US2197539A - Degassing apparatus - Google Patents

Description

Patented Apr. 16, 1940 PATENT OFFICE DEGASSING APPARATUS Kenneth C. DJlickman, Rochester, N. Y., assignor, by mesne assignments, to Distillation Prod-' ncts, Inc., Rochester, N. Y., a corporation of t Delaware Application December 1, 1937, Serial No. 177,552

1 Claim.

This invention relates to improved apparatus for degassing organic liquids and particularly to an improved method and means for thoroughly degassing an organic liquid which is to be subjected to high vacuum distillation.

The usual method of removing absorbed gases from liquids involves vacuum treatment of relatively static films or bodies of the liquid. This procedure is ordinarily employed to remove gases from an organic liquid in order to prepare it for high vacuum distillation. It was thought that if the liquid were subjected to a vacuum corresponding to that which would be used in the distillation, sufliciently complete gas removal would take place. I have found that com-' plete or substantially complete removal of absorbed gases by this method requires an inordinately long period of time. For instance, if a fish oil is exposed to a high vacuum until a pressure of .001 mm. is reached and then sealed in a closed chamber under this low pressure, it will be found that the vacuum in the cham-- her is soon destroyed by the additional gases which are more or less slowly evolved from the oil.

Organic liquids which must be distilled under high vacuum conditions are of low vapor pressure and consequently have complex molecules of high molecular weight. Such substances are easily oxidized. Other such substances because of their peculiar molecular structure; such as high degree of unsaturation are exceptionally liable to oxidation. For these reasons a method for rapid and complete degassing of such liquids to remove oxygen and other absorbed gases is necessary.

A type of centrifugal apparatus disclosed in U. S. Patent 1,667,139, has been employed to break up emulsions and suspensions such as flotation froth and ore slimes. These materials were subjected to centrifugal force and vacmine, in order to separate absorbed gases and cause rapid settling of solid components. This 7 apparatus can be employed to remove gases from organic iiquids in order to prepare them for vacuum distillation, but it is little better than the commonly used method described above. This is due to the fact that all of the degassing chambers are communicating so that the same pressure prevails throughout. It is therefore, difflcult to completely degas the liquid to progressively lower pressures.

This invention has for its object to overcome the above difflculties. Another object is to provide improved apparatus whereby organic liq- (Cl. 183-2.5j

uids can be quickly and completely degassed.

A further object is to provide an improved apparatus for degassing organic liquids which are to be subjected to high vacuum distillation. Other objects will appear hereinafter.

These and other objects are accomplished by my invention which in general comprises causing the organic liquid which is to be degassed, to pass by centrifugal force and while in attenuated form, through a series of chambers maintained at progressively lower pressures.

In the accompanying drawing I have illustrated an elevation in section of a preferred form of centrifugal degasser in which like numbers refer to like parts. Referring to the drawing reference numerals laF-Ik designate sections of a cylindrical main casing closed at the top and bottom by plates 2 and 3. The joints between these sections are rabbeted as illustrated in order to Prevent entry of gas, and may be sealed witha sealing compound. Tie bolts 4 bind the sections together as one rigid unit. Sections lb|k are each provided with a downwardly sloping conical plate 5, the central portion of which extends downward to form a bottlenecklike extension 6. ,Upon each plate 5 is, mounted a cylinder of metal gauze l which is covered at the top by a plate 8 having a central opening Q. A bafile I is mounted upon the under side of each conical plate in such a position as to be in front of the openings of each vacuum conduit ll connected to each of the sections of the main cylinder.

A shaft I2 extends the length of the casing and is mounted in housings l3 and M integral with end plates 2 and 3 respectively. The upper portion of housing l5 has a greater inside diameter thanshaft 42, providing an annular space into which a packing material I5 is placed. The upper portion of this annular space is closed by a plate and is connected atdiametrically opposite sides to conduits 2| and 22. Conduit 22 communicates with the upper portion of a reservoir 23 integral with plate 2. In reservoir 23 is a centrally mounted float 24 mounted on shaft 25 the lower portion of which serves as a needle valve to control the flow of liquid through valve seat 26 into conduit 21. I

A circular plate 2t integral with collar 29 is mounted upon shaft l2 in the area enclosed by section to. A series of substantially identical collars 3i! and plates 3! are mounted upon shaft I2 at spaced distances corresponding to the several portions enclosed by main casing sections l b-41c. Collars are provided with recessed portions 32 slightly larger in diameter than the extensions 6 of conical plates 5 and plates 3| and collars 30 are mounted upon shaft l2 in such a manner that extensions 6 of plates 5 extend into thisrecessed portion in the manner illustrated. Base plate 3 is provided with an integral reservoir 33 which communicates with the inside of the main casing by way of opening 34 and which is connected to a withdrawal conduit 35.

