US2004223A - Process for the conversion or cracking of high boiling hydrocarbon oils into low boiling hydrocarbon oils - Google Patents

Description

June 11, 1935. s u

PROCESS FOR THE CONVERSION OR CRACKING OF HIGH BOILING HYDROCARBON OILS INTO LOW BOILING HYDROCARBON 0111s Original Filed July 24, 1950 INVENTOR JEAN DELATTRE SEGUY BYF ZM ATTORNEY Patented June 11, 1935 PATENT OFFICE PROCESS FOR THE CONVERSION OB CRACKING OF HIGH BOILING HYDRO- CARBON OILS INTO LOW BOILING HYDROGARBON OIL Jean Delattre Seguy, Chicago, 111.,

Universal Oil Products Company, a corporation of South Dakota assignor to Chicago, 111.,

Application July 24, 1930, Serial No. 470,342

- Renewed February 8, 1934 5 Claims.

This invention contemplates the provision of a process for the conversion or cracking of high boiling hydrocarbon oils into low boiling hydrocarbon oils. 7

The invention relates to a process wherein hydrocarbon oils are subjected to a primary cracking reaction under proper conditions, the vapors and the residue resulting from the cracking being separately treated. The specific form of process to which the invention relates comprises the introduction of heavy hydrocarbon oil into a heating coil in which the oil is subjected to pressure and temperature conditions sufliciently elevated to induce cracking, the oil then being subjected to reaction in a primary reaction zone, the vapors evolved therefrom being withdrawn and subjected to dephlegmation with the separation 'of the lower boiling hydrocarbons in the form of vapors from the higher boiling hydrocarbons which are obtained as a reflux conden sate. The unvaporized residue from the primary reaction zone is distilled by its contained heat in a flashing zone, the vapors being withdrawn for treatment in'a fractionating zone, the lighter 25 fractions therefrom being condensed, the heavier fractions taking the form of a reflux condensate.

One of the features of my invention resides in the vapor phase cracking of the reflux obtained 80 by dephlegmation of the vapors withdrawn from the primary reaction zone and the return of the products resulting from the vapor phase cracking into the primary reaction zone to assist in the conversion of the oil and to regulate the character of the productobtained in said zone. By

means of the coupling up of this feature of the invention with the primary cracking system, a gasoline containing high anti-knock properties may be obtained.

A further feature of my invention resides in the vapor phase cracking of the flash reflux condensate and the introduction of the products resulting therefrom into the primary reaction zone. In accordance with the provisions of the invention, it is contemplated that the vapor phase cracking of the reflux from the primary dephlegmator and the reflux obtained from the flash distillation step may be carried on simultaneously in the same vapor phase cracking zone, the relative proportions of the reflux condensates subjected to vapor phase cracking being regulated to any desired extent, the products of the vapor phase cracking being then introduced into the primary reaction zone. The reflux condensate from the flash distillation step may, if desired, be passed into direct contact with; the vapors being treated in the primary dephlegmating zone, or they may be passed directly to the vapor phase cracking zone.

My invention provides further for the indirect contact of the charging oil with the vapors arising in the various fractionating zones. The charging oil may be passed in indirect contact, therefore, with the vapors which are being treated in the flash distillation zone, and may also be passed through a similar indirect heat exchange relationship with the vapors in the primary dephlegmating zone. This insures the proper cooling of the vapors in said zones with the obtaining of reflux condensates which may suitably be subjected to vapor phase cracking conditions. A minor portion of the charging oil may, if desired, be passed in direct contact with the vapors in the flash distillation zone dependent upon the operating conditions of the process.

As a provision of my process, I may divert a portion of the charging oil into direct contact with the oil emerging from the primary heating zone or from the vapor phase cracking zone for the purpose of checking cracking to any desired extent. The cooling of the oil coming from the heating zone in this manner and its contact in the reaction zone with the oil from the vapor phase cracking zone serves to check or control the cracking of the products which are introduced into the primary reaction zone from the vapor phase cracking zone.

