Co-pyrolysis of Miscanthus Sacchariflorus and coals: A systematic study on the synergies in thermal decomposition, kinetics and vapour phase products

In this work, co-pyrolysis of Miscanthus Sacchariflorus (MS) and three ranks of coal, namely lignite (LC), bituminous coal (BC), and anthracite (AC), was performed at the analytical scale. The co-pyrolysis kinetic and products were analysed and compared theoretically and experimentally. The results revealed the synergistic effects of the coal characterstics and biomass blend ratio (BBR) on the thermal decomposition and the products in gaseous phase. The co-pyrolysis of MS-LC and MS-BC samples was characterised by three distinct stages, which were sequentially dominated by moisture removal, decomposition of MS and decomposition of coal. The activation energies of the co-pyrolysis process were different from the activation energies of the pyrolysis of individual MS and coal samples. The kinetics analysis showed that increasing the BBR increased the activation energies of the MS-coal blends up to 25% at the temperatures below 350 °C. However, at the higher temperature range, it decreased the activation energies of MS-LC and MS-BC blends but increased those of MS-AC blends. Both of the coal rank and BBR had noticeable impacts on the thermal behaviour during co-pyrolysis. The optimum positive synergistic effects were obtained on MS-LC blend with a BBR of 1:1. The FTIR analysis results showed the evolution profiles of CH4, CO, CO2, water, formic acid, phenol and xylene. All the products analysed showed L-peaks (250–400 °C) corresponding to MS decomposition. Increasing the BBR promoted the release of all the analysed products from MS-LC and MS-BC, indicating the synergistic effect of the co-pyrolysis.