Effect of Mixing Modes on Integrated Process of Co-pyrolysis of Coal and Biomass with CO2 Reforming of Methane to Improve Tar Yield
The influence of mixing modes on the integrated process of co-pyrolysis of Naomaohu coal (NMH) and elm (ELM) with CO2 reforming of methane (CP-CRM) was investigated over Ni-based catalysts prepared by ball milling. Three mixing modes—NMH/ELM, ELM/NMH, and Blends—were examined and compared with co-pyrolysis under N2 (CP-N2). Results show that product distribution was significantly affected by mixing mode. The Blends mode achieved the highest tar yield, increasing by 35.29% compared with CP-N2. Light oil content in tar was higher, while pitch content was lower for Blends relative to layered modes. Phenols content in tar from Blends was 19.52% higher than CP-N2, and free radical concentration in tar was higher, attributed to enhanced heat and mass transfer between particles by mechanical mixing, promoting complete pyrolysis and efficient utilization of hydrogen-rich free radicals (·H, ·CHx) to suppress secondary cracking and polymerization. In contrast, NMH/ELM mode in CP-CRM improved phenols content by 33.27% over CP-N2. Free radical concentration in tar during CP-CRM was lower than in CP-N2, indicating timely stabilization of pyrolysis radicals by reforming-generated radicals. These findings provide guidance for regulating tar yield and composition in co-pyrolysis processes.