LIME KILN DESIGNS
SMALL-TO-MEDIUM SCALE OIL FIRED LIME KILNS
Lime is a very important basic
material used in a variety of different
industries. These include
construction, agriculture, chemicals
and several processing industries.
There are two forms of lime:
quicklime and hydrated lime.
Quicklime is produced by heating
rock or stone containing calcium
carbonate (limestone, marble, chalk,
seashells, etc.,) to a temperature of
around 1000°C for several hours. In
this process, known as 'calcining' or
simply 'burning', the carbon dioxide
in the calcium carbonate is driven off
leaving calcium oxide plus any
impurities.
Quicklime is an unstable and
hazardous product and is therefore
normally hydrated, becoming not only
more stable but also easier and safer
to handle. Hydrated lime is produced
by adding water to quicklime in a
process called 'hydration' or 'slaking',
where the calcium oxide and water
combine chemically to form calcium
hydroxide.
6 ton per day kiln in Bali.
During slaking the quicklime lumps will disintegrate to a fine powder. If high quality limes
are required some form of screening and/or classification will be required at this stage to
grade the lime. Hydrated lime is normally supplied and sold in bagged form.
If quicklime is hydrated with a large amount of water and well agitated, it forms a milky
suspension known as milk of lime. Allowing the solids to settle and drawing off the excess
water forms a paste-like residue known as lime putty. Methods of burning lime range from
traditional and simple to highly sophisticated and automated. The former are by their nature
labour-intensive and energy inefficient, while the latter are the opposite. In addition the
former tends to produce unevenly burned lime, with a proportion that is underburnt and/ or
overburnt, while the latter produces lime of a very consistent quality.
The type of kilns described in this leaflet are small to medium sized (6 to 16 tonnes output
per day). These attempt to combine the advantages of traditional kilns, by being reasonably
simple to construct and operate, but still retain the advantages of a high quality product and
energy efficient production associated with larger; more sophisticated kilns.
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