US1851526A - Cracking system - Google Patents

Description

March 29, 1932- E, .1. SHAEFFER ET AL CRACK ING SYSTEM NM, wh,

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Patented Mar. 29, 1932 UNITED STATES PATENT OFFICE EDWARD J. SHAEFFER AND EUGENE P. BROWN, OF WHITING, INDIANA, ASSIGNORS TO STANDARD OIL COMPANY, OF WRITING, INDIANA, A CORPORATION OF INDIANA onacxme SYSTEM Application i filed March 8,

The present invention relates to improvements in the production of low boiling point hydrocarbon oils from higher boiling point hydrocarbon oils by pyrolytic decomposition, and will be fully understoodfrom the following description illustrated by the accompanying drawing, in which a layout of apparatus suitable for carrying the invention into efl'ect is diagrammatically shown.

Referring more particularly to the drawing, the numeral 5 indicates a furnace setting in 4which are mounted therpreheating coil (i and the heating coil 'i'.,zgthe ormerbeing counected with the latte'rby means of the pipe 8. A. second setting 9 is provided,in which is mounted a digester coil 10, which is connected with the outlet of the heating coil 7 by means of the connecting pipe12. To` the outlet of the digester coil 10 is connected a pipe 13, which may suitably be provided with a gas cushion device 14 to take theshock of variations in the hydraulic pressjuTefr of the oil passing through the system.,

, The pipe 13 discharges into a vaporizing chamber 15, which may suitably be of the form of a horizontal cylinder, although the precise shape employed for this vaporizing chamber or drum is notmaterial. A pressure relief valve 16 is provided in the line 13 before it enters the vaporizing chamber 15, which is maintained at a lower pressure than the heating and digesting coils. The pipe 13 terminates within the drum 15 in a perforated distributing pipe 17, which is well below the liquid level maintained in the drum. Suitable means, such as the ioat indicator 18, are provided for determining the position of the li uid level in the drum.

rom the vaporizing drum 15 vapors pass out through a separator 19 of any suitable t pe, for removing and returning entrained liquid, and through an outlet pipe 20, which leads into the lower portion of a tower 21, which ma suitably be a screen or baffle tower.

Feed stoc or other suitable material may be introduced into the upper portion of the baiile tower 21 through a supply pipe 22, as hereinafter more fully described. Partial condensation takes place in the tower 21, and condensate formed therein, together with the 1924. Serial No. 697,755.

cooling liquid introduced through the pipe 22, is withdrawn from the base of the tower 21 through the outlet pipe 23. A suitable device, such as the float indicator 21", is provided for control of the liquid level in the tower 21. Vapors pass out from the top of the tower 21 through a vapor conduit 24, which leads them into the base of a dephlegmating tower 25, which may suitably be of balile plate or bubble plate type, and in the fractionating tower 25 a further cooling of the vapors takes place, with a formation of condensate. The condensate thus formed is discharged from the base of the dephlegmating column 25 through au outlet pipe 26 into the base of the tower 21, and` is withdrawn from the latter, together with retiux formed therein, through the outlet pipe 23.

From the top of the fractionating column 25 vapors pass through the line 27 into a reflux drum or tower 28, in which they are cooled by indirect heatl exchange with a suitable cooling medium, preferably fresh stock intended for introduction into the system. Any condensate formed in the refiuX drum 28 is discharged through the pipe 25) into the upper portion of the fractionating column 25, through which it descends in countercurrent to the rising vapors. From the top of the reflux drum 28 vapors pass through the vapor line 29 into a vapor heat exchanger 30, from which vapor and condensed liquids pass through a condenser 31. From the condenser 31 condensate and gas pass into a receiving drum 32. This drum is provided with a liquid discharge line 33, in which is placed a meter 34 and a pressure release valve 35. Gas is discharged through the pipe 3G provided with a pressure release valve 37, b v means of which pressure is retained upon the vaporizing and condensing system.

