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

THERMAL PROCESSING OF ANIMAL FEED PRODUCTS IN THE FORBERG HEAT TREATMENT SYSTEM Ola Jonassen1 and Trond Muri2 1. SINTEF Energy Research, Refrigeration and Air Conditioning, Kolbj rn Heies vei 1D, N-7465 Trondheim, Norway, E-mail: Ola.Jonassen@energy.sintef.no 2. Forberg AS, Hegdal, N-3261 Larvik, Norway, E-mail: Trond.Muri@forberg.no Keywords: feed, heat treatment, steam, granulate ABSTRACT Manufacturers of animal feed must provide products guaranteed free of salmonella bacteria's. This can be achieved by heating the product to 90°C. A new and efficient thermal process has been developed at Forberg AS for this purpose. It is a batchwise operation. Two Forberg mixers/dryers are used. Steam is injected into the product in the first mixer until a product temperature of 90°C is attained. After a predetermined retention time, the product is discharged directly into the second mixer/dryer for dewatering to the initial water content and cooling to initial temperature. A program was developed for first blowing hot air through the product a given length of time for drying followed by a cold air stream for a given time for cooling and final drying of the product. The total processing time for drying and cooling was not to exceed 9 minutes. The temperatures of heated and cooled air and the lengths of time periods used for each level of temperature were determined within the project as well as the air throughflow. An optimal combination was found that enables drying and cooling within 9 minutes. The flow of product and its interaction with process air was found to be efficient for the purposes in this process. The airflow through the Forberg mixers enables rates of product and air contact in the order of magnitude of a fluidized bed. The actions of the specially designed paddles were found to prevent dead zones and isothermal conditions were obtained within the mixers.

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