US1981572A - Method of heat treating hydrocarbon oil - Google Patents

Description

1934- w. F. SIMS El AL METHOD OF HEAT TREATING HYDROCARBON OIL 3 Sheets-Sheet 1 Filed April 9, 1950 Nov. 20, 1934. w. F. SIMS ET AL 1,931,572

I METHOD OF HEAT TREATING HYDROCARBON OIL Filed April 9, 1930 3 Sheet -Sheet 2 FLASH Nov. 20, 1934.

W. F. SIMS ET AL METHOD OF HEAT TREATING HYDROCARBON OIL Filed April 9, 1930 3 Sheets-Sheet 3 Patented Nov.20, 1934. I 1,981,572

.UNITED STATES PATENT \OFFICE METHOD OF HEAT TREATING' HYDROCARBON OIL Willis F. Sims and Venus U. Cloer, Wichita. Falls,

Tex., assignors to Panhandle Refining Company, Wichita. Falls, Tex., a. corporation. of Texas Application April 9, '1930, Serial No. 442,871

2 Claims. (01. 196-61) Our invention relates to the treatment of hypot if such be employed. As a matter of condrocarbon oils and especially to such treatment venience, we may use for our purpose known, when carried on for the production of motor fuel structures, such for example as that disclosed from petroleum by the process commonly known in U. S. Letters Patent No. 1,732,805, granted as cracking. The present application is closely October 22, 1929, to E. C. DYarmett. As will related to our prior copending applications, Sesufficiently appear hereinafter however, we do rial No. 254,753, filed February 16, 1928, which not use the same type of tube or cooperating has matured into Patent Number 1,948,890, Feb. parts as in that patent, but have specially de- 27, 1934; No. 361,015, filed May 6,1929, which has signed our tube so as to attain our own object.

is matured into Patent Number 1,821,116, Sept. 1, Our invention is illustrated in the accompany- 1924, and No. 409,406 and No. 409,407, filed ing drawings, in which November 23, 1929, which have matured into Fig. 1 is a diagram showing a hot tube use Patent Number 1,930,372, Oct. 10, 1933, and Patinstead of a fiashpot. ent Number 1,918,670 July 18, 1933, respectively; Fig. 2 is a sectional view of a furnace and 15 and the invention described and claimed herein hot tube unit of one type which we may employ is in the nature of an improvementv over the in place of the fiashpot. inventions disclosed in said prior applications. Fig. 3 is a horizontal section on the line 3-3 In the earliest of these applications Serial No. of Fig.2 looking in the direction of the, arrows. 254,753we have described and claimed an im- Fig, 4 is a vertical sectional view of a furnace 20 proved method of cracking under sub-atmosand hot tube of a type we may employ with the pheric pressure or vacuum. In our application, fiashpot.

Serial No. 361,015, we have described and claimed Fig. 5 is a diagrammatic view of the preheater, apparatus to be used in connection with said cracking coil, hot tube, and fiashpot, of the method. In our application, Serial No. 409,406, type shown in Fig. 4.

25 we have claimed particularly the mechanical ar- Referring to the drawings and first to Fig. 1, rangement of the preheating furnace and the 56 is the tubular cracking still, inclosed within a cracking still in one unit. In the last applicafurnace 2, heated by oil burners 62; 57 is the pretion mentioned, No. 409,407, we have described heating coil heated in part by burners 61 and in and claimed the arrangement of the fractionpart by waste gases and products of combustion 30 ators and the absorption tower. Our present inpassing from the furnace 2 through openings 63 'vention has for its object particularly the iininto the preheater chamber 2a and thence into provement'of the preheating and cracking appa the stack 60 through either one or both of the ratus and the method of operating the same. fiues 58 and 59. By adjusting the dampers in' While it is true that a certain amount of crackthe fiues, the amount of heat energy absorbed 35 ing might take place in a fiashpot, nevertheless through the coils 57 may be regulated. 1 we find that by giving a particular design to Charging stock is fed intothe preheater 57 I our fiashpot, or by adding to or substituting for through pipe 53 by a pump 54; and the preheated the same an element provided with supplemental oil passes out through the pipe 52 and through heating and agitating means, the percentage of a branch pipe (both of which are valved, as in- 40 conversion is increased as well as the efficiency dicated at 23 and 38a) to the intake pipe 111 of and rapidity of operation. Accordingly, We atthe hot tube 110. This tube is shown on a larger tain our object by inserting at the preheating scale and in section in Fig. 2. Referring to said' end of the system a tube or pot heated by a furfigure, 111 is the intake, 55 is the output leading nace the q valent, and provided with me to the cracking coil 56 in Fig. 1; 101 isthe fur- 45 chahical meansfor Stirring and agitating the nace, 102 is the stack, 103 is the down draft chamvapors in the pot, while maintaining a layer ber containing the hot tube 110, around which o h Same Of. uniform thickness over the enall the products of combustion and heated gases tire inner surface of the walls thereof. This from/the furnace are compelled to pass before piece of apparatus ay be substituted for the reaching the stack 102. It should be noted that 50 fiashpot, or may supplement the fiashpot, but the stack 102 may be the same in practice as the in any case its output is connected with the stack 60, or they-may be two separate fiues in input of the cracking still and the vacuum or one stack. 1 sub-atmospheric pressure maintained on the 104 is an oil burner in the furnace 101, concracking still is extended back to the hot tube trolled y a Valve 112 is a Central Shaft 5 and .on through the latter to the separate fiasht ndin from d to d o the hot 06 jour- 110 5 shaft 115 driven by a motor 116. The shaft 112 carries paddles or blades 120 extending across the diameter of the tube as shown in Fig. 3 and when rotated by the motor 116 adapted to maintain a rapid, turbulent, swirling motion of all vaporsin the tube, together with a thin film of oil vapors in contact with the inner wall of the tube all around, to receive heat therefrom. The action of these blades is centrifugal and results in every portion of the vapors being uniformly exposed to the heat of the walls. The head of the hot tube is provided with a chamber or trough 117 having a draw-01f tube 118 connected to it and provided with a valve 119. Any liquid which separates out and is not vaporized will be carried to this trough 117 at the top of the tube and will be drawn off through the residue draw-off line 118.

