In this blog post, we give a summary of what should be considered when choosing a filtration system for your cooling tower filtration requirements.
Industrial manufacturing facilities typically require cooling equipment to cool down chillers, heat exchangers, products and other devices, and this equipment needs to be protected from contaminants found in the cooling water.
In addition, environmental regulations for protecting water sources require that manufacturers return the utilized cooling water to its source in a non-pollutant state.
Cooling tower filtration systems are essential for safeguarding equipment and to abide by these regulations.
Here are some other valuable benefits of cooling tower filtration:
- Improved heat transfer rates in water cooling system for a longer period
- Reduced water consumption
- Improved chemical effectiveness
- Reduced chemical consumption
- Reduced maintenance and energy costs
- Increased equipment lifetime
What is Water Filtration for Cooling Towers?
The above-mentioned regulations require that cooling systems be chemically treated and monitored on a regular basis, specifically for corrosion, scaling, suspended solids and biological fouling.
Corrosion, scaling and biological fouling can be controlled by routine water treatment, but the suspended solids can be more challenging as they can reach the system in various ways, such as production contaminants, pipe corrosion and variations in the raw water composition. Airborne particles are also an issue and, in some cases, can lead to high dirt loads. If left untreated, suspended solids can cause poor energy transfer and obstructions and have an adverse effect on the efficiency of the chemical treatment. In severe cases, suspended solids may lead to expensive replacements, and production efficiency and productivity would be impacted if the system were to be shut down for repairs.
Filtration plays an important role in protecting cooling towers and is divided into 3 categories: side stream water filtration, full stream water filtration and make-up water filtration.
Side Stream Water Filtration:
A percentage (5-15%) of the recirculating cooling water volume flows through a water loop, reducing the overall load of solids. This loop then passes through a filtration system.
Full Stream Water Filtration:
A filtration unit is installed on the discharge side of the pump, after the cooling tower, and continuously filters all of the recirculating water in the system.
Make-up Water Filtration:
Water is lost during the cooling process and make-up filtration process is used to replenish the water reservoir used for cooling. There are four reasons for this water loss:
- Naturally occurring evaporation
- Blowdown/Bleeding: to reduce salinity and particle concentration
- Drift: Mist and/or tiny water drops in small quantities may be carried from the cooling tower, but water loss is less significant than in blowdown and evaporation.
- Overflows or basin leaks: Cooling towers should be examined and properly maintained to avoid overflows and leaks.
Cooling Water Filtration Technologies
Making an informed decision about which filtration technology is the right one for your system is essential. It is important to understand the general application requirements, including filtration degrees, as well as reviewing the advantages / disadvantages and costs of each technology.
Centrifugal separators, also known as hydrocyclones, use centrifugal forces to separate heavy solids larger than 70 micron from water. They are frequently used together with a filtration system that can remove finer particles, but centrifugal separators do not stop organic particles.
Traditional Sand Filters
Sand/media filters route the cooling water to the media bed. There are various types of filter beds, such as, sand, crushed glass, basalt and more. As the water passes through the bed, the particles get trapped and the filtered water then goes to the bottom of the tank to be discharged through the outlet.
Automatic Screen Filters
Automatic screen filters use multiple screens which trap the suspended solids in the cooling water as it passes through them. Filtered water then flows through the filter outlet. The gradual dirt buildup (cake) on the inner screen’s surface begins the cleaning process.
Polymeric Disc Filters
Disc filters are made up of series of flat grooved discs that are stacked together under pressure. As the unfiltered water flows through the discs, trapping the particles. As more particles are trapped, the filter’s pressure differential increases, beginning the cleaning process.
Cartridges & Bag Filters
Cartridge and bag filters are flexible solutions for side-stream filtration. However, they are consumable and require manual replacement. This should be taken into consideration as the disposable nature of these filters will increases expenses over time.
High Efficiency Media Filters
Like the sand filters mentioned above, high efficiency media filtration utilizes sand and crushed glass as the media, but the sand characteristics differ here. Another difference is the cross-flow patterns produced by the water injectors, sweeping over the media bed surface. This causes some of the water to flow in parallel to the top layer for submicron filtration and prevents media fouling and channeling through the media. Contaminants within and on the media are removed by an automatic backwash cycle.
Review of Side Stream Filtration System Characteristics
(click the image to enlarge):
Why Cooling Water is So Complex
Cooling water poses four significant challenges and if not controlled, over time, all can reduce performance and efficient use energy.
- Biological contamination: By design, the cooling tower environment is high in temperature and humidity, making it the perfect breeding ground for bacteria. Even the slight accumulation of biofilm inside components can dramatically reduce efficiency.
- Corrosion: When the air, sodium and additional chemicals present in water are not monitored, they can erode metal and result in leaks in equipment throughout the process and in cooling towers.
- Fouling: When dirt, dust and/or debris clog the cooling surfaces or pipes and the water cannot flow as needed, the air is not cooled as required. This leads to wasted energy, as the system works harder to attain the same outcome.
- Scaling: During the heat exchange process, various minerals, such as calcium, may accumulate on the heat exchange surfaces, creating layers of scaling. If not removed, scaling will increase operating costs.
Selecting the Right Cooling Tower Filtration System
Here are some factors to take into account when contemplating which type of cooling tower water filtration would best meet the requirements and provide the best filtration performance:
- Location: Where in the cooling process will the filtration system be installed?
- Footprint: Are there any limitations on installation space?
- Flow rate: What is the system’s flow rate? Is the preferred pressure variable or steady?
- Filtration degree: What is the micron size of the particles that need to be filtered?
- Particle characteristics: Sand, algae, etc.
- Costs (purchase, maintenance, operations, backwash, energy): Knowing this will assist in the decision.
Amiad’s Cooling Water Filters
Amiad’s filtration solutions and technologies help maintain good water quality, improve heat transfer efficiency, decrease operating costs and are ideally suited to help cope with the challenges associated with the following cooling water applications:
- Spray nozzle filters for nozzle protection
- Side stream filters for cooling towers
- Full stream cooling systems
- Upstream filtration – heat exchangers protection
- Condenser and chiller loop protection
- Cooling tower makeup
With a comprehensive product line and various filtration technologies – screen, disc, centrifugal separators, media and high-efficiency media – Amiad offers customized solutions for the harshest environments, varying water conditions and demanding technical requirements.
You can read more about how the filtration solution for cooling tower water treatment was implemented in our case study: Cooling Tower Filtration for Oil and Gas Company, USA.
Amiad also provides treatment solutions for other challenging industrial water applications, such as, process water filtration, intake water filtration and seawater filtration.
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