Contents lists available at ScienceDirect International Journal of Greenhouse Gas Control journal homepage: www.elsevier.com/locate/ijggc Enzymatic CO 2 capture in countercurrent packed-bed column reactors with high performance random packings Ion Iliuta, Maria C. Iliuta ⁎ Department of Chemical Engineering, Laval University, Québec, Canada G1V 0A6 ARTICLE INFO Keywords: CO 2 removal Countercurrent random packed-bed column reactor Fourth generation random packings Carbonic anhydrase enzyme Modeling ABSTRACT Packed-bed columns with immobilized human carbonic anhydrase II (hCA II) enzyme on fourth generation random packings offer an attractive way to implement CO 2 capture because of low pressure drop, high capacities and extremely large and uniform open area in every ring orientation. Enzyme-based CO 2 removal performance of countercurrent packed-bed column reactors was analyzed by means of a dynamic 3D model which links the macroscopic volume-averaged continuity, momentum and species balance equations in the liquid and gas phases with simultaneous diffusion and chemical reaction at the enzyme washcoat/liquid film scale level. The results reveal that this low-cost, green, and environmentally friendly technology could be an interesting option to CO 2 removal. The performance of packed-bed column reactors with immobilized hCA II enzyme on fourth generation random packings can be enhanced by diminishing the washcoat thickness, increasing the inlet buffer con- centration and pK a constant and increasing the liquid velocity conserving a low pressure drop level. Also, op- eration with extra hCA II loadings allows to obtain higher CO 2 conversion and avoids the deterioration of the CO 2 hydration rate in long-term operation attributable to the decrease of hCA II enzyme activity. 1. Introduction Global warming and climate change issues are notable concerns for the worldwide community. The high level of CO 2 concentration in the atmosphere is responsible for global warming – according to 2014 Intergovernmental Panel on Climate Change report (IPCC, 2014) CO 2 emissions in 2010 counted for 76% of the total anthropogenic green- house gas, CH 4 contributed with 16%, N 2 O with circa 6% and the combined fluorinated gases with almost 2%. The major sources of CO 2 emissions include power plants, petroleum refinery, cement, steel and aluminum production processes, ammonia and hydrogen plants (Rambo et al., 2014). In these conditions, CO 2 capture is considered as promising way for reducing industrial CO 2 emissions by capturing CO 2 from major sources and injecting it into underground reservoirs or re- utilization in enhanced oil recovery, food processing or accelerated algae growth (Rambo et al., 2014; Liang et al., 2016). At present several alternate CO 2 capture technologies are in dif- ferent phases of development and commercial practice (Rambo et al., 2014). These include chemical and physical absorption processes, membrane separation, cryogenic distillation and mineral carbonation. CO 2 capture in typical gas–liquid reactors via chemical absorption using aqueous amine solutions (particularly monoethanolamine, diethanola- mine, di-2-propanolamine and 2-amino-2-methyl-1-propanol) is extensively used in conventional CO 2 post-combustion processes due to the considerable absorption activity, economic efficiency, ability to deal with large volumes of gas and ability to be integrated into existing systems (Kohl and Nielsen, 1997; Luis et al., 2012; Rambo et al., 2014; Liu et al., 2014; Liang et al., 2016; Iliuta and Iliuta, 2017). CO 2 ab- sorption in MEA solutions is considerably fast, and thus commercially preferred, but the energy requirement for the regeneration (about 4 million BTU/ton of CO 2 ) accounts for nearly 70–80% of the total run- ning cost of CO 2 capture process and poses a big challenge in this field for many years (Rambo et al., 2014; Liang et al., 2016). Equilibrium limitations, amine degradation, formation of oxidative degradation products and equipment corrosion are additional drawbacks of the process, generally given by the aqueous moiety (Strazisar et al., 2003; Soosaiprakasam and Veawab, 2008; Jackson and Attalla, 2011; Penders-van Elk et al., 2012; Bougie and Iliuta, 2014). Because of the excessive energy demand in the amine regeneration process alternative approaches able to reduce the cost of CO 2 capture process and minimalize the environmental impacts are needed. One emerging alternative to amines CO 2 absorption–desorption process is the use of biocatalysts to catalyze CO 2 hydration process. An option is the utilization of carbonic anhydrase enzyme, omnipresent in nature, which reversibly convert CO 2 into bicarbonate via a CO 2 hydration process near the limits imposed by diffusion because of the very large http://dx.doi.org/10.1016/j.ijggc.2017.04.009 Received 18 December 2016; Accepted 18 April 2017 ⁎ Corresponding author. E-mail address: maria-cornelia.iliuta@gch.ulaval.ca (M.C. Iliuta). International Journal of Greenhouse Gas Control 63 (2017) 462–474 1750-5836/ © 2017 Elsevier Ltd. All rights reserved. MARK