DE2930312C2 - Sieve centrifuge - Google Patents

Description

The invention relates to a sieve centrifuge according to the preamble of claim 1.

In such a sieve centrifuge (earlier German patent application P 28 34 391.4) it was proposed that to firmly connect the hood in the form of a frustoconical collar to the inner sieve part. The washing liquid is fed via a hollow ring open on the radially inner side, which is connected to the hood is firmly connected.

Due to the high centrifugal acceleration, however, the washing liquid forms only a thin and very fast flowing film that is thinner than that also flowing over the frustoconical collar Layer of solids thrown off from the inner sieve part. The predominantly occurring in the form of strands Solid is therefore only partially wetted with washing liquid.

The invention is based on the object of thorough mixing in a sieve centrifuge of the type mentioned to further improve the solid separated in the inner sieve part with washing liquid.

This object is achieved by the features specified in the characterizing part of claim 1 solved.

All solid quantities thrown off from the inner sieve part hit the liquid film that forms on the hood, and a further improvement in the mixing effect is achieved by the fact that the solid thrown from the inner sieve part hits the liquid film with a tangential velocity component due to the speed difference between the sieve part and the hood. Due to the friction, the mixed solid is slowed down and falls at a lower tangential speed onto the bottom or the inner wall of the outer sieve part, where it is accelerated again. Significant shear forces act again between the solid and the liquid, which result in further mixing.
Apart from the formation of a thick film of washing liquid on the wall of the hood, the solid is mixed intensively with the washing liquid twice, namely when it hits the inner wall of the hood and when the already mixed solid hits the outer screen part.

Advantageous refinements are given in the subclaims.

Apart from improving the distribution effect, it can also accelerate the Hood can be counteracted by the solid material thrown off tangentially from the inner sieve part.

Embodiments of the invention are shown in the drawing and are explained in more detail below
F i g. 1 a half-section through the rotating parts of a sieve centrifuge,

2 shows a half section through a sieve centrifuge according to FIG. 1 and a pre-accelerator.

The F i g. 1 shows the rotating parts of a screen centrifuge, which consist of an inner screen part 1 and an outer screen part 2 firmly connected to it. Both screen members have a common shaft 3, which is supported via bearings in the housing of the centrifugal filter and the on ^e: ne pulley is drivable. The inner sieve part 1 consists of a sieve pocket centrifuge, in the inner area of which a filling tube 7 opens and in which perforated plates 8 are arranged for better distribution of the product over the sieve pockets. Drain pipe stubs 9 are provided to remove the filtrate separated in the sieve pockets.

The outer screen part 2 consists of a bottom part 10 and an adjoining frustoconical part Sieve casing part 11 together.

A drum-shaped hood 12 is concentrically located between the inner and outer sieve parts 1 and 2, respectively arranged, which is open to the bottom part 10 of the outer sieve part 2.

The hood 12 is freely rotatably mounted on the filling pipe 7 by means of a bearing arrangement 16. A feed pipe 17 for Washer fluid is directed in a radially inwardly open hollow ring 18 which is firmly connected to the hood and has passage openings 19 leading to the interior of the hood 12.

In the in F i g. In the embodiment shown in FIG. 2, a frustoconical pre-accelerator 20, which is provided with through openings, is also provided on the hood 12 for the product flowing in from the filling pipe 7. In operation, the product is introduced into the inner area of the sieve pocket centrifuge via the filling tube 7 and from there distributed evenly to the individual sieve pockets by means of the perforated plates 8 (Fig. 1) or the pre-accelerator 20 (Fig. 2), where the filtrate is separated and is discharged via the drain port 9. The remaining solid is thrown out of the inner sieve part 1 in the centrifugal direction and hits the liquid film of washing liquid located on the inside of the hood 12 in the tangential direction, which is supplied via the passage openings 19.
The solid impacting this liquid film with a tangential velocity component is intensively mixed. Due to the friction, it is slowed down and falls at a lower tangential speed onto the bottom part 10 or the sieve casing

part 11, where it again along with the washing liquid is accelerated. Significant shear forces arise again between the solid and the liquid cause further intimate mixing

Although the two screen parts 1 and 2 have the same speeds have, a good distribution of the solids discharged from the inner sieve part 1 is nevertheless achieved, since the difference in circumferential speed, which is responsible for distributing the product on the outer sieve part 2 is required, from the hood 12 enclosing the inner sieve part 1 is effected in such a way that that the solid is first braked on the hood 12 rotating at a lower speed and then on the outer screen part 2 is accelerated again. It can therefore be done with little structural effort achieve good mixing results.

The application of the embodiments according to FIGS. 1 and 2 are recommended when processing Products that contain sensitive components such as easily breakable crystals. With such Products can be damaged by excessive braking and re-acceleration in an undesirable manner or lead to the comminution of certain components.

To dampen excessive braking and acceleration effects, the hood 12 can rotate be moved. According to the in FIGS. 1 and 2 illustrated embodiments, the hood of the Solid, which is thrown off from the inner sieve part 1, set in rotation. For an even distribution this solid on the outer screen part 2, however, is a greater speed difference between the inner one Sieve part 1 and the hood 12 required. Characterized that in the hood 12 entered washing liquid which enters this unaccelerated, a braking effect is created at the same time. For example, for the

Tests carried out in the sugar industry show that the addition of 40 parts of washing liquid results in 60 parts of the inner sieve part 1 discharged sugar in the hood 12 sets a speed that is approximately is half the speed of the inner and outer sieve parts 1 and 2.

The braking effect can be increased by arranging a pre-accelerator 20 (FIG. 2). The hood 12 is not only braked by the washing liquid, but also by the incoming product. This arrangement will be used when the required amount of washing liquid is low is.

Also a separate, possibly adjustable drive for each individual rotor part, such as the inner one and outer screen part as well as the hood 12 is possible.

1 sheet of drawings

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Claims (4)

Patent claims: 1. Sieve centrifuge with an outer, cone-shaped upward widening sieve part, with a arranged inside the outer screen part and with an inner screen part between the inner and outer screen part concentrically arranged drum-shaped drum-shaped which can be acted upon by washing liquid Hood that engages over the inner sieve part and opens to the bottom part of the conical sieve part, characterized in that the hood (12) is the inner seventh part! (1) over its entire Discharge area covered and revolves at a lower speed than the inner screen part (1) 2. Sieve centrifuge according to claim 1, characterized in that the hood (12) is freely rotatably mounted is 3. Sieve centrifuge according to claim 2, characterized in that the hood (12) on a (fixed) Filling pipe (7) is rotatably mounted 4. Sieve centrifuge according to one of claims 1 to 3, characterized in that on the hood (12) a hollow ring (18), which is open on the radially inner side, is attached, which extends to the outer surface of the hood (12) has directed through openings (19) for the application of washing liquid.