(572g) Carbonic Anhydrase Enhanced Carbon Capture: Kinetic Measurements and Pilot Plant  Trials

Carbonic
Anhydrase Enhanced Carbon Capture: Kinetic Measurements and Pilot Plant  Trials

Arne Gladis^1*,
Maria T Gundersen², Philip L Fosbøl¹, John M Woodley²,
Nicolas von Solms¹

1)                             
Center for Energy
Resources Engineering, Department of Chemical and Biochemical Engineering,
Technical University Denmark, Kgs. Lynby 2800

2)                             
CAPEC-PROCESS Center,
Department of Chemical and Biochemical Engineering, Technical University
Denmark, Kgs. Lyngby 2800

Keywords:

Wetted wall
column, carbonic anhydrase, carbon capture, enzyme kinetics, amine, carbonate,
absorption, carbon dioxide

Abstract:

In this study the effect of carbonic anhydrase
addition on the absorption of CO₂ was investigated in a wetted wall
column apparatus. Four different solvents: MEA (a primary amine), AMP (a sterically
hindered primary amine), MDEA (a tertiary amine) and K₂CO₃
a carbonate salt solution were tested in concentrations from 5 to 50 wt%. Necessary
mass transfer parameters such as liquid side mass transfer coefficient and
solvent and enzyme reaction rates were determined in a temperature range from
298 to 328 K and benchmarked to a 30 wt% MEA solution.

The study reveals that the addition of the enzyme
carbonic anhydrase (CA) dramatically increases the liquid side mass transfer
coefficient for 30 wt% MDEA and 15 wt% K₂CO_3. 30 wt% AMP has
a moderate increase whereas 30 wt% MEA was unchanged. The results confirm that
bicarbonate forming solvent which do not produce carbamate benefit from CA. The
results reveal the impact of temperature in relation to CA. A temperature
increase resulted in lower liquid side mass transfer rate for 30 wt% MDEA and
15 wt% K₂CO₃ but in higher rate for 30 wt% AMP. The
overall first order enzyme reaction rate (s^-1) was linearly
dependent on enzyme concentration for 30 wt% MDEA and 15 wt% K₂CO₃
at 313 K. The derived enzymatic reaction rate constant k_enz (m³
kg^-1 s^-1) for 15 wt% K₂CO₃ at 313 K
was about 9 times higher than for 30 wt% MDEA and 10 times higher than for 30
wt% AMP. Temperature and concentration did not observably influence the
enzymatic rate constant in the concentration range of 5 to 15 wt% K₂CO₃.
The higher solvent concentration only led to a slightly higher reaction rate. A
solution with 20 wt% K₂CO₃ had almost 3 times higher enzyme
reaction rate compared to 15 wt% at 298 K and increased with temperature to
almost 5 times faster at 328 K. The enzymatic reaction rate for MDEA decreased
with both temperature and solvent concentration from 15 to 30 wt%. An increase
to 50 wt% resulted in a decrease in reaction rate due to less water present.

Pilot plant campaigns were carried out for different
solvents and conditions and the results were successfully modelled using intrinsic
data obtained from the wetted-wall column experiments