VTT Technical Research Centre of Finland has developed an electric rotary kiln that is capable of making cement production close to carbon neutral. Powered by low-emission electricity, the kiln enables the capture of pure CO2 when lime is burned in the pre-calcination phase of cement production.
VTT has successfully completed several experiments using different feedstocks between November 2021 and October 2022, with the participation of Finnish cement producer Finnsementti and Nordkalk, a leading manufacturer of limestone-based products.
Until now, carbon-neutral production of industrial-quality burnt lime mix has been an elusive goal, says VTT. “Limestone is one of the most used raw materials in the world, so it is urgent we find ways to use it in a more environmentally friendly way. At VTT, we have been able to make the crucial calcination phase more sustainable. With tests of our electric kiln, we have proven that replacing combustion processes with electricity-based solutions is an effective means of curbing climate change. Furthermore, the quality of the burnt lime product is good,” said Eemeli Tsupari, principal scientist at VTT.
The pilot kiln has also been designed with convenient transport in mind. Housed inside a cargo container, it can be easily transported to industrial plants to be used in different production processes, including chemical pulping in the paper industry.
“With proof of concept for the electric kiln in the pre-calcination phase, we are on the path towards fully decarbonising the second burn process by considering new carbon-free heat sources, such as hydrogen, to reach the necessary temperatures,” adds Eemeli. “The current high cost of natural gas makes electricity a more viable option for heating processes using gas. Solving this challenge globally could be the equivalent of taking millions of cars off the road each year. We are now looking for partnerships with major industrial players to take this solution to the next level.”
“The raw meal of cement production was successfully treated in the trial runs to an intermediate product which is fully calcined but not yet reacted with silica, which is exactly what is wanted to achieve in a calciner,” explains Mathias Frankenhaeuser, technical manager at Finnsementti.
“It’s exciting to see that properties of calcium oxide produced in the best experiment points are very near to product-grade burnt lime,” adds Erkka Uuttu, energy manager at Nordkalk.
The kiln is currently located at a VTT facility in central Finland in the city of Jyväskylä.
