Tunstead Works

Washing some of the limestone produces a slurry of clay and limestone fine materials. This is not wasted but used as the basic ingredient of Portland cement which is manufactured in a modern, efficient processing plant.

This new 'dry process' plant was built by one of the world's leading cement plant designers, and opened in 2004.

Emissions have been reduced dramatically and tonne for tonne energy consumption has improved significantly.

The plant works on the principle of combining the slurry from limestone processing, limestone and other mineral additives and feeding them into the kiln which operates with flame temperatures of up to 2,000°C (see process flow chart). The process is fuelled by a combination of coal and petroleum coke which are introduced at two points in the kiln to optimise energy efficiency and reduce emissions.

Inside the kiln a complex chemical reaction forms spherical granules called clinker which are then cooled down and stored in 25,000 tonne capacity silos before being combined with gypsum and milled into the finished cement product.

The new plant is designed to produce 800,000 tonnes of cement each year.