US1874861A - Treating hydrocarbon oils - Google Patents

Description

Aug. 30, 1932. o. BEHIMER TREATING HYDROCARBON OILS Filed May 18 '1.927

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Patented Aug. 30, 1932 UNITED STATES PATENT oFF-ICE OTTO BEHIMER, OF PORT ARTHUR, TEXAS, ASSIGNOB TOTHE TEXAS COMPANY, OF NEW YRX,1N. Y., A CORPORATION OF DELAWARE TBEATING HYDROCARBON OILS Application led May 18, 1927. Serial No. 192,228.

This invention relates to the pressure distillation of hydrocarbon oils and pertains more particularly to certain novel methods of treating the evolved vapors from pressure cracking stills to eli'ect the separation of the vapors into liquid lcondensates.

It has been a problem to properly handle the vapors from pressure stills. If the vapors are fractionated or condensed under still pressure, the gasoline or other light distillate obtained will contain considerable proportions of fixed or permanent gases held"in solution in the liquid under the pressure employed and when the pressure is subsequently reduced as the gasoline is handled in storage and transportation, the gases are released from the liquid, carrying with them large quantities ofthe liquid. On the other hand, if the pressure be reduced and the vapors from the still lsubjected to fractionation or condensation at atmosphericl pressure or l thereabouts, although the liquid condensate obtained may contain a minimum of xed gases, there is a great loss of liquid constituents due to the carrying eifect ofthe permanent gases released at the low pressure. My invention seeks to avoid these disadvantages by providing certain novel methods of treating the pressure still vapo'rs so :o as to prevent or reduce to a minimum the loss of liquid constituents in the exit gases from the system and at the same time produce a stable distillate, that is a distillate which is capablf` of'being handled under $5 the ordinary conditions of storage or transportation without the losses that ordinarily attend the handling of cracked distillates.

My invention contemplates a process wherein the vaporsA from a pressure still are t0 first subjected to a separation under high pressure, such as the pressure of the still, and a distillate obtained from this first separation is then rectified or fractionated under reduced pressure. In accordance with my invention the vapors are taken olf the pressure still and subjected to condensation, dephlegmation or fractionation under a ressure preferably approxi ating that o the still, the vapor product ob ained in this Se al0 ration cooled to form a condensate and t is condensate rectied or fractionated under reduced pressure.

The invention also has in view a process wherein hydrocarbon oils are subjected to cracking temperatures under superatmospheric pressure to eect a conversion of higher boiling into lower boiling hydrocarbons, and the evolved vapors are removed froin the cracking zone and subjected to a separation, as by condensation or fractionation, to produce a vapor fraction and a liquidfraction, the latter of which is returned to the cracking zone for retreatment while the vapor fraction is cooled to form a condensate and the` condensate fractionated or rectified under reduced pressure to form the gasoline or other light distillate desired.

In order to more fully describe the invention, reference will now be had to the accompanying drawing which is a diagrammatic sectional elevationillustrating a particular embodiment of the invention. In the drawing a cracking apparatus is shown consistmg of a heating coil 10 and a pressure still 11. The coil 10 is disposed in a furnace 12 and the still 11 is insulated to .preventloss of heat or mounted in a suitable furnace ,(not shown). A `pump 13 is provided to introduce charging stock through a line 14 to the coil 10 and a transfer line 15 is provided to conduct the heated oil from the coil 10 to the still 1,1. The still 11 is provided with a .residue or tar line 16 anda vapor line 17.

