Before the 20th century, industrial processes were viewed as monolithic, proprietary sequences tailored to a specific product. For example, a brewery and a petroleum refinery were considered unrelated. The revolutionary insight, largely credited to Arthur D. Little in 1916, was that different industries often perform the same physical tasks. Moving a liquid through a pipe, heating a vessel, or separating solids from liquids are universal challenges.
In chemical engineering, a unit operation is a fundamental step or process used to transform raw materials into a desired product. It is a basic building block of a chemical plant or process, and it can be combined with other unit operations to create a complete process. what is unit operation