US2759880A - Short-time contacting of fluids with solids in hydrocarbon conversion - Google Patents

Description

Aug. 21, 1956 J. w. BROWN 2,7

SHORT-TIME CONTACTING 0F FLUIDS WITH SOLIDS IN HDROCARBON CONVERSION 2 Sheets-Sheet 1 Filed Oct. 31, 1951 III Ho s'ouos Fia- '2'- James ZffEprozfrz I BmYentor E 5 M CLttoroeg 2,759,880 Patented Aug. 21, 1956 United States Patent Ofiice SHORT-TIME CGNTACTIWG OF FLUIDS WITH SOLIDS IN HYDROCARBON CONVERSION James W. Brown, Elizabeth, N. 1., assignor to Esso Research and Engineering Company, a corporation of Delaware Application October 31, 1951, Serial No. 254,094

9 Claims. (Cl. 196-55) The present invention relates to a method of contacting fluids with subdivided solids for short contact times. More particularly, the invention pertains to improvements in controlling the contact time of solids-fluids contacting processes involving chemical and/or physical changes of the fluids or solids, wherein the solids-fluids contact time must be held to a minimum to prevent overtreating.

In its broadest aspect, the invention provides for intimately mixing fluids and subdivided solids and passing the mixture at contacting conditions over an extended narrowly confined tortuous path at a high velocity conducive to an appreciable separation of fluids from solids on said path caused by changes in the flow direction of the mixture. The invention finds its greatest utility in the upgrading of heavy hydrocarbonaceous residues, such as topped or reduced crudes, tar, pitch, heavy cycle stocks and the like in intimate contact with heat-carrying subdivided solids to form motor fuel and gas oil range hydrocarbons and coke, or, if desired, olefins, diolefins, aromatics, or similar chemical products.

Prior to the present invention it has been proposed to carry out the thermal conversion of heavy hydrocarbonaceous residues in the presence of heat-carrying subdivided solids, such as coke, sand, pumice, clay, silica gel, kieselguhr, etc., which act as heating medium and coke carrier and prevent the deposition of coke on equipment walls. When motor fuels are the principal desired final product, it has been found preferable to conduct the coking process at conditions conducive to the production of predominantly gas oil range hydrocarbonssuitable as feed stocks for catalytic cracking operations. The reason for this is the superior quality of catalytically cracked gasoline as compared with gasoline derived from thermal cracking operations.

High temperatures and, particularly, long contact times are conducive to high conversions, that is, the formation of excessive proportions of thermally cracked gasoline, gas and coke at the expense of the more desirable gas oil range hydrocarbons. However, high temperatures coupled with short contact times yield desirable proportions of gas oils together with small amounts of a high quality gasoline.

Also, the production of chemicals, such as unsaturated and aromatic hydrocarbons from residua of the type mentioned above, requires high reaction temperatures for the formation of these compounds and extremely short contact times at these temperatures to prevent destruction of the desirable compounds :by over-cracking. High-temperature, short-time contacting between highly heated subdivided solids and hydrocarbon residues, there fore, is of utmost importance in petroleum refining.

Heavy residual oils may be cracked by mixing the same with a stream of hot finely divided coke to vaporize short time to effect mild cracking. The solid and gasiform products are passed into conventional gas-solids separation means and from there to any further desired treatment. This type of operation permits low conversions at temperatures as high as 1100 F. by reducing the vapor residence time to about one second. However, the residual oil feed contains a variety of constituents varying widely in cracking resistance. The more refractory of these constituents will, therefore, not be cracked and will remain unvaporized while others are converted within the short contact time provided and should be immediately removed before they are excessively cracked.

When the transfer line efliuent is passed to conventional gas-solids separation means, such as a cyclone separator, cracking of the uncracked feed constituents deposited on the solids continues. However, at the same time the vapors formed likewise undergo further cracking within the cyclone and its solids discharge line at the high temperatures prevailing therein. Inferior products are formed in this manner. This elfect is aggravated when the separated solids are further treated in subsequent soaking, stripping and/0r drying stages operated at similarly high temperatures. The present invention overcomes these difliculties.

