US1948003A - Treating hydrocarbon oils - Google Patents

Description

Feb. 20, 1934. H, P. PARRIGIN El AL TREATING HYDROCARBON OILS Filed Aug. 2, 1929 S 1. 3, mm a 1 a, a 3 m um Q M W w%% m? ww o MP m 3 w. 2 m4: 4.2 w 3 $3 9 a Patented Feb. 20, 1934 1,948,203 7 raaarnvo maocaaaon oms Homer P. Parrigin and Ralph P. Currie, Gates,

" Tex.,

York, N.

gnors to The Texas Company New Y., a corporation of Delaware Application August 2, 1929. Serial No. 382.904

4 Claim.

This invention relates to the conversion of higher boiling hydrocarbon oils into lower boiling ones for the production of light distillates, such as gasoline and naphtha.

5 The invention relates to a process in which the vapors evolved in a. pressure cracking still are subjected to a preliminary washing or 'dephlegmating to separate out a portion of the heavier constituents and any suspended coke particles before being passed to the regular fractionating tower employed in separating the light distillate, such as gasoline or naphtha, from the heavier constituents which are adapted to be returned to the cracking zone for retreatment. By freeing the evolved vapors of any suspended coke material not only may the fractionating operation be carried on more efliciently, since the deposition and accumulation of coke on the bubble trays or other contact elements employed go in the fractionating operation is largely avoided,

but the cost of cleaning the fractionating tower is'reduced and also the frequency of the need for cleaning is reduced. Furthermore, the reflux condensate formed is substantially free from as coke and thus by providing a condensate for cyclic return to the cracking zone that is free of suspended coke the liability of coke troubles in the heating and cracking zones where the returned constituents are retreated is greatly rese duced.

Various Objects and advantages of the invention will appear from the following detailed description thereof and for the purpose of giving such description reference will now be had, to

as theaccomm yins drawing which isa diagrammatic sectional elevation of anapparatus constructed in accordance-with the invention and constituting an embodiment thereof.

10. represents a heating coil mounted in a suit- 60 able'furnace 11 to which coil the oil to baconverted is introducedby a charging line 12 and pump 18 which draws oil from a suitable source. A plurality of stills ,14, 15, 16 and 1'7 are shown interconnected by vapor equalizing lines 18 and as liquid flow lines 19 and with a transfer line 20 by which the oil heated in-the coil 10 may be introduced to the, battery of stills. The stills are provided with tar or residue draw-ofl lines 21 leading to a common tar line 22 which may so conveniently extend to tankage or to a stripping plant for stripping the pressure tar.

A vapor line 23 is provided for removing vapor from the stills and conducting it'to a preliminary dephlegmator 24. A pump 25 is shown for conducting reflux orwash oil through a charging line 26 to the dephlegmator 24. The pump is arranged to draw all from a suitable source as is more fully explained hereinafter. If desired, contact material such as any of the usual elements employed in dephlegmating or fractionatso ing towers may be employed in the dephlegmator 24. We prefer, however, to either have the dephlegmator entirely free of any such material or to provide only a relatively small number of baflie plates therein with the idea of facilitating a the washing of the vapors so as to separate out any suspended material-without, however, unduly checking or retarding the passage of the vapors through the dephlegmator. A reflux condensate line 29 is provided with a pump 290, one branch 1 line 28 which extends directly to the vapor space of the still 17 at a point just-above the point of connection of vapor line 23, and also with a plurality of branch lines as 30, 31, 32 and 33 extending respectively to thestills 14, 15, 16 and 17. 15 The reflux condensate ih the dephlegmator 24 may thus either be directed to the vapor space or upper end of the still. 17 or distributed among one or more of the stills at the lower ends thereof. It is, we believe, preferable to conduct the a reflux as through. the line 28 back to the upper end of the still 17, and if desired a portion of the reflux may be introduced into the vapor 'spaces of any one or all of the other stills;

A vapor line 84 extends from the dephlegmator g k 24 to a fractionating tower 35 which is preferably constructed in the form of a bubble tower.- The line 36 is provided for withdrawing reflux condensate from the tower 35 and conducting ity to a hot oil pump 37 by which it is forced through .0

aline 38 to the heating coil 10. A vapor line 39 extends from the fractionating tower 35 to a condenser coil 40 and a receiver 41 is provided for collecting the condensate.

