US2271095A - Treating hydrocarbon oils - Google Patents

Description

J. K. ROBERTS I 2,271,095 TREATING HYDROCARBON OILS Filed Dec. 29, 193'? \NYENTOR JDSE PH K. ROBERTS /Zak N W ATTORNEY Patented Jan. 21, 1942 Joseph K. Roberts, Flossmoor, 111., m! to Standard Oil Company, Chicago, 111., a corporation of Indiana Application December 29, 1937,Serial No. 182,191 7 Claims. (01. 196-49) This invention relates to methods of treating hydrocarbons to convert higherboili-ng hydrocarbons into lower boiling hydrocarbons.

According to this invention a charge of relatively heavy oil is passed through a heating zone or coil wherein it is heated to a cracking temperature and maintained under atmospheric pressure or slightly greater, and the heated products are then passed to a coking chamber or drum maintained at acoking temperature wherein vapors are separated and heavy constituents are decomposed by the contained heat of the heated products into vapors and a coke residue which col ects in the coking chamber or drum. Vapors in iuding the vapor products formed by the coking action in the coking chamber pass upwardly in the coking chamber and are passed to a fractionating tower wherein they are fractionated to separate heavy condensate oil such as a heavy gas oil and light reflux condensate such as a light gas oil from a light distillate containing gasoline constituents.

The heavy condensate oil separated from the vapors leaving the coking chamber or drum is passed through a viscosity breaking zone wherein it is maintained under superatmospheric pressure and at an elevated temperature to produce a relativelyv large yield of intermediate constitutents suitable for further cracking to produce gasoline constituents. The products leaving the viscosity breaking zone are separated into liquid residue and vapors, the vapors being fractionated to separate a heavy condensate oil such as a heavy gas oil which is preferably recycled through the viscosity breaking zone for further cracking, from lighter fractions which are subjected to further cracking.

A portion or all of the liquid residue separated from the viscosity broken products may be introduced into a vacuum flash tower maintained under subatmospheric pressure to separate a heavy flash distillate fromliquid residue. The heavy flash distillate is mixed with the charge passing to the viscosity breaking zone for further cracking treatment therein. a

The light reflux condensate separated from the vapors leaving the coking drum or chamber and the lighter fractions separated from products derived from the viscosity breaking operation are subjected to cracking and are advantageously put into a common fractionating tower wherein they contact hot vapors and the heavier portions of the latter vapors are condensed and the lighter portions of the introduced reflux contioned fractionating zone is passed through alight distillate are vaporized. The vapors from the fractionating zone last mentioned are condensed to produce a light distillate having the desired boiling range. The condensate oil containing unvaporized fractions from the last mencracking zone or coil wherein it is maintained under suitable cracking conditions. The products fromthe cracking operation are passed'to an evaporator or separating zone to separate vapors from liquid residue, the hot vapors being introduced into the last mentioned fractionation zone for contact with the introduced light reflux condensate and relatively light distillate.

In the drawing there is represented a diagrammatic illustration showing apparatus suitable for practicing the process of the invention;

Referring now to the drawing, the reference character ll designates a pump for forcing a relatively heavy'charging oil through a line I 2 and through heating zone or coil II in a furnace or heater l6 wherein the heavy oil is raised to a cracking temperature and is maintained under atmospheric pressure or a pressure slightly greater than atmospheric. The heavy oil is passed through the heating zone or coil I 4 at a velocity suflicientto prevent excessive deposition of coke therein. The heated products are passed through line I8 into a coking chamber or zone 20 maintained at a suitable coking temperature. While only one coking chamber has been shown in the drawing it is to be understood that a plurality of such coking chambers is preferably used. The heated oil passing through line It may be passed through the branch lines 2|, 22 and 24 into the coking chamber 20.

