US2003724A - Apparatus for the treatment of hydrocarbon oils - Google Patents

Description

June 4, i935.. w. F. sims Er AL. 2,003,724

TUS FOR. THE TREATMENT OF HYDROCARBON OLS APPARA Filed MarCh 4, 1951 3 Sheets-Sheet l NS @N gva/vanto@ Jun@ 4, 1935. w. F. slMs ET AL v APPARATUS FOR THE TREATMENT OF HYDROCARBON OILS Filed March 4, 1931 Maa/a5 3 Sheets-Sheet 2 Jun@ 4, w35. W, FSW ET M www APPARATUS FOR THE TREATMENT OF HYDROCARBON OILS Filed March 4, 1931 3 Sheets-Sheet 3 Patented June 4, 1935 UNITED STATESl APPARATUS .Fon THE TREATMENT F HYDROCARBON oILs Willis F. Sims and Venus U. Cloer, Wichita Falls;

Tex., assignors to Panhandle Rening Company, Wichita Falls, Tex., a corporation of Texas Application March 4, 1931, Serial No. 520,074

2 Claims.

Our invention relates to the treatment of hydrocarbon oils and especially to'apparatus adapted to produce motor fuel from petroleum by the process commonly known as cracking. The pres- 5 ent application is a continuation in part of each of our prior copending applications Serial No. 254,753, led February 16, 1928; Serial No. 361,- 015, led May 7, 1929, which has matured into Patent No. 1,821,116 and SerialNo. 442,871, filed mi, April 9, 1930. In these prior applications We have described and claimed an improved method of cracking under sub-atmospheric pressure, a com.- plcte plant for practicing the same, and an improved heater particularly adapted for use in our cracking still. In the present case we shall describe the same general system, comprising among other pieces of apparatus the following: a preheater operating preferably under pressure; a flashpot into which the heated oils are admitted and iiashed into vapors; a cracking still receiving the vapors from the flashpot, and heating the same to a high temperature; a vapor pump or equivalent suction means withdrawing the vapors from the cracking still so as to maintain subatmospheric pressure therein and through the open connection of said still with said ilashpot, alsomaintaining a sub-atmospheric pressure on said ashpot; means connecting the output side of said Vapor pump or equivalent with fractionating apparatus,` and therethrough with cooler and separator and/ or other desirable or necessary pieces of apparatus. In our prior application Serial No. 351,015, we have claimed means for maintaining a constant Vacuum or sub-atmospheric pressure on the cracking still and the flashpot in combination with means for relluxingand reheating condensed oils and passing the same back under pressure to the liashpot; also the same elements in combination with heat exchangers in the several fractionating units; also the same including a vacuum pump connected to produce a sub-atmospheric pressure on the entire system from the cooler back to the cracking heater.

In the present case, we shall describe and claim that specific form of the invention in which the pump which creates the vacuum or sub-atmospheric pressure on the cracking coil has its outlet directly connected to the first dephlegmator or fractionator, whereby only the flashpot and cracking coil are under a sub-atmospheric pressure and the rest of the system operates above atmospheric pressure. In addition `to this, we shall claim broadly herein the combination of primary heating means, a flashpot, cracking still, cooling` and separating ,means and means to create and maintain a sub-atmospheric pressure on the cracking coil.

Our apparatus, as it will be described herein, comprises a charging pump, for putting in the chargingrstock, a flashpot, a cracking. still, a

succession of interrelated fractionating ftowers or dephlegmators with necessary pumps,- heat exchangers, ccoler and separator, and finally means for feeding make-up oil into the system andback through heat exchangers to the ashpot, under pressure. This will be described in combination with refluxing heavy condensates, but the same will not be claimed herein, being claimed incombination with the other features in the parent application, Serial No. 361,015. In addition tothe regulation of pressure in the flashpot and crack-v ingst-ill, we have found it possible to arrange a graduated heat transfer by means of Vwhich the make-up oil or reiiux fractions to be cracked, take up practically all the heat energy in the crackedA vapors, in a counter progression to the fraction.- ator. The make-up oil and reflux fractions instead of going direct to the cracking still, have their temperature raised so that they can vbe con. verted into vapors in the ilashpot; and by com-v plementary regulation of the charging oil on the one hand and the make-up oil on the other, the quantity, the temperature, and the pressure of the hot oil admittedvto the flashpot can be regulated to a nicety, with a minimum consumption of fuel in the primary heater Asince a large part of 'the heat ordinarily lost in the fractionating and cooling system is conserved in our system.

