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Abstract: The production of energizing gases such as H2 and CO by gasification process of solid fuels is a technology that has increased in recent years since it is an efficient and clean process. To enable the production of gases, it is necessary to use refractory materials capable of withstanding high temperatures, thermal shock and contact with aggressive media. Nowadays, there is not published literature on refractory materials used for furnaces lining for petroleum coke gasification at high temperatures (∼1900°C). Therefore, this paper deals with the study of alumina and magnesium aluminate/alumina-based refractories as candidates for the furnace lining used in the petroleum coke gasification for steel production. Refractory samples were made with some designed formulations which were subjected to chemical interactions with pellets made of petroleum coke and petroleum coke ash at 1650°C for 4h. After completing the tests, the formulations were cut transversely and were characterized by SEM-EDS and XRD to evaluate the resistance to slag penetration and formation of low melting point phases. The results show that slag penetration and corrosion in the refractory formulations occur due to the formation of hibonite, spinels (Ni2+, Fe2+, Mg2+)(Al, Fe)2O4 and gehlenite phases. However, these phases together stop the molten slag penetration. [Copyright &y& Elsevier]

Fired porcelain scrap has been recycled as filler to obtain a sustainable high voltage porcelain insulator. Quartz was progressively replaced by 5, 10, 15 and 25 wt% of porcelain scraps in a traditional siliceous porcelain composition. The replacement effect on sintered samples at 1250 °C under industrial scheduling using a manufacturing kiln was evaluated by measuring the linear shrinkage, bulk density, porosity, flexural strength, and microhardness. Phase analysis was carried out by X-ray diffraction and microstructural characteristics were studied using a scanning electronic microscope. The results showed that scrap containing samples reached bulk densities around 2.38 g/cm3 and a porosity percentage close to zero. The maximum flexural strength at both unglazed and glazed state was 67.5 MPa and 89.7 MPa, respectively for 5 wt% scrap containing samples. X-ray diffraction studies revealed higher mullite phase in scrap containing samples. Scanning electronic microscopy images of the polished and etched specimens show the presence of quartz grains and secondary mullite needles embedded in a feldspathic vitreous matrix. The properties displayed by the scrap containing samples are highly attractive, since they show similar and, in some cases, superior values in flexural strength, density, and porosity in comparison to those reported for traditional siliceous porcelain. The most outstanding result was found in the flexural resistance, for unglazed porcelain bodies it was improved around 7%, while in glazed porcelain bodies it was improved around 15% with the addition of chamotte in a traditional porcelain composition. These new porcelain compositions can be used to produce noble porcelain insulators as a more sustainable, affordable, and environmentally-friendly alternative. • The higher mechanical strength was for 5 wt% scrap containing samples. • The mechanical strength improvement was attributed to higher mullite concentrations. • Scrap containing samples are highly attractive to produce sustainable insulators. • Scrap containing insulators are an environmentally-friendly alternative. [ABSTRACT FROM AUTHOR]

This paper aims at performing a parametric analysis of the thermoeconomics costs associated with an integrated solid oxide fuel cell (SOFC) system with a vapour-adsorption refrigeration (VAR) system. Particular emphasis is put on the cost of the SOFC’s product (i.e. the electrical energy) and on the cost of the VAR’s product (i.e. the cooling effect). In order to do so, an hybrid system simulator was constructed to determine the influence of SOFC operating parameters: current density, inlet flow temperature, fuel utilization factor and steam to carbon ratio, on the exergy-based costs of the products as well as on the exergoeconomic factors. Results of the analysis show that an energy-based costing can lead to overvaluing the cost of an energy asset. Furthermore, the minimum exergy-based unit cost of electricity is 14 $/GJ and of cooling is 16 $/GJ. The exergoeconomic factor of the VAR systems is the most affected by the operating variables. From this study, it is concluded that production of cold is not highly cost-effective under the operating conditions studied herein. [ABSTRACT FROM AUTHOR]

The influence of MgAl2O4 spinel addition as a ceramic bonding in the MgO–CaZrO3 refractory was established by the evaluation of physical and microstructural characteristics in terms of density, porosity, crystalline phases, phase distribution and morphology. X-ray diffraction analyses and scanning electron microscopy with microanalysis have been used. The mechanical behavior has been evaluated in terms of cold crushing strength at room temperature and modulus of rupture at 25 and 1260°C. Static and dynamic resistances tested by chemical attack of clinker raw constituents have been carried out at 1450°C. Results showed that thermo-mechanical properties significantly improved with increasing the content of spinel. Microstructural analysis revealed that spinel phase aided to develop a strong bond between MgO and CaZrO3 refractory aggregates. Finally, the refractory bodies exhibited a good thermal stability and an excellent chemical resistance against the clinker raw material. [ABSTRACT FROM AUTHOR]

A compact prototype system for H2 production based on a Polymer Electrolyte Membrane (PEM) stack was developed and investigated. A detailed study and an optimization of the Balance of Plant (BoP) was carried out. The system was developed in laboratory by using commercial devices tailored around in house-made membrane electrode assemblies (MEAs). The study regarded both the hydraulic circuit efficiency loss and its optimization by varying process parameters. Energy consumption for auxiliary devices was studied at different temperatures (40, 60 and 75 °C). Efficiency and control strategy management of the system were investigated. Despite an increase of stack performance observed at high temperature, maximum system efficiency (65% compared to HHV) was obtained at 40 °C because of moderate energy consumption by the electric heater. To evaluate the stack contribution to the overall efficiency, the present investigation was completed by a hydrodynamic study of the stack inside the system. Diffusional aspects related to the water mass distribution inside the stack were investigated through a computational fluid dynamic analysis (CFD). In particular, a 3D analysis of the whole stack composed by 120 channels and 10 cells was carried out. The model showed a quite uniform distribution of water over the individual channels and a homogeneous pressure inside the cells. Accordingly, the risk of having hot spots and gases accumulated inside the stack was minimal. [ABSTRACT FROM AUTHOR]

