Decarbonisation Technology - August 2023 Issue

CO to compression

Flue gas to stack

Condenser

Lean amine

Condensate

Rich amine

Solvent regeneration column

CO absorption column

Steam

Flue gas 3 - 5 vol% CO

Rich amine

Reboiler

Condensate

Lean amine

Figure 1 Typical configuration of an amine-based carbon dioxide scrubbing system

the necessary heating for the desorption of the CO 2 . Reboiler bottoms are recycled back into the absorber, which provides regenerated lean amine ready to repeat the process. Amine scrubbers have a high CO 2 uptake capacity and relatively low initial capital

investment. However, they do suffer from some limitations. Firstly, the operational cost of amine scrubbers is expensive, mainly driven by the energy required to regenerate the amine once it is saturated with CO 2 . Amines absorb CO 2 through a strong chemical reaction, forming very stable bonds that require significant energy to break during regeneration. Our customers in the power generation space have pointed to energy penalties in the 30-40% range, representing a significant drop in productivity regarding both Capex and Opex. Due to the high energy input required, the reboilers are often large, further resulting in operational footprint restrictions. High-duty amine scrubbers have large space requirements, limiting their utility for smaller, more modular carbon capture duties. Lastly, certain amines present challenges from a material handling perspective. Most amines undergo oxidative degradation and thermally degrade at solvent regeneration temperatures above 120°C (Vega et al., 2014). It is estimated that this degradation leads to an average monthly replacement requirement of 5% of the amine. Amines also tend to corrode the process equipment and pipework, leading to higher overall Capex and maintenance-driven downtime. Metal-organic frameworks (MOFs) Initially discovered in 1965 as waste material from other chemical processes, MOFs are a

Figure 2 Simplified and modelled 3D representations of MOF structures comprising metal clusters and organic ligands (linkers)