US2953517A - Fluid coking process - Google Patents

Description

p 1960 R. s. WHITELEY ETAL 2,953,517

FLUID coxms PROCESS Filed Nov. 12. 195:

COKER 27 PRODUCTS if 29 24 "2 :JI'

21 I '1 HOT soups 4 23 I O O N FIG. 5

so so so JET VELOCITY F'lZ/SEC.

Robert 5. Whiteley Inventors Donald D. Dun/op By )77, flw/Afforney United States Patent 1 2,953,517 .1 FLUID LCQKING PROQE -.Robert- S Whiteley andDonald D. Dunlop, Baton Rouge,

' 'La.;assignors to? Esso Research and Engineering Company; arac'orpbrationzofQDelawaf Filed ov. 12, ,11953, Ser.' No. 39 -1' 454 s Claims. 01403 -1127 afluidized bed 'offinelyfdiiiid'edsol id particles-which are substantially: inert 'catalytically. The process operates "quite" satisfactorily" in" general, but .ditficulties; are I frequently encountered .withraggl'omeration jot ,the' solid 1 particles into; relativelylarge;masses-which interferelwith 'fluidity' ormobilityjo'fi the bedfandffinally tend'to. cause I bogging; ofjg the b'ed and-iuterruptionl of the'icolring opera- 7 tion.

"'Ithas' been recognized that it is 'highly desirableto obtain as uniform adispersion of the, feed in .the fluidized solids bed i's possiblel .TheQfihely divided-. solid .parti "cles' used are commonly of ajsizeqangefrom .abo'utiO to 400 micronsfavefageldiameterl l'S ichparticles tend readily to adhere ,toeach.otherIwhen coated withthe relatively yiseous' residual o'ilsiwhich are. typical of coking feed stocks; If theiratio of oil, to,.,agiven .'mass.of. solids near ap'ointhinthemekinggbed where thelfeed is introdu'ced ,is too great; a, number .ofparticlesfl adhere I together because they do 1m ,hayefsuflicient heat content to. fully evaporate and crackT-th'e rr'esiduum'fe'e'd ,and .-reduce.-. the -residuegtoTdrycoke.

flt has; also-been i ecognized. in theart that it desirab le to fin'fr'oduce the I feed f at" a relatively large number of jseparate'jl'ioints'du th 'flllidized bedio improve distriibution. tEven'tliis is v t v fin the relatively dense fluid" beds employed, 'I'r'fanging usually between 30 .to;60 wpounds per 'c'ubictfoot. apparent density," "the "usual iatoinized' "feed 1 jets fcannot gpenetrate t completely -satis'factory'..because VeryQfaI'. .Par'ticle's1' offsolidjrhate'rials; siren as coke share of oil even when jthe'loil Zfis'l finely. atomized and i dispers'ed.

inassi It-has .been .found,..quite unexpectedlyfthat the 60 According to the presentinvention improveddispersion pr'ojeetion'o'f a. solidtstream-within ithis'loptimuin velocity range Fmarke'dly. reduced"agglomeration of the bed-{particl'es as coniparedwwithnhigher zor lower jet velocities.

EAbove about J5. feet permsecondgipower requirements ibegin ito become. excessive. ..Moreover this *system has "the importantadvantageof =avoiding-tthe introduction of :an: atomizing .fiuid..such..as. .steamy'which is'necessary with conventional.atomizingujets.

injecting oil .asasolid. stream the critical-jet velocity is: muchhmorec important :than' is the' case "with 'a'n atomized spray. .nozzle. i :It :--is fstlierefore highly irnportant to prevent restriction of the flow from the nozzle 2,953,517 Pa tented Sept. 20, 1960 [with consequent impairment of theoptimum jet velocity. HenceQ onet' feature of the. present invention i involves "the design of. the nozzle such that a conti'nuous or nonatomized" stream of 'oil' may be "projected at a definite 5 velocity without plugging. This is accomplished'by the .use oi a hot f fluid jjacketgaround the feed line substantially to the point'where it emerges from the nozzle.

'I'hus the pr'esentiinvention relates to a' method of coking with emphasis particularly upon the manner of introduction of reed when it relates to the particular design andarrangernent jof feed nozzles neededjtoaccomplished "such a feed method. The invention, will be rnore 'cle'arly' understoodby referring 'to the fattached drawing, wherein Fig. l is' a yerticalsectionalview of a vcoking system including afplurality'offfeed nozzles accordingto the invention, a 1

Fig; 2 is an enlarged detailed perspective view of a suitable nozzle tip. for 'usejin the' process,

Fig. 3 is a-transverse sectional View taken substantially "on the line 3+3 of-Fig. 2, looking in thefldirection of "the arrows,

"Fig; 4 is a'pe'rspective View of ,ats'ome'whatmodified ,0 ,1 l p,

Fig. 4a is an'end view of the nozzle of Fig. 4,

*Fig. 5' is af gnaph'showing the relation between jet velocity in aismooth solid stream and 'theagglomeration rate'ina typical fluidizedsolids coking system. employingc'oked' particles j as the heat carrying solids.