In the coking chamber 20 the heated products are separated into vapors and residue and heavy constituents are decomposed by the contained heat of the heated products into vapors and a coke residue which collects in the cokin chamher. The coke residue may be withdrawn in any wardly through line 2| into a fractionating tower densate and the lighter fractions or relatively '30 wherein the vapors are fractionated to separate heavy condensate oil such as a heavy gas oil and light reflux condensate such as a light gas oil from a light distillate containing gasoline constituents. The vapors pass overhead through line fl'and are cooled and condensed by passing through condenser 84, the distillate being collected in a. receiver 18 having a valved gas outlet 38 and a valved liquid outlet 40.

The light reflux condensate collects on trapout tray 42 having a hood 44. The light reflux condensate is withdrawn from trapout tray 42 and is preferably passed through line 46 by pump 48 into the fractionating tower 50 wherein it contacts hot vapors from a separate cracking operation as will be more fully described hereinafter. The heavy condensate oil is withdrawn from the bottom of the fractionating tower 30 and passed through line 52 by pump 54 through a viscosity breaking zone or coil 56 in heater or furnace 58. In its passage through the viscosity breaking zone or coil 56 the heavy condensate oil is maintained under superatmospheric pressure and at an elevated temperature to produce a relatively large yield of intermediate constituents suitable for further cracking to produce lower boiling hydrocarbons containing gasoline constituents.

The products leaving the viscosity breaking zone or coil 56 are passed through line 60 preferably having a pressure reducing valve 62 into an evaporator or separating zone 64 of the combined evaporator and fractionating tower. 66 to separate vapors from liquid residue. The vapors pass upwardly and are fractionated in the fractionating section 61 of the combined evaporator and fractionating tower 66 to separate heavy reflux condensate from lighter constituents. The vapors remaining after fractionation are passed through line 68, are cooled and condensed by passing through condenser I and the distillate which contains light gas oil and gasoline constituents is pumped through line 12 by pump I4 and preferably into the fractionating tower 50 wherein it contacts hot vapors from a separate cracking operation as will be later described in more detail.

The heavy reflux condensate collects on trapout tray I6 having a hood .18 and is withdrawn therefrom and passed through line 80 by pump 82 and is preferably recycled through the viscosity breaking zone or coil 56.

All or a portion of the liquid residue collecting on the bottom of the evaporator or separating zone 64 is withdrawn therefrom and passed through line 06 into a vacuum flash tower 88 maintained under subatmospheric pressure to further separate vapors from a liquid residue, the liquid residue being withdrawn through line 89. The vapors pass overhead through line 90 .and are cooled and condensed by being passed through condenser 92 to form a heavy flash distillate which is collected in receiver 94. The receiver 94 has a vapor line 96 provided with a pump 98 for maintaining subatmospheric pressures in the vacuum flash tower 88'. Instead of a pump, other means for maintaining subatmospheric pressures may be used such as a barometric condenser. The heavy flash distillate is withdrawn from the bottom of the receiver 94 and is passed through line I00 by pump I02 and is mixed with the heavy condensate oil passing through line 52 and then passed through the viscosity breaking zone or coil 56 for further v relatively light distillate introduced into the fractionating zone through line I2 and light reflux condensate introduced into fractionating zone 50 through line 46. In the fractionating zone or tower 50 some of the lighter constituents of the light reflux condensate and relatively light distillate are vaporized and some of the heavier constituents of the introduced hot vapors are condensed to form reflux condensate. The vapors remaining after fractionation pass through line I06 and condenser I08, the distillate being collectedin receiverv I I I having a valved gas outlet I I2 and a valved liquid outlet 4. The distillate contains gasoline constituents and has the desired boiling range.

The condensate oil collecting at the bottom of the fractionating tower 50 is withdrawn therefrom and passed through line H8 by pump I and through a cracking zone or coil I22 in furnace or heater I24 wherein it is maintained under superatmospheric pressure and at an elevated temperature in order to effect the desired extent of cracking. The cracked products leave the cracking zone or coil I22 through line I26 having a pressure reducing valve I20 and are introduced into the evaporator or'separating zone I04 to separate vapors from liquid residue. A quench oil may be introduced through line I29. The liquid residue is withdrawn through line I and the vapors are passed through line I05 into the fractionating tower as above described. While the light reflux condensate from trapout tray 42 and relatively light distillate passing through line 12 are advantageously introduced into the fractionating tower 50, they may be directly introduced into the cracking zone I22 either as single streams or as a combined stream for further cracking.

