Cement - activated clay
The cement industry is one of the world’s largest emitters of CO₂. In 2023, global emissions from this sector reached 2.4 billion tonnes of CO₂ equivalent, representing 6% of total global emissions.
The evolution of the cement sector – what does it mean?
Traditional cement production relies on the manufacture of clinker, obtained by heating limestone and clay to about 1,450°C in rotary kilns. This process generates CO₂ emissions from two main sources: fossil fuel combustion (around 40% of emissions) and the decarbonation of limestone (around 60% of emissions) according to the reaction CaCO₃ → CaO + CO₂.
The activated clay process is a groundbreaking alternative to this traditional approach. Clay, primarily composed of kaolinite (Al₂Si₂O₅(OH)₄), undergoes thermal activation at temperatures between 600 and 900°C, significantly lower than those required for clinker.
This activation transforms the crystalline structure of the clay, creating a reactive pozzolanic material capable of binding with lime to form cementitious compounds.
A single Blue Capsule can reduce natural gas consumption in a 180 MW kiln plant by 80%. Full decarbonisation is possible via the production of electricity or hydrogen.
The impact of the Blue Capsule reactor
Adopting the activated clay process coupled with a Blue Capsule SMR offers considerable potential for decarbonisation.
In France, with a substitution rate of 50% for clinker by activated clay, this technology could avoid up to 5 million tonnes of CO₂ per year. This happens by eliminating limestone decarbonation and replacing fossil fuels with nuclear energy.
The integration of the Blue Capsule reactor into the activated clay process is fully compatible with current industry practices. For an activation process at 850°C, a single Blue Capsule can preheat combustion air to around 700°C for 180 MW kilns, with the final temperature reached by burning a small volume of natural gas.
A single Blue Capsule can therefore reduce natural gas consumption in a 180 MW kiln plant by 80%. Full decarbonisation is possible via the production of electricity or hydrogen.
Certain clays require activation at temperatures below 700°C, enabling full and direct decarbonisation at lower cost using Blue Capsule hot air, without relying on electricity or hydrogen.
Fewer than a dozen capsules would be enough to decarbonise the clay activation process across the entire French cement sector, provided cement producers adopt this method instead of clinker production and regulations allow such a substitution rate (currently permitted in CEM IV and V cements).
