US2153640A - Seal for centrifugal fluid treating apparatus - Google Patents

Description

April 11, 1939- w. J. PODBIELNIAK SEAL FOR CENTRIFUGAL FLUID TREATING APPARATUS 2 Sheets-Sheet 1 Filed June` 25, V1936 Y INVENTOR.

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ATTORNEY.

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w. J. PODBIELNIAK 2,153,640

SEAL FOR CENTRIFUGAL FLUID TREATING APPARATUS Filed June 25, 1956 V2 Sheets-Sheet 2 ATTORNEY.

Patented Apr. 11, 1939,

SEAL FOB CENTRIFUGAL FLUID TREATING APPARATUS Walter J. Podbielnlak, Chicago, Ill., assigner to Benjamin B. Schneider, Chicago, Ill.

Application June 25, 1938, Serial No. 87,223

12 Claims.

The present invention relates to improvements in the art of effecting counter-current exchange between fluids such as. between liquids and vapors or gases, or between liquids of different densities that are more or less completely immiscible;l

and more particularly to a liquid centrifugal seal adapted for use in centrifugal fractionating apparatus, centrifugal pumps, turbinesA and like apparatus.

Seals of the type embodying my invention may, suitably comprise anv annular chamber or recess into which a liquid is propelled by centrifugal force to form an annular body of sealing liquid. An intermediate disk or vane divides the annular chamber and its outer extremity is arranged to extend into the sealing liquid to prevent the by-pass of fluids passing through the apparatus. Either the means forming the annular chamber, or the vane can be rotated at a suiilciently high velocity (from 500 to 2000 R. P. M. or higher) to centrifugally propel the sealing liquid into the annular' chamber or recess. In my prior Patent No. 2,004,011, issued June 4, 1935, and-my prior application Serial No.

5,059, filed February 5, 1'935, now Patent No. 2,093,645, issued September 21, 1937, and Serial No. 19,327, filed May 1, 1935, now Patent No.

2,044,996 issued June 23, 1936; and in my copending application for aCentrifugal fluid treating apparatus Serial No. 87,224 tiled June 25, 1926, I have described methods and apparatus forthe counter-current treatment of fluids of different densities for reaction, gas absorption, fractional distillation or heat exchange purposes,` etc. where a more effective counter-current treatment and l more accurate fractionation or distillation may be effected. In employing the methods and apparatus therein set forth, counter-current flow Vbetween "a liquid condensate or reflux and a 'lighter iiuid or vaporv is brought about by means of centrifugal force, the reflux or heavier liquid being thereby caused to flow outwardly through a spiral passageway of increasing radius, countercurrent to an inwardly moving lighter uid or i5 vapor. Thus', a much greater eillciency in fractionation, absorption, chemical or contact action may accordingly be secured than in .apparatus of the type hitherto knowm JIn centrifugal fractionating apparatus of the type; hereinabove described'and in like apparatus,

it is essential to use a liquid seal to prevent leakage=and by-pass of the kettle vapors and reflux lp'assing through the rotor 'as the conventional Vfpaking constructions such as the stuiiing box,

`.'l'j carbon spring-held packing rings, labyrinth rings (ci. :ess-si etc. leak too readily and are not practicable for large diameters, high rubbing velocities and `vibrating Joints; and, in instances where a centrifugal pump is used, to handle hot corrosive liquids. Liquid seals of either the stationary or 5 rotating recess type work quite satisfactorily at substantially all clearances between the relatively moving parts when the seal is established by water, salt water solutions and glycerine. In such seals with a clearance between the relatively 10 moving vane and recess in the order of approximately one-eighth of an inch, a perfect seal is maintained at speeds in the order of 2000 R. P. M. and pressure differences across the seal of about 6 to 10 pounds. However, if liquids other than 15 water.' salt water solutions and glycerine are used to establish the seal, the seal will not operate at -all under the same conditions unless the clearance between the relatively moving vanes and recess is critically maintained. Thus I have found 20 that liquids both heavier and lighter than water, ranging from carbon disulphide and carbon tetrachloride to benzine and kerosene, and liquids more or less viscous ranging from lubricating oil to benzene or kerosene; and liquids even of the 25 same viscosity as water, will not operate at all to establish a seal at a clearance in the order of one-eighth of an inch, but permit fluids to rush around the seal. With liquidsl likely to be distilled other than water, salt water solutions and 30 glycerine it is not possible to maintain an unbroken liquid body between the relatively moving vane and recess as any clearance, when operating at high'speeds, at these liquids immediatelyl tear, disrupt and channel, thus permitting uid to g5 rush around the seal. I presume this is due to the fact that the velocity gradient between the relatively moving parts of the seal overcomes the surface tension of the liquid used to establish the seal. l

