US1811272A - Cracking of hydrocarbons and treatment of residues - Google Patents

Description

June 23, 1931. i E. w. :soM 1,811,272

CRACKING 0F HYDROCARBONS AND TREATMENT OF RESIDUES Filed June 30, 1924 2 Sheets-Sheet l Condenser Receiver Reflux Tower Pressure 511' H Cafing Furnare Edward 'W. 150m ATTORNEYS June 23, 1931.

E. W. ISOM CRACKING OF HYDROCARBONS AND TREATMENT OF RESIDUES Filed June 30, 1924 2 Sheets-Sheet 2 INVENTOR Edward W. 160m ATTORNEYS Patented June 23, 1931 UNEED STATES ATEN OFFICE EDWARD W. ISOM, OF WINNETKA, ILLINOIS, ASSIGNOR T0 SINCLAIR REFINING COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF MAINE CRACKING OF HYDROCARBONS AND TREATMENT OF RESIDUES Application filed June 30,

This invention relates to improvements in the cracking of heavier hydrocarbon oils for the production of lighter hydrocarbon oils therefrom. More particularly, it relates to 5, improvements in the operation of pressure stills for the cracking of heavier hydrocarbon oils, such as gas oil, etc., for the production of gasoline or so-called pressure distillate therefrom.

1o The invention includes improvements in the method of pressure distillation, and more particularly it includes improvements in a cyclic process in which tar is drawn off from the pressure still and specially treated to separate the tarry constituents from the oil accompanying them, and in which the separated oil is returned to the pressure still for further cracking.

v The invention also includes an improved methodof treating the tar or residue from pressure stills for the separation of tarry and carbonaceous matter therefrom and for the separation and recovery of the oil accompanying such constituents so as to make it available for further use either in the pressure still or for other purposes.

When heavier. hydrocarbon oils, such as gas oil, etc., are subjected to cracking at high temperatures and pressures in pressure stills,

the cracking operation is accompanied by the formation of tarry or carbonaceous constituents which accumulate in the oil of the charge. As these tarry or carbonaceous constituents increase in amount, there an increased tendency for these constituents to separate out on the heated walls or heated surfaces of the still. In order to reduce this danger, tar is sometimes drawn off from the pressure still during the progress of the cracking operation and additional fresh charging stock or oil is supplied to the still to prevent the content of tar or carbonaceous matter from increasing to an objectionable degree. 'yyhere such tar is withdrawn during the progress of the cracking operation, the amount of the tar withdrawn often amounts to a large proportiolfof the total oil charged into the cracking still; and relatively large amounts of such tar are produced n so the aggregate, since, by withdrawmg tar in 1924. Serial No. 723,081.

this way, the cracking operation can be pro longed for a considerably longer period of time than would be feasible if all of the tar were permitted to remain and accumulate in the pressure still itself.

The present invention relates particularly to the treatment of this tar, withdrawn from the pressure still during the progress of the cracking operation, and withdrawn from the still at the end of the cracking operation; and

the present invention provides an improved process whereby the tar so withdrawn may be directly treated for the separation of the tarry or carbonaceous materials from the accompanying oil, and the oil made available for return to the cracking still freed from all or the greater part of these tarry or carbonaceous constituents.

According to the present invention, the socalled tar withdrawn from the pressure still is admixed with finely divided fullers earth or similar material, and the fullers earth or similar material is brought into intimate contact with all parts of the tarry oil. When the fullers earth has been intimately distributed throughout the tarry oil, the fullers earth and tarry or carbonaceous constituents are separated from the oil for example, b settling, leaving oil free or relatively free rom tarry and carbonaceous constituents. This oil can then be returned to the pressure still for further treatment during the progress of the cracking operation.

Fullers earth appears to have an afiinity for the tarry constituents produced during the cracking of heavier petroleum oil. en it is intimately admixed with and distributed throughout the pressure still tar, it tends to accumulate and adhere to the carbonaceous and tarry constituents. Apparently the finely divided particles of fullers earth act as nuclei about which the tarry or carbonaceous particles collect so that the fullers earth has a clarifying action with reference to these constituents, leaving the body of 011, from which the fullers earth and admixed and attached tarry constituents have settled, relatively freefrom such constituents.

