Clean fresh water is essential to sustain human life and is of paramount importance. However, freshwater shortage remains a global problem. More than 80 countries, primarily located in arid regions and accounting for approximately 60% of the world's land surface, currently experience shortages.

The total volume of water on Earth is approximately 1,400 million km³, of which only 2.5% (approximately 35 million km³) is freshwater. Seawater accounts for approximately 98% of the planet's water resources.

Given the scarcity of freshwater, desalination technology has become particularly important. This is confirmed by the fact that 15,900 desalination plants worldwide currently produce approximately 95 million m³ of freshwater per day [1].

Today, the main methods of desalination of salt water are the following:

1. Distillation

The efficiency of distillation evaporators is limited by scale formation in the hot brine circulation system. The energy consumption of a distillation desalination unit is approximately 24 kWh per 1 m³ of fresh water. Corrosion and scale formation on heat exchange equipment limit heat transfer and lead to even higher energy consumption. Therefore, the use of special anti-scale additives is necessary, which significantly increases desalination costs.

2. Reverse Osmosis

The "Achilles heel" of reverse osmosis technology is membrane fouling. Therefore, pre-treatment stages are necessary to extend the life of the membranes and maximize the efficiency of this method. The energy consumption of a desalination unit using reverse osmosis technology averages 6-9 kWh per 1 m³ of fresh water.

3. Ion Exchange

This method is based on the removal of cations and anions of salts from the liquid. A disadvantage of the ion exchange method is its relatively high reagent consumption. The cost-effectiveness of ion exchange for water desalination is typically limited to initial dissolved salt concentrations of 1.5–2.5 g/L, so ion exchange is not widely used for water desalination.

4. Electrodialysis

The electrodialysis process is used to desalinate water containing no more than 10 g/L of dissolved salts. The actual energy consumption of a desalinator is 7–15 kWh per 1 m³ of fresh water.

5. Freezing

Freezing is a simple, but energy-intensive, method of water desalination. Energy consumption reaches 68.5 kWh per 1 m³ of fresh water.


IMPORTANT!

Existing desalination technologies consume large amounts of energy and simultaneously produce a byproduct. This hypersaline byproduct (salinity of 55-350 g/L depending on the desalination method) is known as "brine." As of 2019, global brine production was approximately 142 million m³ per day [1]. Some desalination methods also require pre-treatment of the water using coagulants, biocides, biosulfate salts, acids, antiscalants, and corrosion inhibitors. The resulting brine, containing dissolved chemicals, is typically discharged back into water bodies after desalination, causing adverse environmental impacts:

increases water salinity in the receiving and mixing zone

increases bottom sediment salinity due to the high salinity of the brine, which is negatively buoyant

decreases oxygen solubility, and therefore, the dissolved oxygen content

formation of toxic compounds for aquatic organisms

increases water turbidity with increased suspended solids, which affects the depth of light penetration

mortality of marine flora and fauna due to exceeding the organisms' salinity tolerance, oxygen deficiency, and heavy metal and chemical poisoning

Dehydration of brine using vortex technology

Using our laboratory setup, we conducted an experiment with our vortex chamber aerodynamics to dehydrate brine from Norilsk Nickel mines. Dry salt and a steam-air mixture with the potential to produce freshwater condensate were obtained. Energy consumption was less than 5 kWh per 1 m³ of freshwater.

The aerodynamic vortex chamber is a device that ensures uniform distribution of the medium around the chamber's periphery and in which the fluid rotates, thereby promoting the formation of a vortex flow. A rotor, driven by the airflow, rotates within the chamber at an angular velocity of ω = 387 rad/s. Saltwater is injected into the chamber under pressure and, due to the rotor's rotation, is instantly pressed against its inner surface. Water particles in the vortex chamber rotate at the rotor's speed and experience a very high centrifugal acceleration of a = 29,600 m/s². This force field allows them to be kept in the vortex chamber for as long as necessary to complete the thermodynamic processes.

Advantages of an aerodynamic vortex chamber for desalination of brine solutions:

1. The result is dry salt and fresh water. Vortex technology on the brine solution allows for the production of pure salt, something no other desalination technology can achieve.

2. The concentration of the initial brine solution is irrelevant to the operation of our system.

3. No brine formation! Environmentally friendly!

4. No need for filters or other consumables.

5. Low energy consumption.


1. Edward Jones, Manzoor Qadir. The state of desalination and brine production: A global outlook. - Science of the Total Environment 657 (2019)