I have found that either the stationary or rotating recess type of seal can be designed to operate perfectly when utilizing any vaporizable liquid, as for example one likely to be distilled, to

establish the seal and maintain an unbroken liquid body between the relatively moving parts thereof at4 operating speeds. Surprisingly enough, this may be made possible by increasing the clearance between the relatively moving vane and recess of the seal sufliciently that the change ll of` velocity gradient between the relatively moving parts is low enough to maintainthe desired unbroken liquid body, and at the same time the clearance must not be so great that the moving part of the seal will not'keep the liquid seal body as v in motion. clearances between the relatively moving parts of the seal, in the order of threeeighths of an inch to five-eighths of an inch and slightly more or less will maintain a perfect seal with all vaporizable liquids at operating speeds (about 2000 R. P. M.) and with pressure differences across the seal in the order of 6 'to 15 pounds and up to pounds or more.

It is therefore within the purview of my invention to provide a liquid seal for a centrifugal fractionating apparatus, centrifugal pump. turbines and the like which will operate with all vaporizable liquids, as for instance water, salt water solutions and glycerine, as well as liquids heavier or lighter and more viscous or less viscous than Water, and also forhot corrosive liquids.

This invention possesses many other advantages which may be made more easily apparentv from a consideration of an embodiment of the invention. For this purpose there has been shown one form ofI the invention in the drawings accompanying and forming part of the present specification. This form shall now be described in detail to illustrate the general principle of the invention; but it is to be understood that this detailed description is not to be taken in a limited sense, since the scope of the invention is defined by the appended claims.

Referring to the drawings:

Figure l is a diagrammatic view, with parts in section, of an apparatus suitable for carrying the invention into effect; and

Fig. 2 is an enlarged fragmentary sectional view thereof, with parts in elevation, showing the construction of my novel liquid seal.

In order that the details of design and construction of my novel centrifugal `seal may be readily understood, it will be described in connection with the embodiment of my invention shown in Figs. 1 and 2 and a process of treating vapors wherein vapors from a vaporizing still or receptacle are charged into the apparatus and passed counterhcurrent to reflux or condensate travelling outwardly therein.

In the drawings, a rotor I0 is provided in which the fluids to be treated are brought into contact by a counter-current movement set up by centrifugal force. The rotor I0 is within a stationary housing II and is mounted for rotation on a vertical rotatable shaft I2. The power for rotating the shaft I2 is transmitted from any suitable source to the pulley I3 as by a motor and belt (not shown). The shaft I2 rotates in and is steadied by a stationary radial bearing I4. 'I'he vapors from a suitable still or kettle I5 are introduced into the apparatus through the inlet I6. The housing II is fluid-tight and is provided with an upper centrally disposed opening through which communication is established between the interior of the rotor I0 and the outlet I1 for the treated vapors in a manner to be described.

As stated above, the rotor I0 is located within the housing Il and is provided with a spiral passageway I8 of increasing radius which establishes communication between the inlet I6 and the outlet I1. The rotor I0 is in the form of a drum and is provided with circular end plates I9 and 20 between which the successive turns of the spirally wound sheet 2l are retained to form the spiral passageway I8. The edges of the spirally wound sheet 2l are forced into spiral grooves in theopposed faces of the end plates I9 and 20 to form fluid-tight joints as in my prior applications and the assembly is retained in a unitary structure as by the tightening bolts 22. 'I'he outermost turn of the spirally wound sheet 2| forms with the adjacent turn thereof, an entrance for lighter fluids to the passageway I8. The innermost turn of sheet 2i forms with its adjacent turn an exit which communicates with outlet I1 through a series of openings 23 formed in the upperpart of hub 24 of the rotor. The hub 24 is secured to the shaft I2 in any suitable manner in order to impart mutual rotation between the shaft and the hub and consequently between the shaft and the rotor. A tubular member 25 is integrally secured to the top end of hub 24 and is adapted to rotate therewith. Member 25 extends up through the central opening in the cover plate 26 of the housing II and provides a passageway for the fluid passing from the rotor to the outelt I1 as well as for the reflux passing into the rotor. It is now apparent that vapors issuing from the kettle I5 will ow through the inlet I6 into the spiral passageway I8, through the openings 23 in hub 24, through the tubular member 25 and thus through the outlet I1. From the outlet, the ytreated vapors pass to a condenser 42 for a purpose to be described.

