Influence laws of operating parameters on coal pyrolysis characteristics

Pyrolysis is a vital route to achieve clean and efficient utilization of coal. This work comprehensively summarizes coal macromolecular structures, and reaction mechanism, influencing laws of main operating factors of coal pyrolysis, as well as its co-pyrolysis with biomass. Coal pyrolysis originates from the cracking of its organic matters, which are composed of inordinately complicated 3-D macromolecular networks with interconnected pores. The whole process is complicated, undergoes five stages and its product compositions and properties vary with diverse reaction conditions. Temperature is the most influencing parameter to determine process extent and a high temperature dramatically cracks coal, which is favorable for volatile yield improvement. Coal type, particle size, atmosphere, pressure, heating rate, catalyst insertion, etc. also impact the process and modify product distribution and characteristics. Desirable target effect can be achieved by proper process parameters regulation. The addition of biomass can also optimize pyrolysis process, which promotes feedstock utilization efficiency simultaneously. Synergistic effects can be found during co-pyrolysis of coal and biomass, and high hydrogen content and inorganic components in biomass are responsible for the synergistic effects. • Macromolecular structures of coal are introduced. • Process and mechanism of coal pyrolysis are summarized. • Influencing laws of main operating parameters in coal pyrolysis are deeply analyzed. • Co-pyrolysis synergy exhibits products yield and quality improvement and harmful pollutants removal.