US2065351A - Conversion of hydrocarbon oils - Google Patents

Description

- 1936. LE ROY (5. STORY CONVERSION OF HYDROCARBON OILS OriginaLFiled April 21, 1931 IN VEN TOR L550) 6. STORY A TTORNEY Patented Dec. 22, 1936 UNITED STATES PATENT OFFICE 2,065,351 CONVERSION OF HYDROOARBON OILS Le Roy G. Story, Bronxville, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware 15 Claims.

which may be used as fuel or for other purposes as desired.

The invention contemplates the stripping of fresh charging stock by contact with the vapors from .a coking operation, the separation of a clean cracking stock for a pressure cracking system, the separation of selected cuts for vapor phase cracking and the coking of the residue liquids from the stripping and pressure cracking operation by the sensible heat of the vapor phase cracked products. With suitable type of apparatus and novel methods of operation the volatile products may be concentrated at one zone in the system whereby a gasoline of high antiknock value, consisting of both liquid phase and vapor phase cracked products, may be separated, the heavier components fractionated to produce selected cuts which may be subjected separately to a pressure cracking system and a vapor phase cracking system, while the unvaporized residual oil from the system may be reduced to coke in coking stills.

The process of the invention is flexible so that a wide selection of cuts for cracking may be made by segregating various fractions according to the desired volatility or refractoriness and each fraction subjected to the most suitable type of conversion operation. Accordingly, the low boiling products vaporized in the pressure cracking operation may be separately dephlegmated to produce selected cuts for vapor phase and liquid phase cracking; the residual liquid or pressure tar may .be flash distilled under reduced pressure to likewise produce selected cuts for the same purpose, if desired; or, the entire vapor fraction from both the pressure stills and. the flash still may be concentrated in one large tower, which also receives vapors from the crude stripper, and the resulting mixture of vapors fractionated to separate the desired gasoline, and to produce at the same time a fraction suitable for vapor phase cracking stock and a clean condensate adapted for pressure still cracking.

The invention may be more clearly understood by referring to the accompanying drawing wherein an apparatus is shown for conveniently carrying out the invention and forming one embodiment thereof.

In the drawing the reference character I represents a heater for heating oil under pressure; 2 and 3 a pair of stills for separating vapors from residual oil; 4 a dephlegmator for dephlegmating or fractionating vapors from the stills 2, 3; 5 a vapor phase cracker for cracking oil in the vapor phase; 6 and l a flash still and dephlegmator for vaporizing residue and fractionating the vapors from the stills, 2, 3; 8 and 8d, coke stills for reducing residual oil to' coke by the heat of the cracked products from the vapor phase cracker 5; and 9 a combined stripper and fractionating tower for stripping crude and for fractionating any or all the vapors from the stills 2, 3, flash still 6, vapor phase cracker 5, and coke stills 8 and 3a.

The heater 1 comprises any well known type of furnace having a coil or tubular heater [0, located therein, and connected to an extraneous supply line H and a clean distillate charge line I2. A burner l3 supplies heat to raise the oil passing through the coil NJ to conversion temperatures. A transfer line I4, conducts oil from the heater to either or both of the stills 2 and 3 by means of the branches l5 and I6 respectively.

The stills 2 and 3 are shown as vertical chambers having a vapor connecting line 20 and a liquid overflow pipe 2!. The vertical type of still is shown for illustrative purposes only and other shapes and designs of stills may be employed, if desired, with equal success. The stills are preferably insulated to retain the heat content of the oil and provide reaction time at conversion temperatures. Each still is provided with residue draw-01f lines 23 and 24 for withdrawing residual liquid continuously or intermittently. A vapor pipe 25, regulated by a valve 23, conducts vapors from the stills 2 and 3 to a line 21, referred to hereinafter. Vapors from pipe 25 may be passed to line 21, by way of vapor pipe 25 having regulating valve 26', if desired. A branch line 28, in which is interposed a valve 23, serves to conduct the vapors, if desired, to the dephlegmator 4.

The dephlegmator 4 may conveniently take the form of a bubble tower equipped with trays to 50 contact the vapors and reflux condensate. A cooling coil 30 is provided in the top of the dephlegmator to supply cooling thereto by an extraneous cooling medium. A vapor pipe 3| conducts vapors from the dephlegmator to a con- 55 denser coil 32. A condensate line 33 serves to convey the condensate from the condenser to a receiver 3 which is equipped with the usual gas release line 35 and liquid draw-off pipe 36.

