Contact-sorption spray drying

Figure 12.16 Contact-sorption spray drying of lysine 1—wheat bran tank 2— pneumatic duct 3—spray dryer 4—sorbent feed 5—atomizer 6—lysine tank 7— cyclone 8—activator 9—blender. (From Tutova and Kuts, 1987.)...

Figure 12.14 presents a schematic of the spray-drying system for con-tact-sorption drying of bacterial preparations, while the design of a three-stream nozzle used to disperse solid sorbent within the spray of these preparations is shown in Figure 12.15. Performance data of this nozzle are given in Table 12.2, and characteristics of contact-sorption drying for selected bacterial cultures are specified in Table 12.3.

In the experiments conducted with additives the amount of additive was kept around 10 % of the solid material. From the point of view of solid waste disposal and possible utilization of this product, the CaS03/CaS04 ratio plays an important role. In general, CaS03 is not desired in the product. The contact time in the spray drier was less than one second. On the other hand, residence time in a conventional spray drier is between 5 and 12 seconds. Results of this work showed that over 70% SO2 removal could be achieved in such a short contact time. This indicates that most of the sorption reaction takes place in a small region around the nozzle. Reaction between SO2 and droplets takes place with a simultaneous evaporation. After the drying is completed the reaction probably continues, but at a relatively slower rate in the presence of moisture. If the relative humidity is not sufficiently high, no ftirther sorption of SO2 can be expected after completion of the evaporation step. 

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