Blow Away Your Soot!

A boiler that has been running for a long time is sure to
have soot deposits on its tubes and furnace.

This is especially prominent in boilers using heavy fuel oil
for burning. Although the fuel will be heated and filtered
before combustion, it still contains a lot of impurities. The
by-products of combustion as well as imperfect combustion
cause the soot to form. The soot is deposited on the heating
surfaces.

During the combustion of the fuel oil in a steam boiler, hot
gases are formed. These hot gases are used to heat up the
water in the boiler to form steam.

With the deposits of soot, a lot of the heat energy is not
able to be transferred to the water, but instead is lost
through the chimneystack. The soot layer acts as a heat
insulator for the tubes and shells of the furnace. The heat
is unable to reach the water.

This not only causes the boiler efficiency to be lowered,
but a more serious problem can also occur. The soot can
catch fire!

A soot fire can be detrimental to the strength of the boiler
because it can cause serious localized hotspots to occur at
the tubes. These localized hotspots can even reach temperatures
that weaken the materials of the tubes.

Soot blowers are installed to blow away these soot deposits.
Steam is normally used as a medium for blowing away the soot.

The operation of the soot blowers goes like this:

1. Steam is channeled to the soot blower pipeline.
2. The operator of the soot blower will open a drain valve
to drain off any water in the steam. This is to make sure
that the steam going through the soot blower is dry.
3. Once the steam is considered dry, the drain valve is shut
off, and the soot blower is turned. Most soot blowers are
constructed in such a way that when it is rotated, a steam
port is uncovered and steam can enter into it.
4. The steam shoots out from the soot blower tube that is
inside the boiler fireside. Many small holes for the steam to
emerge are drilled along the length of the tube. As the tube
rotates, the position of the steam jet will also move with it.
After a full rotation, all the areas around the soot blower
tube should be clear of soot. (However, it depends on how
thick the soot is, the speed at which the soot blower is
rotated, and how efficient the soot blowing is)
5. After completing the soot blowing, the steam supply is shut
off again.

The operation of the soot blower can be done manually or by
remotely controlled motor drive. A motor driven soot blower
will usually include some means of turning manually in case
the motor fails.

The soot that is blown away from the heat transfer surfaces of
the boiler will be carried together with the hot gases out
through the chimneystack.

If there is a dust collector, the soot will be caught
by it, otherwise it goes out to the environment as particles
of carbon and ash.

Folks, hold your breath!

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