Investigation on the performance optimization of sludge spray nozzles based on computational fluid dynamics coupled with discrete phase model

Abstract To reduce the energy consumption and operational costs associated with thermal sludge drying, this study integrated spray technology with sludge drying and designed a spray nozzle specifically for sludge spray drying. Theoretical research and numerical simulations were employed to examine the impact of nozzle structural parameters on the spray field, optimizing the nozzle's spray angle to improve sludge drying efficiency. The results show that as the nozzle angle increases, the pressure rises and the velocity and turbulence energy first decrease and then increase. When the nozzle angle was 120°, the sludge droplets gained the maximum kinetic energy, which maximized the effective area of the spray, resulting in the best crushing effect and the highest sludge particle drying efficiency. Finally, industrial experiments were performed, demonstrating that sludge with a moisture content of approximately 85% was reduced to about 35% after spray drying treatment.