US2243291A - Conversion of hydrocarbon oils - Google Patents

Description

- May 27, 1941.

J. D. SEG UY CONVERSION oF HYDRocARBoN oILs Filed Aug. s1, 193s Patented May 27, 1941 UNTED STATE-S PATENT OFFICE CQNVEESION F HYDROCA-RBON OILS Y Jean Delattre Seguy, Chicago, Ill., ,assignerl to Universal (bi1 Products Company, Chicago, Ill., a corporation of Delaware Application August 31, 1939, Serial No; 292,880

3 Claims.

'I'his invention relates to an improved cracking system involving a combination of interdependent cracking steps, comprising vapor-phase cracking, mixed phase cracking and reforming which cooperate to produce from the charging oil and intermediate liquid conversion products of the process high yields of gasoline or relativelyv light gasoline fractions of high antiknock value, normally gaseous products containing a. high proportion of polymerizable olens and minor yields of good quality liquid residue.

The vapor-phase cracking step of the system employs as charging stock a reflux condensate, formed by fractionation of the vaporous conversion products of the process, which has an end-boiling point of the order of 600 to 650 F., or thereabouts, and is substantially devoid of free carbon (containing say 0.01% or less as determined by the Conradson method). This material is cracked in essentially vaporous state under conditions regulated to produce only a small amount of decomposition or thereabouts), and the resulting conversion products are commingled with the hydrocarbon oil charging stock for the process and the mixture is separated by fractionation into gases and vapors having an end-boiling point of the order of 600 to 650 F. and higher boiling liquid fractions.

The latter are separately cracked at relatively high superatmospheric pressure undermixed phase conditions (70 to 95% vapor generation at the outlet of the cracking coil) to produce substantial quantities of gasoline and lower and higher boiling fractions. The conversion products'- of the mixed phase cracking step are separated at substantially reduced pressure relative to that employed in the mixed phase cracking zone into vapors and residual liquid. The residual liquid is recovered as a product of the process and the vapors are supplied to the same` separating zone to which the charging stock and the conversion products of the vapor-phase cracking step' are supplied, whereby their high-boiling components are included in the cradking stock supplied to the mixed phase cracking step and their lower boiling components of 600 to 650 F., or thereabouts, end-boiling point are commingled in this zone with vaporous componentsl of the charging stock and of the conversion products of the vapor-phase cracking step which have a corresponding end-boiling point.

These commingled vapors are fractionated to condenseV their relatively heavy components as the aforementioned reflux condensate which is supplied to the vapor-phase cracking step and to form a lighter condensate consisting essentially of heavy gasoline fractions. This latter condensate is reformed under cracking conditions of elevated temperature and substantial superatmospheric pressure regulated to produce therefrom high yields of gasoline of improved antiknock value. The resulting reformed products are separated into vapors and residual liquid fractions and the latter are supplied to the same vaporizing and separating Zone towhichthe conversion products of the mixed phase cracking step are supplied, While the vapors are supplied to the aforementioned fractionating zone wherein said reflux condensate supplied to the vapor-phase cracking step and said lighter condensate supplied to the reforming step are derived..

The fractionated vapors of the desired end- .boiling poin't areremoved as the overhead vaporous streamY from this fractionating zone, subjected to condensation and the resulting distillate, which constitutes the high antiknock gasoline product of the process, is separated from the ref of substantially negligible free-carbon content,

is disposed inV furnace 2 and the oil passing through thisl coil is substantially completely vaporized and hea-ted to the desired outlet cracking temperature,` the conditions of temperature, pressure and conversion time in this zone being correlatedto givevonl-y a relatively small amount of cracked products (say 10%, or thereabouts) in the heated products discharged therefrom. These products are directed from coil I through line 3 and valve 4 to separating and fra-ctionating t complished by directly commingling a suitable cooling uid with; conversion products passing through line 3 and may be assisted, when desired, by pressure reduction as the products pass through valve- 4 in thisline'.

I may employ a portion or all of the hydrocarbon oil charging stock for the process as cooling material in line 3 by directing the same from pump 8, to which it is supplied through line and valve l, through line 9, line I0 and valve II into line 3.

vaporous products from the mixed phase cracking step are also supplied to zone 5 and, when desired, may be cooled, as will be later described, and commingled with the vapor-phase cracked products in line 4 to elect a portion or all of the desired cooling of the latter.

The commingled materials supplied to separating and fractionating column 5 are therein separated into an overhead stream of vapors and.

gases, which has an end-boiling point of the order of 600 to 650 F., and bottoms which com` prise the higher boiling components of the commingled materials and which will vary in composition, depending upon the nature of the charging stock employed, but will have an initial boiling point of the order of 600 to 650 F.

