CFD Study of Particle Flow Patterns in a Rotating Cylinder Applying OpenFOAM and Fluent

A rotating cylinder (RC) is a common type of reactor used in the industry, the most typical example being a cement kiln. The particle flow pattern inside such a unit is necessary for the mass and energy transfer, and this flow pattern depends on the operational Froude number and the degree of filling. The main aim of this study is to compare the simulation results from OpenFOAM and Fluent applying a Eulerian multiphase flow modeling concept to study the behavior of dense particle gas mixtures under different operational conditions. Six different flow patterns are simulated, varying the degree of filling from 10 to 45 % and the Froude number from 0.0001 to 5. OpenFOAM is capable of producing results very close to those generated with Fluent, and both software appears to be suitable for simulating the RC dense particle flow using the Eulerian approach

Simulation and Impact of different Optimization Parameters on CO2 Capture Cost

The influence of different process parameters/factors on CO2 capture cost, in a standard amine based CO2 capture process was studied through process simulation and cost estimation. The most influential factor was found to be the CO2 capture efficiency. This led to investigation of routes for capturing more than 85% of CO2. The routes are by merely increasing the solvent flow or by increasing the absorber packing height. The cost-efficient route was found to be by increasing the packing height of the absorber. This resulted in 20% less cost compared to capturing 90% CO2 by increasing only the solvent flow. The cost optimum absorber packing height was 12 m (12 stages). The cost optimum temperature difference in the lean/rich heat exchanger was 5 °C. A case with a combination of the two cost optimum parameters achieved a 4% decrease in capture cost compared to the base case. The results highlight the significance of performing cost optimization of CO2 capture processes.publishedVersio

Physicochemical data for amine based CO2 capture process

Amine based post-combustion carbon capture is a highly discussed CO2 removal method from flue gas. Large-scale CO2 capture facilities with effective solvents are required to make a significant impact on reducing CO2 emissions from power plants and existing facilities. Physical properties of solvents play a major role in designing process equipment. Measured properties like density, viscosity and surface tension are used in mathematical models developed for mass transfer and interfacial area that are used in designing absorption columns. Further, developed correlations to represent measured physical properties are useful in process simulations. This work presents measured density and viscosity data of both CO2 loaded and non-loaded aqueous amine mixtures at different amine concentrations, temperatures and CO2 loadings. Density and viscosity increase with the increase of CO2 loading and decrease with the increase of temperature. The excess volume of binary and ternary aqueous amine mixtures was calculated from measured density data and correlated using a Redlich-Kister type polynomial. A density correlation proposed by Aronu was adopted to correlate densities of MEA + H2O mixtures. A correlations based on density deviation were proposed for MDEA + H2O, DMEA + H2O and DEEA + H2O mixtures. Aronu’s density correlation was modified to fit densities of MEA + H2O + CO2 mixtures. For AMP + MEA + H2O + CO2 mixtures, density was correlated using a modified Weiland’s correlation and a Setschenow type correlation. The accuracies of density data fits were satisfactory as the average absolute relative deviation (AARD) was typically less than 1% and correlations are suitable to perform engineering calculations. Eyring’s viscosity model based on Eyring’s absolute rate theory was adopted to calculate the free energy of activation for viscous flow ∆0+ of CO2 loaded and non-loaded aqueous amine mixtures. Further, the excess free energy of activation for viscous flow ∆0+ was calculated and a Redlich-Kister type polynomial was proposed to fit the measured viscosities of aqueous amine mixtures. For the mixtures of MEA + H2O + CO2 and AMP + MEA + H2O + CO2, empirical correlations were proposed to fit calculated ∆0+ from Eyring’s viscosity model and then the correlation was used to represent the measured viscosities. The viscosity deviation was determined for aqueous amine mixtures to investigate types of intermolecular interactions in the mixtures. Further, a modified Weiland’s correlation and a Setschenow type correlation were proposed to correlate viscosities of AMP + MEA + H2O + CO2 mixtures. The accuracies of the viscosity data fits were typically less than 2% AARD and the proposed correlations can be recommended to use in engineering calculations. The approach of using feedforward backpropagation artificial neural networks (ANNs) to represent densities and viscosities of CO2 loaded and non-loaded aqueous amine solutions gained high accuracies in data fit compared to the conventional empirical correlations. The ANNs are with multiple inputs of mole fractions of amines, CO2 and temperature of the mixtures, one hidden layer and one output that is either density or viscosity of the mixtures. The optimum number of neurons in the hidden layer was found by calculating Mean Squared Error (MSE) over thirty neurons. The experiments performed in a CO2-rig located at USN Porsgrunn illustrates the variations of density and viscosity at the top and the bottom of the absorber column at different liquid flow rates. The density of the solvent increased although the temperature increased due to the exothermal reaction between CO2 and MEA. The influence of temperature increase caused to decrease the viscosity at the bottom of the column even the CO2 loading is higher than at the top of the column. Process simulations were performed to predict the variations of density and viscosity of the column

Impact of Uncertainty of Physical Properties on CO2 Absorption Design

The mass transfer coefficients, interfacial area and pressure drop of a packed bed are essential properties that need to be evaluated prior to the design of a CO2 absorption column. Various mathematical models have been proposed to predict these properties under different process conditions. This work has compared several mathematical models for pressure drop, mass transfer coefficients and interfacial area and discussed how the uncertainty of physical properties and process conditions affect the evaluation of packed bed height in a CO2 absorption column. A case study has been performed to study the propagation of uncertainty in input variables through the packed bed height design equations. Here, it was found as 12% from uncertainty in physical properties and 60% from uncertainty in choice of mathematical model of the calculated packed bed height. A recommended safety factor for the absorption packing height is 60 % for a generic packing, but this safety factor can be reduced considerably if experimental data for pressure drop and mass transfer coefficients are available for the specific packing

