US2120655A - Conversion of hydrocarbon oils - Google Patents

Description

Jun 14, 1938. LE ROY G. STORY CONVERSION OF HYDROCARBON OILS Filed April 21, 1951 Nh. AM. MGWII mig l BY @545W .Patented June 14, li938 PATENT OFFHCE CONVERSION F HYDROCARBON OILS Le Roy G. Story, Mount Vernon, N. Y., assigner to The Texas Compan poration of Delaware Application April 21,

7 Claims.

line having a high antiknock value and fixed gases which may be used as fuel or for otherpurposes 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 sothat` a wide selection of cutsv for cracking may be made by segregating various fractions according to the desired volatility or refractorinessand each fraction subjected to the most suitable type of conversion operation. .Accordingly, the low boiling products vaporized in the pressure crack- ,10 ing 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 45 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 wherey, New York, N. Y., a cor- 1931, Serial No. 531,693

'(Cl. IBG-Jill) in an apparatus is shown for conveniently carrying out the invention and forming one embodiment thereof. f

In the drawing the reference character l represents a heater for heating oil under pressure; 2 and 3 a pair of stills for separating vapors from residual oil; l a dephlegmator for dephlegmating or'fractionating vapors from the stills 2, 3; 5 a vapor phase cracker for cracking oil in the Vapor phase; and 'i a flash still and dephlegmator for vaporizing residue and fractlonating the vapors from the stills, 2, 3; 8 and 8a, 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 thestills 2, 3, flash still 6, vapor phase cracker 5, and coke stills 8 and 8a.

The heater I comprises any well known type oi furnace having a coil or tubular heater l0, located therein, and connected to an extraneous supply line ll and a clean distillate charge line l2. A burner i3 supplies heat to raise the oil passing through the coil Il) to conversion temperatures. A transfer line Hl, 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 2l] and a liquid overow pipe 2l. The vertical type of still is shown for illustrative purposes only and other shape 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-off lines 2,3 and 24 for withdrawing residual liquid continuously or intermittently. A vapor pipe.25, regulated by a valve 26, conducts Vvapors from the stills 2 and l3 to a line 2l, referred to hereinafter. A branch line 28, in which is interposed a valve 29, serves to conduct the vapors, if desired, to the dephlegmator 4.

'Ihe dephlegmator 4 may conveniently take the form of a bubble tower equipped with trays to contact the vapors and reflux condensate. A. cooling coil 30 is provided in the top of the dephlegmator to supply cooling thereto by an eX- traneous cooling medium. A vapor pipe 3l conducts vapors from the dephlegmator to a condenser coil 32. A condensate line 33 serves to convey the condensate from the condenser to a receiver 34 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 31, regulated by valves 33 and 39 respectively, communicating with the bottom thereof to withdraw reiiux condensate from the bottom of the tower. A line 40, in which is interposed a valve 4l, connected to the side of the dephlegmator, serves to withdraw a side cut therefrom, if desired. The reflux condensate pipes 36 and 81, as well as the side pipe 4D, separately connect to a line 21, referred to heretofore, which communicates at diiferent elevations with the upper fractionating section of the tower 9 by means of branch lines 42 and 43. A line 45, regulated by valve 45, communicating with the line 21, leads to the tubes orcoil 41 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 Ivapor phase cracking apparatus. A convenient type of furnace for such use maybe similar to that disclosed in U. S. Patent No. 1,717,334, June 11, 1929, to Luiz de Florez. A pipe 48, controlled by valves 49 and 5t, connects the cracking vcoil 41 tothe stripper section of `the tower 8. Branch lines 5| and 52 connect .the line 48 to the coke stills '8 and 8a.. 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 Vto the flash still 6, a residue line `55 serves to `conduct residuum thereto from the stills 2 and 3. A vapor line 55 conducts vapors from the iiash drum to the dephlegmator 1.

