US2146553A - Vapor-phase cracking process and the production of fog - Google Patents

Description

Feb. 7, 1939. y E.w REMBERT' 2,146,553

VAPOR PHASE CRACKING PROCIEISSi AND THE PRODUCTIQN OF FOGS FiedgJulyzz, 19:52 2 sheets-sheet /17 f mvENToR ATrORNE Feb. 7,l 1939. E; w, REMBERT 2,146,553

VAPOR PHASE CRAGKING PROCESS AND-THE PRODUCTIONOF FOGS .BMM

' ATTORNEY 'more readily.

Patented Feb. 7, i939 UNITED STATES PATENT OFFICE VAPOR-PHASE cRAoKING PROCESS ANI) THE PRODUCTION OF FOG N. Y., a corporation of Delaware Application July zz, 1932, serial No. 623,979

14 Claims.

process, such as disclosed in my Patent No.

1,892,534, dated December 27, 1932, in which the material to be converted is intimately mixed with hot gas and is by this direct heating vaporized and/or superheated to conversion temperature. The oil to be` converted may be introduced into contact with the hot combustion gases or other heating medium either in the state of vapor or as a liquid spray. In the case of heavy stocks, which are dicult to vaporize satisfactorily outside of the mixing and reaction unit, introduction of the material in the liquid phase is desirable. Existing atomizing or spray nozzles, however, are apt to be unreliable when heavy material is to be fed to a cracking operation of this kind. In the spray formed by such nozzles there is a range in the size of particles, and, if the nozzle becomes dirty, scaled or abraded through use, the spray is likely to become irregular, with the production of excessively large drops. These larger drops, when mixed with the hot, inert gas for cracking in the vapor phase, do not vaporize fast enough to prevent a portion of the liquid actually striking the walls of the mixing chamber. When this occurs, the result is the production of coke, lampblack and gas. Also, when large drops are present, the rate of vaporization is slow compared with the rate of cracking, with the results that a certain amount of coke is formed in the liquid phase, and also excessive amounts of gas and fixed carbon in the form of lampblack are formed in the vapor phase. Such conditions give lower yields of gasoline or other liquid products and make it necessaryto interrupt the operation for cleaning more often than is desirable. i

An object of this invention is to make it possible to crack heavy material by intermixture with hot gases, Without coke formation and Without attendant difculties and losses, when the hydrocarbons to be converted are fed either of mixing with the hot gas.

oils, such as distillates, that can be vaporlzed In this process, the liquid oil is atomized with or by a gaseous fluid, which may be either a vapor or agas, before it is brought tact with the heating gas, to. a treatment which y removes all droplets large enough to suffer loc-al overheating and yield coke in the mixing and heating chamber or the reaction chamber. In this Way, a feed stream consisting of a satisfactorily fine suspension of the liquid in the carrying gas or vapor is obtained, and it is this stream Which is mixed with the heating agent. In general, the temperature of the mist or fog so fed should be in th-e neighborhood of 750-850 F., the temperature being determined, however, 15 by the refractoriness of the material; that is, if the material can be cracked easily the temperature at which it is permissible to feed the material is relatively low.

The entire supply of hot gas for instantly vaporizing the liquid particles and for superheating the vapor to conversion temperature may be mixed with the feed stream at one point,

or this mixing and heating may be effected in stages as disclosed in my copending application Seri-al No. 623,978, filed July 22, 1932, without altering the invention. v

The invention contemplates the elimination of all liquid particles above a given or troublesome size and the production of a feed material which 3o is in the nature of a mist or stable fog,- but even though the separation may be conducted in a less effective manner or the atomization be less drastic the evils of coking and excessive pro duction of lampblack and fixed gas can be greatly mitigated. Therefore, I do' not necessarily limit myself to the production and utilization for vapor-phase cracking purposes of a suspension consisting altogether of particles so small as to be regarded technically as the liquid phase of a 40' fog or mist, and these terms are,` therefore, to be understood in a somewhat general sense. Indeed, .as will be disclosed, after a fog-like or mistlike stream, carrying a large part of the liquid material to be vaporized and cracked, has been formed, Vsorne additional liquid m-ay be atomized in contact with this stream, and the issue may then be mixed with the heating gas without a further separation of such larger droplets as may result from the iinal atomization.