The dephlegmator is further provided with lines 36' and 37, regulated by valves 38 and 39 respectively, communicating with the bottom thereof to withdraw reflux condensate from the bottom of the tower. A line 40, in which is interposed a valve H, connected to the side of the dephlegmator, serves to withdraw a side out therefrom, if desired. The reflux condensate pipes 36 and 31, as well as the side pipe 48, separately connect to a line 21, referred to heretofore, which communicates at different elevations with the upper fractionating section of the tower 9 by means of branch lines 42 and 43. A line 45, regulated by valve 4'6, communicating with the line 21, leads to the tubes or coil 4'! located in the vapor phase cracking furnace 5.

The vapor phase cracker 5, shown for purposes of illustration as a diagrammatical section, may be any well known or preferred type of vapor phase cracking apparatus. A convenient type of furnace for such use may be similar to that disclosed in U. S. Patent No. 1,717,334, June 11, 1929, to Louis de Florez. A pipe 46, controlled by valves 49 and 58, connects the cracking coil 41 to the stripper section of the tower 9. Branch lines 5| and 52 connect the line 48 to the coke stills 8 and 3a. A vapor line 53 serves to conduct vapors from the coking stills 8 and 8a to the bottom of the stripper section of tower 9.

Referring now to the flash still 6, a residue line 55 serves to conduct residuum thereto from the stills 2 and 3. A vapor line 56 conducts vapors from the flash drum 6 to the dephlegmator l. A vapor line 58 connects the dephlegmator l to the line 21 referred to heretofore. A residue drawoff line 68 serves to withdraw residue from the flash still 6. A branch line El serves to conduct the residue, if desired, to a charge line 62 leading to the stripper section of tower 9. A reflux condensate line 63 conducts reflux condensate from the bottom of dephlegmator T to the clean distillate charge line Ki l. A branch line 65, controlled by valves 56 and 67, connects the reflux line 63 with the line 21, whereby the condensate may be transferred to the fractionator 9. A branch line 68, controlled by valve 69, connects the line 65 to the line 2'! ahead of valves 10 and H in line 2'! so that the condensate, if desired, may be sent to the vapor phase cracker via lines 21 and 45. A condensate line l5 serves to withdraw condensate from the middle of dephlegmator l to the line 65.

Referring to the stripper and fractionator 9, it will be noted that the upper section of the tower constitutes a fractionating tower while the lower section constitutes the stripper. The sections are separated by a partition having a vapor riser 8| therein so that vapors from the stripper may pass to the fractionator. While the stripper and fractionator are shown as a single tower with the fractionator superimposed on the stripper, nevertheless the two sections may be made as separate units and the invention contemplates such an arrangement.

A charge line 62 leads to the top of the stripper to conduct fresh charge thereto as well as residuum from the line 6!, if desired. A residue draw-off line 83 serves to withdraw unvaporized oil from the bottom of the stripper. A branch line 84 having a pump 8t serves to transfer the residuum from line 83. if desired, to the line 48 to be mixed with the cracked products from the vapor phase cracker 5 and thence to be conducted to the coke stills or to the stripper. A branch line 85, controlled by valve 86, connects the lines 6| and 84 whereby the residuum from the flash still 6 may be contacted with the products from the vapor phase cracker.

A clean distillate or reflux condensate line 90, connected to line 2'1, serves to withdraw condensate collecting in the bottom of the fractionator 9 or condensate in line 21 to storage or to conduct the condensates to the charge line 64 whence they are forced by pump 9! to the coil 10. A condensate line 93, connected to the side of the fractionator, and having a pump 93 serves to conduct, if desired, a side cut from the fractionator to the line 45 leading to the vapor phase cracker 5. A vapor line 95 conducts vapors from the top of the fractionator to the condenser coil 96. A condensate line 91 connects the condenser coil 96 to a receiver 98 which is equipped with the usual gas release line 99 and liquid draw-off line In practicing the invention with an apparatussuch as that shown in the drawing, charging stock, such as crude oil, is charged to the stripper through line 62 wherein the fresh charge comes in contact with the hot vapors therein and the charge may be partially cracked and the lighter constituents vaporized. The vapors, including the volatilized constituents of the fresh charge, pass through the riser 8i to the fractionator. A clean distillate collects above the partition 80 and is conducted by the lines and 64 to the pressure cracking coil ill. The clean distillate passing to the coil ii] is preferably a cracking stock of the nature of gas oil. If desired, an extraneous charge of oil may be introduced through the linev H. The addition of extraneous oil is sometimesv desirable in order to provide a uniform charging rate in case the supply from the fractionator runs low and more particularly is such a supply of charge from line I l convenient in starting up operations.

