Pulp cooking control and wood species change control for a Kamyr continuous digester

We developed the "kappa number control system" for the Kamyr kraft pulp continuous digester which has two kinds of a multiple linear regression model for softwood and hardwood chips that control the cooking zone temperature to stabilize the kappa No. quality at the Kure Mill. This model consists of an H-factor and residual effective alkali (EA) concentration terms and a constant term, etc. The constant term is modified to match gradual unexpected fluctuations using an exponential smoothing method. Furthermore, complicated operations of changing wood species are frequently executed in this digester, and many control elements have to be changed adequately according to appropriate schedules for maintaining the pulp quality stable during such disturbance operations. For this purpose, we introduced the "wood species change and production rate change control system" which also changes a series of operations automatically.