US1804554A - Method and apparatus for fractionation of hydrocarbons - Google Patents

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May 12, 1931. c, p, U s 1,894,554

METHOD AND APPARATUS FOR FRACTIONATION OF HYDROCARBONS Filed Nov. 12, 1926 Patented May 12, 1931 UNITED. STATES PATENT orFlcE.

CARBON P. DUBBS, OF WEMZETTE, ILLINOIS, ASSIGNOR T0 OIL PRODUCTS COMPANY, OF CHICAGO, ILLINOIS, ACORPORATION OF SOUTH DAKOTA.

mnrnon AND APPARATUS ron' rnAo'TIoNArIoN or mnocnnnons Application filed November 12, 1926. Serial No. 147,890.

The present improvements relate more particularly to a, method and apparatus to be utilized with processes for treating hydrocarbons to produce therefrom commercial products of low boiling point range.

In the treatment of hydrocarbon vapors having different ranges of boiling points, and in an attempt to separate and separately collect products of certain ranges ofboiling points, it has been found that these separated products are more or less contaminated With a substantial portion of higher and lower boiling point products, which in most instances, is undesirable.

To give an example, a gasoline cut will consist of that portion of oil distilling ofi from the lowest temperature up to 437 F. This cut is condensed and separately collected. The cut taken above 437 F. is known as the kerosene out. In the ordinary apparatus the gasoline will be found to contain boiling points higher than-437 E, and the kerosene cut will be found to contain boiling points lower than 437 F. In other words, there will be some kerosene in the gasoline cut and some gasoline in the kerosene cut'. Heretoiore, these were known as crude cuts of kerosene and gasoline, and were redistilled to separately free the gasoline from thekeropene and to free the kerosene from the gasoine. In recent practice, rectifying columns have been utilized to accomplish the same purpose on the first distillation, thus avoiding redistillation of these cuts.

It is understood that the above example re lates to the treatment of crude petroleum containing these various fractions in a standard still. In continuous tube stills, the operation is somewhat different. In this case the total oil to be distilled oil", is vaporized and the mixed vapors passed through rectifying columns or dephlegmators, and the different cuts fractionally condensed therein.

As an illustration, if it is desired to distill I the gasoline and kerosene cuts from the crude oil, the crude oil is subjected to a temperature at which both of these cuts are vaporized. These vapors having a wide range of boiling points, are then passed through the rectifying columns where the portionshaving boiling points higher than kerosene are first condensed and withdrawn separately, and the remaining vapors passed to a second rectifying column in which the portions containing boiling points forming the kerosene are condensed and collected separately. The remaining vapors containing boiling points forming gasoline, are then. withdrawn, condensed and separately collected. In some cases, it is only desirable to obtain and collect gasoline, while in other cases, it is desirable to collect separately the gasoline,'kerosene, and sometimes, gas oil. The method and apparatus for fractionation hereinafter described, will be found to be suitable fpr all of the above purposes. If more than a gaso line c'ut'is desired, thenmore dephlegmating or fractionating columns may be used in proportion to the number of cuts of different boiling points desired.

It will be apparent to those skilled in the art that great savings will be made by having a rectifying column so designed as to bring about an efiicient separation of the different fractions for use with distilling and cracking processes, which will obviate the necessity of redistilling these condensed vapors. It is highly desirable to provide a rectifying column that will efliciently function to condense therein only those portions of the vapors having boiling points higher than those belonging to the gasoline fractions, while leaving the gasoline fractions in the vapor phase to be withdrawn and separately condensed.

These various objects are accomplished in the present invention by causing the vaors to ascend in a spiral path, being subected to the action of a cooling medium. The vapors which are condensed in "this ascent, together with the unvaporized portions of the cooling medium, will collect in pools extending at substantial right angles to the spiral path of the ascending vapors. These pools are formed by having the corrugations in the spiral element extending at right angles to the plane of said spiral.

As a'further feature of the present invention, the crests of the corrugations may 'trolle be perforated to permit a certain amount of surplus liquid from the pools to drop therethrough to the surface of that part of the spiral element positioned immediately therebelow, thus breaking up said surplus liquid and causing the liquid to pass therethrough at substantially right angles.

Other advantages and objects of the present invention will be hereinafter more particularly brought out.

In the drawings, Fig. 1 is a diagrammatic side elevational view in vertical section of a rectifying column.

Fig. 2 is a cross sectional view on line 2 2 of Fig. 1.

Fig. 3 is a cross sectional view taken on line 33 of Fig. 2.

Fig. 4 is an enlarged fragentary sectional view taken on line 44 of ig. 3. 7

Referring more in detail to the drawings, 1 designates the outer shell having the removable head 2. Disposed vertically in the height of the shell, are helices 3 contained in an inner shell 4. The outer edge of the helices is preferably solidly joined to the inner wall of the inner shell 4 so that no vaparent that when the head 2 is removed, the

inner shell 4 containing the helices can be readily withdrawn, as said inner shell 4 hangs freely from the top of. the outer shell 1. The numeral 7 designates the vapor inlet having throttle valve 8; 9 designates the liquid condensate draw-off pipe controlled by throttle valve 10. The numerals 11, 11 designate inlets for cooling mediums such as pressure distillate, crude oil or other liquid cooling mediums, which lines 11, 11 are .con-

'by valves 12, 12. The numeral 13 designates a vapor outlet ipe controlled by valve 14; 15 designates a 'quid level gauge and 16 the approximate liquid level line in the rectifyin column. At variousintervals throughout t e height of the helices may be,

interposed bafiles 17. As a feature of the present invention, the surface of the helices is corrugated to provide corrugations 18 extending at right angles to the plane of the spiral helices.

