Finnish refinery Neste has successfully tested two new oil products which it believes will help shipowners manage the transition to IMO 2020
The upcoming sulphur cap has set off a churn in the shipping industry. From 1 January 2020, ships will no longer be able to use bunkers with more than 0.5% sulphur by mass – a drastic reduction from the current 3.5% cap mandated across much of the world. Various compliance mechanisms include: use of distillate fuels, such as marine gas oil or blends of distillates and heavy fuel oil (HFO); installing scrubbers to treat the exhaust gas; and using alternative fuels, such as liquefied natural gas. These options all come at a cost and pose technical challenges, such as fuel handling.
For instance, distillates have poorer lubricity and much lower viscosity than HFO, while marine diesel engines and their auxiliaries are designed predominantly for the parameters of HFOs.
Another option involves the use of low-sulphur heavy fuel oils that come close to the properties of HFOs, in terms of viscosity and flash point. The impact of such fuels on the performance of marine engines, however, must first be studied and qualified.
Neste, a refiner with facilities in Porvoo and Naantali, Finland, has tested two residual fuel oils – one with 0.1% sulphur and another with 0.5% sulphur – along with a low-sulphur marine diesel oil product on a Wärtsilä Vasa 4R32. Its researchers report that no problems were encountered in fuel handling during the tests.
At loads 50% and higher, engine performance was nearly the same across all three oil products. Variations in performance and emission parameters were significant at lower loads, such as 25% and 10%. The 0.1% sulphur and 0.5% sulphur oils had slightly inferior ignition properties compared to the distillate. The dual-fuel test engine was more sensitive to fuel ignition properties than a similar engine optimised for heavy fuel operation.
The results were presented at the CIMAC Congress 19 held at Vancouver this year in a paper titled, Effect of Sulphur Content on Bunker Fuels’ Performance in a Medium-Speed Engine*.The test engine, a Wärtsilä Vasa 4R32 (cylinder diameter: 320 mm, speed: 750 rpm, brake power: 1,640 kW), was connected to a braking generator at Finland’s state-owned VTT Research Laboratory. The test cycle consisted of five loads between 90% and 10% of rated power.
The engine was run from 16 to 18 hours with each fuel during the tests. Weather conditions changed during the tests, which affected performance, the paper noted.
The distillate fuel has the commercial name of DMB. Neste has called the two residual fuels RMG 0.1% S and RMG 0.5% S. The measured efficiency of the engine was almost the same for DMB and RMG 0.1% S.
Ignition properties of RMG 0.5% S were poorer compared to the other two products, but the variations were significant only at the lowest loads. At loads other than 10%, the 0.1% S product yielded the highest NOx levels.CO emissions varied more at low loads. As expected, the heavier product yielded higher CO2 emissions; the trends were similar for particulate matter.
For DMB, sulphur dioxide levels in the exhaust gas were much higher than the values calculated from fuel analysis.
This indicated that there was still residual high-sulphur fuel content in the fuel handling equipment. Before this test, the fuel handling equipment was flushed and about 1,000 dm³ of DMB was run to the engine. The researchers note this arrangement was likely insufficient. RMG tests did not encounter these problems. SO2 concentrations were some 15% higher for RMG0.1% S and 5% higher for RMG 0.5% S compared to calculated values. In absolute terms, the deviation was 2.8 ppm with the 0.1% S product and 4 to 6 ppm for the 0.5% S. These variations were attributed to inconsistencies in the measuring device.
*Sami Nyyssönen and TuulaKajolinna of VTT Technical Research Centre of Finland, and MerjaKouva, Esko Karvinenand Jukka Nuottimäki of Neste Corporation