Development of lime kilns

A large variety of techniques and kiln designs have been used over the centuries and around the world. In 1935, Searle [16.2] described some 50 types of kiln. Wingate [16.3] described a number of kilns currently used in developing countries for small scale lime burning. Such kilns are reviewed briefly in the following sections. 

Although sales of lime kilns in recent years have been dominated by a relatively small number of designs, many alternatives are available, which may be particularly suitable for specific applications. In addition, as most kilns remain serviceable for several decades, many obsolete designs are still in operation, either in the original, or a modified form. 

The purpose of this section is to give an appreciation of how kilns have developed, which types are in common use and which types are generally being installed. 

The earliest technique used for burning lime probably consisted of an uncovered heap, containing alternating layers of wood and limestone. The wood was lit and burnt in an uncontrolled manner for 1 to 2 days. Relatively small amounts of lime were produced at a very poor thermal efficiency. 

Subsequent techniques achieved higher thermal efficiencies by insulating the heap (e.g. by use of a clay skin) and by controlling the air flow (e.g. by placing the wood in a pit with an air channel, and building a mound of limestone on top of the wood). 

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