Experimental techniques for monitoring sedimentation in optically opaque suspensions

Measuring particle concentration in multiphase pipe flow using acoustic backscatter: generalization of the dual-frequency inversion method

A technique that is an extension of an earlier approach for marine sediments is presented for determining the acoustic attenuation and backscattering coefficients of suspensions of particles of arbitrary materials of general engineering interest. It is necessary to know these coefficients (published values of which exist for quartz sand only) in order to implement an ultrasonic dual-frequency inversion method, in which the backscattered signals received by transducers operating at two frequencies in the megahertz range are used to determine the concentration profile in suspensions of solid particles in a carrier fluid. To demonstrate the application of this dual-frequency method to engineering flows, particle concentration profiles are calculated in turbulent, horizontal pipe flow. The observed trends in the measured attenuation and backscatter coefficients, which are compared to estimates based on the available quartz sand data, and the resulting concentration profiles, demonstrate that this method has potential for measuring the settling and segregation behavior of real suspensions and slurries in a range of applications, such as the nuclear and minerals processing industries, and is able to distinguish between homogeneous, heterogeneous, and bed-forming flow regimes.

Novel On-Line Sedimentation Analyzer

The design and development of a novel vibrating reed technique for on-line measurement of the sedimentation kinetics of two-phase dispersions is described. The feasibility of operation of the analyzer has been successfully verified in conjunction with a variety of model and industrially relevant systems. The former include mono- and polydisperse glass ballotini/water mixtures with solids particle sizes and concentration ranges of 55-200 µm and 1.75-2.81% (v/v), respectively. Measured settling velocities are in good accord with those obtained from direct visual observation of suspension-clear liquid interfaces. The industrially relevant systems include agglomerated kaolin/water suspensions with solids concentrations as high as 20% (v/v) and oil/water emulsions with light phase concentrations in the range 30-50% (v/v). Copyright 2000 Academic Press.