Realization of quasi-steady-state piled smouldering using sequential operation chambers for industrial treatment of biomass wastes

Piled smouldering has great potential for treatment and utilization of biomass wastes. However, its unsteady-state nature limits its industrial utilization, as well as treatment of smoke. This article addresses this issue by proposing the sequential operation of numerous smouldering chambers to realize steady- or quasi-steady-state piled smouldering. The superposition characteristics of sequential unsteady-state curves were analysed theoretically, and a code was developed to determine an appropriate number of piled chambers at an allowance oscillation percentage. Smouldering experiments were performed on a single mini chamber (length × width × height: 340 × 140 × 140 mm³) containing piled wood pellets mixed with wood powder. The superposition of sequential burning rate curves was demonstrated using the code based on the mass loss data of experiments. Analysis shows that the perfect-steady state is possible given the superposition value of the burning rate curve is a constant in this proposed system. Experiments show that the molar ratio of CO/CO₂ in smoke is almost a constant around 0.5 during densely piled smouldering, showing the great potential for self-sustained burning out the smoke. Based on the experimental results, the calculation results show that the relative oscillation range of burning rate (OSC) decreases from 75% to 3% while increasing the number of chambers from 2 to 7. This work provides a novel technology to enable quasi-steady-state smouldering for industrial utilization.