Liquid residue or tar is discharged from the vaporizing drum 15 through a line 38 provided with a pressure release valve 39 into the lower portion of a vaporizing druln 40, this drum being suitably provided with bullies or screens. The tower 40 being at a lower pressure than the drum 15, a further vaporization of the tar takes place, the separated vapors passing out through vapor line 41 into condenser 42. from which the condensate passes to a receiving drum 42S. The pressure tar distillate collected in the receiving drum 43 is discharged through a line 44 in which are provided a meter 45 and ay pressure relief valve lll. Residues are Withdrawn from the tower 4|) through a line -lT provided with a release valve 48.

'["he stof-hv to he treated is brought in through line l0 and is forced through the heating ,system hy the pump 50. liy the pump 5u the stock is forced through a line il to the vapor heat exchanger 3l). from which the partially heated stock passes into the feed line 52. A valved branch line 53 leads from the line 5l to the reflux drum 2S, in which are provided suitable heat exchanger devices, such as the coils .14, through which the feed stock passes to provide the desired cooling effect upon the vapors passing through the drinn. After leaving the reflux drum 2S, the feed stock passes through the pipe 55 into the feed liue 52.

A second valved branch liuc 50 leads from the line 5l to the pipe Q2 by which stock is supplied to the tower Q1 for cooling action therein. A valved line 57 connects this supply pipe Q2 with the feed line 52, and by suitable control of the valves in the lines 5G and 57. the temperature of the feed stock entering the tower Q1 may be controlled. By this means the temperature of the vapors leaving the tower Q1 may be adequately controlled and a direct heat exchange is secured Within the tower, resulting in ay condensation of the heavier or higher boiling portions of vapors passing therethrough, This feed stock is discharged through the pipe 23. together with reflux formed in the tower 2l and in the dephlegmating column 25. The liquids thus discharged through the pipe Q3 are forced by a pump 58. preferably of the surge pump type, through a line 59 into the feed line 52. The feed line 52 is connected with the inlet of the preheating coil 6.

In carrying out the present process, the stock to be treated, which may suitably be a heavy hydrocarbon oil 0f the nature of gas oil or a crude residuum is drawn in from the pipe 49 and forced by the pump 50 under pressure into the line 51 leading to the heat exchanger 30. From the heat exchan er the stock, partly heated therein, passes t rough the line 52 to the preheating coil 6, in which it is preheated to a temperature below cracking temperature by the combustion gases which have already been used to heat the primary heating coil 7 and the digester coil 10. From the preheating coil 6 the oil, suitably heated therein to a temperature of, say, 500 to 600 F., is forced through the pipe 8 into the heating coil 7, in which it is brought to a cracking temperature in excess of 675 F., say 850 to 900 F., While flowing therethrough with a velocity such that substantially no deposit of carbon can take place Within the coil. From the heating coil 7 the hot oil passes through the pipe 12 into the digesting coil 10 in which it is held at substantially the same temperature as that to which it is brought in" the coil 7 by any suitable heating means, a relatively moderate heat being required for this purpose. The oil is caused to travel through the digesting coil 10 at a rate such that substantially no deposition of carbon can talte place, and is maintained therein for a suiiieieut period for a substantial amount of cracking to take place.

The digesting coil has preferably a somewhat larger cross sectional area than the heating coil 7 and is also of somewhat greater length, thereby providing more capacity and longer travel of the oil through the digesting coil than through the heating coil. The rate of travel through both coils is sulieiently high to prevent deposition of colte, and the digesting coil 10 being only mildly heated to maintain a cracking temperature therein. Suitable dimensions for heating and digesting coils in a plant having a capacity of 00 barrels per hour are, respectively 4500 feet of 3 inch pipe and (3000 feet of 4 inch pipe. These dimensions may, of course, be varied within Wide limits.

