US2093278A - Process for the treatment of hydrocarbon oil - Google Patents

Description

Sept. 14, 1937. P. c. KEITH, JR 2,093,278

PROCESS FOR THE TREATMENT OF HYDROCARBON OIL I I Filed Oct. 5, 1953 INVENTOR A'ITORNEY Patented Sept. 14, 1937 FATENT @FHQE PROCESS FOR THE TREATMENT OF HYDROCARBON 01L Percival 0. Keith, Jr., Peapack, N. 5., assignor to Gasoline Products Company,

Inc, Newark,

N. J a corporation of Delaware Application October 5,

3 Claims.

This invention relates to processes for converting relatively high boiling hydrocarbon oils into lower boiling products, particularly gasoline.

It is an object of my invention to provide a plural section cracking unit, one section of which is adapted to make from relatively heavy or dirty charging stock a clean charging stock for cracking in another section.

The above mentioned and further objects and advantages of my invention will be made clear in the following description taken in conjunction with the accompanying drawing.

Referring more particularly to the drawing, fresh charging stock for example, topped crude or other relatively heavy hydrocarbon oil, is forced by pump i through charging line 2, preheating coil 3, heat exchanger 4, heat exchanger 5, and branch lines 6 and 1, into an intermediate section in combination tower 8, wherein it is contacted with highly heated vapors rising through the tower, as will be explained more fully hereinafter, The amount of oil introduced through the pipe I is preferably only that sufficient properly to reflux the baiile plates 9, while the remainder is introduced through pipe 6, the valves til and Il serving as control means. The unvaporized portions of the fresh relatively heavy charging stock are collected on trap out tray 2 with the condensed portions of the hot vapors rising through the tower, and withdrawn through pipe 13 into accumulator drum M, from which they are passed through pipe I5 by pressure pump it into heater H, which is preferably of the tubular type. The oil is raised to a cracking temperature in the heater ii, and may undergo some conversion therein, emerging at a temperature of from 800 to 900 F., for example about 856 F. This hot oil passes through pipe i8 into reaction chamber i9, wherein further conversion thereof takes place without additional heating. This reaction chamber is preferably vertically disposed, the line 18 connecting at the top thereof. If desired the heater ll may be so operated as to cause therein part, or all, of the desired cracking of the charging stock, or only a very small portion of the cracking may be accomplished in the heater, and the rest may take place in the reaction chamber l9. Preferably a considerable portion of the cracking takes place in both the heater and the reaction chamber, the total cracking per pass amounting to possibly 12-13%, although the percentage of cracking may be less or more than that mentioned, depending on the stock being treated, this being in the nature of a viscosity breaking operation. The pressure on the oil in 1933, Serial No. 692,237 a (Cl. l-48) the reaction chamber is preferably of only a moderate value, e. g. 225 pounds per square inch, this being preferably substantially the same as the heater outlet pressure, although pressures from atmospheric to 480 pounds per square inch may be used in both heater and reaction chamber. It is generally desirable however, to operate considerably below the 400 pound value in order to prevent the deposition of large amounts of coke.