Applicability of NRTL Model for Prediction of the Viscosity of Alkanolamine + Water Mixtures

This study discusses the applicability of the non-random two-liquid (NRTL) model to represent viscosity for MEA (monoethanol amine) + H2O and AMP (2-amino-2-methyl-1-propanol) + MEA (monoethanol amine) + H2O mixtures under different amine concentrations at temperature ranges of 293.15 K– 363.15 K and 293.15 K – 343.15 K respectively. The NRTL model is adopted to determine excess Gibbs free energy of mixing and the Eyring’s viscosity model based on absolute rate theory is used to obtain excess free energy of activation for viscous flow. The correlations are proposed for the viscous flow as a function of concentration of the components, temperature and Gibbs free energy. Correlations are capable of representing measured viscosities at 1.3% and 0.3% of absolute average relative deviation (AARD %) for MEA + H2O and AMP + MEA + H2O mixtures respectively. These deviations are acceptable for engineering calculations and correlations can be used in process design and simulations like Aspen HYSYS and ASPEN Plus

Density and Viscosity Correlations for Aqueous 3-Amino-1-propanol and Monoethanol Amine Mixtures

Density and viscosity data and relevant correlations are essentially needed to perform mathematical modelling and simulations for the design of process equipment. Correlations that are developed to cover a range of concentrations and temperatures help to use them in mathematical modelling and simulations of absorption - desorption processes. In this study, a density correlation was proposed for 3A1P (3-Amino-1-propanol) + H2O mixtures. The McAllister three body model was adopted to correlate kinematic viscosity data of MEA (monoethanol amine) + H2O mixtures and kinematic viscosity data for 3A1P + H2O mixtures. The Eyring’s viscosity model based on absolute rate theory was used to correlate dynamic viscosity data. A Redlich – Kister type polynomial was proposed to fit the excess free energy of activation for viscous flow for 3A1P + H2O mixtures. The developed correlations were able to represent density and viscosity data with accepted accuracy and can be used to perform engineering calculations

Aspen Hysys and Aspen Plus Simulations for Amine Based Absorption Process Compared to Results from Experiments in CO2-RIG

In this study, equilibrium-based and rate-based simulations in Aspen HYSYS and Aspen Plus were performed to compare the removal efficiency and physical properties of density and viscosity in a CO2 absorption column. The experimental results from our previous study were used for comparison. In the equilibrium-based simulations, removal efficiency at 40 kg/hr of solvent flow rate was fitted with simulation by adjusting the Murphree efficiency of 12% in all stages. Accordingly, the equilibrium-based performed for other considered flow rates by keeping adjusted constant Murphree efficiency for all the stages in the absorber column. The variations of physical properties like density and viscosity were simulated and compared with measured properties under three different liquid to gas (L/G) ratios. Performed rate-based simulations with default molar volume/density and viscosity models of Clarke model and Jones-Dole model respectively were able to predict the properties with acceptable accuracy, but a deviation of 25% between measured and simulated viscosities for the lean MEA mixture was observed

Aspen Hysys and Aspen Plus Simulations for Amine Based Absorption Process Compared to Results from Experiments in CO2-RIG

In this study, equilibrium-based and rate-based simulations in Aspen HYSYS and Aspen Plus were performed to compare the removal efficiency and physical properties of density and viscosity in a CO2 absorption column. The experimental results from our previous study were used for comparison. In the equilibrium-based simulations, removal efficiency at 40 kg/hr of solvent flow rate was fitted with simulation by adjusting the Murphree efficiency of 12% in all stages. Accordingly, the equilibrium-based performed for other considered flow rates by keeping adjusted constant Murphree efficiency for all the stages in the absorber column. The variations of physical properties like density and viscosity were simulated and compared with measured properties under three different liquid to gas (L/G) ratios. Performed rate-based simulations with default molar volume/density and viscosity models of Clarke model and Jones-Dole model respectively were able to predict the properties with acceptable accuracy, but a deviation of 25% between measured and simulated viscosities for the lean MEA mixture was observed.publishedVersio

Comparison of the influence of drag models in CFD simulation of particle mixing and segregation in a rotating cylinder

CFD modelling was used to simulate particle segregation in a transverse plane of a rotating cylinder under different particle-particle drag models. The Eulerian method was used to model the dense particulate phases in the system. Two types of particles, with different density and size, were used in the study. The simulations were performed under the rolling mode since this mode is believed to give good particle-particle mixing. The drag models of Schiller-Naumann, Morsi- Alexander and Syamlal-O’Brien Symmetric were applied in the modelling of particle-particle drag and results were compared with experiments. All the drag models were able to model the particle segregation. The Schiller-Naumann model and the Morsi-Alexander model showed good agreement with the experimental results while the Syamlal-O’Brien-Symmetric model had some deviations

Physical Properties of MEA + Water + CO2 Mixtures in Postcombustion CO2 Capture: A Review of Correlations and Experimental Studies

The knowledge of physicochemical properties of a mixture of amine, water, and CO2 is beneficial in evaluating the postcombustion CO2 capture process and process equipment design. This study reviews the literature of density, viscosity, and surface tension measurements with the evaluated measurement uncertainties and proposed correlations for monoethanol amine (MEA), water, and CO2 mixtures. Adequate research has been performed to measure and develop correlations for pure MEA and aqueous MEA mixtures, but further studies are required for CO2-loaded aqueous MEA mixtures. The correlations fit measured properties with an acceptable accuracy, and they are recommended to use in process equipment design, mathematical modelling, and simulations of absorption and desorption