In 2019, four European cement manufacturers – Buzzi SpA/Dyckerhoff GmbH, Heidelberg Materials AG, SCHWENK Zement GmbH & Co. KG, and Vicat S.A. – joined forces through the research company CI4C GmbH & Co. KG to jointly implement the CO₂ capture project “catch4climate” at the cement plant site in Mergelstetten. The facility, for whose construction and operation more than €120 million is being invested, will be the first to use the so-called Pure Oxyfuel process for CO₂ capture. To this end, a dedicated rotary kiln line with a clinker production capacity of 450 tonnes per day is being built exclusively for research and development purposes.

The Pure Oxyfuel process was developed by thyssenkrupp Polysius. Hoffmeier, based in Hamm, was commissioned with the manufacture of the kiln shell, the installation of the riding rings, the kiln inlet and outlet sections, and the girth gear. The CO₂ Purification Unit (CPU) is being built by Linde Engineering, while the oxygen supply system (LOX = Liquefied Oxygen Plant) will be provided by Westfalen AG.

In December 2023, the rotary kiln was transported by inland waterway vessel from Hamm-Uentrop to the port of Heilbronn, where it was temporarily stored until the on-site construction work required for kiln installation had been completed. The remaining journey to Mergelstetten was then carried out by heavy goods transport during the night in order to minimise disruption to traffic.

Due to its compact dimensions, this is the first kiln that Polysius has transported as a single unit, complete with riding rings and girth gear, and installed onto the kiln foundations in a single lift. To achieve this, all installation activities on the construction site were planned in detail in advance, alongside the development of the transport concepts, ensuring that the rotary kiln could be positioned without delay in one lifting operation. A 700-tonne crane was used to lift the kiln into place on 7 March 2024.

The commissioning of the Oxyfuel kiln system is expected to take place in the first quarter of 2025. Following commissioning, a project duration of approximately three years is planned for the generation of research and development results, provided that the progress of the findings requires it.

Information: The Pure Oxyfuel Process

The Pure Oxyfuel process used in Mergelstetten (from “oxy” for oxygen and “fuel”) is a clinker-burning process in which pure oxygen is introduced into the kiln instead of air, ensuring heat generation through the combustion of primary and alternative fuels without the presence of atmospheric nitrogen. This approach increases the CO₂ concentration in the kiln exhaust gas to approximately 90%, thereby significantly enhancing the potential for CO₂ capture. The aim is to capture 100% of a cement plant’s CO₂ emissions in a cost-efficient manner. The project is also intended to establish the conditions necessary for the large-scale deployment of CO₂ capture technologies within the cement industry. The captured CO₂ can subsequently be utilised or stored (CCU, CCS).

Many industries – including the production of fertilisers, fuels for long-haul aviation, and plastic-based hygienic medical products – have an urgent need for carbon. To date, this carbon has been obtained almost exclusively from fossil energy sources. Another potential source is the capture and utilisation of the CO₂ generated by the cement industry.