US1774228A - Process for cracking hydrocarbon oil - Google Patents

Description

Aug. 26, 1930.

A. D. DAVID PROCESSA FOR CRACKING HYDROCARBON OIL Original Filed May 31, 1923 @atente Ang. 26, E93

lBt-.Y D. DAVID, OF CHICAGO, LLNOIS, ASSGNOR TO UNVERSL @EL PRQDUCTS COME'ANY, OF CHICAGO, ILLENIS, A CORPORATION 0F SOUTH ifltl` RGCESS FOR-CRACKING HYDRCARBON OIL Application led May 31, 1923, Serial This invention'relates to improvements in a process for cracking hydrocarbon oils, and refers more particularly to the pressure distillation carried on continuously to effect the conversion of relatively high boiling point oils into oils of a loW Vboiling point having the characteristics of gasoline and the like.

Among the objects of the invention are to provide a process in which a charging stock is introduced and utilized as a refluxing medium, having first been preheated by circulation of the residual substances from the still and the reflux condensate about coils through Which the cool incoming oil is directed; to provide a process in which the oil is distributed over a fiat surface in a relatively thin stream whereby a maximum surface of the oil is exposed to the heat and pressure conditions of the still, promoting the conversion reaction; to provide an apparatus for carrying out this process, and in general to provide a process and apparatus of the character referred to.

rihe single figure is a diagrammatic side' elevational view of the apparatus With parts in section.v

Referring to the drawings, 1 is a pump, 2 a reflux prehenter comprising a closed container having a'coil 3 positioned therein. At 4 is shown a similar type of preheater with the closed outer container, and a similarl coil 5 positioned therein. rThis latter preheater receives its heat from the residuum, as will hereinafter be explained. At 6 is shown a still, above Which is positioned a dephlegmating tower 7. The still is connected by transfer pipe 8 to the heating coil 9 positioned in the furnace 10, shown as a side fired type of furnace with a combustion chamber 11 in which burners 12 are situsted, and a heating chamber 13 in which the heating coil is positioned. The dephlegmater is connected at its top by means of a pipe le With a partial condenser comprising a coil 15 in a condenser box 16, which is preferably cooled either by water or cool oit which is circulated about the coil.

rlhis partial condenser has connection through the pipe 17 with the hnal condenser coil it? positioned in the condenser box 19.

No. 642,435. Renewed May 25, 1.929.

rlhe discharge end of the final condenser coil 18 is connected by means of a line 20 to a receiving tank 21, which is equipped With a pressure gauge 22, liquid level gauge 23, pressure relief valve 2a and drawof valve 25. Describing now the mannerin which vthe oil is circulated through the system and treated under regulated conditions of tem* perature and pressure to relieve therefrom the lighter fractions and produce a distillate of relatively lighter gravity, the charging stock is introduced from any convenient source through the inlet pipe 26 and is charged by means of the pump 1 through the line 27, ivhich has secondary connections 28 and 29, With the reflux. preheating coil 3. llt is likewise connected by pipes 8O and 31 to the residuum pr'eheating coil 5. Valves 32 and 33 are positioned in the line 27, and valves 34 in the respective lines communicating with the preheating coils for controlling the travel of the oil introduced to the system. ln this manner, it is possible to circulate the incoming oil charge in heat exchange relation With the hot mixture of raw oil and reflux condensate returned from the dephlegmating column 7 and subsequent thereto, directing it in heat exchange relation contact with the hot residual substances Withdrawn from the still.

liy by-passing the preheaters, the oil may 4be charged directly through the line 27, thence through the pipe 35 controlled by a valve 36 and introduced directly by the spray 37 into the dephlegmating column.

The reflux tower or deplilegmating column has positioned therein a plurality of baille members 38 for breaking up the flow of liquid into finely divided particles and exposing an increased surface of the liquid medium to the hot oil vapors rising through the column. This charging stock serving as a reuxing medium, separates out considerable quantities of the higher boiling point fractions which collect with the introduced liquid into the pan 39 positioned at the bottom of the column. A drawoff line 40 from this pan or receptacle, controlled by a valve 41, serves to return this hot liquid mixture to a charging pump 42 from which it is disthrough -the transfer line 8 controlled by a valve 45, and is introduced above the plate 46 positioned in the upper part of the still 6. The oil on being introduced onto this plate, spreads out into a relatively7 thin ilm, and gravitates toward the opposite end olf. this still, due to the inclination of the plate. During its travel aloneP the surface of the plate, a considerable portion of the oil is vaporized, due to the heat in the chamber, the unvaporized portion flowing off the end of the plate and collecting in a pool in the lower part of the chamber.

This unvaporized portion may be drawn i off either intermittently or continuously in order to maintain a controlled level in the still. This drawn off unvaporized liquid is directed'through a pipe 47 controlled by a Valve 48 t0 the residuum preheater Where a portion of its heatis taken up by the charging stock circulated through the coil 5. The oil drawn off from the preheater through the l line 49 regulated by a valve 50, may be directed to storage or to further conversion means, not shown.

The evolution of vapors in the still takes place both from the surface of the oil ou the plate 46, and also from the pool of oil maintained in the lower portion of the still.

