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Performance improvement of the proton-conducting solid oxide electrolysis cell coupled with dry methane reforming
(2023-02-28)
Patcharavorachot, Yaneeporn
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Chalee, Wissawa
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Saebea, Dang
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Arpornwichanop, Amornchai
The proton-conducting solid oxide electrolysis cell (H-SOEC) is a clean technology for syngas production from H<inf>2</inf>O and CO<inf>2</inf> through electrochemical and chemical reactions. However, it provides a low CO<inf>2</inf> conversion and produces a syngas product with a high H<inf>2</inf>O content. To improve the H-SOEC for syngas production, H-SOEC coupled with a dry methane reforming process (H-SOEC/DMR) was proposed in this work. The process flowsheet of the H-SOEC/DMR was developed and further used to evaluate the performance of the H-SOEC/DMR process. From the performance analysis of the H-SOEC/DMR process, it was found that the CO<inf>2</inf> and CH<inf>4</inf> conversions were higher than 90% and 80%, respectively, when the process was operated in the temperature range of 1073–1273 K. In addition, the result showed that a syngas product with a low H<inf>2</inf>O content could be obtained. Energy efficiency was then considered and the results indicated that the highest energy efficiency of 72.80% could be achieved when the H-SOEC/DMR process was operated at a temperature of 1123 K, pressure of 1 atm, and current density of 2500 A m−2. Based on a pinch analysis, a heat exchanger network was applied to the H-SOEC/DMR process that improved the energy efficiency to 81.46%. Finally, an exergy analysis was performed and showed that the H-SOEC/DMR unit had the lowest exergy efficiency as a high-temperature exhaust gas was released.
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Ba0·5Sr0·5(Co0·8Fe0.2)1-xTaxO3-δ perovskite anode in solid oxide electrolysis cell for hydrogen production from high-temperature steam electrolysis
(2021-02-08)
Prasopchokkul, P.
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Seeharaj, P.
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Kim-Lohsoontorn, P.
Among perovskite anodes in solid oxide electrolysis cell (SOEC), Ba<inf>0·5</inf>Sr<inf>0·5</inf>Co<inf>0·8</inf>Fe<inf>0·2</inf>O<inf>3-δ</inf> (BSCF) has gained much attention due to its dominantly high performance. However, the BSCF still suffers from chemical instability. In this study, the B-site of BSCF is partially substituted by a higher valence Ta5+ (5, 10, 15 and 20 mol%) to improve its structural stability - Ba<inf>0·5</inf>Sr<inf>0·5</inf>(Co<inf>0·8</inf>Fe<inf>0.2</inf>)<inf>1-x</inf>Ta<inf>x</inf>O<inf>3-δ</inf> (BSCFTax, 0 ≤ x ≤ 0.20). It is found that doping with higher valence Ta5+ increases both chemical stability and electrochemical performance of BSCF. Although the BSCFTa0.10 shows the lowest oxygen vacancies indicating by the ratio of adsorbed oxygen vacancies (O<inf>adsorbed</inf>) to lattice oxygen (O<inf>lattice</inf>), the electrochemical performance increases. The decrease in Co3+/Co4+ ratio results in increasing electronic conductivity in the anode. It is likely that proper amount of Ta5+ doping provide a balance between ionic and electronic conductivity in the anode and improved electrochemical performance. The symmetrical half-cells with electrolyte support (BSCFTa/YSZ/BSCFTa) are fabricated to determine the area specific resistance (ASR) and activation energy of conduction - BSCFTa0.10 shows the best performance. Cathode-supported Ni-YSZ/YSZ/BSCFTa0.10 also shows higher durability than Ni-YSZ/YSZ/BSCF (operating at current density −0.45 A cm−2 in electrolysis mode, 80 h, 800 °C and H<inf>2</inf>O to H<inf>2</inf> ratio of 70:30).