It is, therefore, the principal object of the present g invention to provide improved means for preventing overthe oil at least partially while forming a suspension of treatment of reactants in the high-temperature, shorttime contacting of fluids with subdivided solids. A more specific object of the invention is completely to crack heavy residual oils in contact with heat-carrying solids in a transfer line contacting zone without overcracking of desirable cracking products. Other objects and advantages will appear from the description of the invention hereafter wherein reference will be made to the accompanying drawing in which Figure l is a schematical illustration of one form of apparatus adapted to carry out an embodiment of the invention;

Figure 2 is a similar illustration of a different embodiment; and

Figure 3 illustrates schematically a more specific adaptation of the modification of Figure 1.

In accordance with the present invention, fluids and subdivided solids to be contacted are intimately mixed and the mixture is passed at high velocities through a narrowly confined tortuous path at conditions adapted to separate solids from fluids on said path as the result of changes in the direction of flow. Separated solids are thus concentrated on said path and their residence time mai be several-fold that of the fluids passing through said pat The tortuous path may have the form of a pipe or transfer line provided with suitable bafiles causing a frequent change of the direction of flow. A helical or spiral baflie, the turns of which extend at least over a substantial portion of the length of the transfer line contacting zone, is best suited for this purpose. Solids and fluids are separated by centrifugal action, solids accumulating on the periphery of the transfer line and the fluid being accelerated along the axis of the transfer line. Centrifugal separation and solids concentration in the trans fer line may also be accomplished without the use of bafiies by giving the transfer line itself a helical or spiral shape.

In accordance with another embodiment of the invention, the tortuous path may be provided by a plurality of horizontal or upwardly inclined preferably perforated baffles arranged in staggered fashion over at least a portion of the length of the transfer line, the battles covering a portion only of the cross-sectional area of the transfer line. Solids impinging on these baffles are continuously projected back into lower portions of the transfer line while the fluid passes in tortuous flow through the space not occupied by the baflles. The rapid change in the direction of flow of the fluid causes a rough separation of solids from gases. The space directly above each baffie provides a place for separated solids to accumulate so that their treatment may be continued over an extended period of time. Perforations in the baffies allow a small amount of aeration gas to fluidize the solids so accumulated.

When applied to the upgrading of heavy hydrocarbonaceous residues, the hot partially vaporized oil feed is intimately mixed with subdivided heat-carrying solids and the mixture having attained the desired upgrading temperature is passed through a transfer line of the type described above. Vapors present in the mixture originally formed as well as vapors and gases produced by cracking in contact with the heat-carrier solids are continuously being mixed with and separated from the heat carrier along their tortuous path through the transfer line. Actually, cracked vapors are separated from the solids at the instant they are formed, thus reducing their contact time with the heat carrier to an extremely short time insufficient to cause over-cracking. Uncracked liquid constituents, on the. other hand, remain on the separated solids and are thus subjected to cracking conditions for a considerable length of time allowing for efficient cracking of these more refractory constituents. Since cracking and resulting vaporization take place continuously along the path of the transfer line and vapor-solids separation proceeds simultaneously therewith, all constituents of the feed are inherently subjected to optimum conditions of contact time according to their cracking resistance and overcracking of cracked products is greatly reduced or practically eliminated.

In many cases it is desirable to subject the solids and constituents deposited thereon to a long-time cracking treatment in two or more successive stages, while recovering and quenching vapors as they are removed from each stage. For example, the complete conversion of feed may take so long that vaporous products must he removed to prevent overcracking while the solids require prolonged treatment in a subsequent stage. This could be accomplished by passing the entire effluent from each stage, i. e., all the vapors and solids through individual gassolids separators and returning only the solids to the next stage for further treatment. However, at the high temperatures required for the upgrading of residual oils, it is difficult to limit the time needed for separating and collecting the solids and introducing the same into a subsequent stage, when using conventional gas-solids separators. Furthermore, the addition of aeration gas would be necessary after each separation stage to convey the separated solids and to reduce density to the point where a subsequent cyclone would be operable. This would require excessive diluent gas for the complete-process.

