The constant trickle of water can hollow out rocks. Furthermore, a continuous flow of water will gradually erode everything in its path. A more dramatic and spectacular example is the Grand Canyon in Arizona, United States. Furthermore, if the flowing water is hot, it will erode or dissolve the solids it passes through (leaching) more quickly than cold water. By the time the hot water returns to the cooling tower, it is already full of suspended solids. The cooling tower, as a means of dissipating heat, flows hot water from the top of the tower, and cool air from the surrounding environment that comes into contact with the warm water absorbs the heat. As a result, the water becomes cooler and the air becomes warmer.
Hot water also tends to be corrosive and form deposits. This is why the materials used to construct cooling towers must be durable and able to withstand large temperature differences. Certain types of wood and plastic can be used for cooling tower construction. If the materials are of poor quality, the cooling tower construction will be short-lived and even dangerous. When hot water enters the cooling tower and mixes with suspended solids, some of the water evaporates, leaving the suspended solids behind. This suspended solids-rich liquid concentrates in the sump at the bottom of the cooling tower. Over time, the concentration of these suspended solids increases until it reaches a level that must be controlled by removing it from the system, known as blowdown.
The outside air that comes into contact with the water from the cooling tower contains dust or small particles, as well as microorganisms such as various bacteria, fungal spores, and algae. These dust or small particles become suspended and accumulate/concentrate, forming deposits in the form of mud or crust. In the presence of sunlight, these microorganisms, such as bacteria and algae, photosynthesize, multiplying and increasing in number. Pathogenic bacteria like Legionella can even cause Legionnaires' disease. This mud and algae contaminate and clog heat exchanger tubes, accelerating their corrosion.
In the heat exchanger, if the scale thickness is 0.3 mm, it is estimated that there will be a heat/energy loss of 10% and if the scale thickness is 0.6 mm, it is estimated that there will be a heat/energy loss of 23%. And in general, fouling causes an annual energy/heat loss of around 15%, so it requires maintenance and pipe replacement every 3–5 years. If not handled properly, heat/energy loss due to fouling can reach up to 70% after five years. Fungi and bacteria will cause wood to rot/decompose, making it brittle and destroyed. Likewise, oxidation reactions on metal surfaces, because these metals release electrons or capture oxygen, causing corrosion on the metal. Corrosion on metal causes the metal to become increasingly eroded, brittle and damaged.
Maintaining water quality from various contaminants in a cooling tower, which volume thousands of tons per hour and operates 24 hours a day, is certainly not simple. Only by maintaining this water quality can the cooling tower's performance and lifespan meet its design targets. Using effective, efficient, and environmentally friendly technology is the best option. Advanced Oxidation Process (AOP) technology is an innovation to address these issues. This technological approach effectively, efficiently, and environmentally friendly addresses various water issues in cooling towers. For example, in algae cells, ions from the Advanced Oxidation Process (AOP) attack the sulfide groups contained in amino acids in the remaining proteins involved in photosynthesis. As a result, photosynthesis is inhibited, and the cells dissolve or disintegrate. If algae and microbial cells remain, their regrowth is inhibited by the AOP ions in the water, thus preventing algae growth. During this process, bacteria are also killed or rendered inactive.
The second example is the rust prevention mechanism of pipes. Iron (Fe) loses electrons according to the oxidation reaction and forms rust. However, when the AOP material participates in this reaction and releases electrons first, the iron is prevented from releasing electrons, thus suppressing rust formation. The rusted iron is converted to black rust through the AOP reaction, forming a dense oxide film that prevents further corrosion and protects the pipe and structure.
And the third example is the scale prevention mechanism. When water passes through the AOP system, calcium (Ca) and magnesium (Mg) ions—the components that cause hardness—are removed through crystallization in the liquid phase, thus softening the water. The resulting calcium carbonate particles cannot adhere to pipes. In hard water containing calcium (Ca) and magnesium (Mg) ions, needle-like scale structures typically form and adhere to pipe walls. Through AOP treatment, scale-forming ions undergo particle growth in the liquid phase, forming spherical particles ranging in size from a few micrometers to tens of micrometers.
According to the Gibbs–Kelvin formula, the volumetric free energy is reduced and the adhesive force is lost, thus preventing it from sticking to the pipe walls. Scale will accumulate at the bottom of the basin and be removed by a blowdown mechanism. In addition, this AOP technology will also remove scale that has already stuck to the pipes (scale removal existing pipes) and also the sterilization effect which is also very important for the quality of the cooling tower water such as preventing wood rot/decaying and killing pathogenic bacteria, both of these aspects will be explained on another occasion, Insha Allah.
To measure cooling tower performance based on the problems encountered and the solutions implemented, several parameters are used. These parameters include:
• Water pH
• Total dissolved solids (TDS)
• Tower equipment checklist
• Filters and strainers
• Wet bulb temperature and humidity
Meanwhile, safety in cooling towers is also important and needs to be considered. These include:
• Chemical additives (if used and not yet using AOP technology)
• Rotating equipment
• Dangers of hot water
• Working at heights
• Working safely on the cooling tower.
• Equipment failures
• Metal corrosion and wood rot/decay
The use of cooling towers can be said to be an important and fundamental equipment for industrial operations in general. Starting from power plants that still use fossil energy, cofiring or biomass power plants to geothermal power plants, data centers, chemical industries, biorefinery industries, petrochemical industries, iron and steel industries, food industries, pharmaceutical industries, textile industries, pulp and paper industries and so on. Related to the era of decarbonization and sustainability / sustainability of the use of renewable energy such as biomass including wood pellets and palm kernel shells / PKS as part of carbon neutral fuels or carbon negative such as carbon capture and storage (CCS) to biochar, of course environmentally friendly technology, especially easy to operate, affordable investment costs to repair-maintenance, will be an option for these industries, such as AOP technology for water conditioning in cooling towers so as to provide significant savings.
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