Analysis of heat and moisture transfer during drying of urea particles

Abstract

Urea is an inexpensive form of nitrogen fertilizer which is widely used in the agricultural industry. Urea as granule is produced through a drying process by which moisture content decreases to avoid operational issues. In this study, a numerical model is proposed for the drying of urea particles in the prilling process. The model is developed based on mass, heat, and hydrodynamic transfer equations for the urea particles and cooling air. The moisture and temperature variations of particles and cooling air at different heights of the prilling tower are calculated under different operating conditions. The shrinkage of particles due to the moisture loss during the drying process at different heights of the tower is considered. The model is validated with the real data obtained from a urea drying plant operated under steady-state condition. The result highlights that the model can be used to manipulate the operating parameters to improve product quality and to minimize urea temperature to prevent lamps and caking formation in the tower.

Keywords

• Moving boundary condition
• mixed convection
• particle drying
• shrinkage
• urea modeling