Seminar Topic on Fuels


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Types of fuels

Presently crude oil is most sought after for marine use.
Broadly classified into three types:
a) Paraffin base: residue > 5% paraffin wax.
b) Asphalt base: contains <2% paraffin wax and mainly composed of asphalt. (Naptha)
c) Mixed base: paraffin wax >2% <5% mixed intimately with asphalt.
The type obtained depends on the source and also determines the type of refining necessary and nature of end products produced.
Paraffin and gas oil are known as distillates, which are free flowing, easily stored and can be used without free treatment.
Residual fuels are very viscous at normal temperatures and require heating before use.
Also in some cases blending or mixing of the various oils is done to provide a range of commercial fuels for different duties.

Presence of Various Salts

Vanadium and Sodium
Present in crude oils in an soluble form.
Levels present depends on the crude oil source oil, with those from Venezuela and Mexico having the highest.
Levels also related to the refinery process.
Most residual fuels contains less than 150 mg/kg
Maximum may be 400 mg/kg.
Fuel delivered contain less than 50 mg/kg.
Presence of sea water increases this value approximately by 100 mg/kg for each percent of sea water.

Aluminium and Silicon

Indication of Aluminium represents the potential presence of catalytic fines.
Fines are particles of spent catalyst that arise from catalytic cracking process in refinery.
Fines are in form of complex alumino-silicates.
Size and hardness depends upon catalyst used.
EFFECTS
The abrasive nature of fines can damage fuel pumps, injectors, piston rings, and liners.
Concentration more than 30 mg/kg, can cause damage to machinery.
Difficult to remove by centrifuging.