Nov-2024

Optimised coagulant programme helps refinery to increase water reuse and reduce energy use (ERTC 2024)

Water scarcity poses a challenge to the petroleum refining industry, impacting operational efficiency and sustainability goals.

Caroline Bird
Solenis

Article Summary

Refineries, and other water-intensive operations, rely heavily on clean water for essential processes. The global stress surrounding water usage and availability continues to grow as water costs increase and regulations become stricter. Multiple areas around the world have seen drier seasons that have caused additional stress on local water supplies. In drought-stricken areas, industrial operators need to be more conscious of water management, trying to reuse as much water as possible.

Wastewater treatment plants at a refinery pose an opportunity for managing water and mitigating negative environmental impacts. These plants are designed to treat various streams of wastewater from all of the processing units at a refinery. By effectively treating wastewater, refineries can enhance operational efficiency by reusing water and reducing freshwater intake. Wastewater treatment plants serve as integral components in the sustainability and operational reliability of a refinery.

Case study: Water and energy savings in a European refinery
Solenis has been working with a large petroleum refinery in Europe in a drought-stricken area. The refinery has two wastewater treatment plants that discharge wastewater into the sea. The wastewater treatment plants consist of a dissolved air flotation (DAF) system and a secondary biological process.

Customer challenge
The refinery wanted to implement circular solutions to increase the amount of water that was recycled. However, its ability to do so was limited by its use of a ferric chloride coagulant. This inorganic coagulant did not allow for optimal sludge separation or water quality.

Coagulants are one of the most important chemical solutions used in a refinery as a first step in wastewater treatment to reduce organic matter and suspended solids. The selection of an appropriate coagulant is a critical decision that depends on multiple variables. A good alternative for inorganic coagulants is organic coagulants. These can improve operations and support sustainability goals, optimise chemical dosage, decrease volume of produced sludge, and help with pH control.

Solution analysis
After extensive lab analysis, Solenis recommended that the refinery switch its existing ferric chloride coagulant to ChargePac™ 312, a proprietary liquid coagulant product. This is an organic coagulant that provides high clarity and enhances flocculation. Using it would allow for lower consumption rate, at a rate of 12 to 1, and would have a positive impact on the sludge production.

As shown in Figure 1, a settling test provided better sludge separation and water clarity results using the new coagulant than the incumbent ferric chloride coagulant. Figure 2 shows that the amount of sludge produced using the new coagulant, pictured on the right, was significantly less than that produced using the ferric chloride coagulant.

Results
The conversion to the ChargePac 312 coagulant was a success; the wastewater treatment plant and the refinery began to see positive results in less than 20 days. Because the new coagulant used a much smaller dosage, the amount of coagulant fed was reduced twelvefold.

After the plant converted to the new coagulant, vast improvements were seen in the biological reactor. The chemical oxygen demand (COD), nitrogen, and phosphate levels were balanced to the right proportion (i.e., 100:5:1). The solids loading was also decreased by more than 50%, as shown in Figure 3, thereby optimising the COD reduction efficiency. Improving the efficiency of the biological reactor improved aeration, allowing the refinery to reduce its energy consumption by 113,880 kWh/year, equating to an energy cost savings of $24,000/year.

Overall sludge production and related transportation costs were reduced by 20-25% per year, which also helped the refinery lower its carbon dioxide emissions. Furthermore, because of the greater dewatering performance of the ChargePac 312 coagulant, the amount of recycled water that was reused in the refinery was increased fivefold. Lastly, due to these positive impacts, the discharge water to the sea improved. The increase in the quality of water also created a margin for water reuse for the refinery.

Overall, the change to the new coagulant improved the performance of the entire treatment process. The refinery now has effluent parameters with a higher contingency buffer. This reduces risk to fail on environmental compliance and makes water reuse possible. Notably, the refinery’s water reuse increased more than five times.

Recognition
Through its collaboration with Solenis, the refinery received a Solenis Sustainability Award in 2023. The award recognises projects that deliver reduced water use, reduced energy consumption, decreased greenhouse gas emissions, optimised raw material utilisation, or reduced waste. This award was granted on the basis of the meaningful process improvements that positively affected the refinery’s water use and environmental impact.

Conclusion
Coagulants are a crucial part of any wastewater treatment programme. Choosing the best coagulant programme for this refinery allowed the wastewater treatment plant to achieve superior sludge separation and improved water quality for reuse applications and effluent discharge. Solenis’ team of experts helped design a treatment programme that optimised coagulant dosage to obtain optimal results for this refinery. As demand for water increases, especially when it is a scarce resource, the successful use of the most appropriate coagulant will become a vital part of every wastewater treatment programme.

This short article originally appeared in the 2024 ERTC Newspaper, which you can VIEW HERE