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In situ mineral sediment characterization with light scattering and image analysis MacIver, Michael Ryan


In this study, optical backscattering (OBS) and in situ image analysis are used to measure sediment bed density and aggregate size. A method is described for the measurement and interpretation of OBS height scans to obtain a measurement of aggregate size and solid concentration profiles in sediment beds of flocculated minerals. It was found that when OBS height scans were measured during batch settling and from multiple angles at the end of batch settling, the resulting root-mean-square, 𝐹rms, and mean, 𝐹mean, signal values can be analysed to quantify the sediment bed solids concentration and aggregate size as a function of height in the sample. A size calibration method was applied which relates the 𝐹rms values obtained from model solid ceramic spheres and silica particles to 𝐹rms values measured from sediment beds of flocculated kaolin. An iterative fitting method is applied to obtain a calibration function which can be applied to obtain a quantitative description of solid volume as a function of height and time during the batch settling experiment, 𝜙s(ℎ,𝑡). Evaluation of the fitted solid volume versus height functions resulted in a reasonable relative error when compared with the measured solid volume in the sample. A brief analysis on a statistical interpretation of image data for various samples of flocculated mineral sediment beds is given. This study suggests that the evaluation of OBS signal values and high magnification image analysis can be applied on the lab scale for determination of aggregate size and sediment bed density and may form the basis of a measurement system that can be applied to larger scale batch settling or pilot thickening equipment to measure rheological properties and mass flux.

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