The oil passes from the coil 10 through the line 13 provided with a gas cushion 14 for suitably cushioning hydraulic shocks in the system, and after passing the pressure release valve 16, enters the vaporizing drum 15. The pressure release valve 1G is so adjusted as to maintain in the heating and digesting coils, a pressure such that the stock is maintained in substantially liquid state until a material amount of conversion has taken place: for example, a pressure of 200 to G00 pounds per square inch may be employed. A suitable pressure with stocks of the character of gas oil has been found to be about 325 pounds per square inch. In the vaporizing drum 15 a pressure above atmospheric is also maintained, the pressure therein being suitably 25 pounds per square inch or higher. Any intermediate pressure between atmospheric and pressure maintained in the heating and digesting coils may be employed. A body of liquid is maintained in the drum 15, and this body of liquid is kept by the incoming hot oil at a temperature of from 10() to 200 below that prevailing at the outlet of the digesting coil; that is, With a temperature of 850 to 900 in the digesting coil, the liquid in the vaporizing drum will have a temperature of about 700 F. The pipe 13 terminates in the drum l5 in a distributing pipe 17 near the bottom of the drum and Well below the surface of the liquid body therein. The release of pressure upon the liquid entering the drum causes a rapid vaporization of a considerable portion thereof, say from 40 to 80%, and the introduction of the oil into the vaporizing drum in this manner causes a violent agitation ot the liquid body therein and causes any coke formed in the oil body to be ke t in suspension therein. The formation o deposits of coke in the vaporizing drum is thereby substantially prevented..

The large amount of vapors evolved in the drum 15 passes out through a separator 19, which removes and returns entrained liquid to the drum, and the vapors then pass through the line 20 into the tower 21, in which they are slightly cooled, partly by radiation from the tower and partly b the introduction into the tower ot' a suita le cooling medium, preferably hydrocarbon oil, such as a part of the stock to be treated. 1n the embodiment of the invention shown in the' drawing, this cooling medium is supplied to the tower through the pipe 22, and may be drawn at will through the pipe 56 from the fresh charging stock line 51 or from the pipe 5T connecting with the charging stock line 52 containing the stock partly heated as it passes through the heat exchanger 30, or partly from both, in accordance with the temperature conditions which it is desired to obtain within the tower 21. The supply of the cooling medium is suitably controlled to bring the temperature of the vapors in the tower 2l to 60() to T00o F. and to thereby remove from the vapors a consider-.dile proportion of the heavier constituents before the vapors pass into the bubble tower or fractionating column 25 in which a more careful fractionation thereof is effected. The reiiux formed in the tower 21, together with the hydrocarbon oil used as a cooling medium therein, pass out through the pipe 23 and are forced by the pump 58 into the charging stock line 52 leading into the coils.

From the tower 21 the vapors, cooled to 600 to T000 F., pass into the fractionating column 25. in which a further cooling talies place. From the column 25 the vapors pass into a reflux drum or condenser 28, where theY are subjected to a controlled cooling by heat exchanger with cold charging stoel( drawn from the line 51 through the valved line 523. The supply of cooled charging stock to the condenser or drum 54 is controlled in accordance with the character of the end product desired, which may suitably be iinished gasoline or, if desired, a somewhat heavier product intended to be subsequently rerun into finished products. Condensatie formed in the condenser or reflux drum 28 returns to the top of the traetionating column 25 through the line Q9 and descends througl'i the column together with any reflux formed therein. The reflux formed in the column 2 and in the drum 28 is drawn off through the line QG. and passes, together with the condensate and coolingl medium from tower 21, to the charging stock line 52 in the manner already described. The vapors from the condenser orreilux drum 28 pass through line 29a and heat exchanger 3() and condenser 31, in which the final distillate product is condensed. From the condenser 31 the distillate product, together with any permanent gas formed in the process, passes into the receiver Distillate may be drawn off from the latter through the line and gas passes ofi" through the line 36, which is provided with a pressure valve 3T which reduces the pressure of the gas to that desired in the line 36, for example, atmospheric or slightly thereabpve- T he valve Si' is employed to maintain the desired pressure in the vaporizing drum 15 and in the overhead system just described.

The residuum or tar in the vaporizing drum 15 passes out through. thc line 38 provided with the pressure release valve 39 into a vaporizing tower 40, which is maintained at a substantially lower pressure, say at atmospheric pressure or slightl thereabove. A pressure slightly in excess ot atmospheric, say 10 to 15 pounds, is preferred, as the use ot' such pressure obviates the necessity o pumping unvaporized liquid from the tower 40. The reduction of pressure on the hot residuum or tar permits of a further vaporiza tion thereof in the tower 40 without the supply of added heat to a bottom of, say, about 10% on the original stock, in which most of the colte formed in the process is accumulated. The vaporized portion passes through a vapor line 41 into the condenser 4Q, and t 1e condensate passes into the drum 43 and may be employed as a part of the charging stock for the system or may be used as a` fuel as desired. The bottom or residuum formed in the tower 4() is forced out through the line 4i', the liquid level in tower 40 being maintained as indicated by lioat indicator 58.