The gaseous fluid employed in the atomization and to serve as the carrier for the liquid particles may be a true gas, such as fixed hydrocarbon gases, for example, or it may be a vapor, such as steam. Preferably, however, this fluid consists of hydrocarbon vapor, which is itself to be cracked. More especially, the invention includes the heating and partial vaporization of oil to be subjected to the cracking reaction, and the automization 'of the unvaporized portion in the vapor thus or Without release into a separating zone at rela' tively reduced pressure, the vapor which is evolved from the oil may be supplementel by steam or by other medium. Again, a heavy oil `can be heated with comparatively little or no vaporization, and this hot oil can be mixed and atomized with the vapors obtained hy substantially completely vaporizing a lighter oil or distillate, such as gas oil.

A single separation of large droplets following atomization of the oil in contact with the gaseous fluid, and before mixing the feed stream with the hot gas, can be made to suffice, but in the p're-u :erred and most effective mode of execution of the invention liquid is atomized in successive stages, with corresponding successive separations of larger liquid particles, until a definite limit. of size of'particle has been obtained in the iog or mist, or until a definite quantity of liquid has heen suspended in the gaseous carrying huid.

A further feature of the invention consists in the maintenance' of baci; pressure in the atomizing and separating system, and the abrupt release ci the mixture of gaseous fluid and suspended liquid particles from this baci; pressure, with consequent production of a finer mist or fog, since on the release of pressure a portion of each inoividual droplet will vaporize automatically and thus the droplet will shrink. rihe release of pressure is preferably made to take place at the nozzle through which the fog is delivered into contact with the hot gas, though this may be varied.

Other objects and features oi the invention will become apparent as the specification pro-1 ceeds.

In the accompanying drawings forming part hereof:

Fig. 1 is a schematic view oi a system of apparatus for carrying out the invention, one part of the apparatus being shown in section; and

Fig. 2 is a schematic View illustrating a simplifled system, portions of which are shown in section. Numerous other forms and embodiments of the invention will suggest themselves to those skilled in the art.

In Fig. l, the oil to be treated is forced under substantial pressure by a pump 2 through a line 3 to and through the tubes of a pipe still or heater ii. A considerable part of the oil is vaporized, and the vapor and unvaporized oil pass through a line 5 to one of a pair of mixers and preliminary atomizers 6. For practical reasons, it is desirable to duplicate the mixers t and the atomizers l and 7a, and to provide valves as indicated for shutting oi their connections, so that one device of a `pair can be cleaned wmle the other is in service. The mixers 6 may be of any suitable construction, as, for example, one employing a Series of orifice plates through which the mixtur.; of vapor and liquid is made to pass.

ausente From the mixer, the material is delivered through a pipe to a separator 9, where the large drops o liquid are caused to separate from the vapor and from the majority of small drops which remain in suspension in the vapor.

Liquid is conducted from the separator through piping iii to one ci` a pair of atomizers l?. The vapor laden with small drops passes rom the separator to these atomizers through piping il. The liquid and vapor are again mixed and more liquid is atomized. The mixture proceeds through a pipe i2 to another separator Qa, where all large droplets oi the spray are removed. Liquid collecting in this separator ows throu 1i piping i3 to one of the atomizers le, to which the vapor-carried spray or mist is conductedI through piping lfl. Liquid is again broken up in passing through this atomzer, enriching the fog, which is then delivered through a pipe to a separator db, where a final removal of over size particles is effected. The liquid leaving this separator through valved line it may be un e drawn from the system or may be delivered te hot oil storage for re-cycling.

The og or mist ot very fin-e particles in suspension in the vapor leaves the last separator through a valved pipe il and passes to the feed nozzle IE or the mixing, heating and cracking unit i9.' There it enters a suitable mixing chainber or tube where it is intimately mixed with hot and inert combustion gases from a com' tion chamber 2l, this combustion chamber ing burners die which are supplied with a liquid or gaseous fuel by blowers througl: lines 22, 23. The liquid material in the issue from the nozzle it, because of the ne state of division in which it exists, and because all or practically all large drops have been excluded, is vaporized at once. For the same reasons, coi;-s ing on the Walls isavoided or reduced to a mir."- mum, and the mixing, heatingi and cracking operation proceeds continuously for an inde?.- nitely long time and in an economic manner. The mixture of the heating gas and vapor proceeds through a heat-insulated and grefractory-l Walled reaction chamber 2Q, Where it is lrept at the conversion temperature, preferably above 900 F., for a predetermined brief reaction time, at the conclusion of which it is quenched to a temperature sufficiently low (750 F. or less) to arrest the reactions. In respect to these matters, tne operation is preferably carried out in accordance with the process disclosed in my Patent No. 1,892,534.

