Four different configurations of a 5 kW class shell-and-tube methane steam reformer with a low-temperature heat source

The methane steam reforming reaction is an extremely high endothermic reaction that needs a high temperature heat source. Various fuel cell hybrid systems have been developed to improve the thermal efficiency of the entire system. This paper presents a low temperature steam reformer for those hybrid systems to maximize the utilization of energy from a low temperature waste heat source. In this study, the steam reformer has a shell and tube configuration that is divided into the following zones: the inlet heat exchanging zone, the reforming zone and the exit heat exchanging zone. Four different configurations for methane steam reformers are developed to examine the effect of heat transfer on the methane conversion performance of the low temperature steam reformer. The experimental results show that the overall heat transfer area is a critical parameter in achieving a high methane conversion rate. When the heat transfer area increases about 30%, the results showed elevated dry mole fractions of hydrogen about 3% with about 30 °C rise of reformer outlet temperature.     

Facile Proton Transport in Ammonium Borosulfate—An Unhumidified Solid Acid Polyelectrolyte for Intermediate Temperatures

High proton conductivity is reported for unhumidified ammonium borosulfate, NH₄[B(SO₄)₂], a solid acid coordination polymer that contains 1D, hydrogen-bonded NH₄⁺···¹_∞[B(SO₄)_4/2]⁻ chains. NH₄[B(SO₄)₂] is thermally stable to 320 °C and is amenable to sintering into monolithic, polycrystalline discs at 200 °C and about 300 MPa of uniaxial pressure. Impedance spectroscopy measurements reveal ionic conductivities for sintered ammonium borosulfate of 0.1 mS cm⁻¹ at 25 °C and up to 10 mS cm⁻¹ at 180 °C in ambient air. No superprotonic transition is observed in the temperature range of 25–180 °C. Ab initio molecular dynamics simulations show these high conductivities are aided by free rotation of the NH₄⁺ units and significant gyrational mobility of the SO₄ tetrahedra, which, in turn, provide facile pathways for proton locomotion. High conductivities, a wide operational temperature window, and tolerance to both ambient and anhydrous conditions make NH₄[B(SO₄)]₂ an attractive candidate electrolyte for intermediate-temperature hydrogen fuel cells that may enable operation at temperatures as high as 300 °C without active humidification.     

Structure,nonlinearity, and system theory

The suggestion of writing, for some problems, nonlinear state equations not as dx/dt = F(x,u,t), but as dx/dt = [A(t,x)]x + [B(t,x)]u(t), which is more ‘constructive’ as re system perception and possible structural generalizations, is considered, supported by arguments related to the classification of switched circuits as linear and nonlinear. The point of the distinction is mainly that when solving dx/dt = F(x,u,t), one immediately dwells into the analytical problems related to pure mathematics, whereas for dx/dt = [A(t,x)]x + [B(t,x)]u(t), considering first a constant matrix [A], one introduces the system's physical structure and considering then [A(x)] sees the nonlinearity of the system as a dependence of the structure on the processes in it or on system's input. (This might be named structural response). The thinking in terms of structure better observes the engineering and physical degrees of freedom, which are relevant regarding applications. Some electronic systems and physical systems (e.g., hydrodynamic) are considered in these terms. The logical side is always the focus, and the pedagogical (even philosophical) side is not ignored. Copyright © 2013 John Wiley & Sons, Ltd.     

Characterisation of coarse composite sphalerite particles with respect to flotation

The flotation response of a typical zinc-lead (Zn/Pb) ore, with respect to coarse composite (sulphide/non-sulphide) particles is reported. The flotation tests were carried out on a selected feed particle size range (−600 + 75 μm, at P₈₀ of 390 μm) and the recovery of Zn composite particles analysed on a size by size basis. The best results were achieved with the use of 75 g/t sodium isopropyl xanthate (SIPX), obtaining a Zn recovery of 77%, with a significant improvement at the coarse end of the particle size distribution. Computerised scanning electron microscope (QEMSCAN) was used to characterise value mineral grain size and degree of liberation, as well as gangue and sphalerite association in particles reporting to both concentrate and tailings. A new characterisation function (Locking ratio, LR) was developed based on the data from the automated mineralogical analysis to characterise particles into two-phase composites with different degree of locking texture (simple and complex). The function, which is based on the mode of occurrence of sphalerite, grain size, proportion and composition of the constituent minerals in each particle, was used to study the flotation response of the particles with different degrees of locking. The results highlight the difference in recoverability of the sphalerite bearing particles with different degrees of locking, with simple locking texture giving higher recovery than complex locking texture, for the same overall liberation.     

