ABSTRACT
The majority of the processes with a solid phase are two-phase reactions, but three-phase processes also exist. For three-phase systems, the liquid phase is often used as a solvent, and a suspension is facilitated for the reactive gas and solid phases. Oxidation of zinc ore, that is, zinc sulfide, is a process in which the size of the reactive solid particle remains approximately the same: zinc sulfide is oxidated to zinc oxide. Similar reactions occur, for example, in the oxidation process of pyrite to hematite. Tank reactors, batch reactors (BRs), and semibatch reactors are often used for carrying out liquid–solid reactions. For instance, the production of carboxymethyl cellulose is carried out industrially in a BR, whereas sodium borohydride is produced in continuous tanks-in-series reactors. In mathematical modeling of reactors with a reactive solid phase, the description of changes in the solid phase is of considerable importance. Several models have been proposed for the reactive solid phase.
