US2026505A - Converting hydrocarbon oils - Google Patents

Description

Dec. 31, 1935. p. P. BAILEY CONVERTING HYDROCARBON OILS Filed May 16, 1931 INVENT ATTORNEY Patented Dec. 31, 1935 UNITED STATES PATENT OFFICE 2,026,505 CONVERTING mmnooar'mon OILS tion of Delaware Application May 16, 1931, Serial No. 537,816

4 Claims. (01. 196-48) This invention relates to improvements in converting hydrocarbon oils and relates particularly to pressure cracking of petroleum oils to produce satisfactory yields of motor fuel having high anti-knock value while inhibiting the formation of substantial quantities of free carbon or coke and non-condensable gas.

The invention broadly contemplates converting higher boiling hydrocarbon oils, such as topped crude or gas oils, into lower boiling ones at desirably high temperatures where relatively high anti-knock values are developed, and at the same time inhibiting the formation of excess quantities of coke or carbon and gas.

When operating according to the invention, portions of the heavier constituents of the cracked products that are prevented from decomposing into coke or gas are made available for further treatment in the processto be thereby further converted into desirable motor fuel.

Thus among the foremost advantages of my invention is that relatively heavy unclean oils may be processed and, satisfactory yields of high antiknock motor fuel obtained, and continuous oper- 2 ating periods of long duration may be had without formation of substantial quantities of coke and gas.

The invention includes the steps of heating a fresh charge oil to a desirable moderate crack- 0 ing temperature and delivering it into a reaction and contacting vessel from which a vapor is passed to other reaction vessels and is finally dephlegmated to produce a desirable motor fuel and a clean gas oilcondensate. The clean gas 35 oil is heated to a higher temperature than the fresh charge oil and is delivered into the contacting vessel where it is contacted with the fresh charge oil and a residue which is deposited in the further reaction vessels and is passed into 4.0 the contacting vessel. The resultant vapors are combined and passed thru the reaction vessels and dephlegmator as described. A residue which is precipitated in the contacting vessel is withdrawn substantially as fast as it is deposited 4.5 as is also the residue precipitating in the further reaction vessels. 'An appropriate superatmospheric pressure is maintained thruout the system.

Other advantages of the invention may be 50 better understood by' referring to the following description in connection with the accompanying drawing, the single figure of which illustrates diagrammatically a preferred embodiment of apparatus suitable for carrying out the invention.

55 I is a heater, 2 is a combination flash and reaction vessel, 3 is a heater, 4 and 5 are reaction vessels, 6 is a dephlegmator, I is a reflux condenser, 8 is a final condenser, 9 is a trap and I0 is an accumulator.

Oil to be treated, from a source not shown, is 5 delivered thru a line 15 to the heater l and is transferred from the heater thru a line I6 to a plate or spreader near the mid-point in the vessel 2.

Vapors and mist formed in the vessel 2 are 10 delivered overhead thru a line 20 into the vessel 4 while residue deposited in the bottom of the vessel is discharged thru a line 2|.

A line 22 connects the lower portions of the vessels 4 and 5 while drain lines 23 and 24 connect with a transfer line 25 having a pump 26 which leads to a plate or spreader near the midpoint in vessel 2.

A line 30 conducts vapors from the top of the vessel 5 into the lower portion of the dephlegmator 6. Vapors emerging from the top of the dephlegmator pass thru a line 3| into the reflux condenser 1. A line 32 conveys condensate from the condenser 1 back to the dephlegmator 6 while a line 33conducts the issuing vapor to the final condenser 8, and a line 34, from which the trap 9 depends, conveys the final products to the accumulator H] which has a vapor outlet and a liquid outlet 36.

A line 40 having a drain connection 4|, leads to the pump 42 from which lines 43 and 45 lead to the vessel 5 and the heater 3, respectively, and a transfer line 46 leads from the heater 3 to the vessel 2. A cooler 44 is provided inthe line 43.

A pump 50 in a line 5|, leading from the bottom of the trap 9 to the upper portion of the dephlegmator 6, serves to return a portion of the distillate as a coolant to the dephlegmator.

upwardly while the residual portion of the oil over- .50 V

flows the plate and drops down to other baffles or spreader plates which are provided for spreading the liquid oil out film-like to afford'greatest pos- V sible contact with'hotter vapors sweeping over its surface and to minimize the possibility of parti- 5 cles of lighter products becoming imprisoned in the residue and carried down with it.

