As one of the ingredients for concrete, cement is the world’s most used building material and is responsible for around 7% of the world’s carbon dioxide emissions.
VTT, with Finnsementti, Nordkalk and UPM has developed a solution that can bring a significant reduction in carbon dioxide emissions in the production of cement and quicklime.
They use low-emission electricity instead of fossil fuels for decomposing calcium carbonate and capture carbon dioxide in a using a gas-tight, electrically-heated rotary kiln with close to zero carbon dioxide emissions.
The main raw material for cement is limestone. Quicklime is also required in huge quantities in the pulp and steel industries. In traditional production of cement and quicklime, emissions are generated for two reasons:
- The production takes place at temperatures above 1000°C, and releases emissions into the atmosphere.
- The carbonate contained in limestone decomposes in the production process into carbon dioxide and quicklime. These carbon dioxide emissions from carbonate cannot be avoided without replacing limestone as one of the world’s most used raw materials.
‘Replacing combustion processes with electricity-based solutions and significantly increasing emission-free electricity production is an effective means of curbing climate change. With this technology, the pure carbon dioxide from the limestone can be captured and then either stored or utilised in, for example, the manufacture of low-emission products. There is already a market for carbon dioxide as a gas used in the production process, and a number of potential uses are being developed that would massively increase the scale of its use,’ explains Project Manager Eemeli Tsupari, Principal Scientist at VTT.
The Decarbonate project led by VTT and including Finnsementti, Nordkalk and UPM has constructed a 12 metre electrically-heated rotary kiln which was then used to test the precalcination of the raw powder for cement and the production of both quicklime and also the lime mud used in pulp mills.
The test kiln could also be used for reducing emissions in other industrial sectors, such as the battery and asphalt industries.
‘Finnsementti has been working on climate change for a long time, and several emission reduction projects are under way. Finnsementti’s strategy includes the goal of carbon neutrality, which can only be achieved with new technology. Minimising fossil energy use and utilising carbon capture will be an integral part of the future of the cement industry,’ says Ulla Leveelahti, Environmental Manager at Finnsementti.
Emissions trading is steering industry towards reducing emissions and at the current price level, a decrease of one tonne in carbon dioxide emissions means a savings of EUR 60 for companies. A one-third reduction in emissions at a medium-sized cement plant would mean savings of several million euros per year. In addition, the electric kiln produces a new product: purified carbon dioxide. In other words, electrically-powered calcination could be economically viable already at current prices, but assessing its feasibility at the industrial scale and the investments required for this will require further studies.
Here is a short film on the topic: