Chemical Engineers are often known as process engineers in professional life, but we do not design processes - we design process plants. Engineers design physical artefacts, and a process is not an object. Process plants, however, are – they are made of concrete and steel, wires and pipes, tanks and pumps. Processes happen in them.
The process designer specifies the physical sub-components of the plant and how these are to be connected and controlled in order to carry out the process safely, reliably and economically. The process is an emergent property of the specified collection and interconnection of parts.
The job of selecting and specifying the parts and their interconnections involves a great deal of professional judgement, as well as the judicious application of engineering science and mathematics. The documentation of these choices is done largely by means of drawings. Drawings allow the communication with other engineering disciplines which is necessary to optimise the plant design.
Drawings are the things which the people who will build the physical plant need to do their jobs. The plant itself is the ultimate deliverable, but the immediate deliverables are mostly drawings. This is process plant design, a rather messy, intuitive, collaborative, multi-disciplinary, multifactorial business. It involves knowledge of the needs of electrical, software and civil engineers, equipment suppliers and of those who will procure, commission and operate the plant. It also involves communication and negotiation with these other disciplines...
You'll have to get a copy of the TCE to read the rest (they hide all of their articles behind a paywall) but it covers many things I have written about on here before. There will be lots more on this in the book, chapters two and three of which also went to their publisher yesterday.