Impact of hardness on cooling towers and how to control it

Cooling towers are critical components in a variety of industries, including power plants, petrochemical plants, and water treatment facilities.

They play a crucial role in cooling the water used in industrial processes. However, the efficiency of cooling towers can be compromised by various factors, one of which is water hardness. In this article, we will take an in-depth look at the impact of hardness on cooling tower efficiency and how to control it.

Water hardness is a common problem faced by many industries in Indonesia. With diverse geographical characteristics, ranging from remote islands to major cities, water sources in our country have varying levels of hardness. Some areas have high hardness groundwater, while other areas may face surface water contamination issues. A good understanding of the impact of hardness on the cooling system and how to overcome it is crucial for the continuity of industrial operations in the country.

What is Water Hardness?

Before we delve into its impact on cooling towers, let us first understand what water hardness is. Water hardness is caused by the presence of certain metal ions in water, mainly calcium (Ca2+) and magnesium (Mg2+). Water that contains high concentrations of these ions is referred to as "hard water."

Water hardness is usually expressed in terms of milligrams per liter (mg/L) or parts per million (ppm) of calcium carbonate (CaCO3). Based on the level of hardness, water can be classified as follows:

• 0-60 mg/L: Soft water
• 61-120 mg/L: Slightly hard water
• 121-180 mg/L: Hard water
• 180 mg/L: Very hard water

In Indonesia, water hardness levels vary depending on the location and source of the water. For example, groundwater in some areas of Java tends to have higher hardness levels compared to surface water in Sumatra or Kalimantan.

Impact of hardness on cooling tower efficiency

FRP water softening system, for example, has been widely used in various industrial sectors to address hardness issues.

2. Use of Scale Inhibitors

Scaling inhibitors are chemicals that are added to cooling systems to prevent scale formation. They work by interfering with the crystallization process of scale-causing minerals. Some commonly used types of scale inhibitors include:

• Phosphonates
• Polymers
• Phosphonate-polymer blends

The choice of the right scale inhibitor depends on the water composition, system operating conditions and other factors. Beta Pramesti's Chemicals for cooling towers includes various types of scale inhibitors tailored to the specific needs of industries in Indonesia.

3. pH control

Controlling the pH of the water in a cooling system is an important strategy to reduce scale formation. Generally, maintaining a pH between 7.0 and 8.5 can help minimize scale formation while avoiding corrosion. However, the optimal pH may vary depending on the composition of the water and the type of treatment chemicals used.

The use of acids or bases to adjust pH should be done carefully and under the supervision of an experienced water chemist. An overdose of pH adjusting chemicals can lead to corrosion problems or equipment damage.

4. Dispersants

Dispersants are chemicals that help keep mineral particles suspended in water, preventing them from settling and forming scale. They work by modifying the surface charge of particles, so that the particles repel each other and stay separated.

The use of dispersants can be very effective in reducing scale formation, especially when combined with scale inhibitors. However, proper selection and dosage of dispersants is critical to ensure their effectiveness.

5. Reverse Osmosis (RO)

For cases where water hardness is very high or when very high quality water is required, reverse osmosis (RO) systems can be an effective solution. RO uses a semi-permeable membrane to remove most dissolved minerals, including calcium and magnesium, from water.

While the initial investment for an RO system is quite high, in the long run it can yield significant savings through improved system efficiency and reduced water treatment chemical requirements. Beta Pramesti's Reverse osmosis system has proven effective in addressing water hardness issues in various industries in Indonesia.

6. Electromagnetic Treatment

Electromagnetic water treatment methods have gained popularity in recent years as a non-chemical alternative for controlling hardness. These systems use electromagnetic fields to alter the crystal structure of hardness-causing minerals, thereby reducing their ability to form scale.

Though the effectiveness of this method remains to be seen.

Although the effectiveness of this method is still debated within the scientific community, several industries in Indonesia have reported positive results from using electromagnetic treatment systems, especially in combination with other treatment methods.

7.

7. Blowdown and Makeup Water Management

Effective blowdown management is key to controlling mineral concentrations in cooling systems. Blowdown is the process of removing a portion of water from the system and replacing it with new water (makeup water) to keep mineral concentrations within acceptable limits.

Optimizing the frequency and volume of blowdown is the key to controlling mineral concentrations in the cooling system.

Optimizing blowdown frequency and volume can help reduce scale formation while minimizing water wastage. The use of automated monitoring systems such as Sentinel CTS for cooling tower monitoring can greatly assist in efficient blowdown management.

Implementation of Hardness Control Strategies

Implementing an effective hardness control strategy requires a holistic approach and a deep understanding of the cooling system as well as local water characteristics. Here are some key steps in implementing a successful hardness control program:

1. Comprehensive Water Analysis

The first step in addressing hardness issues is to conduct a thorough analysis of the water used in the cooling system. This should include not only the measurement of total hardness, but also other parameters such as alkalinity, pH, conductivity, and the concentration of specific ions.

In Indonesia, the characteristics of water can be found in the following sections.

In Indonesia, water characteristics can vary greatly depending on location and source. For example, groundwater in some areas in Java may have much higher levels of hardness compared to river water in Kalimantan. Therefore, accurate and comprehensive analysis is essential.

2. Selection of Treatment Method

Based on the results of the water analysis and other operational considerations, select the most suitable combination of treatment methods. This may involve the use of water softeners, scale inhibitors, dispersants, or a combination of different methods.

It is important to consider not only the effectiveness of water softening, scale inhibitors, dispersants, or a combination of methods.

It is important to consider not only the effectiveness of the method in controlling hardness, but also factors such as operational costs, chemical availability, and environmental impact. For example, the use of RO systems may be very effective but may not be practical for all industries due to high investment and operational costs.

