US2061820A - Process for cracking oil - Google Patents

Description

NOV- 24, 1936- J. G. ALTHER PROCESSv FOR CRACKING OIL Original Filed Nov. 4, 1929 2 Sheets-Sheet l uw mw Nov. 24, 1936. J, G. ALTHER 2,061,820

PROCESS FOR CRACKING OIL Original Filed NOV. 4, 1929 2 Sheets-Sheet 2 Patented Nov. 24,l 1936v UNITED STATES PATENT oFFlc-E Application November 4, 1929, Serial No. 404,625 Renewed July 12, 1934 5 Claims. (Cl. 196-49) This invention relatesto the art of treating hydrocarbon oils and more particularly to the separation of various constituents of the oil and their treatment for the productionof more desirable products.

Among the methods now in general 'commercial use for the manufacture of motor fuel are what are known as the topping process, the liquidvapor phase cracking process and the vapor phase cracking process. The topping process, as the name would imply, simply separates the natural light fractions contained in the crude oil from the heavier portions. This is a simple and comparatively inexpensive process, but the produc tion of motor fuel therefrom is,'of course, limited to the natural gasoline contained in the crude oil.

By what is known as the liquid-vapor phase cracking process, the residual oils and intermediate distillates from distillation operations as' well as crudes in their natural state, may be subjected to super atmospheric pressure and temperatures beyond those required to vaporize the oil at atmospheric pressure and may be so converted into products of higher and lower molecular weight and boiling points. The term, liquidvapor phase, indicates that the oil undergoing treatment remains in part in the liquid state, and a portion of the oil may be vaporized in the heating element and the amount vaporized is a function of the temperature attained and the pressure to which the oil is subjected. With various improvements in this process such as the ashing operation, the production of those products suitable for motor fuel may be maintained at maximum for a given production of marketable fuel oil and the production of the heavier residual pitchy materials and carbon minimized.

In the vapor-phase process, the oil is subjected to treatment under conditions somewhat similar to those employed by the liquid-vapor-phase method, but temperatures employed are generally higher and the pressures generally lower than those employed for similar oils undergoing liquid vapor-phase cracking. Consequently, all or a major portion of the oil undergoing treatment is in a vaporized state.

While the so-called liquid-vapor-phase process is the least limited of the three, as it may be employed to convert nearly any type of hydrocarbon oil with a high yield of motor fuel, it is particularly adapted to the handling of heavy oils such as topped crudes and fuel oils, whereas the vaporphase process in its present state is usually limited to the conversion of lighter oils such as gas oil, intermediate distillates and the like. `One of the main advantages of the vapor-phase process, however, lies in the fact that the high temperatures employed are conducive to the formation of motor fuels having a high antiknock value.

My invention employs modifications of all three 5 of the above mentioned processes and by their combination assures the most suitable treatment for various components of the oil and-a consequent maximum yield of the most desirable products.

The novel method whereby these three systems are tied together and-operated as an inter-dependent unit comprises one of the features of this invention. By my process reflux from the fractionating device of the topping system may be l5 returned to the liquid-vapor-phase system for treatment.v Reflux from the fractionating device of the liquid-vapor-phase system may be returnedf wholly or in part to the vapor-phase system for further treatment or a portion may be returned to the llquid-vapor-phase heating element for reconversion. A- portion or all of the residual oil from the liquid-'vapor-phase system may be `treated in a zone substantially reduced pressure (a flash chamber) where the lighter portions are vaporized. This flash chamber may be the same zone into which oil from the heating element of the topping system is discharged. A portion or all of the residual oil from the vapor-phase system may likewise be returned to this same ash chamber, or to the liquid-vapor-phase reaction chamber, either or both.

Another feature of this invention is the introduction of a cooling medium into the material leaving the vapor-phase heating element. This cooling medium may be charging stock, any nished product or intermediate product from within 'the system, or any suitable oil or other cooling medium such as gas or steam from an exterior source. It is to be understood that this cooling medium may be introduced at any desired temperature.

