Reverse Osmosis

Sudden flash effect by Distillation (MSF)

The desalination is obtained by distillation in evaporate water to steam which does not contain salts (these are volatile from 300º C): The steam then condenses on the inside or outside of the tubes of the installation. The desalted systems typically operate below the atmospheric pressure and therefore require a vacuum system (pumps or ejectors), apart from the removal of the air and non-condensable gasses. The use of flash camera evaporation allows a sudden (and therefore of irreversibility) prior to their subsequent condensation. Generally, the camera flash is located in the lower part of a capacitor of the steam generated in the lower chamber. Therefore, the recovery of heat necessary for evaporation is obtained thanks to the union of successive stages in cascade to different pressure, and is the minimum contribution required from the condensation of a steam of low or medium quality from a power generation plant. This evaporative process is the most widely used in the world, massive deployment especially in the Middle East. This is due to several reasons:

• Is especially valid when the quality of the raw water is not good (high salinity, temperature and contamination of the water provided).

• Its coupling with power plants to form cogeneration systems is very easy and allows a high degree of variability of operating ranges in both plants.

• Its toughness in the daily operation compared to other distillation processes is notorious.

• The ability of the MSF plants is much greater than other plants distilleries in virtue of the amount of stages connected in cascade of operation without problems. However, MSF plants have a serious drawback. Its specific consumption, defined as the amount of energy consumed to produce 1 m^3 of desalinated water, is among the highest in the processes studied. This consumption contribute to the heat consumption from the plant producing electricity, higher than other distillation processes due to the flash effect; and the power consumption due to the large number of required pumps for the flow of plant. In addition to its high cost of operation, its installation cost is not lower than other desalination processes.

By multiple effect distillation (MED)

In contrast to the MSF process by flash effect, in the multiple effect distillation (MED) evaporation occurs naturally in one side of the pipes of an exchanger taking advantage of the latent heat given off by the condensation of steam on the other side of the same.
A MED plant ( Multi-Effect Distillation) has several stages connected in series to different operating pressures, these effects have each successive time the lowest boiling point by the effects of such pressure.
This allows the feed water to experience multiple boils in the successive effects, without the need to resort to additional heat from the first effect. The salt water then transfers to the following effect to suffer a evaporation and the cycle repeats itself, using the steam generated in each effect.
Normally there are also cameras flash to evaporate a portion of the salt water, it moves to the next effect, due to its lower operating pressure. The first stage is fed by an external steam system spiraled, a-pressure turbine (or removing a condensation).
A final condenser picks up fresh water at the last stage by preheating the water input to the system. Therefore the plants also make up MED cogeneration systems like the MSF consuming a portion of energy for the production of electricity.
The multiple effect distillation is a process not only used for desalination. The capacity of this type of plants tends to be lower than the SPS (they rarely exceed 15,000 m^ 3/day) although this is more due to political reasons that operational: the larger MSF are installed in the Middle East and the largest MED are installed in the Caribbean Islands to supply water to these areas of high pressure from tourism. It is also true that the maximum number of effects connected in series is rarely more than 15, with the exception of the MED with multiple effects built into each one of them, arriving in this case to a total number of more than 50.
However, they have a better overall performance with respect to a SPS: the ratio of gain in the distillers of this type of plant you can get to 15 without any problem, thus reducing the consumption of this specific process with respect to a SPS plant with identical capabilities.
This is mainly due to the irreversibility associated to the separation process flash that appears in the SPS processes. In addition the power consumption is less than the MSF as it requires less circulation pumps in the absence of recirculation brine.
Aguasin distributes in Chile chemicals for the treatment of MED Equipment and MSF fouling products BELGARD ® and antifoam / Moisturizer BELITE ® of our represented BWA.

Thermal vapor Compression (TVC)

Compression of steam heat (TVC, Thermal vapor compression) gets the distilled water with the same process as a multiple effect distillation (MED), but uses a source of thermal energy different: these are the so-called thermal compressors (or thermal-compresors), that consume half steam pressure from the plant of electricity production (if we have a dual plant, but it would be a steam process obtained specifically for this) and that draws out part of the steam generated in the last stage at very low pressure, compressed further and giving rise to a steam-pressure intermediate to the previous suitable to be made to the 1st stage, which is the only thing that consumes energy in the process.

The performance of this type of plant is similar to the MED plants, however its desalination plant capacity may be significantly greater to afford greater adaptability of steam outlet of producing plants of the same. Many times they are considered the same process, but here will be treated individually, as energy consumption of the plant is done by a different team.