Encyclopedia of Environmental Science and Engineering, Volume I and II

PCBs AND ASSOCIATED AROMATICS 935

99.99999% efficiency. Because of the increasing short supply

of base stocks suitable for use as electrical transformer fluids

it is becoming increasingly necessary to reclaim the oil. Also,

the once empirical reclamation procedures practiced in the

industry are on a sound scientific footing today so that there

is no need for the concern that there once was regarding the

performance of reclaimed product (Webber^106 ).

Physical processing methods which do not chemically

alter the components of the oil, and which do not leave

residues of the process in the decontaminated fluid, are less

likely to result in changes to the properties of the oil than are

chemical destruction methods.

CHEMICAL EFFECTS OF DECONTAMINATION

PROCESSES

The accepted properties of new mineral transformer oil and

oil requiring reclamation are summarized in Table 54. It is

appropriate at this point to describe the characteristics of

transformer oil.

Power Factor The ratio of the power in watts dissipated

in the oil, to the product of the effective sinusoidal voltage

and current in volt-amperes. It is expressed numerically as the

sine of the dielectric loss angle. An increase in power factor

corresponds to an increase in the concentration of polar con-

stituents in the oil and is used as a measure of the extent of

oxidation.

Neutralization Number The total acid number is defined

as the quantity of base, expressed in milligrams of potassium

hydroxide, required to neutralize the acidic compounds in

1 g of oil. The acids present in service-aged oils are due to

oxidative degradation.

Interfacial Tension The molecular attractive force

between oil and water expressed in units of dynes per

centimeter. As the concentration of polar contaminants in the

oil increases the interfacial tension (IFT) value decreases.

The test is therefore an indirect measure of the oxidation

which has taken place in the oil.

An important question concerning reclamation is whether

or not reclaimed oil is equivalent to new oil and, in par-

ticular, whether or not reclaimed PCB decontaminated oil

is equivalent to new oil. The fuller’s earth treatment of par-

tially oxidized oils is primarily effective in reducing the

neutralization number and power factor to acceptable levels

but is relatively less effective in producing values of inter-

facial tension, color, etc., typical of new oils. Fuller’s earth

treatment does not remove PCBs or ditertiary-butyl-p-cresol

(DBPC) oxidation inhibitor (Webber^106 ). However, chemi-

cal processes for the PCB decontamination of oil involve

highly reactive alkali metals or organometallic reagents

which have a strong affinity for the most easily reduced

components of the oil.

Polarographic reduction is a measure of the ease with

which a compound will accept an electron and this therefore

allows an assessment of the relative reactivities of radical

Destroy as PCB

Contaminated

Liquid

Chemical

Utility Boilers Diesel Engines Decomposition

Decontaminate

for use as fuel

Physical

Separation

ChemicallyInduced RadiationInduced BiologicallyInduced Distillation Extraction Adsorption

Reclaim Liquid

for Re-use

PCB

Contaminated

Liquid

FIGURE 47 The disposal of PCB contaminated liquids.

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