Chemical Engineering November 2014 - 44

Cover Story
rial that could decrease the effective
port size. If the ports become
partially or completely plugged,
the quantity and distribution of
fuel entering the burning zone may
vary from the design objective, and
combustion problems may occur.
The type of material plugging the
ports determines how it should be
cleaned. Foreign material must be
carefully removed from the fuel
orifices so as not to affect the orifice
dimensions. Fuel tips should
be replaced if any orifices exceed
the specified diameter by more
than one to two twist-drill sizes.
If the material is not easily removed,
some cleaning guidelines
should be followed:
* Soak the burner part in a solvent
to loosen the deposit
* Use a twist drill to remove the
deposit. Never use a power tool
with the twist drill because it is
likely to enlarge the ports
* Use a welder's file to gently remove
the scale from the orifices.
If the scale cannot be removed,
the fuel tip or orifice must
be replaced
* Use wet steam or hot water if the
source of the foreign material is
an amine compound, because
amines are water-soluble
* Shut down the fuel gas valve
and inject steam into the burner
if the amine plugging occurs frequently
without removing the
burner. Note that injection cleaning
may not clear all tip ports
equally
* Soak the tips in a hydrocarbon
solvent, followed by cleaning
with a twist drill if the tips are
plugged with polymers
* Remove the coking, polymer or
solid deposit by oxidation in a
small, high-temperature furnace.
Many tips can be cleaned at the
same time with this technique
Oil tip and atomizer. Fuel-oil
tips are harder to maintain than
gas tips and require more frequent
cleaning. Tips in light fuel-oil service
may have only a slight carbonlike
deposit on the surface. To clean
fuel-oil tips, do the following:
* Use a wire brush to remove
slight carbon-like deposits. Tips
in heavy fuel-oil service will usually
have stubborn hard deposits
on the surface and in the ports
* Use steam cleaning or a twist
drill, in combination or individually,
to remove harder deposits.
It is not recommended to use a
power drill or tool to clean ports
or oil tip surfaces, as any nick or
notch on the oil tip's surface acts
as a site to collect oil and accelerate
tip-coking problems
* Soak the tip in a solvent, followed
by blowing steam through
the orifice to remove the remaining
oil or solid deposits
* Handle the atomizer carefully
when removed from the oil gun
to protect the labyrinth seal.
This seal separates the oil from
the steam by a series of rings on
the atomizer with a tight tolerance
between the atomizer and
the gun body. If the atomizer is
continuously getting stuck and
cannot be removed from the gun
without breaking the atomizer,
the metallurgy may be at fault.
In this case, it is recommended
to exchange the atomizer metallurgy
with a different metallurgy
than that of the oil tip
Burner tiles. The unique profile of
a burner tile's surface is challenging
to reproduce, making tiles difficult
to fix and return to service successfully.
Also, the refractory of the
tile undergoes phase transformation
while in service, and refractory
repairs usually do not adhere to the
surface for very long periods of time.
Burner tiles should be replaced if
they experience any cracks or deformations.
Especially of concern
are major cracks, mainly in wall- or
roof-mounted burner tiles, where
the tile pieces are expected to fall.
Also, one should look carefully for
multiple cracks in a section, which
present evidence of crushing due to
restrained expansion, and are reason
for replacement. The primary
or oil tile shall be checked as well.
If it is badly pitted or cracked, the
recirculation of gases within the
tile is uneven, and coking can occur
on the tile. This coking can lead to
oil dripping and spilling from the
burner. If this is observed, the tile
44 ChemiCal engineering www.Chemengonline.Com noVemBer 2014
must be removed and cleaned.
Flame stabilizer. Different
flame-stabilizer designs are used
to maintain a stable flame in the
combustion zone. For natural-draft
burners, these designs take into account
the diffuse cones, ledges and
tapered tiles of the burner. Poor
conditions or the absence of a stabilizer
can result in unsatisfactory
flame shape or an unsafe flame that
can lift off the burner and leave the
zone where combustion is initiated.
Operations suffer when part of the
flame lifts off the burner due to a
damaged stabilizer because irregular,
erratic flame patterns occur,
and new risks are introduced into
the process. A damaged stabilizer
must be replaced.
Air registers and dampers. All
registers and dampers should be
exercised periodically to ensure
that they are functional. If dampers
are inoperable, check the actuator
and repair if necessary. Dampers
are often inaccessible during
operation and repairs must wait
until the equipment has been shut
down. Clean the register of foreign
materials, spilled oil, sand, rust and
insulation that blocks airflow. If the
register is deformed, possibly due
to incorrect operating procedures,
or the operating handle is broken,
repair or replace the part.
Pilot burners. The most common
pilot burners used in the CPI are
small, heat-release pre-mix burners.
The basic parts of these pilot
burners include the pilot tip, gas
mixer, mixing tube and orifice. The
gas orifice is commonly 1/16 in. in
diameter and can be easily plugged
by pipe scale. This element is
cleaned by hand with a twist drill,
as previously described. If inspection
reveals a damaged pilot tip,
the tip should be replaced.
Flare pilot burners. When the
flare system is in service, monitor
the supply pressure and clean the
fuel strainers, knockout pots and
drains that are accessible from
grade. When the flare system is
not in service, it is recommended to
clean the strainer upstream of the
orifice and to inspect the orifice.
Flame-front generators require
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Chemical Engineering November 2014

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