The quenching liquid delivered through spray nozzles in quencher 25a into contact with the mixture issuing from the reaction chamber is preferably the charging stock supplied through a charging line 26, and the oil thus preheated, or the unvaporized part thereof, is preferably the 'material which is circulated through the pipe still d. The materials proceeding from the quencher may be passed through a scrubber 2'! anda separator 28, as disclosed in my copending application Serial No. 623,977, filed July 22, 1932,

.the liquid being conducted thence through line 29 to a hot oil receiver 30, from which the pump 2 derives its supply, While the gases and vapors pass through a line 3l to a fractionating column 32 and the usual cooling and condensing equipment connected therewith.

Reux condensate from the column 32 may be conducted through a line 60 and'be added to the preheated oil from the quencher 2.58', Which is passed through the heater 4. Such admixture pressure 'drop and of the action of the expansivev uld. However, a variety of atomizing devices may be employed. The number of 'atomizersused in series will depend upon the concentration of liquid desired inthe vapor at the end of the system, and, also, the more efficient the atomizers the smaller will be the number of units required in series to accomplish a given result.

The design of va. separator for use at 9, 9 or 9b must be such as to throw out most or substantially all of the drops formed in atomizing that are larger than the desired size. The type that .is most advantageous is one in which the stream from the atomizer is delivered tangentially into a circular chamber of considerable volume, the resulting whirling motion of the mixture in the chamber causing the larger drops to be thrown by centrifugal force `against the walls, down which they flow to the bottom of the chamber. Instead of such separators, it is evident that large drums, in which the velocity -of the stream is slowed down to a point where settling ofthe larger drops occurs, may be employed. Still other types of separator can be-used.

If theloil'fpassedathroughthe pipeestill 4 is'of a kind that yields insuicient vapor, it may be supplemented with steam or with other vapor or gas. Thus, a Valved steam line 33 is is shown joining the still outlet pipe '5 in advance of the preliminary atomizers '6, and lin like manner steam or other additional expansive uid may be introduced at or before any of the atomizers. Valved lines 6I and 62 are s'hown connecting with the piping and I4, for this purpose. The amount of liquid fed from a separator to a succeeding atomizer is regulated so that the pro-- portion of liquid to vapor passed through'the -atornizer is that which will give the most emcient operation. A valved line 34 is shown by which a. portion of this liquid can be by-'passed past the atomizersl 1 to the atomizers 1, or through a further by-pass 35 to the line I6 which conducts liquid from the last separator 9b. to the hot oil storage 30 and/or to a draw-off 63 from the system. Similarly, `a portion of the liquid from the separator ila can be diverted from the atomizers 1a.

Back pressure is held in the atomizing and separating system, and the feed nozzle |8 of the cracking unit, or at an anterior point, is restricted in order to eiect a sharp eventual reduction inpressure. This results in a decided diminution in the size of the liquid particles in suspension in the fog, through partial 'vaporization, regardless of extraneous heating.

The pressure drop across the atomizing and looked. A pressure drop ,of 150 pounds per square' inch across the atomizing and separating systhe egress for the fog at another of these modified operations.

In the particular organization of apparatus i1'- series with others may be as low as 30 pounds per square'inch, `forl example, and may range upwards of about 50 to 60 pounds.

An atomizer unit giving 40 to 50 pounds per square inch pres-v sure drop across it may be consideredas a typical example of a series system.

Fig. 2 illustrates both a simplification of the atomizing and separating process and the atomi# zation of a. heavy oil withthe .vapor of a light oil.; Operation on a heavy crude, fa large portion of which is flashed off in the quencher at temperatures of the order of '700 F., will be more particularly considered. In this case, operation of a pipe still to vprovide suficient vapor for atomizationwould prove difficult.

