subject: Introduction Of New Fluid Bed Dryer [print this page] It has been found, however, that in fluid bed dryer having a bed plate with perforations or openings of the gill type, the efficiency of the transporting flow components 26 is too high so that the lower layers of the fluidized product P flow towards the product outlet 17, while the upper layers of the fluidized product flow in the opposite direction towards the product inlet 16. This causes an undesired backmixing of the fluidized product P, whereby the residence time of the various particles of the fluidized product P on the bed plate can vary substantially.
the present invention provides a fluid bed dryer comprising a bed plate having a plurality of gas distributing openings defined therein, the openings of the bed plate being arranged in pairs of substantially oppositely directed openings, a depressed portion of the plate extending between the openings of each pair, and means for passing drying gas upwardly through the openings of the bed plate for fluidizing a particulate product supplied to the bed. Each depression may be shaped so that the direction, the velocity, and/or the mass flow of the gas flows directed through the pair of openings defined at opposite sides of each depression are different so as to provide a resulting combined gas flow having a fluidizing flow component extending at right angles to the upper surface of the bed plate, and a transporting flow component extending along or parallel to the upper surface of the bed plate. However, if desired, the depressions may also be shaped so that the gas flows through the oppositely directed openings provide a resulting, combined fluidizing gas flow which is directed at substantially right angles to the bed plate, and which has substantially no transporting flow component parallel to the upper surface of the bed plate.
The present invention also relates to a bed plate for a fluid bed dryer as described above, said bed plate having a plurality of gas distributing openings formed therein, and the bed plate according to the invention is characterized in that said openings are arranged in pairs of substantially oppositely directed openings, a depressed portion of the plate extending between the openings of each pair.
