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 3.6 BLENDING. Two possible methods of blending waste oil with fuel oil are:
direct and in-line blending. Direct blending is the addition of the waste
oil directly into existing fuel oil tankage. If the waste oil being added to
the tank is lighter than the normal fuel oil, it should be pumped in at the
bottom of the tank as shown in Figure 3-2a. The lighter oil will tend to mix
as it rises through the heavier oil. If the waste oil is heavier than the
fuel in the tank, it should be pumped in on top as shown in Figure 3-2b. The
heavier oil will tend to mix as it falls into the fuel. The tank contents
should then be circulated to achieve a homogeneous mixture. Care must 'be
exercised to insure that the filler pipe opening is immersed below the fuel
surface in order to prevent splashing and accumulation of electrical charges
and that the oil suction line is not located directly at the bottom of the
tank to prevent the intake of any water or sediments. Direct blending tests
show that no special attention is required to burn the waste oil, except
sometimes to adjust the temperature of the blend so that its viscosity is
nearly the same as that of the regular fuel oil.
In-line blending is simple and practical with either distillate or
residual fuels. Even though additional equipment is necessary, the effort
and expenses are minimal. A waste oil supply and in-line blending scheme is
shown schematically in Figure 3-3. In this scheme, the waste oil is
introduced into the suction side of the main fuel pump of the existing system
to insure thorough mixing. Temperatures are taken at three locations, and a
sampling port is provided downstream of the pump so that the waste oil
concentration can be measured by either the "Temperature Method" or the
"Specific Gravity Method" described below. The recirculating pump near the
waste oil tank is used for stirring the waste oils in the tank, as necessary,
to insure a homogeneous mixture. (Depending on the specific installation,
one may consider the possibility of using the existing fuel transfer pump for
this purpose to cut overall cost.) Experience gained thus far shows that
in-line blending is simple to implement and works in an acceptable manner.
specific gravities, respectively, of the regular fuel oil, waste oil, and
their blend at the same temperature. The waste oil concentration, C, would
be approximately :
For this method, an ordinary hydrometer, a thermometer, a glass cylinder, and
a sampling port close to the burner nozzle in the fuel system will be
required. This is a one-time measurement, but the accuracy is good, the
procedure is simple, and the initial investment is minimal. The accuracy of
3.6.2 Temperature Method. Let T1,
T2, and T3 be the temperatures,
respectively, of the regular fuel oil,
waste oil, and their blend. If these
temperatures are measured at locations
fairly close to one another and the
mixing takes place without the loss or
gain of heat, the waste oil
concentration would be approximately:
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