US2216683A

US2216683A - Treatment of hydrocarbon oil

Info

Publication number: US2216683A
Application number: US166492A
Authority: US
Inventors: Jr George Armistead
Original assignee: Gasoline Products Co Inc
Current assignee: Gasoline Products Co Inc
Priority date: 1937-09-30
Filing date: 1937-09-30
Publication date: 1940-10-01
Anticipated expiration: 1957-10-01

Description

Oct. l. 1940. s. ARMISTEAD, JR 2,216,683

TREATMENT OF HYDROCARBON OIL Filed sept. so, 1937 v 4Z' 601111,51? A.

INVENTOR GEO/ ARM/571590, .r/r.

ATTORNEY Patented Oct. l, 1940 n UNITED STATES TREATMENT OF HYD'ROC'ABBON OIL George Armistead, Jr., Scarsdale, N. Y., assignor to Gasoline Products Company, Inc., Newark, N. J'., a corporation of Delaware Application September 30, `1937, Serial No. 166,492

' 3 claims. (o1. 19e- 67) This invention relates to the art of converting higher boiling hydrocarbons into lower boiling hydrocarbons. L

According to my invention the heat necessary to effect the desired extent of cracking of a heavy oil and drastic cracking ofa relatively clean oil is supplied by burning a residual oil or the like and mixing the hot products of combustion directly with the oils to be cracked so as to utilize a substantial part of the heat thus generated. One of the reasons why prior processes in which air is injected into a large bodygof oil in a large vessel have not been successful is because of the objectionable deposition of coke. 'In one step of my process the oil and oxygen-containing gas are passed through a narrow and conned passageway, and in this way objectionable coking is rovercome as there is a continualmovement of oil past the nozzle. My invention may also employ an oxygen-containing gas richer in oxygen than air, in fact, pure oxygenitself and with the presence of fless inert diluent gas at the point of combustion, higher localized temperatures are obtained with consequent improvement in oil de- 25. composition rate and character of products.

In one form of the invention a heavy oil is burned with oxygen or with an oxygen-containing gas and the hot products of combustion, preferably separated from unburned heavy oil, are di- 30 rectly mixed with a relatively clean cil stock to be cracked to' raise the temperature of the clean oil stock to an active cracking temperature. The combined stream yis then passed through'a cracking coil-or zone wherein the oil to be cracked is 35 maintained under superatmospheric pressure and a high temperature for a suicient time to effect n the desired cracking.

The stream of cracked products` leaving the cracking zone is then passed 'under a lower pressure to an evaporator or separatingzoner where hot vapors are separatedfrom cracked residue. Before being passed to the evaporator, the stream of cracked products may be mixed with products coming from another cracking zone as will be hereinafter described. The hot vapors passupwardly inthe evaporator Lor-separating zone and are contacted with a relatively heavy fresh charging oil, suchas reduced crude oil, and in this way some of the hot vapors are condensed to form a heavy reux condensate and some of the lighter constituents of the relatively heavy oil are vaporized. t

The unvaporized fractions of the heavy charging oil and the heavy reilux condensate are collected and a portion thereof may be burned with oxygen or with an oxygen-containing gas, there being insuiiicient oxygen to consume all of the oil. By this combustion the temperature of the heavy oil and reflux condensate is raised and the heavy oil and reux condensate are subjected to any degree of cracking varying from a mild conversion directed at the reduction of viscosity and formationv of gas oils from the residuals to the formation of a large yield of gasoline. The products of this treatment are discharged into a separator in whichk they may be separated into vapors and a liquid residue. The vapors are passed to the evaporator or separating zone above mentioned and the liquid residue under reduced pressure is mixed with the stream of cracked products leaving the rst mentioned crackingV zone, the latter combined stream also being introduced into the evaporator or separating zone above described. However, they separator may be bypassed and all the products of this treatment may be mixed with the cracked products leaving the rst mentioned cracking zone and the combined stream then passed to the evaporator or separating zone.

The vapors remaining after contact with the, relatively heavy charging oil are fractionated to separate a reflux condensate of the nature ofgas oil from vapors of the desired boiling'range. The

gas oil condensate thus separated'may form the feed stock to the clean oil cracking zone hereinbefore mentioned. The vapors of the desired boiling range arefurther treated to separate water and carbon dioxide from the gasoline product in any suitable manner. t

In the drawing I haveshown a diagrammatic flow sheetof apparatus adapted for practicing my invention.

