| Under the developing demands of low-carbon and green industrialization, the low speed tissue paper machine has been obsoleting by domestic tissue paper manufacturer owing to its heavy energy-consumption and serious contamination. It was replaced by the medium speed or high speed tissue paper machine. However, pulp refining is the most important section in the papermaking process. Compared to the low-speed tissue paper machine, the new tissue paper machine puts forward more strict requirements of the quality of stock. At present, the constant power pulp refining control scheme that applied in most pulping lines can’t guarantee the stable quality of stock,(i.e., hard to maintain steady beating degree). Therefore, the quality stability of pulp refining is an important research subject in the field of tissue paper. This thesis takes the pulping section of high speed tissue paper machine pulping and paper line in Hebei as controlled object, and is funded by the project of key science and technology innovation team in Shaanxi province. Surrounded with beating degree soft-sensing technique and constant beating degree pulp refining control system, the study of technology application was launched. The main works are presented as follows.I. Research on modelling of beating degree soft-sensing based on SVM.Aimed at the research status that large numbers of training data were needed and generalization was insufficient, the scheme of beating degree of soft measurement based on SVM was proposed, and it was compared with the neural network. The parameters of beating degree model based on SVM are optimized via grid search and cross validation, and the beating degree model was established with good fit ability and excellent generalization. Took good advantage of small sample training of SVM algorithm, the correction scheme of beating degree based on SVM was designed.II. Research on the control strategy of constant beating degree and design of interlock protection scheme.Aimed at the disadvantage that the quality of stock in traditional constant power control scheme is uncontrollable, a kind of constant beating degree control schemes based on SVM soft-sensing technique was proposed. Through researching the relationship between power and beating degree, a controller of beating degree was put forward and the cutter algorithm of refiner is modified. Through the analyzing of foreign advanced safety technology of the disc refiner, the interlock protection logic of pulp refining control system was designed. The protection logic, which can be unlocked progressively, can prevent the devices be damaged resulting from disc touch. Finally, the triple disc refiner can be protected comprehensively.III. Implement of stock-quality control system based on OPC technology.Owing to the massive peripheral equipment and complicated control system of the pulping line, it is difficult to implement the control system. Took the S7-400PLC as the hardware foundation and setting PCS7 software as the develop platform, the DCS of pulping line was implemented in this paper. The communication between upper computer and MATLAB was realized via OPC technology, and constant beating degree scheme was applied into the practical system. As a result, the stable control of pulping quality control system in pulping line is realized, achieving an excellent control effect.Taking actual project as the background, the designed DCS of pulping line scheme in this paper has been put into operation in October 2015. The practical running effect show that the constant beating degree scheme has a more stable control effect. Because of the varying duty ratio, the start time of refiner was shrank by 20%. The stabilized error of beating degree between measured value which was by soft sensor on line and laboratory value within ±0.5°SR, the rate of the first class product enhances by 4% and the stock consumption decline from 1.120 down to 1.055, promoted the efficiency of raw materials effectively. |
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