Other improvements and features of my invention will be more fully understood by reference to the drawing showing an apparatus suitable for carrying out the process of the invention, the drawing being diagrammatic and not to scale.

The raw oil charging stock is pumped through line I by means of pump 2 into line 3, controlled by valve 4. A portion of the charging stock may be introduced directly into the flash dephlegmator 1 through line 5, controlled by valve 6. It is desirable, however, that all or the major portion be fed through line 8, controlled by valve 9, into in-v direct heat exchanger I 0 located in flash dephlegmator 1. The raw charging oil is then fed into indirect heat exchanger l I located in primary Y dephlegmator l2, causing partial condensation of the vapors arising therein, the reflux condensate so formed being further subjected to cracking conditions as will be hereinafter described. The raw oil then passes through line 53 and valve 10 into heating element l4 located-in furnace setting 125. A portion of the raw oil may be diverted through line l6, controlled by valve l1, into the transfer line I8 of the heating element I4. The raw oil passes through control valve I9 into reaction chamber 28. The vapors leaving reaction chamber 28 pass through line 2|, controlled by valve 22, into the dephlegmator I2 wherein indirect heat exchange occurs between the ascending vapors and the raw oil as heretofore described. Additional cooling is also eifected, as will be hereinafter described.

The reflux condensate from the dephlegmator passes through line 23, controlled by valve 24, into hot oil pump by which it is pumped by line 26, controlled by valve 21, into secondary heating element 28 located in furnace setting 29. The temperature in this heating element is elevated so that substantially vapor phase cracking occurs therein. The vapors leaving heating element 28 pass through line 69, controlled by valve 30, into reaction chamber 20.

The final vapors leaving dephlegmator I2 pass through line 3 I, controlled by valve 32, into cooler and condenser 33, the distillate therefrom together with gases passing through line 34,. controlled by valve into receiver 36. The distillate from receiver 36 is withdrawn through line 31, controlled by valve 38. The gases in receiver 36 are withdrawn by line 39, controlled by valve 46. A portion of the distillate may be recirculated to the dephlegmator I2 through line 4|, controlled by valve 42, by means of pump 43 and through line 44, controlled by valve 45. The purpose of this is to assist in cooling the vapors arising in dephlegmator I2 to condense out the heavier portions therein, the reflux condensate so formed being subjected to conversion conditions as previously described.

The unvaporized residue from reaction chamber 20 passes through line 46, controlled by valve 41, into the flash distilling-chamber 48 where owing to the reduction in pressure and the latent or stored heat in the residuum flashing or vaporization occurs. Unvaporized residual oil may be withdrawn from chamber 48 through line II and valve I2. The vapors leaving the flash chamber 48 pass through line 49, controlled by valve 50, into flash dephlegmator I. The heavier portions of the vapors are condensed in flash dephlegmator I owing to the cooling action of the raw oil either by indirect or direct contact. Additional cooling of the vapors in dephlegmator I may be provided, by means of relatively light oils, such as a part of the distillate collected in receiver 64, or material not heavier than the condensate formed in dephlegmator 1. The reflux condensate so formed passing through line 5|, controlled by valve 52, is pumped by means of pump .53 through line 54 in whole or in part through line 55, controlled by valve 56, into the primary dephlegmator I2 or through line 51, controlled by valve 58, and by means of pump 25 through line 26, valve 21 into vapor phase heating element 28 from where it is discharged through line 69 and valve 30 into the reaction chamber 20. A portion of the raw oil, before it enters heating coil I4 may be diverted through line I3, controlled by valve 14, and mixed :in line 69 with the products of vapor phase cracking,

whereby their temperature and the degree of conversion may be regulated.

The lower boiling components of the vapors leaving flash dephlegmator I pass through line 59, controlled by valve 60, into flash cooler and ing in flash receiver 64 may be withdrawn through line 65, controlled by valve 66. The gases collecting in receiver 64 are withdrawn through line 6'1, controlled by valve 68.