By maintaining a vacuum or a 4sub-atmospheric pressure in the cracking zoneand flashpot, cracking commences at a lower temperature, while the raising of the temperature, Vtogether with the turbulent and rapid motion ofthe vapors through the cracking tubes due to the pull'of the vacuum, causes a considerable increase inthe amount of heat energy taken up per square Vfoot of surface, With a corresponding increase inthe amount of cracked products. Without limiting ourselves to one specific set of pressures, we have found in actual practice that suitable pressures for our system and our method are from 15 to 175 pounds absolute on the primary heating still, from 12 to-14 pounds absolute on the ashpotfand from G to i4 pounds absolute (or a higher vacuum) on our cracking zone. Itis to be understood that the word vacuum as used-n this specification means therefore any pressure below that of the atmosphere, but the actual pressures employed will be'stated in pounds absolute.

Our invention is illustrated in the accompany ing drawings, in which Fig. l is a diagrammatic side elevation with parts in section showing the general arrangement of our apparatus.

Fig. 2 is a similar view of a modicationshowing a different form of preheater. K

Figi 3 is a similar diagram of vtheinitial-heat ing and cracking portion of the systemJ showing a `modified arrangement in which the preheater of Fig. 2 is placed intandem with the'ordlnary` Referring to the drawings and first to Figf l, the principal pieces of apparatuslemployed in this system are the preheater 51, the iiashpotA I, the cracking still 55, the dephleginators orfractionators 6, 1, 8, and the suction pump VI-'l connected between the cracking coil 55 andthe dephlegmator tower 8. Much of the detail in these drawings will not be claimed herein, as it forms the subject matter of claims in prior copending applications, but the complete system will be briefly` described and its operation stated, in order to furnish a proper and complete foundation for the claims herein, which will be directed to the combination of the essential features above stated, with particular reference to the location of vthe pump M between the cracking still and the dephlegmators or fraotionators, so as to maintain a sub-atmospheric pressure on the cracking still and the flashpot, and an atmospheric or super-atmospheric pressure on the rest ofthe system extending forwardly from pump I4 to thecoil 9 and the separator ID and backwardly from pump I5 for reflux fractions through heat exchangers 28-21-26 and the pipe 22 to the flashpot.

Each of the pumps I2, I3, I4, I5, I5 is supposed to be driven by a suitable source of power. Each of the dephlegmators may be of the bubble tower type as shown at 1 8, or of the bafe plate'type as'shown in 5. From the top of each tower a goose neck extends down to below the middle of the next succeeding tower and from the top of the last tower 8 to the cooler or condenser 9 and separator Iii.` From the latter a valved pipe 29 carries off the condensate and the pipe 30 draws off uncondensed gases. Each of the towers contains in its top a heat exchanger 25, 21, or 28, whose area and capacity is increased in the direction of ow, to provide for the rising temperature of the refiux oils. The inlet of the first of these heat exchangers 28 is connected through the valved pipe 32 to the outlet of the pump I5,l with valved branch SI to the top of the absorbing tower I I, and to a source of supply of make-up oil, the flow from which is regulated by valve 55.Y From the outlet end of the heat exchanger 25, the pipe 22 extends to the flashpot I direct, without going to the preheater 51. ChargingV stock is fed into the preheater under pressure by thev pump 54 and in order to build up pressure and accumulate thermal units in the coil 51, the valve 23 is provided which in operation is complementary to the valves 35 and 38. Means are provided to regulate the heating of the reflux fractions in the heat exchangers 21, 28. These are shown in the drawings as by-passes controlled by valves 36, 31, which like the other valves described can be set at anything from closed to open.

