US3372095A

US3372095A - Separator

Info

Publication number: US3372095A
Application number: US409258A
Authority: US
Inventors: Ralph G Nester
Original assignee: Nester and Faust Manufacturing Corp
Current assignee: Nester and Faust Manufacturing Corp
Priority date: 1964-11-05
Filing date: 1964-11-05
Publication date: 1968-03-05
Anticipated expiration: 1985-03-05
Also published as: DE1542336A1; CH434204A

Description

R G. NESTER March 5, 1968 SEPARATOR Filed Nov. 5. 1964 w 6 TS w we 2 N mN 9 M w 3 F i f B m r 5 M w W M a 1 m JW W q r H 2 v 2 j e00 .szcr/o/v 6 ATT RNEY United States Patent 3,372,095 SEPARATOR Ralph G. Nester, Fairfield, Del., assignor to Nester and Faust Manufacturing Corporation, a corporation of Delaware Filed Nov. 5, 1964, Ser. No. 409,258

Claims. (Cl. 202153) ABSTRACT OF THE DISCLOSURE A rotatable shaft having an embossed surface, the raised parts being in the form of helices extending along a substantial part of the shaft is provided, which shaft is placed within a column to be used in separation of liquids, as by distillation. The dimensions of the said shaft are such that in operation contact is made between the outermost portions of the helices and the inside Walls of the column. The helices are present in the form of from about 0.5 to about 8 turns per inch. The apparatus also includes means for rotating the shaft, means for removing the material transported through the column, a means to connect the apparatus to a vacuum source and a reservoir for separated material.

This invention relates to apparatus for separating liquids. More particularly, it relates to apparatus for use in fractionating columns or a scrubbing tower and the like.

While considerable interest has been shown and much work has been done with spinning band distillation columns, the devices-which have been available heretofore have not had the efliciency desired. It is true that the prior devices had low hold-up and afforded low pressure drops. However, these advantages are outweighed by the relatively low efficiency of the columns. Some of the prior art devices contain rotating stainless steel or other metal screens which are in the form of helices or truncated cones or contain spirals that fit totally between the walls of the columns. Such devices afford good vapor/liquid contact with the wall because of the proximity of the edges of the screen or metal to the wall. However, even these devices do not have the efiiciency that is desired. The providing of a spinning band with a low pressure top, a low hold-up, and a high efliciency is a much needed advance.

Etficiency is a measure of the enrichment of one compound in the column which separates it from other different compounds. Essentially, efficiency is dependent upon the vapor/liquid contact. In other words, the more frequently the ascending vapor contacts the descending liquid the more eflicient will be the separation. In existing spinning band apparatus, liquid is free to contact and spiral up the rotating band without actually contacting the walls of the column. Consequently, rising material can advance upwardly without contacting descending liquid. It is desirable to avoid these effects.

An object of the present invention is the provision of an apparatus which affords improved gas and liquid contacts. Another purpose is the provision of an improved spinning band, fractionating column. A still further aim is the development of a spinning band column which affords low hold-up, low pressure drop, and high efiiciency. Another purpose is the provision of an annular spinning band which constricts the vapor path so that the rising vapor 3,372,095 Patented Mar. 5, 1968 must contact the walls of the column. Other objects will be apparent from the description below of this invention.

The objects of this invention are accomplished by the provision of a rod which contains on its outer surface a second rodlike element which is spirally wound around the first rod from the bottom of the first rod to its top. The length and diameter of the rod will depend upon the size of the column or tower. Since the central rod is mounted at the top to apparatus for rotating the device of this invention, the central rod will normally be the larger. T he device of this invention is a longitudinal element which has on its outermost parts a helix or a plura'lity of helices running along its length a distance that conforms to the length of the distilling column in which it is to be used. The outside diameter of the device is such that there is only a very slight, at most, annulus between the inside of the column Wall and that part of the device of this invention nearest that wall. The spirals on the device used in distillation rot-ate so that there is a downward pumping action exerted on liquid that attempts to rise in the column. Usually the devices of this apparatus will have the shape shown in the drawings to which reference is now made in further description of the invention.

