Simulation of large coal particles pyrolysis by circulating ash heat carrier toward the axial dimension of the moving bed

• Published in: Fuel processing technology Vol. 154; pp. 227 - 234
• Main Authors: Zhang, Ya-Qing, Zhu, Jia-Long, Wang, Xiao-Hang, Zhang, Xi-Wang, Zhou, Shi-Xue, Liang, Peng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2016
• Subjects: Coal pyrolysis; Heat transfer; Large coal particle; Solid heat carrier; Volatile evolution; Large coal particle; Volatile evolution; Solid heat carrier; Heat transfer; Coal pyrolysis
• ISSN: 0378-3820; 1873-7188
• DOI: 10.1016/j.fuproc.2016.08.037

A heat transfer, reaction, pyrolysis mathematical model for the non-isothermal coal particles by using circulating ash as heat carrier toward the moving bed has been established. Combined with the Thermogravimetry-Mass spectrometry technology and Coats–Redfern integral method, the model has the ability to predict the temperature distribution of pyrolysis gas-coal-ash as well as the evolution characteristics of the main volatile products (such as CH4, CO2, H2, CO, C2H4, C2H6, C6H6, C7H8, C8H10, C10H8). The results show that, the maximum temperature difference between the core and surface of coal (10mm) has reached 406K at the bed height of 0.05m. The layer closer to the coal core has a higher but later peak value of the devolatilization rate. The evolution of the main volatile products is concentrated at the bed height of 0.08–0.24m. The velocity of the moving bed, blending ratio of ash to coal, coal particle size, preheating temperature of coal and initial temperature of ash have obvious influence on the devolatilization process. Radiation is the most significant factor affecting the devolatilization behavior. The model can be applied to different coal species. This study can provide a theoretic foundation for the amplification design of the moving-bed reactor in the poly-generation system. A heat transfer, reaction, pyrolysis mathematical model for the non-isothermal coal particles by using circulating ash as heat carrier toward the moving bed has been developed. The model can predict not only the internal pyrolysis behavior of coal particles but also the temperature distribution of pyrolysis gas-coal-ash toward the pyrolyzer. Combined with the multiple-reaction model, the evolution characteristic of the main volatile products is revealed. [Display omitted] •A mathematical model for large coal pyrolysis using ash heat carrier is developed.•There is a significant temperature gradient inside the large coal particles.•Devolatilization process has a transient delay compared with the heating process.•3–4min design residence time of the moving bed pyrolyzer is reasonable.•The model can be applied to different coal species.