Evaporative cooling towers

Evaporative cooling towers

Monitoring cooling water quality

Cooling Water Treatment

of evaporative cooling systems

Most industries need the largest part (almost 90%) of their used water quantity for cooling. This immense water consumption clearly illustrates the essential role of water cooling for industrial production. Nowadays, hardly any branch of industry can manage without the cooling capacity of open evaporative cooling systems: the chemical industry, food industry, breweries, airports, data centers, etc.

In order to operate an evaporative cooling system as efficiently as possible, the consumption of cooling water should be reduced on the one hand and on the other hand the protection of the entire system against corrosion, deposits and biological growth should be increased. Therefore, a trouble-free, economical operation of an evaporative cooling plant requires an individually optimized water treatment for each plant.

Since 2017, the 42nd BImSchV – Federal Immission Control Ordinance – defines binding guidelines for the operation of natural draft cooling towers, evaporative cooling systems and wet scrubbers. Relevant systems have to be designed, constructed and operated in such a way that state of the art technology prevents contamination of the process water by microorganisms, especially legionella.

Operators of these plants have to meet the hygienic requirements as well as to ensure an economic operation of the systems. The treatment of the cooling water with different chemicals required for this purpose must be individually adapted to the respective plant and the prevailing conditions. To ensure that the chemicals used achieve the desired effect and at the same time the consumption of chemicals is minimized , continuous monitoring of the circulating cooling water is essential.

ProMinent offers all components required for automatic monitoring of relevant parameters of your cooling water circuit. Our portfolio includes measuring and control devices, sensors, pumps, disinfection systems, digital fluid management and pre-assembled complete solutions. These products of the various divisions, which have been specifically optimized for the application of cooling water treatment, are characterized by a long service life, low maintenance and high reliability.

Our experts will be pleased to advise you on the selection of the appropriate products for your system and will create individual solutions tailored to your customer requirements.

Background Information

Focus on evaporative cooling towers

Biology in cooling towers

Biology in cooling towers

The majority of microorganisms live in biofilms. For a biofilm to grow only very few requirements need to be met: a surface, sufficient nutrients and dampness. The physical and chemical conditions in technical systems carrying water, such as evaporative cooling towers, provide ideal habitats. Furthermore, biofilms allow legionella, which enter the evaporative cooling towers via makeup water, to take up residence and reproduce in these systems in the first place. Given the optimum living conditions these systems also provide for legionella, they can grow undisturbed and reach concentrations harmful to health. This explains why an appropriate mode of operation is essential to prevent the formation of pronounced biofilms in evaporative cooling towers. Such a mode of operation must be aimed at making the living conditions as unfavourable as possible for microorganisms and the growth of biofilms.

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Corrosion in cooling towers

Corrosion in cooling towers

Due to the operating mode of open evaporative cooling plants, the salt concentration in the process water is constantly increasing. An excessive salt and mineral content leads to calcification and corrosion in the cooling system and its pipes. Algae and biofilm formation as well as dust particles introduced from the ambient air also have a negative effect on the cooling capacity of the plant and also damage the installed materials. The effects of corrosion damage are far-reaching: increasing maintenance costs, reduced efficiency of the heat exchangers, contamination of the circuits, operational disturbances or even shutdown of the plant. A continuous monitoring of the corrosion enables a timely detection of incipient damage.

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Water treatment in cooling towers

Water treatment in cooling towers

The concentrated process water caused by evaporation has to be regularly replaced with fresh makeup water. To ensure that
the salt concentration does not rise to a range where it impacts negatively on the cooling system’s efficiency and materials,
the concentration of the process water should be continuously monitored by means of a conductivity measurement. Automatic blow down and an appropriate supply of fresh water minimize the risk of deposits and corrosion. Additionally, corrosion
inhibitor and hardness stabilizer are added directly to the supplied fresh water, proportionate to volume, in order to protect
the system. Since microbiological films also reduce the efficiency of the cooling system and may provide a home for pathogenic bacteria, biofilms as well have to be combated through the addition of chemicals.

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Online measurement of oxidizing biocides

Online measurement of oxidizing biocides

In order to fight microorganisms, either non-oxidizing or oxidizing biocides are added to the cooling water circuit. On the one hand, non-oxidizing biocides possess good material compatibility, but the underlying mechanism of the biocidal effect allows the bacteria present in the cooling water circuit to develop resistance. Therefore, the alternation of two different non-oxidizing biocides at regular intervals is highly recommended. As the effectiveness of oxidizing biocides is based on another mechanism, it prevents the bacteria from developing resistance.

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Online corrosion monitoring

Online corrosion monitoring

Chemical and physical conditions prevailing in evaporative cooling towers promote corrosion of metal surfaces. As corrosion processes cannot be avoided completely, cooling water should additionally be treated with corrosion inhibitors, and also the state of the system should be monitored continuously. On the one hand, online corrosion monitoring enables the evaluation of the effectiveness of the corrosion inhibitor, and on the other hand, provides information on the actual state of the system and thus makes it possible to detect arising damages at an early stage.

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Relevant products and services

Controller

The controller AEGIS II has been developed especially for the treatment of cooling water in evaporative cooling towers. It monitors, controls and documents all relevant parameters as requested by the regulations.

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Sensors

Sensors that measure cooling water parameters need to cope perfectly with this constantly fluctuating water quality. Measurements must be reliable and reproducible without any need for additional maintenance efforts or shortened service intervals. ProMinent offers sensors for most parameters that are commonly analysed to ensure cooling water quality. These sensors, ProMinent developed especially for this application, are optimised for high performance under challenging conditions.

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Solenoid-Driven Metering Pumps

The amount of chemicals added depends on the specific, local conditions and varies for each system. In addition, the consumption of chemicals must be minimised. As one of the market leaders in the area of solenoid-driven metering pumps, ProMinent has a wide experience that, in combination with continuous innovation and development of new technologies, results in the most modern and reliable metering pumps.

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Pre-assembled panels for cooling water monitoring

Based on years of experience and the close collaboration with our customers we have designed six different versions with varying configuration for the application of cooling water treatment. All pre-assembled panels can be easily integrated in the cooling water circuit and put into operation without the slightest effort.

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Disinfection Systems

The biocides chlorine dioxide and ozone show effective disinfection strength independent of pH and have the additional advantage of not forming toxic AOX-compounds. Furthermore, because of their gaseous state these disinfectants fight microbiological films most efficiently. Due to the high reactivity of these gases, chlorine dioxide and ozone must be produced on-site in special systems and cannot be stored or transported as ready to use biocides. ProMinent developed, explicitly for the treatment of cooling water, reliable and secure complete systems for on-site, on demand production of these disinfectants.

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Digital fluid management

DULCOnneX

As digitalization and networking advances more and more, new possibilities arise to monitor, control and optimize processes. Our solution for digital fluid management collects versatile information, processes all data and takes advantage of this information to efficiently control processes. Operators have location independent and real-time access to all available information required for optimal monitoring and control of any installed device, system or compound.

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