As the
specific gravity and the viscosity of fuel oils increase, the sediment level,
which originates primarily from transport and storage contamination, will
increase as a result of a slowing of the natural settlement process. As both
the water and sediment content of heavy fuel oil increase, the usable energy in
the fuel decreases.
The
moisture in fuel oil when burnt is converted
into steam, which then carry the heat to the chimney & is a direct loss to
boiler. Also too large moisture content sometimes result in lowering of
the burning temperature, improper combustion, choking of burner tips
and erosion & corrosion of boiler parts like Air preheater, ID
fan, chimney internal, ducts etc.
Water
content of 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. Water
may be present in free or emulsified form and can cause damage to the inside
furnace surfaces during combustion especially if it contains dissolved salts.
It can also cause spluttering of the flame at the burner tip, possibly
extinguishing the flame and reducing the flame temperature or lengthening the
flame.
Sediments
in fuel oil are nothing but incombustible which lowers the calorific value of
fuel, choke burners & form slag & deposits on the outer surfaces
of the various tubes thereby lowering the heat transfer.
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