In addition to the charge oil the residue which is deposited in vessels t and 5 is delivered into the vessel 2 at a higher point. The residue is usually som what cooler than the charge oil when it is delivered into the vessel 2.

Both of these oils are subjected to additional heating in this vessel by the highly heated clean gas oil fraction which is condensed in the dephlegmator 6 and heated in the coil 3. This condensate, which may be drawn from the dephlegmator at approximately 725 F. is passed rapidly thru the heater 3 where its temperature is raised to approximately 1000 or 1050 F. and is immediately delivered to a lower point in the vessel 2 than the charge oil and residue are.

Such of the charge oil and residue as does not vaporize upon entering the vessel 2 overflows the baflies and is subjected to further heating by the upwardly moving highly heated vapors of the clean stock. This heat interchange effects further vaporization of the charge oil and residue and also some condensation of the more highly heated clean stock. Remaining residual portions overflow the lower baiiles and are deposited in the bottom of the vessel from where they are withdrawn substantially as soon as they are deposited, only enough being held in the bottom of the vessel to maintain a liquid seal, that is, so that no quantity of vapor will be withdrawn.

The vapor and mist developing in the vessel 2 is passed thru the vessels 4 and 5 where the time of reaction of the vaporous portion is measurable by its velocity as it is passed therethru. A tempera ture of approximately 87 5 F. is maintained in the reaction vessel 4 and slightly less in the vessel 5. The mist and other liquid particles being formed by polymerization and condensation undergo less time of reaction than the vapors do as they are coalescing continuously and being deposited in the bottoms of the vessels and withdrawn while the vaporous portion is moved from one vessel to the next and finally released from the last one.

All of the vapor produced in the cracking step is subjected to scrubbing in the upper portion of the vessel 5 to remove any tarry or carbon particles which might have been carried along to this point. It is preferable in this scrubbing step to return a portion of the clean condensate from the dephlegmator to one of a series of plates or baliles situated in the top of the last vessel over which the vapor sweeps. In order to avoid returning considerable quantities of this reflux material it is desirable to pass it thru the cooling coil 44.

The scrubbed vapor is passed to the dephlegmator 6 where it is dephlegmated to produce a clean reflux condensate and an overhead vapor. The overhead vapor is passed thru the reflux condenser f and a final vapor is condensed in the condenser 8 to produce a motor fuel distillate, a portion of which may be pumped back continuously to the upper portion of the dephlegmator 6 as a cooling medium. It is preferable to keep the level of condensate drawn down to a minimum in the dephlegmator the same as in the reaction vessels. While the temperature of the oil at this point in the system is not high enough to effect much cracking it is desirable that the condensate which is to be so highly heated be free of tarry or cokey substance.

In the mode of operation just described, the condensate from the dephlegmator 5 which is to be heated to the high temperature is a very clean stock, such for example as a gas oil fraction having a color of approximately [5 on the Lovibond scale thru a cell.

This very clean lower boiling fraction is more difficult to convert than the heavier higher boiling charge oil and residue, but on the other hand it is capable of withstanding higher temperatures without the advanced conversion or decomposition that produces carbon and gas. Converting at the higher temperature serves also to produce motor fuel of relatively high anti-knock value. 10 As the rate of decomposition increases rapidly with the temperature, however, it is of advantage to lower the temperature of this oil almost as soon as a desirably high degree has been attained.

This is accomplished by the quenching effect of the cooler oil and vapor in the vessel 2. By this heat interchange an average temperature of the mixture in the vessel 2 is effected at which conversion of the voluminous vapor and mist continues at a somewhat slower but satisfactory rate and as the rapidly precipitating liquid which is deposited in the bottom of the vessel is withdrawn substantially as soon as it is deposited it does not have time to further decompose to form carbon.

t is believed that the cooler quenching oil may also have a solvent effect on incipient gas and coke in the highly heated clean stock.

Due to the conditions set up in the vessel 2 it will not always be possible to remove all of the gas oil fraction from the residual portion of the residue and charge oil which is deposited in the bottom thereof. It may therefore be desirable to subject this residue to autogenous distillation at reduced pressure to strip it of the gas oil fraction which may be returned to the system with the charge oil for further treatment.

