In 2019, the four European cement manufacturers Buzzi SpA - Dyckerhoff GmbH, Heidelberg Materials AG, SCHWENK Zement GmbH und Co. KG and Vicat S.A. joined forces in the research company CI4C GmbH & Co. KG to jointly realize the "catch4climate" CO₂ capture project on the site of the cement plant in Mergelstetten. The plant, for the construction and operation of which over 120 million euros will be invested, is the first to use the so-called pure oxyfuel process for CO₂ capturing. A separate rotary kiln line with a clinker production capacity of 450 tons per day will be built for this purpose, which will be used exclusively for research and development.

The pure oxyfuel process was designed by thyssenkrupp Polysius. The company Hoffmeier in Hamm was commissioned with the production of the kiln pipe, the assembly of the kiln rings, the kiln inlet/outlet segments and the gear ring. The CO₂ purification unit (CPU) is being built by Linde Engineering and the oxygen supply (LOX = Liquified Oxygen Plant) is being provided by Westfalen AG.

In December 2023, the rotary kiln was transported by barge on the river from Hamm-Uentrop to Heilbronn-Hafen, where it was initially stored temporarily until the construction work on site for kiln assembly was completed. The rest of the journey to Mergelstetten was then carried out by heavy goods vehicle during the night to avoid disrupting traffic as much as possible.

Due to its compact dimensions, the kiln is the first that Polysius has transported in one piece, including the race and gear ring, and placed on the kiln foundations in one lift. In addition to working out the transportation concepts, all the assembly processes on the construction site were planned in such detail in advance that the rotary kiln could be placed in one lift without delay. A 700-ton crane was used to lift the furnace into place on 7 March 2024.

The oxyfuel furnace system is expected to be commissioned in the first quarter of 2025. After commissioning, a period of around three years is planned to work on the research and development results, if the progress of the results requires it.

Video: GötschMedia

Info: The pure oxyfuel process
The pure oxyfuel process used in Mergelstetten (Oxy for oxygen) is a clinker burning process in which pure oxygen is injected into the kiln instead of air to ensure heat generation without atmospheric nitrogen by burning primary and alternative fuels. In this way, the proportion of CO₂ in the flue gas is increased to around 90 percent in the furnace, thereby significantly increasing the CO₂ capture potential. The aim is to capture 100 percent of a cement plant's CO₂ emissions cost-effectively. The project also aims to create the conditions for the large-scale use of CO₂ capture technologies in the cement industry. Capture enables the CO₂ to be used or stored at a later date (CCU, CCS).

Carbon is urgently needed in many branches of industry - for example in the production of fertilizers, fuels for long-haul flights or plastic-based hygienic medical products. To date, this carbon has been extracted almost exclusively from fossil fuels. Another option is the capture and use of CO₂, which is produced in the cement industry.

Photos: Armin Buhl