A few words about firing waste oil in a boiler furnace.
Is the sludge a waste oil just to get rid of or is it a valuable
fuel?
Well, it’s both. It’s waste oil that you want to get rid of, but it
contains energy that you ought to utilize.
The waste oil has to be conditioned to form a smooth emulsion with between 20%
and 30% of water. Circulating the content of the sludge service tank with a
large pump and, if necessary, add some water will be a useful method. The
percentage of water might be measured by means of a capacitive electrode in the
pipe downstream the circulation pump. The measuring method has some
disadvantages, but it works.
The temperature of the emulsion should be adjusted to achieve the viscosity
recommended by the burner maker, but it mustn't exceed the boiling point of the
water.
It’s normally difficult to fire pure sludge; it has to be mixed with
normal fuel oil. The sludge/fuel oil ratio depends on the sludge quality. With
a really poor sludge you can only fire about 10% sludge. With a better,
well-mixed sludge the ratio could be much higher, but the burner has to be
continuously supervised, since it’s very difficult to get a homogeneous
sludge-mixture and the air demand may change suddenly.
There is no problem to fire sludge with this method. The problem is that sludge
contains a great portion of ash and nonburnable sediments that accumulates on
the surfaces of the furnace.
Increased soot-cleaning is strongly advised.
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