A pneumatic conveying duct of 0.2 m diameter and 1 m height has been chosen for simulation (Fig. 1). Similar duct diameter has been reported in the literature for single gas inlet [4,7]. The duct is provided with a main hot air supply before the solid feeding point and hot air entry at three other axial locations of 0.25, 0.5 and 0.75 m in the duct. Distribution of hot air to these entry points was 1 during the simulations.