As a further feature of the present invention, the crests of these corrugations 18 are perferably perforated as shown at 19, for a purpose hereinafter to be explained.

T e operation of the rectifying column should beapparent from the foregoing description. The mixture of vapors entering rged into the bottom section of the helices 3. It is to be noted that the liquid level shown in the drawing at 16 is inst below this vapor inlet line, but suflicienty high so as to cause the lower portion of the helices to be submerged therein.

The object of this is to keep the portion below the helices filled with liquid, and thus prevent any va ors entering that section. It is understo of course, that the apparatus can be operated efliciently without any liquid level at all in this part of the tower, if desired. As the vapors are forced to pass upwardly in a spiral path around the helices, they are decreased in temperature, and condensation of art of the vapors continuousl takes place. %y the time those vapors whic are still uncondensed reach the top of the helices, all of the vapors havin boiling points hi her than those desired, ave been condense 7 Therefore, the vapors withdrawn from the rectifying column through the pipe 13 are of the desired low boiling point range. The condensate in the rectifying column contains more or less all that portion havin boiling points higher than those-it is desired to condense in the rectifying column, but as these condensed va rs flow back down the surface of the helices, they collect in pools behind the corru ations 18, the surplus liquid overflowing t rough the apertures 19 into the helices below, and as this liquid continues to flow down, it is progressively subjected to higher heat so that any low boiling point rtions contained therein are revaporized y the hot ascending vapors. By the time the condensate reaches the bottom of the spiral, it has been freed of substantially all those fractions having the desired low boilin point range.

The function of the baflles 1 is to direct the vapors to the outer periphery ofthe spiral.

It is to be noted that the spacing of the spiral gradually grows smaller in an upward direction for the reason that since part of the vapors are condensed as they pass upward through the spiral, the remainin volume of vapors is smaller, and to maintain the same velocity, it is necessary to decrease the space between the helices. It is of considerable advantage to have the helices 3 made of a thin metal of great heat conductivity so that the heat from the ascending vapors can be readily transmitted from one side of the spiral to the 0015 of liquid collecting on the upper side, t us promoting evaporation of the light ends of this condensate. If the oil used as charging stock contains more or less of a product having boiling points similar to' those produced by cracking, this charging stock may be fed directly into the fractionating column through either of the inlet pipes 11, but it is preferable that this charging perature of the vapors in this part of the. rectifying column before being discharged therein. The rectifying column may be maintained under atmospheric pressure, superatmospheric pressure, or under vacuum.

The rectifying column should be so designed that the velocity of the vapors through the spiral will not be suificient to pick up by entrainment any substantial portion of the condensate.

The fractionating column may be say, five feet in diameter more or less, and forty feet high more or less. The s acing at the lower part of the spiral may e say eight inches more or less, progresslvely decreasing until the spacing at the upper part of the spiral is say, five inches more or less.

The advantage of permittin pools of cooling li uid and condensate to be formed beyond t e corrugations 18 is to utilize the heat from the vapors passing under and over these pools to reboil and vaporize the lighter fractions trapped in these liquor pools;

Where the surplus liquid drops through the perforations 19, it drops at right angles to the ascending vapors.

By providing perforations 19 in the top of the corrugations 18, I overcome the objection of having the holes clogging, which is frequently the case where the holes are in the bottom of the pan, which holes become clogged with scales and the like, thus closing them. At the same time, by providing the holes in the top of the corrugations, I permit a pool of oil to collect back of each corrugation to stabilize the temperature throughout the dephlegmator, and as hereinafter explained, permit reboiling and vaporization of light fractions trapped in said liquid pools.

40 It is understood of course, that these corruations 18 can be made sufiiciently high to orm whatever size pool it is preferable.

The chargin stock treated per day may be one thousand arrels and the vapors entering the rectifying column through the pipe 7 may be at a temperature of say 830 F. more orless, while the vapors discharging through the ipe 13 may be at a temperature of say 3501 more or less, these figures of course, being merely illustrative.

I claim as myinvention:

1. An apparatus for rectifying hydrocarbon oil vapors comprising an elongated vertical shell, a vapor inlet adjacent the lower portion-of said shell a. vapor outlet adjacent the upper ortion of said shell, a continuous helical ba e within said shell, radial corrugations in said baflie, and perforations in the crests of said corru ations.

2. A method for ephlegmating hydrocarbon oil vapors which comprises causing the vapors to ascend through a fractionating zone in a continuous helical path in countercurrent heat exchan relation with a de- 66 phlegmating liquid ascending in a helical current heat exchange relation with a de-' phlegmating liquid descending in a helical path through sald fractionating zone, collecting the liquid during its helical descent through said zone in a series of,pools extending radially from the center of said zone to the periphery thereof, overflowing liquid in distributed form from the pools, into direct contact with the rising vapors therebelow, removing said liquid and condensate from the lower portion of said zone, and removing the uncondensed vapors from the upper portion of said zone.

CARBON P. DUBBS.

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