US2011479A - Process for treating hydrocarbon oil - Google Patents

Description

Aug. 13, 1935. J. H. FORRESTER I PROCESS FOR TREATING HYDROCARBON OIL.

Filed Feb. 20, 1933 w E N R O m 9 Q. Q a- I :Hm HUN. l ll 8 NN &

Patented Aug. 13, 1935 UNITED" STATES PROCESS FOR TREATING HYDRO-- CARBON OIL Jay H. Forrester, Hammond, Ind., assignor to Standard .Oil Company (Indiana), Chicago, 11]., a corporation of Indiana 'ApplicationcFebruary 20, 1933, Serial No. 657,643

1 Claim.

My invention relates to the art of pyrolytic conversion or cracking of petroleum oils and the like and has for an object the provision of a process of and apparatus for'cracking relatively high boiling oils, such as gas oil, into lower boiling products, the process and'apparatus being particularly adapted to produce a satisfactory yieldvof gasoline products having a high antiknock value when used as motor fuel, and being capable of employment for extended periods of time with high operating efliciencies and a minimum of operating difiiculties.

My invention has for further objects such additional improvements in operative advantages and results as may hereinafter be'found to obtain.

My invention is particularly adapted to beemployed in conjunction with a method of cracking hydrocarbon oil, designated generally as lowliquid-level operation, in which an oil is heated to cracking temperature under pressure, as, for example, While in transit through a pipe coil, and the resultant cracked products are delivered to one or more enlarged stills or reaction chambers from which vapors and liquids are separately removed, the latter at a rate sufficient to maintain the bulk of the material within the chamber or chambers in the form of vapors and to prevent the accumulation of-more than small amounts of liquid in the bottom of the chamber or chambers. The vapors thus withdrawn are fractionated to recover a heavy fraction: and a lighter fraction therefrom, the heavy fraction being recycled through'the cracking zone if desired, while the liquid products, or tar, removed from thereaction vessel or vessels may be withdrawn from the system. a

. By means of my present invention, prior operating difficulties are overcome. Cracking is successfully carried out principally in the vapor phase to give cracked distillate having an improved anti-knock value, while avoiding excessive coke formation in the reaction chambers and maintaining high yields and high operating According to my invention the stills or vapor chambers are substantially unobstructed internally and are as free as possible from intruding surfaces upon which carbon or coke is likely to The stills or chambers are opmoved as fast as formed or evaporated in the course of the process.

The heated partially cracked products from the pipe coil are discharged into the interior 'or interiors of the still or stills in an upward direc- 5' tion, preferably by means of a vertically disposed conduit terminating a short distance above the liquid level within the still or a little above the bottom of the still, but in any event discharging I upwardly into that portion of the still which is in occupied by materials in the va'por'phase.

Provision is made for withdrawing vapors from the upper portion of the still or stills and for removing tar or other liquid products from the bottom of the same. The vapors are subjected to fractional condensation in'the usual manner and all or a portion of the heavier condensate may be recycled forfurther treatment.

In order that my invention may be clearly set forth and understood, I now describe, with ref- 20 erence to the drawing accompanying and forming a part of this specification, a preferred form and manner in which my invention maybe embodied and practiced. In this drawing,v

Figure lis a somewhat diagrammatic elevational view of apparatus for cracking petroleum oil constructed in accordance with my present in- Vention; and r Figure 2 is a View, partly in elevation and partly in vertical section, of a portion of the apparatus shown in Figure l, on an enlarged scale.

Similar reference numerals designate similar parts in each of the views of the drawing.

Referring now to the drawing, the oil to be cracked, for example, a gas oil, is introduced from a suitable source (not shown) through a conduit l, and is forced by a pump 2 through a conduit 3, a heat-exchange coil 4 and a conduit 5 into a pipe coil '5 located within a suitable heating furnace l, where the oil is heated to a cracking temperature, for example, a tempera ture of 895 F. The heated oil then passes through a transfer line H to a plurality of insulatecl reaction chambers or stills A, B, Cfand D, being introduced into the bottoms ofthe stills h A, B, C, and'D through'branch conduits I3 having valves M and terminating in vertically disposed conduits 15 located within the interiors of the stills A, B, C, and D.