Referring to Figs. 4 and 5 the furnace 101, the cylindrical hot tube 110a, the shaft 112a, stuffing box 113a, and the blades 123, are all the same as previously described. In this form. however, there is no trough at the head of the tube. pors only from either the fiashpot or the vaporizing unit (hot tube or still) enter this cracking tube 110a through the vapor inlet line 121 and pass upward to the vapor line 122,the revolving blades 123 causing a turbulent flow of the vapors.

It will be noted that in the arrangement of Figs. 1 and 2, and also in the arrangement of Figs. 4 and 5, the output of the hot tube, through pipe 55, or pipe 122, is the same, that is to say heated vapors which have been partly cracked. After leaving the hot tube, 110 or 110a, the vapors are passed to the tubular cracking still 56 (Fig. 1) where the cracking is completed, still under a vacuum. Fromthe cracking still 56, the cracked vapors are carried through a plurality of fractionators 6, '7, 8 and an absorption tower 11, the

condensed oils from the fractionators passing to a suitable separator 10 and receiver, while the lighter vapors carried off with heavier fractions are recovered in the absorption tower 11 and returned to the last fractionator 8 to be therein released, and condensed, and passed to the separator 10. In the top of each fractionator is a heat exchanger 28, 27, or 26. Make-up oil, combined with uncracked heavier fractions, is pumped back through these heat exchangers in series, abstracting heat from the vapors in the respective fracpels them, until they are released into the flashpot as controlled by a valve 38 thereat.

The hot tube 1100; is preferably vertical, and contains an axial shaft 112a rotated by external power, and carries radial blades 123 extending across the internal diameter of the tube, which are constantly rotated, causing a turbulent flow of vapors and therefore a high heat transfer to vapors being cracked. After being thus expanded into vapors and partially cracked, in the hot tube as such, these vapors pass to the cracking coil While it is truethat a certain percentage of cracking occurs whenever oils are heated, it is a o true that the product is both uncertain and unsatisfactory unless the conditions are fixed, and particularly the amount of heat energy communicated .to each part of the body of 011 under treatment, which should be uniform, and the pressure thereon. The peculiar virtue of a hot tube of the type described, with rotary paddles,

is that instead of massing the oil in a body requiring deep penetration of the heat waves, whereby uniform heating is of course impossible, we can form a thin film around the inside of the hot tube which is easily and'uniformly penetrable by the heat energy communicated through the walls of the tube while at the same time, owing to the motion of the paddles, the vapors passin through are in a turbulent state of flow, and therefore in the best condition to absorb heat as they are brought into contact with the tube walls. This much of itself however would not be sufficient for our purpose,inasmuch as the vapors initially produced in our system are supposed to contain all the fractions of the charging or makeup oil flashed into vapor simultaneously. The characteristic featureof our system by which We accomplishthis is to preheat them under pressure, as already stated, and then admit them to the expansion chamber, which in this case is the hot tube, and thence to the cracking still, under a vacuum.

