Understanding the Pyrolysis Synergy of Biomass and Coal Blends Based on Volatile Release, Kinetics and Char Structure

Abstract

The devolatilization characteristics, kinetics, and volatile-char interaction mechanism during co-pyrolysis of a bituminous coal (BC) and four different biomass were deeply investigated with the integrated approaches to achieve new understanding of the pyrolysis synergy. The results showed that co-pyrolysis of BC and the biomass presented obvious synergy in the respects of volatile release, gas formation, pyrolysis kinetics, and char structure. Co-pyrolysis of BC and the biomass increased the maximum devolatilization rate and activated energy ( E ), but had no influence on initial and maximum devolatilization temperatures compared to individual pyrolysis below 380 o C. Co-pyrolysis of BC and the biomass produced more C–O and C=O bearing compounds, but less CO, CH 4 and C 2 + aliphatics. Compared with the woody biomass, blending the two herbs in BC generated less CO 2 and arenes, but more porous structures in the chars. The kinetic study suggested that co-pyrolysis of BC and the biomass obeyed 1.5 order reaction mechanism and the synergy in terms of E values was related to both biomass species and reaction temperatures. Furthermore, a new volatile-char interaction mechanism was proposed to interpret the existence of the external molecular interaction between BC volatiles and the bio-chars at the secondary pyrolysis stage within 380–650 o C.

Keywords: Pyrolysis, Biomass and coal blends, Synergy, Pyrolysis kinetics, char structure