Fresh water is increasingly becoming a scarce resource in the world. An increase in its amount will be highly required in the future. This is due to the resultant increasing in the population, enhanced living standards and expansions experienced in the industrial sector and agricultural activities. Seawater technologies help in reducing the shortage of this vital resource.
Marine water comprises a whole 97% of the aqua storage on earth. This is followed by the glaciers which make up only 2% of the summation. Surprisingly only 0.5% is the one available for humanity use. This is sourced from inland aqua bodies. Sea aqua being not suitable for domestic and industrial human use has made desalination quite a vital means of providing another source of fresh water.
The desalination process involves separation of the resource into two streams. A fresh stream containing a low concentration of dissolved salts and a concentrated brime stream. The above process requires some form of energy to desalinate and several different technologies are utilized. Over the years a variety of innovations have been developed on the basis of thermal distillation, membrane separation, freezing, electro dialysis, etc. On commercial basis the two most important technologies are based on the MSF and RO technologies although it is viewed that the two processes together with MED (multiple effect distillation) will be dominant and competitive in the future.
So what are some of the technologies used? Multiple-stage flash distillation is one of them. This one is based on the principle of flash evaporation. The resource is evaporated by reducing the pressure as opposed to raising temperature. The economies of the MSF heating technology are achieved by regenerative heating where the sea water flashing in each flash chamber or stage gives up some of its heat to its counterpart going through the flashing process.
Multiple effect distillation is the form of distillation process. And is also thermodynamically efficient. The process takes place in a series of evaporators called effects and uses the principle of reducing the ambient pressure in the various effects. The MED plant steam economy is proportional to the number of effects. MED plants can have 3 types of tubes, that is, horizontal, vertical or submerged. Most recent application have been in the Middle East. Although their number is still relatively small compared to MSF plants, their numbers have been increasing.
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.
Reverse osmosis, commonly referred to as RO, is where the osmotic pressure is overcome by applying external pressure higher than the osmotic pressure on the sea water. Thus it flows in the reverse direction to the natural flow across the membrane leaving the dissolved salts behind with an increase in salt concentration. Over the past decade a number of developments have been made to help reduce the operating cost of RO plants. These are the development of membranes that can operate efficiently with longer duration and the use of energy recover devices.
These are not the only technologies in use. But the most commonly used ways of desalination as compared to the one mentioned above. We have others such as freezing, potabilization and solar evaporation.
Marine water comprises a whole 97% of the aqua storage on earth. This is followed by the glaciers which make up only 2% of the summation. Surprisingly only 0.5% is the one available for humanity use. This is sourced from inland aqua bodies. Sea aqua being not suitable for domestic and industrial human use has made desalination quite a vital means of providing another source of fresh water.
The desalination process involves separation of the resource into two streams. A fresh stream containing a low concentration of dissolved salts and a concentrated brime stream. The above process requires some form of energy to desalinate and several different technologies are utilized. Over the years a variety of innovations have been developed on the basis of thermal distillation, membrane separation, freezing, electro dialysis, etc. On commercial basis the two most important technologies are based on the MSF and RO technologies although it is viewed that the two processes together with MED (multiple effect distillation) will be dominant and competitive in the future.
So what are some of the technologies used? Multiple-stage flash distillation is one of them. This one is based on the principle of flash evaporation. The resource is evaporated by reducing the pressure as opposed to raising temperature. The economies of the MSF heating technology are achieved by regenerative heating where the sea water flashing in each flash chamber or stage gives up some of its heat to its counterpart going through the flashing process.
Multiple effect distillation is the form of distillation process. And is also thermodynamically efficient. The process takes place in a series of evaporators called effects and uses the principle of reducing the ambient pressure in the various effects. The MED plant steam economy is proportional to the number of effects. MED plants can have 3 types of tubes, that is, horizontal, vertical or submerged. Most recent application have been in the Middle East. Although their number is still relatively small compared to MSF plants, their numbers have been increasing.
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.
Reverse osmosis, commonly referred to as RO, is where the osmotic pressure is overcome by applying external pressure higher than the osmotic pressure on the sea water. Thus it flows in the reverse direction to the natural flow across the membrane leaving the dissolved salts behind with an increase in salt concentration. Over the past decade a number of developments have been made to help reduce the operating cost of RO plants. These are the development of membranes that can operate efficiently with longer duration and the use of energy recover devices.
These are not the only technologies in use. But the most commonly used ways of desalination as compared to the one mentioned above. We have others such as freezing, potabilization and solar evaporation.
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