In accordance with a specific embodiment of the invention, these difficulties may be eliminated by removing from the central portions of the transfer line reactor, at points suitably spaced in the direction of flow, a substantial portion of the vapors and gaseous products, along with such solids which have not been separated as a result of the intrinsically rough separation taking place in the transfer line. After this gas and vapor removal, the bulk of the solids and the remaining gases and vapors are passed on through the next section of the transfer line to undergo further treatment followed by gas and vapor removal in the manner described and this procedureis repeated until the desired conversion is accomplished. The gases and vapors removed from the individual stages may be quenched to prevent overtreating if desired after separation from entrained solids in conventional separators.

A preferred modification of this embodiment provides for split feed of the total residual oil chargetothe various stages. In this manner, the necessity for introducing extraneous carrier gas between the individual stages is eliminated. Also, the solids/oil ratio required to render the process operable is minimized. Since subsequent feed portions are added only after previous portions have been converted, the amount of liquid on the solids at any one time is substantially less than if the entire feed is introduced at one point. Thus, the stickiness and resulting agglomeration tendency of the solids is reduced and no high solids/or ratios are required. Such high ratios are undesirable because they result in the entrainment of large amounts of product vapors into the solids workup system which may include a combustion zone used for reheating the solids. Also, with low solids to oil ratios it is possible to quench the total reactor effluent, including solids without requiring excessive heat removal for quenching.

Product coke is the preferred heat-carrying solid, particularly because of the high heating value of the solid product formed. However, other solids, such as sand, pumice, cracking catalyst, clay kieselguhr, or metal shot, may be used, if desired. These solids are heated preferably by circulating the same through a separate combustion zone and burning part of their carbon content therein. The combustion zone may be operated as a fluid or transfer line reactor or in any other manner well known in the art.

Specific reaction conditions, of course, depend on the character of the reactants involved and the results desired. Quite generally it may be stated that the dense fluidsolids feed mixture should be introduced into the transfer line contacting zone of the invention at velocities of about 5-40 feet per second, while the outlet velocity should be 40-100 feet per second, preferably about 60-80 feet per second to accomplish the desired separation effect.

When applying the invention to the upgrading of residual oils by contact with highly heated coke, solids particle sizes of about 32-325 mesh may be used at the velocities specified. Contacting temperatures of about lO00-l200 F. are suitable for the production of optimum yields of gas oil suitable as catalytic cracking feed stock, while for the preparation of chemicals, such as unsaturated and aromatic hydrocarbons, temperatures of about 1200-l500 F. are more suitable.

Having set forth its objects and general nature, the invention will be best understood from the following more detailed description of the embodiments illustrated in the drawing.

Referring now to Figure 1, the reference character 1 designates a transfer line reactor provided with spiral baffles 3 arranged over the major portion of the length of reactor 1 and prescribing a tortuous path upwardly through the vertical transfer line reactor. The lower end of reactor 1 is connected to a feed pipe 5 for supplying a suspension of subdivided solids in a carrier gas or vapor. Hydrocarbon feed together with a vapor diluent, such as steam, is introduced into the lower portion of reactor 1. A small section of the feed end of reactor 1 is free of baffies to provide sufficient space and time for intimate mixing of fluids and solids. Reactor 1 discharges into a conventional gas-solids separator 9 of the cyclone type.

When employing equipment of the type illustrated in Figure 1 to the thermal cracking or coking of heavy residual oils, finely divided hot coke having a particle size of 35-325 mesh, preferably predominantly about -200 microns, may be supplied in the form of a dense suspension of solids in a carrier gas through line 5. The temperature of the coke may be about 1100-l700 F., depending on the temperature desired for the cracking reaction in reactor 1. As a general rule, the coke feed temperature should be about 100-400 F. higher than the cracking temperature. Specific temperature differentials depend on the type of operation. They may be about l50-250 F. in the production of chemicals, such as olefins and aromatics and about 300-400 F. for making gas oil at 1100 F.

