Drying and gas or vapor contact with solids – Apparatus – With apparatus using centrifugal force
Patent
1984-05-18
1986-05-13
Makay, Albert J.
Drying and gas or vapor contact with solids
Apparatus
With apparatus using centrifugal force
34 57A, 34 57E, 366101, F26B 1700
Patent
active
045877440
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a fluidized bed apparatus for mixing, drying, granulating, pelleting, polishing and/or coating pulverous or granular material, comprising a container which is at least apparoximately rotationally symmetrical with respect to an at least approximately vertical container axis, connectable to a gas source, plunger pipe in upward direction so as to move the material in the container, in particular to fluidize it, all around the plunger pipe in an upper area of the container to deflect the material entrained upwardly by the gas in outward direction,
In a known fluidized bed apparatus of this kind (DE-PS No. 872 928) the deflector shield is embodied by a circular, substantially flat baffle plate, the outer edge of which is bent obliquely in a downward direction and positioned close to the wall of the container in such manner that an annular gap is formed between the two. The material entrained by the gas in upward direction around the plunger pipe is distributed by the deflector shield from the center toward all sides like a fountain so that it will settle again in the container without requiring any special space for a bulk material cone forming. The gas flows upwardly around the outer edge of the deflector shield and through the annular gap into the suction nozzle of a blower by which it is again pressed into the container through the plunger pipe.
This known deflector shield is hardly suited to provide the desired uniform settling of the material. Still less is it possible to obtain thorough and yet gentle circulation of the material. If at all, it is obtainable only with exceptionally easily movable material. If vigorous gas flow is produced to convey specifically heavy material upwardly along the outside wall of the plunger pipe, the material will hit the deflector shield at considerable energy and thus may be altered undesirably. A strong gas flow is developed in the annular gap between the outer edge of the deflector shield and the container wall and it may entrain quite considerably quantities of smaller particles of the material. If one attempts to avoid the undesired effects of a strong gas flow by letting the gas flow more slowly, then very soon a status will be established at which it will no longer be possible to convey sufficient quantities of material in upward direction, particularly material which is difficult to treat to that uniform and quick treatment of the material no longer is obtainable.
It is, therefore, the object of the invention to develop a fluidized bed apparatus of the kind specified such that gentle and, at the same time, quick and uniform treatment of the most varied kinds of pulverous or granular material will be possible.
This object is met, in accordance with the invention, in that the deflector shield is permeable to gas at least in individual areas.
In this manner the gas flow which has conveyed the material upwardly along the plunger pipe will separate gradually from the material since the gas can flow upwardly through the permeable areas of the deflector shield, rather than being forced to flow as far as into the vicinity of the outer container wall and then pass upwardly at rather high velocity through an annular gap. The areas of the deflector shield which are permeable to gas may be so designed and arranged that gas will pass through them at moderate velocity while the material is being held back, without being damaged, by the deflector shield.
The gas-permeable areas of the deflector shield in accordance with the invention permit the design of preferred embodiments with which the deflector shield extends radially outwardly to an upper container edge.
In such embodiments, preferably the deflector shield forms a vault having a circular apex whose apex diameter corresponds at least approximately to the mean value of the diameters of the plunger pipe and the upper container edge. The result of this design of the deflector shield is that the material carried upwardly by the gas flow along the plunger pipe will be directed gently outwardly and finally
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Makay Albert J.
Westphal David W.
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