GB2069863A - Fluidized bed apparatus - Google Patents

Abstract

In a fluidized bed vessel (92, 94) of a fluidized bed apparatus, a substantially horizontal rotor disc (78) is disposed above an air chamber (12). The rotor disc (78) is adapted for being driven in rotation about an at least approximately vertical axis and for adjustment along said axis. The fluidized bed vessel (92, 94) is conical in its lower part (92) surrounding the rotor disc (78) and has at that location an upwardly widening annular seat (88) for the rotor disc (78), said rotor disc (78) abutting aginst the seat (88) in the lower end position of its axial adjustment in the manner of a valve body, closing the air chamber (12) toward the top. Rotor disc (78) may carry a sealing ledge (84%). Alternatively, 92 may taper downwardly and 78 abuts against 88 in the upper end position of its axial adjustment. <IMAGE>

Description

SPECIFICATION Fluidized bed apparatus The present invention relates to a fluidized bed apparatus, comprising a fluidized bed vessel in which a substantially horizontal rotor disc is disposed above an air chamber so as to be driven in rotation about an at least approximately vertical axis and for adjustment along said axis.

Afluidized bed apparatus of this kind with a fluidized bed vessel which is conical in its lower part surrounding the rotor disc is known from GB-PS 2 003 396A.

The adjustability in height of the rotor disc in the known apparatus provides the opportunity to adapt the flow conditions in the fluidized bed vessel in simple manner to various granulating materials and the resulting different operating conditions, regardless of the quantity of circulating air. In the embodiments of said laid open print the fluidized bed vessel is separated from the air chamber by a perforated bottom which prevents material to be granulated or already granulated from falling out of the fluidized bed vessel into the air chamber, irrespective of the position in height of the rotor disc, when the air or other gas stream from the air chamber into the fluidized bed vessel to produce the fluidized bed therein is interrupted, as may become necessary, for instance, for cleaning exhaust air filters disposed above the fluidized bed vessel.Yet the perforated bottom, on the one hand, makes it difficult to clean the entire fluidized bed apparatus, as frequently required above all in pharmaceutical enterprises, all the more so as the space between the rotor disc and the perforated bottom is not readily accessible.

Besides, granulating materials may collect in the space between the rotor disc and the perforated bottom during interruptions of operation for the purpose of cleaning the filters, and they may cause uncontrollable flow conditions when the fluidized bed is set into motion again. They may even stick to the walls of the fluidized bed vessel so as to disturb the adjustability in height of the rotor disc.

It is, therefore, the object of the instant invention to develop a fluidized bed apparatus of the kind defined initially such that it will be easier to make it ready for operation again after shutdown.

This object is met, in accordance with the invention, in that an annular seat for the rotor disc is formed in the area of the lower end of the fluidized bed vessel, said rotor disc abutting against the seat in the one end position of its axial adjustment in the manner of a valve body, closing the air chamber toward the top.

Thus it was possible, when the drive of the rotor disc is switched off, to close the fluidized bed vessel absolutely tightly toward the bottom, either for filling fluidized bed vessel or for short interruptions of operation to clean filters, for instance, by vibration or for emptying the fluidized bed vessel upon completion of a granulating process. Positive pressure can be produced in the air chamber before an annular gap is opened once more between the seat and the rotor disc upon renewed start-up of the apparatus.

Thus it can be prevented positively at any operational condition that granulating material or the finished granules will fall from the fluidized bed vessel into the air chamber.

In a particularly advantageous embodiment of the invention the annular seat widens upwardly and the rotor disc, in its lower end position, abuts against the seat. The rotor disc may comprise a seal secured to the edge of the disc. In the embodiment having an upwardly widening valve seat, the seal is preferably a sealing ledge forming an upwardly opening flap valve.

Embodiments of the invention will be described below with reference to the accompanying drawings, in which: Fig. 1 is a vertical axial sectional elevation of a fluidized bed apparatus with a fluidized bed vessel which narrows frustoconically in its lower portion and widens frustoconically in its upper portion, and Fig. 2 is also a vertical axial sectional elevation of a fluidized bed apparatus with a fluidized bed vessel which widens frustoconically upwardly in its lower portion and narrows frustoconically in its upper portion.

