US1930730A - Treating hydrocarbon oils - Google Patents

Description

Oct. 17, 1933. w. M. STRATFORD TREATING HYDROCARBON OILS 2 Sheets-Sheet 1 Filed July 25. 1929 I avwmtoz K MWA Oct. 17, 1933.

W. M. STRATFOR D TREATING HYDROCARBON OILS Filed July 25, 1929 2 Sheets-Sheet 2 LIL.

UZR IZOD u (mt A TTORNE Y Patented Oct. 17, 1933 UNITED STATES PATENT OFFICE TREATING HYDROCARBON OILS William M. Stratford, New York, N.- Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware This invention relates to the pressure distillation of hydrocarbon oils wherein higher boiling hydrocarbons are converted into lower boiling products, such as gasoline and naphtha.

In cracking hydrocarbon oils by distillation under pressure the tar or residue withdrawn from the cracking still necessarily contains gasoline or naphtha constituents, as well as heavier fractions such as gas oil, and it is common practice to distill the residue thus withdrawn at reduced pressure to recover therefrom gasoline or naphtha constituents and also so-called cycle stocks which are adapted for further treatment for conversion into gasoline or naphtha.

In accordance with my invention the cracking operation is carried on in a plurality of stills and steam or other fluid adapted to lower the partial pressure of the fluid being distilled is admitted into the still or stills from which the residue is being withdrawn, so that the residue may be thus freed of lower boiling constituents before it is withdrawn from the cracking zone. Thus the gasoline or naphtha constituents, as well as a portion of the gas oil or cycle stock, may be removed from the residue before it is withdrawn from the cracking stills. This residue may then be further distilled at reduced pressure to obtain the rest of the cycle stock or distilled to such an extent as may be desired. My invention thus has the advantage of removing all of the gasoline or naphtha constituents, made in the cracking process, directly from the cracking stills and since the residue withdrawn from the cracking stills may be free from gasoline constituents it is unnecessary to use expensive fractionation equipment in the residue stripping operation. By

carrying on the dephlegmation or fractionation of the evolved vapors from the cracking stills at superatmospheric pressure, such for example as approximately the pressure of the stills, the entire quality of gasoline or naphtha formed in the cracking operation may be subjected to such polymerizing or stabilizing action as may take place in the pressure dephlegmator or in any other apparatus that may be associated directly with the pressure stills.

In order to more fully disclose the invention reference will now be had to the accompanying drawings wherein: Figure l is a diagrammatic sectional elevation of an apparatus constructed in accordance with the invention and constituting an embodiment thereof. Figure 2 is a diagrammatic sectional elevation of a modification thereof.

In the drawings a coil and drum or tube and tank cracking system is shown but it is to be understood that the invention is not limited to this particular type of cracking operation, since it may well be practiced in any method of cracking in which the oil is distilled in two or more stills or separate bodies of oil are subjected to the cracking operation. 9 designates a pump adapted to draw charging stock from a suitable source and introduce it to a heating coil 10 mounted in a furnace 11 adapted to heat the oil to the cracking temperature desired. A battery of cracking stills consisting of stills 11a, 11b, 11c and 11d is shown. A transfer line '12 is shown extending from the coil 10 to oneof the stills, 11a. These stills may either be heat insulated or mounted in a suitablefurnace. The first three stills, 11a, 11b and 110, are interconnected by vapor equalizing lines 13 and 14. A liquid flow line 15 interconnects the upper ends of the still's 11a and 11b,

a liquid flow line 16 interconnects the lower ends of the stills 11b and 110 and flow line 17 connects the upper end of the still 110 with the still 1101, so as to thus establish a current or flow of oil through the several stills. A vapor line 18 is shown extending from the still 11d and a vapor line 19 extending from the still 110, which lines connect with a common vapor line 20 extending to a dephlegmator 21. It may be noted that the cracking stills may be interconnectedin such. manner as may be desired with such an arrangement of liquid flow lines and vapor equalizing lines as it is desired to employ, although it may be stated that it is believed that the particular arrangement shown is an advantageous one for practicing .the invention.