Referring now t'o the drawing, the main parts of the apparatus comprise a combustion chamber or zo'ne Il), a cracking zone I2, another 'cracking-zone I4, a combined evaporator and fractionating zone I6 and a secondary fractionating zone I8 which may-be of bubble tower construction. Pipe lines, pumps and other means are included whereby the methods of my invention may be carried out. The heavy oil collecting at the bottom of the combined evaporator andfractionating zone I6 comprises cracked residue as will be later described in more detail. The cracked residue is withdrawn throughline 22 and a portionthereof is passed through line 24 byv pump 26 and introduced into the combustion zone lil where it is' mixed and burned with oxygen or an oxygen-containing gas introduced through .line 28 bypump 32. By regulating the opening of valve 33 any desired portion or all of the heavy cracked oil passing through line 22 may be pumped through line 24.

The heavy oil is burned during its passage through the combustion zone ID which is of proper construction to obtain the desired Contact between the oil and oxygen or oxygen-containing gas and to -permit the required burning. Types of combustion zones may include nozzle mixers, refractory lined extended passages or the like. The proportion of oil to oxygen may be such that a portion or all of the oil is consumed. The hot vapors and products of combustion thus formed may be passed through line 34 lto a separator 35 wherein any liquid residue is yseparatedfrom hot products of combustion and is withdrawn through line 35, the vaporous products and gases of combustion being passed through line 38. However, the separator 35 may be omitted, if desired, in which case all of the products leaving the com- .bustion zone IIJ are then passed through-line 38. Where all the oil Iintroduced into zone Il! is burned, high temperatures are obtained andit will be necessary to vconstruct the separator 35, if one is used, and lines 34 and 38, as well as the zone I0, of refractory material to withstand such high temperatures. yIn addition I may cool the hot products of combustion inthe zone I 0 by introducing cool gases through line 39, the gases f.' being recovered during the operation of the process as will be later explained. Or the separator 35, lines 34 and 38 and the zone I0 may be internally insulated to protectv the internal surfaces thereof from the high temperatures.

A relatively clean oil stock such as condensate oil takenY from the bottom of the secondary fractionating zone I8, is passed throughfline 40 by pump 4I and is admixed with the hot products of combustion passing through line 38 in order to immediately raise the clean oil stock to an active cracking temperature. The heated oil' is then passed through thecracking zone I2 preferably unred where it is maintained under high temperature and high pressure conditions in order to effect the desired cracking. The crackingzcne may alsolinclude a soaker 42 but this soaker may be of coil `constructionand form a continuation of the cracking coil or zone I2. In some instances it may be desirable toprovide a furnace or heater for the cracking coil or zone I2 andsoaker 42if a coil is used to supplyadditional heat externally thereto. l

The stream of cracked products leaves, the cracknig zone through line 44 having a pressure A reducing valve 46 and is preferably mixed with cracked products cor-ning from the othercracking zone or coil I4 later to be described in `more detail. The combined stream including the cracked products from the crackingzone I2 is passed under lower pressure into the evaporator or separating zone 52l of the combined evaporator` and fractionating tower I6 where a separation into hot vapors and cracked residue takes place. The cracked residue is withdrawn through line 22 and may form part ofthe oil'which is burned in theV and fractionating tower I6 through line 60 in order to preserve the proper quality of the vapors passing through line 6I. If desired, only part of the fresh feed may be introduced into the latter passes of the cracking zone I2 and the rest introduced into the combined evaporator and fractionating tower.

The unvaporized fractions of the heavy oil and the heaxy reflux condensate are withdrawn from the trapout tray 56 fandl are. passed' through line 62 .by pump' 64.1 The stream` of oily passing through line 62 is combinefd with oxygen or an oxygen-containing gas introduced throughline 65 and a portion of the heavy oil is burnedin order` to raise the temperature of the unconsumed'heavy oil. The hot products of vcombustion and'unconsumed he ated heavyl :oil are passed through the coil or zone I4 maintained under appropriate cracking conditions to effect the desired degree of` cracking of the oil. In the preferred method of operation the proportion of oxygen, the temperaturel and the time of digest inthe zone I4 are controlled to give the greatest reduction in viscosity of the residual constituents of the feed and to produce the greatest amount `of comparatively low boiling range gas oil suitable for furthercracking or for withdrawal as a product Whileiit is preferred to use thev coilA I4 which is no ,t' externally fired, in some instances it may bedesirable to provide a furnace'or a heater` for the coil vIII to supply additional heat externally thereto;H The coil I4 may be used to viscositybreak heavy oils other than the Aheavy oil Jtaken fronrthe fractionating section 5,3.l v