While the products from coil 28 may discharge at upper part of chamber 20, near the point of introduction of the products from coil I4, it may be preferable to introduce them at the lower part of chamber 28, whereby the vapors may bubble through the unvaporized oil maintained at the lower part of said chamber. However, the condition of level or time element in the chamber 26, as well as the temperature therein are preferably controlled by the various means shown so that little or no carbon forms, and that the residue from the process may be substantially free of B. S. and solids, or may not contain more than 2% thereof.

I may employ equalized pressure on the heating element i4, reaction chamber 20, primary dephlegmator I2, condenser 33 and receiver 36, or I may employ differential pressures thereon. Preferably, there is a reduction in pressure between the reaction chamber 26 and the flashing still 48. The pressure in heating element 28 may be elevated as desired by means of pump 25.

I preferably employ temperatures within the cracking range of 800 F. to 975 F., more or less, in heating element I4, whereas in heating element 28 I preferably employ temperatures ranging from 950 F. to 1250 F., more or less, although I do not limit myself specifically to these ranges.

As a specific example of the results obtained by the process of my invention, a 28 A. P. I. gravity topped crude may be processed at a temperature in the heating element I4 of approximately 900 F., under a pressure, maintained on the heating element and the reaction chamber 20, of approximately 175 pounds per square inch, the pressure. on the elements I2, 33 and 36 being substantially equalized therewith; the temperature in vapor phase heating element 28 may be approximately 975 F.; the ratio of reflux condensate, including the condensed flash distillate passing through coil 28 being approximately three times the amount of raw oil charged to-coil I4; the average temperature in the reaction chamber being approximately 875 F., a yield of about 60% of gasoline was obtained having an anti-knock value of approximately benzol equivalent, that is equivalent to a mixture of straight run Pennsylvania gasoline and benzol containing 50% of the latter. Approximately 25% of a good fuel oil residue was obtained having less than 2% B. S. and suspended carbonaceous matter; approximately 5% of pressure distillate bottoms was obtained and the remainder was substantially all gas, as very little coke was made.

By elevating the temperature in the heating element 28 to 1025 F. and maintaining all other conditions substantially constant with the exception of the temperature in reaction chamber 28, which was somewhat increased, and with the exception of a somewhat lower reflux ration resulting from the operation, the gas volume was increased from approximately 650 cubic feet per barrel in the previous example to approximately 850 cubic feet per barrel of raw oil charged in the present case. The gasoline yield was reduced to approximately 55% and the anti-knock value was increased to approximately benzol equivalent. A heavy asphaltic residual oil was produced and the amount of pressure distillate bottoms was increased somewhat. The amount of coke formed in the second case was greater than that in the first. With similar conditions, but by cooling the oil discharging from coil 28 with cooler oil, as shown, so as to lower the temperature of the oil in the chamber 20 down to about 875 F., the yield and the anti-knock characteristics remained about the same, but the residue was rendered more fluid and its content in B. S. and solids, as well as the coke formation were substantially reduced.

The rate of gas formation was found to be not solely a function of temperature, but also of time and pressure. The pressure in the heating element 28 during the above operations was approximately 200 pounds per square inch. In other cases where the pressure was reduced on the reaction chamber 20 and the succeeding elements and the pressure likewise on coil 28 for corresponding temperatures the gas formation was found to increase somewhat. The pressure on the flash distillation system was maintained at approximately 30 pounds per square inch.

In the above operations only a small portion of the raw oil was by-passed in direct contact with the vapors in the flash dephlegmator.

The above examples are illustrative only and are not to be considered as limitations on the scope of the invention.