Each of the stills is equipped with valved tar or residue draw-off lines as 22a, 22b, 22c and 22d. The line 22d is shown extending to a tar stripping still 23 and the line is provided with a pressure reducing valve 24 so that the pressure may be reduced in the chamber 23 for distillation. The still 23 is shown equipped with a line 25,for introducing steam or other gas to aid in the distillation in cases where the desired amount of distillation cannot, be effected merely by the contained heat in the residue. The line 2211 is provided with a branch line 26 so that the residue withdrawn from the still 11d may, if desired, be passed to tankage or to distilling means other than that of the still 23. A vapor line 27 extends from the still 23 to a condenser 28 and a tank to a pump 39.which is adapted to pump the condensate through a line 40 to the coil 10.

The dephlegmator 21 may be in the form of a bubble tower or other suitable fractionating equipment and is provided with a vapor line 30 which extends to a condenser coil 31. A receiving drum 32 is indicated for collecting the pressure distillate. A line 33 is shown for withdrawing reflux condensate from the dephlegmator 21 to a pump 34 by which this condensate may be forced through a line 35 to the heating coil 10.

The still 11d is shown provided with a line 36 for introducing steam or other gas adapted to lower the partial pressure of the oil being distilled therein and thus promote vaporization in this still. The still may be constructed, as shown, of greater volume than that of any of the other stills 11a, 111) or 110, in order to take care of the increased volume of vapor that may be present in this still.

In practicing the invention with the apparatus thus illustrated gas oil or other suitable charging stock is introduced by the pump 9 to the coil 10 wherein the oil is raised to a cracking temperature and is then passed through the transfer line 12 into still 11a. The oil passes through the successive stills 11b and 110 into the still 11d, cracking temperatures and pressures being maintained in the several stills. The temperatures and pressures employed in cracking are well known and need not be restated herein, but temperatures of the order of 750 Ft-950 F. under 100-600 pounds pressure may be given as a specific example. The bulk of the tar or residue is withdrawn from the still 11d through the line 22d, and the lines 22a, 22b and 220 are not normally employed for the withdrawal of tar, except in cases of emergency or only occasionally in order to satisfy the operator that these lines may not be plugged up with coke. Into the still 11d, from which substantially all of the tar or residue is withdrawn, steam may be introduced through the line 36. The still 11d may be held at approximately the same pressure as that of the other stills but due to the introduction of the steam, which is preferably superheated, the oil therein may be stripped of its gasoline or naphtha constituents. The steam may be introduced. at a temperature sufiicient to prevent a drop in temperature in still 11d. or this still may be held at a lowertemperature than that obtaining in the other stills. It is preferable to introduce suflicient steam so that a portion of the kerosene or gas oil constituents may also be removed, so as to thus insure that all of the gasoline constituents will pass out as vapor through the line 18.

The vapors from the line 18 combine with those passing through the line 19 from the other cracking stills and are directed by the line 20 into the fractionating tower 21 for fractionation so that the total gasoline or naphtha yield in the cracking operation may thus be separated out as an overhead vapor fraction in the tower 21 and collected in the receiver 32, while the heavier constituents of higher boiling point than that desired in the gasoline fraction are drawn off by the line 33 and picked up by the pump 34 which conducts them to the heating coil 10. If desired,

steam may be introduced into the lower part of the fractionating tower 21 to insure that all the gasoline constituents may be removed from the reflux condensate before it is withdrawn from the tower.

The tar or residue withdrawn from the still 1111 through the line 24 thus freed of its lighter constituents, preferably of all of its gasoline components, is directed by the line 24 into the still 23 wherein it is distilled at reduced pressure, such for example as atmospheric pressure or thereabouts. By having no gasoline components in the residue thus introduced to the still 23 there is ordinarily no necessity for any fractionating equipment for the evolved vapors and thus these vapors may be readily condensed in the condenser 28 and collected in the tank 29. However, it may be pointed out that the practice of the invention does not preclude the fractionating of the vapors from the still 23 into a plurality of cuts, such for example as a light gas oil and a heavy gas oil, if it is desired to do so. The distillate collected in the receiver 29 may be pumped back to the coil 10 by the pump 39 or may be sent to tankage, treated in another cracking unit or utilized as may be desired. The stripped residue 'or fuel oil formed in the still 23 may be drawn off by the line 37 to tankage.

