Apricot kernel shells pyrolysis controlled by non-isothermal simultaneous thermal analysis (STA)

In order to clarify relationship between apricot kernel shell biomass slow pyrolysis mechanism and its main constituents (viz. hemicelluloses, cellulose and lignin), the reactivity effects of main constituents on pyrolysis characteristics were determined by the non-isothermal simultaneous thermal analysis. It was found that four-step (parallel) reaction model is suitable for studying the slow pyrolysis process, within the semi-global model which excludes the strong interaction between biomass constituents (pseudo-components). The application of the proposed model was allowed by the results obtained from KAS iterative isoconversional (model-free) approach. The valorization of the model was confirmed by the process optimization. The complex (cumulative) apricot kernel shell pyrolysis rate curves at different heating rates are successfully resolved into the individual decomposition rate curves (arising from thermal conversion of hemicelluloses, cellulose, and primary/secondary lignin fragments) by four-parameter Fraser–Suzuki function. Besides hemicelluloses and cellulose pyrolyses, the proposed model distinguishes primary and secondary lignin reactions, which enhance the gaseous products releasing (primarily CO and CO gases) and charification of the solid residue (increased the bio-char yield).