US2503188A - Apparatus for thermal cracking of hydrocarbons - Google Patents

Description

April 4, 1950 E. v. BERGSTROM 2,503,188

APPARATUS FoR THERMAL cRAcKING oF HYDRocARBoNs Filed March 27, 1946 3 Sheets-Sheet 1 HEHTE PURA/HCE INVENTOR .EF/C l/. @EFG STOM BYMW ATTORNEY April 4, 1950 E. v. BERGsTRoM APPARATUS FoR THERMAL cRAcxING oF HYDRocARBoNs Filed March 27, 1946 3 Sheets-Sheet 2 WY f/.m Mm

April 4, 1950 E; v. BERGSTROM APPARATUS FOR THERMAL CRACKING 0F' HYDROCARBONS Filed March 27, 194e 3 Sheets-Sheet 3 ATTORNE Patented Apr. 4, 1950 A APPARATUS FOR THERMAL CRACKING F HYDROCARBON S Eric V. Bergstrom, Short Hills, N. J., assignor to Socony-Vacuum Oil Company, Incorporated, a corporation of New York Application March 27, 1946, Serial No. 657,591

7 Claims.

sired tov contact a gas with a solid for a predetermined denite interval of time.

In general, processes for contactof a gas with a granular solid provide means for introducing a gas to a body of the solid under such conditionsthat the gas will diiuse through the granules and thereby remain in contact with the same for the desired period. The utility of the present Iinvention is aptly illustrated by contact oi a hot granular solid with hydrocarbons to induce rapid heating vof the gas to a desired cracking temperature. For example, lower olens such as ethylene are produced in large yield by cracking hydrocarbons such as crude oil or gas oil at temperatures of 1500 to 1600 F. for very short reaction periods, say one-half second or less. If the crackingtemperature is unduly prolonged, aromatic compounds are produced to a substantial extent at the expense of the low boiling oleilns. Longer cracking times also produce highly condensed hydrocarbons of a tarry or coky nature. These factors render it undesirable to conduct the cracking `reaction in heating coils of the-type` generally used lor thermal cracking to produce gasoline. The reaction can, however, be

' readily conducted by contacting the charge with a highly heated refractory solid which raises the temperature of the char-ge very rapidly to the desired cracking temperature. After the desired cracking time, the temperature is advantageously and rapidlyl reduced by quenching; either by injection of a quenching liquid such as wateror liquid oil or by contact with a cold granular solid.

The apparatus of this invention is also well adapted tothe manufacture ofacetylene and the like by cracking of hydrocarbons at high temperature. Thus. light hydrocarbon gases, typied by propane, may be contacted with a solid at such temperaturethat the gases .will be rapidly heated to 2400 F. and thereafter rapidly reduced to a temperature below that which will cause formation o( undesirable by-products.

that the path followed by the charge in diiusing through the ygranular -solids shall be constant for all portions of the charge. This ideal is of course impossible of achievement in actual practice but the present invention provides means for very close approximation of this desired result and it is now possible to obtain closely controlled reaction times in apparatus capable of adjustment to provide different contact times and thereby compensate for the requirements of diierent reactions or `diflerent charging stocks. y

According to the present invention, the apparatus is so designed that a highly heated refractory solid is passed continuously into and through a reactor for ,contact with a charge to thereby heat the latter to the'desired reaction temperature and maintain the charge at such desired temperature for a predetermined period of time. The apparatus is also adapted for use in a process wherein the charge is supplied in liquid phase to be vaporized and heated by the contact with the granular solid contact material.

'I'he ow of contact material to the contact bed within the reactor is such as to provide a sloping surface across the top of the bed lying at about the angle of repose of the solids used. The charge is introduced by a plurality of outlets in the bed and lying in a. plane substantially parallel to the top surface of the contact material. By this means it is possible to provide a plurality of paths of equal length through the bed from the outlets to the top surface. There will of course be minor variation in the length of path travelled by portions of the charge from the same point of introduction but the mean path from each outlet is substantially equal to the mean path for each other outlet.

