As I noted when I began this series, drying is just one of a myriad of industrial heat and mass transfer operations. Heat processing operations such as drying, evaporating, curing and calcining are related but distinct enough to be characterized. This month, I will continue to detail some of the more common industrial moisture removal and thermal processes and will distinguish some of the peculiarities relating to them.

Distilling

Distillation involves the separation of components of a mixture, most commonly a liquid, by producing a gas or a vapor and then condensing the so-formed vapor. Distillation is used extensively in the fractionation of volatiles and other organic compounds. Multistage distillation is common to achieve the final or various intermediate fractions.

Distilling is a separation process that will not typically change the chemical structure of the constituents.

Examples of distillation operations are found in the petrochemical industry and the chemical industries. Spirit alcohols, the type that puts the “P” in party, are largely distilled.

Dehumidification

This is a process that reduces the amount of vapor in a gas stream. Methods of dehumidifying gases include desiccant beds and molecular sieves, cooling of the gas stream to below the vapor dewpoint, and compressing the gas stream to force condensation.

Calcination

Calcining is a process in which a material is heated up to a temperature that will achieve a desired chemical reaction or modification of the material. This may be achieved by temperature alone, or it may require a controlled environment or the addition of reagents, or catalysts, into the process.

The term calcining is frequently interchanged with roasting. Roasting is more frequently associated with the food industry, where products such as coffee and cereals are roasted to enhance flavor, smell, body and color.

Incineration

Incineration is the process of combusting a product to reduce the mass and/or volume. The product may be a byproduct or undesirable product (toxic, noxious, odiferous, unstable, acidic, etc.). Incineration aims to produce an inert or harmless gas and residue.

Incinerators are frequently associated with the asphalt industry and with the remediation of contaminated soil, as well as eliminating volatiles from exhaust streams.

Afterburners or flares are common sights around refineries and certain chemical plants. In essence, these are gas incinerators for the flue gases or

byproducts of the process. PH