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

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, H-2, CO, C2H4, C2H6, C6H6, C7H8, C8H10, C10H8). The results show that, the maximum temperature difference between the core and surface of coal (10 mm) has reached 406 K at the bed height of 0.05 m. 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 0.08-024 m. 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. (C) 2016 Elsevier B.V. All rights reserved.