A paraffin-fueled SOFC system design and integration

This paper addresses an integrated design of paraffin-reformer, gas separations and the electricity production with a solid oxide fuel cell (SOFC). The overall design consists of three modules. First module is a system of paraffin reformer. In this module, the paraffin feed stream is to send to a steam-reformer. In the second module, the gas separations method illustrated is the combination of a methane-permeable membrane with a pressure-swing adsorption (PSA). In the third module, the purified hydrogen is fed to the SOFC unit. To be energy efficient, this paraffin-fueled SOFC system is designed with the consideration of heat integration. The intent of this paper is to provide a possible, alternative way of cogeneration systems for refinery and petrochemical plants.     

Effect of dopants on the performance of CuO–CeO2 catalysts in methanol steam reforming

Steam reforming of methanol was carried out over a series of doped CuO–CeO₂ catalysts prepared via the urea–nitrate combustion method. XRD analysis showed that at least part of the dopant cations enter the ceria lattice. The addition of various metal oxide dopants in the catalyst composition affected in a different way the catalytic performance towards H₂ production. Small amounts of oxides of Sm and Zn improved the performance of CuO–CeO₂, while further addition of these oxides caused a decrease in catalyst activity. XPS analysis of Zn- and Sm-doped catalysts showed that increase of dopant loading leads to surface segregation of the dopant and decrease of copper oxide dispersion. The addition of oxides of La, Zr, Mg, Gd, Y or Ca lowered or had no effect on catalytic activity, but led to less CO in the reaction products. Noble-metal modified catalysts had slightly higher activity, but the CO selectivity was also significantly higher.     

Generating hydrogen-rich fuel-cell feeds from dimethyl ether (DME) using physical mixtures of a commercial Cu/Zn/Al2O3 catalyst and several solid–acid catalysts

Homogeneous physical mixtures containing a commercial Cu/ZnO/Al₂O₃ catalyst and a solid–acid catalyst were used to examine the acidity effects on dimethyl ether hydrolysis and their subsequent effects on dimethyl ether steam reforming (DME-SR). The acid catalysts used were zeolites Y [Si/Al = 2.5 and 15: denoted Y(Si/Al)], ZSM-5 [Si/Al = 15, 25, 40, and 140: denoted Z(Si/Al)] and other conventional catalyst supports (ZrO₂, and γ-Al₂O₃). The homogeneous physical mixtures contained equal amounts, by volume, of the solid–acid catalyst and the commercial Cu/ZnO/Al₂O₃ catalyst (BASF K3-110, denoted as K3). The steam reforming of dimethyl ether was carried out in an isothermal packed-bed reactor at ambient pressure.

The most promising physical mixtures for the low-temperature production of hydrogen from DME contained ZSM-5 as the solid–acid catalyst, with hydrogen yields exceeding 90% (T = 275 °C, S/C = 1.5, τ = 1.0 s and P = 0.78 atm) and hydrogen selectivities exceeding 94%, comparable to those observed for methanol steam reforming (MeOH-SR) over BASF K3-110, with values equaling 95% and 99%, respectively (T = 225 °C, S/C = 1.0, τ = 1.0 s and P = 0.78 atm). Large production rates of hydrogen were directly related to the type of acid catalyst used. The hydrogen production activity trend as a function of physical mixture was

     

多孔介质模型在核电蒸汽发生器设计中的应用

对基于多孔介质模型开发的核电蒸汽发生器三维热工水力分析程序ATHOS进行介绍．并应用ATHOS对核电蒸汽发生器二次侧的复杂传热传质现象进行数值模拟。获得蒸汽发生器二次侧的流动换热状态,以及二次侧三维两相流场分布,分析结果可作为传热管流致振动、磨损分析及结构设计的输入数据。研究工作表明,多孔介质模型在核电蒸汽发生器设计中具有重要的应用价值。     

Steam gasification of an australian bituminous coal in a fluidized bed

To produce low calorific value gas, Australian coal has been gasified with air and steam in a fluidized bed reactor (0.1 m-I.Dx1.6 m-high) at atmospheric pressure. The effects of fluidizing gas velocity (2–5 U_f/U_mf), reaction temperature (750–900 °C), air/coal ratio (1.6-3.2), and steam/coal ratio (0.63–1.26) on gas composition, gas yield, gas calorific value of the product gas and carbon conversion have been determined. The calorific value and yield of the product gas, cold gas efficiency, and carbon conversion increase with increasing fluidization gas velocity and reaction temperature. With increasing air/coal ratio, carbon conversion, cold gas efficiency and yield of the product gas increase, but the calorific value of the product gas decreases. When steam/coal ratio is increased, cold gas efficiency, yield and calorific value of the product gas increase, but carbon conversion is little changed. Unburned carbon fraction of cyclone fine decreases with increasing fluidization gas velocity, reaction temperature and air/coal ratio, but is nearly constant with increasing steam/coal ratio. Overall carbon conversion decreases with increasing fluidization velocity and air/ coal ratio, but increases with increasing reaction temperature. The particle entrainment rate increases with increasing fluidization velocity, but decreases with increasing reaction temperature. This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University.     

