Drying and gas or vapor contact with solids – Apparatus – With apparatus using centrifugal force
Patent
1992-12-22
1994-02-01
Bennet, Henry A.
Drying and gas or vapor contact with solids
Apparatus
With apparatus using centrifugal force
3457A, 34 57R, F26B 1710
Patent
active
052823210
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a fluidized bed apparatus for treating particulate materials, comprising same, rising from the entrance space to the fluidized bed space is oriented in a predetermined direction, especially given a twist, and plates each for spraying fluidizable substances into the gas stream.
Various embodiments of such an apparatus are known from DE 38 339 723 C1. In those cases a process gas, such as dry air is supplied to the entrance space, either centrally from below or through an immersion tube which extends from above through the fluidized bed space into the entrance space. From the entrance space the process gas flows through all the intermediate spaces defined between the baffle plates into the fluidized bed space. The intermediate spaces in which nozzles are provided have reduced flow cross sections due to these nozzles and, therefore, smaller quantities of process gas per unit time flow through these intermediate spaces than through those without nozzles. Consequently irregularities, not always desirable, may develop in a fluidized bed which is to form in the fluidized bed space. An entirely uniform fluidized bed, for instance, is desired when tablets are to be dried which have been sugar-coated with a liquid sprayed in through the nozzles. It is, therefore, the object of the invention to provide for an additional opportunity in a fluidized bed apparatus for treating particulate materials to influence the fluidized bed, above all to render it more uniform. Particulate materials to be treated in such an apparatus may consist, for example, of round or oblong tablets, pellets, and the like, in other words particles which, being bulk material, leave free interstices. The treatment, for example, may consist of applying a gastric juice resistant coat from an aqueous or organic solution, dispersion, or suspension on to such particles.
The object is met, in accordance with the invention, starting from a fluidized bed apparatus of the kind described initially, in that intermediate spaces without nozzles between baffle plates communicate with said inlet chamber, first inlet chamber and are connected to a second inlet chamber, and
In this manner the flow relationships in the intermediate spaces including nozzles between the baffle plates can be controlled independently of the flow relationships in intermediate spaces which do not include nozzles. The pressure in the second inlet chamber may be higher, the same, or lower than the pressure in the first inlet chamber.
The second inlet chamber preferably is an annular chamber which is concentric with the vessel. In this context it is convenient if passages extend substantially radially from the second inlet chamber to the intermediate spaces in which there are nozzles.
Preferably, the second inlet chamber extends all around a central pipe for the discharge of process gas which pipe begins in an upper region of the fluidized bed space and extends down and out of the vessel.
In an especially convenient embodiment of the invention, separate fans are connected upstream of each of the two inlet chambers.
Furthermore, it is convenient if a return air fan is arranged downstream of the fluidized bed space to maintain negative pressure in the fluidized bed space as compared to the surroundings of the vessel, while positive pressure prevails in the two inlet chambers.
In certain cases the fluidized bed apparatus according to the invention may be kept operating by the return air fan alone. Also in that event can the gas streams reaching the fluidized bed space from the inlet chambers be controlled independently of each other, provided throttling means of any known type are connected upstream of the inlet chambers. In general, however, the mode of operation described with two separately controllable fans disposed upstream of the inlet chambers is preferred.
An embodiment of the invention will be described in greater detail below, with reference to diagrammatic drawings, in which:
FIG. 1 is a vertical axial section through a vessel of the apparatus according to th
REFERENCES:
patent: 4530169 (1985-07-01), Okawara
patent: 4970804 (1990-11-01), Huttlin
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