While I have described a rather specific mode of operation, it is to be understood that I do not wish to limit my invention in this manner, but prefer it to be limited only by the appended claims in which the invention is defined.

I claim:

1. The process of converting higher boiling hydrocarbon oils into lower boiling ones that comprises heating a condensate oil to high cracking temperature in transit through a heating coil, passing the heated oil at a high cracking temperature into an enlarged cracking zone maintained at cracking temperature wherein separation of vapors from liquid occurs, introducing oil into said enlarged cracking zone, at a temperature lower than that of said condensate oil introduced, to thereby lower the temperature of reaction therein as well as subject the cooler oil to cracking, withdrawing separated liquid from the enlarged cracking zone at a rate adequate to prevent the accumulation of a body of liquid therein, passing separated vapors to a secondary cracking zone wherein the vapors are maintained at a cracking temperature to effect further cracking of the vaporous constituents, preventing the accumulation of liquid in said secondary cracking zone by the rapid withdrawal of liquid therefrom, and conducting the withdrawn liquid to said enlarged cracking zone, passing the vapors to a fractionating zone and subjecting them to fractionation therein to separate out a final light distillate and a reflux condensate and conducting said reflux condensate to said heating coil.

2. The process of converting higher boiling hydrocarbon oils into lower boiling ones that comprises heating a condensate oil to high cracking temperature in transit through a heating coil, passing the heated oil at high cracking tem- 15 perature into an enlarged cracking zone maintained at cracking temperature wherein separation of vapors from liquid occurs, separately heating charging stock to a moderate cracking temperature lower than that to which said condensate oil is subjected in said heating coil and directing the heated charging stock into said enlarged cracking zone, withdrawing separated liquid from said enlarged cracking zone at a rate adequate to prevent the accumulation of a body of liquid therein, passing separated vapors to a secondary cracking zone wherein the vapors are maintained at a cracking temperature to effect further cracking of the vaporous constituents, preventing the accumulation of liquid in said secondary cracking zone by the rapid withdrawal of liquid therefrom, and conducting the withdrawn liquid to said enlarged cracking zone,

passing the vapors to a fractionating zone and subjecting them to fractionation therein to separate out a final light distillate and a reflux condensate and conducting said reflux condensate to said heating coil.

3. The process of converting higher boiling hydrocarbon oils into lower boiling oils which comprises heating a cracking stock to a moderate cracking temperature of the order of 825 F., passing the heated oil into a contacting and vaporizing zone thru which evolved vapors rise maintained at a cracking temperature, drawing off vapors from the upper part of said zone, passing them to a subsequent reaction zone for further reaction while maintained at cracking temperatures, withdrawing vapors from the reaction zone and subjecting them to fractionation between motor fuel as vapor and a heavier oil as condensate, withdrawing residue from the reaction zone, heating the condensate to' a high cracking temperature of the order of 1000 F., and passing it into said contacting and vaporizing zone at a point below the point of entry of the heated cracking stock, passing the residue withdrawn from said reaction zone into the contacting and vaporizing zone at a point above the point of entry of the heated cracking stock, ef- 5 fecting contact between rising vapors and falling liquid in such zone, and withdrawing-residual liquid from the bottom of the zone at a rate adequate to prevent the accumulation of liquid therein. 10 4. The process of converting higher boiling hydrocarbon oils into lower boiling ones that comprises heating a condensate oil to high cracking temperature in transit through a heating coil, discharging the heated oil from the heating coil 15 and passing it into an enlarged cracking zone maintained at cracking temperature wherein separation of vapors from liquid occurs, introducing oil into said enlarged cracking zone, at a temperature lower than that of said condensate 20 oil discharged from said heating coil, to thereby lower the temperature of reaction therein as well as subject the cooler oil to cracking, withdrawing separated liquid from the enlarged cracking zone at a rate adequate to prevent the accumu- 25 lation of a body of liquid therein, passing separatedvapors to a secondary crackingzone wherein the vaporsare maintained at a cracking temperature to effect further cracking of the vaporous constituents, preventing the accumulation of '30 liquid in saidsecondary cracking zone by the rapid withdrawal of liquid therefrom, and conducting the withdrawn liquid to said enlarged cracking zone, passing the vapors to a fractionating zone and subjecting them to fractionation 5 therein to separate out a final light distillate and a reflux condensate and conducting said reflux condensate to said heating coil.

DOUGLAS P. BAILEY. 4o

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