In a distillation process, condensate or reflux is formed in the passageways of the apparatus and this reflux or added reflux or heavy fluid is made use of in a liquid centrifugal seal to prevent the escape of vapors between the housing II and the outlet I1 and to prevent the vapors from issuing from the apparatus without first being treated in the rotor.

The seal comprises an annular liquid seal chamber 21, surrounding tubular member 25, into which liquid reflux or condensate is adapted to be propelled to form an annular body of sealing liquid, and an intermediate rotating vane 28 dividing the annular chamber. The vane 28 is secured to the upper part of member 25 and rotates therewith. Upper and lower ribs or cleats 32 may suitably be formed on the vane to aid in imparting motion to the seal liquid. The rotatable vane centrifugally propels the liquid into an annular body into ther seal chamber and the outer end thereof extends into thelbody of seal liquid to keep it in motion during operation and thus prevent the by-pass of fluids passing through the apparatus.

The seal chamber 21 may suitably be formed by a saucer-shaped depression in the central portion of a casting 29, and a cover member 30 rigidly secured theretodn opposed over-lying relationship to the bottom face of the saucer-shaped depression. An adjustable boss or clearance ring 33 may be secured in any desired manner to the inner end of the saucer-shaped depression of casting 29 (Fig. 2) for a purpose to be hereinafter described. This boss' extends upwardly towards the rotating vane 28 and forms with the under face thereof a restricted clearance space. The boss surrounds the tubularV member 25 to provide an annular space which communicates with the interior of the housing. The casting 29 is rigidly secured to the plate 26 of housing I I and is provided with a conduit which is connected to outlet I1 and forms a part thereof. A cover plate 3| is removably secured to an opening in the casting 29 to permit inspection of the apparatus and the ready assembly and disassembly of the seal.

As set forth above, a liquid seal of the character described works quite satisfactorily for substantially all clearances between the vane 29 and the opposed faces of the seal chamber 21 when water, salt water solutions and glycerine are used as the seal liquid. However, if liquids other than water, salt water .solutions and glycerine are used,

as for instance liquids `adapted toA be distilled which are both heavier or lighter and more viscous or less viscous than water, then the seal will not operate to prevent the by-pass of vapors unless a minimum critical clearance between .the relatively moving parts is maintained. In vother the clearance between the rotating vane :and the 'opposed walls ofthe seal chamber ismade sumciently large so that the 4velocity gradient of 'the seal liquid between the relatively moving parte is notl great enough to cause channeling of the liquid by overcoming the surface tension thereof. I have :found that a minimum clearance I 1:5 between the vane and the opposed `faces ofseal `chamber 2l in the orderof three-eighthsof an inch and slightly more or less will 'permit the `seal to function perfectly for substantially all vaporizable liquids. However, the 'clearance bev tween the relatively moving parts cannot be so large that the rotating vane, even though ribbed, cannot keep the body of seal liquid in, motion. I have found that clearances up to ve-,eighths of an inch and slightly more will maintain the seal liquid in motion'and will function to maintain a perfect seal with all vaporizable liquids.

