13.7. Solids Modeling

Solids handling is abundant in the process industries. Starting from the fluidized catalytic cracking (FCC) unit in a petroleum refinery to the modern power plant using coal, various unit operations involve the handling of solids. Solids may significantly affect mass, momentum, and energy balances in a chemical system even if the solid is inert. In addition, the particle-size distribution of the solid can affect the operation of solid handling equipment such as cyclone separators, crushers and grinders, and crystallizers. Hence, for simulating these processes accurately, the fundamentals of solids modeling must be understood.

13.7.1. Physical Properties

Sections 13.2 and 13.4 provided a detailed account of the importance of selecting the appropriate physical property methods and models. Solids modeling is no exception to this approach. The systems involving solids can be composed of various well-defined solids (such as SiO₂, Fe₂O₃, etc.) or solids that themselves are heterogeneous mixtures of complex materials (such as coal or biomass). In addition, various polymorphs may be present. Polymorphs are different crystalline or amorphous forms of the same solid in which molecules have different arrangements and/or different molecular conformation. The polymorphs usually differ in their dissolution rate, melting temperature, reactivity, sublimation temperature, and other attributes. The properties of the solids depend not only upon their composition but also on their structure which is almost impossible to characterize in a process simulator. Therefore, many solids that are frequently encountered in the process industries are not available in simulator databanks. Quite o....Section 13.6.