Dynamic Interfacial Zone and Local Phase Concentration Measurements in Emulsions, Dispersions, and Slurries

Abstract

A non‐intrusive x‐ray transmission video based method for measuring local concentrations of one phase dispersed or emulsified in another, on‐line and without sampling, is described using illustrative examples. The method involves passing a polychromatic x‐ray beam through a multiphase fluid/slurry contained in an x‐ray transparent or translucent vessel. The leading dimensions for the unit cell for local concentration measurements are the cross‐sectional area of a single pixel (magnification dependent) and the length of the path followed by the x‐ray beam through the vessel (vessel dependent). Measurement frequency is dictated by the data acquisition system or the video format employed—typically thirty measurements per second. X‐ray transmission radiography is sensitive to small density differences. For example, in a prototype apparatus, the water content in a water‐in‐oil emulsion/dispersion is readily measured to within 5000 ppm. The water + nano scale silica particle content in a water + silica in oil emulsion/dispersion has a comparable uncertainty unless the particles aggregate or disaggregate in which case the uncertainty jumps to 5 wt%. The resolution limit for nano scale silica particles, with mean diameters less than 40 nm, in water is 2 wt%. However, the technique is more sensitive to larger particles. The vessel employed maybe made from any x‐ray transparent or translucent material such as glass, aluminum, beryllium, etc. Potential applications for the technique include both batch and continuous processes drawn from diverse application areas such as the food, environmental and phase separation sciences, as well as in the energy sector. Technique limitations and the role SAXS can play in addressing them are also discussed.