Limekiln
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- CaCO3 + heat → CaO + CO2
Although limekilns were used in the production of lime mortar in Ancient Egypt and later by the Greeks and Babylonians, the Romans favored instead to produce their mortars from pozzolanic ash.
Limekilns seem to have come into regular use about the 18th century. The larger stones were used for building but the smaller were burnt to produce lime which was a useful commodity in various ways: it could be spread on the fields, for building purposes or for lime-washing buildings. It was regarded as cleansing and was used not only on farm buildings but often on factories after 1800.
The stone had varying degrees of hardness and therefore took varying times to burn; chalk took about 24 hours and limestone about 60 hours, but the harder stone produced the better product. All kinds of fuel were used in the kilns, wood, coal, turf or other organic products.