US2458165A

US2458165A - Method and apparatus for conversion of fluid hydrocarbons

Info

Publication number: US2458165A
Application number: US735326A
Authority: US
Inventors: Herbert K Holm
Original assignee: Socony Vacuum Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1947-03-18
Filing date: 1947-03-18
Publication date: 1949-01-04
Anticipated expiration: 1966-01-04

Description

Jan. 4, 1949. H. K. HOLM v 2,458,165

METHOD AND APPARATUS FOR CONVERSION OF FLUID HYDROCARBONS Filed March 18, 1947 4 Sheets-Sheet l HOPPER O INVENTOR.

HfFBERT KHOLM Maw A GENT 0 AYTOFNEY.

Jan. 4, 1949. H. K. HOLM 2,458,165

' METHOD AND APPARATUS FOR CONVERSION OF FLUID HYDROCARBONS Filed March 18, 1947 4 Sheets-Sheet 2 INVENTOR.

HERBERT K HOZM.

JAMQW AGENT 0i? ATTORNE).

Jan. 4, 1949. H. K. HOLM 2,458,165

METHOD AND APPARATUS FOR CONVERSION OF FLUID HYDROCARBONS Filed March 18, 1947 4 Sheets-Sheet 3 INVENTOR. HERBERT r HOLM 9M am l- AGENT 0R ATTORNEY Patented Jan. 4, 1949 METHOD AND APPARATUS FOR CONVER- SION OF FLUID HYDROCARBONS Herbert K. Holm, Chicago, Ill., assignor to Socony- Vacuum Oil Company, Incorporated, a corporation of New York Application March 18, 1947, Serial No. 735,326

14 Claims. 1

This invention has to do with a method and apparatus for conversion of fluid hydrocarbons in the presence of a particle-form solid contact material which may or may not be catalytic in nature.

Exemplary of the processes to which this invention may be applied are the catalytic cracking conversion of high boiling fluid hydrocarbons, the catalytic hydrogenation, dehydrogenation, aromatization, polymerization, alkylation, isomerization, reforming, treating or desulphurizing of selected hydrocarbon fractions. Also exemplary are the thermal cracking, viscosity breaking and coking of hydrocarbon fractions in the presence of heated inert, solid materials.

Typical of such processes is the catalytic cracking conversion of hydrocarbons, it being well known that high boiling fluid hydrocarbons may be converted to lower boiling gaseous, gasoline containing hydrocarbon products by exposure to a suitable adsorbent type catalytic material at temperatures of the order of about 800 F. and higher and at pressures usually above atmospheric. Sucha process has recently been developed commercially into a continuous cyclic process wherein the solid catalyst is passed cyclically through a conversion zone wherein it is contacted with fluid hydrocarbons to eilect the conversion thereof and through a regeneration zone wherein it is contacted with a combustion supporting gas such as air which acts to burn ofi from the catalyst a carbonaceous contaminant deposited thereon in the conversion Zone.

This invention is particularly concerned with such cyclic conversion processes or gas-solid connature of natural or treated clays, bauxite, inert carriers upon which catalytic materials such as metallic oxid'es have been deposited or certain synthetic associations of silica, alumina or silica and alumina to which small amounts of. other materials such as metallic oxides may be added for special purposes. In processes wherein the contact material is not catalytic in nature its purpose is usually that of a heat carrier and may take any of a number of forms, for example, spheres or particles of metals, stones or refractory materials such as mullite, zirkite, or corhart material. In order to permit practical rates of gas flow through the contact material which is maintained as a substantially compact column in the conversion zone, the contact material should be made up of particles falling within the size range of about .005 to 1 inch in diameter and preferably .03 to 0.5 inch in diameter.

In such processes wherein the direction of gas flow through the reaction zone is countercurrent to the downward flow of the contact material, the maximum rate of gas flow should be limited to that which will not cause boiling of the contact material or serious interference with its flow otherwise serious difllculties arise such as channeling of the solid and gas flow and excessive attrition of the solid material. In many processes such as, for example, the conversion of liquid hydrocarbons to lower boiling gaseous products it is desirable to pass the reactant fluid downwardly through the conversion zone concurrently with the contact material flow. In such processes a serious difliculty arises in the withdrawal of gaseous reactants from the contact material column within the conversion zone. In one form of operation practiced heretofore a row of inverted, spaced, collecting troughs was positioned in the column of contact material within the lower section of the reactor and gas was withdrawn through suitable pipes extending under the ends of the troughs. Such an arrangement is unsatisfactory due to serious entrainment of contact material in the gaseous streams withdrawn from'the ends of the collecting troughs.

A major object of this invention is the pro- ViSlOl in a process wherein a gaseous material is contacted with a substantially compact column of particle-form contact material of an improved method and apparatus for withdrawal of gas from said column without substantial entrainment of contact material particles.

Another object of this invention is the provision of an improved method and apparatus for conversion of a high boiling fluid hydrocarbon to a lower boiling gaseous hydrocarbon product in a confined zone in the presence of a substantially compact column of contact material particles flowing downwardly through said zone in the direction ofrthe reactant flow.

