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Purpose: In this paper, the free vibration characteristics of a coupled functionally graded beam system(CFGBS) with arbitrary boundary conditions are presented based on the first-order shear deformation beam theory(FSDBT) and Haar wavelet method (HWM) for the first time. Method: A coupled beam system made of functionally graded material (FGM) consist of two straight beams and one curved beam, i.e., straight-curved-straight beam. For modeling the general boundary conditions, the artificial spring technique is employed. The individual beams of the coupled beam system are connected by continuous condition using the artificial spring technique. The displacement fields are derived based on the FSDBT and the governing equation of beam system is obtained by applying the Hamilton's principle. All displacement functions of the CFGBS are expanded by the Haar wavelet series and its integrals, and a discretized characteristic equation is obtained. Results: The accuracy and reliability of the proposed method for vibration characteristics analysis of the CFGBS considered in this paper are confirmed, and the new vibration characteristics results of the CFGBS with various geometric dimensions, boundary conditions, and material parameters are presented through numerical examples. These new numerical results can be used as benchmark data for research in this field. [ABSTRACT FROM AUTHOR]

Non-slagging entrained flow gasification provides a number of advantages for gasification of high-ash-fusion-temperature (AFT) coals in comparison with the traditional slagging gasification. To further explore the gasification characteristics of high-AFT coals and determine the gasification condition for non-slagging entrained flow gasification, a typical Chinese high-AFT Huainan (HN) coal is gasified in an isothermal thermogravimetric analyzer (TGA) at temperatures between 1100 and 1500 °C with CO2 partial pressure range from 4.5 × 104 to 7.5 × 104 Pa. Volumetric model (VM), shrinking core model (SCM) and random pore model (RPM) are used to fit the experimental data for determining the kinetics. Results show that the gasification reactivity of HN coal char increases with the increase in temperature, the activation energy is around 80 kJ·mol−1, and the reaction order is 0.96, 0.78 and 0.69 with respect to VM, SCM and RPM, respectively. For all the investigated conditions, the RPM model better fits the experimental results. Thermogravimetry–differential scanning calorimetry (TG-DSC) and scanning electron microscopy–energy-dispersive X-ray analysis (SEM–EDX) technologies are applied to examine the ash fusibility of HN coal. The apparent ash fusion behavior is observed around the temperature of 1300 °C due to the partial melting of fayalite and almandite. To minimize ash fusion and coal ash agglomeration, a temperature of 1200 °C is suggested for non-slagging gasifying HN coal. [ABSTRACT FROM AUTHOR]

The gasification/combustion kinetics of a typical Chinese high-ash-fusion-temperature (AFT) coal char, Huainan (HN) coal char, are analyzed using a thermogravimetric analyzer in this paper. The carbon conversion rate and the gasification/combustion reaction rate characteristics of HN coal char are studied. The initial gasification/combustion reaction rates are also analyzed in this paper. Results show that at 1300 °C, the gasification and combustion processes are changed from the chemical reaction control zone to the pore diffusion control zone. Thus, 1300 °C is recommended as the gasification temperature of the non-slagging EFGs system using high-AFT HN coal. Based on the isothermal method, a complementary method of iso-conversional and model based is used to analyze the gasification and combustion kinetics of HN coal char. The gasification/combustion reaction order m and activation energy E of HN coal char are obtained by iso-conversional method. The kinetic model equation f(α) is obtained based on a modified master plot method. The kinetic exponent n and the pre-exponential factor k0 are obtained by model-based method. The results of this work provide the useful data for designing the non-slagging EFGs using high-AFT coals. [ABSTRACT FROM AUTHOR]

Catalytic oxidation of CO into CO2 using copper–manganese–cerium (Cu–Mn–Ce) ternary oxides pellets represents a promising strategy for CO abatement. In this work, Cu–Mn–Ce ternary oxides catalyst pellets were prepared with different precursors by combining the wet-mixing-kneading and extrusion-spheronization methods. Physicochemical properties of the catalyst pellets were characterized by N2 adsorption–desorption, X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectrometry, transmission electron microscopy, X-ray photoelectron spectroscopy and H2-temperature programmed reduction. CO oxidation performance of the catalyst pellets were investigated in 0.5%CO, 2.0%H2O and balanced air using a fixed-bed reactor. Effects of granulation and precursor on the structure–activity relationships of the catalyst pellets were studied. The granulation process will adversely affect the CO oxidation performance of the as-prepared Cu–Mn–Ce ternary oxides catalysts. The catalyst pellet derived from nitrate precursors (CuMnCe-N) exhibits excellent CO oxidation activity (T50 = 115 °C), good time-on-stream stability (retains about 97% conversion after 85 min of reaction tested) and superior kinetic performance (Ea = 40.32 kJ/mol). The excellent CO oxidation performance is associated with the formed Cu–Ce–O solid solution, enhanced reducibility and dual synergistic effects. Besides, the desired catalyst pellet possesses good mechanical properties with a high mechanical strength of 14.70 MPa and a low attrition rate of 9.46%. The results will provide important guidance for designing efficient catalysts for CO oxidation. [ABSTRACT FROM AUTHOR]

Catalysts for the oxygen reduction reaction (ORR) play an important role in fuel cells. Alternative non-precious metal catalysts with comparable ORR activity to Pt-based catalysts are highly desirable for the development of fuel cells. In this work, we report for the first time a spinel MnCoO/C ORR catalyst consisting of uniform MnCoO nanoparticles cross-linked with two-dimensional (2D) porous carbon nanosheets (abbreviated as porous MnCoO/C nanosheets), in which glucose is used as the carbon source and NaCl as the template. The obtained porous MnCoO/C nanosheets present the combined properties of an interconnected porous architecture and a large surface area (175.3 m·g), as well as good electrical conductivity (1.15 × 10 S·cm). Thus, the as-prepared MnCoO/C nanosheets efficiently facilitate electrolyte diffusion and offer an expedite transport path for reactants and electrons during the ORR. As a result, the as-prepared porous MnCoO/C nanosheet catalyst exhibits enhanced ORR activity with a higher onset potential and current density than those of its counterparts, including pure MnCoO, carbon nanosheets, and Vulcan XC-72R carbon. More importantly, the porous MnCoO/C nanosheets exhibit a comparable electrocatalytic activity but superior stability and tolerance toward methanol crossover effects than a high-performance Pt/C catalyst in alkaline medium. The synthetic strategy outlined here can be extended to other nonprecious metal catalysts for application in electrochemical energy conversion. [ABSTRACT FROM AUTHOR]

A fluidized bed electrode could lower concentration polarization and activation polarization because of its high mass and heat transfer coefficient. The polarization characteristics of the fluidized bed electrode are systematically investigated in a molten carbonate fuel cell anode with an O/CO/gold reference electrode. The results show that polarization performance of the anode is improved by selecting proper flow rates of H, O and CO, choosing suitable nickel particle content together with appropriate O/CO ratio, and increasing reaction temperature as well as the area of the current collector. Limiting current density of 115.56 mA·cm is achieved under optimum performance as follows: a cylindrically curved nickel plate current collector, nickel particle content of 7.89%, the reaction temperature of 923 K, H flow rate of 275 mL·min, O/CO flow rate of 10/20 mL·min and O/CO ratio of 1 : 2. [ABSTRACT FROM AUTHOR]