(429b) Investigation of a Pilot-Scale Fluidised Bed by Electrical Capacitance Tomography and Fluid Dynamic Simulation

The Aeromatic-Fielder? FlexStream? Fluid Bed is a new multi-purpose processor, which has been developed by GEA Pharma Systems Ltd. It makes use of the fluidised bed technology to achieve granulation, drying and coating in one processor. A pilot-scale fluidised bed (MP-4) has a capacity of up to 120 kg and three spray nozzles evenly mounted on the side walls near the bottom of the fluidised bed. Because of three processes in one, FlexStream? can potentially give superior product quality compared with the conventional top-spray granulation or wurster coating. However, its behaviour has not been fully understood with risks of uneven control of particle wetting or wet particles stuck as lumps just in front of the nozzles or elsewhere. Therefore, it is necessary to investigate the behaviour of FlexStream? fluidised beds, and to monitor and control the flow rate of air and liquid in the nozzle regions, aiming to ensure the product consistency and to improve operation efficiency.

The aim of this research is to investigate the hydrodynamic behaviour of an MP-4 fluidised bed with FlexStream? air and atomisation air spray nozzles by electrical capacitance tomography (ECT), and to provide an online monitoring and measurement tool for FlexStream? fluidised bed operation. This is the first time that ECT was applied in a real industrial process and on a pilot-scale fluidised bed. To demonstrate the ability of ECT with large-scale fluidised beds without disruption of the fluidisation process, 12 insulated capacitance electrodes were placed on the inner wall of the MP-4 fluidised bed. Two different fluidisation processes were tested: (1) bubbling without spray nozzles and (2) bubbling with spray nozzles switched on. With this ECT sensor, the working conditions of the nozzles and the MP-4 fluidised bed can be monitored. In this paper, test results and data analysis are given. Some key issues on the application of ECT in large-scale vessels in an industrial environment are discussed. To validate the ECT measurement results, a two-phase flow model has been used to simulate the process in the MP-4 fluidised Bed. Future work on ECT for scaling up from lab-scale to pilot-scale fluidised beds is given in the end of the paper