Amine-based post-combustion capture

Amine-based carbon capture is a regenerative process using an amine solvent to remove CO2 from flue gas. Reversing the reaction releases pure CO2 for capture and frees up the solvent for re-use.

Amine-based post-combustion capture (PCC) is a well-proven and commercially-available technology, having been used in the petroleum sector since 1996 and in the coal-fired power industry since 2014. In the cement industry, it was successfully used to capture carbon dioxide (CO2) during a small-scale trial at Norcem’s Brevik plant in Norway, a project that is now being scaled up to capture up to 400,000 tonnes per year of CO2.

The technology uses an amine solvent to scrub CO2 from the flue gas. The flue gas is initially fed into an absorption column, where the solvent selectively removes the CO2. The CO2-rich solvent is then fed into a desorber column, where it is heated to release the CO2, which is captured before being sent for geological storage or onward use. This regeneration process is highly energy intensive, however, posing an economic and environmental challenge.

The regenerated solvent is cooled and returned to the absorption column.

Commercially-available amine solvents can be grouped into first and second generations. First-generation solvents include mixtures of water and monoethalolamine (MEA), diethalolamine (DEA), triethanol amine (TEA) or potash. Of these, MEA is most widely used for CO2 absorbtion, due to its high selectivity, quick reaction and low cost. However, it is also sensitive to impurities and requires desulfurization and denitrification of the flue gas to work effectively.

Second-generation solvents include improved blends of sterically-hindered alkaloamines and amino acids that require lower regeneration temperatures and are more resistant to degradation. However, they cost more than and do not perform as well as MEA.

Despite the challenges, amine-based PCC is the most advanced carbon capture technology available to the cement industry with several suppliers on the market. Its planned commercial-scale deployment at Brevik – where waste heat from the cement manufacturing process will be used to optimise the process – is set to provide valuable operating experience to the industry, easing its future adoption by other cement plants.