The cracked products pass oil from the reaction chamber through pipe 29 and reducing valve 2i, into a lower section "i2 in the combination tower 8, under a pressure preferably considerably lower than that in the reaction chamber, e. g. 45 pounds per square inch, although pressures from atmospheric to pounds per square inch, or more, may be used if desired, the main requisite being that the pressure be lower than that in the reaction chamber, so that flashing takes place by the contained heat of the hot products. In the combination tower 8 the introduced cracked products separate by their contained heat into vapors which rise upwardly through the tower, and liquid residue which collects on trap out tray 22. The highly heated vapors rising upwardly through the tower serve to strip the fresh charge introduced through pipes 6 and l of lighter products in the nature of gas oil, kerosene, and the like, these lighter products rising in vapor form past the baffle plates 9, bubble trays 23, and trap out tray 24, upon which the heavier portions thereof condense, while the lighter vapors move upwardly past bubble trays 25, heat exchanger coil 3, and bubble trays 26. The vapors which reach the top of the tower pass off through vapor line 2'5, and condenser 28, into receiving drum 2E3 having the usual gas draw off line 29 and liquid draw off line 38f, these vapors being of the boiling range desired for the final product, e. g. gasoline. Some of the distillate collecting in the drum 29, may be pumped back in the usual manner through line 33 by pump 3! to serve as reflux in the top of the tower. The condensate collecting on the trap out tray 25 is so selected as to be suitable for use as clean cracking stock and this clean condensate product, which may, for example, comprise light gas oil and kerosene, is drawn off through line 32 and heat exchanger 4, into accumulator 33, from which it is withdrawn through conduit 35 and forced by pump 36: through line 3'! and heat exchanger 38, into an intermediate point in combination tower 539. A portion of the liquid product from accumulator 33 is forced through line 48, having branches 4! and 42, to serve as reflux on the bubble trays 23 and 25 respectively, valves being provided to effect the necessary control. A portion of this lightly cracked product, e. g., gas oil, may be drawn off through line 43 and cooler 44, into storage drum 55, for use as Diesel oil, or for any other purpose, the necessary control being effected by valve 46. In the combination tower 39 the introduced clean condensate stock flows downwardly over balile plates 47 against an upwardly rising current of highly heated vapors, with the result that the condensate is highly heated. A portion of this condensate may be vaporized. The unvaporized portions of the introduced clean condensate, mixed with the condensed portion of the rising vapors are collected on trap-out tray t8 and withdrawn through pipe 49 into accumulator 50. From 50 the condensate is withdrawn through pipe 5| and forced by pump 52 through cracking heater or furnace 53, which is preferably of the tubular type, being raised in temperature, by passage through the heater, to a rapid cracking temperature, preferably about 900 F. and under a pressure of a relatively high value, preferably about 750 pounds per square inch, although somewhat higher or lower temperature and/ or pressure may be used. The temperature may range, for example, from 850 to ll00 FL, while the pressure may be several hun dred pounds higher or lower than that mentioned as preferred, the values selected depending largely upon the character of the charging stock and the particular final products which it is desired to produce. From the furnace the highly heated cracked products pass through conduit 54 into reaction chamber 55, which is preferably verti-- cally disposed, the line 5 entering the top thereof. The crackingper is preferably considerably higher than that taking place in the heater H, and may be, for example, in the neighborhood of 18% to 20%, although the value may be higher or lower than that mentioned, depending upon the character of the charging stock and the particular conditions selected for operation. The major portion of the cracking preferably takes place in the reaction chamber 55, a part only being effected in the heater 53, although the proportion of cracking in the heater with respect to that taking place in the reaction chamber may be altered as desired by varying the time of passage of the oil through. the heater and the temperatures to which it is subjected therein. From the reaction chamber 55 the cracked products pass through pipe 55 and reducing valve 51, into the lower part'fia of combination tower 39, which is maintained at a pressure considerably lower than that in the reaction chamber 55, being, for example, in the neighborhood of 240 pounds per square inch. This value is given by way of illustration and approximates that preferred in most cases, although higher or lower pressure may be used, depending upon the amount of lighter products which it is desired to separate from the cracked oil introduced into the combination tower from the reaction chamber. The lower the pressure in the combination tower, the greater the amount of light products flashed off. The line 56 preferably withdraws oil from the lower part of reaction chamber 55, and in order to prevent accumulation of coke around the point of connection of line 56 with the reaction chamber, and also to prevent the accumulation of coke in the line 56, a portion of the combined feed forced by the pump 52, may be diverted through cross-over line I! into the lower portio-n of the reaction chamber, slightly above the point of connection of the line 56, the amount of oil so introduced being sufficient to agitate and flush out any accumulating carbonaceous matter, the control being effected by valve 18. The amount of oil so by-passed through line Tl should be sufficient to keep the temperature in the lower part of the reaction chamber down. to a value of approximately 800 F., more or less. The lower portion 58 of this combination tower constitutes an evaporator or separator. The evolved vapors pass upwardly through trap-out tray 48, baffles 41 and bubble trays 59, encountering downwardly flowing streams of reflux condensate, and fresh charge introduced through pipe 31, with the result that heavier fractions of the rising vapors are con,