The temperature of the rcsiduum within the tower 40 may be from 40() to 600 F., being substantially below cracking temperature.

le claim:

1. The method of producing low boiling hydrocarbon oils from higher boiling hydrocarbon oils which comprises forcing such oil in a rapid stream through a heating zone maintained at auch a temperature as to bring the ioil to cracking temperature, immediately passing the oil into and through a coniined passage subjected to moderate heat sullicient only to maintain the oil at substantially the same cracking temperature, the rate ot flow of the oil being sutlicient to prevent substantial deposition of coke or carbon. maintaining a pressure upon the oil sutlicient to retain the oil in substantially liquid state until a material amount of decomposition has been ell'ected, introducing the oil products entirely and directly into a chamber at lower pressure, maintaining a liquid body of oil products in said chamber, the point of introduction of heated oil thereinto being below the level of the liquid bod and separating the vapors evolved in said chamber.

i2. The method of producing 10W boiling point hydrocarbon oils from higher boiling point hydrocarbon oils which comprises passing the oil to be treated in a coniined stream through a heatingr zone at a temperature suflieient to bring the oil to eracliing temperature, then passingr the oil in a eoni'ineil stream through a '/.one heated suflieiently to maintain the oil at substantiallyY the saine Cracking temperature, maintainingpressure upon the oil sutiieient to keep the original stock in liquid state under the temperature conditions prevailing, the velocity of the oil in passing through said heated zones being such as to prevent substantial deposition of carbon therein, introducing the heated oil products entirelyY and directly into a body of liquid eran-hed oil products maintained at a lower pressure above atmospheric pressure, whereby a separation of vapors is effected and earbon formed is maintained in suspension in the liquid residuuni in said chamber, and \\ithdrawing liquid residuum from said Chamber.

EDlVARD J. SCI-IAEFFER. EUGENE P. BROVN.

DISCLAIMER 1,851,526.-Edward J. Shaqer and Eugene I. Brown, Whiting, Ind. CnAoKxNG SYSTEM. Patent dated March 29, 1932. Disclaimer Filed April 18, 1936,

by the assignee, Standard Oil Company. Hereby enters this disclaimer to that part of the specification which constitutes claim 1.

[Qfcal Gazette May 12, 1936.]

of the liquid bod and separating the vapors evolved in said chamber.

i2. The method of producing 10W boiling point hydrocarbon oils from higher boiling point hydrocarbon oils which comprises passing the oil to be treated in a coniined stream through a heatingr zone at a temperature suflieient to bring the oil to eracliing temperature, then passingr the oil in a eoni'ineil stream through a '/.one heated suflieiently to maintain the oil at substantiallyY the saine Cracking temperature, maintainingpressure upon the oil sutiieient to keep the original stock in liquid state under the temperature conditions prevailing, the velocity of the oil in passing through said heated zones being such as to prevent substantial deposition of carbon therein, introducing the heated oil products entirelyY and directly into a body of liquid eran-hed oil products maintained at a lower pressure above atmospheric pressure, whereby a separation of vapors is effected and earbon formed is maintained in suspension in the liquid residuuni in said chamber, and \\ithdrawing liquid residuum from said Chamber.

EDlVARD J. SCI-IAEFFER. EUGENE P. BROVN.

DISCLAIMER 1,851,526.-Edward J. Shaqer and Eugene I. Brown, Whiting, Ind. CnAoKxNG SYSTEM. Patent dated March 29, 1932. Disclaimer Filed April 18, 1936,

by the assignee, Standard Oil Company. Hereby enters this disclaimer to that part of the specification which constitutes claim 1.

[Qfcal Gazette May 12, 1936.]

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