A specific object is the provision in a hydrocarbon conversion process wherein the contact material moves downwardly as a substantially compact column of solid particles concurrently to the fluid reactant flow of a practical method and apparatus for withdrawal of gaseous conversion products from said column in the conversion zone without substantial entrainment of contact material particles in the eilluent gas stream.

These and other objects of this invention will become apparent from the following detailed description of the invention. Before proceeding with the description, certain expressions employed herein in describing and in claiming this invention will be defined. The term gaseous" as used herein, unless specifically otherwise modifled, is intended broadly to cover material existing in the gaseous phase under the particular operating conditions involved regardless of what may be the normal phase of that material under ordinary atmospheric conditions. The expression contact material, unless otherwise specifically modified, is used herein in a broad sense to cover any solid material having suitable heat carrying and stability properties for the particular process application in which it is employed, and the expression is intended to broadly cover catalytic and non-catalytic materials.

The invention may be most readily understood by reference to the drawings attached hereto of which Figure l is an elevational view of an arrangement of a cyclic conversion system to which this invention is applied, Figure 2 is an elevational view, partially in section, of a conversion vessel constructed according to this invention, Figure 3 is a vertical view, in section, of a modifled form of gas collecting trough, Figure 4 is a similar view of still another modified form of gas collecting trough. Figure 5 is an isometric view showing the stacking arrangement of troughs shown in Figure 2, and Figure 6 is a a graphical representation of certain pressure drop data obtained in connection with the apparatus of Figure 2. All of these drawings are highly diagrammatic in form.

Turning now to Figure 1 there is shown a conversion vessel [0, a regeneration or reviviflcation vessel II and conveyors l2 and i3 for transfer of contact material between the conversion and regeneration vessels. In operation particle-form contact material is supplied from hopper 40 through gravity feed leg 4| into the upper section of the conversion vessel [0. Used contact material is withdrawn from the lower end of vessel l0 through drain conduit I4. The rate of contact material flow is controlled by valve ii on conduit i4 so that a substantially compact column of contact material is maintained within the conversion zone. The hydrocarbon charge tovessel i0 may exist in the gaseous phase or liquid phase or both. The charge may be heated and completely or partially vaporized in a suitable charge preparation system [6 which may be of conventional design. Heated charge vapors may be admitted to the upper section of the conversion zone through conduit l1 and heated liquid charge may be admitted through conduit l8. Gaseous conversion products are withdrawn, separately of the contact material, from the lower section of the conversion zone through conduit is through which it passes to a conventional product recovery system 211. An inert seal gas, such as steam or flue gas may be admitted through conduit 2| into aseal zone maintained at the upper end of vessel ill for the purpose of preventing hydrocarbon escape through the gravity feed leg. The rate of seal gas introduction may be so controlled by means of diaphragm actuated valve 22 and differential pressure control instrument 23 as to maintain a seal gas pressure in the seal zone slightly-above the hydrocarbon pressure in the upper section of the conversion zone. An inert purge gas such as steam or flue gas may be introduced into the contact material column below the level of gaseous reactant outlet l3 through conduit 24 for the purpose of purging gaseous reaction products from the outflowing used contact material. The used contact material is transferred to conveyor l2, which may be a continuous bucket elevator for example, to the upper end of regeneration vessel H. The regeneration vessel shown is of the multistage type, well adapted for the regeneration of spent cracking catalysts. Air or oxygen containing gas is introduced from manifold 25 into several superposed burning stages through

inlet conduits

26, 21 and 23. Flue gas may be withdrawn from these stages through

conduits

23, 30 and 3l all connecting into outlet manifold 32. The contact material temperature may be controlled by passing a suitable cooling fluid through cooling tubes located in vessel l I between the burning stages. Cooling fluid may be introduced into the cooling tubes (not shown) through communicating

inlets

33 and 34 and withdrawn therefrom through communicating outlets 35 and 38. Regenerated contact material is withdrawn from vessel ll through drain conduit 31 through which it passes to conveyor |3. The hot regenerated contact material is transferred by conveyor l3 to reactor supply hopper 4|). While the regenerator described hereinabove is of the multistage type, it will be understood that other types of regenerators adapted for regenerating contact materials may be employed within the scope of this invention. The type of regenerator or reviviflcation vessel to be employed will vary depending upon the particular process involved. Any apparatus adapted to condition the contact material to a state satisfactory for re-use in the particular conversion process involved is contemplated to be within the scope of this invention. It should be further understood that this invention is not considered as limited to any particular positional arrangement of conversion and regeneration vessels or to the particular apparatus described .hereinabove for contact material introduction into the conversion vessel.