It is accordingly a principal object of this invention to provide means for thermally cracking hydrocarbons by contact with a hot granular solid wherein variations of contact time are reduced to a minimum.

A further object of the invention contemplates adjustability of the contact time by providing movable pipes for the introduction of charge which can be adjusted as to the distance between the top of the bed and the point of charge introduction.

These and other objects and advantages of the invention will become apparent from consideration of a typical plant for practicing the invention as illustrated by the annexed drawings wherein:

Figure 1 is a diagrammatic representation of the principal 'elements of a plant for practicing the thermal cracking of hydrocarbons to produce olens;

Figure 2 is a vertical half section of a heater for bringing granular refractory solids to the temperature desired for the reaction;

Figure 3 is a partial section on line 3-3 of Figure 2;

Figure 4 is a detail view of a modified type of burner tube for use in the apparatus of Figure 2;

Figure 5 is a'partial vertical section of the reactor to which this invention is directed;

Figure 6 is a partial section on line 6--6 of Figure 5; and 4 Figure 7 is a partial section on line 1-1 of Figure 5.

Referring specifically to Figure 1, a refractory granular solid such as fused aluminum oxide having an average diameter of 0.3 inch is circulated in a cyclic manner through a heater I0, a reactor Il andan elevator I2. In the heater I0 the granular solid is raised to a suitable temperature by the combustion of fuel introduced at I3 in air from blower I4, flue gases being diverted to an economizer or direct to the stack at I5. The highly heated solids pass downward through a feed leg I6 having a steam sealing zone Il to the reactor Il. A preheated or cold oil charge which may contain water (in either liquid or vapor phase) as described in more detail hereinafter is introduced from a manifold I8 and brought into direct contact with the heated solids in the reactor. The gases rising from contact with the bed of granular solid is quenched with water introduced at I9 and the cooled effluent stream is removed at and passed to a tar separator 2| wherein high boiling materials are removed. 'Ihe remaining vapor passes from the tar separator by line 22 to a spray condenser 23 wherein oil or water spray further condenses a portion of the efliuent stream to leave a vapor containing a high proportion of the desired product which passes overhead by line 24 to suitable purification equipment such as a gas plant. The bottoms from spray condenser 23 are transferred to an oil separator 24 from which is removed a hydrocarbon layer which may be cooled in heat exchanger 25 and a Water layer which is passed through cooler 26 and may then be returned to the reactor for quenching or to be mixed with the charge stream. The liquid hydrocarbon layer from oil separator 24 may be further purified to recover gasoline, aromatic naphthas or relatively pure aromatic compounds.

Returning again to the reactor II, the cooled refractory granules pass down through the reactor tobe removed at 21 for recycling to the heater: It is often desirable to seal the bottom of the reactor against escape of hydrocarbons as by introduction of steam at line 28 to the bottom of the reactor. The granules pass through an evacuation pot 29 connected to a water injector 30 andare then transferred to the bottom of the elevator I2 wherein they are raised to the top and returned to the heater through a classifier 3| wherein particles of a size smaller than that desired in the system are removed from the stream and rejected 'from the system.

The structure of the heater is shown in Figures 2 to 4 wherein the shell 32 encloses means for burning fuel in air in direct contact with the refractory solid and then passing the products of combustion through the refractory solid in generally countercurrent relation about the means for introducing air and fuel, thus preheating the solids as well as the air and fuel supplied to the burners.

