US2366513A - Method for breaking foam - Google Patents

Description

Jan.; 1945. L 7L E.GATES A `2,366,513

METHOD FOR BREAKING FOAM Filed May 20, 1941 1 INVENTOR A BY ATTORNEY 70% Patented Jan. 2, 1945 METHOD FORBREAKING FOAM Louis E. Gates, Canton, N. C., assignor to The Champion Paper and Fibre Company, Canton,

N. C., a corporation of Ohio Application May20, 1941, Serial No. 394,382`

. This invention relates to methods yand apparatus for breaking foam. It has a particular v`foam further carries most of the resins as well as other valuable chemicals, which are lost unless thefoam isbroken and converted to a liquid which can be handled in the recovery plant.

The primary object of this invention is thus the provision of an easily operatedand reliable method of converting stubborn and stable types of foam intol a liquid which can be handled conveniently.

An allied object is the provision of an apparatus for this purpose which shall be simple, effective, small in size, and convenient in handling andin operation.'

Other detailed objects of the inventionl will be apparent from the following description.

I have found that foam, even of the stable and persistent type described, can be substantially completely broken by, preferably, separating it from the parent liquid .and then subjecting itin the vform of vaA relatively small stream, projected through an otherwise substantially foam-free atmosphere, to impact against a substantially` foam-free surface and then `throwing it through an otherwise substantially foam-free atmosphere for a material distance, to allow the component` residual foam to a breaking operation like. that already described. Iy have found that by this process I-can convert foam which otherwise constitutes only a troublesomewaste product, into a. commercially foam-free liquor which' can be "conveniently handled for the recovery of valuable chemicals and by-products.

This process can, I find. be conveniently lcarried out by the use of two paddles which rotate rapidly one above the other on a substantially vertical axis in-a cylindrical housing, the inside e' claims. (or 25e-sn) -diameter of which is materially-larger than theI One or more pipes or diameter of the paddles. spouts, whose diameter is small relative to the radius of the paddles, introduce one `or, more 1 streams of the foam downwardly into the plane of rotation of the upper paddle, in a zone intermediate its axis and the circumference of its path. Just below this paddle and above the low- .er paddle is afunnel shaped member whose upper rim is spaced a small and substantially uni form distance from the inside wall of the housing. Liquid can thus run down the housing wall while any residual foam is caught by the funnel and directed into the path of the lower paddle in a zone'between its axis and the circumference of its path. The liquid resulting from the break- `ing of the foam flows from the bottom of the .W-housing into a suitable container below.

The invention will be further described with reference to the, accompanying drawing illustrating one embodiment thereof and in which:

Fig. l is a diagrammatic representation of the arrangement of a system for disposal of-foam. Fig. 2 is a cross sectional view of the foam breaking apparatus per se.

Referring to the drawing, foamy liquor, which may be black liquor from the sulphate pulping process,'is introduced into a tank III through a pipe III. From this tank thevfoam, withonly its ventrained liquid, flows out through a pipe I2 by virtue of pressure 'in tank IIl.` If this pressure is insufficient, a pump I3, advantageously a positive pressure pump such as a gear pump, may be provided in pipe4 I2. Branches I4 of pipe I2 deliver foamto the foam breaker I5, which may be driven by a belt I6 and motor I'I.A There the foam is converted tov liquidwhich flows into a tank I8 from which it may be withdrawn `through a pipe I9 under control of a valve 20,

its chemical content may be recovered.-

` The foam breaking devices themselves are shown in detail in Fig.` 2. A` cylindrical housing 2| isprovided with external'support brackets 22 and a suitably hinged cover-23. Mounted for rotation` within housing 2| is a shaft 3I carried substantially coaxially with' housing 2l by bearings 33 and 34, and carrying a pulley 35 by which Y 4it. may be driven by belt I6 and motor I'I. Within 50 housing 2l, paddles 36 and 31 are flxedly mounted on shaft 3|. The diameter of these paddles,

i. e., the diameter of their disc-shaped paths', is materially smaller than the'` internal diameter of and passed if desired to a recovery plant where -paddles advantageously have a slight pitch, as

illustrated in Fig. 2, in a direction which tends to impel the foam downward. This aids in maintaining continuity of flow through the machine and tends to prevent foam from being thrown upward into the space above the paddle where it otherwise might tend to accumulate at a location where a foam-free atmosphere is desired, and thus impair the efiiciency of the device. The foam inlet pipes I4 direct the foam downwardly through the plane of rotation of upper paddle 36. Foam inlet pipes I4 should be small in diameter relative to the radius of paddle 36, and should not be so great in number, with reference tothe rate of flow of foam through them, that paddle 36 is compelled to operate in an atmosphere of foam and thereby to largely lose its effectiveness.

distribution to the number of radial blades in paddle 36 in order that the impact load may be more perfectly balanced. The paddle 36 may advantag'eously have upwardly widened ends 33 which extend above the outlets of pipes I4 vso that any foam which may be deflected horizontally will be struck and broken before passing beyond the reach of the paddle.

