Seeking advice on scaling of wet air cooler tube banks in refineries and chemical plants located in coastal areas
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Dear seniors: I am based in the Dalian area, and my workplace is located near the sea. In many of the facilities there – such as units for continuous reforming, alkylation, isomerization, and MTBE production – the tubes or finned tubes of the wet air coolers or hybrid air coolers are suffering from scaling, as well as severe corrosion of the structural components (galvanized parts are severely corroded, while stainless steel parts remain uncorroded). Initial tests have shown that the main components involved are calcium salts and magnesium salts. Considering the need to clean these systems, high-pressure water cleaning was attempted; however, it was found that only the surface salt layer and scale could be removed, while the interior spaces of the tubes could not be cleaned, resulting in poor outcomes. May I ask whether the effect of chemical cleaning is rapid and lasting? Some similar posts suggest using coatings and improving the quality of cooling water, such as by using softened water – what is the effectiveness of these methods? I would be extremely grateful if you, my seniors, could offer me some guidance!
Originally, using circulating water gave results similar to those shown in the diagram; later on, using steam condensate and pure water yielded better results. Also, the factory is by the sea, so the sea breeze at night is likely to be very humid
For carbon steel structural frameworks, special anti-corrosion methods can be employed, as galvanizing the surface of carbon steel does not provide effective corrosion resistance. If high-pressure water jet technology is not effective for cleaning tubes, chemical cleaning can be used as an alternative, and its results are better than those achieved with high-pressure water.
Senior, could you be more specific?
Yes, the salt mist is quite severe by the sea
That’s right. First, for steel structures, highly corrosion-resistant coating materials are used to prevent corrosion, such as aliphatic polyurethanes and other similar materials; however, it is essential to pay attention to the surface treatment of the metal. The second approach is to use chemical cleaning to solve the problem. If the organization has professionals for cleaning, they can be entrusted to carry out the task. What needs to be done is indeed not easy; it is possible to use cleaning agents that cause little or no corrosion to metal materials. Pay special attention to the cleaning of aluminum alloy fins. First, select the cleaning agent and conduct a scale-removal test on it. Third, if the heat exchange tubes (transparent tubes) are being updated, apply a coating to them for corrosion prevention.
I am extremely grateful for the kind guidance from my senior
This is the result of chemical cleaning of the continuous reforming unit
This is the effect of applying a special coating after chemical cleaning; however, the actual heat exchange performance and maintenance-free characteristics still require long-term testing and verification through actual equipment operation!
May I ask what kind of water we used as a water source before, and was its hardness measured?