Coupled negative-ion and HHO assistance stabilizes combustion and suppresses emissions in small-scale municipal solid waste incineration

Abstract Small-scale municipal solid waste (MSW) incineration is constrained by transient devolatilization, non-uniform air–fuel mixing, localized hot spots, incomplete oxidation, and pollutant release. This study evaluates coupled negative-ion-conditioned combustion air and on-demand oxyhydrogen (HHO) enrichment in a two-chamber batch incinerator. Four modes were compared—Ion OFF, Ion ON, Ion OFF + HHO, and Ion ON + HHO—using a 2.0 kg MSW batch, approximately 30 mm particles, and 5.6 m³ h⁻¹ airflow. Distributed temperature measurements and time-resolved gas analysis assessed thermal behavior, carbon oxidation, hydrocarbons, nitrogen species, and sulfur emissions. Negative-ion activation produced smoother thermal histories, while HHO addition was associated with enhanced oxidation of CO and volatile intermediates. The combined mode provided the best integrated response. Total NO x decreased from 70.0 to 49.3 ppm, corresponding to 29.6%. Experimentally measured PM, VOC, HCl, and PCDD/F emissions decreased by 30.6%, 30.8%, 6.1%, and 28.6%, respectively, under Ion ON + HHO relative to Ion OFF. H/O/OH/HO₂ chemistry and electrohydrodynamic transport provide plausible mechanistic interpretations, but radicals, local charge fields, and ion-induced velocities were not measured directly. Overall, coupled ion/HHO assistance improved combustion stability and multi-pollutant performance within the investigated operating window. These findings support further optimization across airflow, HHO dosage, ion intensity, and reactor scale.