Essential Physical and Chemical Unit Operations
Physical Unit Operations
Distillation
An operation to separate, by vaporization and recondensation, the different components of a liquid or liquefied mixture. This process utilizes the varying boiling points of each substance to be separated.
Filtration
A separation technique or process unit operation where a mixture of solids and fluids (gas or liquid) is passed through a porous filter medium. This medium, often part of a device called a filter, retains most of the solid components of the mixture.
Sieving
A method to separate mixtures of solid particles of different sizes by passing them through a sieve or colander. Smaller particles pass through the sieve’s pores, while larger ones are retained. This is a very simple method generally used for heterogeneous solid mixtures, such as stones and sand, where sand passes through the sieve and stones are retained. The sieve openings are usually of different sizes and are selected based on the particle size in the mixture.
Sedimentation
The process whereby solid material transported by running water settles to the bottom of a river, reservoir, flume, or a specially constructed device for this purpose.
Mixing
The process by which two or more substances are combined without a chemical reaction occurring that changes their components. Mixtures can be separated into their original components by physical (mechanical) means. They are classified as homogeneous and heterogeneous.
Milling
A process that seeks to extract juices from various agricultural products like sugarcane or grapes. The term “milling” commonly refers to the pulverization and dispersion of solid material.
Transportation
Transportation (from Latin trans, “across,” and portare, “to carry”) refers to moving people or goods from one place to another. Transportation is a core logistics activity for placing products at the right time and desired destination.
Drying
Consists of separating small amounts of water (moisture) or other liquid from a solid material to reduce the residual liquid content to an acceptably low value. Drying is usually the final stage of a series of operations, and the product is often extracted from a dryer for packaging.
Chemical Unit Operations
Combustion
A chemical reaction in which an element (fuel) combines with another (oxidizer, usually oxygen as O2 gas), releasing heat and producing an oxide. Combustion is an exothermic reaction that produces heat and light.
Oxidation
A chemical reaction that results in a compound where electrons are lost, thus increasing its oxidation state.
Saponification
A chemical reaction between a fatty acid (or a saponifiable lipid containing fatty acid residues) and a base or alkali, yielding a salt of the acid and the base as the main product. These compounds have the distinction of being amphipathic, meaning they have both polar and nonpolar (or apolar) regions, allowing them to interact with substances of disparate properties. Soaps, for example, are salts of fatty acids and alkali metals obtained by this process.