The supp y line for the wash oil pump 26 9| may extend to the receiver 41 for withdrawing a portion of the naphtha or gasoline condensate or, to the fractionating tower 35 for withdrawing a portion of the condensate from this tower so that a portion of either 01 these conden- 10o sates may be admitted to the dephlegmator 24 to serve as a dephlegmating means forthe vapors passing therethrough. One distillate that has been used to advantage as a reflux'or washing medium is a distillate obtained from thedistillation of tar or residue withdrawn from cracking stills. Thus residue withdrawn through the line 22 may be directed into a stripping still wherein it may be distilled at reduced pressure and the resultant vapors fractionated to yield, for exno ample, a heavy endpoint naphtha fraction having an end point of the order of 500 F. for instance and this naphtha fraction pumped into the top of one or more of the stills 14,15, 16 and 17 or into the dephlegmator 24. If desired, the dephlegmator may be omitted and the wash oil discharged directly into any of the stills as 14, 15, 16 and 17 and preferably into still 1'7 from which the vapors are withdrawn for passage to the fractionating tower 35. A branch line 26a is indicated for introducing the wash oil directly to the still neck of still 17.

In one method of practicing the invention with the apparatus illustrated the oil to be converted is raised to a cracking temperature in the coil 10 and is passed into the stills 14, 15, 16 and 1'7 where cracking and vaporization take place. Any suitable temperatures and pressures adapted for cracking may be employed. The evolved vapors are passed to the preliminary dephlegmator 24 wherein they are subjected to a washing or dephlegmating action which condenses out a portion of the vapors and separates out any coke or carbon particles, thus leaving the coke-free vapors to pass to the fractionating tower 35 wherein they are fractionatedto form the overhead gasoline or naptha distillate which is taken off through the vapor line 39 and collected as a condensate in the receiver 41, and a reflux condensate which is substantially free from coke and which may be drawn off through the line 36 to the pump 37 by which the condensate is conducted through the line 38 to the coil 10 at a point therein where the oils being combined are at substantially the same temperatures.

It is preferred to carry on in the tower 35 a fractionating operation of an efficient type such as may be accomplished by a bubble tower to produce an overhead distillate of desired end point and a reflux condensate that may be substantially free from constituents boiling within the range of that of the overhead distillate. While a similar efficient fractionating operation may be carried on in the dephlegmator 24 it is not ordinarily necessary to do so, since it is satisfactory to subject the vapors entering the dephlegmator to a mere condensing or dephlegmating operation such as will insure the separation of any coke carried in suspension in the vapors and also may produce a small portion of heavier reflux condensate which need not necessarily be a closely fractionated cut. This reflux condensate may, for example, comprise about 25% in volume of the amount of reflux condensate that is drawn off from the fractionating tower 35 for return to the cracking zone. This condensate withdrawn from the dephlegmator 24 may be passed to any or all of the stills 14, 15, 16 and 17 through the line 29 and its branch lines 30, 31, 32 and 33 but the preferred method of operation is to pass this condensate 'throughthe line 28 directly to the upper portion of the still 17, preferably into the vapor space thereof, so as to effect a washing of the vapors even before leaving the still 1'7. As has been pointed out, in some cases the dephlegmator 24 may be omitted and the wash oil dis charged directly into any or all of the stills 14, 15, 16 and 17 and preferably into the still 1'? from which the vapors are being withdrawn.

By condensing a portion of the vapors before passing them to the regular bubble tower or fractionating tower for more complete fractionation it is possible to increase the capacity of the battery by decreasing the work required of the fractionating tower and decreasing the quantity of hot oil that it is required to pump back from the fractionating tower to the heating coil 10.

If desired, the vapors entering the dephlegmator 24 may be cooled sufllciently that the vapors leaving through the line 34 may be at a temperature below an efficient cracking temperature, such for example as below 700 F., in order to thus inhibit cracking in the fractionating' tower 35 and thus not only facilitate the fractionating operation carried on therein but also avoid the liability of the formation of coke therein.

Although the preferred embodiment of the invention has been set forth in connection with apparatus having a particular construction and arrangement of parts and mode of operation, it is obvious that various changes and modifications may be made therein, while securing to a greater or less extent some or all of the benefits of the invention, without departing from the spirit and scope thereof. Therefore, only such limitations should be imposed as are indicated inthe appended claims.

