Page 102 - Materials Chemistry, Second Edition

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Cleaner Production
conventional air spray guns and this will reduce overspray and
hence will save raw material.
– Fixed painting table can be modified to a turning or rotating paint-
ing table to facilitate the painting process from all directions.
• Reducing air emissions is necessary when spraying polyester and
polyurethane or any other chemical as these are very harmful to the
working environment if not done in a controlled area. The emissions’
impact can be reduced and controlled by adopting several measures:
– A good ventilation system to collect the dust especially after
polyester spraying where the white “polyester” dust is very dan-
gerous to the worker force.
– The chimney of the painting booth should be high enough from
any surrounding buildings and could contain a filter. Biofiltration
is recommended as a control technology, where contaminated exhaust
air passes through a biofilter for contaminant removal. The biofilter
consists of organic matter, such as tree bark and compost, the pores
of which are filled with water. Biologically active micro-organisms
are present, partly free-floating in the water and partly attached
to the organic matter. Other recommended filters are catalytic
oxidizers.
– Always use the spraying booth for painting processes. This
improves product quality and protects the surrounding environ-
ment as well as the working environment.
• In the area of materials reuse and recycling, waste separation is the
first step for on-site or off-site recycling. Waste separation involves
avoiding both the mixture of different types of waste and the mix-
ture of hazardous wastes with non-hazardous wastes. This makes the
recovery of hazardous wastes easier by minimizing the number of
different hazardous constituents in a given waste stream. Also, it pre-
vents the contamination of non-hazardous wastes. Specific examples
include segregating spent solvents by solvent types, and segregating
non-hazardous paint solids from hazardous paint solvents and thin-
ners. Solvent recycling is the use or reuse of a waste as an ingredient
or feedstock in the production process on-site.
– Reuse of cleaning solvent for painting equipment as a reducer for
the next batch of the same or darker color.
– Distilling “dirty” solvent and reusing it for cleaning.
– Inclined table to collect the drops of sealer/waste paint for reuse,
instead of being lost on the floor or above the table.
• Loss prevention and housekeeping is the performance of preventive
maintenance and equipment and materials management to minimize
opportunities for leaks, spills, evaporative losses, and other releases
of potentially toxic chemicals.
– Spray guns can be cleaned by submerging only the front end of the
gun in the cleaning solvent.