Soot process in a vertical methane-fueled furnace supplied with fuel through its primary inlet located at its bottom, and with air via two opposing horizontal air jets perpendicular to the direction of Fuel supply, are studied numerically under different operating conditions. Results show that increasing the inlet temperature of fuel and/or air favors soot generation, hence enhances thermal radiation to walls. Radiation to the walls also increases by increasing air supply rates under fixed overall excess air ratio (EAR) conditions. Increasing EAR favors soot formation in the circulating regions formed below air jets, but it enhances soot oxidation in the upper locations. Consequently the heat radiated to walls is reduced.