A vapor line 58 connects "the dephlegmator 1 toV the line 21 referred to heretofore. A residue draw-off line 68 serves to'wthdraw residue from the flash still 6. A-branch line 8l serves to conduct the residue, if desired, to a charge line 62 leading to the stripper section of tower 9. A reiiux condensate line 63 conducts reflux condensate from the bottom of dephlegmator 1 to the clean distillate charge line 84. A branch line 65, controlled by valves 66 and 61, connects the reflux line V153 with the line "21, wherebyv the condensate may be transferred to the fractionator 9. A branch line 68, controlled by valve 159, connects the line 55 to the line-21 ahead of valves 18 and 1| in line 21 so that the condensate,` if desired, may be sent to the vapor phase cracker via lines 21 and 45. A condensate line 15 serves to withdraw condensate from the middle of dephlegmator 1 to the line v65.

Referring to the stripper and fractionator 9, it will be noted that vthe upper section of the `tower constitutes a fractionating tower while the lower section constitutes the stripper. The sections are separated by a partition 88 having a Vapor riser 8i 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. Y

v A charge line 62 leads to the top of `the stripper to conduct fresh charge thereto aswell as residuum from the line 6I, if desired. A residue draw-,olf line 83 serves to withdraw unvaporized oil from the bottom of the stripper. A branch line B4, having a pump 84'` serves to transfer the residuum from line 83,7if 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 6I 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 85, connected to line 43, serves to withdraw condensate collecting in the bottom of the fractionator E3 or condensate in line 21 to storage or to conduct the lcondensates to the charge line 84 whence they are forced by pump 9| to the coil i8. 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 45leading 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 TS1-connects the condenser coil 98 to a receiver 95 which is equipped with the usual gas releaseline 99 and liquid draw-oli? line |88.

In -practicing the invention with an apparatus such as that shown lin the drawings, charging stock, such as crude oil,-ischarged tothe 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 throughV the riser 8l to the fractionator. A clean distillate collects above the partition 8D and is conducted vby the lines 88 and 54 to the pressure crackingv coil 10. The clean distillate passing to the coil I0 is preferably a cracking stock of the nature of gas oil. If desired, an extraneous charge of o'il may be introduced through the'line -Il. The addition of extraneous oil is sometimes 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 H convenient in starting up operations. A

The oil in the heating coil i8 is raised to conversion temperatures of the order of '150 F.- 950" 'FL 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 drawings 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 oillmay be charged to one or both stills andthe entire contents of the stills maintained substantially Vas vapors. The vapors from the stills Zand 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 passedthrough rline v28 to the dephlegmator 4. In the dephlegmator the vapors are fractionated to separate a gasoline fraction which Yiscondensed in condenser 32 while the heavier constituents are collected as reflux condens'ate. The reiiux condensate may be collected entirely in the bottom of the tower .4 or separated into selected cuts and o ne Ycut taken off as a side stream throughV line 4'0. 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 fractionatorrg or directly to line to be backtrapped to the heater coil I8. 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 conu ducted 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 1 may be separated into one or more cuts, asV desired. In some cases it may be desirable to pass a substantial amount of the vapors to vapor phase cracker and this may be done by suitable regulation of valves 10 and 1I in line 21, or the vapors by other regulation of the same valves may be sent directly to the fractionator 9. Likewise, one or two cuts of condensate may be made in theV tower 1, these cuts being drawn off through lines 63 and 15. In this way a side cut may be taken off through line 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 'I may be returned to coil I0 through line 94. 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 I0 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 E6 respectively. Y

While I have described the manner in which particular fractions from either the dephlegmator 4 or dephlegmator 1 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 exibility of operation isV an essential feature of my invention whereby selected outs may be treated in a manner to provide optimum conditions for both yield and quality of the desired nished 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 8a by means of lines 5l 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 cokegstills 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 residuurn from the flash still, this oil may be passed through lines 6l and 62 to the stripper.

It is preferable, however, to by-pass it through lines 85 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 Il is by-passed, are fractionated and the reflux condensate or clean distillate, entirely or in part, passed to the heater coil I9. Sometimes it is desirable to separate the reux condensate into selected cuts, and therefore, I have shown a line 93 for making a side cut 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:

l. The method for conversion of hydrocarbon oils which comprises passing fresh charging stock into contact with vapors from a coking Zone to form unvaporized liquid and vapors, fractionating said vapors to form a vapor fraction and a reflux condensate, subjecting said condensate to conversion conditions of temperature and superatmospheric pressure to separate low boiling products as vapors from residual oil, flash distilling said residual oil to produce an unvaporiz/ed residual liquid and a selected distillate for vapor I:

phase cracking, subjecting only said selected distillate toa vapor phase cracking operation, mixing the unvaporized residual oil from the system with the products from the vapor phase cracking operation and passing the resulting mixture to said coking zone.

