Numerical modeling for preliminary design of the hydrogen production electrolyzer in the Westinghouse hybrid cycle

Jomard, Florent; Feraud, Jean-Pierre; Caire, Jean-Pierre

doi:10.1016/j.ijhydene.2007.12.052

Cited by 34 publications

(22 citation statements)

References 23 publications

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“…Many papers incorrectly report the standard reduction potential for the sulfite-sulfate couple to be 0.17 V vs. SHE [3,4,10,11,12]. It is likely that this value was obtained from the original proposal of the HyS cycle, in which the inventors used the well-known relationship between the Gibbs free energy and the equilibrium cell potential to calculate E° [13].…”

Section: Two Different Pem Sde Configurations Are Being Developed Undmentioning

confidence: 99%

“…The hybrid sulfur (HyS) cycle has received much attention recently as a possible means for the efficient large-scale production of clean hydrogen [1,2,3,4,5,6,7]. Like other thermochemical cycles, it has the advantage over traditional methods of hydrogen production in that it does not consume fossil fuels or contribute to greenhouse gas emissions when coupled with advanced, high-temperature nuclear or high-temperature solar heat sources.…”

Section: Introductionmentioning

confidence: 99%

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A thermodynamic analysis of the SO2/H2SO4 system in SO2-depolarized electrolysis

Gorensek

Staser

Stanford

et al. 2009

International Journal of Hydrogen Energy

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The hybrid sulfur thermochemical cycle has been proposed as a means to produce efficiently massive quantities of clean hydrogen using a high-temperature heat source like nuclear or solar.The cycle consists of two steps, one of which is electrolytic. The reversible cell potential for this step and, hence, the resulting operating potential will depend on the concentrations of dissolved SO 2 and sulfuric acid at the electrode. To understand better how these are related as functions of temperature and pressure, an Aspen Plus phase equilibrium model using the OLI Mixed Solvent Electrolyte physical properties method was employed to determine the activities of the species present in the system. These activities were used in conjunction with the Nernst equation to determine the reversible cell potential as a function of sulfuric acid concentration, temperature and pressure. A significant difference between the reversible and actual cell potentials was found, suggesting that there may be considerable room for reducing the operating potential.

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Section: Two Different Pem Sde Configurations Are Being Developed Undmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A thermodynamic analysis of the SO2/H2SO4 system in SO2-depolarized electrolysis

Gorensek

Staser

Stanford

et al. 2009

International Journal of Hydrogen Energy

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The high temperature decomposition of H 2 SO 4 to SO 2 , O 2 , and H 2 O is suited for use with advanced gas-cooled nuclear reactor heat sources or solar receiver arrays. [1][2][3][4][5][6][7] The electrolysis step described here is coupled with the high temperature step to complete the cycle.…”

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confidence: 99%

Quantifying Individual Potential Contributions of the Hybrid Sulfur Electrolyzer

Staser

Gorensek

Weidner

2010

J. Electrochem. Soc.

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The hybrid sulfur cycle has been investigated as a means to produce clean hydrogen efficiently on a large scale by first decomposing H 2 SO 4 to SO 2 , O 2 , and H 2 O and then electrochemically oxidizing SO 2 back to H 2 SO 4 with the cogeneration of H 2 . Thus far, it has been determined that the total cell potential for the hybrid sulfur electrolyzer is controlled mainly by water transport in the cell. Water is required at the anode to participate in the oxidation of SO 2 to H 2 SO 4 and to hydrate the membrane. In addition, water transport to the anode influences the concentration of the sulfuric acid produced. The resulting sulfuric acid concentration at the anode influences the equilibrium potential of and the reaction kinetics for SO 2 oxidation and the average conductivity of the membrane. A final contribution to the potential loss is the diffusion of SO 2 through the sulfuric acid to the catalyst site. Here, we extend our understanding of water transport to predict the individual contributions to the total cell potential. © 2010 The Electrochemical Society. ͓DOI: 10.1149/1.3397901͔ All rights reserved. The hybrid sulfur ͑HyS͒ cycle has gained attention due to the possibility of using this process to produce clean hydrogen on a large scale at efficiencies higher than those using water electrolysis.1-19 The high temperature decomposition of H 2 SO 4 to SO 2 , O 2 , and H 2 O is suited for use with advanced gas-cooled nuclear reactor heat sources or solar receiver arrays.1-7 The electrolysis step described here is coupled with the high temperature step to complete the cycle. We developed a gas-fed anode electrolyzer in which SO 2 is oxidized to H 2 SO 4 via the following reaction 11,[14][15][16][17][18] We have successfully carried out Reactions 1 and 2 over a range of operating conditions ͑i.e., temperature, flow rate, and membrane pressure differential͒ and design variations ͑i.e., catalyst loading and membrane type and thickness͒. [14][15][16][17] We have also accurately predicted water transport and correlated the operating potential to the sulfuric acid concentration produced at the anode. [15][16][17] We have shown that the concentration of sulfuric acid produced at the anode increases with current density and that the sulfuric acid concentration at the anode influences the cell potential via the reversible cell potential U eq . 18Although we have previously correlated cell potential to acid concentration and hence water transport, a quantitative measure of the various potential losses has never been made. In this discussion, we present a comprehensive investigation of the components that make up the total cell potential ͑i.e., reversible cell potential, membrane resistance, and catalyst activity͒ to better understand and improve electrolyzer performance and operation. ExperimentalThe experimental setup was the same as that described previously.14-17 The cell was a standard 10 cm 2 cell from Fuel Cell Technologies, Inc. Reactants and products were fed to and from the cell through Kynar manifolds inst...

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] In this thermochemical cycle, sulfuric acid is decomposed at high temperature ͑ϳ850°C͒ to SO 2 and water, and the SO 2 is converted back to sulfuric acid in a proton exchange membrane ͑PEM͒ electrolyzer. Hence, the sulfur compounds are internally recycled, such that the overall process decomposes water into hydrogen and oxygen.…”

mentioning

confidence: 99%

Sulfur Dioxide Crossover during the Production of Hydrogen and Sulfuric Acid in a PEM Electrolyzer

Weidner

2009

J. Electrochem. Soc.

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A proton exchange membrane (PEM) electrolyzer has been investigated as a viable system for the electrolysis step in the thermochemical conversion of sulfur dioxide to sulfuric acid for the large-scale production of hydrogen. Unfortunately, during operation, sulfur dioxide can diffuse from the anode to the cathode. This has several negative effects, including reduction to sulfur that could potentially damage the electrode, consumption of current that would otherwise be used for the production of hydrogen, introduction of oxygen and SO2 to the hydrogen stream, and loss of sulfur to the cycle. However, proper water management can reduce or eliminate the transport of SO2 to the cathode. Here we present model simulations and experimental data for the flux of SO2 to the cathode as a function of current density and pressure differential across the membrane and show how water transport influences SO2 crossover. Understanding SO2 crossover is important in evaluating both the lifetime of the electrolyzer and membranes developed to limit SO2 crossover.

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Numerical modeling for preliminary design of the hydrogen production electrolyzer in the Westinghouse hybrid cycle

Cited by 34 publications

References 23 publications

A thermodynamic analysis of the SO2/H2SO4 system in SO2-depolarized electrolysis

A thermodynamic analysis of the SO2/H2SO4 system in SO2-depolarized electrolysis

Quantifying Individual Potential Contributions of the Hybrid Sulfur Electrolyzer

Sulfur Dioxide Crossover during the Production of Hydrogen and Sulfuric Acid in a PEM Electrolyzer

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