`After passing through the zone orf coill I4, the

h ot products of combustionand cracked ,products may be passed through line 66 to a separator 68 and a Acoolingroil may beintroduced through line 59. In the lseparator 68 there is a separation into hot-vapors which. are passed through line I2 having pressure reducingvalve 'i3 into the evaporator orseparating zone52of the combined evaporator and separating ,tower I6, and liquid residue which is withdrawnffrom the bottom of the separator' v68` through lineI' byY pump '16. The liquid residue may then be passed throughline 'I8 having a pressurel reducing vvalve 82 and mixed Withthe stream of cracked products leaving the cracking zone I 2 throug'hline 44 toeffect further Imild cracking joryiscosity breaking o f theliquid residue..A This .latter combined stream is then,v introduced'linto the evaporator or separating *zoney52l .ofggthe combined evaporator and ,fractionatingftower I6 wherein a separation, into hottvapor's and cracked'residue occurs as has been=above

fdescribedLLines

66 and 18 are provided with Valves' so thattheseparator'BB*maybeby-passed in Whi'clievent the products lfrom the cracking coil`jI4-preferably quenched, are passed directly through line, lI8 into evaporatorV 52. AThe separator 68 maybe provided with the necessaryY internalfractionating equipment'lto serve'asan'efiicient fractionator for theproduction of vgas oil as'side streams,

such as at S3, for heating or Diesel oils or similar purposes. i f' Instead of passing all of theunvaporizedportions of the heavy oil and heavy reuxfco'n'densate throughline62, I may pass allor part thereof through'line 8 4 by pump 85"-and introduce the unvaporized portions of the heavy Voil and heavy reflux condensate into the latterpasses of the cracking zone orcoil I2,\or if desired, into the soaker 42. By introducing the heavy oil into the latter passes of cracking Zone or coil I2 or into the soaker 42, the temperature of the `heavy oil is raised to effect viscosity breaking thereof while the cracking of thev oil first introduced into the cracking zone I2 continues. v

The vapors remaining after contact Awith the fresh feed oil introduced intothe fractionating section 53 of the combined evaporator and fractionating tower I6 are passed through line 6I into the bottom portion of the secondary fractionating zone I8 wherein they pass upwardly and are subjected to further fractionation by means of cooling applied to the top of the secondary fractionating zone I8. During this fractionation the fresh gas oil constituents distilled from the fresh feed in fractionating section 53 along withunconverted gasoilcollect at the bottom of the secondary fractionating zone I8 and form the stock withdrawn through line and passed through the main cracking zone I2. Drawoi points'l and 88 may be provided to permit-the withdrawal of gas oil from the system for use as heating and Diesel oils or the like. V

The vapors of the desired boiling range leave the top of the secondary fractionatingzone I8 through line 90, are condensed by passing through condenser 92 andthe distillate is collected in a receiver or drum 94. The distillate collected in the receiver or drum 94 comprises-gasoline and water which may be separated in any suitable mannen' Ythe water being .drawn off through valved line 96 and the gasoline withdrawn through line 91.

through line 98 and are passed to a washing tower I III into which wateror any other suitable solution or medium is introduced through line ||2. YIn the case of Water the carbon dioxide present in the gases will be dissolved and the solution of carbon dioxide is withdrawn from the bottom of the tower IIO through valved line II4. The remaining gases are passed from the top of the tower I I0 through valved line I I6 and may be passed to a suitable recovery plant for :the extraction of contained gasoline.-` All orf a portion of these gases leaving the top of tower IIII may be used for cooling by being introduced into ther combustion Zone I0 through line 39 as above described. The use of comparatively pure oxygen for heating in the coil I4 and combustion zone I0 has the advantage of producing no combustion products-other than carbon dioxide and water which can be readily separated out before the kremaining gases go to the recovery plant thus simplifying the stripping of the gases `in the final steps of the process. y Y

A portion of the gasoline collected inthe receiver 94 may be passed through line ||8 by pump I I9 into the upper portion of the secondary fractionating zone I8 as reflux. As additional refiux some of the liquidnear the top of the secondary fractionating zone .may bewithdrawn through line |20 by pump |22 and passed through heat exchanger |24 and then returned to thetop of the secondary fractionating zone I8 through The gases which are not con-l densed leave the top ofthe receiver ordrum 94v line |26. The 'heat exchanger |24 serves to preheat the fresh feed passing throughfline 54 prior to its introduction intothe fractionating section 53 of the combined evaporator and fractionating tower I6. f

The fresh feed pump |32 and after beingpreheated in heat exchanger I24 `is further preheated by vpassing through heat exchanger |34. The. preheated fresh feed is then passed through line 54 into the fractionating section53 lof lthe combined evaporator and fractionating tower I6.