The charging stock may be any desired type of hydrocarbon oil ranging from light distillate to crude petroleum, reduced crude or the like and in addition to the aforementioned provision for commingling charging stock with the conversion products being supplied to zone 5, I provide for introducing regulated quantities of the charging oil, when desired, directly into column 5 at any desired point in this zone for. the purpose of assisting cooling and fractionation therein. Line I2 and valve I3, communicating with line 9 and column 5, are provided in the case here illustrated for introducing charging oil directly into the latter zone.

Bottoms from column 5 are directed therefrom through line I4 and valve I5 to pump I6 by means of which they are supplied through line I1 and valve I8 to mixed phase cracking coil I9. This coil is disposed in furnace and the oil passing therethrough is heated to the desired cracking temperature, preferably at substantial superatmospheric pressure, the conditions of temperature, pressure and conversion time in this zone being correlated to produce high yields of gasoline from the oil suppliedithereto under mixed phase cracking conditions. Normally,.from 70 to 95%, or thereabouts, of the conversion products discharged from coil I9 will be in vaporous state and the total vaporous and liquid conversion products may be directed through line 2I, valve 22, line 23 and valve 24 into vaporizing and separating chamber 25 or, when desired, they may rst be supplied through line 26 and valve 21 into reaction chamber 28.

When chamber 28 is employed, it is preferably operated at a relatively high superatmospheric pressure which may be substantially the same or somewhat lower than that employed at the outlet of coil I9. The reaction chamber is preferably insulated to conserve heat, although insulation is not indicated in the drawing, so that the products supplied to this zone, and particularly their vaporous components, are subjected toappreciable continued cracking as they pass therethrough. Both vaporous and liquid conversion products are withdrawn in commingled state from the'lower portion of chamber 28 and directed through line 29, valve 30, line 23 and valve 24 into vaporizing and separating chamber 25.

Chamber 25 is operated at a substantially reduced pressure relative to that employed at the outlet of coil I9 and also at a substantially lower pressure than that employed in chamber 28, when the 'latter Zone is utilized,` whereby the liquid conversion products supplied to this zone are appre ciably further vaporized, leaving a relatively heavy liquid residue which is removed from the lower portion of the chamber through line 3I and valve 32 to cooling and storage, or elsewhere, as desired.

The vapors supplied to and evolved in chamber 25 are separately removed from this zone through line 33 and they may be supplied directly through valve 34 in this line and through line 3 to separating and fractionating column 5 or, when desired, they may first be cooled by passing the same through cooler 35 which communicates with line 33 through lines 36 and 38 controlled by the respective valves 31 and 39.

The relatively clean vapors from the upper portion of column 5 which, as previously mentioned, have an end-boiling point of the order of 600 to 650 F. and which include vaporous and gaseous components of this end-boiling point derived from the total commingled materials supplied to column 5, are directed through line 46 and valve 4I to fractionator 42 wherein they undergo fractionation in commingled state with vaporous products of the reforming step of the process, which latter are supplied to the fractionator, as will be later described. The heavy components of the commingled vapors are condensed in fractionator 42 to form the aforementioned relatively clean cracking stock supplied to coil 2 and, in the preferred embodiment of the invention, this material has an end-boiling point of the order of 600 to 650 F. and contains only a negligible amount of free carbon (for example, 0.01%, or less, as determined by the Conradson test). The Ivapor-phase cracking stock is direoted from fractionator 42 through line 43 and valve 44 to pump 45 which supplies the same through line 46 and Valve 4T to cracking coil I.

Components of the vapo-rs supplied to fractionator 42 of lower boiling characteristics than the materials supplied to coil I are further fractionated to form a light overhead vaporous stream Vconsisting essentially of normally gaseous products and light gasoline fractions of high antiknock value (such as, for example, those boiling up to approximately 250 tol 350 F., or thereabouts) and form a light condensate which consists essentially of heavier gasoline fractions. This light condensate may have an initial boiling point ranging, for example, from 200 to 300 F., or thereabouts, and an end-boiling point of from 400 to 450 F., or thereabouts, and is directed from the fractionator through line 48 and valve 49 to pump 50 by means of which it is supplied through line 5I and valve 52 to reforming coil 53.

