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This case study is related to applying an Alfa Laval diesel centrifuge for the large-scale recovery used diesel fuel that is used for washing crude oil railcars.
Railcars transporting crude oil need periodic cleaning. This is to remove accumulated sludge, waxes, etc. Diesel fuel is often used as the washing fluid for rail car cleaning. One facility used approximately 10,000 gallons of fresh diesel every day.
Reusing the spent black diesel was desirable but not workable due to the water and sludge contamination of the diesel. The facility owner was familiar with the Alfa Laval diesel centrifuge for diesel purification from his service in the navy.
The owner contacted Dolphin Centrifuge to explore the possibility of using one of our industrial centrifuges to purify the spent diesel and reuse it.
The customer had sourced a chemical additive. This additive would drop out some of the impurities into a heavy ‘black phase’. The heavy phase would drop out over time.
Finally, they removed this separated phase by decanting. This was a time-consuming process. It required manual labor and considerable tank capacity for decanting.
Dolphin Centrifuge recommended testing of the chemical diesel mix. We tested the mix in our in-house testing facility with our pilot-scale disc centrifuge.
We mixed the desired ratio of the customer-provided chemical into the black diesel. The mixed fluids were then processed through our pilot scale, a disc-stack centrifuge.
The diesel purifier separated the heavy phase and produced a stream of clear diesel. The separated heavy phase was flowing out of the heavy phase outlet. The customer got the purified diesel analyzed for impurities and water.
| Parameter | Before Centrifuge | After Centrifuge |
| Water | 12% (v/v) | 0.05 % (v/v) |
| Sludge | 5.8% (v/v) | 0.06 % (v/v) |
The analysis results showed diesel with less than 0.12% impurities. This was definitely reusable to clean out rail cars! The customer awarded Dolphin a contract to build a 40 GPM diesel fuel purifier system.
The featured image on the top of the page shows the system manufactured by us. The system included a chemical injecting port designed by Dolphin. We also integrated a dynamic mixing system on the inlet feed line to the centrifuge.
Integration included electrical and mechanical aspects of the mixer. We also integrated Flow-meters into the diesel and chemical lines. We used a PID loop to control both pumps to check and ensure a consistent diesel to-chemical mix.
Dolphin Centrifuge’s engineering team did the site installation and commissioning. The system recovered the daily volume of used diesel during the night shift.
The customer reuses the diesel 2~3 times before refreshing the wash diesel stock. This resulted in annual savings of over $2M! The diesel centrifuge module paid for itself within the first month!
| Centrifuge Model | Alfa Laval WHPX 510 3-Phase; Self-Cleaning; Disc Stack Centrifuge |
| System Options | VFD Control PD Feed Pump |
| Chemical Mixer with Chemical Dosing Pump | |
| Automatic PLC/Touch-Screen Control Panel | |
| Sludge Tank with Sludge Disposal System | |
| Clean Diesel Tank with Return Pump |
Contact Dolphin Centrifuge for pricing information or to discuss your specific application. We have a large inventory of diesel fuel centrifuges for sale.
by Sanjay Prabhu MSME
Engineering Manager, Dolphin Centrifuge