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Thermodynamic analysis of a proton conducting SOFC integrated system fuelled by different renewable fuels
(2021-03-19)
Saebea, Dang
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Arpornwichanop, Amornchai
;
Patcharavorachot, Yaneeporn
This work proposes a power generation system consisting of steam reformer and SOFC–H+ fuelled by different types of fuel, i.e., ethanol, glycerol and biogas. The performance analysis of integrated system is performed based on thermodynamic calculation through Aspen Plus simulator. The total of the Gibbs free energy minimization is used to determine product composition at equilibrium. The electrochemical model not only considers all voltage losses but also includes the effect of current leakage as a result from the electrolyte used. Considering the operating condition of steam reformer, it is found that the gas product contains the highest amount of hydrogen without the carbon formation when reformer is operated at 973 K with steam to carbon ratio of 1. In addition, the simulation results show that the SOFC–H+ operated at 973 K and 1 A/cm2 can provide a suitable compromise between system performances and exhaust gas composition. The use of glycerol reformate has the highest cell and system efficiencies and fuel utilization compared to the others. In addition, the integrated system fuelled by glycerol can release low CO amount whereas there is more heat provided to the surrounding. Therefore, it can be concluded that glycerol is suitable renewable fuel for SOFC–H+ integrated system.
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Optimization of hydrogen production from three reforming approaches of glycerol via using supercritical water with in situ CO2 separation
(2019-01-22)
Patcharavorachot, Yaneeporn
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Chatrattanawet, Narissara
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Arpornwichanop, Amornchai
;
Assabumrungrat, Suttichai
A pathway for hydrogen production from supercritical water reforming of glycerol integrated with in situ CO<inf>2</inf> removal was proposed and analyzed. The thermodynamic analysis carried out by the minimizing Gibbs free energy method of three glycerol reforming processes for hydrogen production was investigated in terms of equilibrium compositions and energy consumption using AspenPlus™ simulator. The effect of operating condition, i.e., temperature, pressure, steam to glycerol (S/G) ratio, calcium oxide to glycerol (CaO/G) ratio, air to glycerol (A/G) ratio, and nickel oxide to glycerol (NiO/G) ratio on the hydrogen production was investigated. The optimum operating conditions under maximum H<inf>2</inf> production were predicted at 450 °C (only steam reforming), 400 °C (for autothermal reforming and chemical looping reforming), 240 atm, S/G ratio of 40, CaO/G ratio of 2.5, A/G ratio of 1 (for autothermal reforming), and NiO/G ratio of 1 (for chemical looping reforming). Compared to three reforming processes, the steam reforming obtained the highest hydrogen purity and yield. Moreover, it was found that only autothermal reforming and chemical looping reforming were possible to operate under the thermal self-sufficient condition, which the hydrogen purity of chemical looping reforming (92.14%) was higher than that of autothermal reforming (52.98%). Under both the maximum H<inf>2</inf> production and thermal self-sufficient conditions, the amount of CO was found below 50 ppm for all reforming processes.
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Hydrogen and power generation from supercritical water reforming of glycerol and pressurized SOFC integrated system: Use of different CO2 adsorption process
(2018-09-13)
Patcharavorachot, Yaneeporn
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Saebea, Dang
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Authayanun, Suthida
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Arpornwichanop, Amornchai
The performance analysis of an integrated system of glycerol supercritical water reforming and pressurized SOFC was presented. The use of different CO<inf>2</inf> adsorption processes that include in situ and ex situ processes was compared to determine the suitable process for hydrogen and power generations. The influence of operating condition, e.g., temperature and pressure of reformer, supercritical water to glycerol (S/G) molar ratio, and calcium oxide to glycerol (CaO/G) molar ratio was examined. Then, the electrical performance of each integrated process was considered with respect to the SOFC conditions comprising temperature, pressure, and current density. The simulation results revealed that both processes have same favourable conditions for temperature and pressure operated at 800 °C and 240 atm, respectively. The suitable S/G and CaO/G molar ratios for in situ process are 10 and 2 whereas those for ex situ process are 20 and 1. Under these conditions, maximum hydrogen can be achieved as 87% and 75% for in situ and ex situ processes, respectively. When both integrated processes are operated at the optimal SOFC conditions as 900 °C, 4 atm, and current density of 10,000 A/m2, the SOFC efficiency of 71.56% and 62.12% can provide for in situ and ex situ processes, respectively.
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Performance and environmental study of a biogas-fuelled solid oxide fuel cell with different reforming approaches
(2018-03-01)
Chatrattanawet, Narissara
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Saebea, Dang
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Authayanun, Suthida
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Arpornwichanop, Amornchai
;
Patcharavorachot, Yaneeporn
In this work, solid oxide fuel cells (SOFCs) using biogas as the fuel with two different reforming approaches, i.e., external and internal reforming, were studied to determine the optimal operation conditions for each approach. Thermodynamic analysis was performed using a flowsheet simulator. The equilibrium gas composition was calculated by minimizing the Gibbs free energy. An electrochemical model that includes three voltage losses (i.e., activation, ohmic, and concentration losses) was used to predict the performance of the SOFCs. The simulation results showed that the reformer in the external reforming SOFC should be operated at a temperature of 973 K, a pressure of 1 atm, and a steam-to-carbon molar ratio of 0.5. In performance analysis, the simulation results indicated that both approaches have the same optimal operating conditions, i.e. a temperature of 1173 K, a pressure of 3 atm, and a current density of 5000 A/m2. Under the same operating conditions, the internal reforming SOFC exhibited better electrical efficiency than that of the external reforming SOFC. Considering the CO<inf>2</inf> and CO emissions, the exhaust gas obtained from the anode side of the internal reforming SOFC contained 7.4% CO<inf>2</inf> and 37.9% CO, which are higher values than those for the external reforming SOFC (1.9% CO<inf>2</inf> and 32.5% CO).
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Effect of different fuel options on performance of high-temperature PEMFC (proton exchange membrane fuel cell) systems
(2014-04-15)
Authayanun, Suthida
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Saebea, Dang
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Patcharavorachot, Yaneeporn
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Arpornwichanop, Amornchai
High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have received substantial attention due to their high CO (carbon monoxide) tolerance and simplified water management. The hydrogen and CO fractions affect the HT-PEMFC performance and different fuel sources for hydrogen production result in different product gas compositions. Therefore, the aim of this study is to investigate the theoretical performance of HT-PEMFCs fueled by the reformate gas derived from various fuel options (i.e., methane, methanol, ethanol, and glycerol). Effects of fuel types and CO poisoning on the HT-PEMFC performance are analyzed. Furthermore, the necessity of a water-gas shift (WGS) reactor as a CO removal unit for pretreating the reformate gas is investigated for each fuel type. The methane steam reforming shows the highest possibility of CO formation, whereas the methanol steam reforming produces the lowest quantity of CO in the reformate gas. The methane fuel processing gives the maximum fraction of hydrogen (≈0.79) when the WGS reactor is included. The most suitable fuel is the one with the lowest CO poisoning effect and the maximum fuel cell performance. It is found that the HT-PEMFC system fueled by methanol without the WGS reactor and methane with WGS reactor shows the highest system efficiency (≈50%). © 2014 Elsevier Ltd.

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