Exatem
Guest
in this debate http://www.cad3d.it/forum1/showthread.php?36929-star-wars we mentioned the production of fresh water on board the ships. the ship contains numerous plants, both for production and for disposal and it is often complex plants (think of a passenger ship with a few thousand people who eat, drink and produce waste of all kinds.
I therefore thought to describe the functioning of some of them starting precisely from the production of fresh water.
water production plantsfresh water is produced on board the ships, for the most different uses: steam production, lavender water and for hygienic uses, drinking water, rockets in cooling circuits and air conditioning. production plants are divided into two main categories: Dissalators and distillers. in practice the different types of plants for the production of fresh water differ because they act by exploiting the phenomenon of osmosis (inverse osmosis plants) or by means of a heat process of evaporation and subsequent condensation (evaporation plants).
the dissalators lower the total content of dissolved salts in the sea water so as to allow the use of water so produced as lavender water, possibly as drinking water after appropriate treatment and finally, as reserve water for the requirements of the motor apparatus.
given the characteristics of the water produced by means of desalination plants this is not suitable as food water for naval propulsion or auxiliary boilers for which these plants are mainly used on units with endothermic motor devices (diesel,tag etc.).
distillers produce fresh water through the evaporation of sea water and subsequent condensation of steam and consist of two parts: a evaporator, in which salt water enters which heats up to obtain steam, and a capacitor in which the steam condenses in distillate.
once the sea water was heated through a tube beam placed inside the evaporation chamber (tuber bundle evaporators). Then it went to evaporators called “flash” in which salt water is first heated and then put into the evaporation chamber where it finds a lower pressure of the steam voltage obtaining an immediate evaporation. this solution has the advantage of lowering maintenance costs resulting in the formation of limestone deposits on the pipes. flash evaporators are often made with multiple standard evaporation chambers on the salt water circuit (fall evaporators), each at a lower pressure than the previous one, so as to increase the amount of evaporated water.
in both solutions, the evaporation chamber is maintained at a lower pressure than that environment by usually allowing the evaporation to 60 °C (low pressure evaporators) and for this reason, it usually takes advantage of the heat of the cooling water of the engines to feed the heating coils, this method allows in fact to elevate the temperature of the sea water to about 60 °C even if the evaporation occurs at low temperatures, such a guarantee for this reason it is forbidden to evaporate in port and it is not advisable to do so in coastal waters especially if the production is sent to the deposits of lavender water.
the production of steam produces a liquid residue with a high concentration of salinity called brine: in a modern plant is produced almost a liter of distilled water for each liter of sea water.
the dissalators instead exploit the phenomenon of reverse osmosis and are very used on board the ships since, in the face of a greater cost, they have greater reliability and need a limited number of auxiliary equipment.
These systems exploit a principle for which when two saline solutions in water having different concentration are put into contact through a semi-permeable membrane that does not allow the larger molecules to pass, water tends to pass into the most concentrated solution by diluting it.
the process goes on until the difference of pressure on the two faces of the membrane, consisting of sheets of polyamide or other materials of poor mechanical resistance supported by plastic support networks, reaches a specific value for that solution, called osmotic pressure, which for sea water is about 7.0 kpa every 100 mg/l of salts in solution. to increase the production of a plant are put in parallel several cartridges and to improve the quality of the distillate they can be put in series regarding the flow of sea water. the advantages that reverse osmosis dissalators have towards conventional distillers are mainly:
- possibility of directly producing drinking water, more suitable for food and lavender use than distilled water.
- functional autonomy
- low energy use
- possibility of using extremely simple plants such as conduct and maintenance.
to obtain drinking water, the simplest plants are usually sufficient or those with a single desalination stage.
in any case, whatever the plant, the water obtained must contain a low content of salts. a good evaporation distiller lowers this amount to some units, while a reverse osmosis distiller leaves higher traces, but always less than those imposed by the oms (although the quality of the plants is continuously improved).
I therefore thought to describe the functioning of some of them starting precisely from the production of fresh water.
water production plantsfresh water is produced on board the ships, for the most different uses: steam production, lavender water and for hygienic uses, drinking water, rockets in cooling circuits and air conditioning. production plants are divided into two main categories: Dissalators and distillers. in practice the different types of plants for the production of fresh water differ because they act by exploiting the phenomenon of osmosis (inverse osmosis plants) or by means of a heat process of evaporation and subsequent condensation (evaporation plants).
the dissalators lower the total content of dissolved salts in the sea water so as to allow the use of water so produced as lavender water, possibly as drinking water after appropriate treatment and finally, as reserve water for the requirements of the motor apparatus.
given the characteristics of the water produced by means of desalination plants this is not suitable as food water for naval propulsion or auxiliary boilers for which these plants are mainly used on units with endothermic motor devices (diesel,tag etc.).
distillers produce fresh water through the evaporation of sea water and subsequent condensation of steam and consist of two parts: a evaporator, in which salt water enters which heats up to obtain steam, and a capacitor in which the steam condenses in distillate.
once the sea water was heated through a tube beam placed inside the evaporation chamber (tuber bundle evaporators). Then it went to evaporators called “flash” in which salt water is first heated and then put into the evaporation chamber where it finds a lower pressure of the steam voltage obtaining an immediate evaporation. this solution has the advantage of lowering maintenance costs resulting in the formation of limestone deposits on the pipes. flash evaporators are often made with multiple standard evaporation chambers on the salt water circuit (fall evaporators), each at a lower pressure than the previous one, so as to increase the amount of evaporated water.
in both solutions, the evaporation chamber is maintained at a lower pressure than that environment by usually allowing the evaporation to 60 °C (low pressure evaporators) and for this reason, it usually takes advantage of the heat of the cooling water of the engines to feed the heating coils, this method allows in fact to elevate the temperature of the sea water to about 60 °C even if the evaporation occurs at low temperatures, such a guarantee for this reason it is forbidden to evaporate in port and it is not advisable to do so in coastal waters especially if the production is sent to the deposits of lavender water.
the production of steam produces a liquid residue with a high concentration of salinity called brine: in a modern plant is produced almost a liter of distilled water for each liter of sea water.
the dissalators instead exploit the phenomenon of reverse osmosis and are very used on board the ships since, in the face of a greater cost, they have greater reliability and need a limited number of auxiliary equipment.
These systems exploit a principle for which when two saline solutions in water having different concentration are put into contact through a semi-permeable membrane that does not allow the larger molecules to pass, water tends to pass into the most concentrated solution by diluting it.
the process goes on until the difference of pressure on the two faces of the membrane, consisting of sheets of polyamide or other materials of poor mechanical resistance supported by plastic support networks, reaches a specific value for that solution, called osmotic pressure, which for sea water is about 7.0 kpa every 100 mg/l of salts in solution. to increase the production of a plant are put in parallel several cartridges and to improve the quality of the distillate they can be put in series regarding the flow of sea water. the advantages that reverse osmosis dissalators have towards conventional distillers are mainly:
- possibility of directly producing drinking water, more suitable for food and lavender use than distilled water.
- functional autonomy
- low energy use
- possibility of using extremely simple plants such as conduct and maintenance.
to obtain drinking water, the simplest plants are usually sufficient or those with a single desalination stage.
in any case, whatever the plant, the water obtained must contain a low content of salts. a good evaporation distiller lowers this amount to some units, while a reverse osmosis distiller leaves higher traces, but always less than those imposed by the oms (although the quality of the plants is continuously improved).
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