US1696658A - Process of cracking hydrocarbons - Google Patents

Description

Dnc. l25, 1928.

M. J; TRUMBLE PROCESS OF; CRACKING HYDROCARBONS Original Filed Sept. 2', 1924 3 Sheets-Sheet 2 D@n 25, 192s.

1,696,658 M. J. TRUMBLE y PROCESS OF CACKING HYDROCARBONS original Filed' sept. z, 1924 A :s sheets-sheet 5 PATENT OFFI CE.l

MILDN J'. TRUMBLE, 0F ALHAMBRA, CALIFORNIA. l

PROCESS 0F CRACKING HYDROCARBONS.

Application lie'd September 2, 1924, Serial No. 735,357. Renewed October 24, 1928.

My invention relates to the art of cracking hydrocarbons. It is well known, if hydrocarbons, and partcula `ly petroleum oils, are subjected to proper tempera-ture and maintained under suiicient pressure, that a partial breaking up of the oils occurs and low boiling point oils are produced, a considerable proportion of the gasoline -now in use in the United States beingproduced by such cracking processes.

In the operation of these cracking processes, in addition to the gasoline, there is usually produceda residuum containing considerable quantities of free carbon or tarry hydrocarbons, and the principal problem met with in the design and operation of cracking processes is to provide means for disposing of this solid or semi-solid residue and to prevent its interference with the normal operation of the apparatus.` I have found, however, `that a certain amount of free carbon is very beneficial in the cracking of oil, and I believe that the free carbon may act as a catalyzer inthe promotion of the cracking reaction. It is, therefore, an object of my invention to provide a cracking process in which large amounts of free carbon are maintained in intimate association with the oil to 4be cracked for the purpose of'increasing the yield of low boiling .point hydrocarbons therefrom. l

It is a further object of my invention to provide means by which the sc lid and semi.-

solid portions of the residue may be mechanically broken up and mixed With the oil for the purpose of promoting the cracking re ,ction. l l

It has been found, however, where considcrable amounts of solid or semi-solid carbonaceous material are so produced or present in the usual form of cracking still that there is a. marked tendency for these solid or semi-solid residues to adhere to and buil@ up upon the heating surfaces of the still, forming layers ofsolid carbon which cover these heating surfaces, and not only prevent a proper transfer of the. heat tothe oil to be treated, but which also tend tocause local overheatingat these surfaces, With a consequent damage to the stills.

It is a further object of my invention to provide means for mechanically preventing the adhesion of the carbonaceous material to the heating surfaces, a thin layer of carbona-v ceous material being maintained to pro-mote the cracking reaction, but the thickness of this layer being so limited as not to impair the heating value of the surfaces.

I have further found that it is desirable-that the material which is mechanically removed not readily affected by the cracking reaction,

still has the property of dissolving many products thereof. It is accordingly hereinafter referredto either as a solvent oil or as a carrier oil.

It is a further object of my inventionl to so circulate this solvent oil that the active heating surfaces of the apparatus are constantly washed thereby, thus carrying away the solid and semi-solid residues, in a thin film descending under the action of gravity,as fast `X as they are formed.

It is a further object of provide means for sett-ling from the solvent oil the heavier portions of the suspended material.

Further objectsl andl advantages will be made evident hereinafter.

Referring to the drawing which is for illustrative purposes only,

Fig. 1 is an elevation of an apparatus suited to carry on my process.

the invent-ion to Fig. 2 is a diagram showing-the method of operation of the heating surfaces.

Flg.- 3 is a sectional elevation on the line 3 3 of Fig. lon a somewhat larger scale. F 1g. 4 is a section on a plane represented by the line 4.--4 of Fig. 3.

Fig. -5 isla section on a plane represented by the line 5-5 of Fig. 3. Fig. 6 is an enlarged view of the bottom of the cracking chamber in Fig. 1, showing parts broken away. i Y

In thepractical operation of my linvention I employ a furnace 11 having a flue 12 which projects through a cracking still 13. Sur-` rounding the upper portion of the cracking still 13 is a settling and separating chamber 14, which communicates with carbon chambers 15 and Vapor from the top of the still 13 1s delivered to a dephlegmator '17,

light vapors being taken from the top thereof to a condenser 18. v

The cracking still 13 consists of a tight shell 20 joined by means of a bottom 22 with a heat insulated inner wall 23, which extends up and joins the flue 12 alt 24. A heat insulation isprovided for the purpose of keeping by a wormv33, which in turn is driven by a suitable pulley 34 outside the still 13. Attached to the worm gear32 are two helical scrapers 35 and 36, these Scrapers Htting tightly about the Hue 12 and serving to scrape the solid material from the outer 'surface thereof. -Secured on the lower end of the members 35 and 36 are a series of Scrapers 37, which tend to prevent Vmaterial from ad-l hering to the wall '23. Surrounding the upper end of the Hue 12, outside the Scrapers 35 and 36, are a main oil distributor40 and a solvent distributor 41. The distributor 40 is connected, as shown' in Fig. 4, by means of av short pipe 42 'with one portion 43 of the settling chamber 14, this portion being formed by a high partition 44 and a' low vpartition 45 inside a shell 46, the partitions 44 and 45 extending from the shell 46 to the shell 20 of the cracking still. Material settling in the bottom of the still 13 is delivered :by a pipe to a pump 51 which lforces this material through a pipe 52 and a nozzle 53 into one end of a portionV 54 of the settling chamber 14. The portion l54 is in communicationwith the portion 43 over the top of' thepartition 45. The Ylower end of the portions '43 and 54 are in communication wlth the carbon chambers 15 and 16, respectively,

. through a-pipe 55 having a valve 56, and

Y shown as provided with apertures permit-- through a pipe 57 having a valve 58. Situated inside the shell 20 and rojecting inwardly close to the members 35 and 36 are a plurality of cones 60; and the shell 20 is ting an equalization of pressure by a movement of gases.

Vapor is taken olffrom 'the top of the cracking still 13 through a pipe 61 and deliveredv to the dephlegmator 17. This dephlegmat-or lconsists of a shell 62 having a ti inlide the shell 62 are ya plurality of oppositely concaved pans 65 and 66. Vapor is taken 0H from the top of the dephlegmator 17 through a pipe 67 and delivered to the condenser 18, Which is of any conventional form. Cold solvent or'carrier oil may be delivered througha, pipe 68 into the top of the dbphlegmator 17, this solvent being carried downwardly over the pans 65 and 66 and delivered through a pipe 69 into the distributor 41. The vdistributors 40 and'41 are perforated 'softhat they tend to spray material on the Hue 12.v The oil to be treated isdelivered through a pipe-70v into the pipe 52.

y The operation of the apparatus iscontinuous.

The apparatus may be started in the following manner:

The solvent or carrier oil, which is preferably a distillate 'having a boiling point wht top 63 and a tight bottom 64. Situated somewhat higher than the cracking, temper'- ature which it is desired to maintain inside the still atthe pressure maintained in the still is delivered through the pipe 68 to the dephlegmator, flowing downwardly therethrough and through the pipe 69 to the Idistributor 41, being sprayed from thedistributor 41 on the outer surface of the Hue 12. This solvent oil Hows downwardly over the Hue ,12 and is finally delivered through the pipe 50 to the pump 51. This pumpprefer ably co-nsists of two gears running in mesh and is of well known form now used for circulating hot liquid. lThe solventoil is then pumped upwardly through the pipe 52 into thc chamber 54, flowing over the partition 45 again sprayed upon the hot Hue 12 and Howing downwardly thereon'. As soon as the solvent oil which is thus circulated over the surface of the Hue reaches, a temperature slightly above that necessary vto crack the raw oil, the valve in the pipe 7 0 is opened and raw oil is delivered to the pipe 52, Howing upwardly therein and being mixed therein with the solvent oil. This raw oil is then delivered with the solvent oil through the distributor 40 to the outer surface of the Hue, Howing downwardly thereover in a thin film. The raw oilis probably partially cracked in the pipe 52 but the greater portion of the cracking takes place during the passage of the oil downwardly in the Hlmof solvent oil on the outer surfaceof the Hue 12. Due to the cracking of the raw oil, hot hydrocarbons and tarry material are formed, which, however, tend to go into solution or suspension in the solvent oil. The Hue 12 being at a higher tempera-ture than'the solvent oil, there is a tendency for these Solid or tarry residues to adhere to the Hue 12-and Ibuild up a layer of coke thereon. The members 35 and 36, being continuously rotated,`