The crude oil is charged through the line 26 to the quenching spray 25. The hot reduced crude passes to the hot oil receiver 30, from which it is pumped by pump 40 through line 4| to mixer 43. Reflux distillate from the fractionating column 32 is taken through line 44 to reflux receiver 45, whence it is pumped by pump 46 to andthrough pipe still 4, Where it is practically completelyvaporized. Part of this oil may be removed from the system at 63. 'Ihe vapor, and liquid if any, from the still 4 joins the hot oil stream in the piping 4|, and the liquid and vapor are churned in the mixer 43 and are delivered into the separator 48, from which liquid, andvapor carrying a proportion of droplets, are taken off through pipes 49 and 50, respectively, leadingl to atomizer 5|. The fog or mist produced in the atomizer is delivered into av'separator 52, ,wherein large drops are thoroughly removed. The fog then proceeds through pipe 53 to the feed nozzle 54 of the mixing, heating, vaporizing and reaction unit |9. 'The liquid separated in the separator 52 is returned through line 55 4to the hot oil receiver. 30.

A portion of the liquid oil from the separator 48 maybe by-passed through line 56, past the atomize'r 5|, and be returned to hot oil storage.

Part of theheav'y material may be withdrawn' from the system,v as it may be necessary or de: sirable to do so, through a draw-off 51 connected with the reservoir 30, or elsewhere.

The Valved line 58 indicates the possibility of supplying a certain proportion of liquid oil to the feed nozzle, which in that event would be an atomizin'g nozzle. If the proportion of oil thus atomized directly into contact with the hot gas is not large in proportion to the volume of pre-A formed stable fog, little or no diil'iculty in achievA ing vaporization without 4coking or excessive gas and carbon formation need be encountered.

A system such as' illustrated in Fig. 2 is made more exible by providing for interconnections in advance of the heater- 4, between the reflux from the fractionating column 32 and the heavy or residual-containing stock that is accumulated.

in the reservoir 30. Operations or processes differing specifically from the vone just describedv can be carried out with the same apparatus, or the system may be denitely designed for one 'or lustrated in Fig. 2 a pipe 64gis shown-cross-connecting the heavy-oil line 4| with the connection between the reflux receiver and the pump 46 that forces oil through the still or heater 4. In the operation that has been described, the valve 65 in the pipe 64 would be closed. By opening this valve more'or less and by properly adjusting the valve 6E in the line M, any desired part of the heavy oil stream on its way to themixer 43 can be diverted and can be passed together with the light oil or reiiux through the still 4 when the temperature of the heavy oil stream needs to be raised. If the hot oil from the quencher 25EL be of such character that a suicient portion of it can be vaporized readily, the valve B6 may be closed, in which event all of the material would be pumped through the still, to be partially vaporized therein. Finally, all of the tower reflux might be removed from the system', as at 63, and only the hot oil from the quencher be passed through the still.

Numerous other modifications and applications of the invention will suggest themselves to those skilled in the artsto which it relates.

I claim:

1. A method of treating hydrocarbons, which comprises atomizing hot oil in hydrocarbon vapor, both of which are to be cracked, separating the larger droplets of liquid from the resulting mixture to obtain a feed stream consisting of the hydrocarbon vapor and much liquid material consisting of suspended ne liquid particles, and vaporizing the particles and subjecting the vapors to a cracking reaction, the heat for vaporization, superheat and cracking being supplied by hot gas With which said feed stream is contacted and intermixed after the feed stream has been formed.

2. A method of treating hydrocarbons, which comprises heating oil material and vaporizing a part thereof atomizing the unvaporized liquid lin the vapor obtained from the original liquid, and thereafter bringing the resulting mixture of vapor and much atomized liquid into intimate contact with gaseous heating fluid sucient in temperature and amount to Vaporize the atomized liquid and 4crack the vapors.

3. A method of treating hydrocarbons, which comprises heating oil material under pressure and vaporizing a part thereof, atomizng the unvaporized liquid in the vapor obtained from the original liquid, separating larger droplets of liquid from the resulting suspension of fine particles in the hydrocarbon vapor, thereby obtaining a fog'or mist, maintaining back pressure on the atomizing and separating steps, abruptly reduc--` ing the 'pressure on the fog or mist to effect re- .duction in particle size by partial vaporization,

and then mixing the fog or mist with hot combustion' gases to obtain a vaporizing and cracking reaction.

4. A method of treating hydrocarbons, which comprises heating oil material under pressure and vaporizing a part thereof, atomizng the unvaporized material in the vapor obtained from the original liquid, separating larger droplets of liquid from the resulting suspension of fine particles in the hydrocarbon vapor, separately withdrawing liquid and asuspension of fine particles in the hydrocarbon vapor from the separation step, atomizing this withdrawn liquid in contact with the Withdrawn suspension, separating larger droplets from the enriched suspension, maintainother of which is not, vaporizing the rst of these oils, mixing the vapor thus obtained with the other hot oil and atomizing the latter, separating the larger droplets of liquid from the resulting mixture to obtain a feed stream consisting of the vapor and much liquid material consisting oi' suspended ne liquid particles, thereafter mixing the feed stream with hot gas and thereby instantaneously vaporizing the liquid particles, and subjecting the hydrocarbons to a vapor-phase cracking reaction.