The novelty and advantages of such a system are manifold and for the sake of clearness some of the main objects will be enumerated. By passing the raw oil into a liashing zone after it is heated in the heating coil of the topping system and then fractionating the vaporized portion separating the reux and returning it to the liquidvapor-phase system, those productsy best suited to liquid-vapor-phase treatment may be subjected thereto, the heavier portions of the charging stock which may be conducive to the formation of coke having been dropped out in the flash chamber. Likewise, the clean reux liquid from 55 the fractionating zone of the liquid-vapor-phase system, which is suitable for vapor-phase treatment, may reach the vapor-phase system. By the combined flashing of all or a portion of residual oils in any desired proportion from the liquidvapor-phase and from the vapor-phase systems, together with the heated raw oil from the topping furnace, a temperature may be maintained in the ash chamber most conducive to the proper separation of the light ends in the residual oils and yet leave a residual product suitable for fuel.

The introduction of a cooling medium beyond the heating element of the vapor-phase system where high temperatures, usually above 950 F., are prevalent permits heating in the so termed vapor phase to the necessary high temperature and for the required time to insure the high production of those hydrocarbons which retard detonation and at the same time permits cooling or quenching of the heated material before a timetemperature relation is attained which is conducive to the excessive formation of fixed gas and carbon or both.

There is shown in the accompanying drawings apparatus suitable forcarrying out my process in whichl Fig. 1a is a partial view in side elevation of the apparatus and Fig. 1b discloses the remaining parts of the apparatus.

Referring to Figure 1 the charging stock from any suitable source enters through valve I, in line 2 and may be pumped through pump 3, valve 4 and line 5 into pre-heating coil 6 which is located in the top of the fractionating tower I4 of the flashing system. The raw oil may be here pre-heated by the vapors in the top of fractionating tower I4 and then may pass through line 1 and valve 8 into the heating element 9, of the topping system, located in any suitable furnace IU. The heated oil passes from heating element 9 through line II and valve I2 into the vaporizing zone or ash chamber I3 which, on this particu-` lar drawing is shown as the lower section of fractionating tower I4. If it is desired to carry super atmospheric pressure in the heating element 9, this pressure may be released or reduced 'ber of streams may be taken from the fractionating tower I4. If the charging stock used is crude oil containing a percentage of natural gasoline the gasoline vapors may pass through valve I 6 and vapor line I1 into the condensing and cooling coil I8 from which they may be withdrawn through valve I9, line 20 and lookbox 2I, the liquid product being Withdrawn through line 22 and any uncondensed gases being taken olf through line 23. Other fractions may be similarly con-- densed .and collected, forinstance, a kerosene fraction may be withdrawn through valve I6', vapor line I1', cooler I8', valve I9', line 20', lookbox 2|', liquid draw-off 22 and gas release vline 23. If desired a receiver and gas separator or other suitable equipment may be used in place of the lookboxes, especially if it is desired to operate the flashing system under pressure. Products from any portion of the system may be returned to the top of fractionating tower I4 for the purpose of cooling the vapors by either direct or indirect contact and to assist fractionation, the required connections are not shown.

The reflux liquid collecting on the partition I5 may pass through line 24, valve 25, pump 26 and line 21 into line 28. From line 28 reuxed liquid from fractionating tower I4 may enter the heating element 29 of the liquid-vapor-phase system. This heating element 29 is placed in any Vsuitable furnace 30. The heated oil passes through line 3| in valve 32 into the reaction chamber 33. Vapors from the top of the reaction chamber 33 pass through line 34 and valve 35 into the dephlegmator 36, which may be any suitable fractionating device containing perforated pans, bubble trays, packing or any other suitable fractionating means. or any combination thereof. The type of product recovered from the vapors entering dephlegmator 36 and leaving the top of the dephlegmator, will depend upon the-degree of fractionating done therein and may be a nished motor fuel or a product requiring redistillation, as desired. Vapors from the top of dephlegmator 36, pass through vapor line 31, valve 38, condenser 39 and into receiver 42 through valve 40 in line 4I. Liquid may be withdrawn from receiver 42 through line 43 and valve 44. Any portion of the liquid product from receiver 42 may pass through valve 45 in line 46 and by means of pump 41 be sprayed into the dephlegmator 36.

Uncondensed gas from receiver 42 may be withdrawn through line 43 controlled by valve 44'. Reiiux from the bottom'of dephlegmator 36 may pass through line 48 and by means of surge pump 49 flow through line 50 into line 28. From line 28 a portion or all of this reflux liquid from dephlegmator 36 depending upon the control of Avalves 28', may pass into the vapor-phase heat- 'ing element 5I which is located in any suitable furnace 52. It will be understood that oil entering line 28 from the liquid-vapor-phase dephlegmator 36 may pass wholly, in part or in any desired proportion to either the liquid-vaporphase heating element 29, or the vapor-phase heating element 5I, depending on the oil undergoing treatment and the desired results.