The part -of 'the cracked residue not used for burning in combustion zone I0 may be combined with the liquid residue passing through line 36 from the `separator 35 and passed through heat exchanger |34 for preheating the fresh feed. The combined residue is then passed through cooler |36 and line |38 to a suitable` receiver. The pump 32 is provided to pump the oxygen or oxygen-containing gas through lines 28 and 65to the combustion zone I0 and cracking coil I4. An example of a typical operation contemplated by my invention will now be given but Iam not to be restricted thereto. `The fresh feed, such as reduced crude oil or other oil, preferably preheatedto a temperature of about 250 to 550 F., is introduced into the top portion of the fractionating section 53 where it contacts the hot vapors therein. The unvaporized fractions of the heavyoil and the heavy reflux condensate are withdrawn from the bottom of the fractionating section 53 at a temperature of about 700 to 800 F., and are mixed with about 2.7 to 3.0 per cent by weight of oxygen or equivalent amount of oxygen-containing gas. A part of the heavy oil mixture is consumed bypassing through coil I4 and thev temperature of the unconsumed oil is raised sufficiently high to effect `mild cracking or viscosity lbreaking thereof. The mixture of hot combustion products and unconsumed oil during its passage through the cracking zone or coil I4 is maintained -under superatmospheric pressure of about 100 to 1000 pounds per sq. in. and a temperature of about 850 to 950 F. for a suflicient time to effect the desired extent of viscosity breaking of the oil.

If the unvaporized fractions of the heavy oil and heavy reflux condensate collected on trapout tray 56 are passed through line 84 and through the latter passes of the cracking coil or zone I2 instead of through the cracking zone I4, they are maintained under vsuperatmospheric pressure of about 400 -to 1000 pounds per sq. in. and at a temperatureof about 850 to 950 F. for a sufficient time to effect the desired extentl of viscosity breaking thereof. A

' Cracked residue is withdrawn fromA the bottom ofthe evaporator or separating zoner 52 of the combined evaporator andl fractionating tower I6 through line 22 and `a portion of this residue is partially or completelyburned in the combustion zone I0. The combined evaporator and fractionating tower I6 is pref erablytmaintained under` superatmospheric pressure, for example, about to 100 pounds. per sq. in. and the crack-ed residue under these Yconditions will be at a ternperatur'e of about '750 to 850"v F. 'The desired portion ofthe cracked residue is mixed with about 320% by weight of oxygen or equivalent amount of oxygen-containing gas and burned by passing through the combustion zone'l. The proportions cf oxygen or oxygen-containing gas and oil to be burned are preferably chosen so that sube, stantially all of. the crackedresidue will be 'con.A

is passed through line 54 byv sumed during the burning. The cracked residue Withdrawn from the evaporator 52 is at a relatively high temperature and when it is combined with the oxygen or oxygen-containing gas, an instantaneous rise in temperature results, the effect of which on the oil may be regulated by the size of the contacting zone as well as the proportion of oil and oxygen. By using a smaller proportion of the oxygen-containing gas, only apart of the cracked residue will be consumed and a lower temperature will be obtained.

After passage through the combustion zone I0 the products are passed to the separator 35 Where vapors are separated from any liquid residue. The liquid `residue is withdrawn through line 36 and is preferably introduced into the line 22 subsequent tothe point of withdrawal of a portion of the cracked residue through line 24. The vapors and hot combustion products from the separator 35 at a temperature of about 1500n to 4000c F.`are passed to the cracking zone or coil I2 where they are mixed with the oil to be cracked.

The oil to be cracked is preferably the condensate oil withdrawn from the bottom of the secondaryfractionating zone I3 which is preferably maintained und-er superatmospheric pressurefor example, about 50 to 100 pounds per sq. in. and under these conditions the condensate oil will be at a temperature of about 550 to '700 F. The condensate oil to be cracked and the hot vapors and combustion products leaving the separator ,35 are adrnixed and the mixture is passed through the cracking zone I2 which is maintained under a high temperature of about 825 to 1125 F. and a superatmospheric pressure of about 400 to 1000 pounds per sq. in. for the desired time to effect the desired cracking of the oil.

