Research On Modeling For High Consistency Refiner And Optimization For Pulp Refining Process Of APMP

As one of the promoted industries of the national light industrial revitalization planning, the main development goal of the papermaking industry is to wash out the behindhand productivity and push out to a way of low-carbon economy with energy saving and consumption decreasing. High consistency pulp refining is one of the important sectors with large energy consuming in papermaking process and is one of the important development orientation of pulping crafts. It will be of great theoretical and practical significances for the enery saving and consumption decreasing of high consistency pulp refining process to build up the mechanical and energy consumption models of high consistency refiner and design structure-reasonable high consistency refiner and its control system. By taking a high yield pulping equipment, high consistency conical refiner, as the research object, the mechanical and energy consumption models is investigated in this paper. A novel three-cone double-flow high consistency refiner is designed. Aiming at the high consistency refining process of APMP, the soft measurement algorithms of pulp refining degree and wet weight of the pulp quality indexes as well as the optimization control strategies of APMP pulp refining process are also investigated. Finally, A DCS control system of APMP pulp refining process based on SIMATIC PCS7 development platform is proposed. The main contributions of this paper are summarized as follows.1) The mechanism of high consistency pulp refining is opened out and perfected, which provides a theoretical reference for the optimized design of pulp refining process. It is pointed out in this paper that the low consistency pulp refining depends on the direct action between blades and fibres, while high consistency pulp refining depends on the mutual griding, crushing, kneading and distorting of the high consistency stock in the disc gap. The large amount heat energy induced by friction process can soften stock, which is useful for fibre separating.2) The mechanical model of the high consistency refiner is analysed and built up, which provides a theoretical basis for the optimized design of disc tooth shape. The force received by the high consistency stock in the pulp refining area is the sum of the friction force between discs and the mutual action force between fibres. The force received by frbres in high consistency refining area is not only affected by the performance of the high consistency stock itself, for example, the pulp consistency, the physical and chemical properties, etc, but also related with the pulp refining conditions, for examples, the transmitted pressure of stock, the rotated speed and the gap of disc refiner, etc.3) The energy consumption model of the high consistency refiner is analysed and built up, which provides a theoretical basis for largely decreasing the energy consumption of the existing high consistency refiner. The pulp refining process with high consistency is a complicated flow variable process. During the course of this process, there is not only the change of flow form, but also the change of physical form for the fibre material. The total energy consumption of the flow variable is the sum of the power of flow form change and the power of physical form change. On a specified condition of refining area structure and refining crafts, the pulp refining power can be changed by adjusting pulp refining ratio pressure. And the pulp refining effect will be changed correspondingly. The change of the gap between two refiner plates can regulate pulp refining ratio pressure.4) A novel three-cone double-flow high consistency refiner is designed. Based on the pulp refining theory and mechanical and energy consumption model mentioned above, by referring to the present refiner structure, a novel Three-cone double-flow high consistency refiner is designed. The proposed refiner integrates the flat refining area and conical refining area together and the refiner plate gap can be adjusted simultaneously. It is indicated by practice that the proposed pulp refining equipment is of such prominent advantages as low energy consumption, high efficiency, well pulp refining, little fibre cut-down and good papermaking performance.5) An artificial neural network based soft measurement algorithm of pulp refining degree and wet weight is investigated. A three-layered feedforward neural network consisting of an input layer, an output layer and a hidden layer is built up. The variables of the input layer are material-feed screw rotation velocity, the refiner dilution water flow and pulp refining current. The variables of the output layer are pulp refining degree and wet weight. The training samples are composed by the on-line data from the plant and the experiment data from laboratory. The neural network is trained by a modified BP algorithm to obtain the soft measurement models of pulp refining degree and wet weight.6) The optimization control of APMP pulp refining with high consistency and SIMATIC PCS7 based control system are conducted. Aiming at the pulping process of APMP, on the basis of the built steady state model, a group of suitable setpoint values of the craft parameters are found out to obtain the largest output and the lowest cost on the condition that the quality indexes of pulp refining degree and wet weight fulfil the craft requirement. That is to say, good quality, high output and low consumption. A multi-objective optimization model composed by quality objective function, output objective function and cost objective function is built up. The multi-objective optimization problem is transformed into a single objective optimization problem by constructing evaluation function via multi-objective plan methods. The solution is obtained by using nonlinear planning methods with the help of Matlab optimization tool box. The DCS implementation of APMP pulping process is finished based on the development platform of SIMATIC PCS7.A relatively full and detailed research is conducted in this paper on the mathematical modeling and design for high consistency refiner as well as the optimization control of pulp refining process with high consistency from the aspect of applied technology. During the course of the study for Ph.D, the candidate has acquired such achievements as follows:21 pieces of scientific papers are published in which 4 pieces are indexed by El and another 6 pieces are indexed by ISTP; 4 pieces of national practical patents are authorized,4 pieces of scientific research projects of national rank and province rank are permitted in which one piece is national natural science fund project. One research has acquired the first-rank award of science and technology of Colleges and Universities in Shaanxi Province.