Water Transport in MgSO<sub>4</sub>·7H<sub>2</sub>O During Dehydration in View of Thermal Storage

Donkers, Paj Pim; Beckert, Steffen; Pel, Leo L; Stallmach, Frank; Steiger, Michael; Adan, Ocg Olaf

doi:10.1021/acs.jpcc.5b08730

Cited by 60 publications

(58 citation statements)

References 32 publications

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“…The hydrolysis 48 In the lack of experimental study for the diffusion of H 2 O through MgCl 2 hydrates, we compared with the H 2 O diffusivity through other TCM epsomite (MgSO 4 Á7H 2 O). 49 Zhang et al 49 has reported the same order of magnitude for the diffusivity of H 2 O in the center of the MgSO 4 .7H 2 O. Donkers et al 50 has measured the DC of water in epsomite using NMR. They reported the DC in range of 10 À10 to 10 À9 m 2 s À1 in the temperature range of 293 to 413 K. In the light of their experimental and simulation results of water diffusion in other heat storage material (MgSO 4 Á7H 2 O), we can conclude that the present ReaxFF-MD simulations could mimic the water transport in MgCl 2 hydrates.…”

Section: Reaxff-md Simulations Of Mgcl 2 Hydratesmentioning

confidence: 88%

“…The activation energy and preexponential factor for H 2 O diffusion in MgCl 2 ÁH 2 O is higher than MgCl 2 Á2H 2 O, thus the net effect of the temperature on DC of H 2 O through MgCl 2 ÁH 2 O is similar to MgCl 2 Á2H 2 O. We have fitted the data on water-transport through the epsomite in the temperature range of 293 to 413 K. 50 The DC follows the Arrhenius equation. The activation energy and pre-exponential factor are 5.7 Â 10 À4 m 2 s À1 and 42.6 kcal mol À1 .…”

Section: Reaxff-md Simulations Of Mgcl 2 Hydratesmentioning

confidence: 99%

“…The diffusion coefficient (DC) of H 2 O through MgCl 2 hydrates are reported from Green-Kubo method at various temperature ranging from 300-500 K. The DC of H 2 O in the present study is of the same order of magnitude as the DC of H 2 O in MgSO 4 Á7H 2 O obtained both from MD simulations 49 and experiments. 50 The DC increases with temperature and follows the Arrhenius law for MgCl 2 ÁH 2 O and MgCl 2 Á2H 2 O. The diffusivity of H 2 O through MgCl 2 ÁH 2 O at 500 K increases 64 times compared with diffusivity at 300 K. Similarly, the diffusivity of H 2 O through MgCl 2 Á2H 2 O at 500 K increased 57 times compared to the 300 K. The diffusivity trend suggests that by increasing the temperature upto 500 K, the H 2 O transport (mass diffusion) can be improved.…”

Section: Reaxff-md Simulations Of Mgcl 2 Hydratesmentioning

confidence: 99%

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Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Pathak¹,

Nedea²,

Duin

et al. 2016

Phys. Chem. Chem. Phys.

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MgCl2 hydrates are considered as high-potential candidates for seasonal heat storage materials. These materials have high storage capacity and fast dehydration kinetics. However, as a side reaction to dehydration, hydrolysis may occur. Hydrolysis is an irreversible reaction, which produces HCl gas thus affecting the durability of heat storage systems. In this study, we present the parameterization of a reactive force field (ReaxFF) for MgCl2 hydrates to study the dehydration and hydrolysis kinetics of MgCl2·H2O and MgCl2·2H2O. The ReaxFF parameters have been derived by training against quantum mechanics data obtained from Density Functional Theory (DFT) calculations consisting of bond dissociation curves, angle bending curves, reaction enthalpies, and equation of state. A single-parameter search algorithm in combination with a Metropolis Monte Carlo algorithm is successfully used for this ReaxFF parameterization. The newly developed force field is validated by examining the elastic properties of MgCl2 hydrates and the proton transfer reaction barrier, which is important for the hydrolysis reaction. The bulk moduli of MgCl2·H2O and MgCl2·2H2O obtained from ReaxFF are in close agreement with the bulk moduli obtained from DFT. A barrier of 20.24 kcal mol(-1) for the proton transfer in MgCl2·2H2O is obtained, which is in good agreement with the barrier (19.55 kcal mol(-1)) obtained from DFT. Molecular dynamics simulations using the newly developed ReaxFF on 2D-periodic slabs of MgCl2·H2O and MgCl2·2H2O show that the dehydration rate increases more rapidly with temperature in MgCl2·H2O than in MgCl2·2H2O, in the temperature range 300-500 K. The onset temperature of HCl formation, a crucial design parameter in seasonal heat storage systems, is observed at 340 K for MgCl2·H2O, which is in agreement with experiments. The HCl formation is not observed for MgCl2·2H2O. The diffusion coefficient of H2O through MgCl2·H2O is lower than through MgCl2·2H2O, and can become a rate-limiting step. The diffusion coefficient increases with temperature and follows the Arrhenius law both for MgCl2·H2O and MgCl2·2H2O. These results indicate the validity of the ReaxFF approach for studying MgCl2 hydrates and provide important atomistic-scale insight of reaction kinetics and H2O transport in these materials.

