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    Design and evaluation of the sorption enhanced steam reforming and solid oxide fuel cell integrated system with anode exhaust gas recirculation for combined heat and power generation
    (2017-01-01)
    Wiranarongkorn, Kunlanan
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    Ponpesh, Pimporn
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    Arpornwichanop, Amornchai
    Solid oxide fuel cell (SOFC) is an electrochemical device for power generation with high efficiency and low environmental impact. Due to a high-temperature operation of SOFC, useful heat can be recovered to enhance its system efficiency. Regarding the environmental concern, bio-oil, the renewable liquid fuel, can be applied to SOFC system. In this study, the SOFC integrated with a steam reforming of bio-oil is considered. A sorption enhanced reforming process is studied for the production of high purity hydrogen for SOFC, and the anode gas recirculation in the SOFC system is proposed for the system improvement. Modeling of such an integrated process is performed using Aspen Plus simulator. As heat and power are generated from the SOFC system, the effect of key design parameters; fuel utilization and recirculation ratio of the anode gas, on a heatto-power ratio is analyzed. The system performance regarding to the electrical and thermal efficiencies is also evaluated. The results show that increasing the anode recirculation ratio increases the combined heat and power (CHP) performance, but increasing the fuel utilization decreases the thermal efficiency. It is also found that the appropriate range of heat-to-power ratio of the system varies from 0.24 to 0.89.
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    Optimization of a membrane-based oxidative coupling of methane reactor using surface response methodology
    (2013-01-01) ;
    Tiraset, Sirikarn
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    Saebea, Dang
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    Paengjuntuek, Woranee
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    Arpornwichanop, Amornchai
    An oxidative coupling of methane (OCM) is a promising process to convert methane into ethylene and ethane; however, it suffers from the relatively low selectivity and yield of ethylene at high methane conversion. In this study, a membrane reactor is applied to the OCM process in order to prevent the deep oxidation of a desirable ethylene product. First, simulations of the OCM reactor based on mass and energy balances coupled with detailed OCM kinetic model are performed and effects of key operating parameters, such as temperature, methane-to-oxygen feed ratio and methane flow rate, on the OCM reactor performance in terms of CH<inf>4</inf> conversion, C<inf>2</inf> selectivity and yield are analyzed. To determine its optimal operating conditions, an optimization of the OCM membrane reactor using a surface response methodology is carried out in the second part. The central composite design (CCD) is used to study the interaction of process variables (i.e., temperature, feed flowrate and CH<inf>4</inf>/O<inf>2</inf> ratio) and to find the optimum process operation to maximize the C<inf>2</inf> products yield. © 2013, AIDIC Servizi S.r.l.
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    Analysis of unbalanced pressure PEM electrolyzer for high pressure hydrogen production
    (2017-01-01)
    Saebea, Dang
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    Hacker, Viktor
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    Assabumrungrat, Sutthichai
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    Arpornwichanop, Amornchai
    Proton exchange membrane (PEM) electrolyzer is a promising technology and likely to be an important hydrogen generator. The ability to produce high purity hydrogen and deliver it at relatively high pressure is an important advantage of the PEM electrolyzer technology. In this work, the high pressure PEM electrolyzer without the need for external compression is studied. The simulation of the electrolyzer is performed based on an electrochemical model with consideration of hydrogen permeation. The effect of cathode pressure and membrane thickness on electrolyzer performance is studied. The explosion limit of a hydrogen-oxygen mixture in the anode is also taken into consideration. The electrochemical compression shows advantage in term of delivering hydrogen at high pressure with having less effect on performance and low power requirement. The increase of cathode pressure slightly affects the electrolyzer performance. The high pressure operation at the cathode and the use of thin membranes cause hydrogen crossover from the cathode to anode, especially at high current density operation.
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    Modeling and optimization of proton-conducting solid oxide electrolysis cell: Conversion of CO2 into value-added products
    (2016-11-01)
    Namwong, Lawit
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    Authayanun, Suthida
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    Saebea, Dang
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    Arpornwichanop, Amornchai
    Proton-conducting solid oxide electrolysis cells (SOEC-H<sup>+</sup>) are a promising technology that can utilize carbon dioxide to produce syngas. In this work, a detailed electrochemical model was developed to predict the behavior of SOEC-H<sup>+</sup> and to prove the assumption that the syngas is produced through a reversible water gas-shift (RWGS) reaction. The simulation results obtained from the model, which took into account all of the cell voltage losses (i.e., ohmic, activation, and concentration losses), were validated using experimental data to evaluate the unknown parameters. The developed model was employed to examine the structural and operational parameters. It is found that the cathode-supported SOEC-H<sup>+</sup> is the best configuration because it requires the lowest cell potential. SOEC-H<sup>+</sup> operated favorably at high temperatures and low pressures. Furthermore, the simulation results revealed that the optimal S/C molar ratio for syngas production, which can be used for methanol synthesis, is approximately 3.9 (at a constant temperature and pressure). The SOEC-H<sup>+</sup> was optimized using a response surface methodology, which was used to determine the optimal operating conditions to minimize the cell potential and maximize the carbon dioxide flow rate.