bon. Thereyis, however, a. tendency for this carbonto build up and there is always a thin film of carbon on this surface. This thin Hlm of carbon probably acts as a. eat-alyzcr, tending to promote the cracking of the oil carried by the solvent. The solvent also serves to dissolve or remove from the surface of the Hue 12 the tarry or solid residues formed by the cracking,.all of thisv material passing downward tothe pump 51.

The pump y51 breaks up the solid and semisolid materials, which are then delivered through the pipe 52 and the nozzlev53 int-o the chamber 14. In the portions 43 and 54 of this chamber the solid residues settle out from the solvent, and the valves 56 and 58 being' 'of the shell 20, to form 'time it is necessary to close the valves 56 and 58 and to remove the heavy residue from the chambers 15 and 16, which can' be conveniently Idone through suitable pipes 71 and 71.

- The conical members 60 serve a double purpose. Theyl tend to return to the heating Surface 12 any liquid which may splash therefrom and they also serve, with the inner wall pockets in which light vapors collect.

The vapors produced in the still 13 tend to rise and are carried over by the pipe 6l into the dephlegmator, passing upwardly therethrough outside the pans 65 and through central openings in the pans 66. 'lhesc pans may be kept wet with cold 'solvent delivered through the pipe 68. After the plant has once bee-nbrought into successful operation, however, the supply of oil to either the pipe 68 or the pipe 70 may 'be cut off to any eX- tent compatible with the desired thermal control.

In the ordina-ry operation of thc plant, heavy distillates are caught by the dephlegmator and returned by t-he pipe 69 to the distributor 41, the lighter products passing over through the pipe 67 and condensed in the condenser 18, forming the principal commercial product of the plant. s

In practice solvent oil is produced as an intermediate product but it gradually breaks l up to form low boiling point hydrocarbons and a heavy residue. As a result there is a constant production of such solvent oil and an equally constant breaking up of such solvent. Should the rate of cracking fall so that such solvent is produced faster than it is cracked, the solvent will start to accumulate in the bottom of the cracking still 13, which will become evident to the operator who opens a petcock 83 from time to time. Should he find an accumulation of solvent, he reduces the flow of raw oil through the main intake pipe 70, thus reducing the amount of cold' oil ied into the appara-tus and increasing the temperature in the still. I

In treating California oils, I have operated with excellent vresults with oil temperatures, at the inlet 50 of the pump 51, of from 750 degrees Fahrenheit to 850 degrees Fahrenheit, and with pressures up to 180 pounds per square inch.` I believe this temperature must bein excess of' 700 degrees Fahrenheit to produce good commercial results and that pressures in excess of 20 pounds gauge are also necessary to the best results.

I have found that it is advisable to maintain a large volume ofcirculating solvent as compared with the raw oil. For example, the quantityl of raw oil introduced in a given.` time through the (pipe 70 may be less than 2 per cent of the total fluid circulated in the same time through the pipe 5,2. lThis gives a large volume of solvent on the heating sur- .1'aces, which are thoroughly washed thereby.

