Advanced Materials Research Vols. 953-954

Abstract: Char-cluster interactive combustion occurs widely in practical combustors. A 3-D mathematical model for char-cluster combustion is established. The combustion and gas-solid drag properties of a ten-particle char cluster are numerically studied. Detailed results regarding velocity vector, mass component, temperature distributions around and inside the cluster are revealed. Gas-solid drag forces acted on each combusting char particle are obtained and comparatively studied.

Abstract: This paper reported the fragmentation behavior of lignite coal particles during coal pyrolysis in fluidized bed reactor at temperature of 300°C,350°C,600°C,650°C. The particles with size of 2-4mm,4-6mm and 7-10mm pyrolyzed under N₂ atmosphere. The fragments were recovered by hopper, cooled to the ambient temperature and sieved in different ranks. Experimental results show that with the increasing of temperature and initial coal size due to internal overpressure induced by volatiles releasing and thermal stress caused by thermal gradient of coal intra-particles the intensity of fragmentation was enhanced monotonously, the number of fragments increased sharply and the average size of fragments declined.

Abstract: Cyclohexane dehydrogenation is an important process in the petrochemical industry, chemical raw material such as cyclohexanol, cyclohexanone,benzene and cyclohexene can be produced from which.Divided cyclohexane dehydrogenation into catalytic dehydrogenation or oxidative dehydrogenation, homogeneous or heterogeneous reaction. Summarized vary catalysts, active constituent and process conditions in dehydrogenation process.

Abstract: This work makes thermodynamic analysis and optimization for the coal-based Fischer-Tropsch (FT) process. The thermodynamic analysis results show that under standard conditions the maximum effective carbon conversion is 50% from raw coal (CH_0.8O_0.1) to hydrocarbon products, and at least 50% carbon is converted into CO₂ emission in the coal-based FT process. Subsequently, a new coal-based FT synthesis process is proposed to get minimum water consumption, minimum wastewater emission and maximum energy efficiency. The process contains a pulverized coal gasification unit, water-gas-shift unit and iron-based FT synthesis unit with 50% CO₂ selectivity. The H₂/CO molar ratio of fresh syngas to the FT synthesis unit is 0.5. The carbon and water footprints analysis results indicate that the effective carbon conversion from raw coal to hydrocarbon products is about 46.0%, and it only consumes 0.102 molar water and generates 0.032 molar wastewater when converts 1 molar coal to hydrocarbon products in the process.

Abstract: Long adsorption band can result in negative effective adsorption capacity; in this paper, a calculation method for effective adsorption capacity is put forward for an adsorption band with fδ>L. A safety coefficient of adsorption capacity, g, was defined, which, it was proven, could be calculated out using the similarity law between the adsorption capacity-height distribution curve of a filler and the leakage-exhaustion curve of an adsorption column.

Abstract: In this paper, porous anodic aluminum oxide (AAO) membrane was prepared with highly pure aluminum film in 0.3M oxalic acid under dc voltage of 40V at about 8°C by two-step anodization. The morphology of the specimens processed in different stages of two-step anodization was observed with a scanning electron microscope (SEM). The electrochemical behavior of the anodized aluminum after different stages of two-step anodization was studied by electrochemical impedance spectroscopy (EIS). Different equivalent circuits were established to fit EIS experiment data, based on morphologies and structures of AAO during processing. The electrical elements in the equivalent circuits were used to explain experimental parameters.

Abstract: In order to probe CO₂-coal interactions, differential scanning calorimetry (DSC) experiment was carried out in the atmosphere of He and CO₂ with coals from Huozhou, Changzhi and Jincheng areas in Shanxi Province (classified as high-volatile bituminous coal, low-volatile bituminous coal and anthracite, respectively). It was found that, in a He atmosphere, all the three curves show no enthalpy and are almost reversible, indicating no adsorption occurs. However, in a CO₂ atmosphere, all the three curves show exothermic peaks and endothermic peaks and are irreversible, indicating, except for physical reactions, chemical reactions may also occur. It was proposed that the C atom of CO₂ accepted electrons from coal molecular, and formed an electron donor-acceptor complex (i.e., an EDA complex), in other words, chemical reactions occured, hence exothermic peaks occured. The interconnections of the active sites to other groups in coal molecular are weakened due to the formation of EDA complexes, so easily to be broken during heating, hence endothermic peaks occured. The irreversibility of the curves indicate structure change of coal, which may be influenced by two factors: a) during slow cooling, the ordering of side chains, which were expanded in high temperature, leads to a less associated structure; b) in heating process, the breakage of side chains enhances the associations of coal macromolecular, and leads to a more highly associated structure.

Abstract: Phosphate buffer solution (PBS) was exposed for different times to static magnetic field (MF) generated from six neodymium magnet (B=250mT) at flow conditions. The PBS conductivity and DO were measured as a function of time following the application of MF. It was found that the MF increases the PBS conductivity, and decreases the DO; they all have largest effect at the flow rate of 3m/s. Besides electrochemical reasons, this maybe can explains why the MFC have good performance by exposure to MF.

Abstract: A core-shell structure RuRh@Pt/C nanoparticles was prepared by using a two-step reduction method under ultrasonic promotion. The catalytic performance was tested in methanol electrooxidation. X-ray diffraction (XRD), scanning electron microscope (SEM) combined with cyclic voltammetry (CV) were used to characterize the obtained catalyst. The results showed that there was no alloy formed between the core RuRh and the shell Pt. The electrocatalytic activity of RuRh@Pt/C varied with the Ru/Rh ratio in the bimetallic core, among which the catalyst with the Ru/Rh ratio 1:2 and the Pt-shell thickness of 1.5 (Ru1Rh2@Pt1.5/C) showed the highest catalytic activity for methanol. With this catalyst, the current density of the oxidation peak for methanol electro-oxidation reached 2.3 times as that of Pt1.5/C while the corresponding peak potential shifted 60 mV negatively in comparing to that of Pt1.5/C. In addition, the catalyst with the core-shell structure of RuRh@Pt/C possessed much higher CO-tolerance for methanol electro-oxidation, indicating its promising application in low temperature fuel cell.

Abstract: The effect of molecular sieve, activated carbon, and nickel-based catalyst on oxidation of Ruqigou coal with NaOCl was investigated. The yields of diethyl ether-soluble fractions from reaction mixture are 67.3% for black test, 71.2% for molecular sieve, 68.6% for activated carbon and 70.3% for nickel-based catalyst, respectively. The results indicate that molecular sieve, nickel-based catalyst and activated carbon can all improve the oxidation reactivity of coal in aqueous NaOCl solution. Molecular sieve and nickel-based catalyst can convert most of the organic matters contained in coal into solvent-soluble species. The catalysis of molecular sieve is the highest, followed by nickel-based catalyst, activated carbon is relatively small.