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21.
As an alternative, clean and sustainable solution, a biomass-based integrated power plant is designed and studied both thermodynamically and parametrically. Due to the environmental, economic and performance related advantages, the design of multigeneration energy plants is now increasing and becoming widespread technology. Biomass, which is one of the renewable power sources, is selected for the plant to be more sustainable and environmentally friendly. The proposed system using biomass as an energy source consists of several sub-plants integrated to utilize the waste thermal energy and to generate useful products which are electricity, hydrogen, fresh and hot water, heating, and cooling. In this paper, comprehensive work is carried out for plant modeling and simulation. The thermodynamic assessment results reveal that both energetic and exergetic effectiveness of the whole plant are 56.17% and 52.83%, which are affected positively by varying the reference state conditions, combustor temperature, biomass gasifier temperature, SOFC temperature and pressure, and biomass mass flow rate. In addition, the lowest energy and exergy efficiencies occur in the ORC combined ejector refrigeration cycle with 21.87% and 18.26%, respectively.  相似文献   
22.
Dimethyl ether (DME) partial oxidation (PO) was studied over 1 wt% Rh/Ce0.75Zr0.25O2 catalyst at temperatures 300–700 °C, O2:C molar ratio of 0.25 and GHSV 10000 h−1. The catalyst was active and stable under reaction conditions. Complete conversion of DME was reached at 500 °C, but equilibrium product distribution was observed only at T ≥ 650 °C. High concentration of CH4 and low contents of CO and H2 were observed at 500–625 °C 75 cm3 of composite catalyst 0.24 wt% Rh/Ce0.75Zr0.25O2/Al2O3/FeCrAl showed excellent catalytic performance in DME PO at O2:C molar ratio of 0.29 and inlet temperature 840 °C which corresponded to carbon-free region. 100% DME conversion was reached at GHSV of 45,000 h−1. The produced syngas contained (vol. %): 33.4 H2, 34.8 N2, 22.7 CO, 3.6 CO2 and 1.6 CH4. Composite catalyst demonstrated the specific syngas productivity (based on CO and H2) in DME PO of 42.8 m3·Lcat−1·h−1 (STP) and the syngas productivity of more than 3 m3·h−1 (STP) that was sufficient for 3 kWe SOFC feeding. PO of natural gas and liquified petroleum gas can be carried out over the same catalyst with similar productivity, realizing the concept of multifuel hydrogen generation. The syngas composition obtained via DME PO was shown to be sufficient for YSZ-based SOFC feeding.  相似文献   
23.
Solid oxide fuel cell technology is the technology which can be driving force to change the course of action of the modern era due to its optimal power generation features with maximum electrical efficiency for automobiles and household devices. Fuel cells can be best described as electrochemical devices that make use of fuel oxidation to convert chemical energy into electrical energy and also lower the amount of oxidant simultaneously.A typical SOFC consists of a cathode, anode and an electrolyte constituting a single cell. These single cells are stacked together for a bigger assembly to produce higher degree of power. The solid electrolyte fills the gap between the cathode and anode transporting O2− ions only. This leaves out electrons as transporting medium, which then pass through the cell via external circuit. Out of the two electrodes, oxidation of fuel takes place at the anode and reduction of oxygen takes place at the cathode. The SOFCs operate at higher temperatures of 600–1200°C producing heat as a byproduct of high quality, actively encouraging quick electrocatalysis utilizing non-precious metals and allowing internal restructuration. The SOFC can also work with high purity hydrogen for proton transport other than O2− ion transport. There are many ceramic materials which have been engineered to act as efficient electrolyte materials. Yttria-stabilized zirconia (YSZ) is the most widely used material as solid electrolyte in SOFC.The present review presents a detailed overview of the SOFC related materials and devices and is an effort to present various reported works in a concise manner.  相似文献   
24.
The methane steam reforming reaction is an extremely high endothermic reaction that needs a high temperature heat source. Various fuel cell hybrid systems have been developed to improve the thermal efficiency of the entire system. This paper presents a low temperature steam reformer for those hybrid systems to maximize the utilization of energy from a low temperature waste heat source. In this study, the steam reformer has a shell and tube configuration that is divided into the following zones: the inlet heat exchanging zone, the reforming zone and the exit heat exchanging zone. Four different configurations for methane steam reformers are developed to examine the effect of heat transfer on the methane conversion performance of the low temperature steam reformer. The experimental results show that the overall heat transfer area is a critical parameter in achieving a high methane conversion rate. When the heat transfer area increases about 30%, the results showed elevated dry mole fractions of hydrogen about 3% with about 30 °C rise of reformer outlet temperature.  相似文献   
25.
