Flue gases from industrial plants contain the greenhouse gas CO₂. Carbon capture processes increase the concentration of the gas, enabling it to be utilized or stored.

However, carbon capture technologies rely on energy to release the CO₂ after it has been captured. Normally, this process uses heat as its source of energy, and some industries are able to exploit available surplus heat. For others, however, carbon capture requires complicated retrofitting or modifications to infrastructure, and incurs increased fuel costs.

Optimizing energy consumption

A team of researchers at SINTEF has recently developed a new and simpler technology, called CSAR, for the capture of CO₂ from industrial flue gases. CSAR stands for Continuous Swing Adsorption Reactor. It is based on a heat pump, a vacuum pump and the efficient use of electricity.

"Our studies have shown that the CSAR technology competes very well with technologies that utilize heat. This applies in particular if reasonably-priced electricity from renewable sources is available.

The advantage is that both pumps require just a single conventional source of electricity. This makes the technology ideal for installation on existing plants.

Jan Hendrik Cloete, a Research Scientist at SINTEF, explains the process in more detail. "The CSAR technology utilizes two reactors in the capture process. The CO₂ is initially captured in the first reactor by a sorbent, which binds the gas to its surface.

"This binding process occurs at low temperature and generates heat. The heat is then transferred to the other reactor, where it is used to release the CO₂ from the sorbent, this time at a higher temperature. The heat pump is used to transfer the heat between the reactors, while the vacuum pump assists in releasing the CO₂.

"The combined action of the two pumps makes the transfer of heat very efficient, and is also the reason for the low levels of energy consumption involved in this technology."

Highly competitive

"Our studies have shown that the CSAR technology competes very well with other technologies that utilize heat," says Cloete. "This applies in particular if reasonably-priced electricity from renewable sources is available," he says.

This summer, the CSAR technology was demonstrated by SINTEF and the Norwegian company Caox at the BIR AS waste combustion plant outside Bergen. Every year, BIR processes about 220,000 tons of household waste for electricity and district heat generation, resulting in the emission of 250,000 tons of CO₂.

"After 100 hours of operation, we found that we were able to capture the same amount of CO₂ from real exhaust gases as we had in our laboratory tests," says Cloete. "This was an important step because it confirmed that the CSAR concept also works at an industrial scale. It also helped to boost confidence in our economic estimates," he says.

The pilot reactor is designed to capture 100 kg of CO₂ per day. BIR is working to install a facility designed to capture 100,000 tons of CO₂ annually by 2030. It will achieve this using commercially available technologies. At the same time, the company is also considering the use of new and more efficient technologies, such as CSAR, for capture of the remaining CO₂.

Contributing to CCS technology development

Results from the BIR plant in Bergen are paving the way for scaling up the CSAR technology for application across a range of industries. The pilot reactor has now been returned for upgrading at SINTEF's multiphase laboratory in Tiller outside Trondheim.

Following this, the plan is to install the pilot in a cement factory in Spain. This is part of an ongoing project called CAPTUS, which is looking into sustainable methods for the capture and utilization of CO₂ from energy-intensive industries.