Chemical engineering largely involves the design and maintenance of chemical processes for large-scale manufacture. Chemical engineers in this branch are usually employed under the title of process engineer. Following is an example that illustrates the process engineering part of chemical engineering:

The difference between chemical engineering and chemistry can be illustrated by considering the example of producing orange juice. A chemist working in the laboratory investigates and discovers a multitude of pathways to extract the juice of an orange. The simplest mechanism found is to cut the orange in half and squeeze the orange using a manual juicer. A more complicated approach found is to peel and then crush the orange and collect the juice. A company then commissions a chemical engineer to design a plant to manufacture several thousand tons of orange juice per year. The chemical engineer investigates all the available methods for making orange juice and evaluates them according to their economical viability. Even though the manual juicing method is simple, it is not economical to employ thousands of people to manually juice oranges. Thus another, cheaper method is used (possibly the 'peel and crush' technique). The easiest method of manufacture on a laboratory bench will not necessarily be the most economical method for a manufacturing plant.