US3403785A

US3403785A - Centrifugal drier

Info

Publication number: US3403785A
Application number: US676658A
Authority: US
Inventors: Mercier Andre
Original assignee: Fives Lille Cail
Current assignee: Fives Lille Cail
Priority date: 1965-05-18
Filing date: 1967-10-19
Publication date: 1968-10-01
Anticipated expiration: 1985-10-01
Also published as: GB1094675A; ES326567A1; FR1444790A; CH445385A

Description

Oct. l, 1968 "A, MERCIER v 3,403,785

CENTRIYUCAL DRIER Original Filed May 17, 1966 AGENT Unted States Patent O 3,403,785 Y CENTRIFUGAL DRIER Andr Mercier, La Madeleine, Nord, France, asslgnor to Societe Fives Lille-Cail, Paris, France Continuation of application Ser. No. 550,703, May 12, 1966. This application Oct. 19, 1967, Ser. No. 676,658 Claims priority, application France, May 18, 1965, 17,397 7 Claims. (Cl. 210-178) ABSTRACT F THE DISCLOSURE The conical basket of a centrifugal drier is equipped with a supply tube for the material to be formed whose outlet opening is axially centered and spaced from the closed bottom end of the basket. A guide member partly projects coaxially from the outlet opening toward the basket bottom and is covered with a liquid film during drier operation so that viscous material discharged from the supply tube is precisely guided toward the center of the basket bottom while separated from the guide member by the liquid film which prevents sticking.

This case is a continuation of my prior copending application Ser. No. 550,703, tiled May 17, 1966, and now abandoned.

The present invention relates to centrifugal driers.

In particular, the present invention relates to centrifugal driers which are adapted to operate continuously and which are particularly intended to dry a product which is suspended in a liquid. Thus, a continuously operating centrifugal drier of this type will separate the liquid from the product suspended therein so that the dried product can then be collected in a condition separated from the initial mother liquor.

Although centrifugal driers of this general type are well known, particular problems are encountered when the product which is to be dried is suspended in a highly viscous fluid. It is accordingly a primary object of the present invention to provide a centrifugal drier which is capable of very effectively handling materials of this type so that, even if the product which is to be dried is suspended in a highly viscous mass, it will nevertheless be capable of being eiciently dried with the structure of the present invention.

Conventional centrifugal driers which operate continuously are provided with rotary drying baskets which taper downwardly so that they are in general of a frustoconical configuration having a relatively large open top end and a relatively small closed bottom end which is fixed to one end of a vertical rotary drive shaft. The material which is to be dried is generally supplied to the interior of the rotary drying basket through the open top thereof by way of a suitably calibrated nozzle at the end of a supply tube and situated in a position coaxial with the axis of rotation of the drying basket. With this conventional construction, the product which is to be dried simply falls by gravity to the bottom of the basket where the material is then set into rotary movement as a result of frictional engagement between the material and the rotating basket. As a result of the centrifugal force which acts on the material, this material spreads in the form of a thin layer along the frustoconical inner surface of the rotary basket, this frustoconical inner surface forming the inner limiting surface of a perforated wall of the basket which forms a sieve or strainer of any type through which the liquid can pass while the product initially suspended in the liquid is retained by this perforated basket wall. The actual drying takes place as a result of the centrifugal force acting on the material at the perforated side wall of the rotary basket. Thus, the liquid portion of the initially introduced 3,403,785 Patented Oct. l, 1968 ICC material filters through the sieve formed by the frustoconical side wall of the rotary basket, and the product retained by this side wall continues to slide upwardly along the latter, slipping along the inner surface of the sieve until this product is finally ejected at an upper portion of the basket.

As has been indicated above, driers of this general type cannot be used in those cases where the viscosity of the mother liquor is too great. In the case where the materials introduced into the drier are in a highly viscous form, these materials are in fact in an intermediate state between the liquid and the solid states. As a result, the material has a far greater than negligible resistance to shear and tension. Therefore, when material with these characteristics falls to the bottom end of the basket of the drier, the stream of this material does not distribute itself uniformly over the bottom of the drier but is instead entrained, without becoming dissociated, toward the periphery of the drier basket. The material then slides upwardly along the inner surface of the basket and is finally ejected from the top end of the basket in the form of a sausage-shaped mass without having been dried.

Thus, it is one of the objects of the present invention to provide a centrifugal drier which is particularly suited for efficiently drying highly viscous materials under conditions of the type referred to above.

