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801.
基于GM(1,1)模型的矿井瓦斯涌出量预测研究 总被引:5,自引:0,他引:5
应用灰色系统理论,建立了预测矿井瓦斯涌出量的灰色系统GM(1,1)模型,并用残差序列对预测模型进行了修正。实例表明,该模型的计算精度符合工程实际,可用于矿井瓦斯涌出量的预测。 相似文献
802.
《International Journal of Hydrogen Energy》2020,45(36):18226-18240
There is a growing interest in the usage of hydrogen as an environmentally cleaner form of energy for end users. However, hydrogen does not occur naturally and needs to be produced through energy intensive processes, such as steam reformation. In order to be truly renewable, hydrogen must be produced through processes that do not lead to direct or indirect carbon dioxide emissions. Dry reformation of methane is a route that consumes carbon dioxide to produce hydrogen. This work describes the production of hydrogen from biomass via anaerobic digestion of waste biomass and dry reformation of biogas. This process consumes carbon dioxide instead of releasing it and uses only renewable feed materials for hydrogen production. An end-to-end simulation of this process is developed primarily using Aspen HYSYS® and consists of steady state models for anaerobic digestion of biomass, dry reformation of biogas in a fixed-bed catalytic reactor containing Ni–Co/Al2O3 catalyst, and a custom-model for hydrogen separation using a hollow fibre membrane separator. A mixture-process variable design is used to simultaneously optimize feed composition and process conditions for the process. It is identified that if biogas containing 52 mol% methane, 38 mol% carbon dioxide, and 10 mol% water (or steam) is used for hydrogen production by dry reformation at a temperature of 837.5 °C and a pressure of 101.3 kPa; optimal values of 89.9% methane conversion, 99.99% carbon dioxide conversion and hydrogen selectivity 1.21 can be obtained. 相似文献
803.
《International Journal of Hydrogen Energy》2020,45(4):2794-2807
Hydrotalcite-derived Ni/Mg(Al)O is promising for CH4–CO2 reforming. However, the catalysts reported so far suffer from sever coking at low temperatures. In this work, we demonstrate that a significant improvement of coke-resistance of Ni/Mg(Al)O can be achieved by fine tuning the Ni particle size through adjusting the reduction condition of catalyst. Ni particles having average size within 4.0–7.1 nm are in situ generated by reducing the catalyst at a selected temperature within 923–1073 K. Controllability of Ni particle size is related to the formation of Mg(Ni,Al)O solid solution upon hydrotalcite decomposition. It is found that the catalyst reduced at 973 K exhibits high activity, stability, and coke-resistance even at reaction temperature as low as 773 K. In contrast, the catalyst reduced at 923 K has low activity and deactivates due to Ni oxidation, while those reduced at 1023 and 1073 K suffer from sintering and severe coking. STEM and O2-TPO reveal that coke deposition is directly proportional to the Ni particle size but becomes negligible at a size below 6.2 nm. It is evidenced that a critical size of about 6 nm is required to inhibit coking effectively. CO2 temperature-programmed surface reaction indicates that the deposited carbon on small Ni particles can be easily removed by the CO2 activated at the Ni–Mg(Al)O interfaces, accounting for the better resistance to coking. 相似文献
804.
《International Journal of Hydrogen Energy》2020,45(7):4490-4500
Al2O3 and MgAl2O4 supported 10% (w/w) Ni catalysts having a dispersion of 1.5 and 2.0% are active for DRM at 600 and 750 °C. High temperature reduction of both the calcined catalysts resulted in metallic Ni being formed, suggesting strong support metal interactions. The CH4 and CO2 conversion during DRM are relatively constant with time-on-stream, and are higher for Ni/MgAl2O4 than Ni/Al2O3. Carbon-whiskers are also detected on both catalysts. O2 co-feed of 2.6% (v/v) and increasing reaction temperature to 750 °C helped in decreasing the amount of carbon deposited, except for Ni/MgAl2O4 at 600 °C. Furthermore, higher conversions and H2/CO ratios are achieved. It appears that on spent Ni/MgAl2O4 a different type of carbon species was formed, and this carbon species was difficult to remove by oxygen at 600 °C. Thus, co-feeding O2, using an appropriate temperature, and choosing a suitable support can reduce the carbon present on the nickel catalysts during DRM. 相似文献
805.