It may be pointed out that if desired instead of drawing the bulk of the tar from one still, such as 11d, the tar may be drawn from a plurality of stills, such as for example the stills 11c and 11d, and steam introduced into each of these stills from which the tar is withdrawn. Similarly the transfer line 12 may connect with more than one still. Thus for example in the four still battery illustrated in Figure 2, the transfer line 12 is provided with a branch line 1212 so that heated oil from the coil 10 may be delivered into either still 11a or both 11a and 11b, while tar is withdrawn from, and steam introduced into, either still 1111 or both stills 11c and 11d. Lines 36 are shown for introducing steam into stills 11c and 11d and line 220 is shown connected to line 22d for withdrawal of the tar.

In practicing the invention all of the components of desired end point for the gasoline or naphtha distillate may be taken off as an overhead distillate from the fractionating tower 21 and collected in the receiver 32. Thus for example in case itis desired to make a 400 end point gasoline all of the constituents boiling at 400 F. or lower are taken 011 from the cracking stills and collected as distillate in the receiver 32 while the residue withdrawn from the still 11d contains no components boiling at 400 F. or lower. Thus not only is the entire gasoline product subjected to such polymerizing or stabilizing action as may occur in the fractionating tower 21 but also this entire product may be given such other stabilizing treatment as may be desired, such as by passage through fullers earth or clay directly as taken off the pressure stills. Thus a clay treating tower may be interposed in the line 30, the resultant polymers or condensate being run back to the fractionating tower 21 and the vapors passed into the condenser 31; or the condensate may be passed directly to treating or stabilizing equipment, such as clay treating apparatus or a sulfuric acid treating system or other chemical treating system.

Although the preferred embodiment of the invention has been set forth in connection :with

apparatus having aparticular construction and I claim:

1.-In the conversion of higher boiling hydrocarbon oils into lower boiling ones, the process that comprises subjecting hydrocarbon oil to cracking and vaporization in a cracking zone comprising a still under superatmospheric pressure wherein the evolved vapors comprise low boiling constituents and higher boiling constituents, withdrawing from the cracking still and passing to a stripping still products undergoing cracking and containing constituents comprising components of the same boiling point as those of the low boiling constituents contained in said vapors evolved in the cracking still, while not reducing the pressure in the stripping still introducing thereintc a fluid adapted to lower the partial pressure therein so that vapors are evolved comprising said low boiling constituents contained in the products introduced to the stripping still, passing the evolved vapors from said cracking still and said stripping still to a common fractionating zone and fractionating them therein under said superatmospheric pressure withdrawing residue from the stripping still substantially free from said low boiling constituents and conducting it to a second stripping still maintained under a materially reduced pressure to thereby effect vaporization to vaporize oif higher boiling constituents adapted for recycling to the cracking zone for further cracking, separately collecting said constituents as a condensate and conducting said condensate substantially free from said low boiling constituents to the cracking zone.

2. In the conversion of higher boiling hydrocarbon oils into lower boiling ones, the process that comprises subjecting hydrocarbon oils to cracking and vaporization in a cracking zone under superatmospheric pressure comprising a still chamber wherein the evolved vapors comprise low boiling constituents, separately withdrawing said vapors from said still and passing them to a condensing operation, separately withdrawing from said still unvaporized constituents undergoing cracking and passing them to a second still chamber wherein they are collected in a body and maintained at cracking temperature under superatmospheric pressure, passing through the body of unvaporized liquid in said second still an inert fluid capable of loweringthe partial pressure to effect stripping of low boiling products from said unvaporized products, separately withdrawing vaporous products from said second still and passing them to the aforesaid condensing operation, separately withdrawing the unvaporized products from said second still and passing them to a zone of substantially lower pressure wherein a portion of said products is vaporized, separately cooling the latter resulting vapors and returning the condensed portions thereof ,to the oil undergoing cracking.

