Acoustic diagnostics in process plant: application of pattern recognition techniques

Sound generated in process plants can be used to monitor the progress of the reactions taking place within a vessel, or to monitor fluid flows within a process line. The sound transmits through the structure of the plant itself, and can be picked up by a sensor mounted externally on the vessel. All that is necessary is that there be a satisfactory acoustic path from the process fluid to the sensor. This may require introducing a solid waveguide probe through the wall of the vessel, or an existing part of the structure may be used-for example a thermocouple probe. The technique is non-invasive and does not require sampling of process streams, avoiding the associated problems of ensuring a representative sample and the potential risk of contamination of the product. The Acoustic Diagnostics in Process Plant project began in 1990. The aim was to develop acoustic techniques to be used in process plants. Work has been targeted at developing two demonstrator acoustic monitoring systems in diverse applications. Monitoring of batch crystallisation reactions was the first to be selected, following initial trials at a dyestuffs plant. Acoustic impulses generated by collisions between solid crystals suspended in the process fluid and the agitator, or parts of the plant structure, can be monitored and used as an indicator of the progress of the reaction. Glass ballotini are used in the experiments and pattern recognition methods have been used to discriminate between the different sizes of the ballotini.<
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