In the drawings:

FIGURE 1 is a front or vertical elongation, partially in section, of a fractional distillation apparatus within the principles of this invention; and

FIGURE 2 is an enlarged cross section taken on lines 22 of FIGURE 1.

As shown in FIGURE 1, the vessel 1 has connected to it a column 2 which contains an outlet 3. Within the column is rod 4 which bears on its outer surface a spirally wound member 5'. The spiral element 5 generally runs the full length of the column. At the top of rod 4 there is a section 6 which contains no spiral element '5. This section extends through a plug 7 acting as closure for column 2. To the top section of rod 4 that extends beyond the top of the column is a motor M connected to a source of electrical power which is not shown.

The arrangement of the elements can be seen in more detail by an examination of FIGURE 2. This figure is enlarged to twice the size of the elements shown in FIG- URE 1. Also, there is shown in FIGURE 2 the clamping nuts 8 which hold the flange sections 9 and 10 together. For convenience these holding members have also been put in FIGURE 1. It is obvious that any convenient way of joining the column to the still pot may be used.

Further, it is obvious to those skilled in the art that if one is going to distill under reduced pressure he will provide his column with appropriate additional outlets for connecting the system to a source of vacuum. Also, a condensing means is usually used. For convenience reference is made to US. Patent 'No. 2,712,520 which shows a take-off means and a condensing means which may be used in conjunction with this invention. It will be appreciated that, if desired, the spiral member of this invention may extend up into and even beyond the condensing area.

In operating the device of this invention the material to be distilled is placed in vessel 1 which is then heated in any convenient fashion. While the heat in being applied, the mot-or M is turned on and the rotating of the shaft of motor M which is connected to rod 4 will cause the device of this invention to rotate. Rotation is generally in a direction that pumps liquid downwardly back into the still pot in order to keep the column from flooding during the distillation. When distillation is not the primary objective but a quick coarse removal of a liquid from a solid, which is to remain in the pot as the desired product, then the pumping action of the device may be reversed so that it helps in raising liquid into the column and out of the pot, acting as an extractor. The device has its main application, however, in distillation processes.

The rod 4 and the spiral member 5 is preferably made of a polymeric material and of those available poly (tetrafiuoroethylene) is preferred. Other materials include copolymers of tetrafiuoroethylene with monochlorofluoroethylene, hexafluoropropylene or ethylene or other fluorocarbon polymers such as poly(chlorotrifluoroethylene). Still other materials may be used such as nylon, polypropylene, polyformaldehyde, polyvinylfluoride, metals, ceramics and the like. Usually, a synthetic polymer is preferred and of the various materials which may be used poly(tetrafluoroethylene) is preferred, as stated, since it not only has great chemical inertness and stability but affords a very, very low coefficient of friction.

As the vapor ascends in the column, it is thrown out toward the inner walls of column 2 and is made to contact those walls to a greater degree than heretofore possible. The dimensions of the rotating spiral devices of this invention are such that they form a close fit under normal temperatures. Thus, when the device of this invention becomes heated, it expands resulting in even more positive contact with the walls of column 2. This results in higher efliciency. Similarly, liquid which is descending into the column is made to run down the inside walls With the result that flooding is prevented and a much greater degree of contact between the descending liquid and the rising vapor is obtained. Thus, the apparatus of this invention is much more efficient than the prior art devices.

In construction of devices of this invention the spiralled element and the outer element may be separately made and then joined together. In this instance the joint may be continuous or the spiralled element may be fixed to the central element 4 only at its ends. More frequently, the entire device is integral and will be machine cast or made on a milling machine. The central member 4 may be solid or hollow but if hollow it is preferred that it be sealed at its ends to prevent liquid from rising inside the tube. Also, a plurality of helices may be used. In such an instance the device appears woven with the helices cross- In comparisons of the devices of this invention to previous devices it has been noted that the devices of this invention afford a 50% higher efiiciency than previously reported. This is very low hold-up, being only about 0.1 cc. in a 24 inch column having an 8 mm. diameter. One of the reasons for this is that poly(tetrafluoroethylene) has a very low coefficient of friction on glass, so that a very close fit can be made resulting in a perfect wiping by the spiral of the glass. This leaves a monolayer on the inside of the column. Further, the spiral acts as a bearing throughout the full length of the column so that the spiral element can be rotated at very high speeds without friction. For example, the spinning bands of this invention have been revolved at speeds up to 5400 rpm. with attainment of all of the advantages of this invention. The higher speeds are obtained without friction, and heat on the inside of the walls due to friction does not result. Because of the high rate of downward pumping, there is no flooding and because of the chemical inertness of the spiraled element of this invention, the apparatus may be used for very long periods of time. Also, the device of this invention may be used to handle corrosive materials which could not be handled by the prior art devices.

