Cooling Towers and Water Purification

Cooling Towers and Water Purification

Cooling towers and water purification: are they related?

Cooling towers and water treatment are of vital importance in various industrial processes. Initially, for the importance of having an eco-friendly production. On the other hand, environmental care by industries weighs, since if they do not take care of these aspects they can be severely sanctioned.

What are the cooling towers?

Cooling towers or cooling towers are equipment that aims to achieve cooling through steam. Evaporative cooling, as this technique is known, is a natural process that uses water as a coolant. Its function is, generally, to expel the excess heat that comes from different processes and thermal machines into the atmosphere.

How does a cooling tower work?

Cooling towers have been in use by various industries for over a century and have used the principles of evaporative cooling ever since.

To do this, these cooling towers spray hot water in the form of raindrops. These droplets fall into an exchanger fill where they are cooled by a stream of air flowing upward. The water, already refrigerated, rushes into a tank where it is collected to be distributed through a circuit.

Air can be introduced into this system in a natural or forced way, depending on the type of tower. Enter through lower openings above the water tank and run through the cooling tower from the bottom up.

The heat transfer that allows the cooling of the water occurs when the hot water comes into contact with the cold air, converging inside the tower. When it evaporates, the water takes the heat it needs from the rest of the circulating water, cooling the latter.

During this process, 1% of the water flow evaporates for every 7 ° C of refrigeration. The generated water vapor is filtered through a droplet separator, a key element to prevent the water contaminated by Legionella bacteria from being expelled outside.

Finally, the chilled water is collected in a tank, from where it will be sent to attend different processes where its application is necessary.

Cooling tower types

Cooling towers are classified according to their design, being four main types of them. The difference between these towers lies in the way they introduce air to cool the water.

Natural Flow Cooling Towers

Between the colder outside air and the humid air inside the tower, different densities allow airflow to appear. These cooling towers use high-rise chimneys to obtain the desired flow. Due to the large dimensions of these towers, water flows of more than 200,000 GPM are used. The classic example of these cooling towers is found in thermal power plants.

Induced flow cooling towers

They are considered the most efficient cooling towers since the air inside is sucked through a fan located at the top of the tower.

Forced flow cooling towers

Unlike the interior model, the airflow is forced by a fan located at the bottom of the tower and expelled from the top. This design is less efficient since the water discharge rate is much lower.

Cross Flow Cooling Towers

In this design, air enters through the sides of the tower and flows horizontally as the waterfalls. They are towers that need more air but have a lower operational cost compared to previous towers.

Benefits of using a cooling tower

The use of cooling towers or systems whose objective is to achieve evaporative cooling of the water is very beneficial compared to those systems that require chemical refrigerants. Among these benefits are:

  • Produce less acoustic impact.
  • Require less investment than an air condenser.
  • Provides greater energy savings.
  • Reduces the environmental impact.

Is there a risk of having a cooling tower?

Yes. Like all evaporative cooling equipment, cooling towers are susceptible to developing Legionella pneumophila bacteria. Given its operating conditions, a cooling tower can create an ideal environment for the proliferation of this bacterium. Among the most important risks are:

  • Infection by inhalation of a sufficient quantity of microdroplets.
  • Presence of a contaminated strain in the refrigeration system.
  • Expulsion of contaminated drops into the atmosphere.

Water purification

Ensuring water quality is of vital importance for most processes that use this resource at an industrial level. Water purification is the physical and chemical treatment that seeks to eliminate contaminants that may pose a risk. These contaminants can be microorganisms (such as Legionella pneumophila bacteria), inorganic compounds, and organic compounds.

Water purification process

The water purification process follows various stages or phases. The most common are the following:

Phase 1: Disinfection

Chlorine is used as the disinfecting agent responsible for reducing or eliminating the presence of bacteria and viruses in the water. However, it does not guarantee the purification of water, so the addition of other chemical elements and physical processes is required to purify it.

Phase 2: Filtration with granular media

Through this process, solids present in the water can be removed. During this filtering, it is possible to retain the circulation of particles with diameters of at least 1 micron. This prevents the equipment that will use the water in the later stages of the process and in the industrial system that needs it, from clogging or getting dirty with the sediments.

Phase 3: Application of granular activated carbon

Granular activated carbon helps retain organic compounds that can change some physical property of the water (color, odor or taste). In this phase, granular activated carbon also has the job of reducing the free chlorine present in the water. It also functions as a magnet for bacteria like Legionella, preventing water from dragging them into other stages and systems.

Phase 4: Smoothing

For water to not interfere with the operation of equipment and machinery that use it as a resource, its density must be less than 170 mg / L. To decrease it, a negatively charged ion exchange resin is used. These are synthetic spheres with a polymer matrix, capable of exchanging ions in a liquid, according to their charge and its intensity.

Phase 5: Reverse Osmosis

This process is carried out only to decrease the concentration of salts in the water. In reverse osmosis equipment, applying sufficiently high pressure to the water forces it to pass through a porous membrane that filters more than 99% of the salts.

Phase 6: Ozonation

In this phase, we already have purified water. However, disinfection methods must be used to protect the water against bacterial contamination by external sources after reverse osmosis. This is accomplished through the injection of ozone into the water in the form of bubbling. Ozonation has a lasting effect on water, as long as it does not come into contact with the environment.

Phase 7: Sterilization with ultraviolet light

To prevent bacterial reproduction and proliferation, ozonized water passes through a chamber that integrates a UV light source of the appropriate wavelength.

The relationship between cooling towers and water purification

The use of water is part of one of those environmental advantages of refrigeration equipment since 95% of the water used in a cooling tower is reused by the processes that require it.

In this way, and to guarantee the almost autonomous maintenance of the cooling towers, it is necessary that the water used in their systems receives adequate treatment to get rid of the presence of bacteria and other components.

Water purification is precisely the next step after cooling. In this way, by supplying purified water to the system, it prevents large quantities of Legionella from spreading to each component and process that needs the chilled water.

Likewise, it is guaranteed that the water used in air conditioning units, air treatment units, and other industrial processes has the appropriate density to prolong the useful life of the equipment used in each of these processes.

For this, you can count on the work of highly trained specialists in the use and application of water purification techniques for cooling towers. Contact us to receive more information on how to contact our services.

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