Optimal operations for large-scale seawater reverse osmosis networks

Optimal operation of large-scale seawater reverse osmosis (SWRO) systems, which include multiple RO plants and storage tanks, are studied to reduce the energy cost; and at the same an effective computing method was introduced for the purpose of real time optimization. With well developed models of the RO process and storage tanks based on the first principle, the optimal operation problem is subsequently formulated in the form of differential-algebraic optimization problems (DAOPs). Simultaneous collocation method was used to transform the problem into a large-scale nonlinear programming problem, and then IPOPT solver, combined with an efficient initial-value and finite-element meshing technique, was used for fast solution. Then the optimal operation problem with different variable parameters that significantly affect the performance and the energy saving of the SWRO system were investigated through case studies. Computational results show that the optimal operation problem under different conditions can be solved with high efficiency and stability, and significant energy-saving potential can be obtained through the optimal operation proposed in this paper.