Co-pyrolysis of platanus wood and bituminous coal: Product distributions, char pore analysis and synergistic effects

Abstract

The product distributions and gaseous product composition during the co-pyrolysis of platanus wood (PW) and bituminous coal were explored by employing a drop tube fixed-bed reactor. The pore properties of co-pyrolytic char were investigated via Brunauer-Emmett-Teller (BET) and fractal theory analyses. Synergistic effects were examined by comparing the experimental and theoretical product yields, gas compositions, and fractal dimensions (D) of residual char. Complex synergistic effects affecting product yield and gas composition were observed. Significant positive synergistic effects promoting gas formation were found with 50% PW mass ratio within the temperature scope of 800–1000 °C. In contrast, negative synergistic effects inhibited the formation of char and liquid products. The H2 composition increased owing to the positive synergistic effects at a pyrolysis temperature of 1000 °C, whereas remarkable positive synergistic effects on CO generation were observed with 30% PW blending ratio from 600° to 700°C. PW promoted the specific surface area of co-pyrolytic char. The D values of co-pyrolytic char increased as the PW blending proportion was enlarged. Moreover, the D of residual char indicated higher values than the theoretical results. The higher content of volatile matter and the existence of alkali and alkaline-earth metals in PW were beneficial for forming mesopores and micropores with pore aperture of smaller than 10 nm, resulting in the complexity promotion of the pore structure. An exponential correlation between D and surface area was observed. This study provides important information for devising and optimizing co-pyrolysis systems for biomass and coal.