A Critical Review of Biological Processes and Technologies for Landfill Leachate Treatment

The most common method to deal with the huge production of municipal wastes is still the disposal in landfills which, however, generates a leachate with high contents of organic and nitrogen pollutants. Requirements must be fixed by law to control leachate release from such landfills, and effective treatment processes and technologies must be applied to reduce its impact on the environment. Biological processes for leachate treatment are discussed in this review, in the former part of which attention is paid to leachate formation and its qualitative and quantitative features, while the latter deals with the state‐of‐the‐art of the most effective biotechnological treatments presently employed. Processes, alternative methods, and technological improvements are compared, with special focus on novel technologies to remove nitrogen pollutants from leachate, highlighting advantages and drawbacks of each treatment.     

Multi-criteria decision-making approach assisting to select materials for low-temperature solid oxide fuel cell: Electrolyte,cathode& anode

Solid Oxide Fuel Cells (SOFCs) have been emerged as a viable technology to convert chemical energy of fuels to electrical energy efficiently and environmentally friendly. However, some issues hinder the successful implementation of SOFC in industrial scales, such as elevated operating temperature, electrochemical stability, high costs associated with materials and interconnectors. To facilitate SOFCs commercialization, Low Temperature-SOFC (LT-SOFC) technology has been introduced. Various materials for core components of the LT-SOFC have been suggested and their performances are investigated. However, operating LT-SOFC faces challenges such as low ionic conductivity of electrolytes and slow rate of the oxygen reduction reaction. These obstacles can be overcome by selecting appropriate alternative materials that can conduct tasks preferably. Since assessing choices demands multiple measures, conducting a multi-criteria decision-making approach is inevitable. In this study, the Analytical Hierarchy Process is used to evaluate criteria and different options as alternatives for the main constituents of an LT-SOFC.     

Strengthening Mechanism and Microstructure of Deformable Ti Particles Reinforced AZ91 Composite

In this study, the deformable titanium (Ti) particles reinforced AZ91 composite was successfully prepared by powder metallurgy and subsequent extrusion. The mechanical properties and microstructural evolution of pure AZ91 and 5Ti/AZ91 composite were studied. The yield strength, ultimate tensile strength, and elongation of 5Ti/AZ91 composite are measured to be 212 MPa, 323 MPa, and 10.1%, respectively. Microstructure analysis revealed that Ti particles are elongated along the extrusion direction, forming a discontinuous strip Ti particles, fine precipitated Mg₁₇Al₁₂ phase inhibits dynamic recrystallization (DRX) behavior through Zener pinning effect and hinders the growth of matrix grains, resulting in refiner grains of 5Ti/AZ91 composite. Heterogeneous deformed Ti particles and magnesium (Mg) matrix to generate additional heterogeneous deformation-induced (HDI) strengthening. Heterogeneous deformation-induced strengthening mainly contributed to the increment of yield strength for 5Ti/AZ91 composite.     

Preparation and Applications of Chiral Polymeric Particles

Chiral polymeric particles (CPPs) have been gathering increasing interest as typical functional polymeric particles in recent decades. This article presents a review on the preparation and applications of CPPs. The methods for preparing CPPs are classified into two major groups: The first one is the direct polymerization of monomers and the other is the post-treatment of preformed polymers. CPPs have been explored as a unique type of chiral materials in various fields like asymmetric catalysis, enantioselective release, enantioselective crystallization, and enantioseparation. This review article is expected to accelerate the progress of scientific research dealing with CPPs and their applications in chirality-related fields.     

A novel approach to fabricate porous alumina ceramics with excellent properties via pore-forming agent combined with sol impregnation technique

An innovative approach for fabricating porous alumina ceramics (PACs) with improved mechanical and thermal properties using walnut shell powders as pore-forming agent combined with alumina sol impregnation is reported in the present work. It is demonstrated that uniform distribution of spherical pores can be observed in as-prepared PACs by using above technical route. The decrease of walnut shell powder sizes significantly promotes the enhancement of crushing strength and reduction of thermal conductivity of the PACs. Meanwhile, the impregnated alumina sol is favoring for the formation of spherical micro-pores, then further improves their mechanical and thermal insulation performances. The lowest thermal conductivity and highest crushing strength of resulting sample reach 0.16?W/m?K and 29.2?MPa, respectively. This novel method offers new possibilities to fabricate high-quality PACs.     

Calorimetric study of ytterbium orthovanadate YbVO4 polycrystalline ceramics

The heat capacity of ytterbium orthovanadate was first measured by adiabatic calorimetry in the temperature range T?=?12.28–344.06?K. No obvious anomalies were observed on the curve obtained. The values of standard thermodynamic functions in the temperature range T?=?0–400 K were calculated. Based on low-temperature calorimetry data obtained, previously published data on the high-temperature heat capacity of ytterbium orthovanadate were corrected. The anomalous contribution to heat capacity for YbVO₄ was compared with the data known for YbPO₄.