Advanced Low Energy Enzyme Catalyzed Solvent for CO₂ Capture

Abstract

A proof-of-concept biocatalyst enhanced solvent process was developed and demonstrated in an integrated bench-scale system using coal post combustion flue gas. The biocatalyst was deployed as a coating on M500X structured packing. Rate enhancement was evaluated using a non-volatile and nontoxic 20 wt% potassium carbonate solution. Greater than 500-fold volumetric scale-up from laboratory to bench scale was demonstrated in this project. Key technical achievements included: 10-fold mass transfer enhancement demonstrated in laboratory testing relative to blank potassium carbonate at 45°C; ~ 7-fold enhancement over blank in bench-scale field testing at National Carbon Capture Center; aerosol emissions were below detection limits (< 0.8 ppm); 90% capture was demonstrated at ~19.5 Nm 3 /hr (dry basis); and ~ 80% CO 2 capture was demonstrated at ~ 30 Nm 3 /hr (dry basis) for more than 2800-hrs on flue gas with minimal detectible decline in activity. The regeneration energy requirement was 3.5 GJ/t CO 2 for this solvent, which was below the target of <2.1 GJ/t CO 2 . Bench unit testing revealed kinetic limitations in the un-catalyzed stripper at around 85°C, but process modeling based on bench unit data showed that equivalent work of less than 300 kWh/t CO 2 including all CO 2 compression can be achieved at lower temperature stripping conditions. Cost analysis showed that 20% potassium carbonate in a basic solvent flow sheet with biocatalyst coated packing has economic performance comparable to the reference NETL Case-12, 30% MEA. A detailed techno-economic analysis indicated that addition of catalyst in the stripper could reduce the cost of capture by ~6% and cost of avoided CO 2 by ~10% below reference NETL Case-12. Based on these results, a directional plan was identified to reduce the cost of CO 2 capture in future work.

Integrated Bench-Scale Parametric Study on CO2 Capture Using a Carbonic Anhydrase Promoted K2CO3 Solvent with Low Temperature Vacuum Stripping

“…Free enzyme, dissolved in solvent, together with low temperature stripping, , and CA immobilized as particles or immobilized on column packing and localized in the absorber, together with conventional stripping, , are currently the two typical technologies developed for the CA enhanced CO 2 capture. All these approaches endeavor to address the concern of the low thermal stability of CA at high temperature.…”

“…Akermin Inc. has demonstrated that CA coated M500X structured packing localized in the absorber can achieve 10-fold absorption enhancement in a lab-scale loop reactor, and 7-fold improvement in an integrated slip-stream field test, using 20 wt % K 2 CO 3 . This process was tested at the National Carbon Capture Center (USA), where >2800 h long testing was completed with 90% CO 2 capture at ∼19.5 N m 3 /h flue gas and 80% CO 2 capture at 30 N m 3 /h flue gas . However, a drawback of CA immobilization on structured packing is the logistical challenge and expense of replacing or recoating packing that eventually becomes inactivated.…”

“…This process was tested at the National Carbon Capture Center (USA), where >2800 h long testing was completed with 90% CO 2 capture at ∼19.5 N m 3 /h flue gas and 80% CO 2 capture at 30 N m 3 /h flue gas. 21 However, a drawback of CA immobilization on structured packing is the logistical challenge and expense of replacing or recoating packing that eventually becomes inactivated. In addition, CA immobilization on a fixed surface can potentially limit the full CA activity exploitation, so further work with a free dissolved enzyme warrants investigation.…”

Eight Up-Coming Biotech Tools to Combat Climate Crisis

“…Another example of a successful scale-up of enzymatic CO 2 capture was presented by the American company Akermin Inc., which worked on immobilized CA technology from 2010 to 2013. Akermin Inc. demonstrated 90% capture at ~19.5 Nm 3 ·h −1 , and ~80% capture at ~ 30 Nm 3 ·h −1 for more than 2800 operation hours, with a minimal decline in enzyme activity [ 84 ].…”

The resilience of carbonic anhydrase enzyme for membrane-based carbon capture applications

“…Lu et al [39] showed that the presence of 0.9 M sulfate, 0.7 M chloride or 0.2 M nitrate within 20 wt% potassium carbonate solutions with 20% CO 2 loading and at 50°C resulted in less than 10.2% loss of enzyme activity over short time frames. Zaks and Reardon [40] evaluated the impact of similar anions at 8°C in a similar 20 wt% potassium carbonate solution at 25% loading (pH 10.1) but again only over very short time frames. They showed that the Novozymes enzyme was tolerant to any concentration of sulfate and retained 80% of its activity at 0.25 M nitrate concentration.…”