The following is an example of aspeciiic embodiment of an operative seal. With alseal. of the type shown in the drawings .in which the inside diameter is in the order of four inches, outside diameter in the order of nine inches and with cleats or ribs on the upper and lower side of the vane in the order of one-eighthl of an inch,

the seal will operate perfectly at a clearancein 35 theorder of ilve-eighths of an inch between the vane and the opposed faces of the seal chamber when the vane is rotated in the order of 2000 R. P. M. This seal will operate effectively with any vapcrlzable liquid likely to be distilled in the 40 chemical industry, including water and hot gasoline, and is capable of resisting pressure drops of from tn inches to flfteeninches and moreof mercury. Obviously, the ability of the seal to ,resist pressure drops is dependent upon the specinc gravity of the liquid used in theseal; the

greater the specific gravity of the liquid, the greater the centrifugal pressure at the periphery of the seal and hence, the greater the pressure drop that can be resisted.

While I have disclosed that seals with a clearl ance between the relatively moving parts in the order of three-eighths of an inch to ve-eighths.

of an inch are operative, it is obvious that these limits may be somewhat varied, depending upon the dimensions of the seal, the surface tension of the liquid used and the speed of the moving part, without destroying the operativeness of the seal.

As the kettle vapors are in communication with the seal chamber 21, there is a tendency for these vapors to diffuse and condense in the relatively cold liquid of the seal, thus contaminating the' seal liquid and eventually short circuiting to the condenser. If this be permitted,.the effectiveness of the seal -soon becomes slightly impaired due to slight leakage and the condensed fractions of the distilled vapor become contaminated. I have found that these kettle vapors can be effectively pushed back from the seal chamber by either rm continuously withdrawing a small amount of seal liquid under the full pressure of the periphery and flashing it at a point in the path of these kettle vapors; or preferably by continuously withdrawing a portion of the liquid from the seal, va- 75 porizing it and continuously introducing the-va electric Lor gas fired vaporizer. The now rvaporized liquid-is conducted through a# return 10 conduit Si and is discharged into-an annular -chamber 3l formed in the casting!! beneath the Y' -seal chamber. 'Ihe vapor is then forced into the lower portion or high pressure 'side of the seal chamber through a eway 3l at a point in- 16 side the small clearance space between the boss 33 and the vane 2l. The clearance space can be readily adjusted and it is advantageously made quite small so that a minimumamount of vapor will serve to effectively counteract the diuslon of 20 the kettle vapors into the seal chamber. Clearances in the order of one-sixteenth of an inch and even less have been foundquite effective. As' vaporized seal liquid is used to counteract theV diffusion ofthe kettlevapors, condensation of any 25 i part thereof within the seal will mix with the seal liquid and will not contaminate it. 'I'he uncondensed portion forces its way into the stationary housing Il and is returned to the kettle l5 through a trapped return pipe 39. In order to 80 prevent the withdrawal of an unnecessary quantity 'of liquid from the seal chamber, the rate of flow can be determined by a owmeter 40 inthe line 34 and controlledy by a valve 4I.

In a fractional condensation process, the cen- 85 vaporizer 35, it is obvious that the level thereof,

centrifugally considered, is further removed from the axis of rotation of the rotor than the level of the liquid above the vane. In addition, the 5 liquid on the under-side of the vane is heated by both the kettle vapors andthe vapors from the vaporizer 35 whereas the liquid on the upper side of the vane is positively cooled with added reflux to overcome the eilect of heat transfer 50 through the rotating vane and otherwise. It is thus apparent that `the desired non-equilibrium conditions are continuously maintained throughout the operation of the-device to prevent breakdown of the liquid body due to velocity gradient 55 stresses.

To accomplish this, the body of liquid above the .vane 28 is, as heretofore stated, positively cooled vane butat the same time maintains the liquid l at the desired level. It is nowobvious that the' liquid level on the lower side of the vane is a function of the liquid level above the vane and the pressure difference across the seal. As some .f condensation of the treated vapors may take place inthe chamber 45 above the seal and in the exit conduit I1, the lower walls of the chamber slope towards the axis and the condensate drains into the upper portion of the seal through openings 46 in the cover plate 34 at a point outside the reflux control 'pipe 44. This added condensate may serve to build up the body ol' liquid in the seal chamberto an excessive level. If this takes place, the added built-up pressure of the liquid above the vane urges some of the liquid through the reflux control pipe 44 against the pressure of the reflux entering the pipe until the desired level of the liquid is restored. It is thus apparent that the desired liquid level is auiomatically maintained at `all times during opera tion of the device.

