Department of Chemical and Biochemical Engineering

Publications

Contributions to books


Efficient Carbon Capture for Coal Power Plants, Edited by Stolten and Scherer, (Wiley-VCH 2011), Chapter on “Chemical Absorption Materials for CO2 capture”  p155-174 by Kaj Thomsen

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Chemical Thermodynamics for Industry, (RSC books, 2004), Edited by T.M. Letcher
Chapter on "Thermodynamics of Electrolyte Systems of Industry" by Kaj Thomsen
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Kemiske Enhedsoperationer 5. udgave (2004, 2009 2. oplag, Chemical Unit Operations, Language: Danish)
Authors: Karsten H. Clement, Peder Fangel, Anker Jensen, Kaj Thomsen 
Rettelsesliste
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Electrolyte Solutions: Thermodynamics, Crystallization, Separation methods (Free download of course material)
Teaching material for course 28928 on Aqueous Electrolyte Thermodynamics.
Author: Kaj Thomsen
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Papers, reports, and thesis

 

Arrad, Mouad; Kaddami, Mohammed; El Goundali, Bahija; Thomsen, Kaj, Solubility Modeling of the Binary Systems Fe(NO3) 3-H2O, Co(NO3)2-H2O and the Ternary System Fe(NO3)3-Co(NO3)2-H2O with the Extended Universal Quasichemical (UNIQUAC) Model, Journal Of Solution Chemistry, 45(2016)534–545 (Issue 4).

ABSTRACT:

Solubility modeling in the binary systems Fe(NO3) 3-H2O, Co(NO3)2-H2O and the Ternary System Fe(NO3)3-Co(NO3)2-H2O is presented. The extended UNIQUAC model was applied to the thermodynamic assessment of the investigated systems. The model parameters obtained were regressed simultaneously using the available databank but with more experimental points, recently published in the open literature. A revision of previously published parameters for the cobalt ion and new parameters for the iron(III) nitrate system are presented. Based on this set of parameters, the equilibrium constants of hydrates are determined. The model represents the experimental data with good accuracy from the freezing point region to the boiling points of the solutions.

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Bonalumi, Davide; Valenti, Gianluca; Lillia, Stefano; Fosbol, Philip L.; Thomsen, Kaj, A Layout for the Carbon Capture with Aqueous Ammonia without Salt Precipitation, Energy Procedia, 86(2016)134–143.

ABSTRACT:

Post-combustion carbon capture technologies seem to be necessary to realize the CO2 mitigation policies internationally shared for the next future, despite none of them appears to be ready for full-scale applications. This work considers the aqueous ammonia based process for a coal-fired Ultra Super Critical power plant. Two layouts are simulated with Aspen Plus employing the recently recalibrated Extended UNIQUAC thermodynamic model. The first one operates at chilling conditions, which yield to salt precipitation, and is taken as reference because already analyzed in previous studies. The second layout operates at cooled conditions, which does not yield any salt precipitation. The Chilled layout reveals low specific heat duty and SPECCA equal to 2.2 and 2.86 MJ/kgco2, respectively. In contrast, the Cooled layout presents a higher specific heat duty of almost 3 MJ/kgco2 but, importantly, a lower SPECCA of 2.58 MJ/kgco2. The latter layout is a better choice also from the perspective of the plant operation since it does not present the salt precipitation.

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Gaspar, Jozsef; Gladis, Arne; Jorgensen, John Bagterp; Thomsen, Kaj; von Solms, Nicolas; Fosbol, Philip Loldrup, Dynamic Operation and Simulation of Post-Combustion CO2 Capture, Energy Procedia, 86(2016)205–214.

ABSTRACT:

Thermal power need to operate, on a daily basis, with frequent and fast load changes to balance the large variations of intermittent energy sources, such as wind and solar energy. To make the integration of carbon capture to power plants economically and technically feasible, the carbon capture process has to be able to follow these fast and large load changes without decreasing the overall performance of the carbon capture plant. Therefore, dynamic models for simulation, optimization and control system design are essential. In this work, we compare the transient behavior of the model against dynamic pilot data for CO2 absorption and desorption for step-changes in the flue gas flow rate. In addition we investigate the dynamic behavior of a full-scale post-combustion capture plant using monoethanolamine (MEA) and piperazine (PZ). This analysis demonstrates the good agreement between the developed model (dCAPCO2) and the pilot measurements at both, transient and steady-state conditions. It outlines how the time needed to reach a new steady-state varies with respect to amine type and concentration. The simulation study reveals that it is essential to control the lean solvent flow to avoid sudden changes in the CO2 removal rate and to avoid increased heat demand of solvent regeneration. In addition, it shows how storage tanks (liquid hold-up of the system) can be designed to accommodate significant upstream changes in the power plant management. This flexibility is especially needed for operation in future mixed green energy market.

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Gaspar, Jozsef; von Solms, Nicolas; Thomsen, Kaj; Fosbol, Philip Loldrup, Multivariable Optimization of the Piperazine CO2 Post-Combustion Process, Energy Procedia, 86(2016)229–238.

ABSTRACT:

8 molal piperazine (PZ) is a promising solvent for developing an energy efficient CO2 post-combustion capture process. However, it has a limited operating range due to precipitation. The operating range can be extended by decreasing the piperazine concentration and/or increasing the CO2 loading of the lean solvent. However, optimal solvent composition must be determined taking into account the solvent circulation rate and the heat demand of the solvent regeneration. In this paper, we determine and generalize trends of performance for a broad range of operating conditions: 1.8 to 9 mol PZ/kg water, 0.2 to 0.6 lean loading, and for two flue gas sources: natural gas combined cycle power plant (NGCC, 3.9 mol% CO2) and a coal based power plant (ASC, 13.25 mol% CO2). Special attention is given to the boundaries where precipitation may occur. The results are created by the hybrid CAPCO2 rate-based model which accounts for precipitation when estimating the heat and mass transfer rates. The results show that the 7 molal piperazine gives the lowest specific reboiler duty at 0.40 CO2 lean loading: 3.32 GJ/t CO2 and 4.05 GJ/t CO2 for the ASC case and NGCC cases. The analysis also reveals that the capture process needs to be operated up to 7.8 % above the minimum duty to avoid the risk of clogging due to solid formation. Note, this analysis assumes a 25 degrees C minimum solvent temperature. The energy requirement of the capture process can be further improved by assuming a minimum solvent temperature of 30 degrees C which gives a specific reboiler duty of 3.23 GJ/t CO2 (ASC case) and 3.80 GJ/t CO2 (NGCC case).

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Liang, Xiaodong; Yan, Wei; Thomsen, Kaj; Kontogeorgis, Georgios M., Modeling the liquid-liquid equilibrium of petroleum fluid and polar compounds containing systems with the PC-SAFT equation of state, Fluid Phase Equilibria, 406(2015)147–255.

ABSTRACT:

A critical test for the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (FOS) is the modeling of systems containing petroleum fluid and polar compounds. In this work, two approaches are proposed for the simplified PC-SAFT EOS to obtain the necessary pure component parameters for the characterized non-associating pseudo-components of petroleum fluids. New pure component parameters of mono-ethylene glycol (MEG) are obtained by considering the liquid liquid equilibrium (LLE) data of MEG with normal hydrocarbons in the estimation process and a simple binary interaction scheme of MEG with pseudo- components is proposed. These new parameters are applied to model LLE of the systems of petroleum fluid + MEG with or without water. The results show that the simplified PC-SAFT EOS yields promising predictions of the key mutual solubility of these systems: 15-18% overall deviations for the systems of petroleum fluid + MEG and 23-25% overall deviations for the systems of petroleum fluid + MEG + water. The two approaches are further studied in a more theoretical manner to show the relationship between the solubility of petroleum fluid in the polar phase and the PC-SAFT parameter segment diameter.

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Maribo-Mogensen, Bjorn; Thomsen, Kaj; Kontogeorgis, Georgios M., An electrolyte CPA equation of state for mixed solvent electrolytes, AIChE Journal, 61(2015)2933–2950.

ABSTRACT:

Despite great efforts over the past decades, thermodynamic modeling of electrolytes in mixed solvents is still a challenge today. The existing modeling frameworks based on activity coefficient models are data-driven and require expert knowledge to be parameterized. It has been suggested that the predictive capabilities could be improved through the development of an electrolyte equation of state. In this work, the Cubic Plus Association (CPA) Equation of State is extended to handle mixtures containing electrolytes by including the electrostatic contributions from the Debye-Huckel and Born terms using a self-consistent model for the static permittivity. A simple scheme for parameterization of salts with a limited number of parameters is proposed and model parameters for a range of salts are determined from experimental data of activity and osmotic coefficients as well as freezing point depression. Finally, the model is applied to predict VLE, LLE, and SLE in aqueous salt mixtures as well as in mixed solvents.

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Arrad, Mouad; Kaddami, Mohammed; Maous, Jaafar; Thomsen, Kaj, Modeling the binary system Mn(NO3)2-H2O with the extended universal quasichemical (UNIQUAC) model, Fluid Phase Equilibria, 397(2015)126–130.

ABSTRACT:

In this study, new experimental data for the binary system of Mn(NO3)2-H2O are presented in the temperature range from -29 degrees C to 35 degrees C at atmospheric pressure using the conductometric method, this synthetic method is an accurate experimental procedure in the determination of the solubility of salts in aqueous solutions. Thermodynamic modeling for the binary system of Mn(NO3)2-H2O is also presented based on this new experimental solubility data and some modification on the available data bank. Model parameters for this system were determined and revisited; these parameters are generally valid in the entire range of temperature and composition of the salt.

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Sadegh, Negar; Thomsen, Kaj; Solbraa, Even; Johannessen, Eivind; Rudolfsen, Gunn Iren; Berg, Ole Johan, Solubility of hydrogen sulfide in aqueous solutions of N-methyldiethanolamine at high pressures, Fluid Phase Equilibria, 393(2015)33–39.

ABSTRACT:

A static-analytic method was used to measure the H2S solubility in 50 wt% MDEA and in presence of methane as a makeup gas. The solubility was measured at 7000 kPa total pressure, and at 50 and 70 degrees C, for H2S partial pressures from 31 to 974 kPa. Measurements were also performed at 1500 kPa total pressure and 50 degrees C for H2S partial pressure span of 53-386 kPa. The measured data were compared to predictions using the Extended UNIQUAC model. The experimental data showed that the total pressure has a significant effect on H2S solubility in aqueous MDEA. The observed effect is shown to be dominated by the non-ideality of the gas, and it could be predicted by the pressure effect on the fugacity coefficient of H2S in the gas phase. The experimental data from this work are compared and shown to be consistent with earlier published data.

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Sadegh, Negar; Stenby, Erling Halfdan; Thomsen, Kaj, Thermodynamic modeling of hydrogen sulfide absorption by aqueous N-methyldiethanolamine using the Extended UNIQUAC model, Fluid Phase Equilibria, 392(2015)24–32.

