Enhancing Gas Absorption with Nanoengineered Surfaces for Bubble Manipulation

Abstract

Efficiently reacting gases with liquid absorbents is a crucial aspect of numerous industrial processes on a large scale. When the gas phase is in the form of discrete bubbles within an absorber unit, such as in bubble column absorbers or gas sparging systems, the effectiveness of these bubbles' reaction depends on carefully controlling their properties and flow. This study demonstrates the efficacy of a novel method for gas absorption into a liquid absorbent, which involves using nanoengineered surfaces to spread bubbles into their texture and enhance mass transport between the gas and liquid phases. This surface-enhanced direct injection approach for gas absorption yields more than a two-order-of-magnitude improvement in reaction rate compared to captive bubbles when using a moderately alkaline potassium hydroxide as an absorbent solution for carbon dioxide gas. While the average reaction rates of non-spreading bubbles typically decrease with bubble size, the surface-enhanced absorption of spreading bubbles reverses this trend, enabling the most rapid absorption for the smallest bubbles. Moreover, non-spreading carbon dioxide bubbles cannot be fully absorbed due to product aggregation at their interface, whereas spreading bubbles can avoid this regime by reacting more quickly than the aggregation process on rapid timescales. Finally, we propose this surface-enhanced direct injection method as an absorption technique that scales advantageously for small-scale or distributed modular absorber designs compared to the traditional large-scale absorber units currently used in industry.