The reforming coil is disposed in furnace 54' and the light condensate passing through this zone is heated under cracking conditions of elevated temperature, substantial superatmospheric pressure and conversion 'time regulated to produce therefrom high yields of lighter gasoline fractions of materially improved antiknock Value. The resulting conversion products are directed from Icoil 53 through line 54'and valve 55 into separating chamber 56 and preferably'oooled in any desired well knownmanner prior to their introductioninto the latter zone sufliciently to prevent their .excessive further conversion. As an Yexample of Yone specific means of accomplishing this, line 51, having valve 58 and communicating with line 54, is provided in the case here illustratedfor directly commingling a Vsuitable cooling cil withthe stream oi conversion products passing through line 54 and', when desired, cooling'may' alsobe assisted Iby substantially reducing the pressure on. the stream of conversion products as theypass. through valve 55 in line 5.4.

' The temperature and pressure condi-tions. employedxinv chamber 56. are regulated tio-.separate the materials supplied thereto into relatively clean vapors which include gases, gasoline. fractions and materials boiling up to approximately` 600 to 650 F., and leave the higher boiling com.- ponents of the materials supplied to chamber 56 in liquid state. The relatively clean vapors: are. directed from chamber 56 through line 51S and valve 58 to fractio-nator 42 wherein they are subjected to fractionation, as previously described and the residual liquidis separately removed from chamber 56 and directed therefrom; through. line 59 and valve 601 to pump. 5l. and: thence through line 62 andvalve 63 into-separating chamber 25":4 wherein their heavy com'- ponents commingle with the.- residual. liquid fractions removed from this zone through line 3l` and valve 32, while their lower boiling components are vaporized and supplied with the other vaporous fractions from this zone to. column 5. Pump 6l may be omitted when chamber 56 is operated at higher pressure than that employed in chamber 25.

The overhead vaporous stream resultingv fromfractionation in fractionator 42 is directedv therefrom through line 64 and valve 55to1 condensation and cooling in condenser 55 Wherefrom the resulting distillate and uncondensed gases are directed through line 61 and valve 68. to` collection and separation in receiver 69. The uncondensed gases are removed from the` re ceiver through line lil and valve 'H and directedl to storage or elsewhere, as desired. Distillate collected in receiver 69, which comprises the;

nal motor fuel product of the process and consists of gasoline fractions of `high antiknock value having an end-boiling point of the order of 250 to 350 F., or thereabouts, is supplied from receiver 6| through line 12 and valve 13 to storage or to any further desired treatment.

When desired, regulated quantities of the distillate collected in receiver 69 may .be returned by well known means, not illustrated in the drawing, to the upper portion Vof fractionator 42 to serve as a cooling and reiiuxing medium in this zone and it is also within the scope of the invention, when desired, to utilize this material for cooling the conversion products of the re forming operation in line 54 by supplying the same thereto through line 51 and valve 58.

It will, of vcourse, be understood that any Well known expedients for regulating temperatures at various points in the system and for controlling the boiling range characteristics of the intermediate liquid products, such as, for example, the vapors removed from chamber and from chamber 56, may be employed in conjunction with the means illustrated. For example, suitable fractionating means such as bubble trays, perforated pans or the like may be provided in the upper portion of chamber 56 and a suitable cooling and refiuxing. medium such as, for example, a portion of the light condensate from fractionator 42 may ybe supplied at the desired temperature to the upper portion of this zone as a cooling and refluxing medium. Likewise, light or heavy condensate from fractionator 42 may `be supplied at the desired temperature to the upper portion of column 5 as a cooling and refluxing medium. Similar cooling means. may alf.- so. be employed in chamber 25 to control: the characteristics of the vapors` and the residual liquid products separated in. this zone4 and. coolfl ing may be. employed, when desired, in line 23 in any well known manner, not illustrated Asan example of one specific operation of the process herein provided, employing ascharging oil a. Muskegon topped crude, the condensate supplied to the. vapor phase cracking coil has an end-boiling point of approximately 650 F; and is heated: therein to an outlet temperature'ot' approximately 1000. F. with. a superatmospheri'c pressure at this point in the system of approximately 150 pounds per square inch. Substantially the' same pressure is employed in the succeeding separating and fractionating column and the top temperature of the latter zone is .maintained. at. approximately 709 F., a portion of the chargingoilbeing supplied to the.v fractionating section. of this zone and another'port'on thereof being commingled with thestreanrofr conversion products passing to the'. separating section of this zone from the vapor-phase cracking coil.