ABSTRACT:

Aqueous MDEA is the most commonly used solvent for H2S removal from natural gas. A reliable thermodynamic model is required for the proper design of natural gas sweetening processes. In this study, a rigorous thermodynamic model is developed to represent properties of the H2S-MDEA-H2O ternary system. The Extended UNIQUAC model is used to represent the system behavior. The model is created based on models for the constituent binary subsystems. The developed model provides accurate representation of VLE and heat of absorption for the studied system and subsystem in the temperature range of 0-180(degrees) C, H2S partial pressure of 0.0033-8329.71 kPa, MDEA mass% of 0-50 and loading range of 0-2.17.

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Sadegh, Negar; Stenby, Erling Halfdan; Thomsen, Kaj, Thermodynamic modeling of CO2 absorption in aqueous N-Methyldiethanolamine using Extended UNIQUAC model, Fuel, 144(2015)295–306.

ABSTRACT:

A Thermodynamic model that can predict the behavior of the gas sweetening process over the applicable conditions is of vital importance in industry. In this work, Extended UNIQUAC model parameters optimized for the CO2-MDEA-H2O system are presented. Different types of experimental data consisting of pure MDEA vapor pressure, vapor-liquid equilibrium (VLE) (total pressure and CO2 partial pressure), freezing point depression (SLE), excess enthalpy, heat capacity and heat of absorption were used to adjust model parameters. The model was then used to predict the NMR spectroscopic data. The developed model accurately represents thermodynamic and thermal properties of the studied systems. The model parameters are valid in the temperature range from -15 to 200 degrees C, MDEA mass% of 5-75 and CO2 partial pressure of 0-6161.5 kPa.

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Alexeev, Artem; Shapiro, Alexander; Thomsen, Kaj, Modeling of Dissolution Effects on Waterflooding, Transport In Porous Media, 106(2015)545–562.

ABSTRACT:

Physico-chemical interactions between the fluid and reservoir rock due to the presence of active components in the injected brine produce changes within the reservoir and can significantly impact the fluid flow. We have developed a 1D numerical model for waterflooding accounting for dissolution and precipitation of the components. Extending previous studies, we consider an arbitrary chemical non-equilibrium reaction-induced dissolution. We account for different individual volumes that a component has when precipitated or dissolved. This volume non-additivity also affects the pressure and the flow rate. An equation of state is used to account for brine density variation with regard to pressure and composition. We present a numerical study of the evolution of the reservoir parameters in the framework of the developed model. It is demonstrated that the systems characterized by large Damkohler numbers (fast reaction rates) may exhibit rapid increase of porosity and permeability near the inlet probably indicating a formation of high permeable channels (wormholes). Water saturation in the zone of dissolution increases due to an increase in the bulk volume accessible for the injected fluid. Volumetric non-additivity is found to be responsible for insignificant change in the velocity of the displacement front.

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Herslund, Peter Jorgensen; Daraboina, Nagu; Thomsen, Kaj; Abildskov, Jens; von Solms, Nicolas, Measuring and modelling of the combined thermodynamic promoting effect of tetrahydrofuran and cyclopentane on carbon dioxide hydrates, Fluid Phase Equilibria, 381(2014)20–27.

ABSTRACT:

This work documents both experimental data, and by thermodynamic modelling, the synergistic effect occurring in promoted carbon dioxide hydrate systems at the simultaneous presence of tetrahydrofuran and cyclopentane. Cyclopentane has previously been considered a reference among gas hydrate promoters due to its significant pressure reducing effect in hydrate forming systems such as those related to carbon dioxide capture. The present work shows that hydrate dissociation pressures may be lowered by up to 22% compared to those of the cyclopentane promoted carbon dioxide hydrate system by addition of tetrahydrofuran to the aqueous phase. It is shown experimentally that addition of approximately 5 mol% tetrahydrofuran to the aqueous phase of the cyclopentane promoted system, reduces hydrate formation pressures by approximately 20% compared to those of the cyclopentane promoted system at similar temperatures. A thermodynamic model, based on the van der Waals-Platteeuw model and the cubic-plus-association equation of state is applied to model the mixed promoter system. The model accurately predicts the data measured in this work. Furthermore, the model explains the synergistic effect by the fact that tetrahydrofuran displaces cyclopentane from the large cavities of the sII hydrate structure. The most pronounced synergistic effect (largest pressure reduction) is predicted at scenarios, where approximately half of the cyclopentane in the hydrate phase has been substituted with tetrahydrofuran. The model predicts the maximum pressure reduction compared to the cyclopentane promoted system to be approximately 22%. This happens at tetrahydrofuran concentrations of approximately 2.8-3.1 mol% in the aqueous phase, depending on the system temperature.

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Herslund, Peter Jorgensen; Thomsen, Kaj; Abildskov, Jens; von Solms, Nicolas, Modelling of tetrahydrofuran promoted gas hydrate systems for carbon dioxide capture processes, Fluid Phase Equilibria, 375(2014)45–65.

ABSTRACT:

A thermodynamic modelling study of both fluid phase behaviour and hydrate phase behaviour is presented for the quaternary system of water, tetrahydrofuran, carbon dioxide and nitrogen. The applied model incorporates the Cubic-Plus-Association (CPA) equation of state for the fluid phase description and the van der Waals-Platteeuw hydrate model for the solid (hydrate) phase. Six binary pairs are studied for their fluid phase behaviour. CPA descriptions are adjusted when needed by correlation of binary parameters in the applied mixing- and combining rules. Kihara cell potential parameters in the hydrate model are regressed for the three hydrate formers, tetrahydrofuran, carbon dioxide and nitrogen. The developed model provides highly accurate descriptions of both fluid- and hydrate phase equilibria in the studied system and its subsystems. The developed model is applied to simulate two simplified, gas hydrate-based processes for post-combustion carbon dioxide capture from power station flue gases. The first process, an unpromoted hydrate process, operates isothermally at a temperature of 280 K. Applying three consecutive hydrate formation/dissociation stages (three-stage capture process), a carbon dioxide-rich product (97 mol%) is finally delivered at a temperature of 280 K and a pressure of 3.65 MPa. The minimum pressure requirement of the first stage is estimated to be 24.9 MPa, corresponding to the incipient hydrate dissociation pressure at 280 K for the considered flue gas. A second simulated carbon dioxide capture process uses tetrahydrofuran as a thermodynamic promoter to reduce the pressure requirements. By doing so the minimum pressure requirement of the first capture stage is lowered to 0.41 MPa. Selectivity towards carbon dioxide in the hydrate phase is however lower than in the unpromoted process. Therefore the tetrahydrofuran promoted capture process needs four consecutive hydrate formation/dissociation stages to produce a 96 mol% carbon dioxide-rich product stream. This stream. is delivered at 280 K and a pressure of 0.17 MPa. The present modelling study suggests several drawbacks of using tetrahydrofuran as a thermodynamic hydrate promoter, when applied in low-pressure, hydrate-based gas separation processes. Due to the high volatility of this compound, the promoter readily transfers to the vapour phase. Furthermore, tetrahydrofuran lowers the selectivity towards carbon dioxide, and the gas uptake in general, in the hydrate phase compared to the unpromoted system.

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Herslund, Peter Jorgensen; Thomsen, Kaj; Abildskov, Jens; von Solms, Nicolas, Modelling of cyclopentane promoted gas hydrate systems for carbon dioxide capture processes, Fluid Phase Equilibria, 375(2014)89–103.

ABSTRACT:

A thermodynamic model based on the Cubic-Plus-Association equation of state and the van der Waals-Platteeuw hydrate model is applied to perform a thermodynamic evaluation of gas hydrate forming systems relevant for post-combustion carbon dioxide capture. A modelling study of both fluid phase behaviour and hydrate phase behaviour is presented. Cycloalkanes ranging from cyclopropane to cyclohexane, represents a challenge for CPA, both in the description of the pure component densities and for liquid-liquid equilibrium (LLE) in the binary systems with water. It is concluded that an insufficient amount of reliable LLE data exist for the binary system of water and cyclopentane. Additional water-in-oil data in particular are desired for this system. An unpromoted hydrate-based capture process, operating isothermally at a temperature of 280 K is simulated. The minimum pressure requirement of the first stage is estimated to be 24.9 MPa. Applying three consecutive hydrate formation/dissociation stages (three-stage capture process), a carbon dioxide-rich product (97 mol%) may be delivered at a temperature of 280 K and a pressure of 3.65 MPa. A second capture process, where cyclopentane is incorporated as a thermodynamic hydrate promoter is simulated. At the presence of cyclopentane the minimum pressure requirement of the first stage (operating at 285 K) is lowered to 1.04 MPa. This process needs four consecutive hydrate formation/dissociation stages to produce a 95 mol% carbon dioxide-rich product stream. The vapour phases in the cyclopentane promoted process contains several mole percent cyclopentane at hydrate equilibrium conditions. At temperatures below 284K, the entire cyclopentane bulk phase evaporates completely at hydrate forming conditions (pressures below 0.55 MPa). The present study suggests the hydrate-based separation technology to be unsuitable for the specific case of post-combustion carbon dioxide capture from power station flue gases, where operating pressures should preferably remain close to atmospheric. Even though the hydrate structure becomes available at low pressure conditions (by use of thermodynamic promoters), carbon dioxide may not necessarily enter the solid phase in significant amounts.

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Ferdinand F. Hingerl, Thomas Wagner, Dmitrii A. Kulik, Kaj Thomsen, Thomas Driesner, A new aqueous activity model for geothermal brines in the system Na-K-Ca-Mg-H-Cl-SO4-H2O from 25 to 300 °C, Chemical Geology, 381(2014)78–93

ABSTRACT:

A revised formulation (named REUNIQUAC) of the Extended Universal QUAsiChemical (EUNIQUAC) activity model has been developed, which fits excess thermodynamic properties of binary and selected aqueous ternary electrolyte solutions in the systemNa-K-Ca-Mg-H-Cl-SO4-H2O over temperatures from298 to 573 K and concentrations to 5 molal (or up to saturation if solubility is below 5 molal) for saturated water vapor conditions. Compared to the original EUNIQUAC model, REUNIQUAC employs an extended version of the Debye–Hückel model using effective ionic radii of solute species, a concentration dependence of a UNIQUAC parameter, an additional empirical termfor strongly complexing salts, as well as a simple quadratic temperature dependence of the fitting parameters. REUNIQUAC considers only pairwise interactions between solute species, as opposed to the Pitzer activity model, which additionally needs to account for ternary interactions. Since REUNIQUAC uses also species-specific parameters, extension of the existing parameter set to solutions that are composed of different combinations of the fitted species, is straightforward, and involves only the parameterization of the pairwise interaction terms. All systems could be fitted with accuracy comparable to the Pitzermodel or better, although with much fewer parameters.

