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A Canadian refinery operating a 138,000 bbl/day facility near Edmonton, Alberta, was experiencing ongoing water contamination within its steam stripped ultralow sulphur diesel (ULSD) streams. Steam stripping created a stable emulsion that conventional KO devices and mesh pad liquid/liquid coalescers could not break. This case study outlines the refinery’s challenge, the AquaSep coalescer solution proposed by Pall and the operational results achieved.
Challenge
Steam stripping can be a more economical option for fractionation, but in this case, it led to the formation of extremely fine water droplets as the steam condensed in the distillate. This created a stable emulsion, which conventional separation devices could not resolve. The refinery attempted to use a horizontal mesh pad liquid/liquid coalescer from another manufacturer, but inlet and outlet samples around the device appeared identical.
As a result, the ULSD unit faced storage bottlenecks. Several days of undisturbed settling were required to reduce free water concentrations from approximately 600 ppm to 250–300 ppm, confirming that a highly stable emulsion was present. The refinery adopted molecular sieve media as a temporary measure, but the media could not be regenerated and had to be replaced when spent, leading to significant costs.
After repeated failures to correct the issue, the refinery needed a rapid, reliable, long term solution to resume production of on spec diesel.
Solution
Pall was invited in the summer of 2006 to demonstrate AquaSep® coalescer technology at the refinery. Site testing was performed to confirm sizing requirements and water separation performance. Inlet total water concentration for both ULSD streams was approximately 600 ppmv at temperatures of 30–33°C. Following treatment with the AquaSep pilot unit:
- Free water concentration in the light diesel stream decreased to 5–12 ppmv
- Free water concentration in the heavy distillate stream decreased to 3.5–10.5 ppmv
Based on the performance of the test unit, Pall recommended a combination of vertical and horizontal pre filters and AquaSep L/L coalescers for both streams. The order was placed in August 2006, and equipment was delivered shortly thereafter.
AquaSep Plus L/L Coalescer System
The AquaSep Plus L/L coalescer system is designed for liquid liquid separation and particulate removal, supporting reliable hydrocarbon and water separation.
Light Diesel Components
| Component Type | Elements |
|---|---|
| Prefilter | 77HF624G07Z BD CS HFU660FC20H |
| Coalescer | 37AQH4607B 2BD CS LCS4B1AH LS52F1H |
Heavy Diesel Components
| Component Type | Elements |
|---|---|
| Prefilter | Duplex 12HFH6603F 2BD CS HFU660FC20H |
| Coalescer | 55AQH40807B 2BD CS LCS4B1AH LS52F1H |
Following installation on December 20, 2006, the refinery reported improved clarity and stable downstream operation. The diesel treated through the new system was described as “Clear & Bright.”
Results
The refinery expressed satisfaction with the AquaSep coalescer installation, stating that “the Pall coalescer has worked as promised.” The inability to produce on spec diesel had previously been a major issue, and the new system helped resolve ongoing quality concerns.
The refinery intends to continue using molecular sieve media upstream to remove dissolved water from the ULSD, while relying on the AquaSep coalescer for free water separation. The coalescer’s performance, combined with longer life and improved separation efficiency, is expected to support reduced downtime and help the refinery operate more reliably for years to come.
Key Takeaways
- Steam stripping created a stable diesel water emulsion that traditional coalescers could not break.
- Free water levels of roughly 600 ppmv required multi day settling and expensive temporary measures.
- AquaSep test results showed reduced free water levels down to 3.5–12 ppmv depending on stream.
- The refinery restored production of on spec diesel after installing the AquaSep coalescer system.
Contact Us
If you would like to learn more about separation solutions for diesel and refinery operations, contact our filtration team to discuss your application and goals.