4 research outputs found
Application of Electrolyte-NRTL Model for Prediction of the Viscosity of Carbon Dioxide Loaded Aqueous Amine Solutions
A method
based on the absolute-rate theory has been used and tested
for estimation of the dynamic viscosity of CO<sub>2</sub> loaded aqueous
solutions of a representative amine: monoethanolamine (MEA). In this
approach the electrolyte-NRTL model is applied to estimate the activation
free energy of the solution and consequently enable prediction of
the dynamic viscosity of the strong electrolyte CO<sub>2</sub>:MEA:H<sub>2</sub>O system. Three different concentrations of the aqueous MEA
solutions with 20, 30, and 43 wt %, in the temperature range from
40 to 70 °C, and CO<sub>2</sub> loadings from 0.1 to 0.5 mol
of CO<sub>2</sub>/mol of amine were selected for the model investigation.
The model displays a reasonable prediction ability from experimental
viscosity data in the whole range of system variables. It is shown
that the activation free energy for the flow process can be closely
estimated through the Gibbs free energy of mixing with a correction
on the sign of the energy term in the model equation from positive
to negative. The result reveals that, having a reliable thermodynamic
model for a selected solution, the absolute-rate-theory approach is
applicable for estimation of the viscosities of strong electrolyte
systems such as CO<sub>2</sub> loaded alkanolamine solutions at different
solution concentrations, temperatures, CO<sub>2</sub> loadings, and
operating pressures for various amines and amine blends
The Equilibrium Solubility of Carbon Dioxide in Aqueous Solutions of Morpholine: Experimental Data and Thermodynamic Modeling
Experimental
carbon dioxide solubility data in aqueous 34.8 wt % (6.14 m) and 43.5
wt % (8.85 m) morpholine solutions at 40, 60, 100, and 120 °C
are presented. The solubility measurements were done in a static vapor
liquid equilibrium cell by measuring total pressure. Furthermore,
selected data points were confirmed using gas phase GC methodology.
The obtained combined solubility data was integrated with speciation
data extracted using an established titration method, for thermodynamic
modeling of the system. In regression of the model parameters, the
liquid phase activity coefficients were determined using the electrolyte-NRTL
equations. In addition to binary and pair interaction adjustable parameters
included in the electrolyte-NRTL model, the temperature dependent
carbamate stability and Henry’s law constants for CO<sub>2</sub> in pure morpholine were also calculated. The determined CO<sub>2</sub> equilibrium properties are in good agreement with most of the experimental
data
Facile Method for Determination of Amine Speciation in CO<sub>2</sub> Capture Solutions
A simple and quantitatively reliable method for determination
of
amine speciation is introduced. The method employs three experimental
methods that should be readily accessible. The results for CO<sub>2</sub> loaded aqueous solutions of 30 wt % monoethanolamine (MEA)
are used for demonstration of the method and show promising agreement
with the more complicated spectroscopic methods reported in the literature.
The measurements were done at ambient temperature and atmospheric
pressure, since theoretical calculations and experimental data from
the open literature revealed no considerable difference in speciation
at different temperatures. The procedure is based on acid and base
titration of the CO<sub>2</sub> loaded amine solution along with the
determination of total CO<sub>2</sub> loading. The quantitative results
for the different species concentration in the example MEA solution
is in agreement with other available spectroscopic methods, mainly
NMR, particularly for the free amine, carbamate, and protonated amine
concentrations. Aspen Plus was also used for further assessment of
the experimental data
Morpholine Nitrosation To Better Understand Potential Solvent Based CO<sub>2</sub> Capture Process Reactions
The
amine assisted CO<sub>2</sub> capture process from coal fired
power plants strives for the determination of degradation components
and its consequences. Among them, nitrosamine formation and their
emissions are of particular concern due to their environmental and
health effects. The experiments were conducted using morpholine as
a representative secondary amine as a potential CO<sub>2</sub> capture
solvent with 100 ppm standard NO<sub>2</sub> gas to better understand
the nitrosamine reaction pathways under scrubber and stripper conditions.
The role of nitrite in the nitrosation reaction was probed at elevated
temperatures. The effects of different concentrations of nitrite on
morpholine were evaluated. Formation rate, decomposition rates, activation
energy, and the possible reaction pathways are elaborated. Thermal
stability tests at 135 °C indicated the decomposition of nitrosamines
at the rate of 1 μg/(g h) with activation energy of 131 kJ/mol.
The activation energy for the reaction of morpholine with sodium nitrite
was found as 101 kJ/mol. Different reaction pathways were noted for
lower temperature reactions with NO<sub>2</sub> gas and higher temperature
reactions with nitrite