The coke may be preheated in any conventional manmet by partial burning in a fluid-type, transfer line or other suitable combustion zone (not shown). The hot coke may be fed to pipe 5 by means of an aerated standpipe, screw conveyor, star feeder, etc. For example, the solids may be placed under pressure in an aerated standpipe and introduced to the reaction zone after passing through suitable flow control means, such as a U-bend comprising a substantial riser section, say feet, after which a small amount of riser. gas is injected to control the flow rate. The carrier gas may be steam, flue gas, product tail gas or other inert gas. About 5-20 pounds of coke having a temperature about 100-400 F. higher than the desired reaction temperature may be supplied per pound of residual oil to be converted, depending on the products desired. Within the ranges specified, relatively low coke rates and temperatures are suitable for gas oil production and relatively high values for the production of chemicals. The feed rate of the solids-in-gas suspension should be so controlled that a linear superficial velocity of gases and vapors in reactor 1 of at least feet per second and preferably about 40-80 feet per second is established.

The residual oil which may be a vacuum pitch or any other heavy residue preheated to about 700-800 F. is injected partially in the liquid state through line 7, preferably by means of a spraying or atomizing nozzle 11 into the lowermost unobstructed section A of reactor 1. Nozzle 11 may be so arranged relative to feed pipe 5 that an injector effect is established by the high velocity suspension entering through pipe 5 and that immediate and intimate mixing of the solids and oil feed is accomplished in space A within a residence time in space A of, say, about 5 to /2 second, which should be short enough to prevent appreciable cracking in space A.

The intimate mixture of coke, liquid oil and vapors passes at a reaction temperature of about 1050-1400 F. and a velocity of about 40-60 feet per second into the baffied main portion of reactor 1 and cracking proceeds. The helical baffles 3 impose a spiral flow pattern on the upfiowing mixture. At the prevailing high velocity, an appreciable centrifugal effect is created which results in a concentration of the solids in the peripheral portion of reactor 1, the gasiform medium decreasing in entrained solids content toward the axis of reactor 1. For this purpose, the pitch of spinal baffles 3 should be such that there are about 05-10 complete turns over a height equal to the diameter of reactor 1. Cracked vapors are separated from the bulk of the heat-carrying coke immediately upon their formation and tend to concentrate in the largely solids-free axial portion of the reactor.

Since the density of the upflowing suspension increases rapidly toward the periphery of reactor 1 and most of the gasiform carrier medium flows up the central portion of the reactor, extremely high solids slippage against the flow of the carier medium takes place with the efiect that the average residence time of the solids in reactor 1 is about 2-10 times that of the gasiform medium. The solids carry the entire unvaporized feed so that the residence time of the refractory feed portions is extended by the same ratio and cracking may be carried to completion. without overcracking of product vapors.

For example When the production of optimum yields. of gas oil suitable as catalytic cracking feed stock is desired, reactor 1 may be advantageously so designed and. operated that an average total gas and vapor residencetime of about 0.5 to 3 seconds and an average solids residence time of about 1.0 to seconds are established, at: an average temperature of about 10501100 F. For the production of chemicals, solids residence times of 0.55.0 seconds and gas and vapor residence times of 0.1-1.0 seconds are suitable at temperatures of about: l300-1400 F.

' 20-30 lbs. per cu. ft.

A suspension of substantially dry coke in gasiform products and carrier medium, having an apparent density of about 0.3-3.0 is passed overhead from reactor 1 into cyclone separator 9. Product vapors and carrier medium are Withdrawn via line 10 to be passed to conventional recovery equipment or, if desired, directly to a catalytic cracking zone. Product coke is recovered through line 12. Any desired portion thereof may be passed after suitable stripping to a combustion zone (not shown) for reheating and returned to reactor 1.

Referring now to Figure 2, the equipment illustrated therein is similar to that shown in Figure 1 with the exception of the type of baffies used. Like reference characters are used to identify like elements. In place of helical baflies 3, reactor 1 of Figure 2 is provided with a series of perforated bafiie plates 13 having dams 14, distributed in staggered fashion over the length of reactor 1.

