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 Rise in flue gas temperature due to deposit buildup, on heat transfer
surfaces.
Substantial ash buildup in the fire box, deposits on boiler tubes,
and fly ash.
Figures 3-6 and 3-7 show typical deposits that developed on a fire-tube
boiler after burning FOR for about 3,800 hours. Figure 3-8 shows similar
deposits on the water tubes in the fire box of a water tube boiler after
burning waste oil. White and green flaky deposits are usually seen on the
boiler surf aces. These deposits are made up of compounds of aluminum,
zinc, silicon, phosphorous, calcium, iron, and copper. They were believed
to be from detergents, dirt, and rust picked up in the reclamation
process. These deposits are easy to clean and have no adverse effects on
the boiler.
Because of the usually high noncombustibles and contaminants, ash
deposit problems resulting from burning used lubricating oil blends increase
with its concentration. To minimize maintenance, a concentration of less
than 25 percent used lube oil in the blend is recommended.
Waste oil or FOR should be drawn at a level at least 12 inches above
the lowest point or the bottom of a tank. Otherwise, sediment and water
settled at the bottom of the tank may be drawn into the fuel system to
cause excessive wear of fuel pumps and nozzle tips, inoperative valves, and
plugged strainers and flow passages.
Even though the waste oil cannot be expected to meet the standard
specification of fuel oil, it can be used satisfactorily, provided some
precautions are taken. Synthetic- and chemical-based liquids may be
hazardous in handling and burning. These materials must be segregated at
the source of generation or collected and disposed of according to NAVSUP
Publication 4500: Consolidated Hazardous Item List. Identification of
these liquids is discussed in Chapter 2. It is necessary that the waste
oil be free from halogenated material to prevent toxic gas emissions and
accelerated corrosion of the fire side surfaces of the boiler. Testing of
the waste oil to determine the presence of such contaminants is discussed
in Section 3.5.5.
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