The apparatus. is built in sections in order to simplify construction and dismantling operations. In assembling the apparatus base section 3 is set upon a suitable support and shaft I2 is inserted in the housing H. The lowest collar 30 and plate 3| assembly is then fixed upon the shaft and the lowest conical plate 5, screen 1 and plate 8 assembly is then fixed to the walls of section Ii. Care should be taken to so 10- cate'collar that neck 6 extends well into the recess 32, but does not touch the walls thereof. A sealing compound is then applied to the rabbeted top edge of Ii and section lie is then put in place. section are then fastened in place and conical plate and screen, etc., fixed upon the walls of He. Each section is built. up in substantially the same way and finally top plate 2 is put in place and the whole assembly bound as one rigid unit by bolts 4.

In operating the apparatus conduit is connected to a closed system which may be a molecular or high vacuum still or an evacuated reservoir. Conduit 2| is connected to a supply of the oil or other liquid which" is to be degassed and con-- duits II are connected to vacuum pumps and the system evacuated. The oil fiows from conduit 2| into the annular space l5 and thence into consurface of circular plate 28. Shaft I2 is caused to rotate and oil flowing onto the plate is thrown off by centrifugal force as a thin film or curtain of droplets, in which form it is eifectively degassed. Gases removed at this stage are withdrawn through the conduit connected to section la.

The film of oil thrown from plate 28 collects upon the walls of la and flows through the screen I and along the upper surface ofplate 5 into the space between shaft l2 andbottle-neck projection 6, filling the recessed portion 32 in collar 30. The oil then overflows into the space between collar 30 and projection 6 onto the revolving plate 3| from whichit is thrown in attenuated form. Particles of oil are prevented from entering vacuum conduit II by bafile Ill. The oil fiows in the same way through each section where further gas removal takes place and finally passes through opening 34 into reservoir 33 and is withdrawn through conduit 35.

Initial degassing takes place in the top sections where relatively large volumes of gas are removed at comparatively high pressures. It is therefore, advisable to have these sections connected to. high capacity pumps. In the next sections The collar 30 and plate 3| of this.

smaller amounts of gas will be removed and 'same degree of vacuum, but pumps giving increasingly higher vacua should be connected to the lower chambers which are to be maintained under successively lower pressures.

When degassing oils for molecular or high vacuum distillation it is desirable that the internal pressure of gas absorbedin the oil be reduced to approximately, or below, the pressure I which is to be employed in the distillation. The

pumps connected to the last stages such as Ii and ih should therefore be capable of maintaining such a pressure which usually will be below ..1 mm. and preferably below .05 to .001 mm. Such a complete degassingis particularly important with oxidizable compounds such as vitamins, because if oxygen absorbed from the air remains in the oil in material amounts it will cause oxidation and destruction of the sensitive material when it is heated in the vacuum still.

It will be apparent that many changes can be made in the above described apparatus without departing from the spirit or scope of my invention.

The procedure can be employed to degas organic liquids in general and is of particular advantage for degassing low vapor pressure organic liquids such as cod-liver, halibut liver, linseed oil, hydrocarbon oils, etc., which tenaciously re-' tain absorbed gases. The invention is of particular value for degassing all substances which are to be subjected to high vacuum or molecular distillation. The rapid and complete degassing, which is possible, reduces the problem of maintaining a high vacuum in the still and greatly reduces thermal decomposition and oxidation of easily decomposabl substances such as are usually distilled under such conditions.

I claim:

Apparatus for degassing an organic liquid which comprises in combination an approximately vertical, cylindrical casing, a plurality of spaced conical partitions mounted upon the inside wall of the casing, whereby the casing is divided into a plurality of separate chambers. a vertical rotatable shaft passing through the center of the partions and extending the length of the casing, a plurality of horizontal discs, fixed upon the shaft, each disc being located in a different chamber formed by the said partitions and in spaced relation thereto, sealing means between each partion and the shaft whereby liquid can flow from the upper surface of each partition and thence directly onto the upper surface of the next lowest disc, a conduit directly connected to the space between each pair of partitions whereby the space between each pair 'of partitions can be highly evacuated, a conduit for conveying liquid onto the surface of the top disc and a conduit for withdrawing liquid from the bottom of the casing.

, KENNETH C. D. HICKMAN.

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