As can be seen from the above the apparatus of this invention involves a vertically disposed column that contains centered in it a rotatable shaft made of a polymeric material. This shaft or rod has an embossed surface, the raised parts being in the form of helices extending along a substantial part of the length of the shaft. The central portion of the shaft and the raised portions are solid that is, they contain no perforations so that rising liquid or vapor cannot pass through the parts of the rotating element. The helices may be present in the form of a very few turns per inch such as /8 to /2 turn per inch or they may be present in a greater number such as from /2 to 8 turns per inch. Generally, the number of turns per inch will be about /2 to 4 turns per inch, although the number of turns will be adapted by the user to effect the separation he desires. The apparatus includes means for r0- tating the shaft, a means for removing material transported through the column, a means to hook it up to a vacuum source and a reservoir for the material to be separated.

The means to rotate the shaft may be a length of tungsten, stainless steel or similar metal wire connected through a plug to a motor at one end and connected at the other end to the rotating shaft of this invention. Such a rotating means is shown in US. 2,712,520.

In addition to the advantages discussed above the solid shaft of this invention with its helically embossed surfaces aifords advantages hithertofore not afforded. These reside in the solid nature of the rotatable element of this invention. Any material seeking to travel along the longitudinal axis of the rotating shaft will be thrown outwardly away from the shaft to a greater extent than afforded by the prior art devices, because the material cannot pass through the device and move in a straight path approximating or exactly parallel to the longitudinal axis of the said device. Thus, in distillations a greater mixing is afforded and a greater return of undesired material to the reservoir is effected.

While the invention has been disclosed herein in connection with certain embodiments and certain structural and procedural details, it is clear that changes, modifications or equivalents can be used by those skilled in the art; accordingly, such changes within the principles of this invention are intended to be included within the scope of the claims below.

I claim:

1. An apparatus for distilling liquids comprising a vertically disposed column and centered therein a rotatable imperforate cylindrical shaft of uniform diameter made of a polymeric material and having an embossed surface in the form of a continuous helix rotatable with said shaft and extending along a substantial portion of the length of said shaft, said helix comprising spirals present in a form of about 0.5 to about 8 turns per inch and said spirals spanning the space between said shaft and the inside Walls of said column.

2. Apparatus in accordance with claim 1 in which the overall diameter of said shaft and said helix has a value about equal to the inside diameter of said column.

3. Apparatus in accordance with claim 1 which includes a means to rotate said shaft.

4-. Apparatus in accordance with claim 1 which includes a reservoir for said liquid connected to and in conduit relationship with said column at its lower end.

5. Apparatus in accordance with claim 1 in which said polymeric material is a fluorocarbon resin.

6. Apparatus in accordance with claim 1 in which said polymeric material is poly(tetrafluoroethylene).

7. An apparatus for distilling liquids comprising a column adapted to be vertically disposed; centered in said column a rotatable shaft made of a polymeric material and having an embossed surface in the form of a helix extending along a substantial portion of the length of said shaft and upon rotation contacting the inside walls of said column; at upper end of said column a closure means for said column and connected therethrough a means to rotate said shaft; near said closure means a vapor outlet in said column; and at the opposite end of said column and in conduit relationship therewith a reservoir for the said liquid.

10. Apparatus in accordance with claim 7 which in- 5 eludes at the outlet end a means to connect said apparatus to a vacuum source.

References Cited UNITED STATES PATENTS 9/ 1962 Robbins 1596 Smith 202236 Hughes 15911 Schmie del 2337 Thier 1596 Watt 159-6 X Buchi et-al. 1596 WILBUR L. BASCOMB, JR., Primary Examiner.

NORMAN YUDKOFF, Examiner.

J. SOFER, Assistant Examiner.