Together with its business partners, research, development and innovation partner VTT Technical Research Centre of Finland (VTT) has developed a solution that it says can bring a significant reduction in carbon dioxide (CO2) emissions in the production of cement and quicklime.
As one of the ingredients of concrete, cement is the world's most used building material and is responsible for about 7% of the world's CO2 emissions.
By using low-emission electricity instead of combustion for decomposing calcium carbonate – a central part of cement production – and by capturing the CO2 produced in the production process, VTT says it is possible to operate a cement plant with close to zero CO2 emissions.
This is made possible by using a gas-tight, electrically heated rotary kiln, the company notes.
However, considering that the main raw material for cement is limestone, quicklime is also required in huge quantities in the pulp and steel industries.
VTT explains that, in the production of cement and quicklime, emissions are generated for two reasons. At present, the production takes place at temperatures above 1 000 °C, and this releases emissions into the atmosphere.
An even bigger problem for the climate, however, is the carbonate contained in limestone, which decomposes in the production process into CO2 and quicklime. These emissions that result from the raw material itself cannot be avoided without replacing limestone, 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 CO2 from the limestone can be captured and then either stored or used in, for example, the manufacture of low-emission products,” explains VTT project manager Eemeli Tsupari.
Tsupari says there is already a market for CO2 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”.
Finland Minister of the Environment and Climate Change Krista Mikkonen, meanwhile, explains that reducing industrial emissions is of key importance in achieving the climate objectives of the Paris Agreement.
“Research and development has an important role to play in promoting new solutions. This solution, developed to significantly reduce CO2 emissions in cement and quicklime production, is an excellent example of such work. The duplication of these types of solutions and their scaling to the industrial level play a key role in reducing climate emissions from both industry and the construction sector,” she states.
Meanwhile, the Decarbonate project, led by VTT, involved building a 12 m electrically heated rotary kiln which was then used to test, together with VTT’s business partners, the precalcination of the raw powder for cement and the production of both quicklime and also the lime mud used in pulp mills.
The project involves key Finnish players in the sector, including Finnsementti, Nordkalk and UPM.
The test kiln could also be used for reducing emissions in other industrial sectors, such as the battery and asphalt industries.
In the European Union, emissions trading is steering the industry towards reducing emissions. At the current price level, a decrease of 1 t of CO2 emissions means a savings of €60 for the company.
For a medium-sized cement plant, for example, a one-third reduction in emissions would mean savings of several million euros a 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.