The amount of fullers earth used in treating the pressure still tar will vary somewhat example, the pressure still tar may urated or supersaturated with such tarry constituents will ordinarily require more finely-divided fullers earth than pressure still tar which is drawn off before the tarry constituents become saturated in the oil in which they are formed by the cracking operation. In general, the amount of fullers earth should be suflicient so that after the fullers earth is intimately distributed throughout the oil and the oil is permitted to. settle or otherwise subjected to separation, the fullers earth will remove with it all or the greater part of the tarry constituents, leaving the oil sufliciently clarified for re1ntroduction into the pressure still or for use for other purposes.

7 The treatment of the pressure still tar With the finely divided fullers earthlcan be carried out in various types of apparatus and according to various methods of procedure. For

be collected in a storage tank and the finely divided -fulle-rs earth added thereto and intimately admixed therewith, and the fullers earth and tar may then be permitted to settle, the fullers earth dragging the tar to the bottom of the tank and leaving the relatively tarfree oil so that it can be drawn off after the settling has taken place. Such a settling tank'may be provided with agitators 0r stirrers, for stirring the fullers earth into the oil and insuring intimate distribution of the fullers earth throughout the tarry oil.

Instead of treating a batch of pressure still tarin this way, the treatment can be made more or less continuous, for example, by adding the fullers earth in regulated amounts continuously or intermittently to regulated amounts of the pressure still tar and causing thorough agitation of the earth and tar in a continuous manner, for example, by passing the tar with admixed fullers earth through an agitating apparatus where the fullers earth is intimately distributed throughout the pressure still tar. After this intimate distribution has taken place, the tar and admixed fullers earth can then be run into settling tanks and the fullers earth and tar permitted to settle so that. the oil fromwhich the tar has been more or less completely settled can then be drawn ofi' andreturned to the pressure still.

Inasmuch as the pressure still tar is drawn off at a high temperature, and is more thinly fluid at such high temperatures than after cooling, the admlxture of the tar with fullers earth andthe treating operation can be carried out with the hot .tar, and the fullers earth and tar separated therefrom while the remaining oil is still hot; and the clarified 011 can be returned to the pressure still and its heat to a greater or less extent conserved and utilized both in the fullers earth treatment and in avoiding the necessity for re hteillting theoil upon its return to the pressure s 1 Or the pressure still tar may be cooled after it is withdrawn from the pressure still todecrease the solubility of the tarry and pitchy constituents in the accompanying oil and to assist in the separation of the tarry and carbonaceous materials by decreasing their solubility in the oil. The tar withdrawn from the pressure still maybe cooled before it is subjected to treatment with the fullers earth; or the admixture of the tar with the fullers earth canbe carried out with the hot tar and the admixed tar and fullers earth cooled before or during separation of the fullers earth and tarry constituents retained by the fulle'rs earth. I A lighter oil may be added to the tar withdrawn from the pressure still to assist in the separation of tarry and carbonaceous constituents by the fullers earth treatment. For example, a gas oil or kerosene character fraction may beadded to the pressure still tar before it is admixed with the fullers earth.

The lighter oil added to the pressure still tar may be, for example, pressure distillate bottoms from the fractionation of crude pressure distillate or a suitable fraction derived from crude pe roleum.- Where the treated oil from which tarry and carbonaceous constituents have been separated is returned to the pressure still, the added oil is advantageously of a character suitable as a part of the charging stock going to the pressure still. Where a lighter oil is mixed with the withdrawn tar to assist in the separation of tarry constituents, a part of the fresh charging stock to the pressure still may be added to the tar before treatment with the fullers earth and introduced into" the pressure still with the treated and clarified oil.

Before the treatment with fullers earth,

a part of the lighter oily constituents withdrawn with the tar from the pressure still may be separated by vaporization and condensed and returned to the pressure still or otherwise disposed of without going through the treatment with fullers earth. The hot tar withdrawn from the pressure still under pressure may be subjected to reduced pressure while hot and a part of the lighter oily constituents accompanying the tar vaporized by the reduction in pressure and the tar cooled by the vaporization. The unvaporized tar may then be admixed with the fullers earth and the earth and admixed and attached tarry and carbonaceous materials separated from the remaining-unvaporized oil. The treated and clarified oil can be returned to-the presr sure still or used for other purposes.

The invention is of more 'or less general application to the treatment of pressure still tar from various cracking operations in which such tar is formed. It is particularly advantageous however for the treatment of pressure still tar such as is drawn oil from cracking stills during the progress of the cracking operation and in which the tarry constituents do not greatly exceed in amount that which will saturate the oil in which they are contained. The amount of such constituents may even be less than that which will cause saturation" of the oil carrying them, although the amount may be considerably in excess of the saturation point, particularly toward the end of the cracking operation. The invention is thus of particular value in connection with so-called semi-continuous operation of pressure still in which, during the latter part of a pressure still run, tar is drawn off more or less continuously and in relatlvely large amount in the aggregate, and in which the tarry constituents are admixed with and car ried' by a relatively large amount of oil suitable .for charging stock in the cracking process from which the oil and tar are withdrawn.

Thei separationof the fullers earth and tar from the treated and clarified oil can be effected in various ways. Instead of per- -mitting the fullers earth and tar to settle from the supernatant oil, the separation can be efiected by centrifugal means or by filtration, and this separation can be carried out either upon successive batches of the oil, or in a more or less continuous manner.

- The improved oil product of the invention from which the tar has been separated by the fullers earth treatment is of the same, or substantially the same, composition as the oil in the pressure still from which the tar is withdrawn, except that it has been separated from all or the greater part of its tarry constituents. The fullers earth treatment, moreover, has a purifying and clarifying eflect upon the oil, so that after the separation of the fullers earth and tar, the clarified oil is particularly advantageous for return to the cracking still for admixture with the oil undergoing cracking therein. The improved oil product is of low viscosity, due to the cracking treatment to which it has been subjected, and is of advantage for use as a fuel oil where a clean oil is necessary or desirable. The treated and clarified oil is substantially free from constituents tending to deposit in feed connections or in burners. v

The present invention accordingly provides an improved cyclic process in which tar withdrawn from a pressure still is subjected to a refining operation with fullers earth, to separate all or the greater part of the tar from its accompanying oil, and in which the separated oil is returned to the pressure still to undergo further cracking therein.

This cyclic process can advantageously be carried out in conjunction with pressure stills such as are now operated according to the the tar to be recovered in a form well adapted for return to the pressure still for use in the further carrying out of the same pressure distillation operation.

Instead, however, of returning the clarified oil to the same pressure still during the same runfrom which the oil is withdrawn, it can be stored until needed and used as fresh charging stock at the beginning of the operation of a pressure still, or it can be introduced into some other pressure still, either as a part of the charge, or continuously, or at successive times during the progress of the cracking operation.

The fullers earth treatment of the present invention does not introduce into the oil any objectionable or undesirable constituents; rather it tends to free the oil from undesirable constituents, particularly sulfur-containing constituents which the oil and particularly the tar contained in the oil may contain; and it does not subject the oil to cracking decomposition.

Considered as a cyclic process, the present invention accordingly involves first carrying out the pressure distillation with the production of tar or tarry constituents in amounts sufficient to make it desirable to withdraw tar during the cracking operation; treating the withdrawn tar with fullers earth to separate the tarry constituents from the oil in which they are contained; and returning the oil from which the tarry constituents are thus separated, to the cracking still.

When this treatment is carried out upon hot tar, the oil returned to the still may still retain a considerable amount of the heat con tained in the tar as withdrawn; and the fullers earth treating operation is promoted by the fluidity of the hot tar and the increased facility with which the earth can be admixed therewith and the admixed earth and tar settled therefrom.

The tar or tarry residue produced by socalled digestion processes, or the tar or tarry residue remaining after the vaporization of part of the oil by the self-contained heat of the tar or synthetic crude or other cracked product, can be similarly treated according to the fullers earth treatment of the present invention for the separation of the rtarry constituents from the oil in which they are contained; and the clarified oil can be returned if desired to the cracking process or admixed with fresh charging stock for the cracking process, or used for other purposes.

Instead of using divided fullers earth for treating the pressure still tar or similar tar, other similar adsorbent materials having a similar clarifying eflect may be used. Certain other clays or acid-treated clays can be used in a similar manner, as can also materials like silica-gel, although fullers earth is well adapted for use in the process and its availability and low cost make it particularly advantageous.

The invention will. be further described and illustrated in connection with the cracking of oils in a pressurestill'of the general construction illustrated in United States Letters Patent No. 1,285,200 granted to the Sin-. clair Refining Company, November 19, 1918, upon'the application of Edward W. Isom.

The accompanying drawings show in a somewhat conventional and diagrammatic manner in Fig. 1a pressure still ofthe gen eral construction illustrated in said patent, together with a diagrammatic representation of apparatus in Fig. 1A appropriate for use in the carrying out of the fullers earth treatment and. in the carrying out of the cyclic process of the invention. The drawings are not intended to represent to scale the apparatus diagrammatically illustrated.

