Effect of feed water temperature on the performance and economics of thermal energy driven multiple effect distillation system for water treatment

Abstract

This study presents the design, fabrication, and experimental analysis of Multiple Effect Distillation (MED) plant with four effects (4+C system). A total of 15 experiments were conducted, systematically categorized based on feed water temperature. Baby fire tube boiler producing 25 kg/h steam were installed with plant for experimental study. The investigation focused on distillate output, Gain Output Ratio, Overall Heat Transfer Coefficient, and the cost of distillate. Investigation demonstrates a notable increase in distillate output and Gain Output Ratio as the feed water temperature increases. Furthermore, improvements in the Overall Heat Transfer Coefficient with higher temperatures was observed. Notably, the cost of distillate decreased from $2.5/m³ to $1.5/m³ as the temperature increased. Findings suggest that 80 °C feed water temperature optimizes distillate output and Gain Output Ratio. Beyond this temperature, a decrease in distillate production occurs due to reduced latent heat of vaporization. The economic analysis reveals a trade-off between distillate output and cost, emphasizing the importance of optimizing feed water temperature. The inlet temperature was maintained at 115 ± 0.3 °C, while the boiler pressure remained at 5 bar. In the pilot plant configuration, MED system operating at 80 °C generated a daily water output of 438.93 L/day. The associated cost for producing fresh water was1.65 $/m3, and the system achieved a maximum Gain output ratio of 1.95.