Study on the impact factors and kinetic analysis of thermal transportation process of semi coke from pulverize coal pyrolysis

Abstract

Thermal transportation is a crucial link between the pyrolysis of coal powder and the application of the main product semi coke powder. Taking the semi coke from a 10,000-ton industrial experimental pyrolysis device as the raw material, based on its non-isothermal TG-FTIR (Thermogravimetry-Fourier Transform Infrared Spectroscopy) experiment, an isothermal TG-FTIR experiment was conducted to simulate the thermal conveying process. The non-isothermal TG-FTIR experiment reveales that under different heating rates, the oxidation reaction of semi coke occurs around 300 °C. With the increase in the heating rate, the ignition temperature, maximum weight loss rate temperature, burnout temperature and maximum weight loss rate of the semi coke all increase accordingly. The isothermal TG-FTIR experiment indicates that as the temperature and oxygen content increase, the oxidation reaction is intensified significantly. The yield of major gaseous products such as CO₂, H₂O, and CO increase accordingly, but the output of CH₄ remains small as the lack of volatile content. The kinetics of the non-isothermal and isothermal oxidation processes were comparatively analyzed using various methods, and the calculation results showed good consistency. With the increase of semi coke conversion rate, the activation energy gradually decreases under non-isothermal oxidation conditions and the average values are 86.44 kJ mol⁻¹ (FWO method) and 73.88 kJ mol⁻¹ (KAS method), while it gradually increases under isothermal oxidation conditions and the average values are 71.45 kJ mol⁻¹ (model-free method) and 93.66 kJ mol⁻¹ (first-order reaction model method).