3. Optimization of Chemical Dosage

If using water treatment chemicals, it is very important to optimize their dosage. Dosing that is too low will not be effective in controlling hardness, while over-dosing can lead to wastage and even other operational issues.

The use of an automated dosing system is a great way to optimize dosing.

The use of an automated dosing system such as the Beta Pramesti dosing pump can help ensure accurate and consistent dosing. However, it is important to regularly verify and adjust dosing settings based on water quality monitoring results.

4. Continuous Monitoring and Control

Implementation of a hardness control program is not a "one-off" process. It requires continuous monitoring and adjustment to ensure its effectiveness. This involves:

• Routine testing of key water quality parameters
• Visual inspection of equipment for signs of scale formation or corrosion
• Adjustment of chemical dosages or operational parameters based on monitoring results

The use of automated monitoring systems such as Sentinel WS for water treatment system monitoring can greatly assist in this process, providing real-time data and early warnings of changing water conditions.

5. Operator Training

Even the most sophisticated hardness control program will not be effective without properly trained operators. Ensure that all personnel involved in the operation and maintenance of the refrigeration system understand the basic principles of water hardness, its impact on the system, and the correct procedures for implementing and monitoring the control strategy.

In Indonesia, where the level of water hardness is high, the level of water hardness is high.

In Indonesia, where the level of understanding of industrial water treatment may vary, investment in operator training can provide a significant return in the form of more efficient system operation and a reduction in hardness-related problems.

Conclusion

Water hardness has a significant impact on cooling tower efficiency and performance. From scale formation that reduces heat exchange efficiency to increased risk of corrosion and microbial growth, hardness can cause a wide range of operational and financial issues for the industry.

However, a good understanding of hardness can lead to more efficient system operation and a reduction in the number of problems associated with it.

Considering the diversity of water conditions in Indonesia, it is important to recognize that there are many factors that need to be taken into account.

Given the diversity of water conditions and industrial needs in Indonesia, it is important to adopt a customized approach in addressing hardness issues. Consultation with an experienced water treatment expert, such as the technical team from Beta Pramesti, can assist in designing and implementing the most effective solution for each facility's specific needs.

By proactively addressing hardness issues, industries can not only improve their operational efficiency, but also contribute to a more sustainable use of water resources - an increasingly important aspect in an era of climate change and increasing environmental pressures.

Questions and Answers

Q1: Are there any natural methods to reduce water hardness in cooling systems?

A1: Yes, there are some natural methods that can help reduce water hardness, although their effectiveness may be limited for large industrial-scale systems. Some methods include:

• Use of activated carbon filters which can help reduce some hardness-causing minerals.
• Utilization of certain aquatic plants in pre-treatment systems that can absorb some of the calcium and magnesium.
• Use of moringa seeds which have been known to have natural coagulant properties.

However, for large-scale industrial cooling systems, these methods are generally not effective enough and often need to be combined with conventional water treatment approaches.

Q2: How can we tell if our cooling system is experiencing a hardness problem?

A2: Some signs that indicate a cooling system may be experiencing a hardness issue include:

• A gradual decrease in cooling efficiency
• Increased energy consumption to achieve the same level of cooling
• White or grayish deposits on equipment surfaces
• Increased frequency of leaks or pipe breaks
• Water quality test results showing high hardness levels

If you observe these signs, it is advisable to conduct a thorough water analysis and consult a water treatment expert to determine the appropriate steps.

Q3: Does the use of seawater in cooling systems require a specialized approach to address hardness?

A3: Yes, the use of seawater in cooling systems does require a specialized approach. Seawater has much higher levels of hardness and salinity than fresh water, which can lead to more serious scale formation and corrosion issues. Some special approaches include:

• Use of corrosion-resistant construction materials such as titanium or special nickel alloys
• Implementation of desalination systems such as reverse osmosis before seawater is used in the cooling system
• Use of scale and corrosion inhibitors specifically designed for seawater environments
• Increased blowdown frequency to control salt concentration

In Indonesia, especially for industries located in coastal areas or small islands, an understanding of seawater cooling system management is essential for efficient and sustainable operations.

References

1. Pincus, L. I. (2021). "Practical Boiler Water Treatment including Air-Conditioning Systems". Page. 226. "The cooling tower is designed to bring the hot water into intimate contact with the surrounding air, which produces efficient cooling but also brings acidic gases from the air into solution, making the water more corrosive."

2. Spellman, F. R. (2018). "Handbook of water and wastewater treatment plant operations". Pp. 636. "Hardness in water is caused by the presence of certain positively charged metallic ions in solution, such as calcium and magnesium. The most common hardness-causing ions are calcium and magnesium, but others include iron, strontium, and barium."

3. Pincus, L. I. (2021). "Practical Boiler Water Treatment including Air-Conditioning Systems". Pp. 239. "The saturation index I* is the algebraic difference between the actual pH of the water and the calculated pH. When I* is zero, the tendency to form scale is at a minimum. When I* is positive, there is a tendency to form scale in the cooling system."

4. Spellman, F. R. (2018). "Handbook of water and wastewater treatment plant operations". Pp. 464. "Water hardness, calcium carbonate, magnesium, soap and detergent effectiveness, scale formation, water softening, corrosive tendencies, alkalinity, hardness and alkalinity relationship, odor control, odors from septic wastewater, industrial wastes, treatment processes, chemical oxidation, chlorine, potassium permanganate"

5.

5. Pincus, L. I. (2021). "Practical Boiler Water Treatment including Air-Conditioning Systems". Pp. 257. "The open-spray cooling system, blowdown, evaporation, windage, and other mechanical losses are discussed. The water spray comes into close contact with air, causing soluble gases in the air to dissolve and concentrate in the recirculating spray water."