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Muhammad Waseem Arshad, Hallvard Fjøsne Svendsen, Philip Loldrup Fosbøl, Nicolas von Solms, and Kaj Thomsen, Equilibrium Total Pressure and CO2 Solubility in Binary and Ternary Aqueous Solutions of 2.(Diethylamino)ethanol (DEEA) and 3.(Methylamino)propylamine (MAPA), J. Chem. Eng. Data, 59(2014)764-774

ABSTRACT:

Equilibrium total pressures were measured and equilibrium CO2 partial pressures were calculated from the measured total pressure data in binary and ternary aqueous solutions of 2-(diethylamino)ethanol (DEEA) and 3-(methylamino)- propylamine (MAPA). The measurements were carried out in a commercially available calorimeter used as an equilibrium cell. The examined systems were the binary aqueous solutions of 5 M DEEA, 2 M MAPA, and 1 M MAPA and the ternary aqueous mixtures of 5 M DEEA + 2 M MAPA (5D2M) and 5 M DEEA + 1 M MAPA (5D1M), which gave liquid−liquid phase split upon CO2 absorption. The total pressures were measured and the CO2 partial pressures were calculated as a function of CO2 loading at three different temperatures 40 °C, 80 °C, and 120 °C. All experiments were reproduced with good repeatability. The measurements were carried out for 30 mass % MEA solutions to validate the experimental method. All the measured data were also compared with the results of 30 mass % MEA as a reference case. 5 M DEEA has shown high cyclic capacity. Both 2 M and 1 M MAPA showed high loading capacities at 40 °C and 120 °C. The aqueous amine mixtures, 5D2M and 5D1M, gave fairly good cyclic capacities and their results depend on the concentration of the promoter (MAPA) in the mixture. Approximate enthalpies of absorption of CO2 in all the tested aqueous amine systems were estimated from the CO2 solubility data. The measured total pressure and the estimated CO2 solubility data can be useful in thermodynamic modeling of the capture systems when aqueous DEEA−MAPA solutions are used as capture solvents

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Bjørn Maribo-Mogensen • Georgios M. Kontogeorgis • Kaj Thomsen, Modeling of dielectric properties of aqueous salt solutions with an equation of state, The journal of physical chemistry. B. — 117(2013) 10523-10533, Issue 36.

ABSTRACT:

The static permittivity is a key property for describing solutions containing polar and hydrogen bonding compounds. However, the precise relationship between the molecular and dielectric properties is not well-established. Here we show that the relative permittivity at zero frequency (static permittivity) can be modeled simultaneously with thermodynamic properties. The static permittivity is calculated
from an extension of the framework developed by Onsager, Kirkwood, and Fröhlich to associating mixtures. The thermodynamic properties are calculated from the cubic-plusassociation (CPA) equation of state that includes the Wertheim association model as formulated in the statistical associating fluid theory (SAFT) to account for hydrogen bonding molecules. We show that, by using a simple description of the geometry of the association, we may calculate the Kirkwood g-factor as a function of the probability of hydrogen bond formation. The results show that it is possible to predict the static permittivity of complex mixtures over wide temperature and pressure ranges from simple extensions of well-established theories simultaneously with the calculation of thermodynamic properties.

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Muhammad Waseem Arshad, Philip Loldrup Fosbøl, Nicolas von Solms, Hallvard Fjøsne Svendsen, and Kaj Thomsen, Heat of Absorption of COin Phase Change Solvents: 2‑(Diethylamino)ethanol and 3‑(Methylamino)propylamine, J. Chem. Eng. Data, 58(2013)1974-1988. DOI: 10.1021/je400289v

ABSTRACT:

Heat of absorption of CO2 in phase change solvents containing2-(diethylamino)ethanol (DEEA) and 3-(methylamino)propylamine (MAPA) were measured as a function of CO2 loading at different temperatures using a commercially available reaction calorimeter. The tested systems were aqueous single amines (5 M DEEA, 2 M MAPA,and 1 M MAPA) and aqueous amine mixtures (5 M DEEA + 2 M MAPA and 5 M DEEA + 1 M MAPA) which give two liquid phases on reacting with CO2. All parallel experiments have shown good repeatability. The measurements were taken isothermally at three different temperatures, (40, 80, and 120) °C. The measured differential heat of absorption values were converted into integral values by integration. Heats of absorption of CO2 in aqueous single amines were affected by changing the solvent composition (large difference in concentrations) and CO2 feed pressure simultaneously. In addition to these two parameters, it also depends on temperature and the type of amine used. Tertiary alkanolamine (DEEA) has shown greater dependency on these parameters compared to the diamine (MAPA) containing both primary and secondary amine functional groups. In aqueous amine mixtures, heats of absorption depend on CO2 loading, temperature, and composition of the constituent amines in the mixture. All measured heat of absorption data were compared with 30 mass % MEA used as a base case.

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Muhammad Waseem Arshad, Philip Loldrup Fosbøl, Nicolas von Solms, and Kaj Thomsen, Freezing Point Depressions of Phase Change CO2 Solvents, J. Chem. Eng. Data, 58(2013)1918-1926. DOI: 10.1021/je3013167

ABSTRACT:

Freezing point depressions (FPD) in phase change solvents containing 2-(diethylamino)ethanol (DEEA) and 3-(methylamino)propylamine (MAPA) were measured using a modified Beckmann apparatus. The measurements were performed for the binary aqueous DEEA and MAPA solutions, respectively, in the concentration ranges of (0 to 55) mass percent and (0 to 32.5) mass percent of amine. For the ternary aqueous DEEA–MAPA solutions, freezing points were measured for 5:1, 3:1, 1:1, 1:3, and 1:5 molar ratios of DEEA/MAPA. The FPD method was extended for easy and accurate measurement of freezing points in the CO2 loaded systems. It is based on saturation of the solution by CO2 and then dilution by using a batch of the original unloaded solution in order to get the solutions with different CO2 loadings. Freezing point measurements were then carried out for (12, 20, 30, and 33) mass percent DEEA solutions and (10, 20, and 27) mass percent MAPA solutions at different CO2 loadings. The apparatus and the experimental method used showed good repeatability and accuracy. The measured freezing point data were compared with monoethanolamine (MEA) and methyl diethanolamine (MDEA) found in the literature. The experimental values indicate that the DEEA–water interaction is almost similar to that of MEA–water interaction. MAPA has shown a stronger nonideal behavior compared to DEEA. A correlation for the freezing points as a function of solution composition was formulated for the unloaded binary and ternary systems

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Linnenberg, Sebastian; Darde, Victor; Oexmann, Jochen • Kather, Alfons; van Well, Willy J.M.; Thomsen, Kaj, Evaluating the impact of an ammonia-based post-combustion CO2 capture process on a steam power plant with different cooling water temperatures, International Journal of Greenhouse Gas Control, 10(2012)1-14

ABSTRACT:

The use of aqueous ammonia is a promising option to capture carbon dioxide from the flue gas of coal-fired power plants. Compared to a capture process using monoethanolamine (MEA), the use of ammonia can reduce the heat requirement of the CO2 desorption significantly, although an additional effort is necessary to provide the cooling of the process. To allow for a fair evaluation of the integration of this CO2 capture process into a power plant process, an overall process evaluation is carried out. The use of detailed models of the power plant, of the compressor and of the CO2 capture process enables the calculation of the power loss due to the steam extraction as well as due to the required auxiliary power for CO2 compression, solvent and cooling pumps and mechanical chillers. To study the influence of the cold end of the process, two power plants with different cooling water temperatures are analysed. Additionally, two different process configurations of the capture plant, with either one single absorber or two absorbers connected in series where the first absorber captures the majority of the CO2 and the second limits the NH3 slip, are evaluated.

The influence of the main process parameters (desorber pressure, solvent circulation rate, solvent recycling rate and chilling temperature) are evaluated and the optimal configuration with respect to the overall net efficiency penalty is determined.

The study shows that the configuration of the process with absorption at low temperature (app. 10 °C) with or without precipitation of ammonium carbonate compounds leads to a lower net efficiency penalty than an MEA-based process, assuming that low temperature cooling water is available. An estimate of the size of the absorber shows that the absorber columns of an ammonia-based process are significantly higher than the ones required for an MEA-based process.

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Victor Darde; Bjørn Maribo-Mogensen; Willy JM van Well; Erling H Stenby; Kaj Thomsen, Process simulation of CO2 capture with aqueous ammonia using the Extended UNIQUAC model, International Journal of Green House Gas Control 10(2012)74-87

Process simulation of CO capture with aqueous ammonia using the Extended UNIQUAC model, International Journal of Green House Gas Control 10(2012)74-87

ABSTRACT:

The use of aqueous ammonia is a promising option to capture carbon dioxide from power plants thanks to the potential low heat requirement during the carbon dioxide desorption compared to Monoethanolamine (MEA) based process. The patented Chilled Ammonia Process developed by Alstom absorbs carbon dioxide at low temperature (2-10°C). The low temperature limits the vaporization of ammonia in the absorber and entails precipitation of ammonium carbonate compounds, thereby allowing high loadings of CO2. The process has thereby good perspectives. However, a scientific understanding and evaluation of the process is necessary.

In this work, the performance of the carbon dioxide capture process using aqueous ammonia has been analyzed by process simulation. The Extended UNIQUAC thermodynamic model available for the CO2- NH3-H2O system has been implemented in the commercial simulator Aspen Plus® by using a newly developed user model interface (Mogensen et al., 2012). It allows for making equilibrium calculations using the advanced thermodynamic model together with the features of the commercial simulator. The present work deals with the results from the process simulation study. Two process configurations have been tested and a thorough sensitivity analysis of the main process parameters has been performed in order to analyze their effects on the heat and electricity requirement. This work confirms the high potential of the process. The heat requirement is found to be in the same range as the values reported recently for advanced amine processes. Assuming that cold cooling water is available, the electricity consumption remains limited. Hence the Chilled Ammonia Process is a promising option for post combustion carbon dioxide capture. 

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Subham Paul and Kaj Thomsen, Kinetics of Absorption of Carbon Dioxide into Aqueous Potassium Salt of Proline, International Journal of Green House Gas Control 8(2012)169-179

ABSTRACT: The absorption of carbon dioxide (CO2) into aqueous solution of potassium prolinate (KPr) are studied at 303, 313, and 323 K within the salt concentration range of 0.5 - 3.0 kmol m-3 using a wetted wall column absorber. The experimental results are used to interpret the kinetics of the reaction of CO2 with KPr for the above mentioned concentration and temperature range. Following the reaction mechanism of CO2 with primary and secondary alkanolamies, the reaction of CO2 with KPr is also described using zwitterionic mechanism. Based on the pseudo-first-order condition for the CO2 absorption, the reaction rate parameters are determined from the kinetic measurements and presented at each experimental condition. The reaction order is found to be in between 1.36 1.40 with respect to KPr for the above mentioned concentration range. The second-order rate constants, k2, are obtained as 118914, 203851, and 317625 m3 kmol−1 s−1 at 303, 313, and 323 K, respectively with activation energy of 36.5 kJ mol-1. The second-order rate constants are much higher than for alkanolamines and some other salt of amino acids.