Granular solids are continually introduced at the top of the heater IIJ to fall on a tube sheet 33 having a plurality of depending feed pipes 34 which provide a substantially uniform supply of solids across the heater above the heating zone. Solids from the feed pipes 34 pass downwardly through preheating pipes 35 to enter a zone of direct contact with products of combustion below the ends of the tubes 35. Air and fuel for heating the solid are introduced by air headers 36 and fuel headers 31 respectively. Depending from the air headers 36 are a plurality of air tubes 38, each enclosing a fuel tube 39 connected to a fuel header 31. As the air and fuel pass downward through their respective supply tubes, they are heated and are then combined at the bottom of the supply tubes to provide a very hot flame impinging directly on the hot granular solids. As will be apparent, there is an open space, free of solids, directly below the end of each air tube 38, the form of which depends on the angle of repose of the granular solid. This forms a small combustion chamber, but for the most part, the flame is propagated through and combustion occurs on the surface of the granular solids thus giving very eicient heating. The products of combustion flow upward through the mass of solids in counter-current direction thereto until they reach the bottom of preheating pipes 35 and enter a chamber free of solids about the preheating tubes 35 and the air tubes 38. The apparatus arrangement for supply of air and fuel into the heating chamber as described hereinabove is the subject of claims in United States Patent 2,432,503, issued December 16, 1947, in which this applicant is one of the inventors.

'I'he highly heated solids are withdrawn from the heater at a uniform rate across the heater by the use of flow controlling plates shown in the bottom of Figure 2. The upper plate 40 has a number of depending feed pipes 4I each of which draws uniformly from a small area above its open upper end. The solids from the pipes 4I are withdrawn from a space between plate 40 and a plate 42 therebelow by a lesser number of openings in the plate 42. Similarly, a still lower plate 44 has a number of openings still less than the number of openings in plate 45.

The general arrangement of tubes in the heating and combustion portion of heater I0 is illustrated in Figure 3 wherein it is shown how the tubes for supplying air and fuel are uniformly dispersed among the tubes for supplying hot granular solids. Figure 4 is a detailed view which shows a modified type of tube for supplying air and fuel. The air tube 38 is of the same general nature as those shown in Figure 2 but the fuel is introduced at a plurality of spaced points near the bottom of the burning section by means of perforated pipes 46 extending out from the fuel tube 39 as shown. Preferably, a triangular n -41 is provided above each of the perforated tubes 48 as shown.

Figures 5to 7 inclusive relate to the reactor structure which is characterized by means to so introduce the hot refractory granules that they Will have an upper surface of relatively simple configuration thus rendering easier the problem of controlling reaction time. The outer shell 58 of reactor II, having internal insulation 5I, is of generally circular outline. The actual reactor space, however, is defined by an inner shell 52 of generally rectangular cross-section. The hot -of the moving bed extendingas a plane sloping at the angle of repose from the bottom edge of hood 54 to the opposite side of shell 52.

It will be apparent that the vrectangular shape of the reactor here shown is not the' only form -suitable for this element. Other shapes, using 'dividing inserts of suitable structure may also be employed. For best operation, the 'dividing 'insert should be of a thickness at least about equal to the thickness of the feed pipe to thereby divert the moving solids to portions of the reactor other than that directly below the feed pipe.

gli! tars, the remaining vapor is quenched to 100 Among the products produced are 8,752 lbs. per hour of ethylene representing a yield of 28.1% by weight of this principal product. 'I'he process also produces 1500 lbs. per hour of highly aromatic gasoline having a clear octane number of 90 or better. Substantial yields of propylene and butadiene are also obtained.

It will be noted that the reaction zone is such that the process is not adversely affected by accumulation of coky or tarry deposits or by deposition of solid matter itself from impurities in the charging stock. Similarly, dirty water may be used since all solid deposits from the reaction are laid down on solid particles which are thereafter transferred to a combustion zone wherein solid contaminants are rapidly and eiliciently removed by burning.

The compact moving bed of solids withinshell carbons from leading out of the shell 52 and condensing between outer shell 50 and internal insulation 5l This is advantageously accomplished by introducing a non-condensible gas. at 59. The

gas introduced at 59 may be the light hydrocarbon gases available around oil refineries or may be the-light hydrocarbon gases removed from the product of the reaction.