The oil in the heating coil I0 is raised to conversion temperatures of the order of 750 F.-950 F. and a pressure of 200-600 pounds per square inch may be carried on the coil and stills 2 and 3. Two stills are shown in the drawing but any number may be used. Likewise, the stills are shown connected with vapor lines and liquid overflow lines, but it is contemplated that a low liquid level may be maintained in the stills in which case there would be no overflow but instead the hot oil may be charged to one or both stills and the entire contents of the stills maintained substantially as vapors. The vapors from the stills 2 and 3 pass through the line 25 and may be passed directly to the fractionator 9 through line 21.

In one method of operation the vapors from stills 2 and 3 may be passed through line 28 to the dephlegmator 4. In the dephlegmator the vapors are fractionated to separate a gasoline fraction which is condensed in condenser 32 while the heavier constituents are collected as reflux condensate. The reflux condensate may be collected entirely in the bottom of the tower 4 or separated into selected cuts and one cut taken off as a side stream through line 40. In case a side stream is taken off it is preferable to charge this cut to the vapor phase cracker through line 45 while the heavier cut in the bottom of the tower 4 is passed through line 36 and line 21 to the fractionator 9 or directly to line 90 to be 7 backtrapped to the heater coil Hi. When .no side cut is taken from the tower 4 then the reflux may be passed entirely or in part through lines 31 and 45 to either the vapor phase cracker 5 or the tower 9.

The residue from stills 2 and 3 may be conducted continuously or intermittently to the flash still 6. A reduced superatmospheric pressure is maintained in the still 6 so that the lighter fractions of the residual oil are immediately flashed by their sensible heat into vapors. The vapors pass to dephlegmator 1 while residue is withdrawn through line 60 to be disposed of as described hereinafter. The vapors in dephlegmator I may be separated into one or more cuts, as desired. In some cases it may be desirable to pass a substantial amount of the vapors to vapor phase cracker 5 and this may be done by suitable its regulation ofvalves Ill and H in line 21, or the vapors by other regulation of the same valves may besent directly to the fractionator 9. Likewise, one ortwo cuts of condensate may be madein the tower 1, these cuts being drawn off through lines 63 and '15. In this way a side out may be taken off through line 15 and sent to the vapor phase cracker by suitable regulation of valve 69 in branch line 68 and valve 61 in line 66, while a heavier condensate from the bottom of tower 1 may be returned to coil l0 through line 64. In some cases it may be desirable to make a single cut of condensate in tower 1 and this cut may be withdrawn through line 63 and passed to the coil It) or conducted through line 65 to either the vapor phase cracking coil or to the fractionator 9 by suitable regulation of valves 69 and 61 in lines 68 and 66 respectively.

While I have described the manner in which particular fractions from either the dephlegmator 4 or dephlegmator I may be passed to the vapor phase cracker 5 or the fractionator 9, it is to be understood that selected fractions of liquids and/or vapors from both dephlegmators may be passed simultaneously to the vapor cracker 5 or fractionator 9. It will be observed therefore that flexibility of operation is an essential feature of my invention whereby selected cuts may be treated in a manner to provide optimum condi tions for both yield and quality of the desired finished products.

The oil in passing through vapor phase cracker 5 is raised to a temperature suitable for conversion in the vapor phase, say between 950 F. and 1150 F. The hot products of conversion may be transferred through line 48 directly to the stripper section of the tower 9. It is preferable, however, that these products go to the coke stills 8 and M by means of lines 5| and 52, in order that the heat thereof may be used for coking the residual oils from the system. Two coke stills are shown, for purposes of illustration, but only one is ordinarily used at a time while the other is cleaned of the coke deposition therein. The vapors from the coke still pass through lines 53 to the stripper section where they contact the heavy oil charged thereto through line 62.