Discharge from the vapor-phase heating element 5I may pass through line 53 and'valve 54 into the vapor-phase reaction chamber 55. Any desired cooling medium may be introduced at the required temperature through line 56 controlled by valve 51. Vapors from the vapor-phase reaction chamber 55 may pass through line 58 and valve 59 into the vapor-phase fractionating tower 60.. As in dephlegmator 36 the type of vapors leaving the top of the fractionating tower 60 may be controlled by the degree of fractionating therein and the desired product may pass through line 6I,-valve 62, condenser 63, line 64 and valve 65 into receiver 66 and be Withdrawn through line 61 and valve 68. Any portion of this product may likewise be returned through valve 69 in line 10 by means of pump 1I to the fractionating tower 60, or if desiredfand it is sometimes preferable, distillate fromvreceiver 42 or from lookbox 2| may be introduced to tower 60 through suitable means (not shown). Uncondensed gas may be Ywithdrawn from receiver 66 through line 12 controlled by valve 13. v

Reflux from the bottom of the vapor-phase fractionating tower 60 may pass through line I4 and by means of surge pump 15 be returned through line 16 to the vapor-phase heating element 5I.

Residual oil from the vapor-phase reaction chamber 55 may be withdrawn through lines TI controlled by valve 'I8 and returned through line I9,'va1ve 80, pump 8I, valve 82 and valve 83 into the vaporizing zone or flash chamber I3,Othrough line 84, valve 85, line II and valve I2. A portion or all of this residual oil from the vapor-phase system may be diverted, however, and pass into the liquid-vapor-phase reaction chamber through line I9 and valve 83', as an intermediate step. It will be appreciated that when a cooling medium is introduced into transfer line 53 considerable residue will accumulate in chamber 55. Residual oil from the liquid-vapor-phase reaction chamber 33 may likewise be returned through alternate lines 86 controlled by` Valves 8l through line 88, valve 89, pump 90' and valv'e 9| into line 84 and thence to vaporizing zone or flash chamber I3 through valve 85, line' II and valve I2.

VBy means of reduced pressure on flash cham-` ber I3 the latent heat in the residual oils may be utilized to vaporize their light portions and portions of the charging oil and these may pass,

into the fractionating tower I4. 'I'he liquid remaining in flash chamber I3, may be continuously withdrawn through lines 92 controlled by valves 93.

The following is given as an example of the operation of my process, but it should not be interpreted as limiting the process to the method of operation or the particular results therein disclosed.

A 33 A. P. I. Oklahoma crude oil was charged to the heating element of the topping system having rst been preheated in coil I5 to a temperature of approximately 400 F. The topping system was operated under substantially atmospheric pressure and the natural gasoline contained in the charging stock which amounted t0 approximately 20% of 437 F. end point gasoline, was recovered from the top of the fractlonating tower. A kerosene cut amounting to approximately 15% of the charge was taken through a side stream from the fractionating tower. A 23 A. P. I. intermediate distillate returned as ref iux from the fractionating tower of the topping system was cracked in the liquid-vapor-phase element and yieldedv approximately 55% of gasoline based on the oil charged to the liquid-vaporphase element or approximately an additional 25% based on the crude oil. The transfer temperature'in the liquid-vapor-phase treatment was 910 F. and the pressure approximately 300 pounds per square inch. In this particular operation a portion ofthe reflux from the dephlegmator of the liquid-vapor-phase system was returned for re-treatment to the heating element of the liquid-vapor-phase system. The balance of this reflux was processed in the vapor-phase element at a temperature vof approximately 1050 F. and at above atmospheric pressure, and yielded approximately an additional 20% of high anti-knock gasoline having a benzol equivalent of about Residual oils Withdrawn from the reaction chambers of the liquid-vapor-phase and vapor-phase elements were not measured, but were returned to the ash chamber or Vaporizing zone of the topping system and together with the bottoms from the crude oil amounted to approximately 15% of the crude oil charged to the system. This nal residual oil was sultable for use as refinery fuel.