As an alternative to the foregoing, and in order .fiashpot and then passed to the inlet of the hot tube as vapors, whereby the percentage of unsats urates and aromatic compounds is increased. The purpose in mind in designing this entire system has been to produce one hundred percent of cracked products as unsaturates and aromatics, or in other words high grade motor fuel.

The vapors from the hot tube are drawn through the cracking tube 56 preferably at a temperature of 1000" F. to 1200 F., and a pressure of 6 to 14 pounds absolute is maintained on said tubes by the vacuum pump 14. This low pressure affects also the hot tube, and lowers the temperature at which the cracking reaction takes place. It also accelerates the velocity of the vapors, considering a constant gallonage of raw oil charged, as compared with a system operated at. or above atmospheric pressure. This effect extends also back to the hot tube 110a, wherein a double effect is produced by the blades 123 and the low pressure combined. The resultant effect is to speed up the operation of cracking beyond what has heretofore been possible since the vacuum pull on the hot tube 110a and the tubes 56, causes a rapid flow of vapor through them, while the paddles 123 in the hot tube by forcing the vapors against the tube walls, keep up the temperature of the vapors and prevent the loss which would otherwise occur due to too rapid travel of the vapors through the system. Thus the result produced by our combination is more than the sum of the separate results of the use of a hot tube and the maintenance of a sub-atmospheric pressure taken Separately. We have discovered that by maintaining a vacuum in the vapor phase we can advantageously increase travel, and by providing means to supply more heat, or to expose more vapors in their travel to the heat, we can not'only maintain the speed of travel, but also maintain or increase the rate of conversion per unit of time or per unit of travel, or both. If the tube 110a had sumcient capacity, or if a battery of said tubes be employed, the cracking tube 56 might be dispensed with without altering the principle involved or the improved result attained, which is due to the combination of more eflicient heating with the low pressure and increased travel.

The vacuum pump 14 is located at such a position, with suitable connection lines 30, 39, 40, 42, and valves 3, 4, 5, 19, 46, 20, 21, and 25, that the vacuum may be applied at the discharge from the tubes in the heating zone 2, afterward pumpin the vapors so. removed from the tubesto cooling and separation tower 6, or the vacuum may be applied on the separator drum and the vapors so removed may be discharged into the a bsorp--v tion tower 11.

The vapors entering the cooling and separation tower 6 may be at or below atmospheric pressure, depending on the point at which the vacuum is applied to the system, and will be at an elevated temperature, preferably from 1000 F. to 1200 F., depending on the temperature found most suitable to give the largest practical yield of gasoline or related light oils. Because of this elevated temperature of these vapors they contain considerable quantities of heat that must be removed before the products of the reaction produced in the tubes can be condensed and made stable under atmospheric conditions. This heat is removedin two ways; 1) by causing the hot vapors to come in contact with a downward flow of liquid oil. drawn from the bottom of cooling and separation tower '7 by pump 13, and discharged through valve 18 to tower, 6, preferably contacted with the hot vapors over a series of battle plates placed in this tower; .and (2) by causing the vapors to come in contact with heat exchanging coils26 placed in this tower, through which oil of relatively lower temperature than the vapors is caused to flow by pump 15. This causes the heat to be utilized (1) in vaporizing the incoming oil from tower 7. and (2) in the absorption of the heat by the cooler oil flowing in the cooling coils. This cooling effect will cause a heavy residue to collect in the bottom of the cooling and separation tower 6 which is removed from the system by pump 12.

The vapors from tower 6 enter the tower 7. at or below atmospheric pressure dependin on the point at which vacuum is placed on the system and in tower '7 they are further cooled and fractionated. This tower is preferably of the bubble type. The cooling is efiected by causing the vapors to come into contact with heat exchanging coils 2'7. through which oil of relatively lower temperature than the vapors entering the tower is caused to flow by pump 15. The cooling in this tower is carried to such a point that a large portion of the vapors entering it are caused to condense to liquid. This liquid is drawn from tower '7 by pump 13 which discharges a part of it into tower 6 at 18 and a part through the coils,

26. Valves 18 and 47 are so located onthe discharge line from pump 13 that all or any part of the liquid from the bottom of the cooling and separating tower '7 may be caused todischarge into either the tower 6 or the coils 26.

The vapors from the tower 7 enter another tower 8 at or below atmospheric pressure depending on the point at-which the vacuum is applied to the system, and in tower 8 they are further cooled and fractionated. This tower is preferably of the bubble type. Cooling is effected by causing the vapors to come in contact with the coil 28 through which oil at a lower temperature than the vapors is caused to flow by pump 15. This cooling allows a considerable portion of the vapors to be condensed and the condensed fractions are removed from the bottom of the tower through the heat exchanger 17 by the pump 15.