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Section: Reaxff-md Simulations Of Mgcl 2 Hydratesmentioning

confidence: 88%

Section: Reaxff-md Simulations Of Mgcl 2 Hydratesmentioning

confidence: 99%

Section: Reaxff-md Simulations Of Mgcl 2 Hydratesmentioning

confidence: 99%

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Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Pathak¹,

Nedea²,

Duin

et al. 2016

Phys. Chem. Chem. Phys.

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“…Donkers has studied the water transport on 1-2 mm crystal of heptahydrate of magnesium sulfate by NRM analysis in dynamic condition under dry N 2 atmosphere [22]. This analysis allows to show that liquid water is formed in the pore of crystal during dehydration at 48 °C due to local increase of the water vapor pressure.…”

Section: Mgso 4 (S) + 7h 2 O (G) ↔ Mgso 4 • 7h 2 O (S)mentioning

confidence: 99%

Thermodynamic study of MgSO4 – H2O system dehydration at low pressure in view of heat storage

et al. 2017

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Study about magnesium sulfatewater vapor equilibrium proved to be very interesting especially on the use of dehydration-hydration reactions for the heat storage application in recent research. Heat is realized by hydration of lower hydrates as this reaction is exothermic. Therefore, reversible reaction, endothermic thermal dehydration of higher hydrates, is used for charging of system and in this state the energy can be stored over long time. Even if magnesium sulfate appears as promising candidate with high theoretical energy density of 2.8 GJ/m-3 , technological process is rather complicated. The main problem that thermodynamic and kinetic data are poorly understood to present. In these study salt hydrates equilibrium of magnesium sulfate was investigated by new approach. It makes possible to understand the dehydration reaction of MgSO 4 •6H 2 O for heat storage application. Dehydration reaction under various water vapor pressures and temperatures were investigated by thermogravimetric analysis. The result showed that water content in the solid phase is a function of temperature for given water vapor pressure. So, we can conclude that this magnesium sulfatewater vapor system is bivariant and some hydrates appear as the non-stoichiometric hydrates.

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“…However, not every salt shows better thermochemical heat storage properties. Several literatures have been reported for contemplated the demand of TCMs on the basis of high dehydration/hydration enthalpy, easily achievable reaction temperature (<150°C), material cyclability, toxicity and cost 26 . Previous studies reported that MgSO 4 7H 2 O has the potentially to store space heat energy for long term.…”

Section: Introductionmentioning

confidence: 99%

Hydration performance and cycling stability of threeTCM:MgSO₄,ZnSO₄andFeSO₄

2020

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Summary Thermochemical heat storage materials offer high‐energy storage densities and clean means of long‐term solar energy storage. The aim of the study is to assess the potential heat storage efficiency of salt hydrates, based on sufficient hydration/dehydration performance, water sorption and cyclicability. MgSO4 7H2O, ZnSO4 7H2O and FeSO4 7H2O were evaluated based on preselected criteria. The main highlights of the dehydration result show that higher enthalpy was obtained for MgSO4 and ZnSO4, shows 2256 and 1731 J g−1 enthalpy, respectively. During hydration process, six water molecules were absorb by MgSO4 and ZnSO4 after pre‐dehydrated temperature 150°C and 120°C, respectively. The cycle stability of MgSO4 and ZnSO4 showed better performance which give rise 1210 g−1 and 1155 J g−1 enthalpy, respectively. It was expected that FeSO4 would show higher cyclicability due to their higher enthalpy (1400 J g−1) in the first round; however, overhydration does not permit it to released larger energy. The impact of relative humidity on water sorption performance and rate of hydration were reported which showed that MgSO4 and ZnSO4 can uptake maximum water under 85% and 75% relative humidity. Ongoing studies and the booming progress of ZnSO4 7H2O illustrate that likewise MgSO4 7H2O, it is also the potential candidate and can be use in thermochemical heat storage devices. To bring zinc sulfate heptahydrate into market, more detail studies in fields of evaluation of advanced materials and development of efficient and compact prototypes are still required.

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Water Transport in MgSO₄·7H₂O During Dehydration in View of Thermal Storage

Cited by 60 publications

References 32 publications

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Thermodynamic study of MgSO4 – H2O system dehydration at low pressure in view of heat storage

Hydration performance and cycling stability of threeTCM:MgSO₄,ZnSO₄andFeSO₄

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Water Transport in MgSO4·7H2O During Dehydration in View of Thermal Storage

Cited by 60 publications

References 32 publications

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Reactive force field development for magnesium chloride hydrates and its application for seasonal heat storage

Thermodynamic study of MgSO4 – H2O system dehydration at low pressure in view of heat storage

Hydration performance and cycling stability of threeTCM:MgSO4,ZnSO4andFeSO4

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Water Transport in MgSO₄·7H₂O During Dehydration in View of Thermal Storage

Hydration performance and cycling stability of threeTCM:MgSO₄,ZnSO₄andFeSO₄