Can't you extract fresh water from sea water? If it could, wouldn't that make water too scarce?

The cost of extracting fresh water from seawater is too expensive

Here are the extraction methods:

Simple:

Seawater distillation is the simplest method of desalination. Take seawater into the evaporation dish heated, above the defense plus condensation plate, collected from the condensation plate is fresh water, and the last residual salt in the evaporation dish is an important chemical raw material Oh.

Complicated:

Desalination

Contents:

There is a lot of salt in seawater. Is it possible to remove the salt from the vast ocean and extract fresh water? Desalination is a dream that mankind has pursued for centuries. As early as the era of the world's great voyages, the British royal family has offered a reward to solicit cost-effective desalination methods. To this day, although there are hundreds of desalination methods, the production of fresh water is also different flavors, but by the standard of cost-effective measurement, is still not satisfactory.

On the surface, desalination is very simple, as long as the salt in the salt water and fresh water can be separated. One of the simplest methods is distillation, in which the water is evaporated and the salt left behind, and then the water vapor is condensed into liquid fresh water. This process is similar to the gradual salting of seawater, except that it is fresh water that humans are trying to capture. Another method of desalination is freezing, which freezes seawater so that it freezes, and the salt is separated out as the liquid freshwater turns into solid ice. Both methods have drawbacks that are difficult to overcome. The distillation method consumes a great deal of energy and produces a great deal of potting scale in the apparatus, while on the contrary not much fresh water is obtained. This is a very uneconomical way. The freezing method likewise consumes much energy, and the fresh water obtained is poor in flavor and difficult to use.

In 1953, a new way to desalinate seawater was introduced: reverse osmosis. This method utilizes a semi-permeable membrane for the purpose of separating fresh water from salt. Under normal circumstances, the semi-permeable membrane allows the solvent in the solution to pass through, but does not allow the solute to pass through. Since seawater is high in salt, if a semi-permeable membrane is used to separate seawater from freshwater, the freshwater will diffuse through the semi-permeable membrane to the seawater side of the membrane, thus raising the level on the seawater side of the membrane until a certain height creates a pressure that stops the freshwater from diffusing over. This process is osmosis. If you do the opposite, to get fresh water, just apply pressure to the seawater in the semi-permeable membrane, it will cause the fresh water in the seawater to permeate outside the semi-permeable membrane, while the salt is blocked by the membrane in the seawater. This is the reverse osmosis method. The biggest advantage of the reverse osmosis method

is energy saving, the production of the same quality of fresh water, its energy consumption is only 1/40 of the distillation method. therefore, since 1974, the world's developed countries coincidentally will be the direction of the research of seawater desalination turned to reverse osmosis method.

In the emerging reverse osmosis research in the ascendant, the old distillation method also changed course, rejuvenated. Common sense tells us that water at room temperature and pressure to be heated to 100 ℃ before boiling, producing a large amount of water vapor. The traditional distillation method only considered the way to obtain water vapor by increasing the temperature, which consumes a lot of energy. The new method is to lower the air pressure, the properly heated seawater, into a man-made vacuum distillation chamber, the seawater in the fresh water will be in an instant rapid evaporation, all into water vapor. Many of these vacuum distillation chambers are connected together to form a large desalination plant. If the desalination plant is built together with a cogeneration plant, and the waste heat from the cogeneration plant is used to heat the seawater, the cost will be even lower.

Most of the world's large desalination plants now use the new distillation method. In West Asia's oil-rich countries, often the land is "rich in oil", but not a freshwater well. The reality that water is more expensive than oil, so that the desalination plant has sprung up in West Asia's coastline. 1983, West Asia's largest country, Saudi Arabia, in the port of Jeddah, the construction of 300,000 tons of fresh water daily production of seawater desalination plant; in another West Asian country, Kuwait, can now produce 1 million tons of fresh water every day. In the Persian Gulf coastal region, some countries' desalinated seawater has accounted for 80-90 percent of their freshwater use.

(Reverse osmosis can be used

If a pressure greater than the osmotic pressure is applied to an instance of a solution, the water in the solution passes through a semi-permeable membrane and flows to the pure water side, and the solute is retained on the solution side, an action known as reverse osmosis...)