New Type of Clinker: Ternesite Clinker
New type of clinker significantly reduces CO2 emissions
Cement clinker production is very energy-intensive — around 0.8 tonnes of CO2 on average are released per tonne of clinker manufactured. We are therefore making a huge effort to improve the CO2 balance sheet of our production operations. For example, technical process measures and the use of alternative fuels have enabled us to reduce specific CO2 emissions to 0.608 tonnes per tonne of cement produced. However, the possibilities for further reductions in this area have now been fully exhausted at many of our plants. CO2 emissions can also be lowered with the help of additives, such as blast furnace slag or fly ash, which can at least partially be used as substitutes for Portland cement clinker. However, they can only be employed to a certain extent because their supply is limited.
The HeidelbergCement Technology Center (HTC) is developing new and innovative techniques for reducing CO2 emissions. Only for a few years, our researchers at HTC have been working to develop alternative binders that work more or less without conventional clinker. One of the most promising concepts here is Belite Calciumsulfoaluminate Ternesite (BCT). As is the case with conventional binders, the performance capability of this material depends on the clinker phases — i.e. the chemical compounds that form when the raw material mix is heated. Until recently, the ternesite clinker phase was considered to be non-reactive, at least not with pure water. However, it has been discovered that if aluminium is present, as it is in the BCT system, an immediate chemical reaction occurs and a solid structure is formed. After the first successful burning tests in the lab, HTC registered a total of six patents in the late summer of 2011 for the manufacturing and application of clinker containing ternesite.
The benefits of using this substance are clear. First of all, its altered chemical composition and its manufacturing at a temperature that is 150 to 200° C lower result in CO2 emissions that are up to 30% lower than those generated by the production of normal Portland cement clinker. Energy efficiency is also improved, as the lower burning temperature reduces fuel consumption by roughly 10%. The electricity costs for the manufacturing process are about 15% lower as well, because less energy is required for the grinding process. In 2013 a first large-scale BCT trial was launched at one of the HeidelbergCement plants in Germany, where the new product was manufactured for the first time with existing plant technology.