:Referring first'jtoEig I the coking vessel 11' isof conventionaldesignwith' provision suchfas an'inlet line 13"iforf introducing. lpr'eheated solid, particles, preferably 'eoke"particles," of a size "ranging somewhere between 120 'and;about400' microns average diameter. A',fluidi'zing gas"'s uehfas'fsteam'is introduced through one 'or more inletsylsrjand the bottom "ofthe vessel' is constructedf-to provide astripping zonej17 into whichra strippinggas such asisteam may be introduced .at '19.

Afeed manifold'zljbrings preheated, oil; to a plurality of feed nozzles Z3'which are preferably spacedmoreor *lessequally ina'yertical and lateral or arcuate-arrangementaroundjthe periphery of thevessel 11. Thesenozzles preferably project for ,somedistance into the vessel so as to 'avoidhaving the feed contact the vessel walls 45 directly.

' The hot solidpartic'les' which I form a, fluidized solids bed '24 are preferably jpreheated 'to'a temperature surficientto 'establish a fluidbedtemperaturefof at least 900 F aud notm 'orefthan about 1200 F. .for coking to -produce rn'otor' fuel's and gas oil frornpetroleum residua.

"Whereitfis desired"to fproduce chemical raw materials 1 such asolefinsandiaromaticsfthe bed temperature should be substantially higherand contact time is much shorter.

l he feed is vaporized and cracked by contact withlthe -hot particles andthe'vapo'rous or'g'aseous products pass "upwg lqlythrfough aisolids separator such as .acyclone ,25

"and to afsuitable recovery system notshown throug h outlet 2 7. The s'eparatedsolids are returned -to the bed througlr solids return line or dipleg .29.

Since the colgingfprocess is endothermicgthe coke partiales-gradually,are"cooled and are'withdraw from. the "-bottorn'of the Vessel, for example, through stripper -117 into an outletline 31. From here, 'at-least a part of the solids are taken to a' heater and reheated for return 65 through line 1 3 Inasmuch as coke is'produced in the -process,1part of itmaybewithdrawn as a product.

The tips ofth "nozzle members23' are shown considerably enlarged in Figures 2, Band 4. The form shown in*- Fig." 2. "gnerallyfiesignated 35, consists primarily of 0 a cylindrical 'bodywith a' tapered or wedge shapeden d portion 37 which is hollow substantially" throughout 'its length to provide for steam jacketing. An inner tubular the data appear to be sound and well substantiated. will be obvious that various modifications may be made feed line 39 extends through the tip and is preferably turned at right angles near its outlet end so as to project substantially vertically. within the coking vessel as indicated at 41. It is found that in order to prevent excessive atomization of the jet the terminal portion of the how should be straight and its length should a least The nozzle structureof Fig. 2 is H times its diameter. shown in cross-section in Fig. 3 where it will be noted that the feed line 39 and the'perpendicular extension 41 are sourrounded by the hollow jacket space so that a .jacketing medium may be kept flowing through the tip down the system.

The nozzle tip structure shown in Fig. 4 is somewhat similar to that of Fig. '2 but is not jacketed completely out to its outlet. It comprises a cylindrical body 45 having an extended end portion 47. The feed line indicated at '51 is essentially the same as feed line 39 of Fig. 2 but the end portion of the nozzle 45 is not hollow, being bored only to provide a smooth flow line 53 of the same diameter as the flow line 55 in feed line 51. It may be formed conveniently by drilling longitudinally and transversely, plugging the end of the longitudinal bore 53 with a plug 56. This simplifies construction and facilitates cleaning it line 53 should become clogged. A vertical bore 57 at least 5 times as long as its diameter joins the bore 53 so that a continuous or solid stream of oil may be fed therethrough. In cross-section, the nozzle tip may be generally elliptical with the major axis of the ellipse arranged vertically as shown in Fig. 4a. Alternatively, it may be merely flattened so as to be narrow in the vertical plane- The diameter of the bore is relatively small and the velocity should be maintained between the general limits of 35 and 75 feet per second. The unjacked portion of this nozzle is relatively short. The steam jacket, when used, is primarily for cooling, not for heating, under usual coking'conditions, to avoid coking of the feed within the nozzle.

The temperature of preheating of the oil feed is of some importance. It is desirable to reduce the viscosity of the feed as far as is reasonably possible without ap- .proaching the point where thermal cracking would take place within the nozzle by reason of the feed temperature. perature for the feed is about 500 to 600 F.