Reactor 1 of Figure 2 may be operated for residue coking substantially in the manner described with reference to Figure 1. The initial superficial gas velocity in zone A is preferably about 30-60 ft. per second so as to establish a gas velocity of about 60-80 ft. per second in the bathed reactor portion at points below and between baflie plates 13. Solids impinging on baffies 13 are reflected back into lower portions of the reactor while the gasiform medium passes through the reactor in continuous upward flow having a zig-zag pattern which, at the high velocities involved, results in a rough gas-solids separation and an accumulation of solids above perforated baffie plates 13.

The desired gas-solids separation may be secured and the solids accumulating on baffle plates 13 may be maintained in a mobile state by properly designing the reactor so that the pressure drop through baffle plates 13 and masses M thereon equals the pressure drop of the gases 1 and vapors flowing around bafiie plates 13. The former pressure drop is determined by the size and spacing of lbaffle plates 13, the depth of solids masses M, the width of the plate perforations, and the solids concentration in the gas and vapors in the plate perforations. The latter pressure drop is mainly a function of the flow velocity and the solids concentration of the gases and vapors fiowing around plates 13.

In general, it is desirable to maintain above plates 13 fluidized solids beds having an apparent density of about This may be accomplished by so controlling the pressure drop in the various portions of reactor 1 that the gases and vapors pass through fluidized solids above plates 13 at a superficial velocity of about 1-5 :ft. per second, preferably about 2-4 ft. per second, assuming a gas and vapor velocity around plates 13 of about -80 ft. per second. In some cases it may be necessary to obstruct the free flow of gases and vapors around plates 13 by minor mechanical flow impediments 16 in the form of small discs or the like so as to increase the pressure drop through these sections.

When so operating, the average residence time of the solids and the liquid deposited thereon is substantially longer, say about 25 times longer than that of the gases and vapors. Complete cracking of even the most refractory feed constitutents may, therefore, be accomplished, at vapor residence times insuificient to permit excessive overcracking.

By way of example, the following conditions may be employed to provide an average solids residence time about 5 times that of vapors and gases. Assuming reactor 1 to have an inner diameter of about 3 ft. and a height of about 20 ft., baffle plates 13 may be about 1.5 ft. wide. The height of dams 14 which controls the depth of the fluidized solids beds M on plates 13 may be about 1 ft. The distance between the top of dams 14 and the bottom of the next higher plate 13 should be about 1.2 ft. The plate perforations should provide a free area of about 520% of the total plate surface, the free area being the larger Within the range specified, the higher the density of the suspension passing through the perforations.

The superficial velocity of gases and vapors in space A may be about 40 ft. per second and about 80 ft. per second around plates 13. The superficial gas velocity in beds M should be about 3 ft. per second to establish an apparent bed density in beds M of about 30 lbs. per cu ft. These conditions are based on the use of petroleum coke of about 100-200 microns average particle size as the heat carrying solid. When operating as just described, no special flow impediments 16 are required to establish the desired pressure drop.

The system illustrated in Figure 3 is designed for multistage contacting of fluids with solids in equipment similar in many respects to that shown in Figure 1, like elements being identified by like reference characters. It will be noted that reactor 1 is provided with a plurality of centrally located vapor traps 15 distributed in spaced relationship over the height of the reactor, whereby a plurality of superimposed essentially unobstructed mixing zones A, B, C and a plurality of superimposed contacting zones X, Y, Z, with helical baffles 3 are established.

in operation, hot solids, such as subdivided coke and preheated residual oil, may be supplied via lines 5 and 7 and nozzle 11 substantially as described with reference to Figure 1. Rapid mixing takes place in zone A and the mixture enters zone X at high velocity. A rough separation of solids and vapors takes place in zone X while cracking is proceeding. Solids are concentrating and flowing up in the periphery of zone X. A relatively dilute suspension of solids-in-gases and vapors passes upwardly in the center of zone X, all substantially as described with reference to Figure 1.

