A CAPILLARY SUCTION PROBE FOR BUBBLE-SIZE MEASUREMENT

This paper describes a fully submersible capillary suction probe technique developed for bubble size measurement in large-scale stirred-vessel reactors. The method uses a vacuum to continuously withdraw a small stream of gas-liquid dispersion through a short capillary tube with a funnel-shaped inlet. Photodetectors mounted on the tube are used to detect the bubble slugs, producing a binary-waveform type signal. The probe is interfaced to a high-speed data acquisition system controlled by a microcomputer, to allow storage of large amounts of data and fast processing. Some aspects of two-phase flow inside the capillary are discussed, as well as details of the probe calibration procedure. The automated bubble size measurement technique achieved very good reproducibility of results and very high rates of sampling from bubble sizes down to 0.3 mm diameter. Typical results obtained in a 1.0 m diameter stirred vessel are presented.