Innovative technology for carbon capture
Concept of the Calix direct separation reactor (DSR) for CO2 stripping during the calcination process.
What is a calciner?
Limestone consists mainly of calcium carbonate (CaCO3).
Cement production requires calcium oxide (CaO) as a component of the clinker in order to react with water to become solid concrete.
By adding heat to the limestone in the calciner, the CO2 is driven out of the CaCO3.
The calcination process takes place in a rotary kiln, or – in modern kiln lines – in the calciner, which forms part of the high preheating tower.
Calix magnesium-oxide reactor at Bacchus Marsh near Melbourne, Australia, which has been operating since October 2013.
Development of a new calciner to separate out CO2 released from limestone in clinker production.
At last year’s COP21 Climate Conference in Paris, world leaders agreed to limit global warming to a maximum 2°C, with an ambitious ideal of only 1.5°C, in order to prevent disastrous flooding in many countries.
The cement industry has also announced its Low Carbon Technology Partnership initiative (LCTPi), which aims at reducing global CO2 emissions by 20-25% compared to “Business as Usual” by 2030. But the question remains: what actions can realistically be taken to reach this objective?
One answer could be the LEILAC project: Low Emission Intensity Lime And Cement. HeidelbergCement and others companies have teamed up in a consortium with Australian technology provider Calix to develop a breakthrough calciner that can directly separate and capture the CO2 released from limestone when being transformed into clinker. This €21 million project has received €12 million in support from the EU. It includes design, construction and testing of the innovative calciner at HeidelbergCement’s Lixhe cement plant in Belgium.
“The power industry is shifting to renewable sources, such as solar and wind power, and the automotive industry as well is slowly converting to electrical cars and low carbon fuels,” says Peter Lukas, Director Global Environmental Sustainability (GES). “In 30 years, the cement industry could become by far the largest CO2 emitter of all sectors. Therefore, we have to act now, as technological changes in our capital-intensive industry take several decades to mature.”
HeidelbergCement already started a pioneer with the first Carbon Capture project in the cement industry in Norway and supports the climate change innovations of ECRA, the European Cement Research Academy. ”The new Calix calciner has the potential to bring about a giant leap forward in CO2 abatement,” says Jan Theulen, Director Alternative Resources at GES. “Over 60% of our CO2 emissions originate from the calcination of limestone. If we could separate this CO2 without using more energy, we would come closer to financially feasible carbon capture. We have joined forces with other cement companies, such as CEMEX and CRH Tarmac, as well as Lhoist, one of the world leaders in the lime industry. The production of lime requires a similar calcination process. One of the reasons for the EU to support the project was that the innovation will help several industries in their climate change abatement efforts.”
Stefan Federhen, Manager Process Engineering at HTC Global, has supported Calix adapt the technology to a cement kiln. ”What makes this direct separation reactor (DSR) so different is that the heat for calcination is not directly brought into contact with the limestone. The heat is introduced indirectly via the hot surface of super high-grade steel at 1050°C or more. This allows stripping of CO2 from the limestone, without mixing it with other combustion gases. The result is an unparalleled high CO2 concentration of more than 95%, which - according to the plan - can be cooled and then directly used for further purposes.”
It is this feature that makes the new calciner highly innovative, but at the same a challenge, given that the steel has to stand up to the corrosive kiln atmosphere. The engineers from Calix have built a similar calciner that has been operating for some years at an already impressive temperature of 900°C. “On the basis of this knowledge, we will select the most appropriate steel in terms of cost and performance,” adds Stefan Federhen. “Our goal is to master the heart of the technology: the super hot steel surfaces.
Jan Theulen, Director Alternative Resources at GES (left) and Julien Wart, Plant Manager Lixhe, in front of the kiln and the preheater tower, where the Calix calciner will be built.
Kick-off of the project was in January 2016 at the Lixhe plant. Some tough engineering nuts must now be cracked before constructing the 50-metre high tower. Final construction will take place in 2018, followed by two years of intensive testing. Julien Wart, Plant Manager of Lixhe, is deeply involved in the project: “Our industry needs such innovations, and I’m eager to support the project. At the same time, I have to take care of many practical issues, for example, that the new Calix tower is positioned in a way that our maintenance cranes can still access the kiln. The environmental, safety and health aspects of this pilot must also comply with our standards. Communication with our employees and neighbours is important. We have to explain the importance of the project for our industry, and for Lixhe to be at the forefront of the industry on this CO2 abatement technology.”
“We are excited about the chance to utilise EU funds to initiate a fundamental change to the environmental impact of clinker production,” says Jan Theulen. “We have to work hard to maximise the value of the tests. The whole cement sector will be watching us, and therefore I’m glad we have joined forces between GES, HTC and the operations. Together with our consortium partners, we have access to a lot of brainpower and experience to make this challenge a success.”