Techno-economic analysis of green hydrogen production from biogas autothermal reforming

The development and deployment of energy mix hydrogen production technologies, and the prospect of supplying “green” hydrogen to fuel-cell cars are expected to play significant roles in the near future. The sustainability of the process is a key enabler for a hydrogen-including economy. A techno-economic analysis of the BioRobur technology, which involves the green hydrogen production of 100 N m³ H₂/h (5.0 grade), has been performed in this study to provide a basis for comparison between the final cost of the hydrogen and the European target. Moreover, a technology for its eventual implementation has been addressed, in which the weakness and strengths have been identified by means of a SWOT analysis. The cost and supply analysis of this biogas-to-hydrogen production system, via autothermal reforming, indicates that municipal solid waste (MSW) is an important source of the low-cost supply of biogas-derived hydrogen. As far as the market potential is concerned, this analysis suggests that MSW can provide about 286,607 kg/day at 5 €/kg H₂ (delivery cost). Additionally, after 10 years of amortization, the final cost to produce 100 N m³/h of H₂ would be 2.5 €/kg, which is far lower than the European target for the cost of obtaining H₂ through biogas reforming, that is, 5 €/kg of H₂.     

Aqueous phase reforming of glycerol over Ni-based catalysts for hydrogen production

Aqueous phase reforming of glycerol over Ni-based catalysts for hydrogen production was carried out at 225 degrees C, 23 bar and LHSV = 4 h(-1). The Ni-based catalyst was prepared by an incipient wetness impregnation method. The catalysts before and after the reaction were characterized by N2 physisorption, CO chemisorption, XRD, TPR, SEM and TEM techniques. It was found that Ni(20 wt%)-Co(3 wt%)/gamma-Al2O3 catalyst showed higher glycerol conversion and hydrogen selectivity than Ni(20 wt%)/gamma-Al2O3 catalyst. There are no major changes in Ni particles after the reaction over Ni-Co/gamma-Al2O3 catalyst. The results suggest that the Ni-Co/gamma-Al2O3 catalyst can be applied to the hydrogen production system using APR of glycerol.     

Physical and photo-electrochemical properties of the spinel SrFe2O4: application to hydrogen production under visible light

Journal of Materials Science: Materials in Electronics - SrFe2O4 prepared by sol–gel method after annealing at 800 °C crystallizes in a normal spinel structure. The structural,...     

PdZn/ZrO2催化剂上二甲醚低温蒸汽重整制氢

采用溶胶-凝胶法制备ZrO2载体,然后采用沉积沉淀法制备一系列PdZn/ZrO2重整催化剂,对其进行BET、XRD的分析;并将其与水解催化剂(m(ZSM-5)∶m(γ-Al2O3)=2∶1)复合用于二甲醚蒸汽重整反应.考察了载体焙烧温度、表面活性剂、活性组分负载顺序和催化剂的装填方式对重整反应性能的影响.研究结果表明,以500℃焙烧,加入表面活性剂及PdZn共同负载制备的PdZn/ZrO2重整催化剂和水解催化剂机械混合组成的复合催化剂显示出较好的活性和较高的选择性,H2收率可达56.1％,CO2选择性为90.2％.     

Syngas production employing nickel on alumina-magnesia supported catalyst via dry methane reforming

Nickel supported on alumina-magnesia bimetallic oxide support (Ni/Al₂O₃-MgO) nano-catalysts were prepared by the co-precipitation followed by impregnation (two steps) method separately and tested for the dry methane reforming. The optimum bimetallic oxide catalyst support ratio (i. e., alumina: magnesia) is tested and it has been found that alumina:magnesia ratio of 1 : 2 showed the most stable results. The effect of nickel loading has been studied by impregnating the bimetallic oxide support with nickel as 10 wt.%, 12 wt.%, 14 wt.%, and 16 wt.%. It has been found that the catalyst containing 12 wt.% nickel showed the best activity in terms of methane (CH₄) and carbon dioxide (CO₂) percentage conversions, syngas (H₂:CO) ratio, lowest coke formation and stability for dry methane reforming at 800 °C, 1 atm and methane: carbon dioxide ratio of unity. The Brunauer-Emmett-Teller surface area and pore size analysis of fresh catalyst has been carried out. The x-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray and elemental mapping analysis for fresh and spent catalysts has been obtained confirming the coke formation during the reaction.     

Improved optical and electrical characteristics of free-standing GaN substrates by chemical polishing utilizing photo-electrochemical method

The optical and electrical properties of GaN(0001) surfaces treated by a novel chemical polishing method are described. Scanning microscopic photoluminescence images reveal that the polished GaN surface shows improved luminescence properties compared to the untreated surface. Current-voltage measurements of Schottky barriers formed using the GaN substrates show that the polished GaN surface has a lower reverse leakage current, and that the barrier height and ideality factor are improved after the polishing treatment.     

