Increased options for automated fluidized bed control

Recent trials have demonstrated that the Parsum inline particle size analyzer (Malvern Instruments) can be used successfully to monitor particle growth in a fluidized bed.

As part of a joint development project between Glatt Ingenieurtechnik GmbH, Weimar, and Parsum GmbH, Chemnitz, the use of inline particle size measurement was investigated, under various operating conditions.

Complex flow regimes, high humidity and a very broad particle size distribution combine to make the measurement of particles within this environment a significant challenge. In tests involving the monitoring of lactose granulation the Parsum probe tracked particle growth throughout the entire process, generating data that opens up options for automated control.

Fluidized bed granulation is a widely used unit operation, particularly in the pharmaceutical, food and speciality chemical industries, but process control is frequently problematic and based on operator experience or trial and error rather than effective monitoring. Inline analysis and automated control can deliver dramatic efficiency gains and improvements in product quality/consistency; the key is finding analyzers that meet the requirements of the application.

The Parsum is an optical rod probe with no moving elements and measures particle size by detecting interruptions of a laser beam caused by material passing through it. It is insensitive to vibration and slight impacts. Once installed, usually in pipelines, falling zones or vessels, it requires no manual adjustment. An integral pressurized air feed ensures that the optical sapphire windows are protected from product build-up – a particularly important feature for potentially fouling applications. It is suitable for the measurement of particles in the size range 50 to 4000 microns at temperatures in the range minus 20 to 100ºC.