Engineering design approaches towards reducing the power consumption of the coastal power plant’s residual heat based desalination plant

Coastal power plant condenser’s reject heat based Low Temperature Thermal Desalination (LTTD) plants exploit only 9 °C thermal gradient available between the power plant condenser’s reject seawater and surface seawater for distillation, hence requiring large quantities of seawater. The consequence of this high seawater flow rate is the liberation of more Non Condensable Gases in the flash chamber which results in the escape of uncondensed water vapour from the distillate condenser leading to an increase in the vacuum load of the plant. This study investigates the influence of the tube pass and tube diameter of the distillate condenser, the influence of introducing a de-aerator, and the influence of introducing a Direct Contact Condenser (DCC) in the plant using HTRI software. The study results show that 17 mm outer diameter tubes with single pass condenser is the better option as it results in smaller shell diameter with a 58 % reduction in the total cost of the condenser, 40 % desorption efficiency in de-aerator reduce the vacuum load by 31.7 % and introduction of DCC with 0.05 kPa pressure drop further reduces the vacuum load by 54.6 %. Hence total reduction in the vacuum load is 69 % in the main vacuum system of the LTTD plant. • The effect of using DCC as the post condenser on Coastal power plant’s residual heat based desalination plant is presented. • Influence of de-aerator efficiency on the distillate condenser’s performance in the plant is investigated. • Distillate condenser cost and cold seawater pumping power of the plant are investigated.