Squash leaf glandular trichome volatiles: Identification and influence on behavior of female pickleworm moth [Diaphania nitidalis (Stoll.)] (Lepidoptera: Pyralidae)

Fourteen volatile compounds occurring in leaf trichomes of yellow squash (Cucurbita pepo L. cv. Early Prolific Straightneck) were identified. These compounds accounted for 83.5% of the volatile matrix. Ubiquitous constituents of the epidermis (myristic, palmitic, and stearic acids,n-tricosane, andn-pentacosane) accounted for 73.7%; these compounds were not bioassayed. The volatileso-,m-, andp-xylene, toluene, 2-heptanone, (R)-(+)- and (S)-(–)-limonene, and germacrene D were tested for their influence on attraction and oviposition by the pickleworm moth (Diaphania nitidalis Stoll.). No single compound, except germacrene D, was attractive. (R)-(+)-Limonene and 2-heptanone were weakly repellent. Mixtures of the highly volatile fractions were as attractive as volatiles emanating from whole, intact leaves. Oviposition levels on treated artificial sites corresponded with levels of visitation. Oviposition was significantly stimulated by whole-leaf volatiles, and (S)-(–)-limonene caused a slight but significant reduction.Mention of a trade name or proprietary product does not constitute a warranty or guarantee by the U.S. Department of Agriculture, nor does it imply exclusion of other products that may also be suitable.     

Reforming of methane and coalbed methane over nanocomposite Ni/ZrO2 catalyst

Nanocomposite Ni/ZrO₂-AN catalyst consisting of comparably sized Ni metal and ZrO₂ nanoparticles is studied in comparison with zirconia- and alumina-supported Ni catalysts (Ni/ZrO₂-CP and commercial Ni/Al₂O₃-C) for steam reforming of methane (SRM) and for combined steam and CO₂ reforming of methane (CSCRM). The reactions are performed under atmospheric pressure with stoichiometric amounts of H₂O and CH₄ or (H₂O + CO₂) and CH₄ at 1073 K. Under a wide range of methane space velocity (gas hourly space velocity of methane GHSV_CH4 = 12,000–96,000 ml/(h g_cat.), the nanocomposite Ni/ZrO₂-AN catalyst always shows higher activity and stability for both SRM and CSCRM reactions. The two supported Ni catalysts (Ni/ZrO₂-CP and Ni/Al₂O₃-C) exhibit fairly stable catalysis under low GHSV_CH4 but they are easily deactivated under high GHSV_CH4 and become completely inactive when they are reacted for ca.100 h at GHSV_CH4 = 48,000 ml/(h g_cat.). The CSCRM reaction is carried out with different H₂O/CO₂ ratios in the reaction feed while keeping the molar ratio (H₂O + CO₂)/CH₄ = 1.0, the results prove that the nanocomposite Ni/ZrO₂-AN catalyst can be highly promising in enabling a catalytic technology for the production of syngas with flexible H₂/CO ratios (ca. H₂/CO = 1.0–3.0) to meet the requirements of various downstream chemical syntheses.     

Effect of incipient removal of hydrogen through palladium membrane on the conversion of methane steam reforming: Experimental and modeling

This paper presents a mathematical model based on the reaction rate expressions to describe the displacement of methane conversion in the steam reforming. The effect of several parameters including weight hourly space velocity (WHSV), load-to-surface ratio, reaction pressure, hydrogen partial pressure in permeate side and reaction temperature were investigated. Simulation and experimental results showed that a conversion higher than 80% could be achieved in a palladium membrane reactor at reaction temperature of 500 °C relative to 850 °C in a conventional fixed bed reactor (FBR). Besides, the yield of CO (<2%) in membrane reactor was much lower than that (>50%) in the FBR, which indicated the significant depression of CO production in use of membrane reactor.     

Effects of microreactor wall heat conduction on the reforming process of methane

In this paper, the effect of wall conduction of an autothermal tubular methane microreformer is investigated numerically. It is found that the axial wall conduction can strongly influence the performance of the microreactor and should not be neglected without a careful a priori investigation of its impact. By increasing the wall thermal conductivity, the maximum wall surface temperature is decreased. Due to the complex exothermic–endothermic nature of the chemistry of reforming, the axial variation of the wall temperature is not monotonic. Methane conversion and hydrogen yield are strongly dependent on the wall inner surface temperature, hence the heat conduction through the channel wall. The equivalence ratio and the wall thickness also significantly affect the reforming effectiveness and must be carefully considered in reactor optimization. Furthermore, it is found that exothermic oxidation reaction mechanisms, especially partial oxidation, are responsible for syngas (hydrogen and carbon monoxide) production near the inlet. Farther downstream, in the oxygen deficient region, endothermic steam reforming is the main hydrogen producing mechanism. By increasing the thermal conductivity, steam reforming becomes stronger and partial oxidation becomes weaker. For all investigated inlet conditions, the highest hydrogen yield is obtained for no or very low conductive walls.     

干燥机的最新发展(二)

本文论述了以过热水蒸汽作为干燥介质代替热风的干燥新技术的原理、优越性、存在的问题以及发展前景，并对微波对流干燥器的原理、特点等作了描述。