Closed cooling loops are used to provide the required cooling to critical industrial equipment and processes that cannot tolerate the variability from open recirculating cooling towers. The key challenges in operating a closed loop are corrosion control and microbiological growth. A new non-toxic closed loop corrosion inhibitor program was developed that does not contain nitrite, heavy metal, P, B, or filming amine. This paper will present results from recent field trials using this new digitally-enabled, sustainable corrosion inhibitor program. The first field trial was conducted at a refinery in the Middle East that provided an opportunity to evaluate the new program in a hot loop (>90 °C) that experienced upsets and hydrocarbon ingress. A second field trial was conducted at a steel mill in Europe with a significantly more challenging makeup water that included moderate chloride and no hardness. Positive results from both field trials will be presented that will include coupon weight loss measurements, dissolved Fe concentration, and product actives monitoring


An emerging market driver in industrial water treatment is the move to more sustainable chemistries. Corporate sustainability goals are becoming more common and more stringent. Customers are turning to water treatment companies for innovative solutions that can satisfy their sustainability goals and not sacrifice performance or asset integrity. Indeed, a major trend in evaporative open cooling water treatment is to move away from heavy metals such as zinc and other environmentally questionable materials such as phosphates. Another area of cooling water that is in need of a sustainability refresh is closed cooling loops. The most widespread closed cooling treatment programs are based on combinations of nitrite, molybdate, and borate. All three of these chemicals have regulatory, discharge and/or SH&E concerns.1,2

Like open cooling towers, closed cooling loops provide cooling to critical operations, but with no cycling or evaporative losses. Key challenges in operating a closed loop are corrosion and microbiological growth. Scale is not typically a concern in closed loops since the makeup waters are usually softened. In addition to nitrite and molybdate, some treatment options exist that are based on phosphorus or filming amines,3,4 but nitrite and molybdate have been and remain the most widely used.5 Although scale is not a concern in closed loops, the chloride content in the loop has been shown to be the primary driver of corrosion. Chlorides can enter the closed loops either from the makeup water, or from leaks in seawater cooled heat exchangers. For example, refineries in the middle east are prone to such chloride ingress. Such spikes in chloride concentration can prove problematic for less robust closed cooling options such as molybdate and filming amines. As such, a market need has emerged for a reliable, robust, and sustainable closed cooling treatment program.

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