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In industrial practice, it is important to have a method for early detection of changes in fluidized bed behaviour, e.g., to warn about upcoming bed agglomeration. Recently, a number of new monitoring methods based on observing the non-linear dynamics of measured pressure fluctuations have been reported. In this paper, these methods for monitoring fluidization are discussed and the expected future developments are described.

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Vacancy concentrations and vacancy mobility are studied in stoichiometric NiGa. The thermal vacancy content, which is determined from density and thermal expansion experiments amounts to some percents. The activation energy for vacancy formation for the temperature interval in which the experiments are carried out is 0.20 eV. During the thermal expansion measurements an after‐effect in the macroscopic length is measured simultaneously. The annealing curves are well described by first‐order kinetics and from the temperature dependence of the time constants an activation energy for vacancy migration of (1.34 ± 0.04) eV is derived. On the basis of the present after‐effect measurements and tracer self‐diffusion measurements a diffusion mechanism is proposed for NiGa: nickel and gallium migration via nearest‐neighbour jumps and through single as well as divacancies.