In particular, it is an object of the present invention to provide a construction which will reliably direct the material which is to be dried along the axis of rotation of the drying basket so that the material will reach the central portion of the bottom of the basket to be distributed outwardly from this central portion of the bottom of the basket.

Furthermore, it is an object of the present invention to provide a construction which will reduce the extent of viscosity of materials which initially are highly viscous, So that in this way it becomes easier to dry the materials.

In addition, it is an object of the present invention to provide a structure which can accomplish these results in a drier which operates continuously.

Also, it is an object of the present invention to provide a construction of the above type which is simple and rugged and which lends itself to incorporation into existing driers. Of course, the structure of the present invention also can be incorporated into new driers.

In accordance with the present invention, there is arranged along the axis of rotation of the drier basket, at least partly in the interior thereof, an elongated guide member which extends downwardly along the interior of the basket to the region of the bottom end thereof. The supply means which is provided for supplying the material to be dried to the interior of the basket through the open top end thereof directs this material for flowing movement downwardly along the exterior surface of the guide member. A means is provided for maintaining on this exterior surface of the elongated guide member a film of liquid which thus becomes situated between the guide member and thev material to be dried so as to prevent sticking of the material to be dried onto the elongated guide member and so as to promote the efficient downward flowing of this material toward the interior bottom end of the drier basket precisely along the axis of rotation thereof.

Thus, the material which is to be dried cannot depart from the axis of the rotary drier basket and it becomes uniformly `distributed in all directions along the bottom of the basket. This distribution is enhanced by the fact that the elongated guide member around which the material is situated as it ows toward the bottom of the 'basket forms the material into a tubular stream so that the bottom end of the stream which reaches the bottom end of the basket is of an annular, ring-shaped configuration greatly enhancing the uniform outward distribution of the material along the bottom of the basket.

With the construction of the the invention, moreover, there is the advantage of bringing about dilution of the liquid phase of the material to be dried just prior to actual drying, in a manner similar to that set forth in French Patent No. 1,316,550. Thus, the film of liquid on the exterior surface of the elongated guide member can be a liquid solvent which reaches the bottom of the rotary drying basket together with the material to be dried so as to mix intimately with the material to be dried, thus diluting the liquid phase thereof, so as to facilitate the drying action.

The invention is illustrated by way of example in the accompanying drawing which forms part of this application and in which one embodiment of a construction according to the present invention is illustrated, by way of example, in a schematic sectional elevation taken in a plane which includes the axis of rotation of the drier.

The centrifugal drier shown in the drawing includes a rotory drying basket 1 which is of a generally frustoconical configuration and which has a closed bottom end fixed to the top end of a rotary drive shaft 2, which rotates at high speed. This drive shaft is supported for rotary movement by bearings carried by a supporting structure 3 which is in turn mounted on vibration damping elements 4.

The rotary drying basket 1 is situated in the interior of a housing which provides around the exterior of the basket 1, below the top end thereof, a chamber C in which the liquid phase of the material introduced into the drier is collected after this liquid phase has become separated from the product suspended initially in the liquid. Thus, the drier 1, as shown schematically in the drawing, includes an inner rotary perforated wall 19 forming a sieve and having small openings through which the liquid can flow, this inner wall being supported by an outer wall structure having larger openings and supporting the sieve 19. Communicating with the open top end of the rotary basket 1 is an outer chamber D of the drier housing, and it is in this chamber D that the dried products are collected after being ejected from the upper portion of the rotary drier basket 1.

This rotary drier basket 1 has, in the region of its botton end, inner and outer wall portions which are spaced from each other to define the annular space 18 which extends not only along the bottom of the drier basket but also part of the way upwardly along the side wall thereof. For this purpose the basket 1 has, in its lower interior portion, a bowl 14 forming the inner wall and having a lower cylindrical portion which is joined with an upper perforated frustocoriical portion 1S. The perforations of the frustoconical portion 15 of the inner wall 14 are great enough to permit passage of the largest particles suspended in the liquid of the material to be dried. Suitable spaced studs are xed to the outer bottom wall portion of the rotary basket and support the bowl 14 in spaced relation thereto, these studs being situated along the lower wall portions of the inner wall 14 and the outer wall 16 at the bottom end portion of the rotary basket 1. In this way, the outer wall 16 of the basket defines with the inner wall 14 thereof the annular space 18 which communicates with the lower horizontal space between the

walls

14 and 16 and which extends upwardly between the perforated wall portion 15 and the sieve 19 to the space which surrounds the upper lip of the inner wall 14 just above the perforated portion 15 thereof. This construction is analogous to that disclosed in French Patent No. 1,383,840.

