bottom of said column into said first contacting zone.

JOHN C. MUNDAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS I Number Name Date 1,577,534 Miller Mar. 23, 1926 2,231,424 Huppke Feb. 11, 1941 2,247,126 Hemminger June 24, 1941 2,252,740 Teter Aug. 19, 1941 2,253,486 Belchetz Aug. 19, 1941 2,286,447 Thomas June 16, 1942 2,290,580 Degnen et al July 21, 1942 2,296,386 Hemminger Sept. 22, 1942 2,296,722 Marancik et al Sept. 22, 1942 2,304,827 Jewell Dec. 15, 1942 2,323,899 Day et al July 13, 1943 2,326,166 Pier et a1 Aug. 10, 1943 2,339,874 Nysewander Jan. 25, 1944 2,349,575 Voorhees May 23, 1944 2,367,281 Johnson Jan. 16, 1945 FOREIGN PA'I'ENTS Number Country Date 533,037 Germany Sept. 8, 1931