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In this paper the technique of cross-correlating the void fractions derived from the transmission signals of two γ-sources is used for the non-intrusive study of bubble phenomena in gas-solid fluidized beds. Special attention is given to the optimization of this method with respect to the statistical uncertainty inherent to radioactive decay. Experiments in a 40 cm gas-solid fluidized bed illustrate that bubble velocity distributions can be obtained.

A radiotracer-based laboratory method for measuring the rates of metal volatilisation loss, i.e. emission from solid, metal(s) containing catalysts was developed and tested. The details of the method are illustrated on an alumina-supported CuO catalyst in which some CuO was labelled with 64 Cu. The method enables determination of emission rates of copper at pmol s −1 level and partial pressures of copper at nbar level.

A method is described for the utilization of 41 Ar as radiotracer for oxygen in a standard Rushton air-water contactor at steady state conditions without oxygen depletion. The compartmental analysis method is applied to appraise the mass transfer kinetics of the system. Results demonstrate the suitability of 41 Ar as a radiotracer for oxygen and that the system can be described as an open, three-compartmental model.