' These vapors pass off to the dephleglnating column where they are subjected to a refluxing action of the liquid charging stock introduced by means of the spray 37. The still vaporous portion rising to the top of the tower passes olf through the line 14 controlled b a suitable valve, to a partial .condenser W 1ere a portion ot' the vapors are con. densed. The fluid oils discharged from the partial condenser are directed to the pipe 17 in whichpis interposed a trap comprismg a U-shaped pipe such as that shown at 51. In this trap is collected the condensed liquid produced in the partial condenser. A

Portions of this liquidfinay be returned through, the line 52 and introduced into the top of the reiiuxing column where it serves as astabilizing liquid preventing the passing over of the objectionable light fractions which may be separated from the charging stock by the hot vapors. Thus portions otv the fluid hydrocarbons not returned through the line 52, pass on throughthe line 17 to the final condenser and are collected as liquid distillate in the receiver 21.

A uniform pressure may be maintained upon the entire system by controlling the relief valve 24 in the receiving tank, or die'rential pressures on the separate stages may be imposed by the manipulation of the valves in the connecting lines.

By the method described, it is possible to utilize the heat of the system moreedectively, due to the preheating of the charging stock by the reflux liquid and residuum drawn oli 'from the preheated liquid utilized as al refluxing medium. After passing through the heats ing zone, the oil is introduced to the still in a manner to promote the maximum conversion due to the exposing of a large surface of the oil to the heat and pressure conditions in spreading it over the conversion plate, and further causing additional conversion due to Ithe maintenance ot the pool of oil in which the products undergo a digestive reaction.

The vapors are refluxed and a uniform distillate assured by the returning of portions of the overhead product to the top of the column which prevent the lighter fractions from passing over and producing an objectionable Wide range of fractions in the final distillate.

An illustrative run: By treating gas oil of approximately 280 to 32 Baume to temperatures ranging from 700 to 900 F., and pressures lfrom to 250 pounds per square inch, a uniform quality distillate of from 49 to 52 Baume and comprising 40% to of the charging stock was obtained.

I claim as my invention:

l. A process of cracking hydrocarbon oil, consisting in continuously passing oil through a coil located in a furnace "wherein the oil is heated to a conversion temperature, in discharging the oil from said coil into an enlarged zone Wherein'substa'ntial vaporization occurs, in passingthevapors issuing from said enlarged zone to a dephlegmator. in introducing pieheated raW oil toA said dephlegniator to act as a dephlegmating medium or the vapors passing therethrough,

from said dephlegmatrto a primary con# denser in returning portions of the distillateV condensed in said primary condenser to said dephlegmator toals'oact as a dephlegmating medium, in passing the remaining vapors and distillate to a linal condenser and in col' lecting the resulting distillate, in Withdravr-.nt mg mixed raw oil andirefiux condensate col' '110 1n passing the uncondensed vapors issuing stantial pressure on the oil undergoing conversion.

2. A contlnuous process `for cracking I hydrocarbon oil, consisting in heating the oil to a conversion temperature, in directing the heated oil to an en arged zone wherein substantial vaporization occurs, in passin the vapors from said enlarged zone to a dep legmator, in passing the uncondensed vapors from said dephlegmator to a primary condenser, in returning portions of the distillate resultin from said primary condensation to the dep legmator to act as a dephlegmating medium therein,I in passing the remaining distillate and vapors from said primary condenser to a final condenser and in collecting the resulting distillate, and in preheating the raw oil by passing it through a zone in heat interchange relation with reflux condensate withdrawn from the dephlegmator and also in heat interchange relation with residue withdrawn from said enlarged zone and in maintaining a substantial pressure on the oil undergoing conversion.

3. A process of ,treating hydrocarbon oil consisting in passing the oil through a heating zone wherein it is heated to a conversion temperature, in discharging the oil in substantially liquid phase into an enlarged zone, in causing the liquid oil to form in a thin film in said enlarged zone to accelerate the conversion of the oil, in passing the vapors issuing from said enlarged zone to a. dephlegmator, in introducing preheated raw oil to said dephleglnator to physically intermingle with the vapors and act as a dephlegmating medium therefor, in passing the uncondensed vapors from said dephlegmator to a condenser, in returning portions of the condensate to the dephlegmator to act as an additional dephlegmating medium and in colle` ing lthe remaining distillate, in withdrawing lnixed raw oil and reflux condensate from said dephlegmator and in forcing it toa zone of heat interchange wherein it gives up heat to the incoming raw oil, thence passing said mixed raw oil and reflux condensate to said heating zone, in additionally reheating raw oil prior to its introduction into said dephlegmator by passing it through a zone of heat interchange relation with the residual oil Withdrawn from said enlarged zone and in maintaining a self-generated superatniospheric vapor pressure on the oil undergoing conversion.

4. In processes for cracking hydrocarbon oil of the character in which the oil is heated v to a cracking temperature ina single pass only through a heating coil, thence transferred to an enlarged zone wherein separation of vapors from unvaporized oil occurs, the vapors subjected to reflux condensation in a dephlegmator, the reflux condensate returned to said heating coil, and the unvaporized oil constituents withdrawn from said enlarged zone, the improvement which comrises causing the oil delivered from said heating coil to said enlarged zone to flow upon its initial introduction to said enlarged zone in a thin film of substantial area and effecting preheating of the charging oil being supplied to the process by the absorption of heat from the unvaporized oil withdrawn from said enlarged zone and from the reflux condensate by indirect heat exchange in a zone apart from the dephlegmator.l

AUBREY D. DAVID.

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