《International Journal of Hydrogen Energy》2020,45(8):5297-5308
Nickel-free solid oxide fuel cell anodes are an object of study for applications that aim at utilising primary carbonaceous fuels to generate power. In this study, a ceria-Co-Cu anode is produced and tested with hydrogen, methane and ethanol fuels at various temperatures.The produced catalysts were characterised by X-ray analysis and H2 temperature-programmed reduction (TPR). Catalytic tests were performed and compared with the material under electrochemical operation. The cells were electrochemically characterised by recording i-V plots. The samples were assessed post-test for eventual carbon deposits by Raman spectroscopy investigations and temperature-programmed oxidation (TPO) analysis.The cells were able to operate with hydrogen, methane as well as ethanol, directly fed to the anode, with maximum power densities ranging from 400 to 540 mW.cm−2, depending on the fuel stream utilised. The cells also kept their integrity demonstrating coking resistance for over 24 h of continuous operation. Important discussions and conclusions are drawn about carbon formation and the role of each compound in the anode composition. The bimetallic cell (ceria-Co-Cu) is herein compared to monometallic ones (ceria-Co and ceria-Cu) that served as baselines. The advantages of the bimetallic composition are listed and evaluated throughout the discussions. 相似文献
806.
Zhongkui Zhao Panpan Ren Weizuo Li Boyuan Miao 《International Journal of Hydrogen Energy》2017,42(10):6598-6609
Supported Ni catalysts on ZrO2 towards steam-CO2 bi-reforming (SCBR) of methane for the production of synthesis gas were synthesized by the hydrothermal process with different mineralizers followed by l-arginine ligand-assisted incipient wetness impregnation (HT-LA-IWI) method. The effect of type and amount of mineralizers for preparing ZrO2 supports on the nature of supports and supported Ni catalysts, as well as on the catalytic properties and structure–performance relationship were investigated. Results show that the catalytic performance is strongly dependent on the morphology and textural of ZrO2 support notably affected by the type and amount of mineralizer. The supported Ni catalyst on the ZrO2 prepared by using sodium acetate (molar ratio of sodium acetate/zirconium, NSAc/Zr = 0.5) as mineralizer (Ni/ZrO2 (SAc0.5)) shows much higher catalytic activity than the one on ZrO2 prepared by using sodium carbonate (molar ratio of sodium carbonate/zirconium, NSC/Zr = 0.5) as a mineralizer (Ni/ZrO2 (SC0.5)), ascribed to higher Ni dispersion and smaller average crystallite size of Ni. With respect to both activity and stability, the sodium acetate can be selected as a suitable mineralizer for the preparation of excellent ZrO2 support. Furthermore, the increasing NSAc/Zr from 0.5 to 2.0 leads to an increase in surface area but a decrease in pore diameter and pore volume, which endows the Ni/ZrO2 (SAc2.0) catalyst with much larger average crystallite size of Ni but much worse Ni dispersion than Ni/ZrO2 (SAc0.5). As a result, Ni/ZrO2 (SAc2.0) shows much lower catalytic activity than Ni/ZrO2 (SAc0.5). Moreover, the Ni/ZrO2 (SAc2.0) catalyst shows worse Ni sintering resistance than Ni/ZrO2 (SAc0.5) owing to its weaker NiZrO2 interaction confirmed by H2-TPR results, which endows it with lower catalytic stability although it has higher coke deposition resistance. 相似文献
807.
Fethi Bouras Mohammed El Hadi Attia Fouad Khaldi Mohammed Si-Ameur 《International Journal of Hydrogen Energy》2017,42(13):8932-8939
This study presents a numerical investigation of the effects of mixing methane/hydrogen on turbulent combustion processes taking place in a burner similar to that integrated in gas turbine power plants. Thereby, in comparison to the reference case where the burner is fuelled by 100% of methane, the variations of the axial velocity field, temperature field and mass fraction of carbon monoxide field are examined for different percentages of hydrogen fuel injection. The computed results, obtained by using the software Fluent-CFD, are compared and validated against experimental reference data. Results show that the hydrogen addition to the methane has an impact on all physical and chemical parameters of the reactive system. 相似文献
808.
