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DEFINITION
:
A dark viscous residual fuel
obtained by blending mainly heavier components from crude distillation unit, short residue
and clarified oil from fluidized catalytic cracker unit.
NOMENCLATURE
Bunker fuel, furnace oil ,
Fuel oil are other names for the same product. Though Fuel oil is a general term applied
to any oil used for generation of power or heat, Fuel oil can included distillates and
blends of distillates and residue such as Light Diesel Oil.
SPECIFICATION
Furnace oil in the current
marketing range meets Bureau of Indian Standards Specification IS : 1593 - 1982 for fuel
oils, grade MV2.
VISCOSITY
Viscosity is the most
important characteristic in the furnace oil specification. It influences the degree of
pre-heat required for handling, storage and satisfactory atomization. If the oil is too
viscous it may become difficult to pump, burner may be hard to light and operation may be
erratic. Poor atomization may result in the carbon deposits on the burner tips or on the
walls. The upper viscosity limit for furnace oil is such that it can be handled without
heating in the storage tank is excepting under server cold conditions. Pre-heating is
necessary for proper atomization.
FLASH POINT
As per the Controller of
Explosives classification, Furnace oil falls in the class "C" category with
minimum flash point standard of 66 deg. C. Since Penskey Martens Closed Cup method is
used, it is apparent that a small quantity of low boiling point hydrocarbons is sufficient
to lower the flash point drastically.
POUR POINT
It is a very rough indication
of the lowest temperature at which Furnace Oil is readily pumpable. In the specification
the pour point of Furnace oil is not stipulated. However, for Furnace oil manufactured
indigenously and for imported parcels, the pour point is such that current supplies
normally can be handled without heating the fuel oil handling installation.
WATER
Water may be present in free
or emulsified form and can on combustion cause damage to the inside furnace surfaces
especially if it contains dissolved salts. It can also cause sputtering of the flame at
the burner tip. Water content of furnace oil when supplied is normally very low as the
product at refinery site is handled hot and maximum limit of 1% is specified in the
standard.
SEDIMENT
Furnace oil being a blend of
residues contains some quantity of sediments. These have adverse effect on the burners and
cause blockage of filters etc. However, the typical values are normally much lower than
the stipulated value of maximum 0.25 percent, by mass.
ASH
Ash is incombustible component
of the furnace oil and is expressed as a percentage mass of the furnace oil sample. Ash
consists of extraneous solids, residues of organometallic compounds in solution and salts
dissolved in water present in the fuel. These salts may be compounds of sodium, vanadium,
calcium magnesium, silicon, iron etc.
Ash has erosive effect on the
burner tips, causes damage to the refractories at high temperatures and gives rise to high
temperature corrosion and fouling of equipments.
SULPHUR
Sulphur determination includes
burning of known quantiy of oil, treating the sulphur oxidation products formed during
combustion and weighing of sulphur in the form of sulphate.
The sulphur di oxide may come
in direct contact with the product during the combustion process and may create adverse
quality effects in the product.
CALORIFIC VALUE
Calorific value of a fuel is
the quantity of heat generated in kilocalories by complete burning of one kilogram weight
of fuel. Gross calorific value is higher than net calorific value to the extent of heat
required to change water formed by combustion into water vapours.
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