A part of the oil, after having been cooled by passing through the heat exchanger 17, is discharged by pump through valve 31 into the absorption tower 11, and a part of the oil is discharged through coils 28 and 27, through valve 32. Valves ill-and 32 may be so opened or closed as to cause a desired quantity or all to fiow in either direction; v r

The vapors in the tower 8 are also cooled by the liquid from the bottom of the absorption tower 11 which is pumped from tower 11 by pump 16 through heat exchanger 17 where the temperature of this liquid is raised by liquid flowing ina counter current from the bottom. of tower 8, and it is then discharged into tower 8 through valve 33. The temperature of the liquid entering tower 8 may be controlled by by-passing the heat exchanger with a portion of the cold liquid from absorber 11. This by-pass may be of any suitable or desired construction, and is shown at a: in the drawings. The liquid from absorber 11 contains the very light fractions not condensed by water'cooling coil 9. These absorbed light fractions are removed from this liquid on its entrance into tower 8"due to the heat it gains in heat exchanger 17*and the hot vapors entering tower 8.

The vapors from the tower 8 are caused to pass through water cooling coil 9 where they are condensed at atmospheric pressure or lower depending on the point at which the vacuum is applied tothe system. This condensate, because of the cooling and separation it has previously had, is

gasoline or related light oils and is collected in separator drum 10. This light liquid is removed from the separator drum 10 .through valve 29 by a pump not shown in the drawings.

The vapors that collect in separating drum 10 are either drawn from it by vacuum pump 14 or are caused to pass into absorbing tower 11 by reason of their own pressure. This also depends on the point at which the vacuum is applied to the system. These vapors flow in a counter-current to the cooled liquid from the bottom of the tower 8 and the lighter gasoline or related lighter oils are absorbed in this liquid. The tower 11 ispreferably of the bubble type.

The fixed gases pass from the tower 11 through I line 4'7 to the atmosphere, or to burners under the furnace, or to commercial gas lines.

The bottoms from tower 8, either with or without make-up oil, delivered through line 34 and valve 35, not required as absorption oil in the tower 11, are returned to the system and used as cooling oil in coils 28, 27,. and 26. The line conducting this oil to coils 28 and 27 has valves 36 and 37 so situated that all or any part of this liquid can be caused to flow through them.

The heated liquid from coils 26 is conducted through line 22 and through valves 38 and 38' to the hot tube 110 or the flashpot as the case may be, and the vapor so produced is retreated in the tubes 56 placed in this furnace.

We have not deemed it necessary in adapting the additional element of a hot tube to our system, to vary the type of fractionating, separating, and absorption apparatus employed in our previous systems. The only differences in the sys- 'tem 'of Fig. 1, from the cracking still 56 onward,

are those which naturally occur in operation or adjustment when the rate of conversion is higher and the'initial heating operation more efiiciently and perfectly performed. The adjustment of the valves throughout the system will be'afiecte'd, be-

cause there will be less of the heavy fractions to reflux and recrack, there will be a higher percentage of the desired motor fuel in the first run-off, and particularly the percentage of unsaturated and aromatic compounds passing from the separator will be increased and under favorable conditions may reach practically 100%; .It

will be understood of' course that this does not mean 100% of the raw oils, by 100% of the cracked product. initially charged which will be ultimatelyde- The percentage of the raw oil livered as motor fuel will vary, o1 course,'ac-

, cording to the character of the oil used. How- .ment in every respect by the use of the process and apparatus described'herein, and particularly I ever, we can show a very substantial improvethe percentage of conversion, and ter 'of the cracked products.

What we claim is: 1. The method of heat treating hydrocarbon oils and of producing motor fuel therefrom, which consists in heating the oils under pressure to the characdistillation temperatures, passing a stream of the oils into a circular flash-vessel under sub-atmospheric pressure, rotating the vapor and residual i oils therein at a speed suflicient to confine substantially the entire oil content 'of the vessel to a film of oil on the inner surface of the vessel and to maintain the oil vapors in said vessel, heating said film to a high temperature through the walls of said vessel at sub-atmospheric pressure, an continuously collecting and drawing off the heated vapors from said vessel under asub-atmos-v pheric pressure or vacuum, super-heating said vapors in a cracking zone at sub-atmospheric pressure separated from the flash-vessel .to com-' plete the cracking operation, and finally fractionating and condensing the same. 1

'2. The methodof heat treating hydrocarbon oil whichconsists in heating the oil to distillation temperatures, flashing said oil into vapors in a flashing zone-at sub-atmospheric pressure, separating unvaporized liquid oil from the vapors in the flashing zone without cooling, and reheating the separated liquid oil in the flashing zone, taking 01f the vapors under sub-atmospheric pressure, removing unvaporized oil and

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