I also prov-ide means such as the Scrapers 35 and 36 for mechanically removing adherent matter 4from the heating surfaces.A This adherentlmatter is initially a tarryhydrocarbon, but if allowed to remain on the heating surface it rapidly cokes, producing a hard ma of low heat conductivity Which prevents the ojil from taking heat from the heating surface and causes a. local .overheating at that surface.. By rapidly circulating a solvent oil over the heating surface, I am able tcdissolve the greater portion of said tarbefore it cokes, and by the use of the Scrapers I am able to mechanically remove the coke.

I also provide means such as the gear pump- 5l for breaking up the carbon into fine particles, and I provide means such as the chamber 14 in which the heavy matter, carried in suspension in the oil, is allowed to settle. This heavy matter, consisting largely of free carbon, then settles in the carbon chambers 14 and 15 and is periodically removed therefrom. L

My invention comprises several novel conceptions. I provide means for covering a heating surface, such as the outsidel oli the flue 12, with a rapidly flowing ilm of oil. This film of oil may be largely solvent oil, that is, oil which does not readily -crack at the still temperatures, but which acts as a solvent or carrier for the heavy hydrocarbons produced by the cracking. The rapid circulation of this oil over the heating surface keeps this surface washed so that the heavy cracked products are carried 'away as fast as they are formed. This rapid circulation of the iilm also increases the eiciency of heat transfer from the heatin surface, not only by keeping the `heating sur aces free from adherent sol? ids, |but also by washing oli' gas'bubbles as fast as they form.

By flowing the oil in a lm, the escape of vapors is also facilitated, the vapors readily escaping to cooler portions of the still, Where they cannot interfere With the ready transfer of heat through the body of the oil. The rapid circulation also mixes the oil and prevents local'overheating.

Vhile I have described a definite appara-- tus and certain more or less definite steps of a process, I do not wish my invention to 'bcjlimited to the particular embodiment shown or described, but wish the scopc'of my invention to be defined Wholly by the annexed claims.

I claim as my invention: 120

1. A process for cracking liquid /lydro a carbons under pressure which comprises: flowing said hydrocarbon downwardly in a film over an external vertical surface contained within a pressure chamber; heating said surface internally to a temperature suiicient to cause the cracking of said hydrocarbone; removing the residual carbonaceous products of said cracking action from said surface by a combined mechanical and Washing process; removing the vapor products of said cracking action from said pressure chamber, and condensing said vapors.

2. A vprocess for cracking liquid hydrocarbons under pressure which comprises: flowing said hydrocarbons downwardly in a film over an externalI vertical surface contained within a pressure chamber; lheating said surfacev internally, by means of flue gases, to a temperature sufiicient to cause the cracking of' saidhydrocarbons; mechanically preventing the deposition of the resid u al carbon aceous products of said cracking action upon said heated surface; removing said residual products from said surface by suspension in such liquid hydrocarbons flowing over said surface as are physically stable under the conditions of the pressure chamber; removing the vapor products of said cracking action from said pressure chamber, and dephlegmating and condensing said vapors.

8. A process for cracking liquid hydro cai-bons under pressure lwhich comprises: flowing said hydrocarbons downward yin a film over an external vertical surface contained Within a: pressure chamber; heating said surface internally by means of flue gases to a temperature sufficient to cause the-cracking of said hydrocarbons;'flowing a carrier 39 oil which is substantially stable under the conditions inthe pressure chamber over said surfaceto remove, by carrying 1n suspension Y and solution, the residual carbonaceous products of said cracking action; mechanically preventing the deposition of said residual products upon said surface, and maintaining an intimate contact between said products and said carrier oil; removing the resulting vapor products of said cracking action from 4o said pressure chamber, and dephlegmating /alnd condensing said vapors.