When the solids and gasiform medium reach the level of the lowest trap 15, most of the central gas stream is diverted by trap 15 into line 17 which discharges into an exterior gas-solids separator 19. The solids concentrated in the periphery of zone X by-pass trap 15 through the annular space surrounding the trap and rapidly enter the next contacting stage Y. The vapors and gases freed of entrained solids in separator 19 may be recovered via line 21, preferably after quenching to non-reactive temperatures by the addition of a suitable quenching liquid through line 23. Solids separated in separator 19 may be returned to zone X via line 25.

This procedure is repeated in zone Y. Gas and vapors including those formed by further cracking are trapped out by the second trap 15, passed via line 27 to separator 29 and recovered through line 31 after quenching by means of liquid supplied via line 33. Solids may be returned to zone Y via line 35.

Solids passing upwardly through the annular space surrounding the second trap 15 may be further treated in zone Z and any desired additional number of similar zones as described with reference to zones X and Y. The final mixture of gases, product vapors and dry coke is passed overhead from reactor 1 to cyclone 9 to be further treated substantially as described with reference to Figures 1 and 2.

It will be appreciated that the solids suspension passing upwardly around gas traps 15 has assumed a relatively high density due to the loss of carrier medium removed through traps 15. However, this suspension still contains some valuable cracked product which should be removed as quickly as possible. In order to maintain proper solids flow at a desirably high velocity and to accomplish quick removal of occluded product vapors, it is desirable to add make-up carrier medium between the various contacting zones.

This may be accomplished most advantageously by splitting up the total residual oil feed into several portions and supplying the different portions to zones B, C, etc., via lines 3'7, 39, etc. In this manner, the additional carrier gas required for proper operation is supplied in the form of .feed and product vapors without undesirable dilution of the product with diluent gases. .In order to obtain proper mixing in these secondary mixing zones B, C, etc., an injector effect may be created in any suitable manner. For example, the cross-section of the reactor may be narrowed at a level just above traps 15 so as to form a vcnturi-type flow restriction below the mixing zone proper, as it is shown in connection with mixing zones B and C.

Split oil feed in the manner just described will tend to lower the temperature from zone to zone because the maximum temperature to which the feed may be preheated without excessive cracking lies substantially below desirable coking temperatures. However, such a staggered temperature pattern may be desirable in certain cases. For example, it may be desirable to treat refractory stocks, such as clarified oil fractions or recycle stocks, in the first stage Where temperature is highest. Virgin feed would be injected into subsequent stages it the same conversion is desired.

Furthermore diiferent products may be made in each stage, to wit: chemicals in the first stage at highest temperature, high octane gasoline in the second stage, and gas oil or catalytic cracking feed in a final stage.

If an appreciable temperature drop along the path of the solids through reactor 1 is to be avoided or a rise in temperature is desirable, hot solids may be supplied via lines 41, 43, etc., to zones B, C, etc., whenever additional oil is supplied to these zones. Operation involving split oil feed with or without additional supply of hot solids also tends to reduce solids stickiness and resulting solids agglomeration for a given over-all solidsto-oil ratio as previously indicated.

The embodiments of the invention described with reference to the drawing permit of various modifications. For example, the bafiie plates of Figure 2 may be upwardly inclined rather than horizontal in which case dams 16 may be dispensed with. Multistage operation with product recovery between stages may be employed in systems of the type of Figure 2 in a manner analogous to that described with reference to Figure 3. If solids reflux between immediately adjacent plates is desired in a system of the type illustrated in Figure 2, this may be accomplished by suitably increasing the size of the plate perforations or by decreasing the pressure drop around plates 13.

The total transfer line effluent may be quenched in certain cases, such as Figure 3 Where the coke to oil ratio may be quite low. This may eliminate cyclone 9. Also, the transfer line eflluent may be cooled about l00-200 F. by injection into a fluidized solids bed as for example a fluidized coke bed maintained at such lower temperature wherein coking of any unvaporized feed may be completed at temperatures not harmful to the vapors and gases produced. The total effluent from a system of the type shown in Figure 3 may go directly to a small drier vessel. at reactor temperature because the reaction is practically complete at the outlet of a staged reactor.