The mixed phase cracking coil, tov which bottoms. from the aforementioned separating .andi fractionating column are supplied, is operated with. an outlet. temperature of approximately 935" F. and an. outlet pressure of approximately 200 pounds per square inch. The succeeding reaction chamber is operated at substantially the same pressure and. both vaporous andY liquidconversion products from this zone are supplied tol the reduced pressure vaporizing and' separating chamberiwhich isoperated at a superatmosphericpressure of approximately '75 pounds per square inch, the conversion products being cooled toa. temperature of approximately 850 F. prior tok their introduction into thisA zone, While the temperature of the -vaporous stream leaving this'y zone is maintainedat 'approximately 780 F.V andi further cooled prior to'v its introduction into the separating and fra'ctionating column to which f the charging stock and products of the vaporphase cracking operation are supplied.

The fractionator from which the condensate supplied to the vapor-phase cracking operation and the lighter condensate supplied to the reforming operation are derived, is operated at a superatmospheric pressure of approximately pounds per square inch and said light condensate supplied to the reforming operation has a boiling range of approximately 220 to 450 F. This material is heated in the reforming coil to an outlet temperature of approximately 1025 F. at a superatmospheric pressure, measured at the outlet of the coil, of approximately '750 pounds per square inch and the resulting heated products are cooled prior to their introduction into the succeeding separating chamber to a temperature of approximately 760 F., this separating chamber being operated at a superatmospheric pressure of about 100 pounds per square inch and the temperature of the vaporous stream removed therefrom and supplied to the fractionator be' ing maintained at approximately 685 F., the liquid products from this zone being supplied to the aforementioned reduced pressure vaporizing process 4comprise about 32%, based on the charg-Y ing oil, of residual liquid of good fuel oil characteristics and uncondensed gases which contain a high proportion of polymerizable olens.

It will be understood, of course, that the temperature and pressure conditions given in the foregoing example may be varied considerably, depending upon the type of charging stock undergoing treatment and the desired quality of the final residual liquid and gasoline products, and it is Within the skill of one familiar with the cracking art to vary the operating conditions to suit requirements. Such changes do .not .constitute a departure from the invention so long as its teachings with respect to thev characteristics of the cracking stocks supplied to the vapor phase cracking step are observed While maintaining mild vapor-phase cracking conditions in this zone, mixed phase cracking conditions in the heavy oil cracking step of the systemfand reforming conditions in the cracking step to which the lighter condensate is supplied.

I claim as my invention:

1. A hydrocarbon oil conversion process which comprises introducing cracked vapors and charging oil for the process to a separating and fractionating zone, therein separating a vaporous product having` an end-boiling point of from about 600 to 650 F. and a heavier liquid product, further fractionating said vaporous product in a second fractionating zone to form a light gasoline fraction of high anti-knock value, a heavy gasoline fraction of relatively low anti-knock value, and a reux condensate heavier than gasoline having an end-boiling point of from about 600 to 650 F., subjecting said reux condensate to relatively mild vapor phase cracking such as to effect not substantially in excess of 10% decomposition thereof per pass through the cracking zone, introducing the resultantproducts to said separating and fractionating zone, subjecting said heavier liquid product to mixed phase cracking under conditions yadequate to produce therefrom a greater quantity of gasoline than is formed by said vapor phase cracking, introducing vaporous products of the mixed phase cracking step to said separating and fractionating zone, independently subjecting said heavy gasoline fraction to cracking conditions adequate to enhance the anti-knock value thereof, and supplying resultant vaporous products to said second fractionating zone.

2. A hydrocarbon oil conversion process which comprises introducing cracked vapors and charging oil for the process to a separating and fractionating zone, therein separating a vaporous product having an end-boiling point of from about 600 to 650 F. and a heavier liquid product, further fractionating said vaporous product in a second fractionatingl zone to form a light gasolinefraction of high anti-knock value, a heavy gasoline fraction of relatively low anti-knockY value, and a reflux condensate heavier than gasoline having an end-boiling point of from about 600 to 650q F., subjecting said reflux condensate to relatively mild vapor phase cracking such as to effect not substantially in excess of 10% decomposition thereof per pass through the cracking zone, introducing the resultant products to said separating and fractionating zone, subjecting said heavier liquid product to mixed phase cracking under conditions adequate to produce therefrom avgreater quantity of gasoline than is formed by said vapor phase cracking, separating the mixed phase conversion products into vapors and residue in a reduced pressure vaporizing zone, introducing the vapors to said separating and fractionating zone, independently subjecting said heavy gasoline fraction to cracking conditions adequate to enhance the anti-knock value thereof, and supplying resultant vaporous products to said second fractionating zone.

3. The process as defined in claim 2 further characterized in that liquid products of the-heavy gasoline reforming step are introduced to said reduced pressure vaporizing zone to commingle with the residue separated therein.

JEAN DELATTRE SEGUY.

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