The improvement of this invention as applied to the conversion vessel III is shown in Figure 2, wherein I0 is the conversion vessel having solid inlet 40 at its upper end and outlet I4 at its lower end. A partition 43 is positioned across the upper section of the vessel Ill to provide a seal chamber 44 in the upper end of vessel It. Contact material passes from seal chamber 44 onto the surface ofthe contact material column 45 in the conversion chamber therebelow through uniformly distribuated tubes 46 which depend from partition 43. The partition 43 and tubes 46 combine to provide a gas distribution space 41 above the contact material column in the conversion chamber. vaporized hydrocarbons may be introduced into the gas space through conduit l1. Liquid hydrocarbons enter through conduit l3 which extends across the vessel and is closed on its end within the vessel. A number of branch pipes such as 48 and 49 may connect into the conduit it! within column 45. Contact material is withdrawn from the bottom of the conversion zone through a.

number of uniformly distributed tubes 55 depending from a horizontal partition 54. The streams from tubes 55 are proportionately combined into a smaller number of streams flowing through orifices 56 in still another partition within the lower section of vessel l and the streams from orifices 56 are proportionately combined into a single discharge stream flowing from the conversion vessel in conduit 14. It will be noted that the orifices in partition 51 and the tubes in partition 54 are arranged in circular rows and that the number of orifices within partition 5,! is less than the number of tubes depending from partition 54 and that the orifices 56 are horizontally staggered with respect to the tubes 55. By the gradual proportionate combination of streams into a single discharge stream as described hereinabove uniform withdrawal of contact material from all portions of the cross-sectional area of the conversion vessel is insured. The number of rows of partitions with orifices or depending tubes employed depends, of course, on the horizontal cross-sectional area of the vessel involved. While for vessels of circular cross-sectional shape, the tubes in each partition may be conveniently arranged as concentric circular rows of tubes. On the other hand, for a vessel of rectangular cross-sectional shape the tubes in each partition may be conveniently arranged spaced apart parallel rows of tubes extending across the vessel.

Within the lower section of vessel It! there is positioned an arrangement of baflles which comprises a vertical series of superimposed layers of inverted troughs which in Figure 2 are in the shape of angle irons 60 placed one above the other in a criss-cross manner. irons 60 in any given layer are spaced horizontally apart and extend in parallel horizontally across the vessel in a direction transverse to those angle irons in adjoining layers. Along the heel of each angle iron there are provided a series of orifices 6| so positioned that in any angle iron the orifices are covered by angle irons crossing thereabove. It has been found preferable for the orifices to be so arranged that in any angle iron the orifices are below the closed part of the angle iron crossing thereabove, rather than directly below an orifice in the angle iron above. In order to prevent leakage of solid particles through the edge of the orifices in the angle irons 60, it has been found desirable to construct the orifices in the form of small chimneys as shown in Figure 1. These chimneys may extend a short distance above the heel of the angle iron if desired. It will be noted that the size of the orifices 6! increase in stepwise fashion for the successive layers of angle irons in a downward direction. The two lowermost layers of angle irons are provided along their bases with vertical skirts 63. All angle irons are provided with end plates 64 to prevent entrance of solid pa ticles under the ends of the angle irons.

While the form shown in Figure 2 is a preferred form of the invention fiat topped inverted channels such as trough 80 in Figure 3 may be substituted for angle iron 60. In the case of fiat topped channels simple orifices 8| may be provided instead of the chimney-type orifices 6| of Figure 2. A preferred form of trough construction is shown The angle 6 thereof than on the other layers of troughs. It should be understood that the term trough as employed herein in describing and claiming this invention is employed in a broad sense as covering both angle irons of the type shown in Figure 2 and trough constructions such as are shown in Figures 3 and 4 and troughs of other practical cross-sectional shapes. It should also be understood that the term orifices is used herein in in Figure 4 wherein is shown a sectional view of a gable-roofed trough 82 which may be substituted for angle irons 60. A series of chimneytype orifices such as 83 are provided along the gable-roof of trough 82. When such troughs are employed it is desirable to provide deeper vertical skirts on the troughs of the two lowermost layers a generic sense as covering simple holes such as at 8| in Figure 3 or the chimney-type of orifice shown at 6| and at 83 in Figures 2 and 4 respectively.

In Figure there is shown an isometric view of two layers of stacked angle irons such as are shown in the apparatus of Figure 2. Like elements in Figures 2 and 5 bear, like numerals.

Turning again to Figure 2, there is provided above the top layer of orifice containing angle iron troughs a layer of similar angle irons 82 in which no orifices are provided. The angle irons 62 serve to prevent flow of solid particles through the orifices in the layer of angle irons covered by angle-iron 62.

Below the lowermost layer of angle irons 60 there is provided a row of spaced gable-roofed troughs 65 running across the vessel transverse to the angle irons immediately thereabove. Chimney-type orifices 66 are provided in the gable roofs of troughs 65 to communicate them with the lowermost layer of angle irons. The orifices 66 are as large as or preferably larger than those in the lowermost layer of angle irons.

Flanged nozzles 61 are provided along the vessel shell adjacent opposite ends of the troughs 65. Flanged sleeves 68 of approximatel the same shape as troughs 65 are provided to slide through nozzles 61 and under the opposite ends of troughs 65. The sleeves are connected to nozzles 61 by flanges 69 so that they serve both as supports for troughs 65 and as passages for flow of gas from under the troughs 65 out into the header boxes 10 which enclose the nozzles 61 and open sleeves 68. Gas outlet conduits H are connected into header boxes ID.

