US1966640A - Cracking of hydrocarbon oils - Google Patents

Description

`luy 17, 1934. .1. c. MoRRl-:LL

CRACKING OF HYDROCARBON OILS Filed NOV. l5, 1929 Patented July 17, 1934 UNITED STATES 1,966,646 CRACKING or HY'nRocARBoN olLs Jacque C. Morrell, Chicago, lll., assgnor to Universal Oil Products Company, Chicago, Ill., a corporation of South Dakota Application November 15, 1929, Serial No. 407,378

4 Claims.

This invention relates to an improvement in improvement in this art relative to high temperature or vapor-phase cracking in combination with the so-called low temperature or liquid vapor-phase cracking. In its broader aspects, the invention also relates to the production of end point gasoline direct from the cracking system, which gasoline is defined as that having l the boiling range of a finished motor fuel, and the invention also has application in regulating the kind of residual materials produced in the cracking process permitting the production of fuels and asphalts.

The chief feature of the invention, however, is the high temperature cracking of select fractions produced by previous cracking and distillation. The purpose of high temperature of vapor-phase cracking is to convert hydrocarbons, principally of the para'in series, into hydrocarbons of the unsaturated and aromatic series. The napthenehydrocarbons may be intermediate products in these changes. Broadly speaking, the purpose of high temperature cracking is to convert hydrocarbons of low antiknock characteristics into hydrocarbons having desirable antiknock qualities. Of the four principal groups of hydrocarbons, the aromatic series have the highest antiknock properties and this group of hydrocarbons may be formed from the other hydrocarbons by high temperature treatment.

Knocking of motor fuel is the pinking or metallic noise which occurs when part of the unburned motor fuel mixture explodes suddenly. Knocking increases with the compression pressure in the cylinders of the motor and as the efciency of the motor increases; also with the compression pressure knocking is wasteful of fuel and energy. Hence, the eiciency of the motor must be lowered in order to prevent knocking when ordinary fuels are used. The gasoline formed by high temperature or vaporphase cracking permits the operation of high compression motors which insures greater efficiency and saving of motor fuel.

`In`addition to these advantages this kind of motor fuel permits rapid acceleration and climbing of grades or hills without shifting of gears, thus improving the all around eiciency of the motor.

In the low temperature or liquid vapor-phase cracking range the anti-knock properties of the motor fuel depend usually upon the kind and source of charging stock as well as to changes in operating conditions such as temperature and pressure. For example, improvement in the antiknock properties in the motor fuel will be noted when the cracking temperature is increased. The cracking of select cuts at high temperatures, for example between 925 and 1050 F., will improve greatly the antiknock properties of the resulting motor fuel, the improvement increasing with increased temperature.

One of the chief purposes of the present invention is to conduct the so-called low temperature and high temperature cracking operations simultaneously, but in separate elements withdrawing regulated proportions of the clean distillate for high temperature treatment. The invention is directed partially to the withdrawal of clean reux from a secondary fractionating tower to be cracked at high temperatures for the purpose of improving the over-all antiknock properties of the gasoline produced in the cracking system.

The drawing shows a schematic side elevation which embodies the principal features of the invention. The charging stock may be topped crude, fuel oil, heavy residues, gas oil, kerosene, so or any other cut or fraction of petroleum in general. The oil is pumped by means of pump 1 through line 2 into the heating coil 10 located in furnace 11. The oil may be pumped directly into the coil or it may in whole or in part pass through line 3 controlled by valve 3' into iiash dephlegmator 4, through hot oil pump 5 into line 6 and through the principal dephlegmator 7 and reflux leg 8 and hot oil pump 9, and nally back into line 2 and into the heating coil 10. 90 A Valve 6 in line 6 permits of passing charging oil from line 2 directly into column '7 or if desired pump 5 may force reux and preheated oil from tower 4 back into line 2. The purpose of passing the charging oil through flash dephlegmator 4 is to preheat the oil and condensed vapors in the dephlegmator. The purpose of passing the oil through dephlegmator 'l is to further preheat the oil and condensed vapors in the principal dephlegmator. The condensed portion or reiiux of both dephlegmators is combined with the charging oil and passed through the hot oil pump 9 into the heating coil l0. The oil is raised to a suitable cracking temperature in the heating coil 10 and passes 105 through line 12 and valve 13 into reaction chamber 14. Valve 13 may be used to control the pressure upon heating coil 10. The volatile material containing cracked low boiling hydrocarbons passes from reaction chamber 14 through 110 valve 15 and line 16 into dephlegmator 7. Partial condensation of heavy portions of the vapor arising in dephlegmator 7 occurs yowing to the cooling effect of the raw oil. Further condensation may be promoted by pumping some of the finished product through line 17 into the gdephlegmator as later described. 1