densed and collected on the trap-out tray 48 with unvaporized portions of the fresh charge, to be recycled through the heater 53 and further cracked. The vapors remaining uncondensed at the top of the upper section 60 of combination tower 39; which acts as a ,dephlegmator or fractionator, pass off through vapor line 6|, heat e-x-' changer 38, wherein partial cooling is effected, and final condenser 62, into receiving drum 63,- which is provided with the usual gas draw-off pipe 64, and liquid draw-off pipe 65. A portion of the distillate may be pumped back from the drum 63 through pipe 06, by action of pump 61, to serve, in the well-known manner, as a refluxing medium in the top of the tower. This distillate so collected will have the characteristics of the final desired product, and if desired may be blended with that collected in. drum 29, by opening valve 68 in cross-over line 69. Liquid residue remaining unvaporized in the bottom of evaporator section 58 of combination tower 39, may be drawn off from the system in part or wholly, through line 16, but is preferably passed throughconduit 10, having reducing valve H, into the lower portion 12 of combination tower 8, which serves as a flash drum for flashing off the lighter products from the residue. drum 12 is aidedsomewhat by the contacting of the residuewith the highly heated products from the reaction chamber [9. The action is further aided by the fact that both liquid residue and cracked products from reaction chamber l9 are preferably introduced below the level of the liquid on the tray 22. Excess oil accumulating on the tray overflows the top thereof and passes downwardly through tower 8, from which it. is withdrawn through draw-off line 13, heat exchanger 5, and cooler 14, to fuel oil storage drum 15.

The quantities of stock flowing through the various. pipes of a. combination unit such as disclosed herein, will, of course, vary both with the amount of fresh charge introduced into the system and with the specific conditions set up in the several sections of the systems, however, the following figures set forth one successful set of operating conditions.

Assuming the fresh charge to be 26 A. P. I. topped Persian crude, this being the remaining 60% after 40% of the original crude has been distilled off, the temperature of the oil at the point of introduction into combination tower 8 through pipes 6 and I, after preheating in coil 3 and exchangers 4 and 5, may be about 575 F., and the pressure thereon may be about 45 pounds per square inch. The oil withdrawn from trap-out tray I2 may have a temperature of .700" F., and its temperature after leaving the heater I! may be about 850 F. the pressure be- The flashing process in flash ing 225 pounds per square inch or thereabouts. Under these conditions a cracking to products in the gasoline boiling range, per passage of the oil through the heater I1 and reaction chamber I9, may be about 12 to 13%, the amount of oil passing through the heater I! being about double that of the fresh charge introduced through pipe 2, and comprising, for example, one part of topped crude and one part of heavy gas oil. The temperature at the top of the combination tower 8 may be about 375 F., and the percentage of gasoline passed to the receiver 29, with respect to the amount of fresh charge through pipe 2, may be about 20 to 25. The fuel oil withdrawn from the bottom of the combination tower through conduit 13 may constitute about 45 to 50% with respect to the fresh charge, this residue being a tar having a gravity of 13 to 14 A. P. I., for example. Gas oil to the extent of may be withdrawn through line 43 to storage, while the amount of clean condensate introduced into the combination tower 39 through pipe 31 may, in amount, approximate 38% with respect to the fresh charge. The temperature in the base of combination tower may be about 750 F. and the pressure about 240 pounds per square inch, while the temperature and pressure in the reaction chamber 55 may be about 900 F. and 750 pounds per square inch. The temperature of the vapors at the top of the combination tower 39 may be about 450 F. and the quantity of gasoline collected in the receiver 63 may be about 15 to with respect to the quantity of the fresh charge through line 2.

Operation In operation fresh charge, such as topped crude, crude residuum, or even heavy distillate, is introduced through the charging line 2, preheating coil 3, heat exchangers 4 and 5, and pipes 6 and 1, into an intermediate point in the combination tower 8, the amount of fresh charge introduced through pipe I being sufficient for refluxing the baffles 9 and maintain the proper temperature, while the remainder is directed through pipe 6 onto the trap-out tray l2. The introduced oil is stripped of its lighter fractions by its contained heat resulting from its preheating, and as a result of the contacting there- I of with rising highly heated vapors in the tower 8. The evolved vapors pass upwardly countercurrent to downwardly flowing reflux condensate, with resulting condensation of heavier fractions of the vapors. Those fractions remaining uncondensed at the top of the tower pass off out tray 24, and the treatment thereof will be explained more fully hereinafter. This condensate may be, for example, a gas oil of about 36 A. P. I. gravity.