The residual oil from the system is preferably commingled with the hot vapors from the vapor phase cracking operation. Referring first to the residuum from the flash still, this oil may be passed through lines 6| and 62 to the stripper. It is preferable, however, to by-pass it through lines and 84 to be commingled with the vapor phase cracked products. Therefore, this residue may be used to cool the cracked products in case they are passed directly to the stripper through line 48 or the mixture of residuum and vapors may be passed through lines 5| and 52 to the coke stills where the residue is reduced to coke by the sensible heat of the vapors. Likewise, the unvaporized oil collecting in the bottom of the stripper is withdrawn through line 83 and passed entirely or in part, alone or in mixture with the residuum from flash still 6, into the line 48 to be treated as just described.

The vapors collecting in the fractionator section of tower 9, which may comprise all or a part of the vapors from the entire system, depending on whether the dephlegmator 4 is by-passed, are fractionated and the reflux condensate or clean distillate, entirely or in part, passed to the heater coil l0. Sometimes it is desirable to separate the reflux condensate into selected cuts, and therefore, I have shown a line 93 for making a side out to be returned to the vapor phase cracker 5. The latter is particularly advantageous in case the dephlegmator 4 is by-passed and all the vapors concentrated in the fractionator section of tower 9.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method for conversion of hydrocarbon oils which comprises subjecting hydrocarbon oil to conversion conditions of temperature and superatmospheric pressure to cause cracking thereof, separating the resulting cracked products into a primary vapor fraction and a residual liquid fraction, flash distilling the residual liquid fraction under a reduced superatmospheric pressure to form a secondary vapor fraction, separately subjecting hydrocarbon oil to a vapor phase cracking operation, commingling a relatively cool oil with the products from the vapor phase cracking operation and subjecting the resulting mixture to a distilling operation while out of contact with cracked products undergoing separation as first mentioned to form a tertiary vapor fraction, fractionating said primary, secondary and tertiary vapor fractions in a single dephlegmating zone to separate a relatively light vapor fraction, a relatively heavy condensate and an intermediate condensate suitable for vapor phase cracking and subjecting said intermediate condensate to said vapor phase cracking operation.

2. The method for conversion of hydrocarbon oils which comprises subjecting hydrocarbon oil to conversion conditions of temperature and superatmospheric pressure to cause cracking thereof, separating the resulting cracked products into a primary vapor fraction and a residual liquid fraction, flash distilling the residual liquid fraction under a reduced superatmospheric pressure to form a secondary vapor fraction, separately subjecting hydrocarbon oil to a vapor phase cracking operation, contacting a relatively 0001 oil with the vapors from the vapor phase cracking operation and separating a tertiary vapor fraction therefrom while out of contact with cracked products undergoing separation as first mentioned, fractionating said primary, secondary and tertiary vapor fractions to form a light fraction suitable for producing gasoline and a heavier fraction suitable for cracking, passing a selected portion of said heavier fraction to the vapor phase cracking operation and returning the other portion of said heavier fraction to the oil undergoing conversion conditions of temperature and superatmospheric pressure.

3. The process of treating hydrocarbon oil which comprises introducingfreshrelatively heavy charging stock into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction, an intermediate condensate and a relatively heavy condensate, removing and condensing said light vapor fraction, passing said heavy condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue in a distilling zone separate from said stripping zone, introducing products so separated as vapors into said stripping zone, cracking said intermediate condensate in the vapor phase, and introducing the resulting cracked products into a coking zone, separate from said distilling zone and said stripping zone, introducing a heavy residual oil into said coking zone in contact with said vapors, whereby said residual oil is reduced to vapors and coke, removing vapors from said coking zone and introducing them into said stripping zone in contact with said fresh charge.

4. A process in accordance with claim 3 wherein unvaporized portions of said fresh charge are removed from said stripping zone and introduced into said coking zone as said heavy residual products.

5. A process in accordance with claim 3 wherein said liquid residue first mentioned is flash distilled with attendant formation of vapors and tar, said tar is introduced into said coking zone as said heavy residual oil.

6. A process in accordance with claim 3 wherein said liquid residue is subjected to fiash distillation and vaporized light products are introduced into said stripping zone.

'7. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors, in a first fractionating zone, into a light vapor fraction, an intermediate condensate and a heavy condensate, removing and condensing said light vapor fraction, passing said heavy condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue, in a separating zone, fractionating said vapors, in a second fractionating zone, to form a light vapor fraction and a condensate, removing and condensing said light vapor fraction, introducing said condensate last mentioned into said stripping zone, cracking said intermediate condensate in the vapor phase and introducing the resulting cracked products into a coking zone, introducing a heavy residual oil into said coking zone in contact with said vapors, whereby said residual oil is reduced to vapors and coke, and removing vapors from said coking zone and introducing them into said stripping zone in contact with said fresh chargel 8. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and a condensate, removing and condensing said light vapor fraction, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue, forming a desired product from the resulting vapors, flashing said liquid residue to form therefrom relatively light vapors and unvaporized tar, introducing said tar into a coking zone, segregating an intermediate fraction in said stripping zone lighter than said condensate first mentioned, introducing said intermediate fraction into a vapor phase cracking zone wherein conversion thereof occurs, passing resulting products of conversion into said coking zone, and passing vapors from said coking zone into said stripping zone.

9. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and a condensate, removing and condensing said light vapor fraction, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue, fractionating said vapors to form a light vapor fraction, and a relatively heavy condensate, removing and condensing said light vapor fraction, introducing said relatively heavy condensate into said stripping zone for partial vaporization therein, forming a second condensate in said stripping zone lighter than condensate first mentioned, passing said second condensate to a cracking zone wherein said condensate is cracked in the vapor phase, introducing the resulting cracked products into a coking zone, conducting vapors from said coking zone into said stripping zone, flashing said liquid residue to remove light vapors and leave an unvaporized tar, and introducing said tar into said coking zone to be reduced to coke.

10. A process in accordance with claim 9 wherein unvaporized fresh charging stock from said stripping zone is introduced into said coking zone.

11. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and a condensate, removing and condensing said light vapor fraction, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue, fractionating said vapors to form a vapor fraction and a relatively heavy condensate, removing and condensing said vapor fraction, introducing said relatively heavy condensate into said stripping zone, forming a second condensate in said stripping zone lighter than said condensate first mentioned, introducing said second condensate into a vapor phase cracking zone wherein conversion thereof occurs, introducing the resulting cracked products into a coking zone, introducing unvaporized fresh charging stock from said stripping zone into said coking zone, and removing vapors from said coking zone and introducing them into said stripping zone.

12. The process of treating hydrocarbon oil which comprisesintroducing fresh relatively heavy charging stock into astripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and condensate, removing and condensing said light vapor fraction, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue, fractionating said vapors to form a light vapor fraction and a relatively heavy condensate, removing and condensing said light vapor fraction, combining said relatively heavy condensate with said condensate first mentioned for passage through said cracking zone, flash distilling said liquid residue to form relatively light vapors and leave unvaporized relatively heavy tar, introducing said tar into a coking zone in mixture with unvaporized fresh charging stock withdrawn from said stripping zone, forming a second condensate in said stripping zone lighter than first condensate first mentioned, passing said second condensate through a vapor phase cracking zone, introducing the resulting cracked products into said coking zone to supply the heat necessary for the coking operation, and introducing vapors removed from said coking zone into said stripping zone.

13. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and a condensate, removing and condensing said light vapor fraction, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into relatively light vapors and a liquid residue, flashing said liquid residue to produce vapors and leave unvaporized heavy tar, fractionating the resulting vapors to segregate therefrom a light fraction and a heavy fraction, combining said heavy fraction with said condensate first mentioned, introducing said light fraction into said stripping zone, forming in said stripping zone a second condensate lighter than said condensate first mentioned, passing said second condensate through a vapor phase cracking zone wherein conversion thereof occurs, combining with the resulting cracked products said tar, introducing the combined products into a coking zone and conducting vapors from said coking zone into said stripping zone.

14. The process of treating hydrocarbon oil which comprises introducing fresh relatively heavy charging stock into a stripping zone in contact with highly heated vapors whereby partial vaporization of said stock occurs, separating the resulting vapors into a light vapor fraction and a condensate, removing and condensing said light vapor, fraction, passing said condensate through a cracking zone wherein conversion conditions of temperature and pressure are maintained, separating the resulting products of conversion into vapors and a liquid residue, flashing said liquid residue to produce light vaporous fraction and leave unvaporized heavy tar, introducing said light fraction into said stripping zone, forming in said stripping zone a second condensate lighter than said condensate first mentioned, passing said second condensate through a vapor phase cracking zone wherein conversion thereof occurs, combining with the resulting cracked products said tar, introducing the combined products into a coking zone and conducting vapors from said coking zone into said stripping zone- 15. A process in accordance with claim 14 wherein the vapors separated from said products of conversion first mentioned are fractionated to form a light vapor fraction and a condensate, and condensate so formed is removed and introduced into said stripping zone.

LE ROY G. STORY.

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