Condensed heavier material, known as reflux, passes through reflux leg 8 and through hot oil pump 9 into the heating coil 10. The nonvaporized material from reaction chamber 14 passes through lines 18 and valves 19, which are alternate lines and valves, to the flash chamber 20 where the pressure is reduced to permit volatilization of a substantial portion of the residue from reaction chamber 14. The vapors from flash chamber 20 pass through line 21 and valve 2l into flash dephlegmator 4 where they are substantially condensed by the raw oil charging stock. 'I'he low boiling portion of the vapors from the flash dephlegmator 4 pass through; vapor line 54 and flash condenser 22 into receiver 23, where the condensate may be removed through valvey 23 and uncondensable gas through valve 23". The pressure on flash chamber 20 may be varied from substantially atmospheric pressure upward. The vapors leaving the principal dephlegmator 7 passes through line 24 and valve v25 into the secondary fractionating tower 26. The fractionating tower is preferably of the bubble type which is generally known in the art. During the process of fractionation, reflux liquids are produced and for the bubble type of tower, cuts, or fractions, may be drawn from the decks through lines 27 equipped with valves 28.

It may be found desirable in order to re-boil the lighter portions from the nal reflux to introduce steam into the fractionating tower for which purpose line 29 controlled by valve 30 is provided. The vapors leaving the fractionating column 26 pass through line 3l and valve 32 into condenser 33. The condensed product is passed through line 34 and valve 35 into the receiver 36. The receiver 36 is equipped with line 37 and valve 38 for the release of gas and line 39 and valve 40 for the withdrawal of the liquid. Pump 41 is used for recirculating a portion of the product through line 17 into dephlegmator 7 or tower 26, or both for cooling purposes as may be done by control of valves 4l.

The reflux from the secondary fractionating tower may be in whole or in part withdrawn through line 42 and valves 42 and 43 and pumped by means of pump 44 through a heating coil 45 located in furnace 45. The side stream lines 27 from the fractioning tower 26 may connect with line 42 by means not shown. The oil is susbtantially completely vaporized in coll 45 and is heated to a temperature between 900 and 1100 F, more or less, thus bringing about a substantial conversion into low boiling hydrocarbons of the desired kind. Heavier reflux from primary dephlegmator 7 may similarly be passed through line 8 and valve 43' through the heating coil 45 by means of pump 44. The cracked vapors leave heating coil 45 through line 46 and from there may be passed in one or several directions to utilize the heat contained therein as desired. The vapors may be passed through valve 47 and line 48 into bubble tower 26 for the purpose of reboiling the reflux in the bubble tower to vaporize the low boiling components, as well as be subjected to fractionation, the final vapors passing out of tower 26 with the vapors of the liquid-phase cracking unit. In this case it is desirable to interpose in line 48 a knock-out drum 55 equipped with drain 56, for the removal of tarry materials produced in the vapor-phase unit. Also if desired the vapors may be cooled somewhat by introducing by means not shown a small portion of cooler oil for example charging oil from line 2 into line 46 just before entrance to knock-out drum 55, or the vapors may be passed through line 49 and line 50 through valve 51 and valve 21' into flash dephlegmator 4 where fractionation and condensation of the heavier portions will occur. The lower boiling hydrocarbons are removed through line 54 and are condensed throughflash condenser 22 and collected in receiver 23. Or, the vapors may pass through line 49 and valve 55 into the flash chamber 20 assisting the vaporization in flash chamber 20 and permitting the production of a regulated quality of fuel oil or heavy residual products, such as asphalt. The direction of flow of vapors leaving the heating and cracking coil 45 will depend upon the purpose and all or part of the vapors may be directed in any of the described paths.

The residual product from flash chamber 20 is withdrawn through line 57 and may be passed directly through valves 58 and 59 to a cooling coil or it may be passed through valve 60 and line 61 into the blending equipment 62 where it is blended with a portion of the reflux from bubble tower 26 which may pass with valve 42 closed through line 42 and valve 63.

As a specific example of the temperature and pressures of the operating conditions illustrative of this operation, the transfer temperature--that is, temperature of oil leaving the heating coil 10, may be approximately 875 to 925 F.; reaction chamber temperature, approximately 850 to 875 F.; combined feed temperaturethat is, the temperature of the reflux and charging oil combined, approximately 750 to 775 F.; temperature at top of dephlegmator 7, approximately 550 F.; at the bottom of fractionating tower without reboiling, approximately 500 F., with reboiling, approximately 500-600a F.; at the top of secondary fractionating tower, approximately 350 F. The pressures in heating coil 10, reaction chamber 14, dephlegmator 7, bubble tower 26 and receiver 36 with connecting parts may be substantially the same throughout with the pressure drop from friction and may vary from 100 up to 1000 pounds, more or less. The pressures upon each succeeding element may be dropped,for example, susbtantially from one atmosphere to several atmospheres may be maintained upon that portion of system re-v ferred to from the secondary fractionating column to the primary receiver 36. The pressure upon heating coil 45 may vary from substantially atmospheric pressure upward to any desired pressure. The pressure upon flash chamber 20 and its auxiliary means, the flash dephlegmator, condenser and receiver may be varied from substantially atmospheric pressure up to the pressure of reaction chamber, but preferably should be varied from atmospheric pressure to approximately 30 pounds per square inch.

