Process control in multi-stage flash desalination industry

Process control is an essential part of the desalination industry that requires to be operated under optimum conditions to increase the lifetime of the plant and reduce the unit product cost. Improved process control is a cost-effective approach to energy conservation and increased process profitability. The Multi-Stage Flash (MSF) plant involves many complicated operations related to steam, chemicals and seawater. These include variable capacity, slow dynamics, deadtime characteristics due to certain load changes, significant effects of small deviations from design conditions on plant operation, effects of power plant output conditions on the desalination plant, instability due to disturbances in steam supply and water temperature variations. Keeping in view the above criticalities, the selection of an effective control system becomes inevitable. This paper aims at identifying various types of control loop available in an MSF plant, selection of control elements, type of control strategy needed for it and integrating the whole system for supervisory control.