Numerical simulation and experimental analysis on nitrogen and sulfur oxides emissions during the co-combustion of Longyan anthracite and sawmill sludge

•Chars of LYA and DSS were shown as C0.9898N0.0070S0.0032 and C0.9618N0.0356S0.0026.•The formation models in co-combustion were updated.•SO2 and NO were both released at the initial stage of co-combustion.•SO2 emissions in co-combustion were all lower than that in LYA mono-combustion.•The reasons for low NO emission were derived.