Sustainable hydrogen production system with sulfur–water–organic materials by hydrothermal reaction

Engineered process for hydrogen generation from hydrogen sulfide ions in aqueous solution using solar energy with photocatalysis has been established. In order to design a complete closed loop of hydrogen production system, reacted sulfide ions have to be reduced to photocatalysis-active hydrogen sulfide ion. We focused on hydrothermal reaction of sulfur for reducing the reacted sulfide ions. But the oxidized sulfur species are occurred inevitably by the reaction. Thus alternative reducers are required to sulfur hydrothermal reaction for a complete closed loop of hydrogen production system. We studied sulfur–water–organic materials interaction, and particularly on the effective utilization of waste elemental sulfur. In this study, hydrothermal experiments of sulfur, water urea, and/or alcohols were carried out under atmospheric constituent condition and hypoxic condition at 200 °C. Experimental results show that maintaining solution in weak alkaline condition is important and alcohol compounds had a great role for reduction of sulfur. Elemental sulfur was completely reduced to hydrogen sulfide by the hydrothermal reaction of sulfur with urea and propanol under hypoxic condition. Those results indicate that it is possible to create sustainable sulfur cycle for hydrogen production system using hydrothermal reaction with organic compounds.     

Exergy efficiency improvement in hydrogen production process by recovery of chemical energy versus thermal energy

Exergy analysis is recently being employed as one of the preferred methods to improve the design performance of a system and to achieve overall sustainability. Exergy is mainly composed of physical or thermo-mechanical and chemical components and a single stream can possess one or more forms of exergy. Where there is exergy lost in unused chemical streams or wasted energy, the recovery of exergy would reduce losses and increase the second law efficiency of the process. In many chemical process plants such as hydrogen (H₂), ammonia, nitric acid, etc., there is a potential to recover waste or excess heat by process heat exchange or by generating utilities. For a process like steam–methane (CH₄) reforming (SMR), exergy efficiency can be improved by recovering the available excess heat partially or fully in the form of chemical energy or thermal energy. This paper presents the generalised system analysis to show that the recovery of exergy in the form of chemical energy is better than in thermal energy form due to fewer losses and higher efficiency. The concept is illustrated with the example of a simple combustion system with excess heat in which saving fuel proves to be more exergy efficient than generating utility. The approach is applied to an industrial case study of H₂-producing SMR plant with two modified cases of steam generation and recycling portion of unconverted CH₄ as feed. In the case study, heat exchanger network is treated as a separate process component and a simple methodology is proposed to calculate the exergy losses for the same. The results of the case study prove that the recovery of chemical energy is more efficient than that of thermal energy from an exergy perspective.     

Inorganic nanofibers with tailored placement of nanocatalysts for hydrogen production via alkaline hydrolysis of glucose

Monoaxial silica nanofibers containing iron species as well as coaxial nanofibers with a pure silica core and a silica shell containing high concentrations of iron nanocrystals were fabricated via electrospinning precursor solutions, followed by thermal treatment. Tetraethyl-orthosilicate (TEOS) and iron nitrate (Fe(NO(3))(3)) were used as the precursors for the silica and iron phases, respectively. Thermal treatments of as-spun precursor fibers were applied to generate nanocrystals of iron with various oxidation states (pure iron and hematite). Scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to probe the fiber morphology and crystal structures. The results indicated that the size, phase, and placement of iron nanocrystals can be tuned by varying the precursor concentration, thermal treatment conditions, and processing scheme. The resulting nanofiber/metal systems obtained via both monoaxial and coaxial electrospinning were applied as catalysts to the alkaline hydrolysis of glucose for the production of fuel gas. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and bulk weight change in a furnace with residual gas analysis (RGA) were used to evaluate the performance of the catalysts for various ratios of both Fe to Si, and catalyst to glucose, and the oxidation state of the iron nanocrystals. The product gas is composed of mostly H(2) (>96 mol%) and CH(4) with very low concentrations of CO(2) and CO. Due to the clear separation of reaction temperature for H(2) and CH(4) production, pure hydrogen can be obtained at low reaction temperatures. Our coaxial approach demonstrates that placing the iron species selectively near the fiber surface can lead to two to three fold reduction in catalytic consumption compared to the monoaxial fibers with uniform distribution of catalysts.     

Steam reforming of glycerol into hydrogen over nano-size Ni-based hydrotalcite-like catalysts

Steam reforming (SR) of glycerol for the production of hydrogen was investigated over the nano-sized Ni-based catalysts. The Ni-based catalysts were prepared by solid phase crystallization and impregnation methods, and characterized by N2 physisorption, CO chemisorption, XRD, SEM, and TEM techniques. The Ni/gamma-Al2O3 catalyst showed higher conversion and H2 selectivity. However, it was slowly deactivated due to the carbon formation on the surface of catalyst and the sintering. It was found that the Ni based hydrotalcite-like catalyst (spc-Ni/MgAl) showed higher catalytic activity to prevent carbon formation than Ni/gamma-Al2O3 catalyst in the SR of glycerol.     