In Fig. 5 there is shown graphically the relation between jet velocity and agglomeration rate in grams. The data .were obtained mainly in a small scale apparatus.

The agglomerates were measured as material retained It has been found that the optimum preheat tem on a IZ-mesh screen. It was found that in a small apparatus a-velocity below 35 feet per second resulted in substantial agglomeration of the solids. Thus when coke was used as the heat carrying solid material it was found that as much as 0.44 to 2.75% by weight of the coke. was agglomerated to a size that would not pass the 12- mesh screen. At the other end of the scale it was found that increasing the velocity above .70 feet per second was satisfactory as regards operation but consumed excessive power.

are dispersed by the shearing action of the coke particles in the path of the jet. Too low avelocity does not result in suflicient shearing or suificient penetration in distance.

The data of Fig. 5 have been substantially confirmed by subsequent operation in a larger coking unit so that It in the process and in the design of jet nozzles as well as in the arrangement and number of jets. The number of It appears that jets of optimum velocity have suflicient energy to penetrate the fluid coke bed and feed points will be as many as is required; for example, the number will vary considerably with the size and shape of the coking vessel as will also the arrangement of the nozzles. Ordinarily it is preferred to project the feed vertically or substantially toward the vertical. How ever, as long as the feed does not impinge on the vessel walls, so as to cause formation of coke deposits, it may be projected slant-wise or even horizontally.

The nozzle may be and preferably is longitudinally adjustable, in many cases, so that it can be projected into the vessel to a variable extent as may be desirable. It is also desirable to arrange each nozzle so that it can readily be withdrawn for inspection and/ or replacement.

What is claimed is:

1. A process of coking heavy residual hydrocarbon oils in a dense turbulent fluidized bed of hot finely divided solid particles which comprises preheating the oil feed to a temperature approaching but below incipient thermal cracking to reduce its viscosity substantially to a minimum, then injecting the non-viscous liquid oil feed vertically in a plurality of substantially continuous solid stream oil jets without substantial atomization directly into said fluidized bed at vertically spaced points therein at a jet velocity above about 35 feet per second to minimize agglomerationof the finely divided solid particles, each solid stream oil jet passing through a terminal confined passageway. having its length at least five times that of the diameter thereof.

2. A process according to claim 1 wherein finely divided solids comprise coke particles in the size range between about 20 and 400 microns average diameter.

3. A process according to claim 1 wherein said finely divided solids in. said fluidized bed are at a temperature above 900 F.

4. A process according to claim 1 wherein the jet velocity of said continuous solid stream oil jets is between about 35 and feet per second.

5. A process for coking heavy residual oils in the presence of finely divided solids which comprises forming a dense turbulent fluidized bed of hot solid particles in a coking zone, then injecting residual oil preheated to a temperature of at least about 500 F. and approaching but below incipient thermal cracking temperature to reduce the oil viscosity directly into said dense fluidized turbulent bed at a plurality of regions spaced one above the other Within said dense turbulent fluidized bed as a plurality of Vertically spaced substantially continuous solid stream oil jets without substantial atomization at a jet velocity between about 35 and 75 feet per second to supply suflicient energy to said solid oil streams to penetrate said dense fluidized bed of solid particles and to be dispersed by the shearing actionof said solid particles of said fluidized bed in the pathrof said solid oil streams to distribute the oil feed on said finely divided solids and to minimize agglomeration of said finely divided solids, each solid stream oil jet passing through a terminal confined passageway having its length at least 5 times that of the diameter thereof.v

References Cited in the file of this patent UNITED STATES PATENTS Jahnig'et a1. Jan. 17,

Claims (1)

1. A PROCESS OF COKING HEAVY RESIDUAL HYDROCARBON OILS IN A DENSE TURBULENT FLUIDIZED BED OF HOT FINELY DIVIDED SOLID PARTICLES WHICH COMPRISES PREHEATING THE OIL FEED TO A TEMPERATURE APPROACHING BUT BELOW INCIPIENT THERMAL CRACKING TO REDUCE ITS VISCOSITY SUBSTANTIALLY TO A MINIMUM, THEN INJECTING THE NON-VISCOUS LIQUID OIL FEED VERTICALLY IN A PLURALITY OF SUBSTANTIALLY CONTINUOUS SOLID STREAM OIL JETS WITHOUT SUBSTANTIALLY ATOMIZATION DIRECTLY INTO SAID FLUIDIZED BED AT VERTICALLY SPACED POINTS THEREIN AT A JET VELOCITY ABOVE ABOUT 35 FEET PER SECOND TO MINIMIZE AGGLOMERATION OF THE FINELY DIVIDED SOLID PARTICLES,

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