The above described arrangement is such that there is provided in the lower section of the vessel ID a substantially continuous tortuous solid-particle-free gas flow passage which is in gas flow communication with the contact material column at a series of vertical levels and which is in gas flow communication with gas outlet conduits positioned outside of vessel I0,

In operation of the apparatus shown in Figure 2 contact material enters the seal chamber 44 through conduit 48 and passes from the bottom of the seal chamber through tubes 46 onto the surface of the contact material column in the conversion chamber. The contact material fiows downwardly through the conversion chamber as a substantially compact column of gravitating particles and passes through tubes in partition 54 and orifices 56 in partition 51 to the drain conduit l4. The rate of solid flow is temperature conditions to gaseous hydrocarbon The hydrocarbon reactant is converted under suitable 7 products as it passes downwardly through the conversion chamber. The gaseous conversion products upon reaching the uppermost layer of angle irons tend to become disengaged from the solid column at surfaces formed by the normal angle of repose of the solid material under the angle irons. A small portion of the gaseous products become disengaged at the disengaging surfaces under the angle irons 62 and then pass into the gas space provided by these angle irons.

.The remainder of the gaseous products pass downwardly through the solid column between the spaced angle irons, a portion of the gas being disengaged from the column and collected under the angle irons at each row thereof. The gas collected under any given row of angle irons passes downwardly through the chimney-type orifices in the angle irons therebelow to Join the gas collected under the latter angle irons. Thus the gas collected under all rows of angle irons is gradually combined so that the stream of gas passing from the lowermost row of angle irons through orifices 66 to the outlet troughs 65 comprises most of the gaseous hydrocarbon product except for a small amount of gas which passes down through the column between troughs 65 and is collected under troughs 65. The total gaseous product collected under the angle irons then passes through sleeves 68 to manifold boxes 10 from which it is withdrawn through conduits H.

An inert purge gas such as steam or line gas may be introduced throu h conduit 24 to the space below partition 54. The purge gas passes upwardly through tubes 55 and the bed of contact material between partition 54 and troughs 65 and is finally collected under troughs 65 along with the gaseous hydrocarbon product. An inert seal gas such as steam or fiue gas may be introduced through conduit 2| into seal zone 44 at a rate sufficient to maintain a higher gaseous pressure in zone 44 than in the space 41 of the conversion chamber. In this manner escape of gaseous hydrocarbons through the contact material feed leg is prevented.

By the above described method and apparatus there is provided in the lower section of the conversion vessel a total amount of gas-solid disengaging surface area which is far in excess of the horizontal cross-sectional area of the column of contact material above the bafiling. It is therefore possible by the described method to pass gasdownwardly through the column in the conversion zone at a rate which would be suflicient to entrain the contact material and interrupt the solid column flow, if the gas flow were upward, and still effect an upward disengagement of gas from the solid column in the lower section of the conversion zone without sub-tantial entrainment of solid particles and without interruption of the solid column fiow. In order to accomplish the proper gas-solid disengagement and in order to prevent "boiling of the contact material column and particle entrainment under the uppermost rows of angle iron it is of great importance that the disengaging conditions be maintained substantially uniformunder all the angle irons in all the vertically spaced layers thereof. It has been found that this result may be accomplished by proper proportioning of the size of the orifices in the successive rows or layers of angle irons. Broadly speaking this has been found to involve the provision of orifices in the angle irons which increase in size in a stepwise fashion for successive layers of angle irons in a downward direction. The size of the orifices in the uppermost layer of angle irons containing orifices should be such as to cause a pressure drop due to the downward flow therethrough of the amount of gas collected under angle irons 52 of the uppermost layer, which pressure drop is equal to that caused by the flow of the residual gas not collected under the uppermost layer of angle irons through that vertical portion of the solid column lying between the base of angle irons 62 and the base of the angle irons in the next lower layer of angle irons. The orifices in succeeding layers of angle irons should be similarly proportioned so as to create a pressure drop due to the gas flow therethrough which will balance that through the solid column between layers. Since as the gas works downwardly, the amount of gas flowing through the orifices gradually accumulates and becomes greater and since the amount of gas flowing through the column at corresponding levels gradually decreases, the size of the orifices 6| in successive downward layers must gradually increase. The increase in orifice size is of course limited to that maximum size which will still be covered by the base of the angle thereabove. In some cases, by the time the lowermost rows of angle irons is reached, the orifice size required is greater than the maximum allowable. In order to provide the proper pressure drop balance in such cases, vertical skirts are provided along the base of the angle irons in these lowermost layers in order to increase the height of column and thereby increase the pressure drop due to gas flow through the solid column between these layers. In this manner the desired pressure drop balance may be obtained with a much smaller increase in orifice size in the lowermost layers of angle irons than wouldotherwise be required. In some cases with such construction two successive layers having the same orifice size but different heights may occur. While in general it has been found desirable to provide vertical skirts on the two lowermost layers of angle irons, skirts may be provided on more than the two lowermost layers of angle irons if desired and even on certain of the intermediately positioned layers of angle irons. It will be understandable from the above that while in general, the size of the orifices increase to some extent with each successive layer of angle irons in a downward direction, on some occasions the increase in orifice size may occur only in groups of layers rather than for each successive layer. For example, in a given application the orifice diameters beginning with the top layer and working down might be 0.0, 0.4", 0.5" 0.6" 0.7" 0.7", 0.8", 0.8", 0.9" 1.0" and so on. It should be understood that the expressions in stepwise fashion or "stepwise" are employed in the claims in the broad sense as covering both a change in orifice size or in flow restriction for every successive layer of angle irons and as covering a change in orifice size or in flow restriction for groups of layers of angle irons with change in position of the layer in a downward direction as described hereinabove.