Below paddle 36 is a funnel shaped member 4| mounted substantially coaxially within'housing 2| but preferably leaving a small and substantially uniform clearance 42 between its upper rim 43 and the inner surface of housing 2|. This clearance allows liquid which results from breaking of the foam, to run down the Walls of housing 2| while any residual foam is deflected into the funnel 4|. The outlet 44 of funnel 4| is disposed.

limmediately above the lower paddle 31. Advantageously a small cone 45 surrounds shaft 3| at the bottom of funnel 4| and provides an annular outlet 46 at the bottom of funnel 4|, which delivers the residual foam to paddle 31 in a, zone intermediate its axis of rotation and the circumly also has upwardly widened en ds39, which ex@ tend abone` the mouth 44 of funnel 4| (as shown by the broken lines which indicate the path of paddle 31), as and for the same reason that the ends 38 of paddle 36 extend above the outlets of pipes I4. l

The operation of the device is as follows: The

shaft 3| with paddles 36 and 31 is rotated rapidly by the motor l1. Foam, with only its entrained vThey are advantageously equal in number andv provide additional paddles, I nd that in practice the use of a second paddle 31 is justifiable as a safety measure lin case the foam is `not completely broken by the rst paddle 36,'but thaty these two stages are ordinarily ample to break the most stubborn types of foam en which I have so far used the device, so that additional stages are in general not necessary.

. It should be noted that in order to break the foam, instead of rendering it finer and more stable by the beating action, I provide that the housing is filled with air rather than foam, that exceptfor the relatively small streams of'foam, the paddles operate in a substantially foam-free atmosphere, and that furthermore the surfaces ofthe paddles and the walls of the housing are maintained substantially free from the presence of foam which would cushion the impact and hinder breaking of the foam.

In one example of successful foam breaking, a device similar to that illustrated in Fig. 2 was used. The housing 2| was about 20 inches in diameter and inches long. The paddles 36 and 31 were each composed of two diametrically opposite ,blades extending 6 inches from the center of the shaft 3|. The width of each was 2 inches at the center and 4 inches at the widened vends ference of its path. The paddle 31 advantageous-v -f liquid, is introduced in a downward direction through pipes I4 at a velocity so related tothe rate of rotation of paddles 36 and 31 that the undeflected foam does not pass through the path 4of the paddle before being struck by the next pact is thought t break most of the foam. The

resulting liquid together with any unbroken foam is thrown by centrifugal force outward, of! `of 38 'and 39. The blades were pitched at,an angle of approximately 10 degrees with the axis of .shaft 3| and were rotated at a speed of about 1150 v R. P. M. The funnel 4I was\ approximately 12 inches in height while the clearance 42 was somewhat under 1A inch.l The annular outlet 46 of g.

funnel 4| was about 6 inches inside and 8 inches outside diameter. There were twoll/z inch inlet pipes I4 set to deliver streams of. foam into the path of paddle 36 at distances of about 31/2 inches from the axis of shaft 3|.

per minute. and substantially foam-free liquid owed from the bottom of the device at aA rate A between 1 and '5 gallons per minute, depending` -tional area, of foam through an otherwise substantially foam-free atmosphere into the path of rotationof a rapidly rotating paddle at a rate to assure impact against all parts of the foam which'are undeflected in their' passage through said path, and throwing the 'broken with vthe unbroken foam by centrifugal force through a the paddles, through the air space where the com- .ponent parts are thought to separate, and against the walls Qfhouslng 2|, where most of the re'- maining foam appears to b'e broken. 'I'he liquid the walls through the narrow annular space 42` while any residual foam is caught in funnel 4| directed downward. through annular space 46into the path voi the lower paddle- 31 which v resulting from breakingof the foam runs downfunctions in the manner already described wmf reference to paddle 36. While it is possible, on the one hand, to shorten the device by omittingv Athe lower paddle 3'1,or,

material vdistance against an imperforate surface.

2. Method of breaking foam formedona solution of resinsoap, 'which comprises separating throwing it by centrifugal force Athrougha mate rial distance vagainst an imperforatel` surface,

separating the'residual foam from the liquor resulting from the breaking of a part of the foam, directing the residual foam into the path of rotation ,of-'a1 rapidly rotating paddle, and v throwing it by centrifugal force against an im,

perforate surface. v

3. Method of breaking foam which is formed on'black liquorfrom the sulphate process of pulpon the'other handto lengthen the device and 75 ing resinous woods, in order to facilitate the re- Foam was thus intro-` duced to the device at a rate of about gallons valuable by-products co'ncovery of the chemicals in the foam, which comprises separating the foam from the liquor. then` in an otherwise substantially foam-free atmosphere: subjecting the foam to impact against a substantially imperforate surface by projecting a stream f relatively small cross sectional area, of foam inv a downward direction through the path of rotation of a rapidly rotating paddle; and throwing the broken with the unbroken foam by centrifugal force through a material distance against a substantially imperforate surface. n

4. Method of breaking foam produced on black liquor from the sulphate process of pulping resinous woods by the use of a vacuum'lter.

in order to facilitate the recovery of the chemicals inthe foam. which comprises separating the foam from the liquor, then in an otherwise substantially foam-free atmosphere: subjecting the foam to impactagainst a substantially imperforate surface by projecting a stream. of relatively small cross sectional area, of the foam in -a downward direction through the pathloi' rota- A' 20 pact.

tion of a rapidly rotating paddle; throwing the broken with the unbroken foam by centrifugal force -against a substantially imperforate surface: separating the residual foam from the liquor resulting from the breaking of a part of the foam; subjecting this residual foam to impact against a substantially imperforate surface by feeding it into the path of rotation of a rapidly rotating paddle, and throwing. the broken and unbroken portions of this residual foam by centrifugal force againsta substantially imperforate LoUIs E. GATES.

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