Simulation methods of cotton pyrolysis based on ReaxFF and the influence of volatile removal ratio on volatile evolution and char formation

To understand the influence of volatile removal ratio from the system on pyrolysis characteristics of cotton, a simulation model was proposed by performing both non-isothermal and isothermal simulations using ReaxFF molecular dynamics. Thermogravimetric-Fourier transform infrared (TG-FTIR) was used to study the overall evolution behaviors of volatile from cotton pyrolysis as a reference to simulation results. In non-isothermal simulations, volatile was remained inside the simulation unit during the entire process, while in isothermal simulations a portion of volatile was removed from the simulation unit before starting next simulation at a higher temperature. Results showed that although the non-isothermal simulation method can predict a TG curve similar to the one obtained from the experiment and can reveal the initial evolution behaviors of the volatile, but the atomic contents of chars were unpractical. In isothermal simulations, 100, 80, 60 and 30 % volatile removal ratios (VRR) were employed to resemble the different extent of secondary reactions that volatiles undergo in practical pyrolysis. It was found that contents of aldehydes and C-H were mostly influenced by VRR; and simulations with higher VRR produced chars with lower O and H contents, being close to the practical chars. Simulations with 80, 100 % of VRR had a higher probability to match the reality.