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Desalination of sea water refers to any of several processes that remove some salt and other minerals from the water. More generally, the salt can also refer to remove salts and minerals, such as desalination ground.rnThe first units of the salt used for the production of drinking water by the evaporation of pure water through the addition of heat from the sun or from combustion processes. This principle, but implemented through the mole, Ilex, highly integrated energy processes, continue to apply current techniques for salt, which are based on thermal separation processes.rnIn general, the technology of salt can be classified into three criteria:
(1) extracted from sea water;
(2) The type of separation, which was adopted;rn3) The type of energy used.
(i) Processes in which water is removed before the mainstream. Thus the production of an unsaltedrn(ii) Processes, where the salts removed from the main stream, leaving the salt of the latter.rnSince sea salt is generally less than 4%, it may seem easier to choose processes where salts are removed from seawater, rather than extracting sea water first.rnHowever, due to technological limitations. So far, the processes that remove water gives better performance and therefore are preferred. In particular, the proper design of highly integrated power settings allows the production of fresh water, with relatively low energy consumption.rnAmong these processes, perform a certain separation from the phase change of the water produced fresh, usually in the form of steam, these processes usually noted that evaporation (or heat) process and requires a significant amount of energy due the high heat of evaporation of liquid water. Today, two main types of desalination processes used by thermal evaporation in the world, the Multiple Effect Distillation (MED) and Multi Stage Flash (MSF) desalination. In sea water evaporates MSE in the rooms to flash, the pressure is kept below the supply pressure steam.rnThis leads to a flash of sea water, causing steam generation and cooling brine remaining. An arrangement of flashing stages connected in series with the pressure decreases, the production of large amounts of steam, which then re-condensed out of a tube bundle. Condensation heat of condensation in the beam is used to preheat the feed stream of sea water and thus reduce the thermal energy for heating the food for its Top brine temperature, the temperature at which the Food enters the stage blinks first. Thus, the only entrance to the thermal energy is heat in brine, heated sea water, which is still heated by low-pressure steam to the temperature of the brine above. Standard units require an MSF average of I kg of low pressure steam for every 8 to 10 kg of distillate product.rnIn MED, the evaporation on the outside of a tribal brindle, which is heated with condensing steam engine inside the tubes. The vapors produced in power is then used as motive steam in the next effect. It works on the pressure of the tower. therefore, a low boiling point. Such arrangements of heat integration achieves a very efficient process, resulting in a ratio of performance up to 10-12 kg per kg of distillate motive steam into the first effect. To further improve the efficiency of the process. MEL) units can also be connected to Yap. Recovery units. Thermal Vapour Compression (TVC), mechanical vapor compression (MVC) are the most common systems. TVC front part of steam, the final effect is recompressed by a steam rejectorrn(Developed in the mid-vapor pressure), and then used as a vapor mark the first effect, increasing the ratio of return over 15 to 16 kg of distillate per kg lack of logic in the mid-pressure steam supplied from the ink) of the expulsion. VC 151 in all the steam of the latter effect is directly compressed by a mechanical compressor and used as motive steam in the first effect. In this case, only electrical mechanical) energy is used to power the process. Two other processes that remove water vapor of less importance are the salt of humidification-dehumidification and membrane distillation process. Both are described in the relevant chapters highlight its link with renewable energy.rnProduction of frozen water detail, through the removal of heat from a salt solution, is also a possibility. Energy requirements are much lower than in the previous case, the heat of fusion of water ice is much smaller than the healing of vaporization. However, both the technology of refrigeration cycles. And the desalination process management relevant to today prevents the successful implementation of this option econotnical.rnOther processes to perform the separation of fresh water from salt water without phase change, or how the processes of pressure driven membrane separation. Of these processes, reverse osmosis is the most widely accepted. E 'obtained from the separation of fresh water through semi-permeable membrane that allows the passage of water or salt, in turn, inhibits the flow in the permeaternThe salts can be removed from the iron salt water using devices capable of capturing the content of the ion flow, or by ion exchange membranes or ion exchange resins. In the first case ions are forced to pass through the membrane and thus separated from the mainstream. In the second case (Ion Exchange) ions are trapped in the solid matrix of resin. rnThe first group consists of the transfer membrane processes where the separation is done through selective membranes. Sharpen half permeable membranes are used, water can pass through the membrane into the permeate flux. While the salts are rejected.rnThis is the case of reverse osmosis, where the driving force for separation is a pressure difference between the faces of the same membrane. By contrast, in the process of dialysis Electra, ion exchange membranes are used. rnAllowing selective passage of positive or negative ions. The driving force for the passage of a very large difference in electrical potential between two electrodes placed on the cell surface of the outer channels is the replacement of anionic and cationic membranes. Anions and precautions 1110VC the positive and negative electrodes, respectively, which flows through the anionic and cationic membranes. When the anions can be found cationic and anionic membranes notices, are arrested and imprisoned in the channels where they accumulate in a concentrated flow. On the other side of the river before the ions are attracted to stay with a very low salt content, and therefore lead to diluting the flow.rnThe second group consists of thermal processes, where the separation occurs by the addition or removal of heat for the pure water from saline. Evaporation is usually taken to produce pure water in the salt water vapor liquid. The steam is condensed and the heat of condensation is usually recovered to preheat the feed stream or vapor to evaporate again. Most of the evaporation process needs not only heat but also mechanical and electrical energy for the circulation pumps and auxiliary power units.