Page 332 - Boiler_Operators_Handbook,_Second_Edition

Plants and Equipment 317

time to seriously review the instruction manual so you
understand how those burners are to be operated.

Oil Burners
Fuel oil is introduced into a burner using a burner
tip which is normally mounted on the end of what we
call an oil gun (Figure 10-51). The design and arrange-
ment of the tip and gun is dependent on the type of
atomizing system. Pressure atomizing burners have one
or more tips on the end of a pipe positioned in the burn-
er at the point where the oil has to be injected to develop
the air/fuel mix. Pressure differential, air atomizing and
steam atomizing burners need two pipes, one to convey
the oil to the tip and another to supply the air or steam
or return the oil from the tip. Traditionally the two pipes
Figure 10-50. Gas spuds are concentric with the oil supply down the center pipe
and the annular space between the two providing the
and the gas ring isn’t cast iron I would cut the flanged passage for air, steam or return oil but (like the one in
joint out and weld the piping. Gas free it before welding! the figure) some manufacturers provide two separate
There are few options for the operator when it pipes running side by side.
comes to gas rings, there’s nothing to adjust. All the The tip introduces the oil into the furnace in a way
adjustments for fuel-air mixing have to be made by al- that makes it possible for the oil and air to mix and burn.
tering the combustion air flow. There are problems you As I sit here writing this the news on television is show-
have to watch out for. Gas rings can crack due to thermal ing where the Iraqis have created large pits of oil and set
shock, warping of the front plate, and improper repairs. them afire. The smoke released from those pits is clear
The drilled openings for the gas can be blocked by dirt evidence that you have to do more to produce a clean
accumulation, careless application of refractory materi- fire. To ensure the oil and air mix and burn completely a
als (a common one), and dirt when the burner port is fuel oil burner tip provides a means for “atomizing” the
used for furnace access. The ring can come loose from oil. Atomization is breaking the oil up into tiny droplets
the boiler front plate because the mounting bolts vibrate (not as small as an atom but small enough) so the air can
loose. Any change in the appearance of a gas fire should mix in between all the droplets for complete burning. If
be followed on the next shutdown by a careful examina- the oil isn’t atomized it will not burn well. In some cases
tion of the gas ring. it won’t burn at all.
There are a considerable number of gases that are Don’t accidentally leave the tip off an oil burner
fired in boilers in addition to natural gas (see FUEL and try to start it that way. I know one apartment house
GASES in Chapter 7). In many cases they are burned boiler operator that did that; the burner didn’t light
only because the alternative is to waste them to atmo- the first few times he tried it. After several tries he had
sphere and several are considered a source of pollution.
The petroleum gases can, for the most part, be burned
in equipment identical to natural gas burners with
adjustments in nozzle size or fuel supply pressure to
compensate for the difference in the heating value and
air to fuel ratio of the gases. Others, such as digester gas,
can contain a large percentage of non-flammable gases
and require special burners that can accommodate the
larger volumes of fuel gas required to satisfy the heat
input requirements. Digester gas (from sewage treat-
ment plants) and landfill gas (tapped off a landfill) are
noted for containing hydrochloric acid so the piping and
burner has to be capable of handling the corrosive mate-
rial. As with everything else I’ve said before, take the Figure 10-51. Oil gun