The invention will be further illustrated by the following specific example.

Example A system of the type illustrated in Figure 3 may be operated as follows for the production of chemicals, such as aromatics and olefins from crude residua:

Transfer line reactor 1 may be about ft. long and about 5 ft. wide. Five spiral bafile stages X, Y, Z, etc., each about 7 ft. high may be provided. The spacing of the spiral bafiies 3 may be about 2 ft., corresponding to about 3.5 complete turns in each 7 ft. stage.

A total of about 25,000 barrels per stream day of a reduced crude, such as a vacuum pitch having an AP] gravity of about 7l2, about l020 Conradson carbon andan initial boiling point of about 900 F. are supplied in 5 equal portions to reacter 1 via lines 7, 37, 39, etc., at a temperature of about 700 F. Simultaneously, steam amounting to about 2 wt. percent based on pitch maybe injected through line 7 to atomize the feed i nozzle 11.

Petroleum coke having an average particle size of about 100-200 microns is preheated to about 1500 F. and supplied through lines :L', 41, 43, etc. together with about 3 wt. percent of steam based on pitch for aeration and control of the flow rate of the solids. The coke feed rate should be so controlled that a coke/total pitch weight ratio of about 12 is maintained in reactor 1. A coke feed rate of about 7.5 tons per minute to each stage is suitable for this purpose. A reaction temperature of about 1300 F. and a maximum superficial vapor and gas velocity of about 60 ft. per second are established in this manner. The pressure may be maintained at about 10 lbs. per sq. in. gage.

The average density of the suspensions existing in the various stages just ahead of traps 15 may be about as follows:

Density, pounds Stage No. per cubic foot -1 0.80 2 1.50 3 2.25 4 3.0 5 3.75

When operating as described above, the average solids residence time is about 5-10 times the average gas resideuce time in the reactor. In the case of a conventional transfer line reactor without baffies providing for the same gas residence time, the ratio of solids residence time to gas residence time is usually less than 2.

While reference has been made heretofore chiefly to the upgrading of heavy residual hydrocarbon oils and this is the preferred embodiment of the invention, it should be understood that the invention may be applied in a generally analogous manner to other solids-fluids contacting processes, such as hydroforming, gas oil cracking (with or without catalyst), shale retorting, etc.

The above description and exemplary operations have served to illustrate specific embodiments of the invention. Other modifications within the scope of the invention may appear to those skilled in the art.

What is claimed is:

l. The process of cracking heavy hydrocarbon'aceous residues which comprises intiimately mixing said residues with hot subdivided coarse coke solids having a particle size of 35 to 325 mesh to form a mixture having cracking temperature, passing said mixture at a velocity of about 5 to 40 feet per second at said temperature upwardly through a narrowly confined extended spiral path for a time of about 1 second sufficient to cause substantial cracking of said residues and at a high velocity adequate to cause substantial separation of solids from gasiform cracking products on said path as the result of the centrifugal force developed in the spiral turns of said path and to concentrate solids in peripheral sections of said path, and passing a relatively dilute suspension of solids in gasiform cracking products through the axial portion of said path, the average residence time on said path of said concentrated solids being 2 to 10 times that of said dilute suspension which leaves said path at a velocity of about 40 to feet per second.

2. The process of claim 1 in which said spiral path is defined by spiral flow obstructions within a narrowly confined extended substantially straight path.

