New Hybrid Technology Makes it Easier to Capture and Purify CO2 Produced by the Cement Industry

Cement production contributes to 7% of greenhouse gas emissions worldwide. Now, a novel hybrid technology makes it less costly and easier to capture and purify CO2 generated by the cement industry, and added to this, the technology can be retrofitted to existing cement plants.

Cement is one of the world’s commonest building materials, and its manufacture accounts for 7% of our greenhouse gas emissions. We have to do something about this. This photo was taken in Shanghai. (Image credit: Thinkstock)

At SINTEF, scientists have now improved the technique used for capturing greenhouse gases produced during the manufacturing process of cement. Since this technique is based on the liquefaction of CO2, it is believed that this technology can be used by cement factories and also in other industrial processes in coastal regions and along European rivers, thus enabling it to be transported by ship. As stated above, the technology can also be retrofitted to existing cement plants.

Usually, the flue gases released from a cement factory contain approximately 20% of CO2. However, to transport and/or store the CO2 from these flue gases, they have to be cleaned first. The present minimum requirement is about 95% purity. Conversely, this process needs huge amounts of heat and is therefore energy-intensive.

In light of this, the researchers have now proposed that the industry must use a hybrid technology that makes it easier and energy-efficient to capture CO2 and is also more suitable to transport CO2 by ship.

More than 99% pure

We propose a promising approach using a membrane filter combined with an in-house developed system involving forced concentration of the CO2 by liquefaction. We achieve this by cooling it down under pressure.

David Berstad, Researcher, SINTEF.

The CO2 gases are concentrated to around 70% purity through the membrane alone. It is a current standard to use an extra membrane step to scrub the gas and attain the required purity of 95%. Yet, the SINTEF team’s technique involving CO2 liquefaction is not only less energy-intensive but also results in a gas that is even purer.

During experiments with the novel system conducted on a laboratory rig in Trondheim, Berstad and his research colleague Stian Trædal made measurements that showed purity levels of at least 99%.

The best results that we have seen are about 99.8%, but it is theoretically possible to achieve even higher levels of purity. The purer the gas the better, because it then requires less capacity to transport and/or store the CO2 in gas or liquefied form.

David Berstad, Researcher, SINTEF.

Electrical energy “replaces” steam

The process also provides another benefit. Unlike other systems, it utilizes electrical energy to cool and compress the gas rather than steam to reproduce solvents (chemicals binding to the CO2—ed. note) as is the case with traditional CO2 capture technologies.

Therefore, the hybrid CO2 capture process does not require steam, which only a handful of industrial facilities in Europe and Norway have access to without having to build an extra steam production facility.

Ship transport instead of pipelines

Another major advantage is that it is possible to transport the liquefied CO2 by ship. To achieve this, CO2 liquefaction is made an essential part of the capture process and thus the CO2 is prepared for transport by ship, which is the method specified in the strategies for Norway’s full-scale CCS project.

If CO2 is not to be transported by ship, but under high pressure in a pipeline, the liquefied CO2 is pumped to the required pressure at a temperature of minus 50 degrees before later being heated up again,” stated Berstad.

Multiple lab rig experiments

Using their laboratory rig, the SINTEF researchers performed the CO2 condensation experiments in autumn 2018, which resulted in the report titled “Experimental investigation of CO2 liquefaction for CO2 capture from cement plants.”

During the experiments the lab rig behaved as expected, so now we know that we can be confident that it works and can force the limits of purity even further,” stated Berstad.

In the coming days, the rig will be made more versatile so that it can be used in other experiments like the separation of syngas mixtures, which is applicable in many different systems being employed for emissions-free hydrogen production.

We have constructed the rig to be as versatile as possible so that it can meet a number of different experimental needs. As well as carbon capture and storage applications, we want to use it to find out exactly what level of purity is needed for the liquefaction of CO2. Besides, we intend to use it to see how we can efficiently remove and liquefy CO2 during the production of hydrogen from natural gas.

David Berstad, Researcher, SINTEF.

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