Performance analysis of operating multi-stage flash distillation unit coupled with nuclear power plant

Multi-stage flash (MSF) process is the most widely used technology in large scale desalination plants which utilizes low quality steam produced in nuclear power plant. The objective of this study is to analyze the performance of brine heater used in 4,500 m3/d capacity MSF desalination plant at Nuclear Desalination Demonstration Plant (NDDP), Kalpakkam commissioned in 2008. The efficiency of brine heater, after 12 y of service, was investigated by analyzing the influence of volumetric flow rate and scale thickness on heat transfer rate. The tube side pressure drop increases steeply as a function of volumetric flow rate of cold fluid. A maximum pressure drop of 17.1 kPa was developed at an optimized flow rate of 1,500 m3/h. The overall heat transfer coefficient increases gradually as scale thickness decreases and reached an ultimate of 4,395.3 W/m2 K at a scale thickness of 0.00005 m. For small scale thickness, the percentage reduction in overall heat transfer coefficient increased steeply and attained a saturation limit at 0.00025 m scale thickness. The overall heat transfer coefficient increased from 623.4 to 646.3 W/m2K as the volumetric flow rate increased from 750 to 1,500 m3/h. This study shows that the thermal efficiency of brine heater has not declined significantly after prolonged years of service under different operating conditions.