The function of the pump I2 is to draw off the heavy precipitate or tarry matters from the bottom of tower 6; the function of pump I3 is to .draw voff heavy gas oil which is thrown down in the bottom of tower 1 and return the same in part through valve I8 to the middle section of tower 5 'and inlpart through valve 41 to the heat exchanger 25 as reflux to be retreated. The function of pump I4 is to produce suction through the 'vali/e4 0n the outlet of the cracking still 55, and conversely to build up ahead of it through pipe 39and valve 5 a constant positive pressure, that is to say, a pressure at or above atmospheric, in the towers B-1. The function of the pump I5 is to withdraw light gas oil from the bottom of tower 8, drawing it through the heat exchanger I1 and discharging it either in whole or in part through the valved branch SI into the upper part of absorption tower II, -or in whole or in part through the valved branch 32, into the heat ex- Achangers 28-21-25 Y rlhe portion discharged through the Valve 3i into the tower II has for its function the absorption of gasoline-like fractions which have become entrained with the fixed gases. These gases flow through the pipe 30 under their own pressure and are discharged through the valve 25 and the pipe I2 into the lower part of the tower il. The entrained gasoline-like material is stripped from them and absorbed by the oil entering the head of the tower through the valve 3i. This tower as well as the towers 1 8 is shown as a bubble tower, but it is to be understood that any preferred form of tower may be employed which will aiord a larger superficial area over which gases passing in one direction and the oil passing in the other may come into contact.

The pipe shown leading from the pump I5 vertically to the valves SII- 32 is also provided with a horizontal branch 34 through which make-up oil is supplied to the system. This make-up oil as its name indicates, is to supply in part or in whole,` the losses due to conversion, condensation, and removal from the'system through the cooler S andthe separator i5, or otherwise. Since this make-up oil may be in part used through the Valve 3| as an absorbing agent in the tower I I, for which purpose light gas oil is also drawn by pump I5 through the heat exchanger I1 from the bottom of tower 8, obviously the make-up oil to cover this purpose may be gas oil.

The operation of the system thus described is as follows: charging stock is pumped into the primary heater 51 by pump 54 and is heated in the furnace 2a to a temperature higher than that required forvaporization at the pressure maintained in the ashpot, or in other words, the charging oil is heated under pressure. It is then admitted through valve 23 to the flashpot wherein it instantly passes in the vapor phase. In this form it is drawn in a turbulent, rapidly moving body through the cracking coil 55 into and through the pump Id and so into the tower 6 through the valved pipe 5. In this tower the first separation takes place, the vapors as they rise meeting the gas oil entering the tower through valve I8 and also encountering the surfaces of the heat exchanger 25. The result is a deposit of heavy fractions or a tarry mixture which is removed from the system by the pump I2. The heavy gas oil admitted through the valve I8 dilutes this tarry mixture so as to prevent the deposit of any dried coke or the burning on of coke or tar in the tower.

The vapors thus initially cleansed pass over the rst goose neck into the lower part of the second tower 1 and rise up through the bubble pans and through the reticulations of the heat exchanger 21. There is thrown down in this tower (assuming the crude to be of'average formula) heavy gas oil, which is drawn oi by the pump I3 and carried back to the tower 6 as above stated. The vapors, having given up more heat through the heat exchanger 21, pass through the' second goose neck to the lower part of the third tower 8 through which they bubble up as before and in addition to the bubble pans, they pass through the reticulations of the heat exchanger 28. The condensate in this case is a light gas oil, and the vapors remaining go over through the top of the tower and the third goose neck to the cooler 9 wherein condensable portions are condensed and pass to the separator IB. Valved pipe 29 leads from this separator III to storage, while the pipe 3B goes to the tower II, carrying xed gases with entrained gasoline-like material. These gases ow back under their own pressure through valve 25 into pipe 42 to the lower part of tower II, as indicated by the arrows. In this tower as already stated make-up oil and/or light gas oil drawn from the bottom of tower 8 through heat exchanger I1 are or is fed into the upper part of the tower I I through the valve 3l and meeting the uprising xed gases, absorbs the gasoline carried thereby and carries the same down with it to the bottom of the tower II from whence it is drawn off by pump I6 and forced back through the heat exchanger I1 and the valve 33 into the tower 8. Becoming heated and vaporized in this path, the gasoline rises, goes over the top to the goose neck, and is condensed in the cooler 9 and passes through the separator I to the storage tank. The fixed gases in tower II pass out of the top thereof through the waste pipe 48.

It is obvious that it is possible to adjust the valve 35 and the valve 32 or the Valves of the pump 54 typified at 545 so that the charging stock and the make-up oil will be fed in in complementary quantities and so as to maintain complementary or average temperatures and pressures in the pipes 22 and 52 leading to the flashpot. The Valves 23 and 38 materially assist in this adjustment, so as to produce uniform average temperature and pressure at the flashpot, whether the input is fresh charging stock, or whether it is make-up oil or reflux fractions drawn from the tower 8 by pump I5, or make-up oil entering the system through pipe 34.

