Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Fluidized bed
Reexamination Certificate
1999-04-20
2001-03-20
Beck, Shrive (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Fluidized bed
C422S146000, C422S140000, C034S585000, C034S588000
Reexamination Certificate
active
06203761
ABSTRACT:
FIELD OF THE INVENTION
1. Background of the Invention
This invention relates to a fluidized bed apparatus for the production and/or further treatment of granules comprising
a container with an entry chamber through which a gas, especially air, is designed to flow upwards and a fluidization chamber for fluidizing the material located above the entry chamber;
pivotal slats disposed between the entry chamber and the fluidization chamber and
at least one nozzle arm disposed in the container below the slats and having at least one nozzle line which carries a nozzle directed into the fluidization chamber for introducing materials to be granulated.
The fluidized bed apparatus according to the invention is also intended to be suitable in particular for coating temperature-sensitive granules, for example enzymes, by spraying on molten material.
2. Discussion of Related Art
It is known that materials to be granulated can be introduced into the fluidized bed of a fluidized bed apparatus by various nozzle arrangements through which the materials to be granulated are sprayed onto the granules. Aqueous solutions of materials to be granulated or granulation aids are normally introduced through nozzles disposed above the fluidized bed, i.e. downwards. This arrangement protects the nozzles against soiling by the granules. However, it has disadvantages where the materials to be granulated are molten because the relatively large distance from the nozzles to the fluidized bed leads to premature cooling and hence to solidification of the melt. A shorter distance for the sprayed molten material to travel can be achieved by using an upwardly directed spray arrangement in which the nozzles are located immediately beneath the fluidized bed. In this case, the melt advantageously cools and solidifies only after it has impinged on the granules.
Accordingly, the distance between the nozzle orifices and the fluidized bed should preferably be as short as possible. At the same time, however, granules should not cake on the nozzles or the nozzle lines. This requirement is satisfied if only the nozzle orifices project into the fluidized bed and the nozzle lines are disposed beneath the fluidized bed, i.e. substantially within the entry chamber.
A fluidized bed apparatus such as this corresponding to the type mentioned at the beginning is known from DE 38 39 723 C1 or EP 0 370 167 B1. This fluidized bed apparatus has an at least substantially cylindrical container and the sector-like, radially aligned, partly overlapping slats designed to pivot about their longitudinal axis cause the upwardly directed gas stream to rotate about the container axis in operation. Four nozzle arms extend radially inwards immediately beneath the slatted base. Each nozzle arm carries two nozzle lines each with one nozzle.
Eight narrow and four wide openings are present between adjacent slats in operation. In operation, the nozzle lines extend obliquely upwards in the wide openings so that only the upper part of the nozzle line projects into the fluidization chamber together with the nozzle. The remaining part of the spray arrangement, i.e. the nozzle arms and the greater part of the nozzle lines, is covered by the slats so that the granules in the fluidized bed are unable to cake on the spray arrangement.
If, at the beginning of the process, the material to be treated, for example coated, is introduced into the fluidization chamber, the slats designed to pivot about their longitudinal axis lie in their inoperative position in which they are substantially horizontal and lie sealingly one on top of the other. This prevents the material introduced from dropping through the slatted base into the entry chamber. By contrast, in the operative position, the slats extend obliquely and cause the upwardly flowing air to rotate.
In another known fluidized bed apparatus with a similar slatted base, the nozzles are fixedly arranged on the upper faces of certain slats. The nozzles are supplied with the melt through flexible lines. However, the flexibility of the nozzle lines lying within the entry chamber necessitated by the pivotability of the slats leads to the disadvantages discussed hereinafter.
In the operative state, the slats lie one on top of the other except for a gap of a few mm predetermined by spacers. During filling, air flows through the gaps, although at a lower throughput than during fluidization in order to prevent the product from dropping through the gaps. Accordingly, the air flow rate and the gap width are adapted to one another. The air flowing through the gaps during granulation causes the granules to rotate about the axis of the cylindrical container. By contrast, to empty the granules formed, the slats extend obliquely so that the product drops from the fluidization chamber through the slatted base into the entry chamber in the lower part of which the outlet is disposed.
In order in the case of the fluidized bed apparatus according to EP 0 370 167 B1 to pivot the slats from their oblique position into their horizontal position, the nozzle lines have to be turned about the longitudinal axis of the nozzle arm away from the openings between the slats before the slats are brought from their oblique position into their horizontal position. In the known fluidized bed apparatus, the necessary, structurally complex rotatability of the nozzle arm requires a flexible feed line, for example a hose, for the liquid to be sprayed.
If melts are to be sprayed, problems arise as, for example, in the case of molten nonionic surfactants. This is because the melt has to be kept at an elevated temperature throughout the line in the interests of problem-free delivery. Accordingly, heating of the feed line is generally unavoidable. On the other hand, with the feed lines lying within the entry chamber, the outside must not exceed a certain temperature in order to avoid caking of the granules and hence frequent cleaning of the apparatus. In addition to being heated, therefore, the feed line has to be externally insulated and/or cooled, at least in the vicinity of the entry chamber.
In the case of a flexible and pivotal feed line for the melt to be sprayed, these requirements lead to major design problems. If, for example, electrically heated, externally insulated hoses are used in the flexible feed line, the internal hose undergoes thermal expansion after a short period of operation, resulting in inadequate heating and insulation.
Another disadvantage of the prior art as represented by EP 0 370 167 B1 is that, when the slats are moved from their oblique to their horizontal position and vice versa, the four nozzle arms also have to be swung downwards and upwards, respectively.
DESCRIPTION OF THE INVENTION
The problem addressed by the present invention was to avoid the above-mentioned disadvantages arising out of the pivotability of the slats in a fluidized bed apparatus of the type mentioned at the beginning in a simple and economic manner.
According to the invention, the solution to this problem is characterized in that the slats have cutouts through which the nozzle lines are guided so that they extend partly into the fluidization chamber, the cutouts being sufficiently large for the pivoting movement of the slats.
The cutouts are preferably sealed off from the nozzle lines by a flexible material. However, sealing is not absolutely essential provided that an adequate flow of air from the entry chamber into the fluidized bed chamber ensures that the granules do not drop through the cutouts.
According to the invention, nozzle arms rigidly arranged in the fluidized bed apparatus with non-flexible nozzle lines may be used so that the design of the heating, thermal insulation and cooling system is no longer restricted by the need for pivotability or flexibility. The pivotability of the slats is not impeded because the cutouts provided in the slats for the nozzle lines are sufficiently large. The effective thermal insulation and cooling which is possible through the rigidity of the nozzle arm prevents the granules from caking on the nozzle lines during
Paatz Kathleen
Pichler Werner
Raehse Wilfried
Raker Hans
Beck Shrive
Henkel Kommandigesellschaft auf Aktien
Jaeschke Wayne C.
Murphy Glenn E. J.
Ohorodnik Susan
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