Waste-to-waste synergistic regenerative combustion of ultra-low concentration methane and coal gangue in...

To simultaneously improve combustion efficiency and reduce pollutant emissions during the co-combustion of ultra-low concentration methane and coal gangue, an orthogonal experiment was conducted on a custom-built fluidized bed platform. The study centered on three key parameters: mixing ratio (CR), secondary air ratio (r), and excess air coefficient (α). The coupling law of multi-operating parameters on the thermodynamic behavior evolution of fluidized combustion and the formation mechanism of pollutants was systematically revealed. The results indicate that the mixing ratio (CR) exerts the most significant influence on combustion efficiency, followed by α and r. Furthermore, the combustion efficiency exhibits a non-monotonic trend specifically, an initial increase followed by a subsequent decrease as each parameter varies. In the process of operation, the best working condition combination is CR = 0.3, α = 1.46, r = 30 %. In terms of pollutant emissions, the improvement of CR can effectively inhibit the formation of SO₂ by strengthening the reducing atmosphere. The optimization of r significantly reduces NO_x emissions by enhancing the reduction effect in the dense phase region and the low temperature inhibition effect in the dilute phase region. The regulation effect of α is reflected in the coupling effect of gas-solid combustion kinetics and thermodynamic conditions, showing complex nonlinear regulation of SO₂ and NO_x in different intervals. This study innovatively proposed and verified the multi-operating parameters coordinated control mechanism of fluidized combustion, and quantitatively analyzed the weight and law of each parameter on combustion efficiency and pollutant emission. The research findings establish a new theoretical framework and engineering optimization pathway for the efficient and clean utilization of low-concentration gas and coal gangue, offering important implications for achieving the national "dual-carbon" goals.