multi stage flash distillation vs reverse osmosis an overview of sea water desalination processes | sea ...
Seawater desalination refers to any of several processes in which some salt and other minerals are removed from the water.More generally, salt can also refer to the removal of salt and minerals, such as desalination sites.The first unit of salt for the production of drinking water by adding heat from the sun or during combustion to evaporate purified water.This principle, but achieved through Moore, Ilex, highly integrated energy processes, continues to apply current technologies to salt based on thermal separation processes.(1) extracted from sea water;(Two) the separation method adopted;3) the type of energy used.(I) the process of removing water before the mainstream.(Ii) the process of removing salt from the mainstream, leaving the salt of the latter.Since sea salt is usually less than 4%, it seems easier to choose the process of removing salt from sea water instead of extracting the sea water first.However, due to technical constraints.So far, the process of removing water provides better performance and is therefore preferred.In particular, the appropriate design of the highly integrated power settings allows the production of fresh water at a relatively low energy consumption.In these processes, a certain separation is made from the phase change of the fresh water produced, usually in the form of steam, which usually notice the evaporation (or heating) due to the high temperature of liquid water evaporation, A lot of energy is needed.Today, two major types of seawater desalination processes used by thermal evaporation in the world, Multi-Effect Distillation (MED) and multi-stage flash rate (MSF) seawater desalination.In the seawater, the MSE in the room evaporates to flash and the pressure remains below the supply pressure steam.This causes the seawater to flash, resulting in steam generation and salt water cooling.The arrangement of the flashing stage in series with the pressure will be reduced, resulting in a large amount of steam, and then re-Condensed from a test tube.The condensation heat in the beam is used to warm up the feed flow of the seawater, thereby reducing the heat energy of the heated food to reach the highest salt water temperature, and the temperature at which the food enters the stage flashes first.Therefore, the only entrance to thermal energy is the heat in the salt water, and the heated sea water is still heated by low heatThe temperature of the pressure steam to the salt water above.The standard device requires the MSF average value of low pressure steam per 8-10 kg fraction of the product to be I kg.In the Mediterranean Sea, the evaporation outside the tribal spots is heated by a condensing steam engine inside the tube.The steam generated by the power is then used as the power steam in the next effect.It works under the pressure of the tower.Therefore, the boiling point is low.This arrangement of heat integration enables a very efficient process, resulting in a performance ratio of up to 10-The first effect is 12 kg of the steam per kilogram.Further improve the efficiency of the process.The MEL) unit can also be connected to the Yap.Recovery units.Hot steam compression (TVC), mechanical steam compression (MVC) are the most common systems.(Development in the medium termSteam pressure), then used as a steam mark for the first effect, in the absence of logic in the middle, the reflux ratio of the fraction increased by 15 to 16 kg per kilogramPressure Steam supplied from the ink of the discharge.VC 151 in all steam of the latter effect is directly compressed by a mechanical compressor and used as a power steam in the first effect.In this case, only electrical mechanical energy is used to drive the process.The other two processes for removing less important water vapor are humidifying saltThe process of decompression and membrane distillation.Both of these energy sources are covered in the relevant sections, highlighting their connection to renewable energy sources.It is also a possibility to produce chilled water details by removing heat from salt water.The energy demand is much lower than before, and the heat of water-ice fusion is much smaller than the healing of evaporation.However, both refrigeration cycle technology.The management of seawater desalination processes associated with today has hindered the economic success of this option.Other processes for the separation of fresh water and brine without phase change, or pressure-driven membrane separation processes.Reverse osmosis is the most widely accepted in these processes.E \ 'obtained by semi-separated fresh water \'These salts can be removed from iron salt water using equipment that can capture ion flow content, or by ion exchange membrane or ion exchange resin.In the first case, it is forced to cross the membrane and thus separate from the mainstream.In the second case (ion exchange) ions are trapped in the solid matrix of the resin.The first group consists of a transfer film process, which is separated by a selective film during the transfer film process.Using a Moley semi-permeable membrane, water can enter the penetration flux through the membrane.The salt was rejected.This is the case of reverse osmosis where the driving force of separation is the differential pressure between the surfaces of the same membrane.In contrast, ion exchange membranes were used during dialysis current.The positive or negative ions are allowed to pass through selectively.The driving force of the channels placed between the two electrodes on the surface of the outer channel cell is to replace the negative, cation membrane.Anion and precautions 1110VC flow through the positive electrode and negative electrode of the negative ion membrane and the positive ion membrane respectively.When an anion can be found, the negative ion membrane gives notice, is arrested and imprisoned in a Channel accumulated in a concentrated flow.Before the ions are attracted to stay at a very low salt content, on the other side of the river, resulting in dilution flow.The second group consists of a thermal process in which it is separated by adding or removing heat from purified water.It is usually evaporated in a brine vapor liquid to produce pure water.The steam is condensed and the heat of the cob is usually recycled to warm up the feed stream or the steam evaporates again.Most evaporation processes require not only heat, but also mechanical and electrical energy from circulating pumps and auxiliary power units.
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