| dc.description.abstract | This study aims to investigate protonic ceramic fuel cell (PCFC)/gas turbine (GT) hybrid systems fed by hydrocarbon fuels. Three designs are built: case 1, case 2, and case 3. Cases 1, 2, and 3 flow high-quality heat from GT into a cathode preheater, a reformer, and proportionally into anode and cathode preheaters, respectively. Hydrocarbon fuels such as methanol, methane, propane, and butane are chosen as the input fuels, in which methanol is reformed externally, and other gaseous fuels are reformed internally. Next, several parameters such as air and fuel stoichiometry, steam-to-carbon ratio (S/C), fuel utilization factor (Uf), and anode off-gas recycling ratio (AOGR) are also analyzed. Thermolib is employed to build the system with input parameters obtained from references.
The results in methanol-fed PCFC/GT hybrid systems show that the appropriate configuration is when the high-quality heat from GT flows proportionally into anode and cathode preheaters, as indicated in case 3. The maximum efficiency achieved is 73%, with a total exergy destruction of 211 kW. The results show that the exergy efficiency of fuel cells increases by reflowing the heat from GT to preheaters. Moreover, utilizing the coolant as the heat source for a reformer and evaporator can improve system efficiency.
Results of the AOGR location study show that reflowing anode outlet gas into anode inlet is appropriate in a methanol-fed PCFC/GT hybrid system as the operating temperature of the reformer can be maintained. Moreover, an anode preheater can work maximally with low exergy destruction, as indicated in case 3.
The results of the parameter variation show that PCFC power output increases along with a larger AOGR ratio. It is inseparable from an enormous amount of hydrogen flowing into the anode. Conversely, GT power output decreases as turbine inlet temperature and reactant of combustor decrease. The results show that GT power reduction is relatively small compared to fuel cell power rise, so the system efficiency increases with a larger AOGR ratio. Moreover, installing AOGR also can maintain a PCFC/GT hybrid system operating at maximum power under different Uf variations.
The results of Uf variations show that this parameter is essential in energy distribution into PCFC and GT, in which cell power output increases along with increasing Uf, while GT power output decreases. The results also show that PCFC/GT hybrid system can produce maximum power at low Uf with AOGR, and a hybrid system has peak power at high Uf without AOGR.
The results of the reactant effects show that an increase in fuel must follow an increase in air and vice versa. The objective is to run the system under the best possible conditions: 71% to 72%. For example, the fuel stoichiometry 1.05, 1.1, and 1.2 need to feed with the air stoichiometry 2.5, 3, and 3.5, respectively.
The second system analyzed is IR-PCFC/GT hybrid system. The results show that a proportional heat distribution into anode and cathode preheaters can enhance the system efficiency, as indicated in case 3. The optimized parameters for this system are as follows: air stoichiometry of 2, Uf of 0.85, S/C of 2, and methane as a fuel.
This work contributes to the scientific community for (i) determining an appropriate configuration in PCFC/GT hybrid system, (ii) understanding a good AOGR position, (iii) and choosing the reasonable fuel, S/C, Uf, air stoichiometry, and fuel stoichiometry.
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