Enzymatic reactive absorption of CO₂ in MDEA by means of an innovative biocatalyst delivery system

Due to the increasing world population and industrialization the worldwide energy requirement is also increasing. About 82% of the world's total primary energy supply stems from fossil sources and coal combustion in power plants accounted for 46% of the 32.4 Gt global carbon dioxide (CO2) emissions in 2014 (International Energy Agency, Key CO2 Emissions Trends: Excerpt from CO2 Emissions from Fuel Combustion (2016 edition)). The reduction of CO2 emissions from power plant flue gases is therefore essential to enable reliable and ecologically benign energy supply. An efficient technology to reduce CO2 emissions is reactive absorption in packed columns with aqueous amine-based absorption solvents, herein also called absorbents. The major drawback of conventional amine absorbents is their high absorption enthalpy, which causes high energy requirements during solvent regeneration. Alternative solvents that offer significantly lower absorption enthalpies suffer from lower absorption rates. To compensate for low absorption rates the enzyme carbonic anhydrase (CA) can be added to the absorbent to accelerate absorption kinetics by catalyzing the reaction between CO2 and water. For industrial applications, it can be desirable to immobilize CA which extends enzyme longevity by confining the enzyme to favorable process conditions, prevents unnecessary exposure to high process temperatures, and enables enzyme reuse. The CO2 absorption characteristics and handling properties of an innovative immobilized CA in the form of microparticles, called biocatalyst delivery system (BDS), were evaluated together with aqueous MDEA solvent. Operational feasibility parameters were validated in lab scale, followed by replicated CO2 absorption performance tests in a small demonstration scale counter-current packed column. A sixfold enhancement in total absorbed mole flow of CO2 in the presence of BDS was demonstrated versus blank MDEA solvent. Recyclability and longevity of BDS were validated.

Subjects

Carbon dioxide capture

Carbonic anhydrase biocatalyst

Energy efficiency

Enzymatic reactive absorption

Immobilization

Packed column

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Enzymatic reactive absorption of CO₂ in MDEA by means of an innovative biocatalyst delivery system