2 research outputs found
Determination and Measurements of Mass Transfer Kinetics of CO<sub>2</sub> in Concentrated Aqueous Monoethanolamine Solutions by a Stirred Cell
The gas–liquid reaction rate was determined with
a stirred cell from the fall in pressure and the reaction rate constant
was determined by two data treatment methods, viz. a “differential”
and an “integral” method. The liquid-side mass transfer
coefficient without chemical reaction in the stirred cell reactor
was determined via the pressure drop method. The kinetics of the reaction
of carbon dioxide with aqueous monoethanolamine (MEA) solutions over
a wide concentration range from 0.5 to 12 M at a temperature range
from 298.15 to 323.15 K were studied using a stirred cell absorber
with a plane gas–liquid interface. Low CO<sub>2</sub> partial
pressure (3–4 kPa) was employed to satisfy the criterion for
a pseudo-first-order reaction. Very low inert gas pressures of N<sub>2</sub> and solution vapor were kept, and the stirrer was sped up
to reduce the gas-phase resistance. The results showed that the investigated
reactions took place in the pseudo-first-order fast reaction regime.
The reaction rate constant obtained for MEA with CO<sub>2</sub> at
298.15 K agrees with literature. The reaction activation energy (<i>E</i><sub>a</sub>) of aqueous MEA + CO<sub>2</sub> is 44.89
kJ mol<sup>–1</sup>, and the pre-exponential factor value is
4.14 Ă— 10<sup>11</sup>. The enhanced mass transfer coefficient
in the liquid phase, <i>k</i><sub>L</sub><i>E</i>, initially increases with the concentration of MEA solutions but
decreases when the molarity of MEA is higher than 8 M
Measurements and Correlations of Diffusivities of Nitrous Oxide and Carbon Dioxide in Monoethanolamine + Water by Laminar Liquid Jet
The molecular diffusivities of nitrous oxide (N<sub>2</sub>O) with
aqueous monoethanolamine (MEA) solutions up to 12 M were studied over
a temperature range from 298.15 to 333.15 K under atmospheric pressure
using a laminar liquid jet absorber. The diffusivities of CO<sub>2</sub> in aqueous MEA solutions were calculated by the “N<sub>2</sub>O analogy” method. A simple and effective thermal control
technique was used to control the temperatures of gas and liquid in
the laminar liquid jet absorber. The rates of absorption were determined
by measuring the flow of gas needed to replace the gas absorbed. The
results showed that the diffusivities of both N<sub>2</sub>O and CO<sub>2</sub> into aqueous MEA solution decrease with the increase of the
concentration of MEA, and increase with an increase of the temperature
of the solution. The relationship between the diffusivity and the
viscosity of the solution roughly agrees with the modified Stokes–Einstein
equation, but an exponent mathematical model was employed to simulate
the diffusivity data and shows a better agreement between data and
model for the diffusivity of N<sub>2</sub>O and CO<sub>2</sub> in
the monoethanolamine + water system