Can FO be used to fuel IC engines? Is a very interesting query!!
Let us first understand what is FO? In the India context Furnace Oil or FO is a residual blended fuel available in a number of viscosities. Furnace Oil is a blend of residual fuels generally offered in different viscosities and its nomenclature indicates its viscosities, LV= 80 cSt (80 cSt @50 oC), MV1= 125 cSt, MV2 = 180 cSt and HV 370 cSt. Its Flash is 66 oC. As it is a residual fuel,( has high viscosities) and its costs is very low, BUT, has very high Sulphur (4 to 5%), and thus preferred by many bulk users to fuel their (Low RPM large engines) at the Captive Power Plants (CPP). Typically large engines sub 450 RPM engines made by Wartsila, MAN, Pielstick, etc.. typically as 18V32 or 36 that can generate upto 8 to 10 MW or more.
On the other hand, medium RPM engines upto 750 RPM can be fuelled by LDO as in some CPP’s, HEMs, Off The Road vehicles, Agriculture vehicles etc.. These have medium viscosities 2 to 15 cSt@40 oC. flash of 66 oC and a Sulphur level below 2%.
Most of the commonly available commercial applications use engines with above 800 and generally between 1100 to 1500 RPM ( and increasing RPM’s available nowadays) and use the popular High Speed Diesel (HSD). These have a Flash Point - 35 to 36 oC and most important viscosities of 2 to 5 cSt. And under Euro IV (BS 4) regimes 50 ppm Sulphur. Thee have centane value between 48 – 51.
TYPICAL SPECIFICATION OF FUEL OILS
Properties Furnace Oil LS.H.S. L.D.O. HSD
Density (Approx. g/cc at 15°C) 0.89–0.95 0.88–0.98 0.85–0.8 0.82 -0.85
Flash Point (°C) 66 93 66 34 - 35
Pour Point (°C) 20 72 18 3 - 15
G.C.V. (kCal/kg) 10,500 10,600 10,700 10,800
Sulphur Total, % Wt. Max. Upto 4.0 Upto 0.5 Upto 1.8 0.5
In summary, FO may be used in CPP where selected slow speed sub 500 rpm engines are installed.