4. A process for cracking liquidghydro-V carbonsy under pressure which coniprises:V flowing said hydrocarbons downwardly .1n a lm over an external vert1cal surface conta' ed within a pressure chamber;l heating.,

sai urface internally by means of flue gases to-.a temperature-sufficient to cause the cracking of said hydrocarbons; flowing a carrier .GuA oil which is substantially stable under the conditions of the pressure chamber over said surface to remove, by carrying in suspension and solution, the residual'carbonaceous products of said cracking action; subsequently e5 removing said suspended residual products from said carrier oil', and recycling said carrier voil throughJ said pressure chamber;.mechanically preventing the deposition of said residual products upon'said heated surface,

U0 and maintaining an intimate Contact between saidI products and said carrier oil; removing the resulting vapor products of said cracking action-from said pressure chamber, andi dephlegmating and condensing said vapors.

y, 35 .5. A process for crackingliq'uid hydrocarbons under pressure -which comprises:

fiowing said hydrocarbons downwardly in a Y jecting said partially clarified mixture to said heating'process; mechanically preventing thevdeposition of said residual products upon said heated surface, and maintaining an intimate contact between said products and said carrier oil; removing the resulting .vapor 'products of said cracking action from said pressure chamber, dephlegmatin'g and condensing said vapors.

-6. A process for cracking liquid hydrocarbons under pressure which comprises:

flowing said hydrocarbons downwardly in.

.a film over an external vertical surface contained within a pressure chamber; heating said surface internally by means of flue gases to' a temperature sufficient to cause the cracking of said hydrocarbons; flowing a carrier oil which is substantially stable under the conditionsin the pressure chamber, over said surface to remove, by carrying in suspension and solution, the residual carbonaceous products-of said cracking action ;imechanica'l'ly preventing the deposition of said residual products upon said surface, and maintaining an intimate'.

contact betweensaid residual products and said'carrier oil; removing the. resulting vapor products of said cracking action from said pressure chamber, 4by passage through a dephlegmator in which said vapors are brought into intimate contact with coldcarrier oil flowing through saiddephlegmator in a direction opposed to the flow of said vapors; said carrier oil flowing from said dephlegmator to said heating surface; said vapors passing from said dephlegmator to a condenser. n u

7 A process for cracking liquid hydrocarbons under pressure which. comprises: flowing said hydrocarbons'downwardly in a film over an external vert-ical surface contained Within a pressure chamber; heating said .surface internally by means ofiflue gases to a temperature sufficient to cause. the cracking 4of said hydrocarbons; flowing a carrier oil which is substantially stable under -the conditions of the pressure chamber, over said surface to remove, by carrying in suspension and solutlon, the residual carbonaceous products of said cracking action; mixing said cari rier oil containing said residual products with raw uncracked hydrocarbons; subsequently partially settling said suspended residual products from said mixture, and sub- -jecting said partially clarified mixture to l lrier oil flowing through said dephlegmator in aldirection opposed to the flow of said vapors; said carrier oil flowing from said dephleg'mator to said heating surface; said vapors passing from said dephlegmator to a condenser.

8. A process 'ofcracking a hydrocarbon under pressure which comprises: fiowing said hydrocarbon downwardly 1n a film over an external vertical heated surface; heating said surface internally to a cracking temperature by upwardly moving flue gases ;luniting with said solvent raw oil and flowing the resulting mixture similarly in a ilm repeatedly downwardly and in contact wtih said heated surface while maintaining the surface at an oil cracking temperature by means of the flue gases, and carrying in suspension in said mixture the unvaporized products of said cracking, and dephlegmating and condensing the resulting vapo 9. Acracking apparatus comprising :a ver ticalchamber; an upwardly extending iiue passing through said chamber; mechanical scraping means rotatable about said flue; means for supplying a thin film of oil de scending under the `action of gravity in con tact with said Hue; means for withdrawing vapors and gases from said chamber; means .for removing liquid and solid residual mixture from said chamber; means for separating said solid and liquld residual substances;

separatelmeans for withdrawing said s olid residue, and means for returning residual oil for treatment-.gv

In testimony whereof, I have hereunto setmy hand at Los Angeles, California, this 26th day of August, 1924. v

MILON J. TRUMBLE.

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