Both fluidized bed apparatus shown include an air chamber 12 which is enclosed by a cylindrical wall 14 according to fig. 1 and by a conically upwardly flaring wall 14' according to fig. 2.

Three radial arms 16 carrying a bearing casing 18 are fixed at angular spacings of 120"two the wall 14, 14'. A sleeve 22 is supported for rotation, yet axially fixed by two roller bearings 20 in the bearing casing 18. According to fig. 1 a sprocket wheel 24 is attached to the sleeve 22, whereas it is a bevel gear 24' according to fig. 2. The sprocket wheel is adapted to be driven by way of a chain 26, preferably at infinitely variable speed, from an electric motor (not shown) secured to the wall 14. In corresponding manner the bevel gear 24' is adapted to be driven by a bevel pinion 28 and a shaft 32 supported in roller bearings 30 and arranged radially with respect to the wall 14', from an electric motor likewise not shown in fig. 2.

With both embodiments according to figs. 1 and 2 a rotor shaft 34 is guided for axial displacement, i.e.

in vertical direction in the sleeve 22. A key 35 disposed as torque transmitting element between the sleeve 22 and the rotor shaft 34 warrants that the two can only rotate together. The lower end of the rotor shaft 34 is supported in another axially loadable roller bearing or roller bearing pair 36 in a casing 38 which is supported by an affixed horizontal plate 40 on the circumferential surface of an eccentric disc 42 secured by a clamping sleeve 44 on a horizontal adjuster shaft 46. A pair of pins 48 are secured to the plate 40 so as to straddle the shaft 46 like a fork, whereby plate 40 and casing 38 are prevented from rotating together with the rotor shaft 34. The horizontal adjuster shaft 46 in turn is held axially fixed in bearing bushings 50 and 52 fixed to wall 14 or 14', respectively, diametrically opposite to each other.

The fluidized bed apparatus according to fig. 1 is so designed that the adjuster shaft 46 is rotatable by an adjuster clamp handle 54 which is axially displaceably arranged at one end of the shaft projecting out of the bearing bushing 52 and supported on the outer end face of the bearing bushing 52 through the intermission of a friction disc 56. A tensioning clamp handle 58 is provided to clamp the adjuster shaft 46 in a selected angle of rotation position. There is a threaded connection between the tensioning clamp handle 58 and one end of the adjuster shaft, and the tensioning clamp handle 58 is supported at the end face of the adjuster clamp handle 54 remote from the first friction disc 56, through the intermission of a second friction disc 60.By rotating and subsequently clamp ing the adjuster shaft 46 the rotor shaft 34 can be adjusted in vertical direction and then kept at the desired level.

A similar effect can be achieved with the fluidized bed apparatus according to fig. 2 in that a gear 62 is secured on the adjuster shaft 46 and meshes with a pinion 64 on a countershaft 66 which in turn is supported in a bushing 68 fixed to the wall 14'. A handwheel 70 is connected with the countershaft 66 for common rotation. The countershaft 66 can be clamped in a selected angle of rotation position by means of a nut72 threaded on the shaft and supported on the handwheei 70 through the intermission of cup springs 74. In this mannerthe rotor shaft 34 may be retained in a selected elevation with the fluidized bed apparatus according to fig. 2 as well.

With both fluidized bed apparatus according to figs. 1 and 2 threaded pin 76 is formed at the upper end of the rotor shaft 34 to receive a rotor disc 78 which is clamped tight by a nut 80. Furthermore, a cone 82 is screwed on the threaded pin 76 to press with its basis on the rotor disc 78.

According to fig. 1 an annular sealing cord 84 is fixed at the outer edge of the rotor disc 78 and embedded with approximately half its circular cross section in an annular collar86 of the rotor disc.

