Control parings of a de-oiling membrane process

In offshore oil and gas productions increased attention is directed at the oil-water separation process, as environmental laws demand lower hydrocarbon concentrations in the discharged produced water. Membrane filtration is one possible candidate for significantly improving separation efficiency. However, fouling is one major challenge, where contaminants accumulate within the membrane and thereby adds additional flow resistance. This paper investigates the possibility of improving reference tracking and reducing fouling by improving control pairings and actuator placement. This is achieved by investigating the interaction between commonly deployed decentralized control loops on a membrane process model. The relative input-output interactions are evaluated across varying feed flow rates and membrane flow conductances to ensure that decoupling is maintained beyond the defined operating point. This work concludes that the location of the actuators affects the degree of decoupling significantly and to achieve the maximum degree of decoupling, different actuators must be selected across a variety of operating condition.