The charge is introduced to the upper portion of the moving bed within inner shell 52 by the plurality of pipes 60 extending into the reactor through stuiling boxes 6I from headers 62. Normally, reactions of the present type proceed more satisfactorily in the presence of steam and the steam for the reaction may be provided by water which is vaporized in the reactor with the charge. 'I'he water may be emulsifled with the charge to the reactor or a mixture of water and oil charge from header 62 may be passed through a homogenizing valve before introduction to the reactor. The pipes 60 extend through a plate 63 which forms the top of the reaction zone and through strips 64 extending from the edge of hood 54 to the inner shell 52. The space between the strips 04 and the top plate 83 form a discharge collecting zone from which the treated vapors are withdrawn by pipe 65 to be conducted to separating and purifying apparatus as described above. The temperature of the eiiluent gases is advantageously reduced upon entry into discharge pipe 65 by spraying water therein from a pipe 66 entering the reactor through stufling box 61.

In a typical operation a mass of aluminum oxide refractory pellets of about 0.3" diameter is handled in the elevator at 900 F. at the rateof 200 tons per hour. In the heater the temperature of the pellets is raised from 900 F. to 1575 F. and the pellets enter the reactor at 1546 F. 31,150 lbs. per hour of oil at 900 F. and 15,700 lbs. per hour of water are introduced to the heated granular refractory. At a contact time of 0.29 second with a mean effective temperature of 1440 F. a product is produced which is quenched immediately with water to 572 F. After removal The apparatus is also adapted to production of acetylene at 2400 F. by cracking of propane or the like. It is found desirable in this case to introduce the hydrocarbon charge to a fairly low point in the reactor, say a short distance above the upper now control plate and introduce water or steam in a uniform mannerv near the top of the reactor. An improvement on the reactor and the divider insert is shown and claimed in application 665,604, liled March 27, 1946.

I claim: f v

1. In apparatus for contacting gas with a granulargsolld for a controlled time, a shell of rectangular cross section, said shell having a top and bottom, a dividing insert positioned vertically within said shell and terminating short of the top of said shell, said dividing insert extending entirely across said shell in one horizontal direction and extending across only a central portion of the shell in the horizontal dimension at right 'angles to said rst dimension, a feed tube for solid material supply extendingupwardly from a central location spaced above the top of said shell, a hood extending downwardly from said feed tube into said shell, and terminating on its lower end above said dividing insert, whereby the solids supplied from said feed tube are distributed along said dividing insert, said hood extending onits lower end substantially across said shell in the dimension parallel to the greatest horizontal dimension of said dividing insert and having a horizontal dimension at right angles thereto about equal to the horizontal dimension of said feed tube, and said hood on its upper end having substantially the same horizontal dimensions as said feedtube, and the top of said hood having a substantial slope in the direction of its widest dimension, a plurality of horizontally spaced gas injection tubes extending downwardly into said shell to points below the upper end of said dividing insert, said tubes being vertically adjustable, an outlet conduit for solid withdrawal connected to the bottom of said shell, baille inemfbers arranged above said outlet conduit tov procentrally positioned within said inner shell and extending through a major portion of the shell height but terminating short of its top and botwardly from said feed pipe through the topV of said inner shell vand terminating on its open lower end shortly above the dividing insert, the lower end of said hood being positioned centrally over said dividing insert and being of less horizontal dimension than the insert in the direction of its smallest horizontal dimension but extending substantially the full width of the insert in the direction of its greatest horizontal dimension and the roof of said hood forming a substantial angle with the horizontal in both directions, a plurality of vertical reactant supply tubes extending downwardly through the tops of said cylindrical and rectangular shells and terminating within said rectangular shell at .points on each side of and below the top of said dividing insert and above the lower end of said shell, the lower ends of said tubes terminating at progressively lower levels in said shell the greater their horizontal distance from said dividing insert, an outlet conduit for solid material discharge connected to the bottom of said inner shell and extending through the bottom of said cylindrical shell, vertically spaced partitions with uniformly distributed orices therein extending across the lower section of said inner shell, the partitions at successively lower levels having a progressively lower number of orices therein and the orifices in any partition being horizontally off-set from those in the partition thereabove and an outlet conduit for gas withdrawal connected into said inner shell near its upper end.