Instead of a sealing cord 84, a flat annular sealing ledge 84' is fixed at the outer edge of the rotor disc 78, for instance, by gluing, according to fig. 2.

In both embodiments according to figs. 1 and 2 an annular seat 88 is provided around the rotor disc 78.

According to fig. 1 it is formed at an independent, axially symmetrical structural element 90, screw connected with the wall 14, and tapers frustoconically in upward direction. According to fig. 2, on the other hand, it is formed in the wall 14' itself and widens frustoconically in upward direction.

Above the annular seat 88 both embodiments include a frustoconical lower member 92 of a fluidized bed vessel 92,94, formed integrally or connected by flanges. In the case of the embodiment according to fig. 1 this lower member tapers upwardly, while it is widened upwardly in the embodiment according to fig. 2. An upper member 94, likewise of frustoconical shape, of the fluidized bed vessel 92,94 is flanged to the lower member 92 and widens upwardly according to fig. 1, while it narrows upwardly according to fig. 2.

The fluidized bed apparatus shown in fig. 1 comprises a perforated bottom 96 below the rotor disc 78 as the upper limit of the air chamber 12 and clamped between an annular upper end face of the wall 14 and the annular structural member 90. The fluidized bed apparatus according to fig. 2 does not comprise such a perforated bottom so that the air chamber 12 can be closed at the top only by the rotor disc 78.

The rotor disc 78 is shown in fig. 1 in its upper end position in sealing engagement against seat 88 by means of its sealing cord 84. By rotating the adjuster shaft 46, the rotor disc 78 may be lowered more or less out of its upper end position until close to the perforated bottom 96 so that a more or less wide annular gap is formed between the outer edge of the rotor disc 78 and the seat 88.

The opposite happens with the fluidized bed apparatus shown in fig. 2: In its upper end position, shown in continuous lines, the rotor disc 78 leaves an annular gap 98 between itself and the lower member 92 of the fluidized bed vessel 92,94. From this upperend position the rotor disc may below- ered into a lower end position in which it is indicated in discontinuous lines at the left of fig. 2 and in which it closely abuts the seat 88 with its outer edge.

According to fig. 2 the annular sealing ledge 84' may be made of a yielding, low-friction material like polytetrafluoroethylene and so dimensioned that it will engage the lower member 92 of the fluidized bed vessel 92,94 even with the rotor disc 78 in its upper end position. Yet this engagement will be at such little pressure that the sealing ledge will act like a flap valve and permit air or other gas flow from the air chamber 12 into the fluidized bed vessel 92,94 without giving any processed material contained in the fluidized bed vessel a chance to fall into the air chamber 12. As the rotor disc 78 is lowered, the pressure increases under which the sealing ledge 84' abuts against the lower member 92 of the fluidized bed until the rotor disc 78 rests firmly on the seat 88, thus interrupting any flow from the air chamber 12 into the fluidized bed vessel 92,94.

Claims (6)

1. A fluidized bed apparatus, comprising a fluidized bed vessel in which a substantially horizontal rotor disc is disposed above an air chamber so as to be driven in rotation about an at least approximately vertical axis and for adjustment along said axis, and an annular seat formed in the area of the lower end of the fluidized bed vessel for the rotor disc, said rotor disc abutting against the seat in the one end position of its axial adjustment in the manner of a valve body, closing the air chamber toward the top.

2. Afluidized bed apparatus as claimed in Claim 1, wherein the vessel is conical in its lower part surrounding the rotor disc.

3. Afluidized bed apparatus as claimed in claim 1 or claim 2, wherein the annular seat widens toward the top and the rotor disc, in its lower end position, abuts against the seat.

4. A fluidized bed apparatus as claimed in claim 1 or claim 2, wherein the rotor disc comprises a seal secured to the edge of said disc.

5. Afluidized bed apparatus as claimed in claims 3 and 4, wherein the seal is a sealing ledge forming an upwardly opening flap valve.

6. Afluidized bed apparatus substantially as hereinbefore described with reference to the accompanying drawings.