'Ihe stream of cracked products is passed from the cracking zone I2 through the soaker 42 into the separating zone 52 of the combined evaporator and separating tower I6 which is under less pressure than the cracking zone I2 and where a separation into vapors and cracked residue takes place. Before being introduced into the evaporato-r or separating zone 52, the stream of cracked products from the cracking zone I2 may be mixed with the cracked products leaving the cracking zone I4, or the stream may be passed directly to the evaporator or separating zone 52.

Known processes in which a large body of oil in a vessel is treated with air are subject to the objection that coking occurs around the air nozzles mounted within the body of oil. After building up to a certain height, pieces of the deposited carbon break off and deflect the air stream. The coke then burns and in this burning localized overheating occurs which is a hazard to the apparatus in which the process is carried out. According to my process the burning of the oil takes place in a confined passageway such as a coil, for example, and objectionable coking with its accompanying hazards is overcome.

In my invention aircr oxygen-containing gas or the like is introduced into a stream of oil passing through the zone I4 by a nozzle so that there is a continuous passage of oil past the nozzle and thepassageway is kept open by the continuous movement of the oil through the zone. If there is any coke formation, it will not be su'icient to stop or impair the operation of the process and ifany pieces of the coke break off they Will be carried along with the oil stream and will not cause local overheating of a portion of the apparatus. Generally, exceedingly high .temperatures will be obtained-in combustion zone I0 and there will be n o objectionable deposition of coke therein. The use of an oxygen-containing gas richer in oxygen than air, moreover, has a tendency to prevent the objectionable deposition of coke because of high combustion temperatures which prevail and form the complete and instantaneous burning of the oil without the formation of decompositionintermediates which are the source of coke formation. A

From the foregoing lit will be apparent that I have disclosed a. new process for converting oils which overcomes the objectionable features of prior known processes.

While I have described a particular embodiment of my invention, it is to be expressly understood that my invention is not restricted thereto, and various modifications and adaptations thereof may be made Without departing from the spirit of my invention.

I claim:

1. A process for converting higher boiling hydrocarbons into lower boiling products that comprises separating resulting cracked products of the process into vapors and residue in a separating zone, passing resultant separated vapors to a fractionating vzone into which charging stock is introduced and wherein fractionation takes place to form separated vapors and a fraction comprising unvaporized charging stock and reflux condensate, passing the separated vapors to a secondary fractionating zone wherein the vapors are subjected to fractionation to form a secondary reflux condensate, withdrawing separated' residue from the separating zone conducting residue so withdrawn to a contacting zone, introducing an oxygen-containing gas into said `contacting zone to effect combustion of at least a portion of the cracked residue, comprising unvaporized charging stock and reflux condensate to aflatter section of said elongated passageway to thereby subject said fraction to cracking, and directing resultant cracked products intoA said separating zone.

2. A process for converting higher boiling hydrocarbons into lower boiling products that comprises separating resulting cracked products of the process into vapors and residue in a separating zone, passing resultant separated vapors to a fractionating zone Vinto which charging stock is introduced and wherein fractionation takes place to form separated vapors and a fraction comprising unvaporized charging stock and reflux condensate, withdrawing separated residue from the separating zone, conducting residue so withdrawn to a contacting zone, introducingan oxygen-containing gas into said contacting zone to effect combustion of at least a portion of the cracked residue, combining resultant gaseousl productsvof combustion with condensate oil to be cracked and passing the mixture through an elongated passageway of restricted cross section maintained under superatmospheric pressure to thereby subject the condensate oil to cracking temperature and effect conversion into lower boiling products, introducing said fraction comprising unvaporized charging stock and reflux condensate to a latter section of said elongated passageway to thereby subject said fraction to cracking and directing resultant cracked products into said separating zone.

3. A process for converting higher boiling hydrocarbons into lower boiling products that comprises separating resulting cracked products of the process into vapors and residue in a separating zone, passing resultant separated vapors to a fractionating Zone wherein the vapors are subjected to fractionation to separate out a condensate, withdrawing separated residue from the separating Zone, conducting residue so withdrawn to a contacting Zone, introducing an oxygen-containing gas into said contacting Zone to elct combustion of at least a portion of the cracked residue, combining resultant gaseous products of combustion vwith said condensate and passing the mixture through an elongated passageway of restricted cross section maintained under superatmospheric pressure to thereby subject the condensate to cracking temperature and eiect conversion into lower boiling products, introducing a residual stock to a latter section of said elongated passageway to thereby subject it to cracking and directing resultant cracked products into the rst mentioned separating zone.

GEORGE ARMISTEAD, JR.