US1738386A - Vapor fractionation - Google Patents

Description

Dec, 3, 192.. J. c. MORRELL. 1,738,386

VAPOR FRACTIONATION Filed April 25, 1927 lll lit

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"l he present improvements relate more particularly to a process and apparatus dc si ned 'lor the elticient fractionation oil vapors w.1ereby the sufiiciently converted fractions will be separated from the insuthciently converted lractions,,and the latter returned lor retreatment.

llhe present invention is particularly applicable to the fractionation oil heated hydrocarbon vapors produced in the craclring or distillation ot t 1e hydrocarbon oil, but it is to be understood that in its broad concept, the invention is adapted tor the tractionation o'l vapors llrom any source.

'llhe invention is adapted to be carried out under atmospheric, superatmospheric, or sub atmospheric pressure. I

lln the lractionation of hydrocarbon oil vapors, particularly those produced in the cracking and conversion cl hydrocarbon oil under conditions ol' heat and superatmospheric pressure, it i is desirable that manimum intimate contact be had between the vapors and the cooling liquid, llt has also been lound to be ol' advantage to main tain pools ot liquid in separate stages in the 'lractionating instrumentality whereby there is a tendency toward equilibrium between the liquid and vapors in each stage, and ot more importance, advantageis talren oil the time element during which the liquid in the diderent pools is subjected. to the varying condi tions within the instrumentality. The vapors which escape condensation, and which are removed from the upper end oil "the tram tionating instrumentality will be 'lound to be substantially unitorm in composition, and upon testing will be tound to have been eciently tractionated.

lln such types of 'lractionating towers wherein a body of liquid is maintained upon a deck, and the vapors ascend through open ings in a cap over a vapor riser above the body oil liquid where the velocity of the vapors is high, entrainment may occur so that the liquid descending through the risers in the deck will be held back, thus interfering with the proper operation of the tower, This may be avoided by designing the tower so as to have a low vapor velocity through tear. tlerial l lo. ltlhfillh.

the risers and also relieving the declr Oil some oil its liquid by orifices in the deck plate,

Another method ol avoiding entrainment, which comprises the subject matter ot the present invention, insures the positive descent ol desired quantities of the liquid by having a down-flow pipe or a series oil downtlow pipes in the declr through which sub stantially all at the liquid is caused to descend, permitting at the same time tree ascent ot the vapors through the risers, which ascent may be at a low, or even a high velocitylilntramment ol the descending li uid through the down-dew pipes, isavoideddby maintaining a liquid seal.

"lllhe utility oil the invention, as well as various objects and advantages will be more apparent trom the llollowing description in the drawings, l ig. l is a vertical see tional view ot a l'ractionatin tower equipped l to carry out the purpose ot the present invention.

ltig. it is a cross sectional view talren on line 2-2 o'l l,

Fig. 3 is a truss sectional view talren on line 3-3 ol Fig. l.

Fig. l is an enlarged lragmentary vertical sectional view ot the declr illustratin the cap}, vapor risers, down-tlow pipes and liquid sea ltelerring more particularly to the drawings, l designates a shell which may be dis posed vertically and which may talre any formic 'lhis shell may talre the l'orm oil the usual metal tractionating tower provided with the covers 2 through which the shell may be cleaned. The shell may also be provided with vapor inlet 3 in which may be interposed the valve 4, the vapor outlet 5 in which may be interposed the valve ti, the liquid inlet 'i" in which may be interposed the valve it, and liquid outlet 9 controlled by the valve 10-. Disposed within the shell and spaced suitable distances from each other, are a numberol" declrs it which may be supported on the annular lugs 12, if desired. Each oil the dec lrs ll is provided with a number of vapor risers l3 projecting above the surface oi the deck, over the upper end of which are placed the caps 14. As a feature of the invention, each lid lit)

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of the caps may comprise an annular flange 15, the lower edge of which is disposed a short distance above the surface of the deck 11 and the upper edge connected to a roof 16, which roof may slope toward its edge from the central point indicated. Perforations 17 may be provided in that portion of the annular flange 15 which lies between the upper edge of the vapor riser 13 and the point of connection to the roof 16, the purpose of which will be hereinafter more particularly explained. Downflow pipes 18 are positioned in each deck 11, having a portion projec'ting above and below the deck. The height of the down-flow pipe within the deck 11 is carefully computed, and is preferably such as-to maintain a pool of liquid on each deck 11, the arrangement being such that the liquid will over-flow the upper edge of the down pipe and flow therethrough, collecting in an imperforate depression 19 formed in the perforated plate 20.

