Pyrolysis characteristics of low-rank coal in pressurized fluidized bed under different atmospheres

• Published in: Journal of analytical and applied pyrolysis Vol. 191; p. 107218
• Main Authors: Liu, Qiaoxia, He, Lei, Huang, Yong, Dan, Liu, Kong, Shaoliang, Gao, Yanan, Huo, Pengju, Wang, Linyang, Sun, Ming
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2025
• Subjects: Coal tar; Fluidized bed; High pressure pyrolysis; Semi-coke; Tar-rich coal; High pressure pyrolysis; Tar-rich coal; Coal tar; Semi-coke; Fluidized bed
• ISSN: 0165-2370
• DOI: 10.1016/j.jaap.2025.107218

This study investigated the effects of temperatures (500–650 °C), pressures (1.0–4.0 MPa), and various atmospheres (N2, 50 % N2 + 50 % H2, 50 % CO2 + 50 % H2, and 30 % H2 + 40 % CO2 + 30 % N2) on the distribution of pyrolysis products and tar composition of Hang Lai Wan coal (CHLW) in a kilo-scale fluidized bed. The results show that higher pyrolysis temperatures boost tar yield reaching 15.1 % under 600 °C, 3.0 MPa, and 30 % H2+ 40 % CO2+ 30 % N2, while the increase of pressure results in the reduction of tar yield which reaches a high level at 3.0 MPa. In contrast to N2, the participation of H2 and CO2 enhances tar production. As pressure rises, tar and semi-coke yields decrease, while the yield of gas, particularly CH4 and CO2, increases. Higher pressures result in a reduction of semi-coke pore volume and surface area, with coke surfaces taking on a regular, brush-like pattern that aids gas flow. High-pressure tar is rich in two-ring aromatics, whereas low-pressure tar is abundant in aliphatic hydrocarbons. Higher pressures may be conducive to the generation of active hydrogen, providing energy for bond breaking and enhancing the C-H2 reaction and catalyst efficiency within the coal structure. In summary, temperature and pressure significantly influence coal pyrolysis, H2, and CO2 promoting the formation of coal tar. [Display omitted] •Coal pyrolysis characteristics was studied by high pressure TG and fluidized bed.•Atmospheres (H2/CO2/N2) and temperatures were investigated during coal pyrolysis.•The high tar yield is 15.1 % under 600 °C, 3.0 MPa and 30 % H2+ 40 % CO2+ 30 % N2.•High pressure prefers forming two-ring aromatics, low pressure favors aliphatics.•Higher pressures are favorable to prepare active hydrogen and the C-H2 reaction.