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Operational Analysis of a Proton-Conducting Solid Oxide Electrolysis Cell for Synthetic Fuel Production
(2021-01-01)
Bhichaiphab, Jinjutha
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Saebea, Dang
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Arpornwichanop, Amornchai
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Patcharavorachot, Yaneeporn
Methane and methanol as synthetic fuels can be produced from synthesis gas or syngas. A proton-conducting solid oxide electrolysis cell (H-SOEC) becomes a promising technology that can produce syngas from the co-electrolysis of steam and CO<inf>2</inf>. In this work, the synthetic fuel production from syngas produced by a H-SOEC was modelled and simulated through Aspen Plus simulation software. The composition of syngas and synthetic fuel were calculated by using the minimization of Gibbs free energy. Firstly, the steam to CO<inf>2</inf> (S/C) molar ratio in feed was determined to satisty the suitable stoichiometric number of each fuel. Further, the H-SOEC operating temperature was optimized. The simulation showed that at operation of H-SOEC as 650 °C and 1 atm, the optimal S/C molar ratio for methane and methanol productions is 4.69 and 3.52, respectively. Then, the effect of operation in fuel production was examined. The results indicated that methane flowrate of 0.2 kmol/h can be provided when reactor operates at 250 °C and 3 atm. For methanol production, 0.13 kmol/h of methanol can be generated at reactor operation as 250 °C and 80 atm. In addition, it was found that the methane production does not release CO and CO<inf>2</inf> to nature. Therefore, it can be concluded that the integrated system of H-SOEC and methane production is more attractive feature.
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Effect of sintering additives on barium cerate based solid oxide electrolysis cell for syngas production from carbon dioxide and steam
(2018-05-01)
Likhittaphon, S.
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Pukkrueapun, T.
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Seeharaj, P.
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Wetwathana Hartley, U.
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Laosiripojana, N.
The effect of sintering additives (NiO, Co<inf>2</inf>O<inf>3</inf>, and ZnO) on the performance of barium-cerate-based solid oxide electrolysis cell (SOEC) is investigated. The performance of the SOEC with different sintering additives is determined in terms of relative density, electrochemical performance, and catalytic activity toward reverse water gas shift reaction. BaCeO<inf>3</inf> (BC) and BaCe<inf>0.9</inf>Gd<inf>0.1</inf>O<inf>3−δ</inf> (BCG) are synthesized using conventional precipitation method, comparing to ultrasonic-assisted precipitation. The sintering additives promote both densification and grain growth. The relative density of the BCG without sintering additive is 69% while that of the BCG with 1 wt% of Co<inf>2</inf>O<inf>3</inf>, NiO and ZnO is 95%, 95% and 88%, respectively. The SEM images indicate that the BCG with sintering additives exhibits dense grains with relatively large grain size. Although the BGC with NiO and Co<inf>2</inf>O<inf>3</inf> exhibit maximum relative density, the sample with ZnO shows relatively highest conductivity with the lowest activation energy of conduction and the sample with NiO provides the largest CO yield and CO<inf>2</inf> conversion. The activation energy of conduction is found to be 375.41, 70.06, 66.86 and 61.80 kJ mol−1 for BCG, BCG with 1 wt% Co<inf>2</inf>O<inf>3</inf>, NiO and ZnO, respectively. The BCG with 1 wt% NiO provides the highest CO<inf>2</inf> conversion and CO yield at temperature below 700 °C (62% CO<inf>2</inf> conversion and 32% CO yield at 700 °C). Temperature program of oxidation (TPO) reveals that carbon deposition can cause the low CO yield at the operating temperature above 700 °C.