The material which is to be dried is supplied to the interior of the rotary basket 1 through the open top end thereof by way of a supply means which includes a tube 5 communicating with an insulated control valve 6 and, when the valve 6 is opened, the material which is to be dried is directed downwardly through the supply means toward the interior of the bowl or inner wall 14 at the lower central portion of the basket 1. The outlet of the valve 6 communicates with an upper open end of an elongated supply tube 7 of the supply means, this tube 7 having an axis coincident with the axis of rotation of the basket 1. Tube 7 terminates at its bottom end in a suitably calibrated outlet opening 13 forming an outlet nozzle through which the material discharges downwardly toward the bottom end of the basket 1. l

In accordance with the present invention, there is situated along the axis of rotation of the rotary basket 1- an elongated guide member 8 which has its own axis coinciding with the axis of rotation of the basket 1 as well as with the axis of the supply tube 7. This guide member 8 extends downwardly to the region of the bottom end of the basket 1. In fact, as is indicated in the drawing, the guide member 8 terminates at its bottom end just above the bottom Wall of the inner bowl 14. ln the illustrated embodiment, the elongated guide member 8 is of a hollow tubular construction so that it can receive in its interior an elongated inner tube 9 through which a suitable heating medium is directed in a manner described below. As is apparent from the drawing, adjacent its upper end the guide member or tube 8 is connected with and supported by a horizontally and laterally extending tube which extends to an opening in the tube 7, this latter opening being closed by this lateral tube which communicates with the interior of the tube 8 and through which the tube 9 is directed into the interior of thetube 8, in the manner shown schematically in the drawing.

The tube 9 extends through a central opening' formed in the bottom wall of the bowl 125, and, as is indicated in the drawing, the tube 9 has considerable clearance while passing through this central opening which otherwise is completely empty. In other words, there are no sealing structures situated at the bottom wall of the bowl 14 surrounding the tube 9. Thus, by passing through the central opening in the bottom wall of the bowl 14, the tube 9 terminates at its bottom end in a discharge opening 17 through which it communicates with the space 18 which is defined between the outer wall 16 and the inner wall 14 of the space 18.

A means is provided for maintaining a film of liquid at the exterior surface of the guide member 8 in accordance with the present invention, and this means includes, in the illustrated embodiment, a tubular feed member 10 which surrounds and is fixed to the tube 8 within the supply tube 7, this tubular member 10 having a closed top end and having -at its bottom end a calibrated annular orifice 11 coaxially surrounding the tubular guide member S so that, through this orifice 11, a film of liquid will issue to flow downwardly along the exterior surface of the guide member 8. The interior of the tubular member 10 communicates through a conduit 12 with a suitable source of liquid from which the liquid film is formed.

During operation of the apparatus, the material to be dried, such as, for example, massecuite in a sugar refinery, is directed toward the inner bottom portion of the basket 1, into the interior of the bowl 14 through the open bottom end 13 of the supply tube 7 of the supply means. Simultaneously, a suitabie solvent is introduced from the conduit 12 into the interior of the tube 10 surrounding the elongated guide member 8. In the case of massecuite in ya sugar refinery, this solventcian simply be water. The solvent will dilute the liquid phase of the material which is to be dried. This solvent flows out of the calibrated oriice 11 at the bottom end of the tubular member 10 and flows along the exterior surface of the guide member 8 in the form of a liquid film which surrounds the guide member 8 and which separates the product which is to be dried from the exterior surface of the guide member S, so that in this way the downward flowing of the viscous material is enhanced. The tubular guide member 8 guides the stream of material which is to be dried until it reaches the region of the bottomend of the bowl 14, and the guide member 8 will maintain the stream of material coaxial with the drier axis. In this way, a uniform spreading or distribution of the material along the -bottom of the bowl 14 is assured.

The solvent which forms the film flowing along the exterior surface of the guide member 8 and the material which is to 'be dried are set into rotary movement in the interior of the bowl 14, and the mixture in the bowl 14 of the solvent and the material to be dried results in an extremely rapid dilution of the liquid phase of the material.