A typical operation of one embodiment of the invention will now be given but it is to be understood that thc invention is not restricted thereto. A relatively heavy charging oil such as reduced crude oil or other residual or heavy oil is passed through the heating coil or zone I4 wherein it is heated to about 840 to 950 F. and maintained under a pressure from atmospheric to about pounds per square inch. The heated products are introduced into the coking chamber 20 which has preferably been preheated to at least 650 F. and preferably higher. The coking chamber 20 is preferably insulated to prevent heat loss. The coking chamber 20 during the operation is maintained under a pressure from atmospheric to about 60 pounds per square inch and at a suitable coking temperature of about 780 to 840 F. by the contained heat of the heated products. In the coking chamber vapors are separated from residue and heavy constituents are decomposed by the contained heat of the heated products into vapors and coke residue.

The vapors from the coking chamber are fractionated. in the fractionating tower 30 to separate heavy condensate oil from light reflux condensate. The heavy condensate oil is passed through the viscosity breaking zone or coil 56 wherein it is maintained under a pressure of about/" to 500 pounds per square inch, preferably about 400 pounds per square inch and at a temperature of about 850 to 950 F., preferably about 940 F. The heavy condensate oil is maintained under these conditions for the desired period of time to effect conversion into a relatively large yield of intermediate constituents suitable for further cracking into lower boiling hydrocarbons containing gasoline constitu ents. Heavy reflux condensate from trapout tray 16 and heavy flash distillate from receiver 94 are preferably mixed with the heavy condensate oil passing through the viscosity breaking zone or coil 56 for further cracking treatment along with the heavy condensate oil.

The products leaving the viscosity breaking zone or coil 66 are passedtc'the evaporator or separating zone 04 of the combined evaporator and fractionating tower which is maintained under a pressure of about to 50 pounds per, square inch. The viscosity broken products are separated into liquid residue and vapors, the vapors being fractionated to separate heavy remeats, passing the products from said vast, v breaking zone to a separating sons to separateevaporator or separating zone 04 is passed to the vacuum flash tower 88 which is maintained under an absolute pressure of about '70 mm. to

further separate vapors from liquid residue.

The separated vapors are cooled and, condensed to form a heavy flash distillate, which is returned through line I00 for passage through the viscosity breaking .zone or coil 56 to produce anadditional amount of intermediate constituents suitable for further cracking to produce gasoline constituents. s I

The condensate oil from the bottom of the fractionating tower 50 is passed through the cracking zone or coil I 22 wherein it 'is maintained under a pressure of about 200' to 1000 pounds per square inch, preferably about 750 pounds per square inch and at a temperature of about 925 to 1100? F., preferably about 975 F. to effect the desired extent of cracking. The cracked products are passed to the evaporator or separating zone I04 which is maintained under a pressure of about 200 to 300 pounds per' to a second separating zone wherein separation square inch to separate vapors from liquid residrawing, it will be understood that reflux liquid is usedduring the-fractionation of the vapors. in the fractionating towers according to well known fractionating practice.

While one embodiment of the invention has been described, it is to be expressly understood that the invention is not restricted thereto and various modifications and adaptations thereof may be made without departing from th spirit of the invention. i

I claim: I

1. A process for converting higher boiling hydrocarbon oil into lower boiling hydrocarbons which comprises primarily heating a crude oil residual stock to a cracking temperature, passing the heated products to a coking zone maintained at a coking temperature wherein vapors are separated from coke residue, fractionating vapors separated in said coking zone in a flrst iractionating zone to-separatea heavy condon sate comprising heavy gas oil from lighter reflux condensate comprising light gas 0.11, passing the heavy condensate oil through a viscosi y breaking zone wherein it is maintained under vapors from liquid residue, fractionsting the last mentioned vapors in a second fra'otionating zone to'separate heavy condensate 011 comprising heavy gas oilfrom-a relatively light distillate comprising light gas oil, recycling the last mentioned heavy condensate oil through said viscosity breaking zone, heavier constituents from said li hter reflux condensate and relatively light distillate and-passing suohheav ier constituents through a cracking zone where'- in they are maintained under superatmospheric pressure and high temperature conditions to eflect the desired extent of cracking into lower boiling hydrocarbons, passing the resultant cracked products from the latter cracking zone of vapors from liquid residue takes place, passing the resultant separated vapors to a third fractionating zone wherein the vapors are fractionated to recover a light distillate having th desired boilingrange.

