(270a) Optimization of Seawater Cooling in Power Plants

ABSTRACT Seawater cooling is a common practice in regions with scarce resources of fresh water. Power plants require significant levels of seawater cooling. There two main problems of using seawater in cooling systems. Seawater stimulates the growth of biofouling which reduces the extent of heat transfer. Furthermore, chemical biocides are used to treat seawater in the cooling system to prevent biofilm development. The remaining biocides in the discharged seawater can be very harmful to the aquatic life and can cause serious health problems. Nonetheless, it is essential to maintain the concentration of chemicals at a certain level to ensure control over biofouling development. It is important to maintain a balance between treating the seawater to satisfy the process requirements while considering the environmental and economic implications of such treatment. Some power plants operate in conjuction with a desalination facilities in order to produce drinking water and electricity. This kind of hybrid systems is economically feasible in countries that have high demand for drinking water as well as for power. This work focuses on solving the problem of finding the optimal balance between treating seawater with the right chemicals and dosing scenarios while complying with process requirements. Also, water in the cooling system may be treated prior to discharge to avoid further damages to the aquatic life after the discharge. Furthermore, the demand for electric power and water vary seasonally. To address this complex problem, we develop a multi-period optimization problem for the optimal design and operation of seawater cooling systems in power plants. The developed formulation addresses the question of how should the biocide dosage be varied over time to account for the seasonal variations in demand and in seawater temperature. Furthermore, the reaction mechanism and kinetics of the biocide in seawater are used to estimate the growth of biofilm and the residual biocide in the discharged seawater. A case study is solved to demonstrate the effectiveness and applicability of the devised approach.