The unvaporized portion of the fresh charge and condensed portions of the rising vapors are collected on trap-out tray l2, and withdrawn to accumulator M, from which they are forced through pipe 15 and heater or furnace ll, wherein the oil attains a temperature preferably falling in the range of 800900P F., suitably about 850 F. under a pressure which may vary considerably, e. g. from a few pounds per square inch to several hundred pounds per square inch, preferably about 225 pounds per square inch, and may be subjected to a certain amount of cracking also. The highly heated products then pass into reaction chamber l9 wherein further moderate cracking thereof takes place, this being in the nature of a viscosity breaking operation, wherein the total cracking to productsin the gasoline boiling range may be from 8% to 15% per pass, preferably about 12-13%. The prodnets of conversion then pass through pipe 20 and reducing valve 2i, into the lower part of the combination tower 8, wherein, due to the reduc tion of pressure to a relatively low value, separation of the cracked products into vapors and liquid residue results, the vapors rising upward- 1y through trap-out tray l2 against downwardly flowing charging stock introduced through pipe I, with attendant condensation of the heavier fractions of the vapors. The liquid residue collecting on tray 22 is, in effect, reboiled by the hot products introduced by pipe 20, the product remaining in liquid form overflowing the trapout tray into the base of the tower, from which it is removed as fuel oil through pipe 13 and heat exchanger 5, serving to aid in preheating the fresh charge.

The clean condensate removed from trap-out tray 24 is subjected to heat exchange with the fresh charge in heat exchanger 4, andthence passes into accumulator 33 from which it is withdrawn, through pipe 36, and forced through line 31 and heat exchanger 38, into an intermediate point in the combination tower 39, another portion of this condensate being returned through line 40 to tower 8 as reflux, and a third portion being removed if desired through exchanger 38 for use as. Diesel oil, or as any other product. In the combination tower 39 the introduced clean condensate is partially vaporized by contact with the highly heated vapors, the portion remaining uncondensed being collected on trap-out tray 48 with condensed fractions of the rising vapors. This condensate constitutes the charging stock for cracking furnace 53 and during passage 'therethrough is raised to a cracking temperature of, for example, 850-1000 F'., preferably about 900 F., under a pressure, for example, of from 200 to 1000 pounds per square inch, preferably about 750 pounds per square inch, thereafter being introduced into the reaction chamber 55, a considerable portion of cracking taking place in the furnace 53, or not, as desired. In the reaction chamber 55 further conversion takes place, the total amount of cracking being preferably as great as possible without deleterious coking. The cracking to products in the gasoline boiling range, per pass, may range from 15 to 40%, for example, depending on the character of the stock being treated, but is preferably in the neighborhood of 18-20% per pass. The highly heated cracked products are then introduced through pipe 55, into the lower part 58 of combination tower 39, with attendant reduction of pressure, by action of valve 51, sufficient to cause self vaporization of a large portion of the cracked products. Flushing oil may be introduced through cross-over line 11 into the lower part of the reaction chamber 55 to an extent of, for example, about 5% with respectto the amount of stock charged to the heater 53. The vapors rise upwardly past the trap-out tray 48 and undergo partial condensation by contact with the downwardly flowing charging stock introduced through line 31. The vapors remaining uncondensed are then subjected to fractionation by passage upwardly through the bubble trays or similar devices 59, to which a refluxing medium is supplied through pipe 66. The vapors still uncondensed at the top of the tower pass off through pipe 6|, are cooled in heat exchanger 38, finally condensed in condenser 62 and collected in receiving drum 63 as a desired product. This may be blended if desired with that product collected in receiving drum .29, by opening valve 68 in cross-over pipe 69. Liquid residue is withdrawn from the bottom of combination tower 39, and part or all thereof may be diverted from the system through pipe 16, but this residue is preferably passed through pipe Ill and reducing valve 'll, into the flashdrum portion 12 of combination tower 8, wherein, due to the reduction in pressure thereon and the contacting thereof with highly heated products from pipe 20 partial vaporization results, the vapors passing upwardly through trap-out tray I2, While unvaporized liquid or residue overflows the tray 22 into the base of the tower. The; heavier portions of the rising Vapors are condensed and collected on trap-out tray l2 and are recycled through the heater l1 along with heavier fractions condensed from the vapors evolved from stock introduced through pipe '20, while the unvaporized residue may be withdrawn continuously or intermittently from the base of the tower, through pipe 13. The character of this residue may be varied as desired by properly selecting the drop in pressure between towers 39 and 8, and the other operating condition. This product is preferably withdrawn in suitable condition for use as fuel oil.