We claim: I 1. The method of cracking relatively high boil ing hydrocarbon oils for the production of lower boiling products which comprises subjecting such oil to cracking conditions of temperature in an enlarged still chamber, separately withdrawing from said still chamber vaporized cracked products and passing them to a separate zone wherein they are subjected to intimate contact with a relatively cool hydrocarbon oil introduced into said zone to subject said vapors to washing and a small amount of dephlegmation, thereby separating from said vapors in the form of a mixture a relatively small amount of reflux condensate and heavy entrained coky and tarry products of cracking, separately withdrawing at least a portion of the said mixture of condensate and separated tarry and coke particles and introducing the same directly into the vapors within the still which are substantially in the immediate vicinity of the point of withdrawal of vapors therefrom, thereby washing the vapors just prior to their withdrawal from said still for passage to said separate washing and dephlegmating zone, passing the washed vapors from said washing and dephlegmating zone to a separate fractionating zone wherein undesired higher boiling constituents thereof are separated in the form of reflux condensate, separately withdrawing and collecting the fractionated vapors, withdrawing the latter reflux condensate and passing it through an elongated heated passageway wherein it is heated to a substantial cracking temperture, and discharging the highly heated oil from said passageway into said enlarged still chamber for cracking therein.

2. The method of cracking relatively high boiling hydrocarbon oils for the production of lower boiling products which comprises subjecting a liquid body of such oil to cracking conditions of temperature in an enlarged still chamber, separately withdrawing from said still chamber vaporized cracked products and passing them to a separate zone wherein they are subjected to intimate contact with a relatively cool hydrocarbon oil introduced into said zone to subject said vapors to washing and a small amount of Leagues and coke particles and introducing the same directly into the vapors within the still which are substantially in the immediate vicinity of the point of withdrawal of vapors therefrom, thereby washing the vapors just prior to their withdrawal from said still for passage to said separate washing and dephlegmating zone, introducing the remaining portion of said mixture of condensate and separated coke and tarry material directly into the unvaporized body of oil undergoing cracking in said still, passing the washed vapors from said washing and dephlegrnating zone to a separate fractionating zone wherein unde= sired higher boiling constituents thereof are sep arated in the form of reflux condensate, separately withdrawing and collecting the fractionated vapors, withdrawing the latter reflux condensate and passing it through an elongated heated passageway wherein it is heated to a substantial cracking temperature, and discharging the highly heated oil from said passageway into said enlarged still chamber for cracking therein.

3. The method of cracking relatively high boiling hydrocarbon oils for the production of lower boiling products which comprises subjecting such oil to cracking conditions of temperature in an enlarged stillchamber, separately withdrawing from said still chamber vaporized cracked prodnets and passing them to a separate zone wherein they are subjected to intimate contact with a relatively cool substantially completely vaporizable distillate hydrocarbon oil introduced .into said zone to subject said vapors to washing and a small amount of dephlegmation, thereby separating from said vapors in the form of a mixture a relatively small amount of reflux condensate and heavy entrained coky and tarry products of cracking, separately withdrawing at least a portion of the said mixture of condensate and separated tarry and coky particles and introducing the same directly into the vapors within the still which are substantially in the immediate vicinity of the point of withdrawal of vapors therefrom, thereby washing the vapors just prior to their withdrawal from, said still for passage to said therein.

separate washing and deplegniating acne, passing the washed vaporsfrom said washing and 'dephlegmating zone to separate fractionating charging the highly heated oil from said passageway into said enlarged stilt chamber far erase:- ing therein.

4. The method of or asking relatively high boiiing hydrocarbon oils for the production of lower boiling products which comprises subjecting such oil to cracking conditions of temperature in an enlarged still chamber, separately withdrawing from said still chamber vaporized cracked products and passing them to a separate zone wherein they are subjected to a limited amount of dephlegmation, thereby separating from said vapors a relatively small amount of reflux condensate, separately withdrawing at least a portion of the said condensate and introducing the same directly into the vapors within the still which are substantially in the immediate vicinity of the point of withdrawal of vapors therefrom, thereby washi'ng the vapors just prior to their withdrawal from said still for passage to said separate dephlegmating zone, passing the vapors from said dephlegmating zone to a separate fractionating zone wherein undesired higher boiling constituents thereof are separated in the form of reflux condensate, separately withdrawing and collecting the fractionated vapors, withdrawing the latter reflux condensate and passing it through an elongated heated passageway wherein it is heated to a substantial cracking temperature, and discharging the highly heated oil from said passageway into said enlarged still chamber for cracking Home P. PARRIGIN. RALPH P. CURRIE.

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