US2357670A - Shower deck - Google Patents

Description

Sept. 5, 1944. P. LAMBERT SHOWER DECK Filed June 21, 1941 ATI'OR Y Patented Sept. 5, 1944 SHOWER DECK Pierre Lambert, New Rochelle, N. Y., assignor to The Lummus Company, New York, N. Y., a corporation of Delaware Application June 21, 1941, Serial No. 399,137

3 Claims.

The present invention relates to improvements in fractionating shower decks for a distillation column and more particularly to such shower decks employed in the rectification of petroleum vapors under vacuum.

In some types of fractionating operations, it is the practice to carry out the fractionation in a column provided with a plurality of shower decks, each of which comprises an imperforate liquid collecting section, upon which the downflowing reflux liquid from the deck above is collected, and a perforated shower-forming section, which showers the reflux liquid onto the deck below.

Each deck extends partially across the column,

and the respective decks are so arranged that alternate decks overlap one another whereby the ascending vapors are forced to follow a zigzag path in their upward passage through the column. The function of the perforated section is to provide such a shower as will insure an intimate contact between the downflowing reflux liquid and the ascending vapors, which pass horizontally through the shower from each deck.

Such a shower deck is customarily provided with a weir, which separates the imperforate sectionfrom the perforated section. The liquid LII which is collected on the imperforate section builds up behind this weir, and its depth will depend on the height of the weir and on the head of reflux liquid flowing over the weir. In such operation, it will be apparent that the liquid which is collected on the deck will be held up or retained thereon in a more or less' static condition for a certain length of time before it passes over the weir.

This holdup time of the reflux liquid on a shower deck is determined by the size of he liquid pool that forms behind the weir and by the rate of flow of reflux downwardly through the column. It will thus be appreciated that, the longer the holdup time is, the longer the reflux liquid collected on a shower deck is subjected to the operating temperatures. Where the material undergoing fractionation is a petroleum oil such as a high boiling lubricating oil, this consideration becomes important inasmuch as such an oil is subject to cracking or other deterioration at the high fractionating temperatures employed. It is desirable, therefore, to reduce the holdup time to a minimum in order to avoid cracking or deterioration of the oil at high op-' erating temperatures.

Although various constructions and arrangements of shower decks and the like have .been proposed heretofore to accomplish an intimate contact between downflowing reflux liquid in shower form and rising vapors, to my knowledge none of these have contemplated reducing the holdup time of the liquid flowing across the decks by lowering of the amount of static liquid col-- lected thereon.

The principal object of this'invention isthe provision of a fractionating shower deck designed to reduce materially the holdup time of the reflux liquid collected thereon whereby the time during which the liquid is subjected to the operating temperature is reduced to a minimum.

Another object of the invention is the provision of a shower deck construction for use in the fractionation of hydrocarbon oils whereby the-quantity of reflux collected on the deck is reduced to a minimum and cracking or deterioration of the oils because of subjection to high operating temperatures can be avoided. 7

Other objects of the invention are features of construction which will manifest themselves as the description proceeds.

In accordance with the present invention, I provide an improved fractionating shower deck which is especially adapted for vacuum distillation of high boiling petroleum oils. The shower deck is so designed that the imperforate reflux collecting section thereof slopes downwardly and inwardly towards the perforated shower-forming section. liquid collected on the shower deck is reduced to a minimum, and cracking or decomposition of the oil atthe requisite high fractionating temperatures can be substantially avoided. At the same time, a complete shower of liquid across the path of the vapors is also provided.

Inthe accompanying drawing,

Fig. l is a fragmentary elevation partly in section of a column embodying one form of the improved shower deck, which section is taken on line l-I of Fig. 2;

Fig. 2 is a horizontal sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a vertical sectional view of a modified form of the fractionating shower deck showing weir means for controlling the...formation of the shower; and

Fig. 4 is a vertical sectional view of another modified form of the shower deck having means for controlling the formation of the shower.

Referring to Figs. 1 and 2 of the drawing, I have shown a column, indicated generally by the reference character I, which comprises a shell 2 and which is adapted for the rectification of high boiling petroleum vapors under vacuum.

In this manner the amount of reflux- The oil to be fractionated is vaporized in any suitable still, and the vapors are admitted to the shell 2 in any well known manner. The shell 2 is provided with a plurality ofrectifying or a contact zones, in each of which is located a fractionating shower deck 3 partially extending transversely across the shell. The fractionatin! decks 3 are alternately arranged in the shell as must first fill the space between weirs i and it before covering a further portion of perforated section 5. Thus, a complete shower is always provided. Although weirs I4 and I! are shown to havegthe same height. the height of'the weirs may be increased progressively from weir 8 to weir 9, or any other suitable arrangement may be employed.

In the modification shown in Fig. 4, the shower deck is provided with .the perforated showerforming section B sloping downwardly toward the so that a continuous countercurrent reflux action is obtained.

In accordance with my invention, the shower deck 3 comprises an inclined imperforate liquid collecting section I and a perforated showerforming section 5. The shower-forming section is provided with a large number of slits, holes, or

perforations of small diameter as shown so that,

when the reflux liquid passes therethrough, it forms a shower of fine streams. Preferably these two sections are separated by a weir 6, which provides for an even distribution of the reflux liquid as it flows onto the shower-forming section. The height of weir 6 is preferably made as small as possible so that the amount of liquid collected behind it on the imperforate section 4 may be reduced to a minimum. If desired, the upper edge of weir 6 may be serrated. An end dam or weir 9 is also provided to retain the reflux liquid on the shower-forming section 5.