Investigation of the explosive hazard of mixtures containing hydrogen peroxide and different alcohols

The explosive properties of mixtures of aqueous hydrogen peroxide (H(2)O(2)) and different alcohols (R-OH) like 2-propanol (2-PropOH), 2-methyl-2-propanol (TBA), 2-methyl-2-butanol (TAA) and 2-methyl-2-pentanol (THA) were investigated. Among others, the potential hazard of such mixtures may be characterized by their ability to react by different mechanisms of an explosion in the condensed phase, e.g. the thermal explosion or the detonation. Accordingly, the mixtures were experimentally investigated either by heating them up under confinement in different autoclaves or by exposing them to a shock wave impact applying the steel tube test. The results are discussed and compared to literature data.     

煤油水重整制氢催化剂的优化设计

以Ni为活性组分,稀土元素La,碱金属Li和贵金属Pt为助剂完成了催化剂体系设计;采用等体积分步浸渍法和溶胶凝胶法制备催化剂。考察了助剂La,Li和Pt的作用,研究了催化剂的活性、稳定性和抗析碳性,并筛选催化剂。研究了NiLaLiPt/γ-Al2O3催化剂上煤油水重整制氢的影响因素。     

Nanorod alumina-supported Ni-Zr-Fe/Al2O3 catalysts for hydrogen production in auto-thermal reforming of ethanol

Nanorod alumina-supported Ni-Zr-Fe/Al₂O₃ catalysts were prepared by co-impregnation, characterized by TEM, TPR, XRD, XPS, and TPD-pyridine, and tested in auto-thermal reforming of ethanol. The characterization results indicate that, with iron and zirconia promotion, the Ni_xFe_1−xAl₂O₄ mixture spinel forms, the valence of the surface Ni species is modified, and the acidity decreases. As a result, during a 30-h test over the Ni-Zr-Fe/Al₂O₃ catalyst, sintering is restrained, and the selectivity to hydrogen remains around 85.79% without obvious loss, while the un-promoted Ni/Al₂O₃ shows poor stability and selectivity.     

Effect of hydrogen bonding on the viscosity of alcohols at high pressures

Viscosities of several alcohols and vinyl acetate were measured with a rollingball viscometer. The viscosity measurements were performed at temperatures from 298 to 413 K and pressures up to 195 MPa with an accuracy of ±2%. The viscosities of the alcohols show a stronger dependence on temperature compared with that of substances that do not form hydrogen bonds. In addition, the secondary and tertiary alcohols show a viscosity-temperature dependence not in accordance with an Arrhenius law. An effect of pressure on the association of alcohol molecules resulting from hydrogen bonding was not resolved by means of viscosity data. Separation of the effect of association size upon increasing temperature from the viscosity caused by the change of specific volume was carried out using the Utracki free volume model.     

Bi_(25)FeO_(40)纳米材料的水热制备及光电性能研究

通过水热法在钛基板上成功制备出了不同形貌的Bi25FeO40纳米材料,使用XRD和FE-SEM对水热反应过程中反应的温度(160~200℃)、矿化剂的种类和浓度对产物结构及形貌的影响进行了研究,并对其生长机理进行分析。测试Bi25FeO40的UV-Vis漫反射光谱,发现其在波长400~600 nm范围内具有良好的可见光响应;采用三电极体系测试材料的光电化学性能,结果显示纳米棒状产物对光电流的响应最快。     

风光储制氢下多台制氢机组优化调度研究

以风光储制氢系统中多台制氢机组和储能电池的优化调度为研究对象,目标是制氢的经济效益最大化.根据调度对象和目标函数的特征分别采用改进时序差分算法(TDA)和多目标粒子群优化算法(MOPSO)进行优化调度,其中储能电池的调度起辅助作用,用来使风光出力曲线匹配制氢出力曲线.算例分析表明,文中所述改进时序差分算法在解决多台制氢...     

Improved solar energy conversion efficiencies for the photocatalytic production of hydrogen via TiO2 semiconductor electrodes

Overall solar energy conversion efficiencies of at least 0.8%, somewhat greater than those previously reported, have been obtained in the photocatalytic production of hydrogen using TiO₂ semiconductor electrodes prepared by heat-treatment of titanium metal foils. A shift in the threshold frequency for hydrogen evolution toward energies slightly lower than the 3.02 eV bandgap of TiO₂ has been observed for some of these electrodes. This result supports the possibility of utilizing a greater portion of the solar spectrum, thereby increasing overall conversion efficiency even further. A tentative explanation of this shift involves the presence of mixed phases of the titanium-oxygen system (Magneli phases) in the semiconducting film. An outline of the work in progress is given.