The casting 29 is provided with a chamber 48 that surrounds the lower portion of the seal chamber 21 and which is filled with some suitable insulation 41 as for instance rock wool or the like to insulate the casting against the transfer of heat from the kettle vapors to the upper portion of the seal chamber.

In the operation of the apparatus and in accordance with my invention, gases or vapors or both from the kettle or still I5 enter into the housing II and pass through the spiral passageway I8 of the rotor I0. The rotor and its associated parts are rotated to develop a centrifugal force which may be approximately equal to the force of gravity or even less,`although I prefer that it be substantially in excess o f the force of gravity. In general, I have found it advisable to employ conditions of operation, rates of rotation and the like so that the centrifugal force effective in the operation is equivalent to five or more times the force of gravity. A speed of rotation of 600 to 2000 R. P. M. or higher hasbeen found suitable. 'I'he gases and vapors from the kettle are under pressure such that they pass against centrifugal force set up by rotation, through the passageway I8, counter-current to heavier fluid or reux through the openings 23 and out through the exitconduit 'I'I. The vapors then pass to the condenser 42. Some of the vapors will, in general, condense -in passageway IB to form reflux liquid, but the main supply of reflux is returned to the system as at 50 from the reflux condenser 42 and conduits 43, 4S.

The reux from the condenser`42 flows down the conduit 43 and that portion not needed by the system is drawn of! through a valve as at 5I. 'I'he remaining reflux is returned to the system through the conduit 49. 'I'hat portion of the reflux which is required to maintain the desired seal level above the vane 28 ls by-passed'through the valved line 44, the remainder continues along pipe 49 and enters the rotor as at-SII to treat the vapors. i

The reflux flows through the openings 23 and passes into the passageway I8. Reux entering and formed in the passageway Il flows outwardly therethrough in a film or'sheet against vone wall of the passageway, due to centrifugal force, counter-currently to the gases and vapors flowing inwardly therethrough. 'I'he relatively denser and heavier reflux therefore contacts and scrubs relatively lighter gases and vapors, the two streams of huid being brought together intimately at their surfaces of contact by the centrifugal force applied. The reflux liquid then discharges from the rotor Ill and collects in the bottom of housing II from which it drains back to the kettle II' through the trapped pipe 39.

To determine the differential in pressure beapplicability for use in centrifugal pumps where a stuillng box would not be practical as in the handling of hot corrosive fluids. in turbines and in like apparatus. In centrifugal pumps, due to the absenceof thermal effects no special provisions are required, such as the vaporizer, to prevent the leakage of gas through the seal liquid by diffusion, solution, etc. The same is true when the seal is used in an apparatus designed for oil absorption purposes.

While my description of a specific embodiment of my invention has been directed to a centrifugal seal of the stationary recess type, it is obvious that the seal may be made of the rotating recess type in which the vane is stationary. This type of seal operates substantially the same as regards break-down of the seal liquid due to pressure differences, velocity gradients, etc. In the rotating recessftype of seal the ribs or cleats may standpoint of assembly and disassembly and also because of rthe fact that a rotating vane is lighter and more easily balanced than a rotating recess.

I claim:

l. A centrifugal liquid seal adapted for use in combination with sealing liquids of any surface tension, for centrifugal fractional devices, centrifugal pumps, turbines, and like apparatus, comprising a seal chamber and a vane extending into the chamber between the opposed faces'thereof, said seal chamber and said vane being relatively rotatable and so constructed and arranged that the sealing liquid will be propelled by centrifugal force into the seal chamber to form an annular body of liquid into which the vane extends and said vane being spaced apart in the order of three-eighths of an inch from said opposed faces.

2. A centrifugal liquid seal adapted for use in combination with sealing liquids of any surface tension for centrifugal fractionating devices, centrifugal pumps, turbines and like apparatus, comprising a seal chamber and a vane extending into the chamber between the opposed faces thereof, said seal chamber and said vane being relatively rotatable and so constructed and arranged that the sealing liquid will be propelled by centrifugal force into the seal chamber to form an annular body of liquid into which the vane extends and said vane being spaced apart in the order of three-eighths of an inch to five-eighths of an inch from said opposed faces.