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Jørgensen Herslund P, Thomsen K, Abildskov J, von Solms N, Phase equilibrium modeling of gas hydrate systems for CO2 capture, J. Chem. Thermodynamics, 48(2012)13–27 

ABSTRACT: Two thermodynamic models capable of describing dissociation pressures of mixed gas clathrate hydrates formed from ternary mixtures of CO2, N2 and liquid water, are presented. Both of the models utilize the Cubic-Plus-Association (CPA) equation of state (EOS) for the thermodynamic description of the non-solid phases (vapor and liquid). The solid hydrate phase is described by the van der Waals–Platteeuw model as presented by Parrish and Prausnitz. An algorithm for combining the CPA EOS with the van der Waals–Platteeuw model in a calculation of hydrate dissociation pressure is presented.
Two models are described in this work. They differ in their method for describing the Langmuir adsorption coefficients in the van der Waals–Platteeuw model. These models are named Model I and Model II. Model I utilizes a statistical thermodynamics approach based on Lennard-Jones–Devonshire theory, using the spherical core Kihara cell potential. Model II uses a two-parameter explicit expression for the Langmuir adsorption coefficient, based on Langmuir adsorption theory. With two hydrate formers, four parameters in the Kihara cell potentials are fitted for Model I. Sixteen parameters are required to be fitted for Model II. The two model parameter sets are fitted to pure hydrate dissociation pressures and mixed hydrate dissociation pressures found in literature. In the fitting process, vapor phases with initial mole fractions of CO2 below 0.15 are assumed to form structure II hydrates, while structure I hydrates are assumed to form from vapor phases with initial mole fractions of CO2 at or above 0.15.
The two models are validated against mixed hydrate equilibrium data found in literature. Both dissociation pressures and hydrate compositions are considered in the validation process.
With the fitted parameters, Model I predicts a hydrate structure transition from structure II hydrates at vapor phase mole fractions of CO2 below 0.12 to 0.16 (depending on temperature) to structure I hydrates at mole fractions of CO2 above this concentration range. The exact transition concentration is shown to increase with increasing temperature. Model II predicts structure I hydrates to be stable in concentrations down to vapor phase mole fractions of CO2 in the order of 0.001 to 0.02, depending on temperature. Model II predicts the transition concentration to decrease with increasing temperature.
Since there is disparity amongst the different literature data for this system, it was not possible to determine unequivocally, which of the two models perform better.

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Maribo-Mogensen, Bjorn; Kontogeorgis, Georgios M.; Thomsen, Kaj, Comparison of the Debye-Huckel and the Mean Spherical Approximation Theories for Electrolyte Solutions, Industrial & Engineering Chemistry Research, 51(2012)5353-5363. 


ABSTRACT: The thermodynamics of electrolyte solutions has been investigated by many scientists throughout the last century. While several theories have been presented, the most popular models for the electrostatic interactions are based on the Debye-Huckel and mean spherical approximation (MSA) theories. In this paper we investigate the differences between the Debye-Huckel and the MSA theories, and comparisons of the numerical results for the Helmholtz energy and its derivatives with respect to temperature, volume and composition are presented. The investigation shows that the nonrestricted primitive MSA theory performs similarly to Debye-Huckel, despite the differences in the derivation. We furthermore show that the static permittivity is a key parameter for both models and that in many cases it completely dominates the results obtained from the two models. Consequently, we conclude that the simpler Debye-Huckel theory may be used in connection with electrolyte equations of state without loss of accuracy.

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Darde V, Thomsen K, van Well W, Bonalumi D, Valenti G, Macchi E, Comparison of two electrolyte models for the carbon capture with aqueous ammonia, International Journal of Greenhouse Gas Control, 8(2012)61-72. 


ABSTRACT: Post-combustion carbon capture is attracting much attention due to the fact that it can be retrofitted on existing coal power plants. Among the most interesting technologies is the one that employs aqueous ammonia solutions to absorb the generated carbon dioxide. The evaluation of such process requires the modeling of electrolyte solutions. In this work two thermodynamic models for electrolyte solutions are compared against each other with respect to experimental data. They are the e-NRTL model and the Extended UNIQUAC model, both implemented in the commercial software Aspen Plus (version 7.2). Subsequently, a simple absorption/regeneration layout is simulated employing both models and the process performances are compared. In general, the Extended UNIQUAC appears to describe the experimental data for larger ranges of temperature, pressure and concentration of ammonia more satisfactorily. The energy performances computed with the Extended UNIQUAC models are less promising than with the e-NRTL model.

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Fosbøl PL, Neerup R, Arshad MW, Tecle Z, and Thomsen K, Aqueous Solubility of Piperazine and 2-Amino-2-methyl-1-propanol plus Their Mixtures Using an Improved Freezing-Point Depression Method, J. Chem. Eng. Data, 56(2011)5088-5093, DOI: 10.1021/je200959m 

 

ABSTRACT:In this work the SLE (solid-liquid equilibrium) and freezing points depression (FPD) in the electrolytic binary aqueous systems piperazine (PZ, CAS nr. 110-85-0) and aqueous 2-Amino-2-Methyl-1-Propanol (AMP, CAS nr. 124-68-5) were measured. FPD and solubility were also determined in the ternary AMP-PZ-H2O system. A method was developed by which solubility can be determined at higher temperatures using the FPD setup.
A total of 84 data points are listed in the full concentration range from 35°C to 90°C.
The solid phases piperazine hexa hydrate (PZ•6H2O), piperazine hemi hydrate (PZ•½H2O), and anhydrous PZ are precipitating during the experiments. The data can be used in the formulation, prevention or intentional formation of slurries in piperazine solvents for promoted CO2 capture.

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Victor Darde, Willy J.M. van Well, Philip L. Fosboel, Erling H. Stenby, Kaj Thomsen, Experimental measurement and modeling of the rate of absorption of carbon dioxide by aqueous ammonia, International Journal of Greenhouse Gas Control, 5(2011)1149–1162 

ABSTRACT: In this work, the rate of absorption of carbon dioxide by aqueous ammonia solvent has been studied by applying a newly built wetted wall column. The absorption rate in aqueous ammonia was measured at temperatures from 279 to 304K for 1 to 10 wt% aqueous ammonia with loadings varying from 0 to 0.8 mol CO2/mol NH3. The absorption rate in 30 wt% aqueous mono-ethanolamine (MEA) was measured at 294 and 314K with loadings varying from 0 to 0.4 as comparison.
It was found that at 304 K, the rate of absorption of carbon dioxide by 10 wt% NH3 solvent was comparable to the rates for 30 wt% MEA at 294 and 314K (a typical absorption temperature for this process). The absorption rate using ammonia was however significantly lower at temperatures of 294K and lower as applied in the Chilled Ammonia Process. However, at these low temperatures, the rate of absorption in ammonia has only a small temperature dependency.
The rate of absorption decreases strongly with decreasing ammonia concentrations and increasing CO2 loadings. The rate of absorption of carbon dioxide by aqueous ammonia solvent was modeled using the measurements of the unloaded solutions and the zwitter-ion mechanism. The model could successfully predict the experimental measurements of the absorption rate of CO2 in loaded ammonia solutions.

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Hingerl, F. F. ; Wagner, T. ; Kulik, D. ; Driesner, T. ; Kosakowski, G. ; Thomsen, K. Enhanced geothermal systems: Influence of thermodynamic data and activity models on predicted mineral precipitation-dissolution reactions, Geochimica et Cosmochimica Acta, 74(2010)A406-A406 

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Jensen L, Thomsen K, von Solms N, Inhibition of Structure I and II Gas Hydrates using Synthetic and Biological Kinetic Inhibitors, ENERGY & FUELS 25(2011)17-23 

ABSTRACT: Use of low-dosage hydrate inhibitors in oil and gas field applications has been limited mainly because there are uncertainties related to their efficiency in preventing hydrate formation or because of environmental restrictions. Another question that normally arises in connection with use of low-dosage hydrate inhibitors is how they interact with other (than water) compounds normally found in oil and gas production pipelines.
In this work three different experimental approaches to obtain hydrate induction times have been tested for structure I and II hydrate. All experiments were conducted in a high-pressure stirred cell. The results suggest that by adding small amounts of impurities to the hydrate-forming system a significant improvement in the reproducibility of induction times can be obtained. Adding salt and heptane to the system (as a simple model for seawater and a light crude) was found to increase the hydrate formation rate.
Ice-structuring protein type III identified in the ocean pout, a biological inhibitor, was added to the various hydrate-forming systems to investigate its potential as a low-dosage hydrate inhibitor. As a reference, polyvinylcaprolactam, a well-known and quite effective kinetic inhibitor was used. The icestructuring protein was found to outperform polyvinylcaprolactam for both structure I and structure II hydrate, suggesting that ice-structuring proteins hold a promising potential as environmentally friendly kinetic hydrate inhibitors.

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Fosbøl PL, Pedersen MG, and Thomsen K, Freezing Point Depressions of Aqueous MEA, MDEA, and MEA-MDEA Measured with a New Apparatus, J. Chem. Eng. Data 56(2011)995-1000 DOI: 10.1021/je100994v


 

ABSTRACT: Freezing points for aqueous monoethanolamine (MEA), methyl diethanolamine (MDEA), and MEA-MDEA solutions were measured in the concentration range from 0 to 0.4 mass fractions of the alkanolamines. For the aqueous MEA-MDEA system, freezing points for 1:4, 1:2, 1:1, 2:1, and 4:1 molar ratios of MEA/MDEA were determined. The experimental values indicate that the MDEA-water interaction is stronger than the MEA-water interaction. Measurements were carried out by a new modified Beckmann apparatus, which has not previously been described. The apparatus and method proved to have good repeatability and accuracy. A correlation of the freezing points as functions of the solution composition was made.
Measurements of aqueous MEA and aqueous MDEA were compared to experiments found in the open literature.

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D. Möhlmann and K. Thomsen, Properties of cryobrines on Mars, ICARUS, 212(2011)123–130, doi:10.1016/j.icarus.2010.11.025

ABSTRACT: Brines, i.e. aqueous salty solutions, increasingly play a role in a better understanding of physics and chemistry (and eventually also putative biology) of the upper surface of Mars. Results of physico-chemical modelling and experimentally determined data to characterize properties of cryobrines of potential interest with respect to Mars are described. Eutectic diagrams, the related numerical eutectic values of composition and temperature, the water activity of Mars-relevant brines of sulfates, chlorides, perchlorides and carbonates, including related deliquescence relative humidity, are parameters and properties, which are described here in some detail. The results characterize conditions for liquid low-temperature brines (“cryobrines”) to evolve and to exist, at least temporarily, on present Mars

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Victor Darde, Willy J.M. van Well, Erling H. Stenby, Kaj Thomsen, Modeling of carbon dioxide absorption by aqueous ammonia solutions using the Extended UNIQUAC model, Ind. Eng. Chem. Res., 49(2010), pp 12663–12674 (24), DOI:10.1021/ie1009519

 

ABSTRACT: An upgraded version of the Extended UNIQUAC thermodynamic model for the carbon dioxide-ammonia-water system has been developed, based on the original version proposed by Thomsen and Rasmussen. The original model was valid in the temperature range 0-110°C, the pressure range 0-10 MPa and the concentration range up to 80 molal ammonia. In this work, the validity of this model was extended up to 150°C and the accuracy improved by increasing the number of experimental data points from 2000 to more than 3500. These experimental data consisting of vapor-liquid equilibrium data in various concentration ranges, enthalpy change from partial evaporation measurements, speciation data, heat capacity, enthalpy of solution and enthalpy of dilution data have been used to refit 43 model parameters and standard state properties. Henry’s law constant correlations have been used for extrapolating standard state properties of carbon dioxide and ammonia to supercritical conditions.

