US1775067A - Process for treating petroleum hydrocarbons - Google Patents

Description

R. CROSS Sept.' 2, 1930.

PROCESS FOR TREATING PETROLEUM HYDROCARBONS Filed Aug. 2, 1924 Weil/Jesi;

'5 hydrocarbons to yield relatively li ht distil are, to provide a process in which petroleum hydrocarbons' are continuously treated in a retenue' sept. 2, 1930 4UNrranj s'raiiss, PATENT oFFIcE INC., 0F' WILMINGTON, DELAWARE, A CORPORATION 0F DELAWARE Paocnss non TBEA'IING PETROLEUM IIYnRocARBoNs pplication filed August 2, 1.924.4 SerialNo. 729,693. I

6 is a reaction chamber connected by a trans- This invention relates to improvements in a process and a paratus for treating petroleum hydrocar ons and refers more particularly to a continuous method of cracking late having the characteristics o gasoline andthe like,-`the cracking reaction taking lplace under relatively high pressure and while the oill is maintained substantially in the liquid phase.

Among the salient objects of the invention System under relatively high pressure whereby a synthetic crude is formed in' which are contained considerably more of the low boiling point or lighter 'fractions than in the original charging stock; to provide a process in which Athis synthetic crude Iwhile at high temperature is released from the zone vof high pressure whereby the. lighter fractions are distilled olf; to provide a process in which these lighter fractions are subsequently subjected. to reliuxqcondensation and a process in whichthe liquid material separated outY during the reiluxing or dephlegmating of the vapors is returnedto either the evaporating stage or the initial stage of reux condensation in order to extract the gasoline fractions out of the residue or bottoms separated' inthe na'l stage of dephlegmation; to provide aprocess in which an increased yield of gasoline distillate is procured and one in which there' is'an increased saving of heat primarily due t`o the method of conversion and the recycling of the products for redistillation, and, in general, to provide an apparatus for carrying out the process hereinafter described.

In. the drawings, the single figure is a diagrammatic side elevational view of the apparatuswith parts in section and parts broken away. l

Referring to the drawings, at 1 is shown a furnacehaving an upper and lower compartment,-the-' upper compartment containing l -the preheatin tubes 2 and the lower compartment the ban of heating tubes 3 which'are connected b transfer line 4. The furnace is -eferably eated by means of a gas burner ilgfmleatially Shown at 5. The elementI connected to the evaporator by means of a va-` por line .12 and with the bubble tower 13 by a not cnoss, or KANSAS cI'I'Y, MISSOURI, v.assIeNoa 'ro G'AsoLINE rnoDUc'rs comrm, i

vapor line 14. The top of the bubble tower .communicates through a line 15 to the condenser coil l'positioned in the condenser boX 17. At 18 is shown a gas separator connected with the discharge end of the condenser coil 16 by means of a valve 19 and with the receiver 20 through the pipe 2-1. 22, 23 and 24 are storage tanks for gasoline distillate, recharging stock and fuel oil respectively. At 25 is shown a cooling coil for reducing the temperature of the bottoms Withdrawn from the lower part of the tower 11 through the automatically-operated valve 26 and line 27, The element 28 is a cooling coil through whichis circulated the fuel 'oil bottoms or residual hydrocarbons withdrawn automatically from the lower part of the evaporator 8 through the valve 29 and line 30. At 31, on the side of each of the towers, is diagrammatically shown a li'qid level regulating device for controlling the level in the respective towers by automatic manipulation of the'valves 26, 29 andea I Referring now to the operation, the oil to be treated is charged from the tank 23 toI which itis introduced from any convenient source. This charging stock may consist of hydrocarbons such as those commercially known as kerosene, gas oil or fuel oil, or any type of hydrocarbons utilized in a cracking system for the production of gasoline distillate. This oil iswithdrawn from the tank 23 through the line 33 and is charged, by means of the pump 34, through the line 35, preheating tubes 2 and heating tubes 3, successively.

