Distributed activation energy model of pyrolysis kinetics of starch and lignin with blast furnace slag as heat carriers

Abstract

Molten blast furnace slag (BFS) can be used as heat carrier for biomass pyrolysis, which has high industrial value. Lignin (LG) and starch (ST) were chosen as model compounds of lignocellulosic biomass, which were mixed with different proportions of BFS, respectively. Thermogravimetry-process mass spectrometry studied the characteristics of LG-BFS and ST-BFS pyrolysis. The activation energies were obtained by Kissinger-Akahira-Sunose (KAS) method and four kinds of Distributed Activation Energy Model (DAEM) methods. The results showed BFS has little effect on the temperature of LG and ST pyrolysis. The average activation energy of LG-BFS-30% and ST-BFS-50% calculated by KAS method was 167.74 and 155.57 kJ∙mol−1 respectively, which meant the addition of 30% and 50% BFS promoted the pyrolysis of LG and ST, respectively. The activation energy distribution (AED) obtained by the four kinds of DAEM methods could reflect the actual pyrolysis process more completely. The results showed that the Double Gaussian distribution (GAUSS-2)and the distribution-free method (DAEM-NM) were more closer to the pyrolysis process of LG-BFS and ST-BFS. Compared with the pure LG, the CO2 content in pyrolysis gas decreased by 9.61%, and the CO content increased by 22.14% in the LG-BFS-30% pyrolysis. Compared with ST-BFS and LG-BFS, LG-BFS-30% was more conducive to the generation of CO.