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Victor Darde, Willy J.M. van Well, Erling H. Stenby, Kaj Thomsen, CO2 capture using aqueous ammonia: kinetic study and process simulation, Energy Procedia, 4(2010)1443–1450.

 

ABSTRACT: Carbon dioxide capture using aqueous ammonia is a post-combustion technology that has shown a good potential. Therefore this process is studied by measuring the rate of absorption of carbon dioxide by aqueous ammonia and by performing process simulation. The rate of absorption of carbon dioxide by aqueous ammonia solvent has been studied by applying a wetted wall column apparatus. The rate of absorption is crucial regarding the sizing of the absorber columns. The overall mass transfer coefficient has been measured at temperatures from 279 to 304K for 1 to 10wt% ammonia solutions at loadings up to 0.6. The results were compared with those found for 30wt% mono-ethanolamine ( MEA) solutions.
The capture process was simulated successfully using the simulator Aspen Plus coupled with the extended UNIQUAC thermodynamic model available for the NH3-CO2-H2O system. For this purpose, a user model interface was developed. The heat and electricity requirements were analyzed for a base case configuration, and a preliminary sensitivity analysis was performed on the heat and the electricity requirements and on the ammonia slip from the absorber.

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Lewis, A.E.; Nathoo, J.; Thomsen, K.; Kramer, H.J.; Witkamp, G.J.; Reddy, S.T.; Randall, D.G., Design of a Eutectic Freeze Crystallization process for multicomponent waste water stream, Chemical Engineering Research and Design, 88(2010)1290-1296(9)

ABSTRACT: Complex, hypersaline brines originating from the mining and extractive metallurgical industries have the potential to be treated using Eutectic Freeze Crystallization (EFC). Although EFC has been shown to be effective in separating a single salt and water, it has yet to be applied to the complex hypersaline brines that are typical of reverse osmosis retentates in South Africa. This paper focuses on the application of EFC for the purification of a typical brine containing high levels of sodium, chlorine, sulphate and ammonia that cannot be achieved with other separation techniques. The presence of ammonia prevents the application of membrane technology to treat the brine, leaving only cooling or evaporation as other possible options. Evaporation produces a mixed salt that requires further treatment. Modelling tools were applied to describe the phase behaviour of the complex saline systems under different process conditions and were experimentally validated. The results showed that Eutectic Freeze Crystallization could be used to selectively recover the sodium as a sodium sulphate salt. The simulation tools were especially useful in the design and optimisation of the process
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L Faramarzi; GM Kontogeorgis; ML Michelsen; K Thomsen; EH Stenby, Absorber Model for CO2 Capture by Monoethanolamine, Industrial & Engineering Chemistry Research, 49(2010)3751-3759(issue 8)

ABSTRACT: The rate-based steady-state model proposed by Gabrielsen et al. (Gabrielsen, J.; Michelsen, M. L.; Kontogeorgis, G. M.; Stenby, E. H. AIChE J. 2006, 52, 10, 3443-3451) for the design of the CO2-2-amino-2-methylpropanol absorbers is adopted and improved for the design of the CO2-monoethanolamine absorber. The influence of the application of different mass transfer correlations on the model’s performance is investigated. Analytical expressions for the calculation of the enhancement factor for the second order as well as the pseudo-first-order reaction regime are integrated in the model, and their impact on the model’s prediction is compared. The model has been successfully applied to CO2 absorber packed columns and validated against pilot plant data with good agreement.
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Yi Lin, Antoon ten Kate, Miranda Mooijer, Javier Delgado, Philip Loldrup Fosbøl, Kaj Thomsen, Comparison of activity coefficient models for electrolyte systems, AIChE Journal, 56(2010)1334-1351(issue 5)

ABSTRACT: Three activity coefficient models for electrolyte solutions were evaluated and compared. The activity coefficient models are: The electrolyte NRTL model (ElecNRTL) by Aspentech, the mixed solvent electrolyte model (MSE) by OLI Systems, and the Extended UNIQUAC model from the Technical University of Denmark (DTU). Test systems containing a single salt (NaCl), multiple salts, and mixed solvent aqueous electrolyte solutions were chosen. The performance of the activity coefficient models were compared regarding the accuracy of solid–liquid and vapor–liquid equilibrium calculations for the test systems
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A. Fettouhi, K. Thomsen, Solid–liquid equilibria for binary and ternary systems with the Cubic-Plus-Association (CPA) equation of state, Fluid Phase Equilibria 293(2010)121-129, DOI:10.1016/j.fluid.2010.02.017

ABSTRACT: A systematic investigation of the CPA model’s performance within solid–liquid equilibria (SLE) in binary mixtures (methane + ethane, methane + heptane, methane + benzene, methane + CO2, ethane + heptane, ethane + CO2, 1-propanol + 1,4-dioxane, ethanol + water, 2-propanol + water) is presented. The results from the binary mixtures are used to predict SLE behaviour in ternary mixtures (methane + ethane + heptane, methane + ethane + CO2). Our results are compared with experimental data found in the literature.
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Lars Jensen; Hans Ramløv; Kaj Thomsen; Nicolas von Solms, Inhibition of Methane Hydrate Formation by Ice-Structuring Proteins, Industrial & Engineering Chemistry Research 49(2010)1486-1492(issue 4)

ABSTRACT: In the oil and gas industry there is ample motivation for moving toward greener kinetic inhibitors of gas hydrates as many of those used today suffer from poor biodegradability. In this work, we have investigated experimentally whether ice-structuring proteins (ISPs) found in fish and insect, assumed biodegradable, are capable of inhibiting the growth of methane hydrate (a structure I hydrate). The ISPs investigated were type III HPLC12 (originally identified in ocean pout) and ISP type III found in meal worm (Tenebrio molitor). These were compared to polyvinylpyrrolidone (PVP) a well-known kinetic hydrate inhibitor. The results revealed that adding ISP in sufficient amounts caused the appearance of an initial nonlinear growth period. At a certain point during the growth process the growth pattern changed to linear which is identical to the growth observed for methane hydrate in the absence of inhibitors. The profile of the nonlinear growth was concentration-dependent but also dependent on the stirring rate. ISP type III HPLC12 decreased the growth rate of methane hydrate during the linear growth period by 17-75% at concentrations of 0.01-0.1 wt % (0.014-0.14 mM) while ISP from Tenebrio molitor and PVP decreased the growth rate by 30% and 39% at concentrations of 0.004 wt % (0.005 mM) and 0.1 wt % (0.1 mM), respectively. Considering the low concentration of Tenebrio molitor ISP used, these results indicate that ISP from Tenebrio molitor is the most effective hydrate inhibitor among those investigated. Thermal hysteresis ice formation experiments revealed that ISP from Tenebrio molitor causes higher thermal hysteresis for ice formation compared to type III ISP identified in ocean pout while PVP did not cause thermal hysteresis. This indicates that there might be a direct relationship between ISP performance for ice and hydrate inhibition, and that thermal hysteresis experiments can be used to screen ISPs as kinetic inhibitors.
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Awan, Javeed A.; Thomsen, Kaj; Coquelet, Christophe; Fosbol, Philip L.; Richon, Dominique, Vapor-Liquid Equilibrium Measurements and Modeling of the Propyl Mercaptan plus Methane plus Water System, Journal Of Chemical And Engineering Data, 55(2010)842-846(issue 2)

ABSTRACT: In this work, vapor-liquid equilibrium (VLE) measurements of propyl mercaptan (PM) in pure water were performed at three different temperatures, (303, 323, and 365) K, with a pressure variation from (1 to 8) MPa. The total system pressure was maintained by CH(4). The inlet mole fraction of propyl mercaptan in all experiments was the same, around 4.5 center dot 10(-4) in the liquid phase. The objective was to provide experimental VLE data points of the propyl mercaptan + methane + water system for modeling since there is a lack of available data. These data will allow the industrial modeling of sulfur emission. The thermodynamic model used for the description of VLE is the extended UNIQUAC model. The model parameters are valid in the temperature range similar to the measured data and a pressure range up to 8 MPa.
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Jensen L, Thomsen K, von Solms N, Wierzchowski S, Walsh MR, Koh CA, Sloan ED, Wu DT, Sum AK, Calculation of Liquid Water-Hydrate-Methane Vapor Phase Equilibria from Molecular Simulations, JOURNAL OF PHYSICAL CHEMISTRY B, 114(2010)5775-5782

ABSTRACT: Monte Carlo simulation methods for determining fluid- and crystal-phase chemical potentials are used for the first time to calculate liquid water−methane hydrate−methane vapor phase equilibria from knowledge of atomistic interaction potentials alone. The water and methane molecules are modeled using the TIP4P/ice potential and a united-atom Lennard-Jones potential, respectively. The equilibrium calculation method for this system has three components, (i) thermodynamic integration from a supercritical ideal gas to obtain the fluid-phase chemical potentials, (ii) calculation of the chemical potential of the zero-occupancy hydrate system using thermodynamic integration from an Einstein crystal reference state, and (iii) thermodynamic integration to obtain the water and guest molecules’ chemical potentials as a function of the hydrate occupancy. The three-phase equilibrium curve is calculated for pressures ranging from 20 to 500 bar and is shown to follow the Clapeyron behavior, in agreement with experiment; coexistence temperatures differ from the latter by 4−16 K in the pressure range studied. The enthalpy of dissociation extracted from the calculated P−T curve is within 2% of the experimental value at corresponding conditions. While computationally intensive, simulations such as these are essential to map the thermodynamically stable conditions for hydrate systems.
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T. Boch Andersen; K. Thomsen, Separation of water through gas hydrate formation, International Sugar Journal, 111(2009)632-636(issue 1330)

ABSTRACT: Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goal of the project was to formulate an alternative separation concept, which can replace the traditional water evaporation process in the sugar production. Work with the separation concept showed that gas hydrates can be used for water separation. The process is not suitable for sugar production because of large volumes and the needs for high pressure. The process could be interesting for concentration of heat sensitive, high value products.
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Victor Darde, Kaj Thomsen, Willy J.M. van Well, Erling H. Stenby, Chilled ammonia process for CO2 capture International Journal of Greenhouse Gas Control, 4(2010)131–136

