Technoeconomic analysis of once through long tube MSF process for high capacity desalination plants

• Barriers of increasing MSF evaporator capacity are solved.
• Five tube bundles, once through, and long tubes are the key components of process efficiency.
• Significant saving in the water tariff cost.
• Novel layout of MSF evaporator is proposed to reduce footprint up to 60%.

This work presents a technoeconomic comparison between once through long tube (MSF-OT-LT) with atmospheric deaerator, and brine recycle cross tube (MSF-BR-CT) evaporators. The process design and cost analysis of 30 MIGD MSF-OT-LT evaporator is presented.The process calculations showed that for the same performance ratio, the heat transfer area of MSF-OT-LT is 34% lower than that of MSF-BR evaporator. This is due to the flashing range increase and higher heat transfer coefficient of MSF-OT-LT configuration. The pumping power of the MSF-OT-LT is 40% lower than that of MSF-BR-CT evaporator. This is due to lower friction loss in the tubes and due to remove brine recycle pump. A novel configuration of MSF-OT-LT is proposed in which the stages are arranged in a triple deck. The footprint decreases up to 57% in the large size project of 150 MIGD.For a large size project of 150 MIGD capacity, the unit water cost of the MSF-OT-LT configuration is 36% lower than that of the MSF-BR-CT. It can be concluded from this study that the MSF-OT-LT evaporator is a viable option for large scale capacity and a reliable technology for poor quality and high salinity sea water.