A >250,000 BPD Gulf Coast refinery was losing production capacity to deposition in critical heat exchangers — including the crude unit overhead trim cooler — despite a well-controlled zinc-phosphate program. The root cause was a salt the standard prediction tools were not built to see.
An open recirculating utility cooling system operating on an alkaline zinc-phosphate inhibitor program was fouling critical heat exchangers — including the crude unit overhead trim cooler — causing measurable production capacity loss.
Calcium phosphate was in control. Zinc phosphate was in control. Polymer dispersant dosages were correct by all standard benchmarks. Yet deposit analysis kept confirming significant zinc deposition, with a strong but unexplained silica component that the operating team and incumbent supplier could not reconcile.
The standard monitoring and prediction tools in use tracked zinc and silica as independent parameters — leading the team to assume they were dealing with two separate problems simultaneously.
Aligned refinery and service-company data across online and offline datasets. Conducted heat-exchanger modeling with time-series overall heat-transfer coefficient (U-coefficient) analysis to quantify fouling progression and timing.
Applied advanced competing-ion saturation modeling — accounting for all scale-forming and scale-inhibiting species simultaneously, not in isolation. Re-interpreted lab deposit analysis with a fresh lens.
Conducted onsite data collection, system evaluation and structured team interviews. Delivered a full engineering root-cause report and root-cause presentation to refinery operations and engineering leadership.
The tools and training in use tracked zinc and silica separately — so the team assumed silica was a different problem. No standard model accounted for zinc silicate as a compound salt.
At alkaline pH with 3 ppm zinc in solution, a swing of just 0.5 cycles of concentration was sufficient to exceed the zinc silicate saturation index and drive bulk deposition in the highest-temperature exchangers. Adjusting design control limits for zinc concentration, cycles of concentration, polymer dispersant ratio, and operating pH — and incorporating zinc silicate into the saturation prediction tools — eliminated the deposition entirely.
Independent cooling water program review for refineries and petrochemical facilities. No chemistry sold. No conflicts of interest. ROI typically measured in hours to days.