Fuzzy logic based optimization of a phosphoric acid plant experiences

A fuzzy logic project was carried out at the phosphoric acid plant in Siilinjarvi, Finland in 1990-1993. After the implementation, valuable experience about use and maintenance of this optimization system has been gained. The original system consists of two SISO-control loops for concentration control in two reactors and a large MIMO-system for optimization of the whole plant. In the case of the two concentration controllers some modeling work was done to compare the different control methods. The results of this simulation study are presented in this paper. Due to faulty operation of the computer hardware and basic software the system was not as effective as desired. The operators also had some problems in working with the application because the system was realized in a new computer that they were not familiar with. In this paper the original design of the fuzzy logic system is presented. The conversion work needed for transforming to a PLC-based system is described