The unit described hereinbefore is very flexible and can be used to carry out other processes than those specifically discussed hereinbefore, for example the unit may be used for reforming naphtha. No changes in the equipment are necessary to accomplish this end. The high pressure side of the unit may be used-with normal flow throughout as described hereinbefore, while the low pressure tower 8 may be used for flashing the tar from the high pressure tower 39, the low pressure furnace l1 and reaction chamber [9 then being unused. The naphtha maybe raised advantageously to somewhat higher temperatures than that used in cracking gas oil, e. g., 950 F. or more in the heater 53 and then passed to the reaction chamber 55, the total amount of cracking per pass being approximately the same as in the case of gas oil. Approximately the same pressure may be used onthe reaction chamber 55 and combination tower 39, i. e. 750 pounds and 240 pounds respectively.

While I have described a particular embodiment of my invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

I claim:

1. The process of treating hydrocarbon oil that comprises subjecting condensate oil in a cracking zone to cracking temperature under superatmospheric pressure to effect cracking, directing resultant products of the cracking into a separating zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, subjecting vapors thus separated to fractionation in a fractionating zone to separate out a desired light distillate and a heavier reflux condensate, directing reflux condensate so formed to said cracking zone, passing liquid residue from said separating zone into a flashing zonev of, lower pressure wherein separation of vapors from residue takes place, passing vapors thus separated into a primary fractionating zone separate from the first-mentioned fractionating zone, introducing charging stock of the nature of crude residuum into said primary fractionating zone to cause partial condensation of the vapors and eifect partial vaporization of said charging stock, withdrawing unvaporized portions of said charging stock together with resultant condensate from the primary fractionating zone, subjecting the admixed unvaporated charging stock and condensate in a separate cracking zone to cracking temperature under superatmospheric pressure to eflect cracking, directing, resultant products of cracking into said flashing zone to effect separation thereof into vapors and residue, subjecting vapors remaining uncondensed in said primary fractionating zone to further fractionation to separate out reflux condensate and combining reflux condensate so formed with aforesaid condensate passing to the first-mentioned crackingzone. l

2. The process of treating hydrocarbon oil that comprises subjecting condensate oil in a cracking zone to cracking temperature under superatmospheric pressure to effect cracking, directing resultant products of the cracking into a separating zone maintained under superatmospheric pressure wherein separation of vapors from liquid residue takes place, passing separated vapors into fractionating zone and subjecting them to fractionation therein to separate out a desired light distillate and a heavier reflux condensate, directing reflux condensate so formed to said cracking zone, passing liquid residue from said separating zone into a flashing zone of lower pressure wherein separation of vapors from residue takes place, passing vapors thus separated into a primary fractionating zone separate from the first mentioned fractionating zone, introducing charging stock of the nature of crude residuum into said primary fractionating zone to cause partial condensation of the vapors and efiect partial vaporization of said charging stock, withdrawing unvaporized portions of said charging stock together with resultant condensate from the primary fractionating zone, subjecting the admixed unvaporized charging stock and condensate in a separate cracking zone to cracking temperature under superatmospheric pressure to effect cracking, directing resultant products of cracking into said flashing zone to effect separation thereof into vapors and residue, passing vapors remaining uncondensed in said primary fractionating zone to a secondary fractionating zone, subjecting the vapors therein to fractionation to separate out a desired distillate and heavier reflux condensate and directing refluxcondensate so formed to said first mentioned fractionating zone.

3. The process of treating hydrocarbon oil that comprises subjecting condensate oil in a cracking zone to cracking temperature under superatmos pheric pressure to effect cracking, directing resultant products of the cracking into a separating zone maintained under superatmospheric pressurewherein separation of vapors from liquid residue takes place, subjecting. vapors thus separated to fractionation in a first fractionating zone to separate out a desired light distillate, passing liquid residue from said separating zone into a flashing zone of lower pressure wherein separation of vapors from residue takes place, passing vapors thus separated into a primary section of a second fractionating zone, introducing charging stock of the nature of crude residuum into said primary section of the second fractionating zone to cause partial condensation of the vapors and effect partial vaporization of said charging stock, withdrawing unvaporized portions of said charging stock together with resultant condensate from the primary section of the second fractionating zone, subjecting the admixed unvaporized charging stock and condensate in a separate cracking zone to cracking temperature under superatmospheric pressure to effect cracking, directing resultant products of cracking into said flashing zone to effect separation thereof into vapors and residue, passing vapors remaining uncondensed in said primary section of the second fractionating zone to a secondary section thereof, subjecting the vapors therein to fractionation to separate out a desired distillate and a heavier reflux condensate and utilizing reflux condensate so formed 10

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