Water desalination is a process where the soils, dissolved salts, and minerals are removed from seawater or brackish water. The end product is that it produces purified drinking water or water that is free of chemicals.
In water desalination there are two types of desalinations:
Thermal desalination uses heat and temperatures to evaporate and condense seawater into clean water. This is usually done by large machines in power houses and warehouses.
In addition to thermal desalination, there are also three different types of ways water can be desalinated:
1. Vapor compression
2. multi-effect distillation
3. multistage flash distillation
Vapor compression- It starts in a boiling chamber, in the compressor the steam is pressurized and this gives off heat to the tap water inside the boiling chamber. The water boils and creates more steam. Once the pressurized steam cools down and condensed it is then collected, this is the process of creating distilled water.
Multiple effect distillation is a low temperature thermal process of obtaining fresh water or clean water by boiling sea water in multiple stages. Each stage or sequence is maintained at a lower temperature than the last giving the seawater time to cool and the purify water to be collected as it goes along through each stage.
How is this done? The vapors from the first evaporators is condense in a second evaporator. Each of these evaporator in turn is acting as a heater. Why so many stages? Well the reason being is that sea water must be several degrees lower than the last condensing steam to produce clean water. therefore the sea water must be repeatedly evaporated and condensed because this creates a larger quantity of clean water with the given energy being used.
Multistage flash distillation- This process is similar to multiple effect distillation. It has an evaporator that consists of several stages and each stage is at a decreasing pressure. The sea water is overheated and the vapor is condensed into fresh water. The sea water goes through an inline steam heater and passes different stages in which some of the brine flashes into steam. It goes along until it reaches the last stage in which the last of the brine is gone to waste and the distilled water is traveled to the storage tanks.
The difference between multi-effect flash and multiple effect distillation is that multiple flash has a lower energy consumption and this reduces the costs of creating clean water.