The vapor line communicates with a fractionating or rectifying column 18 which is shown equipped with a reflux condenser 19 connected to the column by a vapor line 20 and a reux condensate line 21. The column 18 is equipped with a pipe 22 for removing the liquid fraction. The pipe 22 has branch lines 23 and 24, the former ofwhich serves to withdraw the liquid from the system in `case it is desired to do sov and the latter of which is connected to the inlet of a pump 25, which pump is adapted to force the liquid withdrawn from the fractionati'n column through a line 26 and thence into t e coil`10. A vapor line 27 extends to a condenser coil l2?) illustrated as being positioned in a 'water-4 The condenser coil is provided with 10 I an outlet pipe 30. Pressure reducing valves 31 and 32 are shown in the pipes 27 and 30 respectively. The pipe 30 has two branches,

` 33 and 34, the former of which extends to a element 38 of a heat exchanger and a pipe 39 extends from the heat exchange element 38 to a rectifying or fraetionating column 40, the pipe 39 having a plurality of branch lines 41 communicating With the "column 40 at distributed points. The rectifying column is shown equipped with a lrefiux condenser 42 to'whih it is connected by a vapor line 43 and reflux condensate line 44. It is to be understood that both the reiux condensers 42 and 19 are adjuncts of the -fractionating towers 40 and 18v respectively, and serve to supply the desired cooling to the towers, and that the refiux condensers as separate elements may, if desired, be omitted and the cooling supplied by cooling means in the top of the towers 18 or 40. A pipe 45 serves to conduct gas to suitable storage or to compression or absorption apparatus shown). The column is provided with a heating coil 46 and a condensate outlet pipe 47 having branch lines 48 and 49. The pipe 48 connects with a heat exchange element 50 in heat exchange with the element 38 previously mentioned and a pipe 51 serves to withdraw liquid from the heat exchange element 50. A by-pass line 52'connects the pipe 34 directly with the pipe 39 so that if desired the heat exchanger may be by-passed and llquid passed directly from the pipe 34 to the plpe 39 and thence into therectifying column 40. It will be seen that in the arrangement lllustrated the distillate in the coil 28 may be passed into the receiving drum 35 and thence into the rectifying or ractionating chamber 40 or it may be passed directly intow the rectifying column 40 Without having been collected in the receiving drum 35 and in either case the heat exchanger consisting of members 38 and 450 may be used or'byrpassed, as may be desired. o

In practicing the invention with the apparatus thus illustrated, the charging stock after having been pre-heated, if desired, by heat exchange with hot vapors or liquids from the system or by any other suitable means, 1s fed into the pipe 10 wherein the oil 1s heated` to a cracking temperature. The heated o1l is thenvpassed into the cracking still 11 where cracking and distillation occur. The vapors pass to the column 18 wherein they are (subjected to rectification, or fractlonatlon to form a liquid fraction and a vapor fraction. The liquid may be removed through the pipe 22l and introduced into the heating coil 10 or returned to the cracking zone for req-treatment or if desired the liquid may be wlthdrawn through the pipe 23 and (not erated, for example, under higher temperatures and pressures than that obtaining inl coil 10 and still 11.` A properlyregulated i amount of cooling is supplied by means of the reflux condenser 19 so that a vapor fraction of desired characteristics is taken off through the pipe 27. The rectifying operation carried on in the chamber 18 is conducted undcr superatinospheric pressure; this pressure may if desired be reduced somewhat from that obtaining in the cracking still 11. I prefer, however, to have no material drop in pressure between the cracking still and the primary rectifying column 18 or in other Words, to carry on this fractionation under substantially still pressure.

The vapors removed from the ractionating apparatus through the line 27 are conducted into the condenser 28 to thereby produce a distillate which is withdrawn through the pipe 30. While the pressure reducing valve f 3l may be employed to reduce the pressure in the condenser coil 28, in the preferred operation this valve is not employed for this purpose, and the still 11, rectifying apparatus 18 and condenser28 are all held under substantially the same pressure. The pressure on the distillate is then reduced by means of the valve 32as the distillate is discharged through the pipe 30. When the receiving drum 35 is employed, it is best to have a 'material drop in pressure through the valve l32 and thus collect the distillate inthe recase the valve in the pipe 37 serves to effect a further reduction in pressure under which the rectification in the'column 40 4is conducted; in other words, the pressure on the distillate is stepped down, the distillate being collected under reduced pressure in the receiving drum 35 and rectification being carriedon in the column 40 under a still further reducedpressure. If it is not desired to use the receiving drum 35, the pressure on the distillate is reduced by the valve 32 and the distillate is directed vinto the line 34 and thus passed to the rectifying column 40.

