UNDERSTANDING THE DYNAMIC BEHAVIOR OF KAMYR DIGESTERS

This paper presents process sensitivity and interaction analysis for K amyr digesters, used for the production of paper pulp from wood chips, using the Purdue dynamic model. In sensitivity analysis, responses of blow line Kappa number to step changes in 17 scaled input variables w ere investigated. The responses to the five most significant inputs, i .e., white liquor caustic concentration and flow rate, upper and lower heater outlet temperatures and extraction flow rate, were approximate d, with good accuracy, by First Order Plus Time Delay transfer functio ns using SigmaPlot(C). Interaction analysis has been carried out using Relative Gain Array, Singular Value Decomposition and a condition-num ber scaling technique to improve the ill-conditioned system. For the p urpose of pairing in multivariable control, and using a 4x4 gain matri x, it has been shown that blow-line Kappa number is to be paired with lower heater outlet temperature, extraction caustic concentration with white liquor flow rate, extraction temperature with upper heater outl et temperature, and solids fraction in the extraction stream with whit e liquor caustic concentration. (C) 1998 Elsevier Science Ltd. All rig hts reserved.