Potential of enhanced weathering of calcite in packed bubble columns with seawater for carbon dioxide removal

[Geoeng Info]

https://www.sciencedirect.com/science/article/abs/pii/S1385894721056709

Potential of enhanced weathering of calcite in packed bubble columns with seawater for carbon dioxide removal

Lei Xing, Huw Pullin, Liam Bullock, Phil Renforth, Richard C. Darton, Aidong Yang

Abstract

Enhanced weathering of minerals is one option being considered for removing CO2 from the atmosphere to help combat climate change. In this work, we consider the weathering of calcite with seawater in a reactor using air enriched with CO2. A mathematical model of the packed bubble column reactor was constructed with the key mass transfer and chemical reaction components validated with experimental data. The modelling results for a continuous process reveal the performance in terms of the specific energy consumption and the CO2 capture rate, which are affected by parameters including particle size, superficial velocities of gas and liquid, reactor bed height and feed CO2 concentration. The major energy requirements are for pumping liquid and compressing gas, and for CO2 enrichment; energy needed for supplying solid particles (mining operations, transport and comminution) was found to be comparatively minor. A trade-off was possible between ground area requirement (determined by CO2 capture rate) and energy requirement. To capture 1 tonne of CO2 at the reactor, optimal designs were predicted to consume 2.1-2.3 GJ of electricity and occupy 1.8-5.2 m2 year of space, depending on the feed CO2 concentration. These would increase to 5.7-8.2 GJ and 7.1-13.1 m2 year per tonne of CO2 captured, after allowing for degassing of the weathering product in the ocean. This increased energy intensity is still within the range of the CO2 removal options previously reported, while the space requirement quantification provides essential information for future feasibility assessment of this scheme.

Graphical abstract

[Tom Goreau]

The article is behind a pay wall, but the abstract is clear, this is about results of a mathematical model of flow of “air enriched in CO2” through a calcite packed column, i.e. industrial emissions abatement, not ambient atmospheric CO2 removal?

 

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https://www.sciencedirect.com/science/article/abs/pii/S1385894721056709

 

Abstract

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[Richard Darton]

No Tom, the idea is to enrich air to a few percent CO2 (say) using DAC and then contact that gas stream with crushed calcite and sea water, releasing the liquid effluent to the ocean. Industrial emissions are not part of the scheme. We did some experiments to validate the reactor model as the paper reports, but Covid and a finite budget somewhat cut the project short. We didn’t work on the DAC part, just assumed reasonable values for energy requirement etc.

It’s not a great scheme, but perhaps just about feasible. The DAC plant would not need as much energy as one making pure CO2 for storage, and you have the advantage of mineralising the CO2. But as the abstract points out, a significant fraction of the captured CO2 returns to the atmosphere when the liquid effluent equilibrates with atmosphere, which is an important issue.

Best wishes,

Richard

Emeritus Professor Richard Darton OBE FREng

https://www.sciencedirect.com/science/article/abs/pii/S1385894721056709

 

Abstract

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[Greg Rau]

Richard,

Would appreciate an eprint when available. This would appear to be a riff on the Rau/Caldeira scheme using flue gas (here and here), but instead using DAC CO2. Why not CO2 from biomass combustion (or fermentation) and forget the expensive DAC front end (and CCS back end)? Anyway, presumably you are aware of the live application of this in a German power plant.

Regards,

Greg

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