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Lime kiln
A lime kiln is used to produce quicklime through the calcination of limestone (calcium carbonate). The chemical equation for this reaction is
:CaCO3 + heat → CaO + CO2
This reaction takes place at 900 °C (at which temperature the partial pressure of CO2 is 1 atmosphere), but a temperature around 1000 °C (at which temperature the partial pressure of CO2 is 3.8 atmospheres〔CRC ''Handbook of Chemistry and Physics'', 54th Ed, p F-76〕) is usually used to make the reaction proceed quickly.〔Parkes, G.D. and Mellor, J.W. (1939). ''Mellor's Modern Inorganic Chemistry'' London: Longmans, Green and Co.〕 Excessive temperature is avoided because it produces unreactive, "dead-burned" lime.
==Early lime use==
Because it is so readily made by heating limestone, lime must have been known from the earliest times, and all the early civilizations used it in building mortars and as a stabilizer in mud renders and floors.〔P. C. Hewlett (Ed), (1998). ''Lea's Chemistry of Cement and Concrete: 4th Ed'', Arnold, ISBN 0-340-56589-6, Chapter 1〕 Knowledge of its value in agriculture is also ancient, but agricultural use only became widely possible when the use of coal made it cheap〔Colin Platt, (1978). ''Medieval England'', BCA, ISBN 0-7100-8815-9, pp 116-7〕 in the coalfields in the late 13th century, and an account of agricultural use was given in 1523.〔Sir Anthony Fitzherbert, ''Boke of Husbandrye'', 1523〕 The earliest descriptions of lime kilns differ little from those used for small-scale manufacture a century ago. Because land transportation of minerals like limestone and coal was difficult in the pre-industrial era, they were distributed by sea, and lime was most often manufactured at small coastal ports. Many preserved kilns are still to be seen on quaysides around the coasts of Britain.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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