Study On Pyrolysis Kinetic Model Of Cigarette Raw Materials

China is the largest tobacco consumer and producer all over the world.While creating value and contributing tax revenue,the tobacco industry is also seriously endangering people’s health.As the initial process of thermal transformation of tobacco,pyrolysis has an important influence on its combustion process.In-depth research on the pyrolysis characteristics of cigarette raw materials and the use of mathematical modeling methods to predict the pyrolysis process of cigarette raw materials is of great significance for reducing the content of harmful components in smoke and improving the quality of cigarette products.In this paper,a total of 49 cigarette raw materials from different production areas,parts,years and flavors were selected.Pyrolysis kinetic parameters were calculated based on thermogravimetric analysis and a pyrolysis kinetic model of cigarette raw materials that could reflect the heating rate and chemical information was established.This paper firstly obtained the TGA data of 49 kinds of cigarette tobacco at 9 different heating rates in the range of 10℃/min～400℃/min wide-range heating rate through thermogravimetric experiments,and further calculated the pyrolysis DTG data,and established a Gaussian peak-splitting method of the DTG curve with good fitting effect(R~2>0.99),that is,named after the four major components of volatile components,hemicellulose,cellulose and lignin,respectively representing the four corresponding pyrolysis components.The total amount of pyrolyzed substances in the temperature range,and the four component ratios obtained by Gaussian peak-fitting of each tobacco sample at a heating rate of 10°C/min were used as the limiting condition for Gaussian peak-splitting.The pre-exponential factor K_i and activation energy E_i of the four components of each tobacco sample under different heating rates of pyrolysis were obtained by fitting each peak curve obtained by Gaussian peak-fitting.On the basis of obtaining kinetic parameters,a kinetic model of pyrolysis of cigarette raw materials was established,which could reflect the effect of heating rate.The numerical method was used for fitting,and it was found that the power function can better characterize the relationship between the pre-exponential factor K_i of the four components in the cigarette raw material and the corresponding pyrolysis heating rate x_i(R~2>0.92),so as to establish the relationship between the kinetic parameters and the heating rate.the association(K_i=a·x_i~b).Then,the accuracy of the model was verified,and the results showed that the model could predict the kinetic parameters more accurately(relative error within 10%),and the model calculation results were in good agreement with the thermogravimetric experimental data(R~2>0.95).On the basis of the determination of chemical information related to cigarette raw materials through continuous flow experiments and chromatographic quantitative analysis and detection,as well as industrial analysis and elemental analysis experiments of tobacco,the complex nonlinear relationship between chemical information and corresponding kinetic parameters of cigarette raw materials was studied by random forest algorithm.relationship,development of a random forest model for predicting the kinetic parameters of cigarette raw material pyrolysis.The results show that the model can better predict the two kinetic parameters of the preexponential factor K_i and activation energy E_i of the four components in the training set(R~2>0.91).The model can predict the pre-exponential factor K_i(R~2>0.75)and activation energy E_i(R~2>0.70)of the four components within a certain error range,and the model can more accurately predict the pyrolysis process of cigarette raw materials(R~2>0.85).