The exact dimensions and the number of layers of the baflie structure described hereinabove is dependent upon the particular hydrocarbon reaction, reactant rate, contact material and pressure and temperature conditions involved of the particular application to which the invention is applied. Moreover the number of layers of angle irons is to some extent dependent upon the dimensions and spacing of the angle irons employed. In general, angle irons measuring from about one inch to six inches across the base may be employed. Preferably the angle irons should measure between two to four inches across the base. The sides of the angle irons should form a slope with the horizontal of at least about 40 and preferably of the order of 60 or greater. The angle irons should be so spaced in each layer as to leave a passage for contact material fiow therebetween measuring at least about five times and preferably ten times as wide as the largest particle of the contact material. The number of layers of angle irons should be suflicient to provide a-total gas-solid disengaging-area which will limit the linear velocity of the gas at the disengaging surfaces below that which will boil or substantially entrain the solidpartlcles. The gas velocity which will entrain and boil solid particles may be determined by calculation from published equations and data or it may be determined by simple routine experiments using the particular contact material and gas that are involved in the process application under consideration. In general it has been found for catalytic cracking conversion operations that at least about 4 layers of angle irons should be used.

The rate of decrease in orifice size from layer to layer of angle irons is dependent upon the particular angle iron size and spacing and upon the particular contact material and upon the number of layers of angle irons involved.

The number of layers of angle irons and the. 30 proper sizing of the orifices to be employed may be determined in the manner now to be described.

Once having settled upon the total rate of flow of gaseous hydrocarbon products and upon the diameter of the conversion vessel for a specific application, then the amount of disengaging surface area required may be calculated in the manner described hereinabove. The amount of disengaging surface provided by each angle iron may be determined by multiplying the length of the two converging lines drawn downwardly from opposite sides of the base of the angle iron at an angle of about 30 degrees by the length of the angle iron. Then having selected a suitable angle iron spacing, the total number of layers of the angle irons to provide the required disengaging area may be easily calculated. Then since an equal amount of gas is to be collected under each layer of angle irons the total amount of gas Q to be collected per unit of time under any layer of angle irons may be readily determined by dividing the total rate of gaseous reactant withdrawal by the number of layers of angle irons. The rate of gas flow through the column or through the passage provided by the angle irons at any level is then fixed. For example, if there are twelve layers of angles, the quantity/of gas flowing through the orifices in the fifth layer from the top is 4Q and the quantity flowing through the solid column at the same level must be 8Q. The next step is to determine the pressure drop due to gas flow through the column between each set of two layers of angle irons. This pressure dropmay be approximately calculated by known methods and on the basis of published data and equations. Preferably it may be determined experimentally in a small model employing closed angle irons of-the same size and spacing of those to be employed in the conversion vessel. In Figure 6 there is shown graphically the data obtained experimentally in such a small model employing angle irons measuring 2 across the base and 1.97" in height spaced side by side in each layer on 2%" centers. In Figure 6 the abscissa represents the pressure drop for various gas rates through the same model containing a bed of the contact material but not containing any angle irons, and the ordinate represents, for the same corresponding gas rates, the ratio of the experimentally determined pressure drop through the bed containing the layers of closed angle irons to the pressure drop for the same gas rate through the angle free bed. The orifices in the angle irons were closed in the experiment to insure passage of all gas charged through the bed. InFigure 6', two curves are given, one for spherical gel type catalyst having an average diameter of about 0.10 inch and the other for pelletted catalyst having an average diameter of about 0.10 inch. Having calculated the pressure drop due to gas fiow through the bed between successive layers of angle irons the orifice size for the angle irons in any given layer to balance the corresponding pressure drop in the contact material bed may be calculated by meansof the simple orifice equation:

-i A CKIZQH where His the pressure drop in the bed across the angle iron in feet of gas flowing, Q is the quantity of gas flowing through the orifice in cubic feet per second, g is the acceleration due to gravity=32.2 feet per second, per second A is the area of the orifice in square feet and C is the orifice coeillcient. The'value of C should be determined experimentally. A value of 0.78 for C has been found satisfactory for the chimneytype orifices.

As an example of the application of the above calculations, in a process involving disengagement of a gaseous hydrocarbon product of about molecular weight at a temperature of 875 F. and pressure of 5#/in. Gauge from a particle form catalyst of 45 lbs. per cu. ft. density and 0.12 inch average diameter, it was determined that the linear rate of gas flow at the disengaging surfaces to avoid entrainment and boiling of the solids should be about 2 feet per second maximum. The angle iron arrangement described in connection with Figure 6 was employed. On the basis of this arrangement it was found that a gas disengaging rate of about cubic feet per minute per square foot of vessel cross-sectional area was possible. It was calculated that 12'layers of angle irons would provide sufllcient disengaging surface for the total gas flow. The orifice diameter in inches for successive layers of angle irons beginning with the top layer were calculated to be as follows: no ports in top layer, 0.268", 0.395", 0.505", 0.605", 0.710", 0.824", 0.943", 1.078", 1.250", 1.250", 1.625. The angle irons in the two lowermost layers were provided with a skirt measuring inch in height along their bases.