The pressure still illustrated in the drawings is made up of the bulk supply tank 1 located away from the heating furnace 2, the Vertical heating tubes 3 arranged in the heating flue of the furnace, and circulating'pipes 4, 5 and 6 connecting the lower and upper ends of the vertical tubes with the bulk supply tank and a circulating pump 7 for circulating the oil from the bulk supply tank through the vertical tubes and back to the bulk supply tank. Arranged above the bulk supply tank is the reflux tower 8 having a series of bafiles therein and being connected with the vapor dome of the bulk supply tank through the vapor line 9. An overflow reflux line 10 leads back to the pipe line leading from the bulk supply tank to the circulating pump. The vapors from the top of the reflux tower escape through the vapor line 11 to the condenser 12, where the vapors are subjectedto condensation. The condenser discharges into the receiver 13, from which the uncondensed vapors and gases are withdrawn through connection .14 and the condensate through connection 15. A feed line 16 is provided for feeding fresh charging stock to the reflux tower 8. An additional feed line 17 is provided for feeding fresh oil to the circulating stream of oil through the pump 7. A tar draw-01f 18 is provided adapted for use during the operation of the pressure still. A pumping out line for discharging the still is shown at 19. For pumping out the still, the valve 20 in the line 21 is closed and the valve 22 in the pumplng out line 1s opened.

The pressure may be regulated and reduced by means of a. regulating valve 23 between the reflux tower and the condenser, or by regulation of valves in the connections 14 and 15 beyond the receiver.

The tar draw-off 18 is arranged to discharge into a receiving tank 24. The rate of withdrawal of the tar from the pressure still 1 and the reduction of pressure between the pressure still and the receiving tank 24 may be regulated by means of a valve 25 in the line 18. The tar collecting in the receiving tank 24 is withdrawn through the connection 26 by meansof a pump 27. Vapors liberated in the receiving tank escapethrough connections 28, and can be discharged to the condenser 29 through connection 30, or may be otherwise withdrawn through the outlet connection 32.

A cooling coil 33 is arrangedwithin the receiving tank, and may be regulated or cut out by means of valves 34 and 35.

The tar withdrawn from the receiving tank 24 is discharged into the agitator 36 where it is admixed with finely divided fullers earth or the like. The treating agent is introduced into the agitator through chute 37 from the elevated bin 38. A power driven mixer 39 is provided in the agitator for distributing the treating agent through the tar The admixed tar and treating agent are discharged from the agitator through connection 40.

From the agitator 36, the admixed tar and fullers earth, or other treating agent, are introduced into one of a series of settling tanks 41, 41, etc. through valved connections 42, 42', etc. A suflicient numberof settling tanks can be provided to render the treatment of the tar-substantially continuous, and, it will be understood that the tar from one still or from battery of stills can be handled in a single treating apparatus of appropriate capacity. In the settling tanks e. g. 41, the treating agent and'the associated tarry constituents are allowed to settle and the oil from A which the tar has been more or less completely A fpump 47 is provided for returning the clari ed oil from the storage tank through the line 21 to the pressure still for carrying out the cycl c process of the invention; or the clarified oil may be withdrawn through the valved outlet 48 for introduction into other pressure stills or for other suitable purposes.-

When the clarified oil is returned to the ressure still through the line .21, the valve 22 is closed and the valve 20 is opened. Any tain the charge in the pressure still approxicondensate from the condenser 29 can be discharged into the storage tank 44 through connection 49 and returned to the pressure still through line 21 with the clarified oil, or withdrawn with the clarified oil through connection 48, or this condensate may be Withdrawn through connection 50 and put to other use.

In the operation of an apparatus such as that diagrammatically illustrated in the drawing, the pressure still will be charged, for example, with a gas oil charging stock and the cracking operation will be carried out in much the usual manner. During the early part of the cracking operation, the formation of tarry or carbonaceous constituents takes place slowly and for a considerable period of time there is no occasion for the withdrawal of the tar. When however, the amount of tarry constituents accumulating in the oil has reached the saturation point or has increased to such a degree as to make it desirable to prevent further accumulation of tarry constituents in the oil, the withdrawal of tar begins and this withdrawal may take place continuously during the remainder of the run.

