SPECIFIC ENERGY CALCULATION :

Specific energy can be calculated with a degree of accuracy sufficient for normal purposes from the density of the fuel and the application of corrections for any sulphur, water and ash that are present.

Gross Specific Energy (MJ/Kg) =

(52.19 - 8.802 P² . 10-⁶) x [1 - 0.01 (x + y + s)] + 9.42(0.01 S)

Nett Specific Energy (MJ/Kg.) =

(46.704-8.802 P². 10-⁶ + 3.167.P10-⁶) x [1 -0.01(x + y. + s)] + 0.01(9.42S - 2.449x)

Where P = density at 15°C in Kg/m³

 x = water content expressed as a percentage by mass.

 y = Ash content expressed as a percentage by mass.

 s = Sulphur content expressed as a percentage by mass.

As illustrated in the figure, with a density of 987 Kg/ m³. 2.5% sulphur and 0.02% water to give a net specific energy of 40.37 MJ/Kg. If required, the slight effect of. ash may be taken into account by subtraction of .0.02 MJ/Kg for each 0.05% wt. of ash. Typically the ash value is in the order of 0.03 - 0.1% by wt.

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