Water is life

MED - Multi-effect desalination Process Steam is passing inside the tubes and cold sea water flowing outside the tubes, steam condenses as distillate (freshwater) inside the tubes passing through series of cells During this process sea water warm up and partially evaporate as well as recovering the heat (latent heat). Seawater due to evaporation getting concentrated flowing down to the bottom where vapor raised at a lower temperature than the heating system. But still it is being used as heating media for the next effect to repeat the process, the decreasing pressure allows brine and distillate to pass to the next cell for flashing producing additional vapors which condense into distillate in the next cell. Repeating the same process in a series of effects called Multiple Effect Distillation. In the last cell where steam condenses on a shell and tubes heat exchanger acting as distillate condenser which is cooled by sea water. At the outset of the condenser, some of the warm sea ...

Detail of MSF system The efficiency and performance of MSF plants very much depend on the formation of scales in heat transfer areas. As soon as the scale deposition starts the heat exchange rate begins reducing demanding more heat to achieve the desired temperature or otherwise reduce the production also the rate of condensation reduced due to less cooling of the heat exchange surfaces The scale mainly consists of the constituents present in the sea water that is calcium, magnesium, bicarbonate, and sulfates. When water temperature increase bicarbonates convert into carbonate and combined with calcium to form calcium carbonate and precipitated when the concentration exceeds the saturation limits. Magnesium hydroxide (alkaline scale) also forms during this process which can be controlled by reduction of pH decomposing some bicarbonates reducing the saturation limits of calcium carbonate to reduce its precipitation. This precipitation can also be controlled by some special chem...