2. A process as defined in claim 1 wherein at least a portion of the liquid residue derived from products leaving said viscosity breaking zone is passed to a vacuum flash zone maintained under vsubatmospheric pressure to further separate vapors from liquid residue, the vapors cooled-to form a heavy flash distillate and such heavyflash distillate directed to said viscosity breaking zone.

' 3. A process for converting higher boiling hy.--

drocarbon oil into lower boiling hydrocarbons which comprises primarily heating a crude oil residual stock to a cracking temperature, passing the heated products to a coking zone wherein the heatedproducts are maintained at a coking temperature by their contained heat to form vapors and coke residue, fractionating the vapors separated in said coking zone to separate a heavy c0ndensate oil from light reflux g-condensate, passing the heavy condensate oil through a viscosity breaking zone wherein it is maintainedundersuperatmospheric pressure and relatively high temperature conditions to produce a relatively high yield of intermediate constituents suitable for further cracking to produce gasoline constituents', passing the products from said viscosity breaking zone to a separating zone to separate vapors from liquid residue, fractionating the last mentioned vapors to separate heavy condensate oil from a relatively light distillate, recycling the last mentioned heavy condensate oil through said viscosity breaking zone, passing the light reflux,

separately from the other fractionating steps 'superatmospheric pressure and relatively high' temperature conditions to produce a relatively high yieldof intermediate constituents suitable for further cracking to produce gasoline constiherein specified to separate a light distillate having the desired boiling range from condensate. oil, passing liquid residue derived from products leaving said viscosity breaking zone to a vacuum I flash zone maintained under subatmcspheric pressure to further separate vapors from liquid residue, cooling'the vapors to form a heavy flash distillate and directing such'heavy flash distillate to said viscosity breaking acne.

4. A process for converting higher boiling hydrocarbon oil into lower boiling hydrocarbons which comprises primarily heating a crude oil residual stock to a cracking temperature, passing the heated products to a coking zone wherein the heated products are maintained at a coking temperature to effect conversion into a coke residue,

fractionating the resultant vapors separated in said coking zone to separate a heavy condensate comprising heavy gas oil from lighter reflux condensate comprising light gas oil, passing the heavy condensate to a viscosity breaking zone wherein it is subjected to cracking conditions of temperature and pressure to effect conversion into a relatively high yield of intermediate constituents suitable for further cracking to produce gasoline constituents, passing the products from said viscosity breaking zone to a separating zone to separate vapors from liquid residue, passing said liquid residue to a vacuum flash zone wherein the residue is subjected to distillation under subatmospheric pressure to form a heavy vacuum flashed distillate, directing such heavy vacuum flashed distillate to said viscosity breaking zone, fractionating aforesaid vapors separated from the viscosity broken products to separate heavy condensate oil from lighter fractions comprising light gas oil constituents, combining lighter reflux are fractionated separately from the other fractionating steps herein specified to recover a desired gasoline product. 1