The descending liquid spreads out over the perforated plate, and is distributed on the caps in the deck below, it being understood that the relative size and number of the perforations is so computed that no substantial amount of liquid will collect thereupon. The arrangement is such that a perforated plate or grid 20 is positioned between each of the first mentioned plates or decks 11, which carry the risers 13 and downflow pipe 18, but which are otherwise imperforate.

The operation is as follows: Heated vapors enter through the vapor line 3 into the interior of the shell 1 and pass upwardly through the perforations in the perforated plate 20, after which they ascend through the vapor risers 13 and through the orifices 17 in the annular flange 15 of the cap. Liquid will collect on the deck 11, building up to a height depending upon the height of the down-flow pipe 18. Excess liquid will overflow the upper edge of the down-flow pipe and will collect in the depressed portion 19, which in effect forms a liquid seal to prevent the vapors from ascending through the down pipe 18 and thus preventin the entrainment of liquid which is descen ing in the down pipe 18.

It is to be noted that the lower edge of this down pipe 18 is below the upper surface of the plate 20 whereby a small pool of liquid will collect.

From the foregoing, it will be apparent that eflicient fractionation will take place as the vapors ascend throughthe tower. In each step of the fractionating tower, an equilibrium will be maintained between the liquid and vapors so that there is a progressive temperature change throughout the tower. The vapors which escape condensation and which are removed through the vapor outlet 5, will be found to be of substantially uniform composition. It is to be noted that intimate conmesses tact, equilibrium between vapors and liquid in each step, and time element for the pools of liquid, all of which are desirable features, are brought about by the present invention without having the vapors bubble up through pools of liquid.

It is to be noted that there may be any number of decks or plates 11 and 20 properly spaced throughout the height of the tower. The number of vapor risers 13 and caps 16 in each deck 11 will vary with the size and capacity of the tower and also will depend on whether a high or low vapor velocity is desired therein. The number and size of overflow pipes 18 may of course, vary.

It is to be noted that the vapors are permitted to have a free upward passage through the risers while the over-flow liquid is caused to have a free downward passage through the over-flow down pipes 18. This free passage of vapors and liquid is brought about without sacrifice of the desired intimate contact between the vapors and liquid which is brought about when the vapors pass through the orifices 17 and through films of liquid which are flowing downward along the wall of the flange 15. The vapors will also have contact with the liquid flowing in film form downwardly on the roof 16, and in addition to this, contact will be effected in the space between the upper surface of the deck 11 and the lower surface of the deck 20. The erforated plate 20 ma if desired, take the orm of a screen provi ed with the imperforate portions 19. The amount and character of cooling liquid introduced through the line 7, will of course, depend upon the conditions of operation, as is well known to those versed in this art. The liquid which remains uncondensed, and which collects in the bottom of the shell 1, may be withdrawn through the line 9, and may be returned for retreatment, if desired, in either the same or a separate process.

I claim as my invention:

A dephlegmator comprising in combination a shell having vapor and liquid inlets and outlets, spaced superimposed imperforate decks mounted within said shell, perforate decks mounted therebetween, relatively short upstanding open end risers projecting above the general plane of each of said first mentioned decks, a cap mounted above each riser, each cap comprising a flange having perforations above the upper end of the associated riser and a top wall, and a liquid overflow pipe projecting above and below each of said first mentioned decks, and imperforate depressions in each perforate deck in which the overflowing liquid collects, said imperforate 1 depressions forming a liquid seal.

In testimony whereof I aflix my signature.

JACQUE o. MORRELL.

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