In the preferred instance, each of the stills DO A, B, C and D is provided with a device N associated with a valve il in an outlet pipe i8 for maintaining a predetermined liquid level in the bottom of the corresponding still and the upper ends of the conduit l5 terminate a short 55 devices I6. I have found that a distance of three feet in a still forty feet high gives satisfactory results insofar as the specific operating instance set forth herein is concerned.

It will be observed from the drawing that the connections between the pipes l3 and the transfer line I] are such that the material flowing from thecoil l0 enters the stills A, B, C, and D in parallel, the valves l4 being operatedin such a manner as tosecure satisfactory distribution of the preheated material to the several stills,

and preferably in such manner as to maintain the temperatures in the several stills A, B, C, and

D substantially the same. Tar'or other residual liquid is removed from the bottom of the stills A, B, C, and D through the'outlets l8 which may lead, as shown, to a manifold line l9, while vapors are removed from the tops of the stills A, B, C and D. In the specific instance illustrated, the means for removing the vapors comprises vapor conduits 2|, 22 and 23 connecting the tops of the several stills in series and a vapor conduit 24 leading-to a bubble tower orfractionating tower25 in the upper portion of which is located the heat-exchange coil 4. The interior of the tower 25 is provided with suitable fractionating means such as bubble-cap plates or trays 26, screen plates, disk-and-doughnut trays or the like. s

As the vapors pass up through the tower 25, fractionation takes place under the influence of cooled reflux oil condensed by contact of the hot vaporswith the coil 4 and limited fractional condensation of the vapors is effected. A float device 21 may be provided in the bottom of the tower 2.5 for maintaining a suitable liquid level, and condensate or backtrap from the bottom of the tower 25 may be recycled throughaconduit 28, a pump 29 and a conduit 3| tothe coil6 or a portion thereof for further. cracking treat- 7 ment.

Uncondensed cracked distillate vapors reaching the top ofthe tower 25 are removedtthrough the vapor line 33 and pass to whatever condensing equipment may be provided for them.

In one instance extremely successful results were obtained in the treatment of'gas oil derived from a Mid-Continent crude, which gas oil had a specific gravity of 26 A. P. I. This gas oil was brought to a temperature of 895 F. at the outlet of the coil ID. The coils 6 and l0,the stills A, B, C, and D and the tower 26 were maintainedunder a pressure of about 310 pounds per square inch. 'Iemperatures of 860 F. and 840 F. weremaintained in the bottoms and tops, respectively, of the stills A, B, C, and D, whiletemperatures of 800 F. and 550 F.- were maintained in the bottom and top outlet, respectively, of the tower 25.

-;Operating under these specificconditions, it

. was found that the naphtha or gasoline produced was considerably improved in anti-knock quality with respect to previous operations 'in which the treatment of materials in the stills A, B, C, andD was carried out largely in the liquid phase. Thus, naphtha having an octane number '71 was produced as compared with naphtha having an octane number of 63 produced in previous high-liquid-level operations. Naphtha produced according to the process of my in-' vention contained as much as of unsaturates I observed,

It was also found that, in comparison to pre vious high-liquid-level operations, the amount of gasoline produced was substantially unchanged although a smaller quantity of tar was produced I by myprocess;

I All of these advantageous results were obtained without, substantial decrease in efficiency of operating time and without excessive coke formation .or high maintenance cost.

It will be'obvious to those skilled in the art that while I have described my invention hereinabove with respect to a particular operation and embodiment, it is susceptible of considerthere is substantially no liquid level therein, liquid oil being removed as fast asitgseparates, without permitting any accumulation thereof in the still vessel or vessels, a i

x ;My invention-is, therefore, not limited to all the specific details ,of the illustrative example or examples set forth hereinabove, but may vari ously beembodiedandpracticed within the scope of the claim hereinafter .made. 1

Iclaim:

lower-boiling products which comprises heating a hydrocarbon oil to cracking temperature under superatmosphericpressure while in transit through a heated pipe coil, discharging the stream of highly heated products therefrom into the lower portion of anelongated interiorly unobstructed. vertically. disposed. reaction, space wherein said products undergo cracking under said pressure by their contained heat, separately removing'vapors from'the'upper portionof said space and passing them to a suitable condensing operation, and withdrawing liquid products from the lower portionof said reaction space at a rate sufiicient to prevent the accumulation of liquid 'therewithin above a predeterminedlevel in the lower portion thereof, the said stream of highly heated products from saidcoil being discharged vertically upwardly into said'reaction I The method'of -converting hydrocarbon oil'into 4

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