3. In apparatus for contacting fluid material with a granular solid for a controlled time, a shell of rectangular cross-section, said shell having a top and bottom, a dividing insert vertically and centrally positioned within said shell and extending through a major portion of the shell height but terminating short of its top and bottom, said insert extending in its major horizontal dimension substantially entirely across said inner shell but extending over only a central portion of said shell in the horizontal directionat right angles to said major dimension, a solid material feed pipe extending upwardly from a point centrally located above the top of said shell, a connecting hood extending downwardly from said feed :pipe through the top of said shell and terminating on its open lower end shortly above the dividing insert, the lower end of said hood being positioned centrally over said dividing insert and being of less horizontal dimension than the insert in the direction of its smallest horizontal dimension but extending substantially the full width of the insert in the direction of its greatest horizontal dimension and the roof of said hood forming a substantial angle with the horizontal in both directions, a plurality of vertical reactant supply tubes extending downwardly through the top of said shell and terminating within said rectangular shell at points on each Side of and below the top of said dividing insert and above the lower end of said shell, the lower ends of said tubes terminating at progressively lower levels in said shell the greater their horizontal distance from said dividing insert, an outlet conduit for solid material discharge connected to the bottom of said shell, vertically spaced partitions with uniformly distributed orifices therein extending across the lower section of said shell, the partitions at successively lower levels having a progressively lower number of orices therein and the orifices in 'any partition being horizontally off-set from those in the partition thereabove and an outlet conduit for gas withdrwal connected into said inner shell near its `upper end.

4. In apparatus for contacting vfluid material with a granular solid for a controlled time, a shell of rectangular cross-section, said shell having a top and bottom, a dividing insert vertically and centrally positioned within said' shell and extending through a major portion of the shell height but terminating short of its top and bottom, said insert extending in its major horizontal dimension substantially entirely across said inner shell but extending over only a central portion of said shell in the horizontal direction at right angles to said major dimension, a solid material feed -pipe extending upwardly from a point centrally located above the top of said shell, a connecting hood extending downwardly from said feed pipe through the top of said shell and terminating on its open lower end shortly above the dividing insert, the lower end of said hood being positioned centrally over said dividing insert and being of less horizontal dimension than the insert in the direction of its smallest horizontal dimension but extending substantially the full width of the insert in the direction of its greatest horizontal dimension and the roof of said hood forming' a substantial angle with the horizontal in both directions, a plurality of vertical reactant supply tubes extending slidably through the top of said shell and terminating at points on each side of and below the top of said dividing insert and above the lower end of said shell, the exact level of the lower ends of said tubes being adjustable by vertical movement of the tubes, an outlet conduit for solid material discharge connected to the bottom of said shell, and a conduit for gas discharge connected near the upper end of said shell.

5. In apparatus for contacting gas with a granular solid material for a predetermined period of time, a shell of rectangular cross-section having a top and bottom, a centrally disposed feed conduit extending through the top of said shell and terminating near the upper end thereof, a dividing insert positioned centrally across said shell directly below said feed conduit, said insert being of a thickness at least about equal to the thickness of said conduit but substantially less than the corresponding dimensionvof said shell, a plurality of spaced gas injection tubes extending downward into said shell and terminating therein at a plurality of points below the upper end of said insert and above the bottom of said shell, said points lying in planes which slope upwardly from the sides of said shell towards said divider.

a centrally disposed outlet conduit connected to the bottom of said shell, and gas outlet conduit connected near the top of said shell.

