Although the pulp and paper industries have used balancing calculations and process control for a very long time, the scope of modelling and simulation applications is not yet as complete as it could be. One reason is that we seldom have steady-state conditions and we lack adequate measurements for on-line control for many quality variables. Also the nal quality of paper depends on many process elements in a complicated and nonlinear way. Control actions for these processes are usually based on skill and experience of the operators. There is a need to improve paper machine performance to increase the competitiveness of the mills. In turn, this makes necessary the application of operator decision-support tools based on dynamic

optimisation in order to allow process operators and engineers to manage complex dynamic problems in an efcient and ecologically sustainable manner.