The reiux condenser 42 is supplied with a regulated amount of cooling so as t6 insure lbe used to heat the bottom of the column so as to supply adequate heating for rectification. The heated liquid collected in the bottom of the vcolumn may be passed to the heat `fore being admitted into the column 40 so that the heat of the liquid withdrawn from the column may be utilized in pre-heating the charge thereto. If desired, however, the heat exchanger may be by-passed and the cool liquid passed through the pipe52 and thence into the pipe 39 and tower 40. It is best to introduce the charge at a point in the tower which will have approximately the same temperature as that of the entering charge and thus if lthe cool liquid is introduced Without having been passed through the heat exchanger, it will ordinarily be introduced at a. point higher up in the column than in the case wherein the charge is preheated. In one way of operating, the cooling supplied to the condenser 29 may be so regulated that the condensate is not 'cooled down as low as atmospheric temperature but is discharged into the pipe 30 at a temperature somewhat above, for example, about .10G-125 F., and in this case the condensate may be passed through the line 52 and pipe 39 and discharged at a suitable intermediate point in the column 40. When passing the distillate from the condenser 28 into the receiving drum before admitting it into the rectifying column 40, it is preferable to cool the condensate down to a temperature -approaching atmospheric or even lower in order that the gas removed through the line 36 may be as dry as possible. 5 It is advantageous to effect a primary separation of gas from the distillate obtained from the condenser 28 since the removal of gaseous constituents from the distillate effects a reduction in the quantity of fiuid required Yto be passed lthrough the rectifying tower and furthermore the reduction of the permanent gas content in the charge to the column facilitates proper rectification in the ,column. Care should be taken not to apply any more heating to the column 40 than is necessary to supply the heat required for rectification and Vto properly strip the distillate of its more gaseous contents sincel the application of undue heat causes the distillate to go off color and it is preferable to conduct the rectification in. such away that there is a minimum volume of liquid in the bottomv of the tower wherein-the greatest heat obtains',

the liquid preferably being rapidly with'- drawn from the system and cooled before it has been subjected to the heat for sufficient.

time to cause a material deterioration in color. And when operating in accordance with the higher temperature method, that is, whenthe liquid condensate is removed from the condenser coil 28 at temperature above atmospheric, for example, at about 100 F. or higher, it is preferable to pass the distillate directly to the rectifying column 40 and not collect it in the receiving drum 35.

In the preferred manner of carrying on the process, cracking is carried on in the still 11 under the desired pressure and this pressure is maintained through the fractionating column 18 and condenser 28, the pressure then being dropped to a pressure approaching atmospheric in the fractionating column 40 with an intermediate drop in pressure in the receiving drum 35 when the -drum is employed. Ordinarily distillation a'nd the primary separation or fractionation is carried on under several hundred pounds pressure and the rectification of the distillate obtained by condensing the vapors from the first separation is carried on at about atmospheric pressure or at a pressure somewhat higher, for example, about 15 pounds to 50 pounds. It is 4 advantageous to carry on the final rectifica- Y tion under a pressure somewhat above atmospheric since a rectified condensate may thus be obtained that is reasonably stable, since the use of some pressure increases the capacity of the rectifying unit. since a substantially dry gas may be obtained with less cooling than in case the pressure were dropped to atmospheric and since the use of some pressure in the rectifying unit facilitates the discharge of the products 'obtained In manufacturing gasoline to meet the present specifications, it is advantageous to rectify the distillate under a pressure of about 25 pounds. When the receiving drum 35 is used for collection of the distillate and for a preliminary separation of the gas before rectifying the'liquid, the pressure may be dropped to any degree intermediate the pressure obtained in the condenser 28 and the pressure employed in the rectifying column 40. This pressure may approximate'the pressure inthe rectifying column or f there may be al substantial drop between the separating drum 35 and rectifying column 40. lFor example, when using several hundred pounds pressure in the condenser 28, and

labout 25 pounds pressure in the'rectifying be substantially free of'fixed or permanent gases or at least free of the lighter of the permanent gases, it being understood that by proper rectification a certain amount of fixed gas, more particularly the fixed gases of lhigher order, may be held in solution inthe rectified liquidA withdrawn, -although the product is reasonably stable and Well adapted for handling in storage and transportation.

