Acoustic chemometric monitoring of an industrial granulation production process—a PAT feasibility study

An acoustic chemometric Process Analytical Technologies (PAT) feasibility study of fluidized bed granulation of a fertilizer product (urea) is applied to a semi-industrial pilot plant (SIPP) in a final evaluation before implementation for full-scale monitoring of the industrial production process. Conventional process monitoring and control is sub-optimal due to slow and labour-intensive laboratory analysis: particle size and liquid urea-concentration (correlated with water content) which are typically delayed by up to some 2 + h of analysis time. It is critical to be able to detect process transients and unwanted upsets, e.g. critical conditions in the granulator which may lead to uncontrolled shutdown situations, necessitating days of labour-intensive work to clean the granulator. The acoustic chemometrics approach goes directly into a real-time, on-line domain. In this study we focus on:1.Optimal localization of acoustic sensors2.Testing of a new sensor type (high-temperature microphone) in a semi-industrial granulator3.Assessment of the feasibility to predict (by PLS-regression):
• bed movement (airflow trough granulator)
• liquid feed concentration (urea)
• reflux of fine material to granulator4.Monitoring and visualization of critical trajectories–early warnings–in an operator-friendly fashion.Results show that both process state and product quality can be monitored to a satisfactory degree, e.g. detecting unwanted lump-formation already at an incipient stage as well as bottom plate clogging. Such early warning allows process operators to change relevant process parameters (fluidization or atomization airflow, bed temperature, feed flux) to control product quality or to prevent critical shutdown situations. Successful validation of this type of PLS-prediction model signifies that acoustic chemometrics is now maturing into a proven on-line technology in process analytical chemometrics and PAT domains.