Why is this research needed?

Carbon capture and storage (CCS) is essential for decarbonisation of power generation and industry, as well as the future expansion of emerging industries such as bulk low carbon hydrogen production. Without CCS, net zero emissions targets would be more expensive to achieve. Among available CO₂ capture technologies, post-combustion capture via chemical absorption is the technologically most mature. In particular, amine scrubbing currently dominates the market, with two large scale plants in North America and one under construction in Norway. One significant challenge of these amine scrubbing plants is ‘amine slip’, where small amounts of amines and their degradation products form aerosols in the absorber and are unintentionally released into the atmosphere. Amine degradation products like nitrosamines are carcinogens, therefore stringent emission limits must be adhered to.

For individual plants, the Environment Agency is proposing emission limits with EAL of 0.2 ng/m3 of fugitive amine in the treated gas, which will need to be backed up by dispersion modelling. Using existing technology, individual amine scrubbing plants will find it challenging to meet these limits, especially during transient operations. And when several of these units are deployed within an industrial cluster, the localised cumulative fugitive amine concentrations are likely to exceed acceptable levels and pose significant public health risks. This will lead to the tightening of individual plant emission limits and the requirement for new technologies to capture these fugitive amine emissions; preferably by methods that do not lead to additional pressure drop or that consume chemicals, which need to be replenished and/or disposed of. To this end, the consortium proposes a new technology (akin to electrostatic precipitators) to combat fugitive amine release utilising the dipole moments of amines to capture and prevent their release to the atmosphere.

Amines have a high dipole moment (monoethanolamine, MEA = 3.21 D; diethanolamine, DEA = 2.91 D), relative to other molecules in the absorber flue gas (N₂ = 0 D, CO₂ = 0 D, H₂O = 1.98 D), which means when passing through an electric field the amine aerosols will selectively move towards the attractive field plate. The aerosols then adhere to the plate, agglomerate as more become captured, grow in weight, which causes the amines to slide/fall to the bottom of the plate, where the amine is removed and disposed of.

What is this research investigating?

This study will utilise a conductor-like polarizable continuum model via DFT calculations to determine dipole moments, molecular geometry optimisation of different amines and then calculate molecular force interactions within different electric field strengths to determine potential design constraints for a fugitive amine electrostatic precipitator. These calculations will provide the starting point for the mechanical design of a prototype for the fugitive amine electrostatic precipitator.

The objectives of this research are:

• To characterise the dipole moments and electrostatic-force interaction strengths of amines commonly used in CO₂ scrubbing.
• To determine the potential design constraints for the fugitive amine electrostatic precipitator.
• To produce a mechanical design of a prototype of the fugitive amine electrostatic precipitator and estimate its cost.

What does the research hope to achieve?

Academic researchers working in Chemical Engineering and Environmental Engineering aligned to carbon capture, utilisation and storage (CCUS) will be able to make immediate use of this new technique and knowledge and apply it to other CO₂ capture processes with other types of absorbents.

Researchers utilising computational fluid dynamics will also be able to integrate their skills to model new flow field plates and electrostatic interaction vessels. These activities will lead to a reduction of the pressure drop across the unit and enable optimisation of the design.

Electrical engineers and researchers with material/corrosion specialisms will be able to make use of the new process concept to study the design and interactions of amines on the electrostatic plates and their longevity.

Outside of academia, the technology developed here will have a significant impact and benefit as it will promote the utilisation and deployment of mature amine scrubbing CO₂ capture to prevent fugitive amine emissions.