Modeling And Control Of Kraft Pulping Digester

Sixty percent of pulp yield is chemistry pulp in the world, and above 90% of chemistry pulp is kraft pulp. Cooking process is an important workshop section in kraft pulp. On the one hand, the quality of cooking process influence directly the following workshop section and quality and yield of paper and benefit of plant. On the other hand, in view of cleaner production, the objective in optimal control of a continuous pulp digester is to achieve maximum pulp production at a specified kappa number with a minimum of chemicals and energy input. The control strategy based on the idea is the feasible approach to reducing pollution and realizing cleaner production. Therefore, it is necessary to study a suitable model and advanced control system on a continuous pulp digester. In addition, it is urgent affairs to develop the related measurement instrument with lower cost.Based on the above objective, as one part of the work about distributed intelligent modeling and optimization method for cleaner production of pulp and paper industry (National Science Fund, No. 69974034), the measurement technology of effective alkali, the model of continuous digester and control system are summarized in the introduction of this paper and studied deeply in the following chapters. The main content of the thesis include: (1) A dynamic model of the continuous pulp digester is developed by applying the method of orthogonal collocation and a simulation study is present showing dynamical effects of input and parameter changes. (2) Subspace identification based inferential control is applied to a continuous pulp digester. And the idea is tested on the continuous digester. (3) Based on the principle of conductance measuring liquor concentration, the online soft-measure system of effective alkali concentration is designed.