The tar thus withdrawn is admixed with the fullers earth and the earth and tar are intimately admixed with each other so that the fullers earth comes into contact with all parts of the tar. The earth-treated tar is then permitted to settle so that the fullers earth will settle to the bottom of the settling tank and will drag down with it all or the greater part of the tarry constituents. After the oil has been sufliciently settled, the oil may be withdrawn and returned to the pressure still. a

As an example of the practice of the process of the present invention in apparatus of the character illustrated, the pressure still may initially be charged with from 8,000 to 10,000 gallons of a gas oil character charging stock and brought to cracking conditions of temperature and pressure, distillate may then be taken off and fresh charging stock introduced at a corresponding rate for a period while the amount of tarry constituents in the charge are building up, during this period the'rate of distillate oil may be from 800 to 1,000 gallons per hour and the rate of fresh feed about 1,000 gallons per hour, before the accumulation of tarry constituents tar may be withdrawn at a rate of about 1,500

- gallons per hour, and the rate of distillate 01f maintained at about 1,000 gallons per hour, to maintain the concentration of tarry constituents in the charge below an objectionable value. This tar withdrawn may be treated for separating the tarry constituents from the associated oil and the clarified oil returned to the pressure still and additional charging stock may be introduced to mainmately constant. Before the conclusion of the run, the withdrawal of tar and the return of the clarified oil and the additional charging stock may be terminated and the concentration of tarry constituents in the charge allowed to build up during the final period of operation. W'here fresh charging stock is introduced through the reflux tower on a pressure still in amount corresponding to the amount of distillate taken off, the returned clarified oil and any additional fresh stock may be introduced directly into the still proper, for example, in a pressure still of the type illustrated, the returned clarified oil may be introduced into the circulating line and the additional charging stock through the circulating pump.

It will thusbe seen that the present invention provides a new and improved method of treating pressure still tar or similar tarry products from cracking operations for the separation of the tarry constituents from the oil with which they are admixed or in which they are dissolved or carried in suspension; and that this fullers earth treatment can advantageously be combined in a cyclic process in which the clarified and recovered oil is returned and subjected to further cracking in the pressure still from which the tar is withdrawn, or in other pressure stills where charging stock of the character thus recovered will undergo further cracking. It will also be seen that the process of the invention provides an improved oil product which has several important advantages for use as pressure still charging stock or as a fuel oil or for other purposes where a clarified oil of low viscosity is required.

I claim 1. The method of treating oil mixtures containing tar produced by the cracking of hydrocarbon oils under pressure when heated to approximately the cracking temperature, which comprises subjecting the tar and oil to a substantial reduction in temperature and dispersing thercthrough finely divided adsorbent material, and thereafter separating the adsorbent material and accompanying tar from the remaining substantially tar free oil.

2. A method of treating oil mixtures containing tar produced by the cracking of hydrocarbon oils under pressure, which comprises vaporizing the lighter oily constituents from the oil mixture, dispersing through the tar and remaining oil finely divided adsorbent material, and separating the adsorbent material and accompanying tar from the remaining substantially tar free oil.

3. The improvement in the operation of pressure stills for cracking hydrocarbon oils which comprises withdrawing from the pressure still, during the cracking operation pressure still tar, vaporizing lighter oily constituents from the tar thus Withdrawn, subjecting the 'unvaporized tar to treatment with finely divided adsorbent material, separating the adsorbent material and accompanying tarry constituents from the treated oil, and 5 returning the treated oil to the pressure still. 4. The improvement in the operation of pressure stills for cracking hydrocarbon oils which comprises withdrawing from the pressure still, during the cracking operation pressure still tar, vaporizing lighter oily constituents from the tar thus withdrawn, subjecting the unvaporized tar to treatment with finely divided adsorbent material, separating the adsorbent material and accompanying tarry constituents from the treated oil, collectingthe vaporized constituents and returning them ,and the treated oil to the pressure still. 5. The improvement in the operation of pressure stills for cracking hydrocarbon oils, which comprises withdrawing tar and adding fresh charging stock during the progress-of the cracking operation to maintainthe pressure-still charge below saturation with tarry constituents, subjecting the tar thus withdrawn to treatment with finelydivided adsorbent material, separating the adsorbent material and accompanying tarry constituents from the oil, and returning the treated oil to the pressure still.

The improvement in the operation of pressure stills for cracking hydrocarbon oils, which comprises withdrawing tar during the progress of the cracking operation, subjecting the tar thus withdrawn to treatment with finely divided adsorbent material, separating the adsorbent material and accompanying tarry constituents from the oil, returning the treated oil to the pressure still, and controlling the rate of tar withdrawal from and supply of oil to the pressure still to to maintain the pressure still charge below saturation with tarry constituents.

In testimony whereof I afix my signature. EDWARD W. ISOM:

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