By Sean Moran, C.Eng, P.Eng, Expertise Limited
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 a physical object. Process plants are – they are made of concrete and steel, wires and pipes, tanks and pumps. Processes happen in them.
The process designer specifies the physical subcomponents., and how they are to be connected and controlled in order to safely, reliably and economically carry out the process. The process is an emergent property of the specified collection and interconnection of parts.
The process 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.
This is process plant design, a rather messy, intuitive, collaborative, multi-disciplinary, multifactorial business. It involves negotiation and discussion with electrical, software and civil engineers, equipment suppliers, those who will procure, commission and operate the plant.
The precise process conditions to be used are actually not that important a part of the whole activity, and if we are honest with ourselves, we cannot as designers predict the conditions within the plant as constructed to a high degree of precision. A good process plant designer makes sure that the plant design envelope encompasses the range of conditions that the plant is likely to see, and that it is robust enough to maintain adequate performance across that envelope.