6. In apparatus for contacting gas with a granular solid for a predetermined period of time, a

.75 tioned within said shelldirectly below said feed conduit, said insert being of a minimum horizontal dimension which is at least equal to the minimum horizontal dimension oi said feed conduit and said insert oocupyin only a portion oi the shell cross section whereby solids from said feed conduit may be diverted into portions of said shell on either side of the insert. a plurality of gas injection tubes extending downward into said shell and terminating on their lower ends short of the bottom of said shell but below the upper end of said dividing insert. the lower ends of said tubes being uniformly spaced apart laterally and being located at progressively lower levels the greater the horizontal distance of the tubes from the insert, a centrally disposed outlet conduit connected to the bottom of said shell, and gas outlet conduit connected near the top of said shell. l

'7. In apparatus for contacting iluid material with a granular solid for a controlled time, a shell of rectangular cross-section, said shell having a top and bottom, a dividing insert vertically and centrally positioned within said shell and extending through a major portion of the shell height but terminating short of its top and bottom, said insert extending in its major horizontal dimension substantially entirely across said inner shell but extending over only a central portion o! said shell in the horizontal direction at right angles to said major dimension, a solid material'ieed 30 l0 pipe extending upwardly from a point centrally located above the top of said shell. a connecting hood extending downwardly from said feed pipe through the top oi' said shell and terminating on ,its open lower end shortly above the dividing insert, the lower end of said hood being positioned centrally over said dividing insert and being of less horizontal dimension than the insert in the direction of its smallest horizontal dimension but extending substantially the full width of the insert in the direction of its greatest horizontal dimension and the roof of said hood forming a substantial angle with the horizontal in both directions, a plurality ofvertical reactant supply tubes extending through the top of said shell and terminating at points on each side of and below the top of said dividing insert .and above the lower end of said shell, said points lying in two planes sloping downwardly and away from said insert towards the two opposite sides of said shell, a centrally positioned outlet conduit connected to the bottom of said shell for granular solids withdrawal. an outlet conduit for gas withdrawal connected to said shell near its upper end and sub stantially above the lower ends of said reactant supply tubes.

ERIC V. BERGSTROM.

No references cited.

Claims (1)

1. IN APPARATUS FOR CONTACTING GAS WITH A GRANULAR SOLID FOR A CONTROLLED T.ME, A SHELL OF RECTANGULAR CROSS SECTION, SAID SHELL HAVING A TOP AND BOTTOM, A DIVIDING INSERT POSITIONED VERTICALLY WITHIN SAID SHELL AND TERMINATING SHORT OF THE TOP OF SAID SHELL, SAID DIVIDING INSERT EXTENDING ENTIRELY ACROSS SAID SHELL IN ONE HORIZONTAL DIRECTION AND EXTENDING ACROSS ONLY A CENTRAL PORTION OF THE SHELL IN THE HORIZONTAL DIMENSION AT RIGHT ANGLES TO SAID FIRST DIMENSION, A FEED TUBE FOR SOLID MATERIAL SUPPLY EXTENDING UPWARDLY FROM A CENTRAL LOCATION SPACED ABOVE THE TOP OF SAID SHELL, A HOOD EXTENDING DOWNWARDLY FROM SAID FEED TUBE INTO SAID SHELL, AND TERMINATING ON ITS LOWER END ABOVE SAID DIVIDING INSERT, WHEREBY THE SOLIDS SUPPLIED FROM SAID FEED TUBE ARE DISTRIBUTED ALONG SAID DIVIDING INSERT, SAID HOOD EXTENDING ON ITS LOWER END SUBSTANTIALLY ACROSS SAID SHELL IN THE DIMENSION PARALLEL TO THE GREATEST HORIZONTAL DIMENSION OF SAID DIVIDING INSERT AND HAVING A HORIZONTAL DIMENSION AT RIGHT ANGLES THERETO ABOUT EQUAL TO THE HORIZONTAL DIMENSION OF SAID FEED TUBE, AND SAID HOOD ON ITS UPPER END HAVING SUBSTANTIALLY THE SAME HORIZONTAL DIMENSIONS AS SAID FEED TUBE, AND THE TOP OF SAID HOOD HAVING A SUBSTANTIAL SLOPE IN THE DIRECTION OF ITS

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