As a result of the centrifugal force which acts on the material to be dried, this material in diluted form is advanced upwardly toward the perforated wall portion 15 of the bowl 14. The material, in the diluted condition achieved by way of the liquid film, will pass through the openings of the wall portion 15, these openings being large enough to permit passage of the largest particles, as pointed out above. The centrifugal force which thus directs the material through the openings of the wall portion 15 provides by way of these openings a division of the material to Ibe dried. In this way, the material is divided to a fine degree and passes outwardly beyond the perforated wall portion 15 in the form of relatively fine filament-ary streams or in the form of droplets yso that, in this way, the divided material has an extremely large outer surface area exposed to the heating fluid which is introduced by way of the tube 9. This heating fluid discharges from the bottom outlet end 17 of the tube 9 to flow along the space 18 upwardly therethrough into engagement with the finely divided material which reaches the space 18 through the openings of perforated wall 15. The heating fiuid which is introduced through lthe tube 9 will generally be a vaporized form of the solvent which is used for the liquid lm flowing downwardly along the exterior `surface of the guide member 8. When this solvent in vaporized form contacts the droplets or filamentary streams issuing from the openings of the wall portion 15, the vapor condenses and heats the finely divided m-aterial.

The liquid film which flows along the exterior surface of the tube 8 together with the material to be dried form a liquid seal at the bottom end of the bowl 14 just above the central lbottom openin-g thereof through which the tube 9 extends so that, as a result of this liquid seal, no sealing structure need be provided passage around the tube 9 lwhere it passes through the central opening at the bottom wall of the bowl 14.

The material which is to be dried, in diluted and heated condition as a result of the above-discussed factors, rises upwardly along the sieve 19 which forms part of the frustoconical side wall of the rotary basket 1, and the liquid phase of this material will now filter through the sieve 19 to be collected in the chamber C. The solid phase continues .to slide upwardly along the sieve 19 and is evacuated at the upper portion of the rotary basket 1 to be received in the chamber D.

It is clear that many modifications of the above-described structure can be provided, by using suitable mechanical equivalents, without departing from the invention. The structure of the invention can of course be used with a conventional centrifugal drier of known type which operates continuously, so that a special structure for reheating the product just before the drying thereof is not required.

What is claimed is:

1. In a centrifugal drier, in combination:

(a) a drying basket having an upright axis of rotation and defining a cavity about said axis, a portion of said basket closing the bottom of said cavity;

(b) supply means communicating with said cavity for supplying a material to be dried, said supply means including (1) a supply tube having an outlet opening in said cavity spaced opposite and axially directed toward said portion for discharging said material, and

(2) a guide member having a portion projecting from said outlet opening, said portion of the guide member being elongated in an axial direction from said outlet toward a free end portion thereof adjacent said portion of the basket,

(3) said projecting portion having a surface exexposed in said cavity from said outlet to said free end portion thereof;

(c) means for maintaining a film of liquid on said surface in direct contact with the discharged material and for thereby separating said material from the guide member lby the contiguously interposed film of said liquid.

2. In a drier as set forth in claim 1, said guide member having another portion received in said supply tube.

3. In a drier as set forth in claim 1, said means for maintaining a film of liquid including a source of said liquid, a tubular feed member surrounding said other portion of said guide member, said feed member communicating with said source and defining with said guide member an annular gap for discharge of said film into said cavity.

4. In a drier as set forth in claim 3, said cavity flaring conically from said bottom, said basket, said supply tube and said feed member being coaxial, and said opening being directed toward said portion of said basket.

5. In a drier as set forth in claim 1, wall means in said basket adjacent said bottom dividing a space of annular cross-section about said axis from the remainder of said cavity, said space being upwardly open toward said remainder and said Wall means being formed with a central opening adjacent said axis and connecting said space to said remainder, and a tube for heatingfiuid axially projecting from said guide member into said central opening and having a discharge opening communicating with said space.

6. In a drier as set forth in claim S, said wall means and said tube for heating fiuid jointly defining an open annular passage connecting said space to said remainder, said passage being adapted to be sealed by the liquid of said film.

7. In a drier as set forth in claim 5, a portion of said wall means spaced from said central opening -being formed with radial perforations therethrough.

References Cited UNITED STATES PATENTS 2,165,807 7/1939 Murphree et al 210-71 X 2,411,660 11/1946 Manning 2102-216 X 2,883,054 4/1959 Sanchez 210-377 X 3,207,627 9/ 1965 Dietzel el al 210-71 X 3,226,257 12/ 1965 Steele et al. 210-369 X 3,238,063 3/1966 Steele 210-369 X FOREIGN PATENTS 1,316,550 12/ 1962 France. 1,383,840 11/ 1964 France.

14,0131 1892 Great Britain. 832,672 4/ 1960 Great Britain.

REUBEN FRIEDMAN, Primary Examiner.

J. L. DE CESARE, Assistant Examiner.