This study examined and elucidated the catalytic dry reforming of methane (DRM) for synthesis gas (syngas) production. The DRM performance was characterized using CH4 and CO2 conversions and product yields under various operating conditions and reactant compositions. A fixed-bed tubular reactor was used as the physical model and axisymmetric non-isothermal governing equations for the gas flow, energy transfer and species transport were solved numerically. The reactant inlet temperature was used as the primary parameter. Good agreement between the numerically predicted and experimentally measured data was obtained as the carbon formation reactions were included. A carbon-free reaction was obtained from the numerical model at high temperature which agreed with the thermodynamic equilibrium analysis. It was found that the DRM performance was degraded as the reaction pressure and reactant flow rate were increased. Under these conditions, carbon yield increases with the increase in pressure and reactant flow rate. It was also found that DRM performance can be enhanced by introducing excessive CO2 into the reaction system. Carbon formation was suppressed by the excessive CO2 supply. The numerical results also indicated that decreases in CO2 and CH4 partial pressures led to enhance the DRM performance. The addition of H2 as one of the reactants suppresses CH4 conversion and inhibited carbon formation while the addition of CO resulted in suppressing CO2 conversion and enhancing carbon formation. 相似文献
809.
Ali Rastegarpanah Fereshteh Meshkani Mehran Rezaei 《International Journal of Hydrogen Energy》2017,42(26):16476-16488
Thermocatalytic decomposition of CH4 is an interesting method for the production of hydrogen. In this article, the catalytic and structural properties of the La, Ce, Co, Fe, and Cu-promoted Ni/MgO·Al2O3 catalysts were investigated in the thermal decomposition of CH4. Mesoporous MgO·Al2O3 powder with the high BET area (>250 m2/g) was synthesized by a novel and simple sol–gel method. The different instrumental methods (XRD, BET, SEM, H2-TPR and TPO) were used for evaluating the physicochemical characteristics of the samples. The addition of Cu to Ni/MgO·Al2O3 dramatically improved the catalytic performance and the Cu-promoted catalysts exhibited the highest CH4 conversion and H2 yields among the promoted and unpromoted catalysts. The Cu-promoted catalyst possessed the highest stability in CH4 conversion during 10 h of reaction. The results also indicated that the Ni–Cu/MgO·Al2O3 catalyst with 15 wt.% Cu showed the highest catalytic activity and stability at higher temperatures (>80% CH4 conversion). 相似文献
810.
Xinhua Gao Guoguo Liu Qinhong Wei Guohui Yang Mitsunori Masaki Xiaobo Peng Ruiqin Yang Noritatsu Tsubaki 《International Journal of Hydrogen Energy》2017,42(26):16547-16556
A silicon carbide (SiC) foam monolith decorated with a carbon nanofibers (CNFs) layer was employed as the catalyst support for Ni-based catalyst preparation, used for the CO2 dry reforming of methane (DRM) reaction. The loading amount of CNFs on the SiC foam monolith was 6.6 wt.%, which obviously increased the surface area of the pristine SiC foam from 4 m2/g to 24 m2/g. The prepared CNFs layer strongly attached to the pristine SiC surface and was considerably stable even after 100 h time on stream (TOS) DRM reaction. The CNFs decorated SiC composite support provided more anchorage sites for improving the dispersion of the Ni particles and enhanced the metal-support interaction compared to the pristine SiC support. Compared with other catalysts such as Ni/SiC and Ni/CNFs, the Ni/CNFs-SiC catalyst exhibited not only the highest activity but also remarkable stability during DRM reaction. The XPS and SEM-EDS results showed that the carbon deposition over the nickel surface of Ni/CNFs-SiC catalyst was much less than those of Ni/SiC and Ni/CNFs catalysts. In addition, the XRD analysis verified that almost no sintering of nickel particle was detected over the Ni/CNFs-SiC catalyst, which was prepared with CNFs-SiC composite as catalyst support, even after 100 h TOS DRM reaction at 750 °C. 相似文献