Rumford furnace

A Rumford furnace is a kiln for the industrial scale production in the 19th century of calcium oxide, popularly known as quicklime or burnt lime.

It was named after its inventor, Benjamin Thompson, also known as Count Rumford, and is sometimes called a Rüdersdorf furnace after the location where it was first built and from where the design rapidly spread throughout Europe.

In previous designs, the fuel (traditionally wood or charcoal, later coal) was mixed with the limestone before burning, which meant that the quicklime end product was contaminated with ash and had to be laboriously cleaned.

The quicklime cools down as it slowly descends through the space below the channel connecting the stack to the firing compartment and is finally removed through an outlet at the bottom of the shaft.

The upper part of the limestone shaft extends above the fuel compartments and its walls contain separate cavities filled with coal dust.