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    Effect of anode-cathode exhaust gas recirculation on energy recuperation in a solid oxide fuel cell-gas turbine hybrid power system
    (2016-01-01)
    Saebea, Dang
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    Authayanun, Suthida
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    Arpornwichanop, Amornchai
    A solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system supplying liquid fuel as ethanol exhibits promise as an auxiliary power unit. In this study, the recirculation of anode and cathode exhaust gas in the SOFC-GT system is proposed to improve the efficiency of heat management in the SOFC-GT hybrid system. The key operating parameters, such as fuel utilization factor and the cell and GT temperatures, are analyzed in terms of the performance of the SOFC-GT hybrid systems. The simulation results show that the recirculation of anode and cathode exhaust gas has a direct impact on the turbine performance. To maintain the inlet temperature of the small turbine in the range of 873-1223 K, the amount of fuel and air added to the combustor to control the turbine inlet temperature on the system performance is also investigated. A SOFC-GT hybrid system with both anode and cathode exhaust gas recirculation achieves the highest system and thermal efficiency.
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    Exergoeconomics of hydrogen production from biomass air-steam gasification with methane co-feeding
    (2017-01-01)
    Nakyai, Teeranun
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    Authayanun, Suthida
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    Arpornwichanop, Amornchai
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    Assabumrungrat, Suttichai
    Biomass is one of the most promising energy sources for hydrogen production. However, biomass gasification has a low hydrogen content in the producer gas. To increase the hydrogen yield, the co-feeding of methane into biomass gasification is proposed in this study. The type of gasifying agent is a key factor in the determination of the content of the hydrogen product. To compare the designs and find the best performance criteria of a process, not only energy and exergy analyses but also a cost analysis of the process should be investigated. In the present study, the effects of various types of gasifying agent, i.e., air and both steam and air, for the biomass gasification with/without methane co-feeding are investigated through an exergoeconomic analysis. It is observed that the air-steam used as an agent achieves high energy and exergy efficiency. Methane co-feeding can improve the energy and exergy efficiency. In exergoeconomic analysis, the specific exergy cost (SPECO) method is applied to investigate the unit cost of hydrogen. The economic reveal that the biomass gasification using air-steam as an agent with methane co-feeding also presented the lowest unit hydrogen cost of 2.69 $/kg. The unit exergy cost of hydrogen is 0.068 $/kW h.
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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) ;
    Chatrattanawet, Narissara
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    Arpornwichanop, Amornchai
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    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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    Thermodynamic analysis of solid oxide fuel cell system using different ethanol reforming processes
    (2015-06-08)
    Thanomjit, Chollaphan
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    Ponpesh, Pimporn
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    Arpornwichanop, Amornchai
    In this study, a performance of a solid oxide fuel cell (SOFC) system integrated with different ethanol reforming processes (i.e., steam reforming (SR), partial oxidation (POX) and autothermal reforming (ATR)) is investigated with the aim to determine a suitable ethanol reforming process for the SOFC system. The thermodynamic analysis of the SOFC system operated under steady state conditions was performed using flowsheet simulator. A detailed electrochemical model incorporating all voltage losses (i.e., activation, ohmic and concentration losses) was considered. The simulation results showed that increases in reformer and SOFC temperatures can improve the electrical performance of the SOFC system. The electrical performance of the SOFC-SR is maximized because this reforming process provides the highest hydrogen yield. However, because the SOFC included an internal methane reformation, electrical performances of SOFC systems with different reforming systems are slightly different. When the thermal efficiency was determined, it was revealed that the SOFC-POX system had a higher thermal efficiency with an increasing O/E and decreasing reformer and SOFC temperatures.
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    Biomass gasification of sugarcane leftover for green diesel production
    (2018-01-01)
    Chatrattanawet, N.
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    Kanjanasorn, W.
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    Authayanun, S.
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    Saebea, D.
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