5. A process for converting higher boiling hydrocarbon oil into lower boiling hydrocarbons that comprises primarily heating crude oil residual stock to a cracking temperature and passing the heated products to a coking zone wherein the heated products are maintained at a coking temperature to form vapors and coke residue, fractionating the vapors separated in said coking 'zone to separate heavy condensate comprising heavy gas oil from lighter condensate comprising light gas oil, passing the heavy condensate to a viscosity-breaking zone wherein it is subjected to cracking conditions of temperature and pressure to produce a relatively high yield of intermediate constituents suitable for further crack-I ing to produce gasoline constituents, passing the products from said viscosity breaking zone to a separating zone to separate vapors from liquid residue, passing said liquid residue to a vacuum flash zone wherein the liquid residue is flash-distilled under subatmospheric. pressure to form a heavy vacuum-flashed distillate and directing such vacuum flashed distillate to said viscositybreaking zone, passing the separated vapors from said separating zone to 'a fractionating zone wherein the vapors are fractionated to separate heavy condensate from lighter fractions comprising light gas oil, cycling said heavy condensate to said viscosity-breaking zone, directing the aforesaid lighter condensate obtained in the fractionation of the vapors derived from the coking operation and said lighter fractions obtained in the fractionation of the vapors derived from the viscosity-breaking operation comprising light gas oil to a separate fractionating zone in contact with vapors therein and wherein fractionation takes place to separate light distillate of desired drocarbon oil into lower boiling hydrocarbons that comprises primarily heating crude oil residual stock to a cracking temperature and passing the heated products to a coking zone wherein the heated products are maintained at a coking temperature to form vapors and coke residue, fractionating the vapors separated in said coking zone to separate heavy condensate comprising heavy gas oil from lighter condensate comprising light gas oil, passing the heavy condensate to 'a viscosity-breaking zone wherein it is subjected to cracking conditions of temperature and pressure to produce a relatively high yield of intermediate constituents suitable for further cracking to produce gasoline constituents, passing the products from said viscosity-breaking zone to a separating zone to separate vapors from liquid residue, passing said liquid residue to a vacuum flash zone wherein the liquid residue is flash-distilled under subatmospheric pressure to form a heavy vacuum-flashed distillate and directing such' vacuum-flashed distillate to said viscosity-breaking zone, passing the separated vapors from said separating zone to a fractionating zone wherein the vapors are fractionated to separate heavy condensate from lighter fractions comprising light gas oil, directing the aforesaid lighter condensate obtained in the fractionation of the vapors derived from the coking operation and said lighter fractions obtained in the fractionation of the vapors derived from the viscosity-breaking operation comprising light gas oil to a separate fractionating zone in contact with vapors therein and wherein fractionation takes place to separate.

light distillate of desired boiling range from higher boiling condensate, passing said higher boiling condensate to a cracking zone wherein it is subjected to cracking conditions of temperature and pressure to effect conversion into gasoline constituents, separating the resultant cracked products from the latter cracking zone into yapors and residue and passing the separated vapors to the latter fractionating zone.

'7. A process for converting higher boiling hydrocarbon oil into lower boiling hydrocarbons that comprises primarily heating cmde oil residual stock to a cracking temperature and passing the heated products to a coking zone wherein the heated products are maintained at a coking temperature to form vapors and coke residue, fractionating the vapors separated in said coking zone to separate heavy condensate comprising heavy gas oil from lighter fractions comprising light gas oil, passing the heavycondensate to a viscosity-breaking zone wherein it is subjectedto cracking conditions of temperature and pressure to produce a relatively high yield of intermediate constituents suitable for further cracking to produce gasoline constituents, passing the products from said viscosity-breaking zone to a separating zone to separate vapors from liquid residue. Passing said liquid residue to a vacuum flash zone wherein the liquid residue isflash-distilled under subatmospheric pressure to form a heavy vacu- .um-flashed distillate and directingsuch va'cuum-fiashed distillate to said viscosity-breaking 1 'zone,- passing the separated vapors from said separating zone to a fractionating zone wherein the vapors areiractionated to separate heavy condensate from lighter fractions comprising light gas oil, subjecting lighter fractions comprising light gas oil, obtained in the fractionation of both the vapors derived from the coking zone and the vapors derived from the viscosity-breaking zone, to cracking conditions of temperature and pressure entirely separately from said coking and viscosity-breaking zones to eflect conversion into gasoline constituents, and fraetionating the resultant cracked products entirely separately from the fractionation of the products formed in said 10 coking and viscosity-breaking operations.

JOSEPH K. ROBERTS.

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