3. A centrifugal liquid seal adapted for use in three-eighths of an inch or slightly less from said opposed faces and means for maintaining the liquid on one side of the vane at a desired level.

4. A centrifugal liquid seal adapted for use in combination with sealing liquids of any surface tension, for centrifugal fractionating devices, centrifugal pumps, turbines and like apparatus, comprising a seal chamber, a vane extending into the chamber between the opposed faces thereof, said seal chamber and said vane being relatively rotatable and so constructed and arranged that .the sealing liquid will be propelled by centrifugal force into the seal chamber 'to form an annular body of liquid into which the vane extends and said vane being spaced apart in the order of three-eighths of an inch to `flve-eighths of an inch from said opposed faces and means for maintaining the liquid on one side of the vane at the desired level.

5. A centrifugal liquid seal adapted for use in combination with sealing liquids of any surface tension, for centrifugal fractionating devices, centrifugal pumps, turbines and like apparatus, comprising a stationary seal chamber and a rotatable vane extending into the chamber between the opposed faces thereof, said seal chamber andsaid vane being so constructed and arranged that the sealing liquid will be propelled by centrifugal force into the seal chamber to form an annular body of liquid into which the vane extends and said vane being spaced from 4said opposed faces in the order of of an inch to 5/8` of an inch.

6. A centrifugal liquid seal adapted for use in combination with sealing liquids of any surface tension, for centrifugal fractionating devices, centrifugal pumps, turbines and like apparatus, comprising a stationary seal chamber and a vane extending into the chamber between the opposed faces thereof, said vane being rotatable and so constructed and arranged that it will propel the sealing liquid into the seal chamber to form an annular body into which the vane extends, said vane being spaced from said opposed faces in the order of three-eighths of an inch to ve-eighths of an inch so that the velocity gradient between the relatively moving surfaces not sufficient to overcome the surface tension of the liquid.

' '7. A centrifugal liquid seal adapted for use in combination with sealing liquids of any surface tension, for centrifugal fractionating devices, centrifugal pumps, turbines and like apparatus, comprising a stationary seal chamber, a rotatable vane extending into the chamber between the opposed faces thereof, said seal `chamber and said vane being so constructed and arranged that the sealing liquid will be propelled by centrifugal -force into the seal chamber to form an annular body of liquid into which the vane extends and said vane being spaced in the order of of an 8. A centrifugal liquid seal adapted for use irll combination with sealing liquids of any surface tension, for centrifugal fractionating devices, centrifugal pumps, turbines and like apparatus, comprising a stationary seal chamber, a rotatable vane extending into the chamber between the opposed faces thereof, said seal chamber and` said vane being so constructed and arranged that the sealing liquid will be propelled by centrifugal force into the seal chamber to form an annular body of liquid into which the vane extends and said vane being spaced apart in the order of three-eighths of an inch to flve-eighths of an inch from said opposed faces so that the velocity gradient between the relatively moving surfaces is not sufficient to overcome the surface tension of the liquid and means for maintaining the liquid, on one sideof the vane, at the desired level.

9. The combination as set forth in claim 5 in which the vane is provided with cleats.

10. In a centrifugal seal of the vane and recess type having a seal liquid in the recess into which the vane extends, means to remove some of the seal liquid and means to vaporize the liquid and introduce the vapors into the entrance to the recess.

11. In a centrifugal seal of the vane and recess type having a seal liquid in the recess into which the vane extends'and in Vwhich the vane is spaced from the opposed faces of the recess in the order of three-eighths of an inch to ve-eighths of an inch, means to remove someof the seal liquid,

means to vaporize the liquid and introduce the vapors in the entrance to the recess, and means to restore the liquid removed from the recess.

12. In a centrifugal seal of the vane and recess type having a seal liquid in the recess into which the vane extends and in which one side of the seal is subjected to the pressure of untreated fluid and in which the other or low pressure side is in contact with treated fluid, means to prevent the bypass of the untreated fluid from the high pressure side to the low pressure of the seal comprising, means to remove some of the seal liquid and means to vaporize the liquid and introduce the vapors in the entrance to the recess and in the path of the untreated fluid.

Y WALTER J. PODBIELNIAK.

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