This document describes the manufacture of flat
glass and pressed and blown glass. Flat glass in-
cludes plate and architectural glass, automotive
windscreens, and mirrors. Pressed and blown
glass includes containers, machine-blown and
hand-blown glassware, lamps, and television
tubing. In both categories, a glass melt is prepared
from silica sand, other raw materials such as lime,
dolomite, and soda, and cullet (broken glass). The
use of recycled glass is increasing. It reduces the
consumption of both raw materials and energy
but necessitates extensive sorting and cleaning
prior to batch treatment to remove impurities.
For the manufacture of special and technical
glass, lead oxide, potash, zinc oxide, and other
metal oxides are added. Refining agents include
arsenic trioxide, antimony oxide, nitrates, and
sulfates. Metal oxides and sulfides are used as
coloring or decoloring agents.
The most common furnace used for manufac-
turing glass melt is the continuous regenerative
type, with either the side or the end ports con-
necting brick checkers to the inside of the melter.
Checkers conserve fuel by acting as heat exchang-
ers; the fuel combustion products heat incoming
combustion air. The molten glass is refined (heat
conditioning) and is then pressed, blown, drawn,
rolled, or floated, depending on the final prod-
uct. Damaged and broken product (cullet) is re-
turned to the process.
The most important fuels for glass-melting
furnaces are natural gas, light and heavy fuel oil,
and liquefied petroleum gas. Electricity (fre-
quently installed as supplementary heating) is
also used. Energy requirements range from 3.7
to 6.0 kilojoules per metric ton (kJ/t) glass pro-
duced.
The grinding and polishing of flat glass to pro-
duce plate glass have become obsolete since the
development of the float glass process. The
chemical makeup of detergents that may be used
in float glass manufacturing can vary signifi-
cantly—some may contain phosphorus. In blow-
ing and pressing, pollutants in effluents are
generated by finishing processes such as cutting,
grinding, polishing, and etching. The pollutants
include suspended solids, fluorides, lead, and
variations in pH.
Liquid effluents also result from forming, fin-
ishing, coating, and electroplating operations.
Heavy metal concentrations in effluents occur
where silvering and copperplating processes are
in use.
Sources
Bounicore, Anthony J., and Wayne T. Davis, eds. 1992.
Air Pollution Engineering Manual. New York: Van
Nostrand Reinhold.
Economopoulos, Alexander P. 1993. Assessment of
Sources of Air, Water, and Land Pollution: A Guide to
Rapid Source Inventory Techniques and Their Use in
Formulating Environmental Control Strategies. Part 1:
Rapid Inventory Techniques in Environmental Pollution.
Geneva, World Health Organization.
Sittig, Marshall. 1975. Pollution Control in the Asbestos,
Cement, Glass, and Allied Mineral Industries. Park
Ridge, N.J.: Noyes Data Corporation.
World Bank. 1996. “Pollution Prevention and Abatement:
Glass Manufacturing Plants.” Draft Technical Back-
ground Document. Environment Department, Wash-
ington, D.C.
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