A Mid-Continent refinery processing significant volumes of heavy Canadian bitumen-based crude. Processing this opportunity crude resulted in frequent desalter upsets caused by asphaltene precipitation and oil coated solids, which generated high oil & grease (O&G) content in the desalter effluent brine (see Figure 1).
These upsets were causing significant challenges at the wastewater treatment facility. To prevent exceeding the plant’s O&G discharge limit, the opportunity crude rates had to be reduced along with crude throughput curtailment.
A solution was required which would allow for more crude blending flexibility of opportunity crudes without causing desalter upsets and excessive amounts of O&G in the effluent brine. Previously, three trials by various competitive process treatment companies had already failed to improve the situation.
To design a chemical treatment program that would maximize opportunity crude processing without upsets or generate oily effluent brine from the desalter, SUEZ conducted field simulations and lab work with multiple samples over several months.
This in-depth qualification sample protocol assisted with building a robust program across variations in crudes, crude blends and process parameters.
SUEZ was confident that the innovative treatment solution proposed would solve the challenge under all modes of operations. This included desalter continuous mud-washing, which was of critical importance to maintain desalter cleanliness.
Figure 1 – Brine effluent without treatment (left) and with SUEZ treatment (right)
Result
Within the first few hours of initiating Veolia’s patent-pending treatment program, the emulsion layer in the desalter was reduced by ~30%. At the same time, the desalter’s effluent brine oil & grease content was reduced by over 95% (see Figure 2).
The two years prior to Veolia’s solution, O&G in the effluent brine averaged 1,900 ppm, and included three trials by competing process companies that had failed to produce results.
The first year of operation with Veolia’s solution resulted in an average O&G level in the effluent brine of 75 ppm: a decrease of 96.1%.
Additionally, the wastewater discharge limit of 100 ppm O&G was achieved greater than 99% of the time, with a pump failure being the only reason for the observed single off-spec brine result.
The refinery determined that the ability to blend higher ratios of opportunity Canadian crude was worth at least $1.5MM/year.
Moreover, the Veolia patent-pending solution represented several other significant process improvements, including:
- Stable desalter operation with a lower operating cost:
- Flexibility to increase salt & solids removal with greater oil/water mixing with reduced chemical consumption
- Cleaner desalter due to continuous mud-wash at design flow rates
- Stable and higher performance at the wastewater treatment plant operation with lower operating cost
- Reduced energy and maintenance cost from lower fouling of crude preheat exchanger and furnace
- Lower crude tower overhead chlorides enhancing asset reliability and reduced overhead chemical treatment cost
- Reduced slop oil recovery and reprocessing cost
Figure 2 – Desalter brine effluent oil & grease before and after Veolia’s patent-pending treatment