Kinetics and reaction chemistry of pyrolysis and combustion of tobacco waste

In this work, the kinetics and reaction chemistry of the pyrolysis and combustion of tobacco waste were investigated. The physicochemical analysis and thermogravimetric analysis under N2 and air atmospheres of the tobacco waste sample mainly consisting of tobacco leaves were performed. The physicochemical analysis results showed that the tobacco waste sample contains more ash and N than other types of lignocellulosic biomass. The DTG curves obtained from the numerical differentiation of the experimental TGA curves have many fluctuations and need to be smoothed for subsequent kinetic analysis. The Savitzky–Golay smoothing algorithm was found to be effective for the smoothing the DTG curves of the pyrolysis and combustion of tobacco waste. The pyrolysis process of tobacco waste can be divided into four stages: (a) the water evaporation generated by the cleavage of aliphatic hydroxyl groups and strongly bonded hydrated compounds, and the degradation of simpler saccharides and other low temperature decomposing components of tobacco waste in the first stage; (b) the decomposition of hemicellulose and pectin, and the formation of nicotine in the second stage; (c) the decomposition of cellulose in the third stage; and (d) the decomposition of lignin and char formation in the final stage. The combustion process of tobacco waste can be divided into three stages: (a) the same as the first stage of the pyrolysis process; (b) the oxidative pyrolysis of tobacco waste components; (c) the combustion of the oxidative pyrolysis char. The Friedman differential and iterative linear integral isoconversional methods were used for the estimation of the effective activation energies of the pyrolysis and combustion of tobacco waste. The results showed that the effective activation energies of the pyrolysis and combustion of tobacco waste varied strongly with the extent of conversion. The obtained effective activation energies are in the ranges of 144–338 kJ mol−1 and 118–257 kJ mol−1 for the pyrolysis and combustion of tobacco waste, respectively. The relationship among the effective activation energies, temperature range, degree of conversion, reactions of tobacco waste components was also obtained.

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