I claim as my invention:

1. A hydrocarbon oil cracking process which comprises passing the oil in a restricted stream through a primary heating zone and heating the same therein to cracking temperature under sufflcient pressure to maintain a substantial portion thereof in the liquid phase, discharging the heated oil into a vapor separating zone and separating the same therein into vapors and unvaporized oil, separately removing the vapors and unvaporized oil and flash distilling the latter by lowering the pressure thereon, dephlegmating the flashed vapors and the vapors removed from said separating zone and combining the resultant reflux condensates, passing the thus combined reflux condensates to a secondary heating zone and cracking the same therein in the vapor phase at higher temperature than that to which the oil is heated in said primary heating zone, and introducing the vapor phase cracked vapors from said secondary heating zone into said separating zone.

2. A hydrccarbon oil cracking process which comprises passing the oil in a restricted stream through a primary heating zone and heating the same therein to cracking temperature under sufficient pressure to maintain a substantial portion thereof in the liquid phase, discharging the heated oil into a vapor separating zone and separating the same therein into vapors and unvaporized oil, separately removing the vapors and unva-- porized oil and flash distilling the latter by lowering the pressure thereon, dephlegmating the flashed vapors to condense heavier fractions thereof, passing resultant reflux condensate in direct heat exchange relation with the vapors removed from said separating zone to dephlegmate the latter and combine insufllciently cracked fractions thereof with said reflux condensate, passing the thus combined reflux condensates to a secondary heating zone and cracking the same therein in the vapor phase at higher temperature than that to which the oil is heated in said primary heating zone, and introducing the vapor phase cracked vapors from said secondary heating zone into said separating zone.

3. A hydrocarbon oil cracking process which comprises passing the oil in a restricted stream through a primary heating zone and heating the same therein to cracking temperature under sufflcient pressure to maintain a substantial portion thereof in the liquid phase, discharging the heated oil into a vapor separating zone and separating the same therein into vapors and unvaporized oil, separately removing the vapors and unvaporized oil and flash distilling the latter by lowering the pressure thereon, dephlegmating the flashed vapors and the vapors removed from said separating zone and combining the resultant reflux condensates, passing the thus combined reflux condensates to a secondary heating zone and cracking the same therein in the vapor phase at higher temperature than that to which the oil isheated in said primary'heating zone, contacting the vapor phase cracked vapors with a cooling oil to substantially lower the temperature thereof and introducing the same to said separating zone.

4. A hydrocarbonoil cracking process which comprises passing the oil in a restricted stream through a primary heating zone and heating the same thereinto cracking temperature under sufiicient pressure to maintain a substantial portion thereof in the liquid phase, discharging the heated oil into a vapor separating zone and separating the same therein into vapors and unvaporized oil, separately removing the vapors and unvaporized oil and flash distilling the latter by lowering the pressure thereon, dephlegmating the flashed vapors to condense heavier fractions thereof, passing resultant reflux condensate in direct heat exchange relation with the vapors removed from said separating zone to dephlegmate the latter and combine insufliciently cracked fractions thereof with said reflux condensate, passing the thus combined reflux condensates to a secondary heating zone and cracking the same therein in the vapor phase at higher temperature than that to which the oil is heated in said primary heating zone, contacting the vapor phase cracked vapors with a cooling oil to substantially lower the temperature thereof and introducing the same to said separating zone.

5. A hydrocarbon oil cracking process which comprises heating the oil to cracking temperature under pressure in a primary heating zone, separating the heated oil into vapors and unvaporized oil under presssure, dephlegmating the separated vapors to condense insufliciently cracked fractions thereof as reflux condensate, condensing the dephlegmated vapors as a product of the process, flash'distilling the unvaporized oil by lowing the pressure thereon, dephlegmating the resultant flashed vapors to condense heavier fractions thereof, combining such condensed heavier fractions with at least a portion of said insufliciently cracked fractions condensed in said dephlegmating step and subjecting the mixture to vapor phase cracking in a second heating zone, and combining the resultant vapor phase cracked products with products of the first-mentioned zone.

JEAN DELA'I'I'RE SEGUY.

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