Effect of binder addition on combustion characteristics of cotton straw pellets and kinetic analysis

In this study, the combustion characteristics and kinetics of cotton straw (CS) particles mixed with polyethylene (PE) film and coal gangue (CG) were investigated. The co-combustion characteristics of CS mixed with PE and CG at different heating rates were revealed by the thermogravimetric method and differential thermogravimetric method. The ignition temperature, burnout temperature, and maximum weight loss rate were measured, and the comprehensive combustion and flammability indexes were calculated. The results showed that the composite combustion characteristic index and flammability index increased with the increase in heating rate. The addition of PE and CG additives could effectively extend the combustion time. The Coats-Redfern (C-R) reaction model and N-order reaction model were used to evaluate the kinetic parameters of the blends. The results showed that 12.5% PE + 12.5% CG particles had the lowest activation energy (Ea = 103.73 kJ·mol⁻¹) at the volatile combustion stage. The dynamics conform to the third-order dynamics model. In addition, the applicability of C-R model, Flynn-Wall-Ozawa (FWO) model, and Starink model in the calculation of activation energy was explored, and it was found that the FWO model is not suitable for the calculation of activation energy of biomass pellet combustion kinetics. This study provides a new method for the development and utilization of mixed fuel particles of cotton stalk and solid waste and expands the application prospect of biomass.