Applied Rule-Based Control of CAN/NPK Granulation

Keywords: Fertiliser granulation, Spherodiser, Fuzzy logic, Granulation control.

The granulation process in the fertiliser industry, in the case of Kemira Denmark a spherodiser, is very operator-dependent in terms of both quality and yield.

The use of Fuzzy logic, which is based on the concept of modelling the operator, is an obvious application for the spherodiser process.

A Fuzzy controller has been developed in close collaboration between PRO-COS A/S and Kemira Denmark A/S.

This paper describes how the rules for the rule-based model are obtained from the operators and the detailed structure and philosophy behind the rule-based model.

The very critical task of implementing and commissioning the Fuzzy controller in the plant, without any organisational and justifying problems, forms the leitmotif of several chapters in this paper. We believe it is the main obstacle when adding the extra level of process control – Fuzzy logic actually is – onto an existing process control system.

The Fuzzy controller concept has after seven months reached a high level of robustness and acceptance among the operators which makes it possible to have an on-line time of the Fuzzy controller close to 90%.

The Fuzzy controller has today the capability to handle major disturbances in the process far beyond the project objectives.

A K Sorth, P B Olsen, F Larsen and N K Larse, Kemira, Denmark.

32 pages, 19 figures.