1st Nordic Drying Conference - NDC'01, Trondheim, Norway, June 27-29, 2001

MILL DRYING OF FISHMEAL Øistein Høstmark, Ola Flesland, Einar Nygård and Åge Oterhals SSF, Norwegian Herring Oil and Meal Industry Research Institute Kjerreidviken 16, N-5141 Fyllingsdalen, Norway Keywords: mill drying, fishmeal, particle size, quality ABSTRACT Fishmeal is traditionally dried in rotary dryers, using either indirect heated steam or air dryers. Drying of fishmeal with a mill dryer has been carried out in order to study the feasibility and potential for improving the product quality, mostly due to a substantially shorter drying time than in rotary dryers. The residence time during mill drying is less than 10 seconds compared to 15-30 minutes in a rotary air dryer. We have studied the effect of varying the inlet temperature and the rotational speed of the mill. The latter is important for the particle size and the drying kinetics. A maximum tolerable water content of different feed materials was observed for the mill dryer. The upper limit was in the range of 20% to 75% water, depending on the feed material properties. Measurements of protein quality showed no loss during the drying process. This type of dryer seems promising for improving the product quality, for both fishmeal and new product applications. The bulk density of fishmeal from the mill dryer was low compared to fishmeal dried in rotary air dryers. This can be improved by controlling the size reduction in the mill.

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