Intelligent control of a rotary kiln fired with producer gas generated from biomass

During the past decade, the academic world has been extremely active in developing new algorithms and theories in the field of artificial intelligence (AI) and intelligent systems. In most cases, however, emphasis has been placed more on theoretical frameworks and mathematical bases than on what the individual AI techniques could offer and on how different techniques could be applied to solve real industrial-scale problems. The reputation of intelligent systems has consequently suffered from an inability to transfer new and sophisticated techniques to industrial applications with identifiable benefits. As a result, although a wide range of intelligent control techniques has been available already for many years, most of the applications in the process industry are based on more conventional techniques. Recently, as awareness of intelligent systems has grown, industrial problems and implementations have fortunately received increasing attention. In this paper, an intelligent supervisory-level system implemented at one of the major Finnish pulp mills to control a lime kiln fired with producer gas generated from biomass is presented. First, the major results of a field study are summarised, with special attention paid to burnt lime quality aspects. Next, a novel linguistic equations approach, which provides flexible methods for both modelling and control, is briefly described. The overall structure and main functions of the developed control system are then described with the main emphasis on the control of temperature and lime quality. Finally, the results obtained during the extended testing period of the system are presented and discussed.