It has been found that in general for hydro carbon conversion operations, the total horizontal cross-sectional area of the orifices in the lowermost layer of angle irons should be at least 2 times and preferably from 2 to 50 times that of the orifices in the uppermost layer of angle irons which contain orifices.

The method and apparatus of this invention may be employed in a wide variety of processes involving contact of gas with a column of particleform solid material. The invention is particularly applicable to catalytic processes for the cracking conversion of liquid or vaporous hydrocarbon charges or both. In general such hydrocarbon conversion operations are conducted under temperatures within the range about 800 F. to

- i100 l t, the higher temperatures being employed 600 F.-900 F. and all or part of the heat required for the conversion may be carried into the conversion zone in the catalyst.

It should be understood that the specific examples of apparatus dimensions and of operating conditions and the examples of application of this invention given he'reinabove are intended as illustrative and should not be construed as limiting the scope of this invention except as it may be limited by the following claims.

I claim:

1. A method for conversion of fluid hydrocarbons in the presence of a particle-form contact mass material which comprises: passing said particle-form contact material at suitable temperatures for said conversion downwardly through a confined conversion zone as a substantially compact column of downwardly gravitating solid particles, introducing a fluid hydrocarbon charge into said conversion zone and passing it downwardly within said column to effect conversion of said hydrocarbon charge to gaseous hydrocarbon products, baiiling the solid particle flow in the lower portion of said column to form a continuous tortuous solid-free passage for gas-flow through a vertical section of said column, said passage being in free gas-flow communication with said column at a plurality of gas-solid disengaging surfaces at a series of vertical levels within the lower section of said column, collecting said gaseous hydrocarbon products from said column into said passage for gas-flow at all of said disengaging surfaces at said series of versaid column at a series of vertically spaced levels, collecting said gaseous hydrocarbon products from said column into said passages at all of said series of vertically spaced levels, causing the gas collected at any level in said passages to flow downwardly to Join gas'collected at lower levels in said passages, subjecting the downward gasflow in saidpassages to a stepwise decrease in restriction in a downward direction so as to insure the collecting of gas into said passages from said column at a substantially uniform rate at all of said vertically spaced levels and withdrawing from said conversion zone at a level near the lower extremities of said passages as at least one con- I flned stream the combined gas collected in said passages from all of said levels.

3. A method for conversion of fluid hydrocarbons in the presence of a particle-form contact mass material which comprises: passing said particle-form contact material at suitable temperatures for said conversion downwardly through a confined conversion zone as a substantially compact column of downwardly gravitating solid particles, introducing a fluid hydrocarbon charge into said conversion zone and passing it downwardly within said column to ef- -fect conversion of said hydrocarbon charge to spaced levels, causing the gas collected at any tical levels, causing the gas collected into said passage at any level to flow downwardly to join the gas streams collected at lower levels, subjecting said gas flowing downwardly in said passage for gas-flow to a stepwise decrease in flow restriction as it moves downwardly through said series of vertical levels so as to provide substantially uniform disengagement of gas from said column at all of said disengaging surfaces at said series of vertical levels, and withdrawing the combined stream of gas from all of said disengaging surfaces from said conversion zone.

2. A method for conversion of fluid hydrocarbons in the presence of a particle-form contact mass material which comprises: passing said particle-form-contact material at suitable temperatures for said conversion downwardly through a confined conversion zone as a substantially compact column of downwardly gravitating solid particles, introducing a fluid hydrocarbon charge into said conversion zone and passing it downwardly within said column to effect conversion o f said hydrocarbon charge to gaseous hydrocarbon products, baiiling the solid particle flow in the lower portion of said column to form a plurality of substantially continuous, tortuous particle-free passages for gas-flow through a vertical portion of said column near its lower end, said passages permitting gas entrance thereinto from level to flow in a general downward direction in said tortuous passages to Join gas collected at other levels. eflecting a stepwise reduction in the resistance to gas-flow through said passages such as to cause a stepwise decrease in the pressure drop due to gas-flow between any of said levels in a downward direction, and withdrawing the combined gas collected from all of said levels from the lower extremities of said passages as at least one confined stream.