3. In the conversion of higher boiling hydrocarbon oils into lower boiling ones, the process that comprises subjecting hydrocarbon oils to cracking and vaporization in a cracking zone under superatmospheric pressure comprising a still chamber wherein the evolved vapors comprise low-boiling constituents, separately withdrawing said vapors from said still and passing them to a fractional condensing operation, separately withdrawing from said still unvaporized constituents undergoing cracking and passing them to a second still chamber wherein they are collected in a body and maintained at cracking temperature under superatmospheric pressure,

passing through the body of unvaporized liquid in said second still a highly heated inert fluid capable of lowering the partial pressure to effect stripping of low boiling products from said unvaporized products, separately withdrawing vaporous products from said second still and passing them to the aforesaid fractional condensing operation, separately withdrawing the unvaporized products from said second still and passing them to a zone of substantially lower pressure wherein a portion of said products is vaporized, separately cooling the latter resulting vapors and returning the condensed portions thereof to the oil undergoing cracking.

4. In the conversion of higher boiling hydrocarbon oils into lower boiling hydrocarbon oils the process which comprises passing a flowing.

stream of such oil through a heating zone wherein it is heated to cracking temperature, passing the heated oil successively through a plurality of series-connected reaction chambers, maintaining bodies of unvaporized products in each of said chambers at cracking temperature and under superatmospheric pressure, withdrawing vaporous low-boiling products from all of said reaction chambers and subjecting them to condensation in a single zone, passing through the body of unvaporized liquid in a subsequent one of said reaction chambers an inert fluid capable of lowering the partial pressure to effect stripping of lowboiling products from said'unvaporized' products, separately withdrawing the stripped unvaporized products from said subsequent reaction chamber and passing them to a zone of substantially lower pressure wherein a portion of said products is vaporized, and separately cooling the latter resulting vapors and returning condensed portions thereof to the oil undergoing cracking.

5. In the conversion of higher boiling hydrocarbon oils into lower boiling hydrocarbon oils the process which comprises passing a flowing stream of such oil through a heating zone wherein it is heated to cracking temperature, passing the heated oil successively through a plurality of series-connected reaction chambers, maintaining bodies of unvaporized products in each of said chambers at cracking temperature and under superatmospheric pressure, withdrawing vaporous low-boiling. products from all of said reaction chambers and subjecting them to fractional condensation in a common fractionating zone maintained under superatmospheric pressure, passing through the body of unvaporized liquid in a subsequent one of said reaction chambers a highly heated inert fluid capable of lowering the partial pressure to effect stripping of low-boiling products from said unvaporized products, separately withdrawing the stripped unvaporized products from said subsequent reaction chamber and passing them to a zone of substantially lower pressure relative to that maintained in said fractionating zone wherein a portion of said products is vaporized, and separately cooling the latter resulting vapors and returning the condensed portions thereof to the oil undergoing cracking.

6. In the conversion of higher boiling hydrocarbon oils into lower boiling hydrocarbon oils theprocess which comprises passing a flowing stream of such oil through a heating zone wherein it is heated to cracking temperature, passing the heated oil successively through a plurality of series-connected reaction chambers, maintaining bodies of unvaporized products in each of said chambers at cracking temperature and under superatmospheric pressure, withdrawing vaporous low-boiling products from all of said reaction chambers and subjecting them to condensation in a common condensing means maintained under superatmospheric pressure, passing through the body of unvaporized liquid in a subsequent one of said reaction chambers an inert fluid capable of lowering the partial pressure to effect stripping of low-boiling products from said unvaporized products, separately withdrawing the stripped unvaporized products from said subsequent reaction chamber and passing them to a zone of substantially lower pressure relative to said condensing means wherein a portion of said products is vaporized, and separately condensing the latter resulting vapors and returning the condensed portions thereof to the stream of oil flowing through said heating zone.

7. In the conversion of higher boiling hydrocarbon oils into lower boiling hydrocarbon oils the process which comprises passing a flowing stream of such oil through a heating zone wherein it is heated to cracking temperature, passing the heated oil successively through a plurality of series-connected reaction chambers, maintaining bodies of unvaporized products in each of said chambers at cracking temperature and under superatmospheric pressure, withdrawing vaporous low-boiling products from all or said reaction chambers and subjecting them to fractional condensation under superatmospheric pressure in a single fractionating zone, passing through the body of unvaporized liquid in a subsequent one of said reaction chambers a highly heated inert fluid WILLIAM M. STRATFORD.

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