What is distillation?

Simple: Seawater distillation is the simplest method of desalination.

Take seawater and heat it in an evaporating dish. Add a condensing plate on top. What is collected from the condensing plate is fresh water, and the salt remaining in the evaporating dish is an important chemical raw material.

Complex: Desalination Contents: Seawater contains large amounts of salt.

Is it possible to remove salt from the vast ocean and extract fresh water?

Desalination of seawater is a dream that humans have pursued for hundreds of years.

As early as the age of world navigation, the British royal family offered rewards for cost-effective seawater desalination methods.

Today, although there are hundreds of methods for desalinating seawater, and the fresh water produced has different flavors, they are still unsatisfactory when measured by economical and cost-effective standards.

On the surface, desalination is simple, just separating the salt in salt water from the fresh water.

The simplest method is distillation, which evaporates the water and leaves the salt behind, and then condenses the water vapor into liquid fresh water.

This process is similar to the process of seawater gradually becoming salty, except that humans are grabbing fresh water.

Another method of desalination is freezing, which freezes seawater and freezes it. The salt is separated while the liquid fresh water turns into solid ice.

Both methods have drawbacks that are difficult to overcome.

The distillation method consumes a lot of energy and produces a lot of scale in the equipment, but does not produce much fresh water.

This is a very uneconomical way.

The freezing method also consumes a lot of energy, but the fresh water obtained does not taste good and is difficult to use.

In 1953, a new method of desalination was introduced, which was the reverse osmosis method.

This method uses a semipermeable membrane to separate fresh water from salt.

Under normal circumstances, a semipermeable membrane allows the solvent in the solution to pass through but does not allow the solute to pass through.

Since seawater contains high salt content, if a semipermeable membrane is used to separate seawater from fresh water, the freshwater will diffuse to one side of the seawater through the semipermeable membrane, causing the liquid level on the seawater side to rise until a certain height generates pressure, causing the

Fresh water no longer spreads through.

This process is osmosis.

If the opposite is done, to obtain fresh water, as long as pressure is applied to the seawater in the semipermeable membrane, the freshwater in the seawater will penetrate out of the semipermeable membrane, while the salt will be blocked by the membrane in the seawater.

This is the reverse osmosis method.

The biggest advantage of the reverse osmosis method is energy saving. It can produce fresh water of the same quality, and its energy consumption is only 1/40 of the distillation method.

Therefore, since 1974, developed countries in the world have invariably shifted their research direction of seawater desalination to reverse osmosis.

While research on the emerging reverse osmosis method is in its ascendant, the ancient distillation method has also changed its course and been rejuvenated.

Common sense tells us that water needs to be heated to 100°C under normal temperature and pressure before boiling, producing a large amount of water vapor.

The traditional distillation method only considers the method of obtaining water vapor by raising the temperature, which consumes a lot of energy.

The new method is to lower the air pressure and send appropriately heated seawater into an artificial vacuum distillation chamber. The fresh water in the seawater will evaporate rapidly in an instant and turn all into water vapor.

Many of these vacuum distillation chambers are connected to form a large desalination plant.

If the desalination plant is built together with a thermal power plant and the waste heat from the thermal power plant is used to heat seawater, the cost will be even lower.

Most of the world's large-scale seawater desalination plants now use new distillation methods.

In oil-rich countries in West Asia, the land is often "rich with oil" but cannot drill a single fresh water well.

The reality that water is more expensive than oil has led to desalination plants popping up along the coastlines of West Asia.

In 1983, Saudi Arabia, the largest country in West Asia, built a desalination plant with a daily output of 300,000 tons of fresh water at the Port of Jeddah; in Kuwait, another West Asian country, it can now produce 1 million tons of fresh water every day.

In the coastal areas of the Persian Gulf, in some countries, desalinated seawater accounts for 80% to 90% of the country's freshwater usage.