34 research outputs found
A Study of Mass Transfer Kinetics of Carbon Dioxide in (Monoethanolamine + Water) by Stirred Cell
AbstractThe gas phase resistance in a stirred cell was investigated to understand and avoid its influence on the measurement of the reaction kinetics. To validate the influence of gas phase resistance and the experimental conditions of pseudo first order reaction for Monoethanolamine (MEA) + CO2 system, low CO2 partial pressure under various inert gas pressure were employed for CO2 the absorption into 0.5, 1, 3 and 3.6M MEA solutions with H2O and ethyleneglycol as solvents, respectively. The absorption was investigated with the stirred cell based on a fall-in-pressure technique
Process intensification for post combustion COâ capture with chemical absorption: a critical review
The concentration of COâ in the atmosphere is increasing rapidly. COâ emissions may have an impact on global climate change. Effective COâ emission abatement strategies such as carbon capture and storage (CCS) are required to combat this trend. Compared with pre-combustion carbon capture and oxy-fuel carbon capture approaches, post-combustion COâ capture (PCC) using solvent process is one of the most mature carbon capture technologies. There are two main barriers for the PCC process using solvent to be commercially deployed: (a) high capital cost; (b) high thermal efficiency penalty due to solvent regeneration. Applying process intensification (PI) technology into PCC with solvent process has the potential to significantly reduce capital costs compared with conventional technology using packed columns. This paper intends to evaluate different PI technologies for their suitability in PCC process. The study shows that rotating packed bed (RPB) absorber/stripper has attracted much interest due to its high mass transfer capability. Currently experimental studies on COâ capture using RPB are based on standalone absorber or stripper. Therefore a schematic process flow diagram of intensified PCC process is proposed so as to motivate other researches for possible optimal design, operation and control. To intensify heat transfer in reboiler, spinning disc technology is recommended. To replace cross heat exchanger in conventional PCC (with packed column) process, printed circuit heat exchanger will be preferred. Solvent selection for conventional PCC process has been studied extensively. However, it needs more studies for solvent selection in intensified PCC process. The authors also predicted research challenges in intensified PCC process and potential new breakthrough from different aspects
Gas Treating
Gas Treating: Absorption Theory and Practice provides an introduction to the treatment of natural gas, synthesis gas and flue gas, addressing why it is necessary and the challenges involved. The book concentrates in particular on the absorption-desorption process and mass transfer coupled with chemical reaction. Following a general introduction to gas treatment, the chemistry of CO2, H2S and amine systems is described, and selected topics from physical chemistry with relevance to gas treating are presented. Thereafter the absorption process is discussed in detail, column hardware is explai
Gas treating: absorption theory and practice
Gas Treating: Absorption Theory and Practice provides an introduction to the treatment of natural gas, synthesis gas and flue gas, addressing why it is necessary and the challenges involved. The book concentrates in particular on the absorption-desorption process and mass transfer coupled with chemical reaction. Following a general introduction to gas treatment, the chemistry of CO2, H2S and amine systems is described, and selected topics from physical chemistry with relevance to gas treating are presented. Thereafter the absorption process is discussed in detail, column hardware is explai
Ultrasound intensify CO2 desorption from pressurized loaded monoethanolamine solutions. II. Optimization and cost estimation
acceptedVersio
Density Measurements of Unloaded and CO<sub>2</sub>âLoaded 3âAmino-1-propanol Solutions at Temperatures (293.15 to 353.15) K
The
first part of this work presents experimental density data
of aqueous 3-amino-1-propanol (3A1P) solutions at different compositions
and temperatures of (293.15 to 353.15) K. It was found that densities
decreased with increasing temperatures and were concentration dependent.
Excess molar volumes of aqueous 3A1P were also established. Five different
methods were compared for correlating density data of unloaded 3A1P
solutions. In the second part of this work, densities of CO<sub>2</sub>-loaded solutions were measured at 0.1 and 0.5 mass fractions of
3A1P at increasing temperatures and CO<sub>2</sub>-loadings. Two different
models were used to regress these experimental data. The suitability
of these methods to represent densities of unloaded and CO<sub>2</sub>-loaded 3A1P solutions is evaluated
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 âN<sub>2</sub>O analogyâ 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 StokesâEinstein
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
Determination and Measurements of Mass Transfer Kinetics of CO<sub>2</sub> in Concentrated Aqueous Monoethanolamine Solutions by a Stirred Cell
The gasâliquid 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 âdifferentialâ
and an âintegralâ 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 gasâliquid interface. Low CO<sub>2</sub> partial
pressure (3â4 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>â1</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
Model uncertainty of interfacial area and mass transfer coefficients in absorption column packings
Uncertainty in model input parameters propagates through the model to make model output imprecision. Here, mathematical models used to calculate interfacial area and mass transfer coefficient for both random and structured packing in a packed bed absorption column was studied to investigate the propagation of model input parameters of viscosity, density and surface tension through the models. Monte Carlo simulation was used to examine the uncertainty propagation, and expectation E(Y) and standard deviation s for the model output values were determined. This study reveals ±5% model output uncertainty for mass transfer coefficient and ±3.7% uncertainty for interfacial area for the Onda, Bravo and Fair models used in random packings. Further, the analysis predicts ±1.3% of uncertainty for interfacial area and ±0.8% of uncertainty for mass transfer coefficient for the Rochaâs correlations used in structured packings
Free Energies of Activation for Viscous Flow of Different Amine Mixtures in Post Combustion CO2 Capture
The viscosity of ternary mixtures of N-methyldiethanol amine (MDEA) + monoethanol amine (MEA) + H2O, Nmethyldiethanol amine (MDEA) + diethanol amine (DEA) + H2O and 2-amino-2-methyl-1-propanol (AMP) + diethanol amine (DEA) + H2O were correlated using Eyringâs viscosity model based on absolute rate theory. The correlations were capable of representing viscosity data within AARD 1.9%, 1.4% and 2.1% for the mixtures MDEA + MEA + H2O, MDEA + DEA + H2O and AMP + DEA + H2O respectively. These accuracies are acceptable in engineering calculations. The excess properties of volume , viscosity and free energy of activation for viscous flow Îâ were studied to understand the intermolecular interactions in the mixtures. The study shows that all mixtures have a negative sign for , and a positive sign for Îâ. This indicates weak intermolecular interactions in mixtures compared to the pure liquids and strong molecular attractions like H-bonds in the mixtures