ABSTRACT: The chilled ammonia process absorbs the CO2 at low temperature (2–10°C). The heat of absorption of carbon dioxide by ammonia is significantly lower than for amines. In addition, degradation problems can be avoided and a high carbon dioxide capacity is achieved. Hence, this process shows good perspectives for decreasing the heat requirement. However, a scientific understanding of the processes is required. The thermodynamic properties of the NH3–CO2–H2O system were described using the extended UNIQUAC electrolyte model developed by Thomsen and Rasmussen in a temperature range from 0 to 110 °C and pressure up to 100 bars. The results show that solid phases consisting of ammonium carbonate and bicarbonate are formed in the absorber. The heat requirements in the absorber and in the desorber have been studied. The enthalpy calculations show that a heat requirement for the desorber lower than 2 GJ/ton CO2 can be reached.
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Victor Darde; Kaj Thomsen; Willy J.M. van Well; Erling H. Stenby, Chilled ammonia process for CO2 capture, Energy Procedia, 1(2009)1035-1042(issue 1)

ABSTRACT: The chilled ammonia process absorbs the CO2 at low temperature (2-10°C). The heat of absorption of carbon dioxide by ammonia is significantly lower than for amines. In addition, degradation problems can be avoided and a high carbon dioxide capacity is achieved. Hence, this process shows good perspectives for decreasing the energy requirement. However, a scientific understanding of the processes is required. The properties of the NH3-CO2-H2O system were described using the Extended UNIQUAC electrolyte model developed by Thomsen and Rasmussen in a temperature range from 0 to 110°C and pressure up to 100 bars [1]. The results show that solid phases consisting of ammonium carbonate and bicarbonate are formed in the absorber. The energy requirements in the absorber and in the desorber have been studied. The enthalpy calculations show that an energy requirement for the desorber lower than 2 GJ/ton CO2 can be reached
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Leila Faramarzi; Georgios M. Kontogeorgis; Kaj Thomsen; Erling H. Stenby, Thermodynamic modeling of the solubility of CO2 in aqueous alkanolamine solutions using the extended UNIQUAC model application to monoethanolamine and methyldiethanolamine, Energy Procedia, 1(2009)861-867(issue 1)


ABSTRACT: The extended UNIQUAC model as proposed by Thomsen and Rasmussen [K. Thomsen, P. Rasmussen, Chem. Eng. Sci. 54 (1999) 1787-1802] was applied to the thermodynamic representation of carbon dioxide absorption in aqueous monoethanolamine (MEA) and methyldiethanolamine (MDEA) solutions. All the essential parameters of the model are simultaneously regressed to a set of data on the MEA and MDEA systems. Freezing point depression, vapor liquid equilibrium (VLE) and excess enthalpy (HE) data of the binary systems of MEA-water and MDEA-water, VLE data on the ternary CO2-MEA-water as well as CO2-MDEA-water systems in a wide range of temperature (-20-200°C) were used. The application of the model to a large number of experimental data for representation of total pressure over the absorbent solutions (25-200°C), correlation of the excess enthalpy and freezing point depression of the binary solutions of alkanolamine and water and also calculation of pure alkanolamine vapor pressure has been performed with good precision.
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Leila Faramarzi, Georgios M. Kontogeorgis, Kaj Thomsen, Erling H. Stenby, Extended UNIQUAC model for thermodynamic modeling of CO2 absorption in aqueous alkanolamine solutions, Fluid Phase Equilibria, 282(2009)121–132

ABSTRACT: The extended UNIQUAC model [Thomsen, Rasmussen, Chem. Eng. Sci. 54 (1999) 1787-1802] was applied to the thermodynamic representation of carbon dioxide absorption in aqueous monoethanolamine (MEA), methyldiethanolamine (MDEA) and varied strength mixtures of the two alkanolamines (MEA-MDEA). For these systems, altogether 13 interaction model parameters are adjusted. Out of these parameters, 11 are temperature dependent. All the essential parameters of the model are simultaneously regressed to a collective set of data on the single MEA and MDEA systems. Different types of data are used for modeling and they cover a very wide range of conditions. Vapor-liquid equilibrium (VLE) data for the aqueous alkanolamine systems containing CO2 in the pressure range of 3-13000 kPa and temperatures of 25-200°C are used. The model is also regressed with the VLE and freezing point depression data of the binary aqueous alkanolamine systems (MEA-water and MDEA-water). The two just mentioned types of data cover the full concentration range of alkanolamines from extremely dilute to almost pure. The experimental freezing point depression data down to the temperature of -20°C are used. Experimental excess enthalpy (HE) data of the binary MEA-water and MDEA-water systems at 25, 40, 65 and 69°C are used as well. In order to enhance the calculation of the infinite dilution activity coefficients of MEA and MDEA, the pure alkanolamines vapor pressure data in a relevant temperature range (up to almost 230°C) are included in the parameter estimation process. The previously unavailable standard state properties of the alkanolamine ions appearing in this work i.e. MEA protonate, MEA carbamate and MDEA protonate are determined. The concentration of the species in both MEA and MDEA solutions containing CO2 are predicted by the model and in the case of MEA compared to NMR spectroscopic data. Using only one set of parameters for correlation of different thermodynamic properties, the model has represented the experimental data with good precision.
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Philip L. Fosbøl; Kaj Thomsen; Erling H. Stenby, Modeling of the Mixed Solvent Electrolyte System CO2-Na2CO3-NaHCO3-Monoethylene Glycol-Water, Industrial & Engineering Chemistry Research, 48(2009)4565-4578

ABSTRACT: The Extended UNIQUAC electrolyte activity coefficient model has been correlated to 751 experimental solid-liquid equilibrium (SLE), vapor-liquid equilibrium (VLE), and excess enthalpy data for the mixed solvent CO2-NaHCO3-Na2CO3-Mono ethylene glycol(MEG)-H2O electrolyte system. The model was validated by predicting the excess heat capacity. The model is consistent and one set of binary interaction parameters are used for calculating all the properties between 50 and 90 °C. The model is compared to experimental data of infinite dilution activity coefficient measurements of MEG and may be used for calculating activities, solubility, salt hydrate properties, pH, and CO2 solubility in the NaHCO3-Na2CO3-MEG-H2O system. A simple density model of NaHCO3-Na2CO3-NaCl-MEG-water is given.
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Philip Loldrup Fosbøl, Kaj Thomsen; Erling Halfdan Stenby, Solubility Measurements in the Mixed Solvent Electrolyte System Na2CO3-NaHCO3-Monoethylene Glycol-Water, Industrial & Engineering Chemistry Research, vol: 48(4), p. 2218-2228 (2009).

ABSTRACT: 212 new data points for solubility and density have been measured in the mixed solvent electrolytic CO2-NaHCO3-Na2CO3-Mono ethylene glycol (MEG)-water system. Measurements were conducted at 2 to 60 °C at atmospheric pressure. An overview of methods available for determining the carbon dioxide and sodium content is given and the reverse Schreinemakers method was chosen. The method gives the amounts of all the species in the liquid. The solutions have a tendency to form meta-stable mixtures from which sodium carbonate salt hydrates may precipitate. 30 meta-stable data points are reported.
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Philip L. Fosbøl, Kaj Thomsen, and Erling H. Stenby, Reverse Schreinemakers method for experimental analysis of mixed-solvent electrolyte systems, J. Solution Chem. 38(2009)1–14.

ABSTRACT: A method based on Schreinemakers tie-line theory of 1893 is derived for determining the composition and phase amounts in solubility experiment for multi-solvent electrolyte systems. The method uses the lever rule in reverse compared to Schreinemakers wet residue method and is therefore called the reverse Schreinemakers(RS) method. The method is based on simple mass balance principles similar to the wet residues method. It allows for accurate determination of mixed-solvent phase composition even though solvent may precipitate as complexes of solvent and salt. Discrepancy between determining composition of salt mixtures by pH titration is discussed and the derived method significantly improves the obtained result from titration. Furthermore the method reduces the required experimental work for analysis of phase composition. The method is applicable to multi-solvent systems and may be used for determination of solid composition, similar to Schreinemakers original rest method. An example calculation in the Na2CO3-NaHCO3-MEG-H2O system is presented.
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Lars Jensen, Kaj Thomsen, and Nicolas von Solms, Propane Hydrate Nucleation: Experimental Investigation and Correlation (Chemical Engineering Science 63(2008)3069-3080)

ABSTRACT: In this work the nucleation kinetics of propane gas hydrate has been investigated experimentally using a stirred batch reactor. The experiments have been performed isothermally recording the pressure as a function of time. Experiments were conducted at different stirring rates, but in the same supersaturation region. The experiments showed that the gas dissolution rate rather than the induction time of propane hydrate is influenced by a change in agitation. This was especially valid at high stirring rates when the water surface was severely disturbed. Addition of polyvinylpyrrolidone to the aqueous phase was found to reduce the gas dissolution rate slightly. However the induction times were prolonged quite substantially upon addition of polyvinylpyrrolidone. The induction time data were correlated using a newly developed induction time model based on crystallization theory also capable of taking into account the presence of additives. In most cases reasonable agreement between the data and the model could be obtained. The results revealed that especially the effective surface energy between propane hydrate and water is likely to change when the stirring rate varies from very high to low. The prolongation of induction times according to the model is likely to be due to a change in the nuclei-substrate contact angle.
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Philip L. Fosbøl, Kaj Thomsen, and Erling H. Stenby, A Review and Recommended Thermodynamic Properties of FeCO3, (Corrosion Engineering Science and Technology, 45(2010)115-135)

ABSTRACT: An extensive review of entropy, enthalpy of formation and Gibbs energy of formation, heat capacity, aqueous solubility and solubility constant of FeCO3 is given. A consistent set of thermodynamic properties for FeCO3 and relevant aqeous species is selected and recommended for use. Speciation schemes for aqeous FeCO3 are reviewed and evaluated. Issues related to supersaturation of FeCO3 are discussed. Works on the thermal decomposition of FeCO3 are presented and an overview of measured solubility and synthesis of FeCO3 is given.
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Zheng Guo, Bena-Marie Lue, Kaj Thomsen, Anne Boye Strunge Meyer, and Xuebing Xu, Predictions of Flavonoid Solubility in Ionic Liquids by COSMO-RS: Experimental Verification, Structural Elucidation, and Solvation Characterization, (Green Chemistry, 9(2007)1362-1373))