In this paper a fully three dimensional, multiphase, micro-scale solid oxide fuel cell anode transport phenomena numerical model is proposed and verified. The Butler-Volmer model was combined with empirical relations for conductivity and diffusivity - notably the Fuller-Shetler-Giddings equation, and the Fickian model for transport of gas reagents. FIB-SEM tomography of a commercial SOFC stack anode was performed and the resulting images were processed to acquire input data. A novel method for estimating local values of Triple Phase Boundary length density for use in a three-phase, three-dimensional numerical mesh was proposed. The model equations are solved using an in-house code and the results were verified by comparison to an analytical solution within the range of its applicability. A limited parametric study was performed to qualitatively assess simulation performance and impact of heterogeneity. Despite the high dependence of the SOFC anode performance on the geometry of its anisotropic, three-phase microstructure there are very few micro-scale numerical models simulating transport phenomena within these electrodes.  相似文献   
26.
To make SOFC high efficiency energy generation devices, thin ceramic films are proposed as their main components. The rate of the oxygen reduction reaction is relevant for the overall performance of the SOFC, hence a lot of attention is given to the cathodes and their interfaces. The airbrushed solution combustion (ASC) method was used to fabricate an LSM thin film on a dense YSZ substrate. A single phase LSM perovskite was obtained with very thin and interconnected porosity, and a small average grain size (55 nm). The nanostructured LSM thin film electrode showed a low total activation energy (1.27 eV) at high temperatures, but a high area specific resistance at 850°C (55 Ω.cm2). The activation energy for the dissociative adsorption and diffusion of oxygen was significantly low (1.27 eV), while the charge transfer and oxygen ion migration activation energy at the LSM/YSZ interface (1.28 eV) was closer to those usually reported.  相似文献   
27.
This paper carefully evaluates the electrocatalytic activity of Sr2FeMo0.5Mn0.5O6 (SFMM) double perovskite as a candidate to substitute the state-of-the-art Ni/YSZ fuel electrode. The electrochemical performance of a 40% SFMM/CGO composite electrode was studied in CO/CO2 and H2 with different oxygen partial pressure. Two different cell configurations are prepared at a relatively low temperature of 800 °C to increase the electrochemically active surface area. The cell was supported with a 150 μm 10Sc1CeSZ electrolyte in the first configuration. The cell in the second configuration was made by applying a 400 nm thin 8YSZ layer on 150 μm CGO electrolyte to improve the electrolyte ionic conductivity. Improving catalytic activity with increasing oxygen partial pressure is a key characteristic of the developed electrode. The polarization resistance of about 0.34 and 0.56 Ω cm2 at 750 °C in 3%H2O + H2 and 60% CO/CO2 makes this electrode a promising candidate for SOCs application.  相似文献   
28.
29.
The electrochemical response of infiltrated La0.5Ba0.5CoO3-δ (LBC) in porous La0.8Sr0.2Ga0.8Mg0.2O2.8 (LSGM) has been investigated. The thermal expansion coefficient (TEC) of the resulting electrode was measured, obtaining α?=?12.5?×?10?6 K?1, a value similar to that of LSGM. The polarization resistance (Rp) and the processes involved in the oxygen reduction reaction (ORR) for the new electrode were studied and analyzed through complex impedance spectroscopy measurements as a function of temperature and oxygen partial pressure (pO2), using a symmetrical cell. The value of Rp for the infiltrated LBC turned out to be lower than that measured for an electrode prepared with a composite LBC-LSGM (1:1?wt%) by an order of magnitude, for the temperature range 750?°C ≤ T?≤?900?°C, and about 5 times lower for the temperature range 450?°C≤ T?≤?650?°C. At 600?°C, the LBC infiltrated cathode exhibits a polarization resistance Rp =?0.22?Ω?cm2, in air. The complex impedance spectra show two processes, one identified as low frequency (LF),with a characteristic frequency of 10?Hz, and the other as intermediate frequency (IF), with a range between 0.05 and 2000?Hz. The LF process could be associated to the diffusion of oxygen in the gas phase through the pores of the electrode. Its resistance, RLF =?0.01?Ωc?m2, was found to be independent of the temperature and half of that obtained for the LBC composite cathode. On the other hand, the IF process is related to charge transfer at the electrode surface and the electrode-electrolyte interface. The LBC cobaltite infiltrated in the LSGM scaffolds offers an adequate thermal expansion coefficient and good electrocatalytic activity for the ORR.  相似文献   
30.
Image analysis and quantification were performed on porous scaffolds for building SOFC cathodes using the two types of YSZ powders. The two powders (U1 and U2) showed different particle size distribution and sinterability at 1300?°C. AC impedance on symmetrical cells was used to evaluate the performance of the electrode impregnated with 35-wt.% La0.8Sr0.2FeO3. For example, at 700?°C, the electrode from U2 powder shows a polarization resistance (Rp) of 0.21?Ω?cm2, and series resistance (Rs) of 8.5?Ω?cm2 for an YSZ electrolyte of 2-mm thickness, lower than the electrode from U1 powder (0.25?Ω?cm2 for Rp and 10?Ω?cm2 for Rs) does. The quantitative study on image of the sintered scaffold indicates that U2 powder is better at producing architecture of high porosity or long triple phase boundary (TPB), which is attributed as the reason for the higher performance of the LSF-impregnated electrode.  相似文献   
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