Research (Process Engineering)

Development of Wurster Coater for Color Coating of Granular Material

Abstract

The Wurster coating is a technique used in pharmaceutical industries for coating aqueous, organic solvents, hot saturated solutions and hot melts over granular particles, spheres and tablets.

A simplified Wurster coater has been established in this research. A glass cylinder having a diameter of 2 cm and length of around 1 ft is used as fluidized bed. A metallic sieve of around 60 mesh size, flanged between plastic flanges is used as an air distributor and also serves as support for the bed of granular material. A plenum is provided below the air distributor for uniform air distribution. Hot air blower is used to provide hot air for the apparatus and it is ensured that it maintains a velocity in the fluidized bed greater than the minimum fluidization velocity (U_mf). A spray bottle is fixed across the fluidized bed in a way ensuring cross flow contact between fluidized particles and the coating material and supplies the material to be coated over the granular material. Granular polymer having a particle size of around 700 micron is used as a bed of particles and water based blue ink is used as coating material to simply demonstrate Wurster coating. Polymer is put in the transparent glass riser (cylindrical column) to a bed height of around 1.5 cm. The spray bottle is filled with the ink to be coated over polymer particles. Air blower is turned on and hot air is provided beneath the particle bed which fluidizes it in the bubbling fluidization regime. The ink is sprayed inside the bed with the help of spraying bottle. The pigment gets coated over the polymer particles and water vapors (formerly present in the ink as liquid water) leaves the fluidized bed with the hot air.

The Wurster coating showed a very convenient technique for coating of granular materials and tablets. It offers excellent control over the product quality because of extensive mixing in fluidized bed. It can be operated in batch and continuous mode and can provide high product throughput when required. This flexibility and ease of operation makes it a very suitable unit operation in pharmaceutical industries.

Team

Dr. Mohammed Ismail Bassyouni
Engr. Syed Waheed Ul Hassan
Engr. Umair Javed

Distinction
This project was selected among top 50 projects round the world in a contest conducted by King Abdullah University (KAUST) under their Winter Enrichment Program 2011.