“CO2 absorption enhancement by the enzyme carbonic anhydrase”
Abstract:
Carbon capture and storage technology (CCS) can help mitigate CO2 emissions from large emitters like cement/steel industry and fossil fuel burning power plants by removing this compound out of a gas stream and storing it beneath the surface. The solvent based absorption/desorption is clearly the most mature option within this technology, but there remain many attempts to make this process economically more viable by reducing the projected capital and operating costs. The capital costs can be reduced by equipment downsizing which can be achieved by increasing the absorption/desorption rate, since a smaller mass transfer interface is needed in the absorber/desorber (resulting in smaller dimensions). Another approach is the use of solvents with low heats of reaction which can reduce the energy requirement for the regeneration process of the solvent and thereby lower the operating costs that make the biggest contribution to the overall cost, but these kinds of solvents often show bad absorption kinetics.
The enzyme carbonic anhydrase has drawn some attention in the field of carbon capture over the recent years as it can help increase the absorption rate for slow chemical solvents several-fold. This effect is possible, because the enzyme catalyzes the reversible reaction between dissolved CO2, water and bicarbonate. The complex reaction mechanism of carbonic anhydrase can be simplified to the following overall reaction:
CO2 + H2O ßà HCO3- + H+
In the field of chemical solvents several types produce bicarbonate in the absorption process, like alkaline salt solutions, tertiary amines and sterically hindered amines. These solvents follow different reaction mechanisms with CO2 alone and the effect of supplementing carbonic anhydrase on the absorption rate is not yet fully understood.
The intention of this morning seminar is to explain the main principles behind using the enzyme carbonic anhydrase in the CCS process and showing first results obtained from absorption experiments with the gas liquid contactor “wetted wall column”.