6. A method of treating hydrocarbons', which comprises continuously supplying two kinds of oil, one of which is readily vaporizable and the other of which is not, vaporizing the first of these oils, mixing the vapor thus obtained with the yother hot oil and atomizing the latter, thereafter subjecting the resulting mixture of vapor and much liquid material consisting of suspended liquid particles to direct heating by intermixing hot gas therewith, to vaporize the liquid particles, and subjecting the vapors to a cracking reaction.

7. A method of treating hydrocarbons, which comprises atomizing oil in a gaseous fluid, separating larger droplets of liquid from the resulting mixture, collecting said larger droplets and withdrawing this liquid, taking oif separately the gaseous uid laden with ne liquid particles, re-atomizing the withdrawn liquid in the mixture of gaseous uid and suspended liquid particles previously obtained, and again separating larger droplets, thereby obtaining an enriched, stable fog, and supplying this fog to a vaporizing and vapor-phase cracking operation in which vaporization of the liquid particles is eiected by in- I termixing the fog with hot gas.

a mixture of gaseous fluid and suspended liquid particles from the separation step, atomizing vthis withdrawn liquid in the withdrawn mixture,

separating larger droplets from the enriched suspension of fine particles in the gaseous uid, mixing a fog or mist thus obtained with hot combustion gases, thereby instantaneously vaporizing the fine liquid particles, and subjecting the hydrocarbons to a vapor phase cracking reaction.

9. A method of treating hydrocarbons, which comprises atomizing oil in a gaseousuid, separating larger droplets of liquid from the resulting mixture, separately withdrawing liquid and a mixture of gaseous fluid and suspended liquid particles from this separation step, atomizing this withdrawn liquid in the withdrawn mixture, separating larger droplets from the enriched suspension of iine particles in the gaseous fluid, regulating the amount of liquid supplied to an atomizing step and by-passing the remainder to a subsequent atomizing step, and supplying the fog or mist thus obtained to a vaporizing and cracking operation, in which the material is heated by direct contact with hot combustion gases.

10. A method of treating hydrocarbons, which comprises atomizing hot oil in a hot gaseous fluid, both of which are supplied under pressure, separating larger droplets of, liquid from a suspension of fine particles in the gaseous uid, thereby obtaining a fog or mist, maintaining back pressure on the separating and atomizing steps, abruptly releasing the fog r mist from the pressure, mixing it with hot com `ustion gases at least fil sufilcient in temperature and amount to vaporize the liquid particles, and subjecting the vapor to a cracking reaction. l

11. A method of treating hydrocarbons, which comprises atomizing oil in a gaseous fluid, separating larger particles of liquid from the resulting mixture, enriching the stream of gaseous uid and suspended particles thus obtained by mixing it with a regulated amount of hot oil and atomizing the latter, and by such steps obtaining a feed containing a large amount of finely dispersed liquid, which feed is then mixed with hot f gas to increase the temperature sufdciently to vaporize the liquid particles and crack the hydrocarbons in the vapor phase. l

12. A method of treating oil, which comprises heating the oil and vaporizing a part of it, separating the vapor and the unvaporized liquid, withdrawing a stream of the unvaporized liquid and atomizing this stream in the vapor so that the vapor becomes charged with droplets, delivering the carrying vapor and carried droplets to a separating zone, there removing larger droplets, and by such steps producing a feed stream in the nature of a iine mist, which is eventually mixedwith enough heating gas of suiilcient temperature to vaporize the liquid particles and crack the vapors.

13. A method of treating oil by atomizing oil in contact with a gaseous carryingmedium. thereby charging the carrying medium with droplets, eliminating the larger doplets from the mixture and by such steps producing a stream of very ne particles suspended in the medium,l which is then mixed with enough high temperature gas to vaporize the liquid particles and crack the vapors. i

14. A method for the conversion of hydrocarbon oils, which comprises atomizing liquid cil in and by its own vapor, to produce a fog or suspension of i'lne liquid particles in the vapor, removing insufficiently atomized oil from this suspension,

thereafter mixing the fog-like suspension with

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