Particle coating with composite shell in a pan granulator

Abstract

In this study, the coating of urea granules with a composite shell was performed in a laboratory-scale pan granulator. The composite shell of coated particles consisted of a filler and a binder. Aqueous solutions of sodium silicate, methylcellulose, and polyacrylamide were used as the binders. Powdery calcium carbonate was used as the filler. The influence of the pan rotation speed, the pan-tilt angle, and the binder type on coating performance and the product properties was investigated. The pan rotation speed varied in the range from 30–70 rpm and the pan-tilt was changed from 30° to 75°. The relative shell mass, crushing strength, moisture content of the coated particles, and particle size distribution (PSD) were determined. A mathematical model was developed based on the population balance equation with the main purpose of predicting PSD. Particles’ weight gain was assumed to be proportional to the ratio of the surface area of the given size particles and the surface area of all particles in the coater. A comparison of calculated and experimental cumulative distributions of particle size was performed. Good agreement was observed between the modeling and the measurements.

Keywords:

• Binder
• composite shell
• controlled-release fertilizer
• mathematical modeling
• pan coating
• particle size distribution

Additional information

Funding

This work was supported by the Council on Grants of the President of the Russian Federation [SP-1951.2021.1].