Chelants like EDTA and NTA are essential tools in water treatment, offering versatile applications across steam boiler programs, closed circuit systems, and wastewater treatment. These powerful agents play a critical role in solubilizing and dispersing metal ions, preventing their re-deposition and ensuring system integrity. Additionally, phosphonate and polymer-based sequestrants are commonly incorporated into a wide range of products, including closed circuit inhibitors, RO scale inhibitors, cooling tower treatments, and more.
Our premium pre-commission cleaners, Multitreat KQ2007, and Multitreat DE, are expertly formulated with a blend of chelants, sequestrants, surfactants, buffering agents, and polymers. These advanced products are designed to deliver optimal cleaning performance, effectively removing debris and corrosion deposits from closed circuit systems, ensuring your systems are clean and ready for operation.
Why Chelants and Sequestrants Matter
In closed-circuit heating and chiller systems, chelants and sequestrants are often formulated into pre-commission cleaners and flushing chemicals to control and remove metal ions, particularly Fe3+ (ferric iron) and Fe2+ (ferrous iron). When significant corrosion deposits have built up, using a chelant-based cleaner is critical for effective cleaning and maintaining system efficiency.
Choosing the Right Chelant-Based Formulation
Selecting the appropriate chelant formulation is vital for maximizing cleaning effectiveness. It’s essential to understand that chelants like EDTA and NTA have different stability ranges, affecting their performance in removing corrosion deposits at various pH levels:
- EDTA: Present in Multitreat KQ2007, is effective in chelating ferric iron (Fe3O4) from pH 2 to 10, with an optimal range between pH 3 and 6. It retains about 50% of its chelation capacity up to pH 10.
- NTA: Present in Multitreat DE, works best for chelating ferric iron (Fe3O4) between pH 2 and 4, with an optimal pH around 3. NTA also retains 50% of its capacity up to pH 8.
These pH ranges must be considered when calculating iron saturation limits for specific formulations. Most pre-commission cleaners also contain phosphonates, which chelate iron effectively around pH 10, adding complexity to the calculation of maximum iron saturation levels when combined with EDTA or NTA.
Optimizing the Cleaning Process
As the cleaning process progresses and iron oxide is removed, the pH of the solution will naturally rise. NTA-based formulations start at a pH around 5 and are most effective up to pH 8, while EDTA formulations start at pH 7.5 and work well up to pH 10. If the pH exceeds these ranges, it may need to be reduced by adding more cleaner or a carefully formulated acidic product like Closed-circuit buffer pH 5.1.
Iron plateau levels for Pre-commission cleaners can be calculated but it must be borne in mind that these calculations are theoretical. At 1% concentration and pH 10 Multitreat KQ2007 will have an iron plateau level of 600ppm whereas at 1% concentration and pH 8 Multitreat DE will have an iron plateau level of approximately 2000ppm.
It is important to remember that chelants also bind to other metals such as copper, calcium, and magnesium, and that the speed of the cleaning process is influenced by temperature. According to BSRIA BG29 guidelines, a chemical clean can take between 12 to 72 hours, so allocate sufficient time to ensure a thorough clean.
Maximizing Effectiveness and Efficiency
For optimal results, maintain the pH within the recommended range which is generally pH 5 to 8 for NTA-based cleaners or pH 7 to 10 for EDTA-based cleaners. If iron levels plateau, it’s generally advised to add more cleaner, allow the system to circulate for at least another hour, and then re-test. Consistent iron levels after three tests indicate that the iron plateau has been reached, signalling the completion of the cleaning process.
Interested in finding out more?
If you would like to discuss any of the above methods or to learn more about our Systemtrace CC product, please contact our technical department on 01327 709439 or ownlabel@bvwater.co.uk
