Method Study On Modeling And Optimization Of Pulp Bleaching Process

With the rapid development of China's paper industry,the demand for bleached pulp is increasing.Pulp bleaching plays an important role in pulp and paper industry,because the quality of pulp or paper,energy consumption,material consumption and environmental pollution are closely related to bleaching process,moreover,the production cost of bleaching section accounts for a large proportion of the whole paper production process.At present,most of the research on the optimization of pulp bleaching process focuses on a certain bleaching stage,and the research on the systematic modeling and optimization of bleaching process is lack.Some research have been done about pollutant reduction for specific bleaching unit,it is important to further reduce the energy consumption and chemical cost of bleaching by using optimization technology under the current pressure of emission reduction,so as to realize the global optimization of the whole bleaching process.In this paper,the bleaching experiments of different levels and different factors(Amount of bleaching chemical?Bleaching temperature?Bleaching time?Bleaching pH)were carried out for the typical bleaching technologies were designed and carried out.The correlation of various indexes and bleaching conditions were analyzed based on the theory of bleaching in this paper.IBM SPSS statistics software(SPSS)was adopted to fit and analyze the variation rules of quality indexes(whiteness?intrinsic viscosity?kappa number),pulp yield,pollutant content in bleaching wastewater(AOX)and bleaching conditions,then the corresponding mathematical models are obtained.The quality indexes of bleached pulp,the content of pollutants in bleaching wastewater(AOX)and the yield of pulp after bleaching are simulated and predicted by using the mathematical models.A typical ECF bleaching technology(D₀EpD₁D₂)was taken as an example in this paper,the establishment and application of the systematic model of bleaching process are elaborated in combination with the established module models above.Firstly,evaluation indexes of bleaching process are discussed and these calculation models are established based on the analysis of quality indexes,pollutant(AOX)content,bleaching yield in different bleaching units,combined with the mathematical relationship between them and the bleaching conditions.Secondly,the whole bleaching system is divided into independent bleaching modules according to the different functions.Based on results of bleaching experiments,the mathematical models of each module are established by curve estimation of SPSS;the systematic model of bleaching process is established by combining the module models and evaluation indexes calculation models,then the model is verified.The whole process of pulp bleaching was simulated by using the systematic model;pulp quality and other indexes with different process conditions were predicted,which provides a technical foundation for intelligent control and system optimization of bleaching process.A systematic optimization model of pulp bleaching process is established based on the systematic model eastblished above,which take the minimum cost of bleaching system as the optimization objective.In this paper,a typical ECF bleaching technology(D₀EpD₁D₂)was taken as a example,fmincon function of matlab was adopted to solve the systematic optimization model.The results showed that the pulp bleaching cost was reduced by 4.87%compared with that before optimization under the premise of meeting the quality indexes such as whiteness,viscosity and kappa number.