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Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
idw - Informationsdienst
Wissenschaft
The cement industry is one of the largest producers of carbon dioxide. It is responsible for up to eight percent of global man-made emissions – almost three times as much as the global air traffic. To reduce this share and become climate-neutral, the industry is relying on technological innovations. The international project “ECem”, in which scientists from the Helmholtz Center Dresden-Rossendorf (HZDR) are also involved, is pursuing a promising approach. With the help of electric heating technologies for the energy-intensive process of calcination, the partners from science and industry want to drastically reduce CO2 emissions in cement production.
The project started in the fall of 2024 and will run for three and a half years. It is funded by the Danish Innovation Fund with 21 million Danish crowns (about 2.8 million euros).
Calcination is one of the most important process steps in the production of cement. Limestone is heated to approximately 1450°C in a large furnace and converted into clinker, the main component of cement, by thermal decomposition. This chemical process is responsible for a large proportion of the CO2 emissions released by the cement industry as a whole. Two-thirds of the CO2 is produced during the decomposition of the limestone, a process known as decarbonization, and is therefore unavoidable. The remaining third is due to the enormous energy consumption required to reach the high temperatures. Fossil fuels such as coal or gas are usually used for this purpose.
The „ECem“ (Electric calciner technologies for cement plants of the future research project is now taking on this industrial heating process. The goal is to develop a more climate-friendly alternative. To this end, the project partners, led by the Danish cement company FLSmidth, including the Danish Institute of Technology, the University of Aalborg, the companies European Energy and Cementos Argos, as well as the HZDR, want to develop two different electric heating technologies.
Metal balls give limestone the necessary material properties
While the Danish partners in the project are working on the development of an infrared radiant heating system, scientists at the HZDR Institute for Fluid Dynamics are researching an electrical solution based on inductive heating. The team first wants to set up a laboratory experiment in which induction coils generate a high-frequency field to heat the material in a container. In a later stage, a rotating kiln will be modeled in a further experimental setup with key data that closely approximates industrial conditions. The challenge is that materials such as limestone, which consists mainly of calcium carbonate, are actually unsuitable for induction heating due to their poor electrical conductivity.
To overcome this obstacle, the team wants to mix so-called susceptors into the raw material to be heated. These are components designed to efficiently convert the electric energy into heat and transfer it to the material. An important task is to find the right material that can function robustly as a susceptor at high temperatures and under harsh industrial conditions. Possible candidates must have a high melting point, must not react with the limestone and should be abrasion-resistant. Forming the susceptors into a shape, for example as metal balls, would have the advantage of combining the calcination and grinding processes into a single step. Investments in the electrification of industrial processes could, in addition to avoiding CO2, have further positive effects such as increasing efficiency or improving product quality, thus giving the respective companies a competitive advantage in the global markets.
Optimization of gas flows ensures effective heat transport
“At first glance, this project has less to do with the fluid mechanics that we usually deal with at the institute,” explains HZDR engineer Dr. Sven Eckert, head of the Magnetohydrodynamics Department. "However, this is not just a matter of installing a heater in a reactor. Cement kilns usually process many tons of material, which is why the difficulty lies in creating a homogeneous temperature field throughout the entire kiln. An inductive heater could even exacerbate this problem if it does not guarantee sufficient heat transport that reaches not only the surface layers but also the interior of the huge volume. Therefore, we have to look at the process in principle, including an optimization of convective gas flows in the furnace, which must ensure effective heat transport."
This is where the researchers around Sven Eckert can apply their expertise. At the HZDR, they also have access to unique measuring techniques such as magnetic field tomography, which is ideally suited for monitoring electrified industrial processes. The team also wants to benefit from the experience gained in the EU project CITADEL, which is coordinated by the HZDR and is already in progress.
The aim of the ECem project is to validate the technology on a laboratory scale. The data obtained in the planned experiments will be an important input for accompanying computer simulations and the development of digital twins that will map the entire process, including energy and mass flows. On this basis, the scientists want to clarify whether the laboratory experiment can be scaled up to real industrial conditions. If the answer is positive, the partners could start building a pilot plant similar to the industrial version after the project ends in 2028. Depending on the research results, this plant could either include induction heating or radiation heating, which are being developed in parallel – or, which is not unlikely, a combination of both solutions.
Dr. Sven Eckert | Head of Department Magnetohydrodynamics
Institute of Fluid Dynamics at HZDR
Phone: +49 351 260 2132 | Email: s.eckert@hzdr.de
Functional diagram of the inductive heating of a rotary kiln reactor in cement production.
HZDR / B. Schröder
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