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Flowsheet-based model and exergy analysis of solid oxide electrolysis cells for clean hydrogen production
(2018-01-01)
Im-orb, Karittha
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Visitdumrongkul, Nuttawut
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Saebea, Dang
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Patcharavorachot, Yaneeporn
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Arpornwichanop, Amornchai
A solid oxide electrolysis cell (SOEC) is an electrochemical technology used for hydrogen production via a steam electrolysis reaction. Because the existing SOEC models are complicated, the aim of this study is to develop a user-friendly SOEC model in a flowsheet simulator (Aspen Plus). The developed model is used to perform a parametric analysis to investigate the effects of key process parameters, i.e., operating temperature, current density, steam concentration, sweep gas type and number of cells, on the SOEC performance. The simulation results show that the voltage and the overall overpotential decrease as the cell temperature increases, whereas the opposite trends are observed when the current density increases. From the energy and exergy analyses, the total energy demand slightly increases with cell temperature, whereas the electrical energy demand decreases. Based on an operating temperature of 1273 K when the SOEC uses oxygen as the sweep gas, the highest energy and exergetic efficiencies of 78.45% and 92.20% are achieved at a current density of 2500 A m−2 and at a steam concentration of 90% in a 500-cell stack.
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Performance comparison of solid oxide steam electrolysis cells with/without the addition of methane
(2016-07-15)
Patcharavorachot, Yaneeporn
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Thongdee, Sirapa
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Saebea, Dang
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Authayanun, Suthida
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Arpornwichanop, Amornchai
Hydrogen is considered a clean energy carrier for the future. At present, the production of hydrogen via a solid oxide electrolysis cell is of interest because water is the only reactant used; however, hydrogen production through electrolysis technology is still costly due to high electrical energy consumption. To reduce this energy demand, an addition of methane to the anode side of the solid oxide electrolysis cell, where it behaves like the anode side of the solid oxide fuel cell and generates heat and electricity to accomplish the electrolysis process, is one interesting method. In this study, modeling of the solid oxide fuel-assisted electrolysis cell is performed based on an electrochemical model to analyze the performance of the electrolyzer with/without the addition of methane in terms of the power input and the energy efficiency. In addition, the effect on the electrolyzer cell by key operating parameters, such as current density, steam fraction, steam-to-carbon ratio, temperature, pressure, steam utilization and fuel utilization, is presented. The simulation analysis shows that the performance of the solid oxide fuel-assisted electrolysis cell is higher than that of conventional solid oxide electrolysis cell, as it requires a lower power input. Furthermore, it is possible to run the solid oxide fuel-assisted electrolysis cell without an external electrical energy input.
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Low-temperature preparation of BaCeO3 through ultrasonic-assisted precipitation for application in solid oxide electrolysis cell
(2015-06-20)
Kim-Lohsoontorn, P.
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Paichitra, C.
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Vorathamthongdee, S.
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Seeharaj, P.
Barium cerate (BaCeO<inf>3</inf>) was synthesized using conventional precipitation and ultrasonic-assisted precipitation. The effect of precipitation parameters (precipitation precursor, precipitation agent, agent concentration and temperature) significantly affected %perovskite formation and crystallite size of the product. Precipitation with 1 M (NH<inf>4</inf>)<inf>2</inf>C<inf>2</inf>O<inf>4</inf> induced the formation of a single-phase BaCeO<inf>3</inf> while precipitation with 5-20 M NaOH provided a mixed phase of BaCeO<inf>3</inf> and CeO<inf>2</inf>. The %perovskite increased as increasing precipitation temperature; however, the crystallite size of the product also increased. Increasing ultrasonic intensity (30 and 150 W cm-2) during precipitation was found to increase the %perovskite and to reduce crystallite size. The precipitation with 1 M (NH<inf>4</inf>)<inf>2</inf>C<inf>2</inf>O<inf>4</inf> agent, using ultrasonic intensity at 150 W cm-2, provided single phase BaCeO<inf>3</inf> with crystallite size of 18.4 nm after calcination at 900 °C for 4 h. The electrochemical performance of the BaCeO<inf>3</inf> cell under steam electrolysis condition (controlled voltage from OCV to 1.5 V; 20% H<inf>2</inf>O, 40% H<inf>2</inf>, and 40% N<inf>2</inf>) was measured (600-800 °C) and the activation energy of conduction was calculated to be 0.78 eV.
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