Co-firing characteristics and fuel-N transformation of ammonia/pulverized coal binary fuel

•Flue gas emission characteristics of NH3/pulverized coal co-firing process with a wide range of NH3 blending ratios were studied in a drop tube furnace.•Effects of coal type, NH3 injection mode, temperature, excess air ratio (α) and NH3 co-firing ratio (ENH3) were compared to achieve efficient combustion and low pollutants emission.•Fuel-N transformation analysis was conducted to explore the nitrogen migration characteristics in high temperature NH3/coal co-firing process which have not yet been investigated before.•Through staged combustion strategy, ENH3 = 40 % is the optimal NH3 co-firing ratio which not only can reduce half of CO2 but also achieve the minimum NOx conversion rate and low residual NH3 level.