Design of Rotary Driers and their Application in the Fertiliser Industry

Keywords: Drier technology, Fertiliser granulation.

Complex chemical fertilisers are manufactured in granulation plants throughout the world. Although the process and mechanical design varies from one site to another, it is almost without exception amongst the major producers that the granulation stage involves the use of a certain amount of water. It is therefore necessary that a drying stage has to be employed to render a product of a quality which is suitable for normal handling and storage.

The various types of drying equipment available to the fertiliser producers are discussed together with some tools and advice which can aid them in making the right selection. The dominant type used in the existing industry is the cascading rotary drier and the basic principles involved in this type of operation are outlined more thoroughly with some details about differences in the mechanical design of the internal parts. The basic science behind this type of drying operation is described together with information on theoretical modelling and simulation of the process.

The drying needs of the different types of granulation processes are briefly described followed by a case study of the development of drying equipment at the Ince plant of Kemira Agro Oy. This latter study outlines the stages in the gradual improvement programme aimed at better efficiency and reliability of the three Driers in use at this location. The safety features built in to the equipment are also outlined and these serve as complementary information to the previous paper (Kiiski, 2000).

The paper concludes by examining how operation of the present-day Driers at Ince compares with theoretical principles. At first glance, the most notable feature is that the new design of lifters is contrary to what the conventional approach would suggest. However, a closer examination does give good reasons why the concept of this new design is correct.

Ian C Kemp, C.Eng., M.I.Chem.E., AEA Technology plc., Harwell, UK, and

R J Milborne, B.Sc. Tech., Kemira Agro UK Ltd, Ince, UK

27 pages, 12 figures, 8 refs.