Characterization and non-isothermal kinetics of Shenmu bituminous coal devolatilization by TG-MS

- The high heating rate promotes the release of evolved gases during coal devolatilization.
- The reaction order model can be described the H2 and C2H2 evolution.
- The JMA model and the standard Z-T-L model can be described CO2 and CO evolution.

The devolatilization characteristics and non-isothermal kinetics of gaseous volatile evolution of bituminous coal were investigated through simultaneous thermogravimetry-mass spectrometry (TG-MS). The TG-MS results indicated that the three types of coals possess similar devolatilization characteristics in terms of mass loss and gas evolution. A high heating rate slightly shifted the TG, derivative thermogravimetric analysis (DTG), and MS curves to a high temperature range and promoted the release of evolved gases. The kinetic parameters of gaseous volatile evolution were determined through a novel procedure. In this procedure, the kinetic model function f(α) was identified using the Málek method, and the activation energy E and the pre-exponential factor A were calculated with common isoconversional methods or a distributed activation energy model (DAEM). With the Málek method, the reaction order model (n = 2) was the most probable mechanism to describe the gaseous formation of H2 and C2H2. This finding implied that chemical reaction is a limiting factor of gas evolution. The evolved rate curve of CO2 and CO could be fitted and identified by subjecting the spectral peaks to multi-Gaussian analysis. A JMA model (n = 3) and a standard Z-T-L model were applied to describe various kinetic stages. Results revealed that the evolved CO2 and CO were mainly controlled by diffusion. All of the standard models failed to fit the gaseous evolution of CH4 and H2O. Therefore, CH4 and H2O possibly underwent a complex process involving different reactions and stages.