Having thus described my inventionwhat I claim isz- 1. A process for treating high boiling point hydrocarbons to produce products of gasolinelike character comprising maintainingl a low pressure zone, introducing to said low pressure zone preheated charging oil and hot residue from a liquid-vapor-phase cracking process, partially distilling the charging oil and residue in said zone, removing from said zone the unvaporized charging oil and residue and isolating the same from the process, fractionating vapors evolved in said low pressure Zone, recovering the light fractions from said fractionation, subjecting the heavy fractions from said fractionation vto a liquid-vapor-phase cracking treatment,

separately taking 01T vapors and hot residue from said liquid-vapor-phase cracking treatment, thus obtaining the hot residue to be introduced to said `low pressure zone, subjecting the vapors from said 'liquid-vapor-phase treatment to fractionation to obtain an intermediate product amenable to vapor phase cracking and subjecting the intermediate product thus obtained to vapor-phase cracking, and introducing residual products of the vapor-phase cracking to said low pressure zone.a

l2. A process' for treating high boiling point hydrocarbons to produce products of gasolinelike ,character comprising maintaining a low pressure zone, introducing to said low pressure zone charging oil for the process, hot residual products from Oliquid-vapor-phase cracking and hot residual products from vapor-phase cracking, partially distilling the charging oil in said zone and isolating the unvaporized portion thereof from the process,subjecting vapors evolved in said low pressure zone to fractionation to obtain a fraction amenable to liquid-vapor-phase cracking, subjecting the fraction thus obtained to liquid-vapor-phase cracking, subjecting vapors produced in the liquid-vapor-phase treatment to fractionation to obtain a fraction amenable to vapor phase cracking, subjecting the last mentioned fraction to vapor phase cracking and returning the residual products from both said liquor-vapor-phase cracking treatment and said vapor-phase cracking treatment to said low pressure zone.

3. A process for cracking oil comprising imparting heat lfrom residual products of a liquidl able as charging oil for the liquid-vapor-phase cracking treatment, subjecting the fraction thus obtained to liquid-vapor-phase cracking, subjecting products vaporized in the liquid-Vaporphase treatmentto vapor phase cracking and utilizing the residual products of said liquid- Vapor-phase cracking treatment and the residual products of said vapor-phase treatment to impart heat to the charging oil.

4. A hydrocarbon oil cracking process which comprises passing a hydrocarbon distillate through a heating zone and heating the same therein to cracking temperature .while maintained under sufficient super-atmospheric pressure to retain a substantial portion thereof in liquid condition, discharging the thus heated distillate into a vapor separating zone and separating the same therein under super-atmospheric pressure into vapors and unvaporized oil, separately removing the vapors and unvaporized oil from said separating zone, introducing the unvaporized oil to a flashing zone maintained under lower pressure than said separating zone, introducing to said flashing zone preheated crude oil containing gasoline, partially distilling the crude oil in said flashing zo-ne to vaporize the gasoline and fractions thereof heavier than gasoline and to forml a crude oil residue, isolating said residue from the process, fractionating the vapors evolved in said ashing zone to condense therefrom fractions heavier than gasoline, and supplying such condensed fractions to said heating zone to constitute said distillate, dephlegmating the vapors removed from the separating zone and vcracking resultant reflux condensate substantially into vapor phase, and introducing residual products of the last named cracking into heat exchange relation with the crude oil.

5. A hydrocarbon oil cracking process which comprises passing a hydrocarbon distillate through a heating zone and heating the same therein to cracking temperature while maintained under sufficient super-atmospheric pressure to retain a substantial portion thereof in liquid condition, discharging the thus heated distillate into a vapor separating zone and separating the same therein under super-atmospheric pressure into vapors and unvaporized oil, separately removing the vapors and unvaporized oil from said separating zone, introducing the unvaporized oil to a flashing zone maintained under lower pressure than said separating zone and flash dstilling the same therein by pressure reduction, simultaneously introducing charging oil for the process to said flashing zone and therein vaporizing a substantial portion thereof, isolating from the process residual portions of said unvaporized oil and of the charging oil deposited in the flashing zone, fractionating the vaporous mixture formed in the flashing zone to condense heavier fractions thereof and supplying such ycondensed fractions to the heating zone as said JOSEPH G. ALTI-IER.

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