3. The process of claim 1 in which the length of said path is a high multiple of its diameter.

4. The process of cracking heavy hydrocarbonaceous residues which comprises mixing said residues with hot subdivided coarse coke solids having a particle size of 35 to 325 mesh to form a mixture having cracking temperature, passing said mixture at a velocity of about 5 to 40 feet per second at said cracking temperature upwardly through a narrowly confined extended path for a time of about 1 second, sufficient to cause substantial cracking of said residue, obstructing the fiow of said mixture on said path in a plurality of sections by flow obstructions defining a tortuous course for said mixture, said stages being separated by unobstructed sections, maintaining the flow velocity of said mixture on said path sufliciently high to cause substantial separation of solids from gasiform cracking products Within said stages as the result of rapid changes in the direction of flow of said mixture through said path, concentrating solids so separated in peripheral sections of said path, passing a relatively dilute suspension of solids in gasiform cracking products through the central portion of said path, withdrawing a portion of said suspension from a central portion of at least one of said unobstructed spaces, and withdrawing the remainder of said suspension from the top of said path, the average residence time on said path of said concentrated solids being 5 to 10 times that of said dilute suspension which leaves said path at a velocity of about 40 to 100 feet per second.

5. The process :of claim 4 in which said tortuous course is spiral.

6. The process of claim 4 in which said tortuous course is zigzag.

7. The process of claim 4 in which fresh hydrocarbonaceous residue is directly supplied to at least one of said unobstructed spaces.

8. The process of claim 4 in which the fresh hot solids are directly supplied to at least one of said unobstructed spaces.

9. The process of claim 4 in which different temperatures are maintained in different stages.

References Cited in the file of this patent UNITED STATES PATENTS 2,270,903 Rudbach Jan. 27, 1942 2,370,816 Schonberg Mar. 6, 1945 2,430,443 Becker Nov. 11, 1947 2,440,620 Tatf Apr. 27, 1948 2,444,128 Anderson June 29, 1948 2,444,990 Hemminger July 13, 1948 2,541,186 Anderson Feb. 13, 1951

Claims (1)

1. 4. THE PROCESS OF CRACKING HEAVY HYDROCARBONACEOUS RESIDUES WHICH COMPRISES MIXING SAID RESIDUES WITH HOT SUBDIVIDED COARSE COKE SOLIDS HAVING A PARTICLE SIZE OF 35 TO 325 MESH TO FORM A MIXTURE HAVING CRACKING TEMPERATURE, PASSING SAID MIXTURE AT A VELOCITY OF ABOUT 5 TO 40 FEET PER SECOND AT SAID CRACKING TEMPERATURE UPWARDLY THROUGH A NARROWLY CONFINED EXTENDED PATH FOR A TIME OF ABOUT 1 SECOND, SUFFICIENT TO CAUSE SUBSTANTIAL CRACKING OF SAID RESIDUE, OBSTRUCTING THE FLOW OF SAID MIXTURE ON SAID PATH IN A PLURALITY OF SECTIONS BY FLOW OBSTRUCTIONS DEFINING A TORTUOUS COURSE FOR SAID MIXTURE, SAID STAGES BEING SEPARATED BY UNOBSTRUCTED SECTIONS MAINTAINING THE FLOW VELOCITY OF SAID MIXTURE ON SAID PATH SUFFICIENTLY HIGH TO CAUSE SUBSTANTIAL SEPARATION OF SOLIDS FROM GASIFORM CRACKING PRODUCTS WITHIN SAID STAGES AS THE RESULT OF RAPID CHANGES IN THE DIRECTION OF FLOW OF SAID MIXTURE THROUGH SAID PATH, CONCENTRATING SOLIDS SO SEPARATED IN PERIPHERAL SECTIONS OF SAID PATH, PASSING A RELATIVELY DILUTE SUSPENSION OF SOLIDS IN GASIFORM CRACKING PRODUCTS THROUGH THE CENTRAL PORTION OF SAID PATH, WITHDRAWING A PORTION OF SAID SUSPENSION FROM A CENTRAL PORTION OF AT LEAST ONE OF SAID UNOBSTRUCTED SPACES, AND WITHDRAWING THE REMAINDER OF SAID SUSPENSION FROM THE TOP OF SAID PATH, THE AVERAGE RESIDENCE TIME ON SAID PATH OF SAID CONCENTRATED SOLIDS BEING 5 TO 10 TIMES THAT OF SAID DILUTE SUSPENSION WHICH LEAVES SAID PATH AT A VELOCITY OF ABOUT 40 TO 100 FEET PER SECOND.

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