The angle at which the imperforate collecting section 4 is inclined downwardly and inwardly from the column wall and the height of the weir 6 determine the amount or quantity of static liquid retained on the collecting: section of each shower deck. By designing the. shower deck 3 for the desired fractionating operation I can thus reduce the holdup time of the reflux liquid collected on the imperforate section 4 to a minimum for any particular operating conditions and can thereby avoid deterioration of the liquid material at the operating temperatures. Particularly in the distillation of high boiling petroleum oils such as lubricating oils is the duration of this holdup time an important factor inasmuch as the oils must necessarily be fractionated at high temperatures with the consequent possibility of cracking or decomposition of the oils when maintained at such temperatures for any sustained period of time.

.Where it is desired to remove a side stream from column I, weir B may be increased in height soas to form a pool ll of reflux liquid suiilcient to permit withdrawal of aside stream from. the particular deck and at the same time to provide a flow of liquid over the weir onto shower-forming section 5. A suitable draw-off I2 is provided for the withdrawal of the side stream from the collecting section-4 through the column wall.

With reference to Fig. 3, it will be noted that I have provided the shower section 5 with a plurality of weirs as at M and If. These weirs serve to-control the formation of the shower and insure that a complete shower is presented transversely across the path of flow of the vapors irrespective of the rate of reflux flow. It will be appreciated that, with this construction, when the rate of reflux flow is low, the liquid flowing over weir 6 oppositely inclined imperforate section 4. This construction also insures the presentation of a complete shower transversely across the path of vapor flow. When the rate of flow of reflux is low, the liquid flowing over weir i must, of necessity, pass through the lowermost row of holes in section 5. The holes may all be made the same size,

but it is preferable to gradually increase the diameter of the holes in accordance with the distance from. weir 8. If found desirable, the spacing between the several rows of perforations may also be varied. It will also be apparent that a minimum of liquid passing over the weir I will assure a complete shower of liquid across the column with this construction because of the slope of the perforated section whether or not Y the imperforate section is also inclined.

Although reference has been made particularly to vacuum distillation of high boiling petroleum hydrocarbons, for which operation the invention has special advantages, it will be apparent that the invention is also applicable to the distillation of other materials which are subject to decomposition under subjection to similar conditions for the particular materials.

Although the shower-forming section 5 of the shower deck of Figs. 1 and 2 is shown to be in the form of a trough attached to the lower edge' of the inclined imperforate section 4, it will be appreciated that the construction may be such that section 5 is flush with the lower edge of section 4. A similar flush construction may be used in the modified form of shower deck shown in Fig. 4.

Various modifications of the invention will suggest themselves to those skilled in the art, but it is desired that all such modifications are within the spirit of the invention as come within the scope of the appended claims.

I claim:

1. In combination with a column for contact of rising vapors with falling liquid, an upper shower deck and a lower shower deck in vertically spaced relation to each other within the column and each extending only partially across the interior of the column and comprising an imperforate liquid-collecting section constructed and arranged with the upper surface thereof downwardly inclined continuously in .vertical section and a'trough-lik shower section extending along the lower edge of said liquid-collecting section and having its bottom formed with numerous small perforations distributed therealong and thereacross, said a weir between said sections and extending upwardly from said liquid-collecting section at the lowest level of the upper surface of the latter to a level below the uppermost level oftion of the upper deck disposed to discharge liquid upon the imperforate liquid-collecting section only of the lower deck.

2. In combination with a column for contact of rising vapors with falling liquid, an upper shower deck and a lower shower deck in vertically spaced relation to each other within the column and each extending only partially across the interior of the column and comprising an imperforate liquid-collecting section constructed and arranged with the upper surface thereof downwardly inclined continuously in vertical section 3. In combination with a column for contact of rising vapors with falling liquid, an upper shower deck and a lower shower deck in vertically spaced relation to each other within the column and each extending only partially across the interior of th column and comprising an imperforate liquid-collecting section constructed and arranged with the upper surface thereof down- "wardly inclined continuously in vertical section and a trough-like shower section extending along the lower edge of said liquid-collecting section and having its bottom transversely inclined reversely to the direction of inclination of said surface of the liquid-collecting section and formed with numerous small perforations distributed therealong and thereacross, and a weir between said sections and extending upwardly from said liquid-collecting section at the lowest level of the upper surface of the latter to a level below the uppermost level of said surface and constructed and arranged for evenly distributed overflow of liquid from the liquid-collecting section to the shower section and forv retention of a relatively small volume of liquid upon the collecting section, said decks being constructed and arranged in a staggered relation to each other with the shower section of the upper deck disposed to discharge liquid upon the imperforate liquidcollecting section only of the lower deck.

in a staggered relation to each other with the shower section of the upper deck disposed to discharge liquid upon the imperiorate liquidcollecting section only of the lower deck, and a side-stream conduit connected to the liquid-collecting section oiyone of said decks and leading from a low point of the upper surface of the latter downwardly and outwardly through the wall of the column.

' PIERRE LAMBERT.

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