ABSTRACT: Predictions of the solubility of flavonoids in a large variety of ionic liquids (ILs) with over 1800 available structures were examined based on COSMO-RS computation. The results shows that the solubilities of flavonoids are strongly anion-dependent; and the ILs could be classified into 3 groups according to the values of esculin solubility. The predictions were experimentally verified by the measurement of the solubilities of esculin and rutin in 12 ILs with varying anion and cation parts. It is shown that predicted and experimental results generally have a good agreement, indicating the correctness of the physics of COSMO-RS as an experimentally independent approach, and the application potential to preselect favourable structures from a large pool of available ILs. Importantly, this work first systemically demonstrated that COSMO-RS derived parameters, electrostatic misfit, H-bonding, and van der Waals interaction energy, are capable of and effectively characterize the complicated multiple interactions in IL system. Force field analysis shows that H-bonding interaction is the most dominant interaction for ILs (followed by electrostatic misfit and van der Waals interactions) to determine the solubility of flavonoids, and anionic part has greater effect on the overall H-bonding capability of the IL. Based on solvation interaction energy with flavonoids and hydrogen bond basicity derived from COSMO-RS, ILs were scaled and categorized qualitatively and quantitatively, which may be of general value to better understand the solvation behaviors of ILs. Conversely, the improved understanding and knowledge of the correct association of specific interactions with defined groups of ILs may help to mix and match these moieties into an optimal structure for a particular application. Therefore, the data obtained in this study may be important for the tailoring of the desired structures of ILs used as the media for efficient enzymatic esterification of flavonoids.
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Yi Lin, Kaj Thomsen and Jean-Charles de Hemptinne, Multi Component Equations of State for Electrolytes”, (AIChE Journal, 53(4)(2007)989-1005)

ABSTRACT: Four equations of state have been implemented and evaluated for multi-component electrolyte solutions at different temperatures and pressures. The equations contain terms accounting for short-range and long-range interactions in electrolyte solutions. Short range interactions are described by one of the three equations of state, Peng-Robinson, Soave-Redlich-Kwong, or Cubic-Plus-Association (CPA). Long range interactions are described by either the simplified mean spherical approximation (MSA) solution of the Ornstein–Zernicke equation or the simplified Debye-Hückel term. An optional Born term is added to these electrostatic terms. The resulting electrolyte equations of state were tested by determining the optimal model parameters for the multi-component test system consisting of H2O, Na+, H+, Ca2+, Cl-, OH-, SO42-. In order to describe the thermodynamics of this multi-component system, ion specific parameters were determined. The parameters in the equations of state were fitted to experimental data consisting of apparent molar volumes, osmotic coefficients, mean ionic activity coefficients, and solid-liquid equilibrium data. The results of the parameter fitting are presented. The ability of the equations of state to reproduce the experimental data is demonstrated. The performance of the equations of state for multi-component systems is compared and analyzed in view of the various short range and long range terms employed.
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Kaj Thomsen, Jørgen Peter Jensen, Peter Simonsen, Bo Sander, Reuse of Alkali from Fly Ash from Biomass Combustion, Report written in Danish language on research project sponsored by PSO (Danish Power Plants).

ABSTRACT: Experiments to leach potassium salts from fly ash from straw combustion were performed. The fly ash was produced in the bio mass boiler at the Avedøre power plant in south western Copenhagen, Denmark. The fly ash contained approximately 90 mass percent water soluble material. When the fly ash was dissolved at low pH, a slightly higher solubility was found. 100 gram fly ash consisted typically of 9 gram insoluble material, 9 gram calcium phosphate, 29 gram potassium sulfate and 53 gram of potassium chloride. In addition, 100 gram of fly ash contained approximately 1 mg of cadmium, corresponding to a concentration of cadmium of 10 ppm in the fly ash. Fly ash from the bio mass boiler at the Avedøre power plant apparently has a significantly larger content of potassium salts than fly ash from other boilers.
The Extended UNIQUAC thermodynamic model was used for calculating relevant phase diagrams and calculations of the necessary amount of water required for dissolving all the KCl and all KCl + K2SO4 of the fly ash. This theoretical minimum amount of water was calculated at a range of temperatures between 10 and 100°C. The amount of water required at 100°C was less than half of that required at 10°C. Experiments were performed in order to find a feasible method for separating the potassium salts of the fly ash from the ash residue and especially from the soluble cadmium salts found in the fly ash.
Experiments with counter current leaching of fly ash in a fluid bed gave unsatisfactory results. Apparently there was a lack of contact between the wash water and the ash. In addition, sedimentation was very slow resulting in an incomplete separation of wash water and ash residue. Experiments with ion exchange by adding CaCl2 to the wash water and successive precipitation of gypsum or anhydrite gave unsatisfactory results. Process simulation had shown that by this method the necessary amount of washing water could be decreased. This is due to the higher solubility of potassium chloride compared to potassium sulfate. By using this reduced amount of washing water with CaCl2 a viscous, muddy slurry was obtained. It was not possible to separate this slurry into a liquid phase and a solid phase.
It was found that a good separation was obtained by intense stirring followed by centrifuging or by filtering the slurry in a filter press. The lab experiments were performed as a counter current leaching process in four stages. Depending on the applied amount of water relative to the theoretical minimum amount of water a complete separation could be obtained in two or more stages. More stages are required if less water is used. If the leaching is performed in less stages, a larger amount of water is required.
If the washing process was performed at pH 1, the phosphate fraction could successively be obtained as a fine, white powder of almost pure calcium phosphate by regulating pH to 12. If the washing process was conducted at a pH between 1 and 5 and pH was successively adjusted to 12, cadmium could not be detected in the brine by current analysis methods. All cadmium was precipitated as phosphate.
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Kaj Thomsen, Duc Thoung Vu, Mette Stenby, Jørgen Peter Jensen, Peter Simonsen and Bo Sander, Leaching of Nutrient Salts from Fly Ash from Biomass Combustion, (Proceedings from 14th European Conference and Technology Exhibition on Biomass for Energy, Industry and Climate Protection, October 2005, p. 1273-1276)

ABSTRACT: Methods to selectively leach nutrient salts from fly ash, while leaving cadmium un-dissolved were studied. Temperature, pH, water to fly ash ratio are all expected to influence the kinetics and the equilibrium boundaries for this process. Three different leaching methods were investigated. The first method was a counter current moving bed process in four stages. The ash was kept in filter bags and leached with water that was introduced into the bags at 40-50°C. In the second method, fly ash and water was brought into contact in a partially fluidized bed. The third method was a counter current moving bed process with agitation/centrifugation. It was found that a satisfactory leaching of the nutrient salts could be achieved with the third method using only two or three stages, depending on the water to fly ash ratio. It is an advantage to perform the process at temperatures above 50°C as the amount of water used for leaching at this temperature can be reduced compared to the amount of water needed at 25°C.
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Ada Villafáfila García, Kaj Thomsen, and Erling H. Stenby, Prediction of Mineral Scale Formation in Geothermal and Oilfield operations using the Extended UNIQUAC Model. Part II: Carbonate Scaling Minerals, (Geothermics 35(2006)239-284)

ABSTRACT: Two additional parameters to account for the pressure dependency of solubility are added to the Extended UNIQUAC model presented by Thomsen and Rasmussen (1999). The improved model has been used for correlation and prediction of vapor-liquid-solid equilibrium for different carbonate systems (CaCO3, MgCO3, BaCO3 and SrCO3) causing scale problems. The solubility of NaCl and CO2 in pure water, and the solubility of CO2 in solutions of different salts (NaCl and Na2SO4) have also been correlated. The temperature and pressure range covered is from 0 to 250°C and from 1 to 1000 bar, respectively. The results show that the Extended UNIQUAC model, with the proposed pressure parameters, is able to represent binary (NaCl-H2O, MCO3-H2O and CO2-H2O), ternary (MCO3-CO2-H2O, CO2-NaCl-H2O and CO2-Na2SO4-H2O) and quaternary (CO2-NaCl-Na2SO4-H2O) solubility data within the experimental accuracy in the temperature range from 0 to 250°C, and the pressure range from 1 to 1000 bar. M stands for Ca2+, Mg2+, Ba2+ and Sr2+
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Søren Gregers Christensen and Kaj Thomsen, Representation of volumetric data of electrolyte solutions at varying concentrations and temperatures, (Internal report)

ABSTRACT: A modification of the Masson equation combined with Young’s rule based on ion specific parameters has been applied to volumetric data for mixtures of (H+, Na+, K+, NH4+, Ca++, Mg++) (Cl-,NO3-,SO4--). The parameters have been regressed from data in the temperature range 0 – 100°C and concentration range 0 – 11.8 mol/kg but are shown to be valid up to saturation. The model only requires 5 parameters per ion in the entire range of concentration and temperature. The model is easily applied to multi component mixtures, and it is shown that the relative errors of the predicted results in both ternary and quaternary systems are well within the experimental accuracy of the data.
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Kaj Thomsen, Modeling Electrolyte Solutions with the extended universal quasichemical (UNIQUAC) Model, (Presented at the 11th ISSP in Aveiro, Portugal, 2004) (Journal of Pure and Applied Chemistry, 77(2005)531-542, issue 3 )

ABSTRACT: The extended universal quasichemical (UNIQUAC) model is a thermodynamic model for solutions containing electrolytes and non-electrolytes. The model is a gibbs excess function consisting of a Debye-Hückel term and a standard UNIQUAC term. The model only requires binary, ion specific interaction parameters. A unique choice of standard states makes the model able to reproduce solid-liquid, vapor-liquid, and liquid-liquid phase equilibria as well as thermal properties of electrolyte solutions using one set of parameters.
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Søren Gregers Christensen and Kaj Thomsen, Experimental measurement and modeling of the distribution of solvent and ions between an aqueous phase and an ion exchange resin, (Fluid Phase Equilibria, 228-229(2005)247-260).

ABSTRACT: The distribution of solutes and solvent between an aqueous solution of salt and an ion exchange resin has been measured at ambient temperature. The experiments have been performed for aqueous solutions of KNO3, KCl, Ca(NO3)2 and CaCl2 in the concentration range of 0-3N. The absorption has been measured for 3 gel type and 3 macroreticular resins with a degree of crosslinking varying from 10.5 to 18.5%. The experimental results have been modeled with the Extended UNIQUAC model combined with an elastic term taking the elastic properties of the resin structure into account. The model shows very good predictions with varying degree of crosslinking, and the deviations between model results and experimental data are all within the experimental error.
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Ada Villafáfila García, Kaj Thomsen, Prediction of Mineral Scale Formation in Geothermal and Oilfield Operations using the Extended UNIQUAC Model. Part I: Sulphate Scaling Minerals, and Erling H. Stenby (Geothermics, 34(2005)61-97)

ABSTRACT: Pressure parameters are added to the Extended UNIQUAC model presented by Thomsen and Rasmussen (1999). The improved model has been used for correlation and prediction of solid-liquid equilibrium (SLE) of scaling minerals (CaSO4, CaSO4·2H2O, BaSO4 and SrSO4) at temperatures up to 300°C and pressures up to 1000 bar. The results show that the Extended UNIQUAC model, with the proposed pressure parameters is able to represent binary, ternary and quaternary solubility data within the experimental accuracy in the temperature range from -20 to 300°C, and the pressure range from 1 to 1000 bar.
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Kaj Thomsen, Maria Iliuta, and Peter Rasmussen, Extended UNIQUAC model for correlation and prediction of vapor-liquid-liquid-solid equilibria in aqueous salt systems containing non-electrolytes. Part B. Alcohol (Ethanol, Propanols, Butanols) - water - salt systems. (Chemical Engineering Science 59(2004)3631-3647, issue 17)

