The use of cooling towers to cool circulating water helps recycle water, leading to water and chemical savings as the chemicals are retained in the system. However, this process can cause issues related to corrosion, scaling, and the increased growth of bacteria.
- Second, the water in cooling towers is typically warmer than normal (tepid), providing an optimal environment for the growth of organisms.
- Third, the operation of cooling towers removes pollutants from the air while accumulating them in the water within the tower basin, causing fouling and bacterial growth.
As a result, microbial deposits, scaling, and sludge build-up adhere to pipes and heat exchange equipment, increasing pipe resistance, reducing water flow, and decreasing the heat exchange efficiency of the entire system, leading to higher energy consumption.
In addition, metal corrosion can cause severe damage to the system, requiring shutdowns for repairs and maintenance, which increases costs and affects production quality while reducing the system’s lifespan.
Types of Chemicals Needed for Cooling Towers
- Chemicals to prevent/inhibit scaling and corrosion in the system (See chemicals)
- Chemicals to prevent algae and microbial growth in cooling towers (See chemicals)
In the past, water treatment chemicals commonly used chlorine or phosphates (inorganic phosphates) / phosphonates (organic phosphates) to inhibit scaling and corrosion. However, these chemicals are being phased out today due to their negative impact on the water environment, such as contributing to harmful algal blooms and eutrophication.
What Are Corrosion Inhibitors and Scale Inhibitors?
Corrosion inhibitors and scale inhibitors are chemicals specifically designed to slow down or prevent scale formation when added to water at low concentrations, typically to prevent the creation of scale. To achieve this, these chemicals react with substances capable of forming scale in the water, creating a stable thermodynamic region. Alternatively, they may prevent the development of scale crystals.
Therefore, the use of these chemicals is a promising and effective approach since a very low dosage (a few dozen ppm) is sufficient to prevent scale formation over an extended period for both surface treatment and equipment.
Common types of scale inhibitors include: Inorganic polyphosphates, Organic phosphates esters, Organic phosphonates, and Organic polymers.
Criteria for Choosing Scale Inhibitors: Efficiency, Stability, Compatibility.
Effects of Using Chemicals
- Increases heat transfer efficiency by removing scale from heat exchangers.
- Prevents scaling from precipitates, suspended matter deposits, and microbial growth.
- Reduces maintenance time and system downtime.
- Maintains and protects metal components by minimizing corrosion and pitting, thus preventing system failures.
- Increases the concentration/recycling cycle of the system.
- Reduces the amount of makeup water and chemicals required, thereby lowering wastewater treatment costs for clients.
- Minimizes bacterial growth on the cooling tower surfaces, leading to maximized water-to-air contact and improved cooling capacity.