Referring now to Figs. 2 and 3, I have therein shown a modification of the preheating apparatus and the cracking apparatus of the type described and illustrated in my prior application, Serial No. 442,871. In Fig. 2, the preheater 51 and the cracking coil 55 are installed the same as before, but between these two in respect to the flow of oil, and taking the place of the fiashpot, I provide a cracking tube III! constructed as described in U. S. Letters Patent 1,723,805, granted October 22, 1929 to E. C. DYarmett. In Fig. 3, the same type of cracking tube IIS is inserted between the flashpot I and the cracking coil 56. in either case, the tube I I0 contains a set of vertical paddles or blades projecting radially in the tube from a central shaft coaxial therewith, which shaft carrying the paddles is rotated by a motor H at such speed that the oil, is spread around the inside surface of the tube as a film by centrifugal force. The shaft is journalled at top and bottom of the tube III! as indicated at IIDa and IIDb. In the form illustrated in Fig. 2, charging oil after leaving the pump passes through the coil 51 and pipe 52 to the bottom end of the tube IIS, into which it is expanded by manipulation of the valve 38a. Reflux oil and make-up oil coming through the heat exchangers 25, 21, 28 and the pipe 22 follows the same path through theyalve 38a to the lower end of the tube I In and is flashed therein into vapors. Sufcient temperature is maintained in the furnace IBI to produce cracking in the film of oil around the inside of the tube IIO, and the partially cracked vapors then pass through the outlet pipe 55 to the still 56 which in this case performs the function of a supercracker. The pump I4 maintains sub-atmospheric pressure on this crackingA still 56 and therethrough and through the pipe 55 also on the tube I I0, which performs the functions of the flashpot in Fig. l in addition to assisting in cracking the vapors.

In Fig. 3, the iiashpot I is retained, and the heated charging stock pumped in from 54 through the pipe Y53 and the preheater 51, reaches the flashpot I through the pipe 52 as in Fig. 1. Heated reiiux fractions and make-up oil are also brought over through the pipe 22 to the ashpot I as Fig. 1. From the iiashpot, instead of carrying the outlet direct to the cracking coil 55, the discharge pipe I2I is carried to the lower end of the tube I I 9, from the top of which pipe 55 goes to the cracking coil 55. The tube I I0 is set in the furnace il and its internal paddles are rotated by the motor H5 so as to maintain a film of oil vapors around the inside of the tube. Heat conducted through the walls of the tube acts very eiciently upon this film which is constantly changing and very turbulent, owing to the vacuum or subatmospheric pressure produced by the pump I4 shown at the right of the figure. In this case the coil 56 acts as a super-cracker, since part of the cracking in the vapor phase and under subatmospheric pressure takes place in the tube IIO. The action of the pump I4 is the same in each case however, viz., to create and maintain a partial vacuum or subatmospheric pressure from its inlet back to the point where the vapors are ashed, and to create and maintain a positive pressure from its outlet side through the fractionators. It may be noted that all deposits from the flashpot and in the pipe I2I, and the tube I I D may be drained off through the pipe 240 which is valved at 24.

What we claim is:

1. Apparatus for the treatment of hydrocarbon oils comprising in combination an initial heater adapted to retain pressure, a feed pump connected to the inlet of said heater and adapted to positively produce pressure therein sufficient to store up heat energy by substantially raising the boiling points of the oils, an expansion chamber or flashpot, a connecting pipe extending from the outlet of said initial heater to said flashpot and a valve in said pipe adapted to release the initially heated oils from said heater into said expansion chamber or ashpot, a still having an open connection to said iiashpot adapted to receive the oil vapors therefrom, and means to heat the oils to cracking temperature in the vapor phase in said still, cooling and separating means connected through a suitable pipe line to the outlet of said cracking still to receive the cracked vapors therefrom, and a pump connected in said pipe line and adapted to positively create and maintain a constant vacuum or subatmospheric pressure on the oil vapors in said cracking still and through its open connection with the ashpot on the content of said flashpot.

2. The combination described in claim 1, in which the pump connected in the pipe line between the cracking still and the cooling and separating means is adapted to positively create and to maintain a positive pressure above atmospheric on the cracked vapors in said cooling and separating means.

WILLIS F. SIMS. VENUS U. CLOER.

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