Solid–Liquid Mixing

The focus of this chapter is on mixing operations in mechanically stirred vessels which involve dispersion of solids in liquids. The minimum agitation speed to achieve the just off-bottom suspended state, Njs, is defined, and experimental approaches to its determinations are provided. Correlations for the prediction of Njs are provided for different impeller-vessel configurations, geometric and physical parameters, and operating conditions. Correlations for the determination of solid–liquid mass transfer coefficients are also given, as well as the equations to determine the rate of solid dissolution, and the time to achieve complete dissolution. Limitations on the draw down of floating solids, and on the distribution of solids throughout the vessel are discussed. Examples for the calculation of Njs and other variables of importance in solid–liquid systems are provided.