Seawater desalination of principles and modes
There is a lot of salt in the sea water. Can we remove salt from the vast ocean and extract fresh water? Desalination has been a dream of mankind for hundreds of years. As early as the era of world navigation, the British royal family had offered a reward for economical desalination methods. Up to now, although there are hundreds of desalination methods and the fresh water produced has different flavors, it is still unsatisfactory in terms of economic standards.
On the surface, desalination is very simple, as long as the salt in salt water is separated from fresh water. One is distillation, which evaporates water and leaves salt, and then condenses water vapor into liquid fresh water. This process is similar to the gradual salting of seawater, except that fresh water is what humans want to grab. Another desalination method is the freezing method, which freezes the sea water and freezes it. While the liquid freshwater becomes solid ice, the salt is separated. Both methods have insurmountable disadvantages. Distillation consumes a large amount of energy and produces a large amount of scale in the instrument. On the contrary, there is not much fresh water. This is a very inexpensive way. The refrigeration process also consumes a lot of energy, but the fresh water obtained is not tasty and difficult to use.
Next, introduce the vacuum pump used in seawater desalination.
Liquid Ring Vacuum Pump as Seawater Desalination System of Application and Advantage
Everyone is paying attention to low-carbon life, and the most cost-saving low-carbon life is to use the existing resources of nature for integrated utilization, such as solar energy, wind energy, biological energy and geothermal energy, such as the use of wind power, the use of solar energy to generate heat or desalination, which not only saves costs, but also greatly reduces land use. The pressure of the ball makes a great contribution to environmental protection.
Solar desalination is an effective way to solve the shortage of freshwater resources in China. There are many methods of solar desalination. In order to reduce the evaporation temperature of seawater, vacuum pump is usually used to realize negative pressure evaporation, which can reduce the boiling evaporation temperature of seawater. The function of vacuum pump can also change the flow direction of water vapor. It is conducive to heat transfer and condensation. Therefore, the vacuum pump plays a vital role in the desalination system. Its working performance has a great impact on the whole desalination system. Therefore, it is required that the vacuum pump has reliable performance, stable operation, low energy consumption, can produce a larger vacuum, and has sufficient pumping rate.
At present, the main vacuum pumps used in seawater desalination are water jet vacuum pumps and liquid ring vacuum pumps. The working principle of water jet vacuum pumps is to use high-speed water flow generated by pressure difference to extract gas, which has the characteristics of simple structure and can extract condensate gas such as water vapor, but its efficiency is low and power consumption is high. The liquid ring vacuum pump relies on the eccentric impeller in the pump shell to rotate and throw water into the pump shell to form a concentric water ring with the pump shell. The water ring and the rotor blade form a periodic volume change so that the gas can be inhaled, compressed and discharged. The advantage of the liquid ring vacuum pump is that at high vacuum, the pumping speed is higher, the condensate gas such as water vapor can be pumped, and the water jet vacuum can be achieved. Compared with its low power consumption, high efficiency and compact structure, the vacuum produced by the pump can meet the requirements of seawater desalination, so the liquid ring vacuum pump is more suitable for negative pressure seawater desalination system.
The liquid-ring vacuum pump is applied to solar desalination system, and a new type of solar desalination device is put forward. Through the experimental study on the working performance of the liquid-ring real pump, the variation law between the vacuum degree and the pumping speed of the system is obtained, which can match the performance of the desalination system and the vacuum pump and determine the operational parameters. It lays a theoretical foundation.