Sabtu, 21 Maret 2015

The Diverse Forms Of Seawater Technologies

By Lelia Hall


For the survival of humans, animals industries and agricultural sector, fresh water has always been a vital commodity. With the increase in each of the above factors makes an increase in its supply in the future important. As it is becoming a scarce commodity. There are various seawater technologies that have come up which aided significantly in achieving the objective.

97% of earth aqua reservoir is marine. While another 2% is locked in ice caps and glaciers. Only less than 0.5% of the earth total supply is available. These are supply from rivers, lakes and underground reservoir. Sea water is not suitable for human consumption and for industrial or agricultural purposes. Removing salt from the unlimited supply of this resource, desalination has emerged as an important source of fresh water.

The process comprises division of the commodity into two. Fresh stream containing little concentration of salts dissolved while the other is heavily concentrated brime. Forms of energy are required for the above process and there by different inventions are being used. Various technologies have come up based on different platforms such as freezing, electro dialysis etc. But the two mostly used and have a promising future are the MSF and RO. Together with MED, they are predicted to be the dominant methods in future.

Multiple stage flash distillation. One of the methods of desalination. It is built on flash evaporation principle. Where evaporation is induced by reduction of pressure instead of increasing of temperature. Its economic advantage is through the regenerative heating. Where the resource gives up its heat to its counterpart on every flash chamber it goes through.

Another method based on distillation is multiple effect distillation. Considered to thermodynamically efficient. It involves the sea water being undertaken through effects, these are a chain of evaporators. The effects use the law of reduction of pressure. Its economic efficiency is determined by the number of effects. This technology has been recently applied in the Arabian region but in comparison to its counterpart MSF it is still not very utilized although it is rising steadily.

Another technology used is the vapor compression distillation. Here the heating of marine aqua comes from the compression of vapor. The vcd plant takes advantage of principle of reducing the boiling point temperature by reducing pressure. Two methods are used to condense vapor, a mechanical compressor that helps to produce enough heat to vaporize incoming sea water and a steam jet that works the same. This process is normally used for small scale desalination units.

There is also the method of Reverse Osmosis (RO). Where external pressure, more than the osmotic pressure of the marine water, is applied thereby overcoming the osmotic pressure. Therefore leaving behind dissolved salts with the increase in their concentration. In the recent past various developments have emerged to assist in reducing operating cost of the RO plants.

There are many other innovations being used in desalination. Others include freezing, solar evaporation and potabilization. But they tend not to be commonly used as compared to the rest.




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