Take back control

Losing heat? Can’t cool it down? Seems like your heat transfer system needs a tune-up! Time has come to take back control of your heat exchangers and cooling towers!

The chemical industry is producing a huge variety of chemicals by using various processes. Most of the time, however, basic chemicals are reacting with each other to obtain the desired finished chemical. While some chemical reactions require heat in order to take place (endothermic), some others, on the contrary, release a fair amount of heat once initiated (exothermic). Because their processes require thermal flexibility and stability, heat exchangers are essential for chemical and petrochemical companies. Heat transfer systems used in the chemical industry can be based on different concepts and technologies and use a wide range of heat transfer fluids. The majority of chemical companies will use mineral oils or water to carry, dissipate or exchange heat in their processes. However, regardless of the thermal fluid in use, heat transfer systems will lose efficiency over the years because of fouling. Fouling is the accumulation of undesirable material such as varnish, sludge, algae, scale, insoluble salts and minerals on the internal surface of heat transfer systems. The following article provides more information on fouling and suggests how to prevent this phenomenon from causing efficiency loss in heat transfer systems.

For all of the challenges heat transfer systems can pose, the tribology specialist Klüber Lubrication has developed highly efficient solutions which can help to restore the full efficiency of water circulation and cooling systems.

Get more out of oil circulation systems

Regardless of whether they are designed to heat or cool down processes, most oil-circulating heat transfer systems in chemical and petrochemical facilities still use group I mineral oils in this heavy-duty application. Group I mineral oils are derived from crude oil. The refining process uses a solvent which leaves impurities and hydrocarbon molecules of different sizes in the mixture. Some heat transfer systems can use up to a hundred thousand liters of oil as a transfer medium, which makes group I mineral oils with their affordable price attractive for chemical companies.

In most cases, heat transfer systems are far from being perfectly designed. In the majority of the systems, the oil is subject to considerable stress, due to an intense localised heating source in combination with low flow velocity. The oil can also come into contact with the air in the expansion tank, causing it to oxidize and degrade faster. Group I oils contain unsaturated hydrocarbons and asphaltene components that react with oxygen, provoking degradation at high temperature. 

Pushing group I mineral oils to their performance and service life limits in heat transfer systems will most likely lead to varnish or carbon buildup throughout the circulation system, which will definitely cause fouling and over time affect system efficiency. The tribology specialist Klüber Lubrication is well aware of the challenges heat transfer systems can represent for chemical companies, and has developed a comprehensive range of products and solutions for this application. The highly refined and hydrotreated base oils used in these products offer much better stability at high temperature and make extended service life possible.

Meeting the requirements perfectly

Modern heat transfer systems are operating in harsh conditions and may require a special thermal fluid or special compliance features such as NSF H1 registration for incidental contact with food. Technology advancement in heat transfer fluids has resulted in consumers today having a wide range of options to choose from according to their needs. Thermal fluids based on different chemistries like polyalphaolefin, polyalkylene glycol or silicone can show numerous advantages in certain applications and could be the right alternative where conventional mineral oils are not suitable.

Detailed analysis, monitoring and maintance

If you have recently noticed damage caused by a group I mineral oil to your system, and realized how poor the efficiency of your heat exchange system has become over the years, you should know that a suitable cleaner/conditioner for example from Klüber Lubrication can restore the system’s efficiency without the need for dismantling or prolonged shutdown. Efficient, headache-free operation of heat transfer systems begins with a good oil monitoring program. Just like blood testing can be useful to analyse health issues, an oil sample from the heat transfer system can reveal crucial information to help prevent eventual failures, safety issues, and even fires.

No tolerance for intruders in water circulation systems

For processes where the heat is not that critical, or where cooling is needed, most chemical companies will rely on water circulation systems. Fouling also occurs in water circulation systems, as non-distilled industrial water contains mineral salts that can bond to metal surfaces. The difference between water and oil circulating systems is the fouling factor, a mathematical value (usually referred to as Rf or Rd) that quantifies the theoretical resistance to heat flow due to the build-up of a layer on the internal surfaces of heat exchangers. It is a ratio between the transfer coefficient of a clean heat exchanger and the same unit after a fouling problem has set in. The standard fouling factors for common liquids and gases are specified in a formal list, which is easily accessible on the internet.

Scale deposits, usually calcium and magnesium compounds, affect the operating efficiency of air compressors, chillers, exchangers, vacuum pumps, boilers, cooling towers and other water-wetted equipment. If not properly treated, sediment, sludge, and scale building up in the recycled water leads to a loss of efficiency and increases energy consumption. Poorly maintained systems can also harbor legionella bacteria, which pose a health risk to those working near such equipment. Every year, the chemical industry loses billions of dollars in revenue due to equipment downtime and increased power consumption, caused by limescale build-up clogging the pipes of the production equipment.

Back to top operating efficiency in a quick, safe and easy way

Considering that equipment like cooling towers only offers an efficiency of 70 to 75 %* from the outset, it is easy to imagine how poor the efficiency becomes once a 3-6 mm  layer of scale has built up. Water-based descalers provide a quick, safe and easy way to clean the equipment and bring it back to top operating efficiency. Klüber Lubrications offers a complete range of high-performance descalers, which are enhanced with wetting agents, corrosion inhibitors and degreasing compounds. These are designed to penetrate and remove encrusted limescale, rust, dirt and corrosion byproducts from water-wetted inner surfaces of commercial and industrial processing equipment. Some high-technology descalers also contain active dyes that changes color in order to let the operator know when action is required.

However, not all descaler chemistries are suitable for all kinds of metal surfaces. For example, special attention has to be paid to electroplated and aluminium surfaces, as traditional descalers based on mineral or organic acids could attack and damage these surfaces and components. It is therefore advisable to contact a specialist like Klüber Lubrication before cleaning a water circulation system. The tribology expert provides technical service, develops efficient cleaning procedures and can even assist maintenance teams on-site in cleaning operations.

Conclusion

As a long-standing partner of the chemical industry, Klüber Lubrication has developed a variety of highly efficient products for all applications in heat transfer systems. These highly efficient heat transfer fluids, cleaners/conditioners and descalers can help to get back the efficiency of water circulation and cooling systems. Taking into account the individual requirements and specific conditions of the application, Klüber Lubriation will provide not only the right products, but the company also offers all kinds of services required in order to optimise the efficiency of the process.

By Jonathan Venditti, Global Market Manager Chemical Industry

Sources:
https://www.watertechonline.com/process-water/article/14071807/understanding-and-preventing-heat-exchanger-fouling
https://chemicalengineeringsite.in/cooling-tower-efficiency-calculations/#:~:text=Cooling%20tower%20efficiency%20is%20limited%20by%20the%20ambient%20wet%20bulb%20temperature.&text=This%20requires%20very%20large%20tower,in%20between%2070%20to%2075%25.

 

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