Desalination plants cause sea and brackish water to become separated, according to howstuffworks.com/. Next, the the separation of the of the sea and brackish water will lead to two different flows. One of the flows will consist of a fresh stream, which is condensate in heat processes and permeated in reverse osmosis. Also, the fresh stream will be required to have a low salt content. The other flow will basically consist of concentrate or brine, which means it will have an extraordinarily high level of salt concentration.
All desalination technologies have to operate off of a powerful energy source. The energy sources either come from mechanics, which use electrical power, or they will use thermal power. The thermal process is founded on evaporation caused by the heat, and then, it uses the condensation from the steam. If you want to understand the intricacies of thermal desalination, you have to understand the methods. The following four tips to understanding thermal desalination are also the four methods simplified.
MED, also known as multi effect distillation, takes place through a series of stages or effects. Every stage is equipped with bundles of heat exchange pipes, which are made super hot from steam heating on the inside. When the pipe bundles are hot, the raw water is sprayed on them. Due to the heat transfer between the pipe walls, a portion of the liquid sprayed on the bundles evaporates. The evaporation results in steam, and the new steam is used in the next stage. This is how the process continues. Essentially, the first tip is understanding steam and condensation.
This method is similar to MED in almost all aspects. Efficiency is enhanced over regular MED in this method by putting a thermal steam compressor in the MED plant. The same process is used in the MED process by letting water evaporate into steam and using the resulting steam in the next process and so on. The difference is the thermal steam compressor, which is also powered by steam, uses steam from the final stage for more compression. The super-condensed steam is reused at a heat source when the process is started over. Like before, the tip is under standing the basics of steam, but additionally, it requires knowing how to compress steam to understand the process better.
This process and the tip are much easier to understand. MVC is mechanical steam compression. According to Wabag, it is almost identical to the MED-TVC process, except the steam used for evaporation is achieved through electricity or diesel power. The best analogy for this is to think of using either an electric or gas stove to get water hot enough to create steam.
This stage is also known as the multi stage flash. The tip to understanding this thermal process is understanding how distillation works. Condensing steam heats the raw water up to the max brine temperature. It turns it into saline, and the saline solution goes into the next stage where the pressure is lower. The water will boil immediately, which causes it to flash into steam and the brine to reach its saturation point. Each stage afterwards, the temp and pressure are lowered. The steam at the end of each stage is fresh water.
Basically, the foundation of each method is very basic science and processes. The only difference is, is they are expanded upon and the processes are done at huge levels. It is worth it though. As thermal desalination technology gets better and cheaper, it will eventually utilize the oceans and salty sea water to irrigate the planet.