MechChem Africa January-February 2025

⎪ PowerGen,PetroChem and Sustainable energy management ⎪

Using the analogy of a domestic kettle, Lund explains that compounds such as calcium and magnesium form a hard scale that ad heres to surfaces. This limits the transfer of heat from the fire side of the boiler to the water side, making the boiler inefficient when it comes to the production of steam. This does not happen immediately, how ever, Paterson warns: “Poor water treat ment damages boilers over long periods. Water does not go off specification in one day. Therefore, water treatment needs to be done correctly and consistently, every single day. Unfortunately, this is what many manu facturing and processing facilities miss.” Lund notes that the relationship be tween on-site boiler operators and water treatment companies forms a strong foundation for a watertight boiler water treatment strategy: “We partner with water treatment companies to train boiler operators in the importance and practice of testing feedwater daily. If any elements are out of specification, they raise that with the regional AES team, and we escalate this to our water treatment partners.” At the beginning of the boiler water treatment process, solids are removed via different forms of filtration. Plants with very high TDS levels might require the installa tion of a reverse osmosis (RO) plant, which

age when reaching a pipe bend. “This foaming also disrupts the measure ment of water levels to the point where, despite indications that these are correct, there may be very little to no water in a boiler, causing it to overheat or even to explode,” he explains. According to Lund, when scale has built up to the point where the equipment is at risk and efficiencies are compromised, clients have two options: using an on-line descalant; or a difficult and expensive off line acid wash, to ‘pickles the boiler’. In this case, in addition to lost production time, it can take up to four days to acid wash a boiler. The cost of the chemicals, as well as neutralising and disposing of the result ing acid effluent can have a very negative financial impact. Boilers requiring repairs after this acid wash process will further add to the overall cost. “Years of poor boiler water treatment can really add up, with negative operational and financial consequences. With this in mind – and aligned with our performance guarantee to clients – we do as much as we can to ensure that clients are aware of water quality concerns and the related risks, al lowing for timeous preventative action to be taken when required,” Paterson concludes. https://www.aes-africa.com

can be a very effective energy-saver, as it requires fewer blow-downs of the boiler to clean it out. “Typically with municipal water supply, the TDS is low, so we proceed directly to a softener. However, there are some areas in the country where the water is very hard. We look at various technologies to identify the most cost-effective way in which to manage that over the long term,” says Lund. PH control is always critical, and must remain within the right parameters to fa cilitate the formation of a protective layer to protect the internal surfaces of the boiler. Lund adds that oxygenates should also not be overlooked: “It is important to re move as much oxygen as possible before water goes into a boiler to prevent the oxygen causing pitting corrosion, especially when boilers have economisers, as there will be oxygen left in the water that will cause pitting and increase the risk of equipment failures.” Another consequence of poor water treatment is foaming. This results in liquids, instead of hot gas, being carried from the boiler into the steam piping network and flowing through the system. This can cause a condition known as ‘water hammer’. Pockets of water travel at the same velocity as the heated gas, potentially causing severe dam

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