As an illustration of yields, operating upona non-residuum basis, that is, withdrawing no liquid from reaction chamber 14, using a 24 to 26 A. P. I. gravity topped crude oil, the following yields may be obtained: gasoline, approximately 65 percent, pressure distillate bottoms, approxiresaca@ mately l per cent, coke, about 75 pounds per barrel, gas, approximately 700 cubic feet per barrel of charge. With the same charging stock operating on a fuel oil basis, that is, drawing residual oil into flash chamber, gasoline approximately 50 percent, fuel oil residue, approximately 35 percent, pressure distillate bottoms, approximately percent, gas and coke, approximately 5 percent, making approximately 250- 300 cubic feet ofV gas perbarrel of oil charged and /100ths to l pound of coke per barrel. Where asphalt is made, approximately 20 percent asphalt, approximately 60 percent gasoline, approximately 10 percent pressure-distillate bottoms, and gas and coke, approximately 5 percent, will be produced. A temperature of approximately 800, or slightly higher, may be. required in the flash chamber for asphalt making and this is supplied in part by the heated vaporsfrom cracking coil 45. In making end point gasoline, the pressure distillate bottoms shown may be converted into gasoline increasing the yield of gasoline thereby with a slightly increased formation of coke and gas. The antiknock quality of gasoline formed in coil v may be approximately benzol equivalent.

lt is understood that the temperatures, pressures and yields given are illustrative and may be varied without departing from the spirit of the invention.

Having thus described my invention, what I claim is:-

l. A hydrocarbon oil cracking process which comprises subjecting the oil to cracking conditions of temperature and pressure while flowing in a restricted stream and separating vapors from unvaporized oil, subjecting the vapors to primary and secondary dephlegmation and thereby condensing therefrom a primary reflux and a lighter secondary reflux, returning said primary reflux to the restricted stream, flash distilling said unvaporized oil by lowering the pressure thereon, separately cracking said secondary reflux at vapor phase cracking temperature, and combining resultant cracked vapors with the vapors released by the ash distillation of said unvaporized oil.

2. A hydrocarbon oil cracking process which comprises subjecting the oil to cracking conditions of temperature and pressure while owing in a restricted stream and separating vapors from unvaporized oil, subjecting the vapors to primary and secondary dephlegmation and thereby condensing therefrom a primary reflux and a lighter secondary reux, returning said primary reflux to the restricted stream, flash distilling said unvaporized oil by lowering the pressure thereon, separately cracking said secondary reflux at vapor phase crackingY temperature, and introducing resultant cracked vapors into the unvaporized oil undergoing ash distillation.

3. A hydrocarbon oil cracking process which comprises heating the oil to cracking temperature under pressure while flowing in a restricted stream through a heating zone, discharging the heated oil into an enlarged reaction zone maintained under cracking conditions of temperature and superatmospheric pressure, removing vapors and unvaporized oil from the reaction zone, dephlegmating the vapors thereby forming primary reux and returning such reflux to the heating zone, further fractionating the hydrocarbons uncondensed by the dephlegmation to form condensate of lower boiling point than said primary reflux, flash distilling said unvaporized oil in a flashing zone by lowering the pressure thereon, separately cracking lighter condensate formed by` said fractionation at vapor phase cracking temperature, introducing resultant cracked vapors into said flashing zone and into Contact with the unvaporized oil undergoing flash distillation therein, dephlegmating the resultant mixture /of flashed vapors and cracked vapors and supplying reflux condensate thus formed to said heating zone.

4. In a hydrocarbon oil cracking process, the steps which comprise heating the oil to cracking temperature in a heating zone and separating the same into vapors and unvaporized oil, subjecting the vapors to dephlegmation and thence to fractionation thereby forming primary and secondary reflux condensates, flash distilling the unvaporized oil in a flashing zone by pressure reduction, returning primary reflux condensate to the heating zone for retreatment therein, passing secondary reflux condensate to a second heating zone and heating the same to cracking temperature therein, and introducing vapors from the second heating zone to the flashing zone to assist the distillation of the unvaporlzed oil therein.

JACQUE C. MORRELL.

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