Influence of side aerations on the initiation of solids circulation and energy supplied in a U-type loop seal of a fluidized bed reactor

• Low-position side aeration most effectively initiated solids circulation. • High-position side aeration required a higher airflow to initiate circulation. • Low-position side aeration resulted in an increase in riser pressure. • Combined side and bottom aeration reduced the required total airflow. The initiation of solids circulation is a critical aspect of fluidized bed reactor operation, governed by the performance of the loop seal. This study aimed to determine the optimal side aeration position in the supply chamber that affects the efficiency of circulation initiation, the solids circulation rate during the initiation phase, and the overall energy consumption of the loop seal. Experiments were conducted using a riser with a cross-sectional area of 100 × 100 mm 2 and a height of 4500 mm, coupled with a U-type loop seal of identical cross-section comprising supply and recycle chambers connected by a 50 mm horizontal passage. Three side aeration ports were installed on the side wall of the supply chamber at different positions: along the centerline of the horizontal passage, at the top wall level, and above the horizontal passage. Silica sand with an average particle diameter of 320 µm was used as the bed material. Results showed that the centerline port facilitated the initiation of solids circulation more effectively than the other positions and yielded the highest solids circulation rate under a constant side aeration flow. Furthermore, the U-type loop seal with both side and bottom aeration required a lower total aeration flow than the conventional loop seal with bottom aeration only, resulting in reduced energy consumption.