4. A method for conversion of fluid hydrocarbons in the presence of a particle-form solid contact material comprising: maintaining a substantially compact column of downwardly moving particle-form contact material within a confined conversion zone, replenishing said column at its upper end with fresh contact material at a suitable conversion temperature, withdrawingused contact material from the lower end of said :column, introducing a heated fluid hydrocarbon charge into the upper section of said conversion zone and passing it downwardly within said column to effect its conversion to gaseous hydrocarbon products, baflling the solid flow in the lower section of said column at a plurality of levels to form a plurality of spaced gas collecting zones from which direct solid flow is excluded at a series of vertical levels within the lower section of said column, collecting said gaseous products from said column in said gas collecting zones at all of said levels, passing the gas collected in said collecting zones at any level downwardly as confined solid excluded streams to the collecting zones next below so as to accomplish the gradual :combining of gas collected at said series of levels, subjecting the gas flowing downwardly between collecting zones to flow restriction which decreases in stepwise fashion from level to level of collecting zones in a downward direction in such a manner as to accomplish substantially uniform collection of gas from said column at all of said levels and withdrawing the combined gas as confined streams from the lowermost collecting zones. X

5. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of particle-form contact material which apparatus comprises: a substantially upright conversion Vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a fluid hydrocarbon charge into the upper section of said vessel, baflie means within a lower portion of said vessel, said bailie means comprising layers of inverted troughs, the uppermost layer being positioned within the lower section of said vessel, the troughs in each layer being spaced apart and extending horizontally across said vessel in a direction transverse to those in the adjoining layers, each of said troughs, excepting those in the top layer, having a series of orifices along its roof, said orifices being so located that in any trough each orifice is covered by a trough in the layer above, the size of the orifices in the troughs in said layers increasing in stepwise fashion with the position of the trough in a downward direction, and means to withdraw gas from under only the lowermost layer of troughs to a location outside of said vessel.

6. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of particle-form contact material which apparatus comprises: a substantially upright conversion vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a fluid hydrocarbon charge into the upper section of said vessel, baflle means within only a lower portion of said vessel, said bafiie means comprising criss-crossed layers of inverted troughs, the troughs in each layer being spaced apart and extending horizontally across said vessel in a direction transverse to those in the adjoining layers and the uppermost layer being positioned at a level within the lower section of said vessel, a series of orifices along the troughs in each layer excepting the uppermost layer and said orifices being so located that in any trough they will be covered by troughs in the layer next above, said orifices increasing stepwise in size with downward position of the layers of troughs and the total horizontal crosssectional area of the orifices in the lowermost row of said troughs being within the range of 2 to 50 times that provided by the orifices in the row of troughs next below the uppermost layer ahd means to withdraw gas from only the lowermost layer of troughs to a location outside of said vessel.

7. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of particle-form contact material which apparatus comprises: a substantially upright conversion vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a fluid hydrocarbon charge into the upper section of said vessel, baiile means within a lower portion of said vessel, said bafile means comprising at least 4 superposed layers of criss-cross inverted troughs, the troughs in any given layer being parallel and horizontally spaced apart and extending horizontally across said vessel in a direction transverse to troughs in adjoining layers and the uppermost layer being positioned at a level within the lower section of said vessel, a series of orifices along the troughs in all layers excepting the uppermost and said orifices being so located that in any trough they.

will be directly below the closed part of the next above trough crossing thereover, said oriflces being equal in size in the troughs in any given layer and increasing in size stepwise for succeeding layers in downward direction and said orifices in the lowermost layer of troughs providing a total horizontal cross-sectional area at least equal to 2 times the area provided in the row of troughs next below the uppermost layer, at least one inverted trough of substantially greater height than said first named troughs positioned below and communicating with said troughs in said lowermost layer, and conduit means to withdraw gas from said last named trough.

8. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of particle-form contact material which apparatus comprises: a substantially upright conversion vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a fluid hydrocarbon charge into the upper section of said vessel, bafile means within a lower portion of said vessel, said baffle means comprising layers of inverted troughs, the troughs in each layer being spaced apart and extending horizontally across said vessel in a direction transverse to those in the adjoining layers and the uppermost layer being positioned at a level within the'lower section of said vessel, each of said troughs, except those in the top layer, having a series of orifices along its roof, said ori ces being so located that in any trough each ori ce is covered by a trough in the layer above, the size of the orifices in the troughs in said layers increasing in stepwise fashion with the position of the trough in a downward direction, a row of spaced inverted troughs of substantially reater height and Width than said,first named troughs positioned within said vessel below the lowermost layer of said first named troughs, and communicating with said troughs in said lowermost layer through orifices in the roofs of said last named troughs, and duct means to withdraw gas only from under said last named troughs.

9. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of particle-form contact material which apparatus comprises: a substantially upright conversion vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a fluid hydrocarbon charge,

' spaced horizontally and being tranverse those of said orifices in said layers of angle irons increasing in size in stepwise fashion for succeeding layers in downward direction, and members defining a passage for gas withdrawal from under the angle irons in the lowermost layer thereof to a location outside of said vessel, remaining layers of angle irons communicating with said location outside said vessel only through the orifices in said lowermost layer. a

10. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of particle-form contact material which apparatus comprises: a substantially upright conversion vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a fluid hydrocarbon charge into the upper section of said vessel, baiile means within only a lower portion of said vessel, said baille means comprising superimposed layers of angle irons positioned with their angles opening their heels and the angle irons in each succeeding layer having a series of orifices along its heel being so located that in any angle iron they will be directly below the closed part of the next above angle iron crossing thereover, said orifices in the angle irons of any given layer being equal in size and the orifices increasing in size in stepwise fashion for succeeding layers in a downward direction, a plurality of gable-roofed troughs of substantially larger size than said an'gle irons positioned'directly below the lowermost layer of angle irons and communicating with said angle irons through orifices in their roofs, and duct means communicating with the space under said troughs for gas withdrawal from said troughs.

11. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of particle-form contact material which apparatus comprises: a substantially upright conversion vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a fluid hydrocarbon charge into the upper section of said vessel,.bailie means beginning and extending downwardly within only a lower section of said vessel, said baiile means comprising superimposed rows of angle irons positioned with their angles opening downwardly, the angle irons in each row being horizontally spaced apart and extending horizontally across said vessel in a direction transverse to those in next adjacent rows, a series of orifices along the heels of all angle irons in all rows excepting the uppermost rowthereof so positioned that in any angle iron the orifices are covered by the angle iron crossing thereover, said orifices being of increasing size in a stepwise fashion for succeedingly lower rows of angle iron, vertical skirts connected along the bases of all angle irons in at least the two lowermost rows to increase theheight of the angle iron members, a reaction product withdrawal conduit outside of said vessel, and passage defining members communicating only the angle irons in the lowermost layer with said withdrawal conduit.

12. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of ,particle-form contact material which apparatus comprises: a substantially upright conversion l6 s vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a'fluid hydrocarbon charge into the upper section of said vessel, bailie means within a lower portion of said vessel, said bafle means comprising superimposed rows of angle irons positioned with their angles opening downward-' ly, the angle irons in each row being horizontally spaced apart and extending horizontally across said vessel in a direction transverse to those in next adjacent rows, the uppermost row of angle irons being positioned at a level within the'lower section of said vessel above said contact material withdrawal means, a series of orifices along the heel of all angle irons in all rows excepting the uppermost row thereof so positioned that in any angle iron the orifices are covered by the angle iron crossing thereover, said orifices being of increasing size in a stepwise fashion for succeedingly lower rows of angle irons so that the total horizontal cross-sectional area of the orifices in the lowermost row of angle irons is within the range 2 to 50 times the area of the orifices in the row next below the uppermost row, vertical skirts connected along the bases of at least the two lowermost rows of angle irons to increase the height of said rows, an external conduit for transfer of gaseous products, and passage defining I means communicating only the lowermost row of angle irons with said external conduit.

13. An apparatus for conversion of fluid hydrocarbons in the presence of a moving mass of particle-form contact material which apparatus comprises: a substantially upright conversion vessel, means to introduce contact material to the upper section thereof, means to withdraw contact material from the lower section thereof, means to introduce a fluid hydrocarbon charge into the upper section of said vessel, bafile means within a a lower portion of said vessel, said baiile means comprising at least 4 superimposed horizontal rows of angle irons positioned with their angles opening downwardly, the angle irons in each row being horizontally spaced apart and extending horizontally across said vessel in a direction transverse to those in next adjacent rows, the uppermost row of angle irons being positioned at a level within the lower half of said vessel, a series of orifices along the heels of allangle irons in all rows excepting the uppermost row thereof so positioned that in any angle iron the orifices are.

below the closed part of the angle iron crossing thereover, said orifices increasingly substantially progressively and uniformly in size for succeed-' ing rows of angle irons in a downward direction and the total orifice area in the lowermost row of angle irons being at least 2 times that in the row next below the uppermost row of angle irons, vertical skirts connected along the bases of all angle irons in at least the two lowermost rows to increase the height of the angle iron members, a header for receiving gaseous products outside of said vessel and members communicating only the lowermost row of angle irons with said header. 14. A method for conversion of fluid hydrocarbons in the presence of a particle-form solid contact material comprising: maintaining a substantially compact column of downwardly moving particle-form contact material within a conflned conversion zone, replenishing said column at its upper end with fresh contact material at a suitable conversion temperature, withdrawing used contact material from the lower end of said column, introducing a heated fluid hydrocarbon 1? charge into the upper section of said conversion zone and passing it downwardly within said column to effect its conversion to gaseous hydrocarbon products, baflling the solid flow in the lower section of said column at a plurality of levels to form a plurality of spaced gas collecting zones from which direct solid flow is excluded at a series of vertical levels within the lower section of said column, collecting said gaseous products from said column in said gas collecting zones at all of said levels, passing the gas collected in said collecting zones at any level downwardly as confined solid excluded streams to the collecting zones next below so as to accomplish the gradual combining of gas collected at said series of levels, restricting the downward gas flow between each of said vertical series of collecting zones in stepwise decreasing amount with downward position of collecting zones, the amount of any two of said series of levels being such as to 18 a cause a pressure drop due to gas flow in said passage substantiafly equal to that of downward gas flow through the column of contact material between the same two levels, and withdrawing the combined collected gaseous products as at least one confined stream from the lowermost collecting zones.

HERBERT K. HOLM.

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

UNITED STATES PATENTS Number Name Date 469,849 Borgarelli Mar. 1, 1892 1,587,582 Galloway June 8, 1926 2,331,433 Simpson et a1. Oct. 12, 1943 2,418,672 Sinclair et a1 Apr. 8, 1947 Evans June 24, 1947