The oil, after passing through the heating tubes where it is subjected to cracking temperatures, is passed continuously through the line 7 into the reaction chamber Where it is permitted to collect in a considerable body 45 positione steel construction in order to withstand the high pressures to which it is subjected. As 4previously stated, the temperature and pressure conditions are so regulated to'cause Vthe cracking to take place substantially in the liquid phasein the reaction chamber. Th1-1s the hydrocarbons, on being withdrawn from the chamber, are in the -form of a liquid syn- Athetic crude having an increased percentage of low boiling point or lighter fractions relative to the charging stock. rlhis synthetic liquid is passed through the transfer line 9, pressure being reduced at the valve 10 or upon its introduction into the evaporator 8. Under certain conditions it may be advantageous to introduce steam, or a liquid me dium either cooler or at a higher temperature than the oil, through the line 36 controlled by a valve 37; Such conditions are present where an excessive amount of oil is distilled/od with the reduction of pressure, leaving only a dry coke which'is difficult toremo've from the evaporating tower. Under such conditions, the introduction of a cooler hydrocarbon, or cooler medium, serves to reduce the temperature or the oil and increase the liquid residual material formed in the evaporator. The introduction of steam, at this point, assists and promotes vaporization of the synthetic product' and improves the 40' character of the linal distillate.

The vapors distilled odin the evaporating 7tower pass overhead through the line 12 and are introduced into the bottom of the reflux o r dephle ating tower 11 in which may be oa-me elements, such as those shown at 38, or inertpacking material, such as Raschig rings or the like. In this tower Iare separated out the higher boiling .point fractions which are drawn'od las previously explained through the line 27, cooling coil 25 and connecting line 3 9 which conducts them to the recharging Ystock tank 23 where they are recycled with the incoming fresh charging stock back to the cracking system.

The uncondensed fractions, passing out of the top ofthe column 11, areintroduced by means of the line 14 intoy the bottom of the bubble tower 13 where a further separation is eected duel to the contacting of these va- 60 pors with the separate pools of oil maintained at intervals in the column and through which theyl are caused to percolate. The liquid condensed from the .vapors is drained back in an opposed direction to their .65 travel and is collected in the bottom of the it is passed' through the gas separator 18,`

liquid receiving tank 20 and finally into the gasoline storage tank 22. rl`he gas separated from the liquid at 18 is returned through the line40 controlled by alvalve 41 and is utilized as fuel in the burners 5 in the furnace l.

The method of operation, to this point, is substantially the same as the process described in certain prior applications with the possible exception, that an additional dephlegmating tower is interposed between the bubble tower and the evaporating tower. The present invention differs from the prior applications, and principally application Serial No. 7 01,283, filed March 24th, 1924, in the name of Waltr M. Cross, in'that the liquid bottoms separated out in the dephlegmating tower 13 in place of being returned directly to the cracking system through the charging line for treatment in the heating tubes, is recycled when drawn od througlithe valve 32 and pipe 42 to a return pump 43 by means of which this reflux condensate may be directed to the evaporating tower through the pipe 44 controlled by a valve 45 or by nianipuu lation of the valve 45 and the valve 46 diverted into the tower ll through the line 47.

By returning the reflux material knocked back in the bubble tower to the evaporator or to the irst stage of dephlegmation, it is possible to reboil or redistill these relatively lighter fractions without the necessity of re circulation through the heating system. lt is a` Well known fact that the products sepaf rated out in this final stage, or bubble tower 13, are relatively close in their boiling oint characteristics to the gasoline distillate nally recovered and require very little additional heat for redistillation. Thus the recirculation throughthe two preceding stages or througheither stage, furnishes a means for retreating these fractions without the necessity of intermingling them with oils 'of a radically diierent character, such as the first charging stock or recharging stock with- `drawn from the initial tower 11. This method of treatment gives not only increasedv assists to' prevent coking of the-fuel oil or .residual material intheevaporating tower.

A typical operation on Mid-Continent gas oil of from 30 to 32 B. gravity, yielded in excess of forty per cent (40%) distillate,- temperatures from 700 to 850 F. being maintained in the reaction chamber and pres- ,sures in excess of 'atmospheres. The temperatures in the evaporating tower range from 650 to 725 F.; thetemperature in thel initial tower 11 approximately 600 F., While the temperature in the lower part of the bubble tower was inthe neighborhood of 450 F. Thus, it is obvious that the condensate from the bubble tower could be readily retreated in either of the preceding stages.

I claim as my invention:

A process for treating petroleum hydrocarbon oils comprising heating the oil to a cracking temperature in a heating stage without any substantial vaporization thereof and before any substantial decomposition occurs, passing the heated oil to a digestion stage Where the cracking initiated in the heating stage is substantially consummated and wherein the oil is maintained substantially l in liquid phase, reducing the pressure and distilling off the lighter fractions in an evaporating stage, subjecting the vaporized products to a dephlegmating action in separate successive stages and to a final condensing ac'- tion, optionally recycling the reflux con--

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