Cimpor reduces CO2 emissions in cement production with activated clay

thyssenkrupp equips a Cimpor Global Holdings plant in Cameroon with an activated clay production system. Using this material, Cimpor cuts CO2 emissions in cement production by 40%.

The new production process replaces a component of cement clinker with activated clay. This is a naturally occurring porous material that has a high absorption capacity by drying, among other things. The material retains its structure if exposed to water. The material can then be reactivated by heating it.

Cement production is a process that releases large amounts of CO2. This is because CO2 is a natural constituent of limestone, the main component of cement. For the production of each tonne of clinker - which is later ground into cement - the process-related CO2 emissions are about 790 kilograms (kg). Two-thirds of these emissions are due to the use of limestone, which releases CO2 through a chemical reaction that is part of the production process.

Cement clinker production is also energy-intensive, as limestone and other materials for cement production are heated to a temperature of more than 1,400 degrees Celsius. This energy consumption also leads to additional CO2 emissions.

Technology from thyssenkrupp makes it possible to replace about a third of cement clinker with activated clay. The production process heats this clay to around 800 degrees Celsius, which is considerably lower than required for the production of conventional clinker. This requires less energy, which, combined with the different chemical composition, reduces CO2 emissions by 40%.

Cimpor is deploying the technique on an industrial scale at a plant near Kribi, a port city in African Cameroon. The plant - once completed in autumn 2021 - should reduce the company's CO2 emissions by 120,000 tonnes on an annual basis. The plant will produce 720 tonnes of activated clay per day. It is Cimpor Global Holdings' second project around activated clay.

"At thyssenkrupp, we are convinced that CO2-neutral cement production is fundamentally possible and achievable in a few steps," says Pablo Hofelich, CEO of thyssenkrupp's Cement Technologies business unit. "We are already far along on the technology side in several areas. We offer our customers products that reduce their impact on the environment while saving costs. This makes it possible to significantly reduce CO2 and nitrogen emissions and reduce the use of raw materials, water and fossil fuels such as coal and gas."

Clay is available in large quantities worldwide, especially in developing countries where demand for cement is rising. These include Southeast Asia, large parts of Africa and Latin America. Using activated clay eliminates the need to import clinker. The technology can thus offer a financially attractive alternative to clinker without compromising on quality.

thyssenkrupp also points to another technology that can help make cement production more environmentally friendly. This involves the company's oxyfuel technology. This technology enables the use of pure oxygen instead of outside air when heating limestone for clinker production. Because nitrogen is no longer part of the process, the CO2 emitted is highly concentrated and easier to separate, store and reuse.

Author: Wouter Hoeffnagel