Process and device for fluidized bed spray granulation

Abstract

Granule production is based on particle growth in a fluidized bed (4), in which the liquid starting product is sprayed into the fluidized bed and the finished granular particle is discharged from the fluidized bed (4) with classification. The classification is carried out with the aid of a classifying air flow which is divided into individual single flows (6) to each of which is assigned a zigzag classifier module (7, 17) and a spray nozzle (5) or a group of spray nozzles. The course of the classifying process is such that the granular particles which are too small and have not yet reached the desired diameter are thrown back into the fluidized bed (4) by a return shaft (9, 18) seated on each of the zigzag classifier modules (7, 17) in parallel or radial zones without cross-mixing, in which the relatively small particles impinge at a relatively large distance from the return shaft (9, 18) and the large particles, which have already grown close to the discharge size, impinge at a relatively small distance. The process is carried out with the aid of a fluidized bed granulator, to the inlet plate (2) of which is connected a zigzag classifier, subdivided in a modular manner, in which each zigzag classifier module (7, 17) is provided with a return shaft (9, 18) at the point where it joins the inlet plate (2, 16). In addition, at least one spray nozzle (5) at the inlet plate (2, 16) is allocated to each zigzag classifier module (7, 17).