2. The method for the conversion of hydrocarbon oils by a series of continuous steps which comprises subjecting a hydrocarbon oil to conversion conditions of temperature and superatmospheric pressure to produce a vapor fraction and an unvaporized residue, fractionating said vapor fraction in a first fractionating zone to form a desired product, subjecting the unvaporized residue to flash distillation in a flashing Zone under a reduced superatmospheric pressure, fractionating the vapors evolved during ash distillation in a second fractionating Zone to separate a selected fraction suitable for vapor phase cracking, subjecting said fraction, while still retaining heat from its previous treatment, to a vapor phase cracking operation, conducting the vapor phase cracked products to a coking Zone, separate fromA said flashing zone, passing the vapors from the coking Zone to a stripping zone, introducing fresh charging stock into said stripping zone, separate from said flashing Zone, separating a clean condensate from the resulting vapors, utilizing clean condensate so obtained, as said hydrocarbon oil undergoing conversion, and passing residual oil from the stripping Zone to said coking Zone.

3. The process of treating hydrocarbon oil which comprises introducing crude oil into a stripping zone, wherein heat is supplied by hot vapors and the crude is partially vaporized, collecting a clean, relatively heavy condensate, and an intermediate condensate, and condensing the lightest of the crude vapors as a desired product, introducing said relatively heavy condensate into temperature and pressure are maintained and said condensate is subjected to conversion, separating the products of conversion into vapors and a liquid residue, extracting gasoline from said vapors, introducing said residue into a iiashing zone of reduced pressure wherein partial vaporization thereof takes place, subjecting resulting vapors to partial condensation to form a relatively heavy condensate and an intermediate condensate, leaving relatively light vapors uncondensed, introducing the residue from said ilash Zone into a coking zone, cracking in the vapor phase the intermediate condensate last mentioned, introducing the highly heated cracked vapors into said coking Zone to maintain the temperature thereof, and introducing vapors from said coking Zone into said crude stripping Zone to aid in the stripping of said crude oil.

4. The process of treating 'hydrocarbon oil which comprises introducing crude oil into a stripping zone wherein heat is supplied by hot vapors, and the crude is partially vaporiz'ed, collecting a clean relatively heavy condensate and condensingA the lightest of the crude vapors as a desired product, introducing said condensate into a cracking zone wherein cracking conditions of temperature and pressure eXistand said condensate is subject to conversion, separating the products of conversion into vapors and a liquid residue, extracting gasoline from said vapors, introducing said residue into a iiashing Zone of reduced pressure wherein partial vaporization thereof takes place, subjecting resulting vapors to partial condensation to form a condensate, leaving relatively light vapors uncondensed, in-

roducing the residue from said iiashing zone into a coking zone, cracking in the vapor phase the condensate last mentioned, introducing the highly a cracking Zone wherein cracking conditions of heated cracked vapors into said coking zone to maintain the temperature thereof, and introducing hot vapors from saidrcoking Zone into said stripping Zone to aid in the stripping thereof. Y

5. A process in accordance with claim 3 wherein said relatively heavy condensate second mentioned is recycled to said cracking Zone first mentioned.

6. A process in accordance with claim 3 wherein unvaporized portions of said crude charging oil are introduced into said coking zone.

'7. The method for the conversion of hydrocarbon oils by a series of continuous steps, which comprises subjectingY a hydrocarbon oil to conversion conditions of temperature and superatmospheric pressure to produce a vapor fraction and an unvaporized residue, fractionating said vapor fraction, in a iirst fractionating Zone, subjecting the unvaporized residue to flash distillation in a iashing Zone under a reduced superatmospheric pressure in a flashing Zone, separate and apart fromthe coking zone hereinafter specied and from the resultant vapors produced in the coking operation, fractionating the vapors

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