At the present time"`gasoline specifications call for a 96% recovery as indicated on the standard Engler distillation fiask. The gasoline distillate as produced in pressure cracking systems when tested Qn the standard Engler fiask ordinarily shows a percent recovery considerably lower than that required, for example, about 92%. The practice of the herein described invention enables the production of gasoline that meets the 96% recovery requirement with a minimum loss of liquid constituents in the exit gases from the system. i

The rectified gasoline or naphtha distillate removed either'through the pipe 49A or pipe 51 may be conducted to suitable storage and passed to suitable treating apparatus. Thus the distillate may be passed through a continuous treating system wherein it is first contacted with sulfuric acid, preferably dilute acid, then Washed with caustic solution, or otherwise properly purified to stand the tests required for marketable gasoline. paratus illustrated, the drawoff lines 49, and 5l extend to a line 53 by which the distillate may be conducted to a tank 54, and an acid treating unit 55 and an alkali Washing unit 56 are indicated through which distillate from the storage tank may be successively passed for treatment with sulfuric acid and caustic solution. The gases removed from the separating drum 35 through the line 36 andthe gases removed from the rectifying apparatus through the line 45 as well as the gases that may be collected in the treating operation may be used for fuel or they may be passed to absorption or compression apparatus f-or the recovery of any liquid constituents containedv therein. It is preferable, however, that the rectification be so conducted in the column. 40 that the gases removed through the line 45 will be substantially dry, or will contain such a small proportion of normally liquid constituents that it would not be, practicable to further treat the gases y for the extraction of gasoline constituents,

and sothat the gas may thus be used economically as a fuel.

In one way of practicing the invention one rectifying tower 40 may be used for handling the distillate Vof several batteries of cracking stills, and thus in each battery oil is subjected to distillation underI pressure, a primary rectification or fractionation of the 1evolved va- `pers is carried on under pressure and the vapors from `the primary Aseparation are condensed under pressure and the distillate thus collected from each-battery is discharged into a rectifyin g column whereinit is fractionated or rectified at reduced pressure.

Obviously many modifications and variations of the invention, as hereinbefore 'set forth, may be made Without departing from In the ap- -and an overhead vapor fraction, condensing said vapor fraction While still 'under superatmospheric pressure, passing resultant condensate directly to a rectifying apparatus and subjecting the condensateV to rectification 4therein under a pressure reduced from that obtaining in the cracking Zone but derived therefrom.

2. In the conversion of higher boiling hydrocarbon oils into lower boilingl ones, the vprocess that comprises subjecting hydrocarbon oil to cracking temperature under superatmospheric pressure .to effect cracking and vaporization, subjecting evolved vapors to dephlegmation While still under superatmospheric pressure to form a reHuX condensate and an overhead vapor fraction, condensing said vapor fraction while still under superatmospheric pressure, passing resultant condensate to a rectifying'apparatus and subjecting the condensateto rectification therein under a pressure reduced from that obtaining in the cracking Zone but derived therefrom to form a product of desired boiling point and vapor tensionand then subjecting the product to a purifying treatment to standing the tests for a marketable product.

3. In the conversion of higher boiling hydrocarbon oils into lower boiling ones, the process that comprises subjecting hydrocarbon oil to cracking temperature under superatmospheric pressureito effect cracking'and vaporization, subjecting evolved vapors to dephlegmation While still under superatmospheric pressure to form/a refiux condensate and an overhead vapor fraction, condensing said vapor fraction while still under-superatmospheric pressure, passing resultant condensate to a rectifying apparatus and subjecting the condensate to rectification therein under a pressure reduced from that obtaining in .the cracking zone but derived therefrom to form a product of desired boiling point and vapor tension and then subjecting the product to treatment With sulfuric L hand this 16th day of May 1927.

OTTO BEHIMER.

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