Numerical simulation of enhanced sludge drying via granulation and optimized dynamic transport

Aiming to address the issues of low efficiency and poor uniformity in sludge drying processes, this study systematically investigates the effects of sludge granulation parameters and conveying control methods on drying characteristics. Results show that sludge thickness, spacing, and length significantly affect drying performance by altering the specific surface area of the material. A large specific surface area improves contact between sludge and hot air, thereby enhancing the drying rate. Optimal dehumidification and uniformity were achieved when the sludge spacing was 20 mm, thickness was 10 mm, and length was 70 mm. Conveying speed also has a significant impact on drying efficiency, as its adjustment changes the trend of moisture content variation and the airflow distribution within the drying chamber. The best performance was observed at a conveying speed of 0.053 mm/s, where the moisture content was reduced to 10% in 92 min. In addition, rational conveying control can suppress the adverse effects of vortices at the bottom of the drying chamber, improving overall efficiency. Stagnation time and position are also key factors for drying uniformity. A staggered stagnation strategy, with 30 min of stagnation for the upper left and lower right layers, reduced the standard deviation of moisture content from 12.4% to 5.9%, significantly improving consistency and product quality. The specific energy consumption decreased from 1.04 MJ/kg to 0.71 MJ/kg, representing a reduction of about 31.7%. This study provides valuable insights into improving sludge drying performance through granulation parameter optimization and dynamic conveying control.