Abstract: Hot-state experiments were conducted to investigate the influence of the change of bias concentration ratio of pulverized coal at primary air outlet on the ignition properties of primary air-coal mixtures in a 350 kW pilot-scale furnace. The furnace temperature at different axial and radial positions, and the concentrations of gaseous species O₂, CO and NO_x were measured in the primary combustion zone to study the effects of bias concentration ratio on pulverized coal ignition, NO_x emission and burnout properties for co-combustion of Shenhua bituminous coal and Shenmu pyrolyzed semi-char (with blend ratio of semi-char to bituminous coal of 1:1). Results show that, except for the bias concentration ratio of 1.0 the ignition and combustion properties of the fuel-rich jet are better than the fuel-poor jet; the steady combustion position of coke moves upward in the furnace, while the O₂ consumption and flue gas generation mainly concentrate on the fuel-rich side. With the increase of bias concentration ratio, the ignition stand-off distance shortens, the combustion stability in high-temperature region enhances, and the NO_x concentration decreases sharply. However, the difference in NO_x emission is only 20.27 mg/m³ between the cases with bias concentration ratio of 3.8 and 5.0 respectively, showing very small difference of NO_x emission. Therefore it is recommended adopting the bias concentration ratio of 3.8-5.0 for the co-combustion of semi-char and bituminous coal.