Physicochemical characterization and pyrolysis kinetic analysis of Moutai-flavored dried distiller's grains towards its thermochemical conversion for potential applications

Abstract

The physicochemical properties of dried distiller's grains (DDGs) were measured and the pyrolysis kinetics analysis was experimentally investigated by the non-isothermal thermogravimetric analysis (TGA) at four heating rates of 10, 20, 30 and 40 K min−1. The results of proximate and elemental analysis showed that DDGs contained relatively high contents of volatile organic components (VOCs, 89.4 wt.%) and carbon (47.0 wt.%), and a higher value of heat content (20.4 MJ kg−1), compared with some other typical agricultural residues feedstocks. The pyrolysis kinetics of DDGs sample were analyzed using the Friedman isoconversional method. The obtained effective activation energies vary with the degree of conversion: 151.2-176.3 kJ mol−1 (α: 0.05−0.10, T: 383–506 K), 176.3-206.4 kJ mol−1 (α: 0.10−0.60, T: 506–653 K), 206.4-320.5 kJ mol−1 (α: 0.60−0.95, T: > 653 K), which correspond to the thermal decomposition of hemicellulose, cellulose and part of lignin, and remaining lignin. And the decomposition temperatures of DDGs components shift to lower temperature, compared with those of typical lignocellulosic biomass, which is caused by the presence of high activity degraded enzymes during brewing process. The physicochemical properties and pyrolysis kinetic results have shown that DDGs has great thermochemical conversion potential for bioenergy. We anticipate these findings will contribute to the industrial application of DDGs pyrolysis to produce biofuel or high-value chemicals and materials.