ABSTRACT: The Extended UNIQUAC model is an electrolyte model formed by combining the original UNIQUAC model, the Debye-Hückel law, and the Soave-Redlich-Kwong equation of state. The model only requires binary, temperature dependent interaction parameters. It has previously been used to describe the excess Gibbs energy for aqueous electrolyte mixtures and aqueous electrolyte systems containing methanol. It has been found to be an adequate model for representing solid-liquid-vapor equilibrium and thermal property data for strongly non-ideal systems. In this work the model is extended to aqueous salt systems containing higher alcohols. The calculations are based on an extensive database consisting of salt solubility data, vapor liquid equilibrium data, and liquid-liquid equilibrium data for solvent mixtures and for mixed solvent-electrolyte systems.
The application of this model to represent the vapor-liquid-liquid-solid equilibria in aqueous systems containing various non-electrolytes (ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl 1-propanol, 2-methyl 2-propanol) and various ions (Na+, K+, NH4+, Cl-, NO3-, SO42-, SO32-, HSO3-, CO32-,and HCO3-) shows the capability of the model to accurately represent the phase behavior of these kinds of systems.
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Søren Gregers Christensen and Kaj Thomsen, Modeling of Vapor-Liquid-Solid Equilibria in Acidic Aqueous Solutions (Ind. & Eng. Chem. Res. 42(2003)4260-4268, issue 18)

ABSTRACT: The phase behavior (vapor - liquid equilibria (VLE) and solid – liquid equilibria (SLE)) and thermal properties of aqueous solutions of ions like (K+, Na+, NH4+, Ca2+, Cl-) in the presence of phosphoric acid (H3PO4, H2PO4-, HPO42- ) and nitric acid (HNO3, NO3-) are described by means of the Extended UNIQUAC model. Model parameters are evaluated on the basis of more than 2000 experimental data points. There is good agreement between calculated and experimental data points. The model parameters are valid in the temperature range from -18 - +122°C and in the concentration range up to 12 molal for the acids HNO3 and H3PO4.
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Søren Gregers Christensen and Kaj Thomsen, Production of fertilizer salts (Dansk Kemi, 83(2) (2002)18-19)

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Maria C. Iliuta, Kaj Thomsen and Peter Rasmussen, Modeling of heavy metal salt solubility using the Extended UNIQUAC model (AIChE Journal, 48(11)(2002)2664-2689)

ABSTRACT: Solid-liquid equilibria in complex systems involving a heavy metal cation (Mn2+, Fe2+, Co2+, Ni2+, Cu2+, or Zn2+) and one or more ions for which Extended UNIQUAC parameters have been published previously are modeled using the Extended UNIQUAC model. Model parameters are determined on the basis of a data bank with more than 4000 experimental data points for binary and ternary systems. The parameters are generally valid in the temperature range from the cryohydratic point to the boiling point of the respective solutions.
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Raphaël Huyghe, Peter Rasmussen, and Kaj Thomsen, Solid-Liquid Equilibria for the Binary Mixtures 1,4-Xylene + Ethylbenzene and 1,4-Xylene + Toluene. (Chemical Engineering Communications 191(8)(2004)1017-1023)

ABSTRACT: Solid-liquid equilibrium (SLE) data for the binary mixtures 1,4-xylene + ethylbenzene, and 1,4-xylene + toluene have been measured using differential scanning calorimetry (DSC) in the temperature range from 133.15 K to 293.15 K.
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Morten Mejlholm, Kaj Thomsen, Peter Rasmussen, Jørgen Vergod, Freddy Knudsen, Hugo Høyer, "SODIUM CHLORIDE DIHYDRATE - A POTENTIAL CAUSE OF SLIPPERY ACCIDENTS" (Presented at the XIth PIARC International Winter Road Congress, Sapporo, Japan, January 28-31, 2002. Proceedings of the XIth PIARC International Winter Road Congress, Sapporo, Japan (2002))

ABSTRACT: From a thermodynamic point of view, it can be expected that sodium chloride dihydrate (hydrohalite, NaCl·2H2O) will form on winter roads under certain conditions at temperatures below 0.1°C. In order to elucidate whether or not the formation of hydrohalite on the pavement can explain the phenomenon of ice appearing to be resistant to road salt, a comparative study has been made on a number of different surfaces measuring the friction index. The friction measurements were performed with a Portable Skid-Resistance Tester. Discontinuous surfaces consisting of small islands of hydrohalite was classified as potentially slippery surfaces. It is therefore possible that the formation of hydrohalite contributes to accidents on slippery roads.
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Selva Pereda, Kaj Thomsen and Peter Rasmussen, Vapor-Liquid-Solid Equilibria of Sulfur Dioxide in Aqueous Electrolyte Solutions Chemical Engineering Science 55(2000)2663-2671.

ABSTRACT: The Extended UNIQUAC model for electrolyte systems, combined with the Soave-Redlich-Kwong equation of state is used to describe the complex vapor-liquid-solid equilibria of sulfur dioxide in electrolyte solutions. Model parameters based on 1500 experimental data points are presented. The parameters are applicable in the temperature range 0 to 110 °C, concentrations up to saturation and pressures up to 30 bar. This validity range corresponds to the experimental data used for the evaluation of parameters.
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Maria Iliuta, Kaj Thomsen and Peter Rasmussen, Extended UNIQUAC model for correlation and prediction of vapour-liquid-solid equilibria in aqueous salt systems containing non-electrolytes . Part A. Methanol - water - salt systems, Chemical Engineering Science, 55(2000)2673-2686

ABSTRACT: The Extended UNIQUAC model has previously been used to describe the excess Gibbs energy for aqueous electrolyte mixtures. It is an electrolyte model formed by combining the original UNIQUAC model, the Debye-Hückel law and the Soave-Redlich-Kwong equation of state. In this work the model is extended to aqueous salt systems containing non-electrolytes in order to demonstrate its ability in representing solid-liquid-vapour (SLV) equilibrium and thermal property data for these strongly non-ideal systems. The model requires only pure component and binary temperature dependent interaction parameters. The calculations are based on an extensive database consisting of salt solubility data in pure and mixed solvents, VLE data for solvent mixtures and mixed solvent - electrolyte systems and thermal properties for mixed solvent solutions. Application of the model to the methanol - water system in the presence of several ions (Na+, K+, NH4+, Cl-, NO3-, SO42-, CO32-, and HCO3-) shows that the Extended UNIQUAC model is able to give an accurate description of VLE and SLE in ternary and quaternary mixtures, using the same set of binary interaction parameters. The capability of the model to predict accurately the phase behaviour of methanol - water - three salts systems is illustrated.
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K. Thomsen and P. Rasmussen, Thermodynamic Model for the Ammonia-Water System" ("Steam Water and Hydrothermal Systems: Physics and Chemistry Meeting the Needs of Industry, Proceedings of the 13th International Conference on the Properties of Water and Steam, Editors: P.G. Hill, P. Tremaine, D. Irish, and P.V. Balakrishnan, NRC Press, Ottawa, 2000, p. 118-125)

ABSTRACT: The ammonia-water system is described by the Extended UNIQUAC model, which is an electrolyte model, formed by combining the original UNIQUAC model, the Debye-Hückel law and the Soave-Redlich-Kwong equation of state. The model is limited to temperatures below the critical temperature of ammonia. Vapor-liquid equilibria are described within the experimental accuracy. The accuracy of enthalpy calculations is better than ± 100 J mol-1, and heat capacity calculations deviate less than ± 1.0% from experimental data. The accurate description of the thermal properties is achieved by taking speciation equilibria into account. Model parameters valid in the temperature range 0 - 130°C are given.
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Kaj Thomsen and Peter Rasmussen, Modeling of vapor - liquid - solid Equilibria in gas - aqueous electrolyte systems, Chemical Engineering Science Vol. 54(1999)1787-1802

ABSTRACT: A thermodynamic model for the description of vapor-liquid-solid equilibria is introduced. This model is a combination of the extended UNIQUAC model for electrolytes and the Soave-Redlich-Kwong cubic equation of state. The model has been applied to aqueous systems containing ammonia and/or carbon dioxide along with various salts. Model parameters valid in the temperature range 0 - 110 °C, the pressure range from 0 - 100 bar, and the concentration range up to approximately 80 molal ammonia are given. The model parameters were evaluated on the basis of more than 7000 experimental data points.
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Kaj Thomsen, Peter Rasmussen, and Rafiqul Gani, Simulation and optimization of fractional crystallization processes. Chemical Engineering Science, Vol. 53(1998)1551-1564.
ABSTRACT: A general method for the calculation of various types of phase diagrams for aqueous electrolyte mixtures is outlined. It is shown how the thermodynamic equilibrium precipitation process can be used to satisfy the operational needs of industrial crystallizer/centrifuge units. Examples of simula tion and optimization of fractional crystallization processes are shown. In one of these examples a process with multiple steady states is analyzed. The thermodynamic model applied for describing the highly non-ideal aqueous electrolyte systems is the Extended UNIQUAC model.
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Kaj Thomsen, Aqueous electrolytes: model parameters and process simulation. Ph.D. thesis, (1997). Department of Chemical Engineering, Technical University of Denmark. Download thesis in pdf format

ABSTRACT: This thesis deals with aqueous electrolyte mixtures. The Extended UNIQUAC model is being used to describe the excess Gibbs energy of such solutions. Extended UNIQUAC parameters for the twelve ions Na+, K+, NH4+, H+, Cl-, NO3-, SO42-, HSO4-, OH-, CO32-, HCO3-, and S2O82- are estimated. A computer program including a steady state process simulator for the design, simulation, and optimization of fractional crystallization processes is presented.
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Kaj Thomsen, Peter Rasmussen, and Rafiqul Gani, Correlation and Prediction of Thermal Properties and Phase Behaviour for a Class of Aqueous Electrolyte Systems. Chemical Engineering Science, Vol. 51(1996)3675-3683.

ABSTRACT: An extended UNIQUAC model is used to describe phase behaviour (VLE, SLE) and thermal properties (heat of mixing, heat capacity) for aqueous solutions containing ions like (Na+, K+, H+) (Cl-, NO3-, SO42-, OH-, CO32-, HCO3-). A linear temperature dependence of the binary interaction parameters allows good agreement with experimental data in the temperature range 0-110°C.
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Kaj Thomsen, Rafiqul Gani, and Peter Rasmussen, Synthesis and analysis of processes with electrolyte mixtures. Computers and Chemical Engineering 19S(1995)S27-S32

ABSTRACT: A computer aided system for synthesis, design and simulation of crystallization and fractional crystallization processes with electrolyte mixtures is presented. The synthesis methodology is based on the use of computed solubility diagrams for the corresponding electrolyte systems. For a specified crystallizer and product(s), the process flowsheet along with conditions of operation is determined while for a specified feed mixture and product(s), the process flowsheet together with the type of crystallizer is determined. In order to verify the "determined" flowsheet an option to perform steady state simulation is also provided. Examples highlighting the various features of the computer aided system are presented.
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Last updated 07.09.2016
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