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Environmental Pollution and Management 31
4.3 Other Environmental Considerations in Cement Industry
4.3.1 Noise pollution
Noise sources which have a considerable effect on the overall noise emission are
distributed throughout the plant: the quarry with its mobile machines and crushers which
operates only in day time, the cement grinding plants, the rotary kiln with its grate or
planetary cooler, the gas discharge outlet and vehicular traffic in the cement plant.
With regard to noise control measures in the plant, a distinction is to be drawn between
primary and secondary measures. Primary measures are applied at the machines or other
sources of noise themselves. These are essentially design arrangements, e.g., relating to
teeth of gear systems, fan blades, etc., which can be applied only in new or replacement of
machinery. Suppliers’ guarantees relating to noise emission are now a normal requirement
associated with any order for equipment.
It is furthermore advisable to opt for relatively quiet working methods, e.g., the use of
electric motors instead of internal combustion engines, water-cooled instead of air-cooled
engines, low heights of fall of materials being stockpiled, adequate cushioning material to
reduce impact and rushing noises, and avoidance of locating several noise machines in
close proximity to one another.
Secondary measures such as sound attenuators (silencers), acoustic enclosures, acoustic
walls, etc., reduce sound propagation, as do appropriate structural measures. They are more
particularly suitable for subsequent improvements. Drawbacks associated with their use,
besides extra operating expense due to pressure loss or the need for forced heat dissipation,
may include inconvenience in operating, maintaining and repairing the machinery affected
by these acoustic arrangements. In connection with all such measures, the cost factor which
progressively increases with the degree of sound level reduction achieved, should be
critically examined.
4.3.2 Reduction of ground vibrations
As with noise, problems with adjacent residents may also arise in connection with ground
vibrations in cases where the distance between residential buildings and the cement works
or the quarry diminishes. Vibrations are generated by shock-like or impact-like actions such
as blasting, combination of materials by drop-weights, discharge of clinker from silos,
periodic excitation due to roller mills or out-of-balance rotors. The geological condition of
the subsoil is an important factor governing the propagation of body waves as well as the
frequency composition of the vibrations.
In the absence of precise information on geological conditions, on account of the large
number of factors involved, it is not possible to predict vibration nuisance - as contrasted
with noise nuisance - at some considerable distance from the source. With blasting, the