| Six kinds of land biomass (fir wood, pine wood, cotton stalk, wheat straw, rice husk and pear leaves) were selected as the experimental materials, and their thermal decomposition behavior by thermogravimetric analyzer in nitrogen atmosphere were studied in this paper. The paper focused on the effects of the heating rate and six kinds of inorganic additives (NaOH, Na2CO3, Na2Si03, NaCl, TiO2 and HZSM-5) on pyrolysis behavior of three kinds of typical lignocellulosic biomass (fir wood, pine wood and cotton stalk). The results showed that the pyrolysis temperature zone and the maximum weight loss rate corresponding to the temperature were increased with the heating rate increasing, but the largest thermal decomposition rate is reduced. Four kinds of sodium compounds made the reaction move to the low temperature zone. The stronger the alkaline, the lower the initial thermal decomposition temperature and the temperature corresponding to the maximum weight loss rate. The three kinds of alkaline compounds (NaOH, Na2CO3 and Na2Si03) reduced the maximum weight loss rate of biomass significantly, and they make the pyrolysis more exothermic.On the basis of visual programming language, Visual Basic 6.0, "thermal analysis kinetics calculation software" was developed. Compared with traditional manual method of calculation, this software was much simpler. It can avoid the calculation errors effectively which make the results much more accurate and improve work efficiency greatly. Two classical methods (FWO method and Popescu method) were employed in this paper to give kinetic analysis for obtaining global pyrolysis kinetics parameters and determining the best mechanism functions. The results showed that the activation energy of the two method were basically consistent and the activation energies increased as the conversion rate increased.The pyrolysis kinetics of a multi-component model was built by analyzing the mechanism of thermal decomposition of biomass. The three-component of thermolysis kinetic parameters were estimated by nonlinear least squares algorithm and it was found that its thermal decomposition activation energy was not influenced by heating rate, which indicated the thermal decomposition mechanism had not been changed in the range of heating rate. The fitting result showed that the alkline additives decreased the thermolysis activation energies of cellulose and hemicellulose, whereas the neutral additive NaCl had no marked influence on the thermolysis activation energies of cellulose and hemicellulose and the surface acidic additives (TiO2 and HZSM-5) increased them slightly. All the studied additives had no apparent effects on the thermolysis activation energies of lignin. The three component kinetic model is more reasonable than the global kinetic model when used for calculating the kinetic parameters of lignocellulosic biomass thermolysis. |
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