Driving on the gravel road from Edenville to Heuningspruit in the Free State one will notice a strange looking tower sticking out from between the trees. What is/was that?
The answer is that it was a lime kiln, that is a technical term to describe an oven or furnace used to heat limestone to convert it to burned lime for use on the gold mines (as a neutralising agent and as building material). It was owned by the New Honingspruit Lime Works.
What remains of the plant is the kiln, the limestone mine, shells of some buildings and some hardware. It took a bit of detective work to figure out what the process was. The first step in the process was to mine the limestone. Limestone is essentially calcium carbonate (CaCO3). Pieces of limestone of a specific size were loaded onto koekepans, transported to the kiln and hoisted to the top. The fire in the kiln was burning continuously with loading and withdrawal at the same time, except weekends. It was filled in layers of 3000 lb (pounds) limestone followed by 800 lb anthracite (coal).
Heuningspruit Lime Kiln (Horst Müller)
The reaction is represented by the following chemical equation:
CaCO3 + heat--> CaO + CO2...
