47    WASTE OIL RECOVERY
Carl P. Steele, Market Manager, Industrial Waste
Christopher T. Mahoney, Technical Services Manager
James D. West, Process Engineer, Technical Services
Bird Machine Company, Inc.
South Walpole, Massachusetts 02071
INTRODUCTION
Traditional methods of waste oil management have essentially involved the collection of generated
wastes into convenient ponds, tanks, or similar storage for subsequent removal to approved dump
sites. This is a generalization, of course, since a variety of forms of pretreatment of these wastes is
accomplished to recover valuable byproducts, reduce volume, etc. These resource recovery efforts
have been accelerated by many industries since the passage of the Resource Conservation and Recovery Act of 1976, and the 1984 Amendments to the Acts, which prohibit disposal of bulk hazardous
liquids in landfills and require storage in properly constructed surface impoundments. Additional
requirements imposed by the amendments to the act require generators to initiate programs designed
to minimize quantities of waste produced. These requirements, and the declining availability of final
disposal sites for waste sludge and the increased costs associated with such disposal, will have a
significant impact on industry operations.
Based on more than 50 years of liquid/solids separation research and practical applications experience, Bird Machine Company, Inc. in South Walpole, MA have combined Bird centrifuge technology
with emulsion breaking technology to transfer a waste oil stream into the following:
• A purified oil stream that can be recycled back to the plant or sold as a byproduct.
• A water suitable for discharge to a wastewater treatment system.
• A solid that is non-free bleeding.
WASTE OIL RECOVERY
Typical refineries have large volumes of various waste oil sludges from a variety of sources. They
can be tank bottoms/cleaning sludges, API separator sludge, dissolved and induced air flotation
skimmings, slop oil, or impoundment pond sludge. The variability of refinery wastes has been the
historical bottleneck in finding a cost-efficient means of treatment. A successful system must handle
wide variations in oil, water, and solids.
In most cases, waste oil recovery is a four phase system: oil, emulsion, water, and solids. The
relative volumes of each of these components in the waste stream varies not only from application to
application but from tank to tank. The most troublesome part of any waste oil system is the oil-water-
solids emulsion which is almost always present and which in conjunction with the oil and water
represents a distinct phase for separation. This emulsion phase by definition is a stable composite
which cannot be broken through the use of centrifugal or filtration mechanisms. The first step in a
successful waste oil recovery system is to destabilize this emulsion phase through the use of heat/
chemical treatment to counteract the attraction due to surface charges at the molecular level.
Typically, the heat/chemical treatment involves one or more of the following steps depending on
the make up of the waste oil stream and the type of emulsion present:
Heat Treatment (180°-200°F)
The use of heat is by far the most common treatment used to break emulsions. It has three primary
effects on the emulsion phase: 1) Reduction of the viscosity which aids in the mixing of chemicals and
the sedimentations of the fine suspended solids; 2) Due to a higher thermal coefficient of the oil
component of the emulsion as opposed to the water component, healing produces a higher reduction
in the specific gravity of the oil component than in the water component which aids in sedimentation
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