Abstract: World fossil fuel reserve is expected to be exhausted in coming few decades. Therefore, the decentralization of energy production requires the design and integration of different energy sources and conversion technologies to meet the power demand for single remote housing applications in a sustainable way under various weather conditions. This work focuses on the integration of photovoltaic (PV) system, micro-wind turbine (WT), Polymeric Exchange Membrane Fuel Cell (PEM-FC) stack and PEM water electrolyzer (PEM-WE), for a sustained power generation system (2.5 kW). The main contribution of this work is the hybridization of alternate energy sources with the hydrogen conversion systems using mid-term and short-term storage models based in artificial intelligence techniques built from experimental data (measurements obtained from the site of interest), this models allow to obtain better accuracy in performance prediction (PVMSE = 8.4%, PEM-FCMSE = 2.4%, PEM-WEMSE = 1.96%, GSRMSE = 7.9%, WTMSE = 14%) with a practical design and dynamic under intelligent control strategies to build an autonomous system. [Copyright &y& Elsevier]

Abstract: Innovative chrome-free basic refractory bricks have been design based on electrofused magnesia–calcium zirconate (MgO-CaZrO3) technology using as ceramic bonding magnesium aluminate spinel (MgAl2O4) and hercynite spinel (FeAl2O4) in order to improve their properties. Industrial refractory bricks have been manufactured by solid state sintering of magnesium and calcium zirconate aggregates with MgAl2O4 and FeAl2O4 spinels at 1650°C in a tunnel kiln. Physical and microstructural characteristics of new refractory bricks have been characterised in terms of density, porosity, crystalline phases, phase distribution and morphology. X-ray diffraction (XRD) analyses and scanning electron microscopy (SEM) with microanalysis (using energy dispersive spectroscopy analysis -EDS) have been used. The mechanical behaviour has been evaluated in terms of cold crushing strength (CCS) at room temperature and three point bending modulus of rupture (MOR) at 25 and 1260°C. Static and dynamic resistance test by chemical attack of clinker raw meal constituents have been carried out at 1450°C. Results have shown that thermo-mechanical properties of new refractory bricks significantly improved with increasing both type of spinel in content. Microstructural analysis revealed that spinel phases aided to develop a strong bond between the magnesia and calcium zirconate refractory aggregates. Finally, these refractory matrixes exhibit a good thermal stability and an excellent chemical resistance against clinker raw meal. [Copyright &y& Elsevier]

Abstract: An IrO2 catalyst was prepared using a colloidal method followed by a thermal treatment. The catalyst was later mixed with Pt-Black and supported on the Sb-doped SnO2 (ATO), synthesized through the same colloidal method. ATO was investigated as a possible catalyst support in an electrode of a regenerative fuel cell (URFC), where Pt–IrO2 was used as the catalyst for the oxygen evolution and reduction reactions. The morphology and composition of the ATO support was investigated through transmission electron microscopy, X-ray diffraction (including Rietveld Refinement), BET analysis, and X-ray fluorescence. An ATO support was obtained with a highly homogeneous distribution and crystal sizes, measuring approximately 4–6 nm. The Pt–IrO2/ATO material was deposited on a Nafion 115 membrane with 0.5 mg cm−2 of catalyst loading. Pt/Vulcan XC-72 (30 wt. %, E-TEK) was used as the catalyst in the H2 compartment with a Pt loading of 0.4 mg cm−2. The electrochemical activity of the Pt–IrO2/ATO for oxygen evolution/reduction in the URFC system was investigated by AC-impedance spectroscopy, linear voltammetry, and chronoamperometry techniques. The maximum mass current activity was 1118 A g−1 at 1.8 V in proton-exchange membrane water electrolyser mode (PEMWE) and 565 A g−1 at 0.3 V in proton-exchange membrane fuel cell mode (PEMFC), both at 80 °C. The value of the round-trip energy efficiency was approximately 48% at 50 A g−1. [Copyright &y& Elsevier]

Abstract: A new generation of highly efficient and non-polluting energy conversion and storage systems is vital to meeting the challenges of global warming and the finite reality of fossil fuels. In this work, nanosized Pt/IrO2 electrocatalysts are synthesized and investigated for the oxygen evolution and reduction reactions in unitized regenerative fuel cells (URFCs). The catalysts are prepared by decorating Pt nanoparticles (2–10 nm) onto the surface of a nanophase IrO2 (7 nm) support using an ultrasonic polyol method. The synthesis procedure allows deposition of metallic Pt nanoparticles on Ir-oxide without causing any occurrence of metallic Ir. The latter is significantly less active for oxygen evolution than the corresponding oxide. This process represents an important progress with respect to the state of the art in this field being the oxygen electrocatalyst generally obtained by mechanical mixing of Pt and IrO2. The nanosized Pt/IrO2 (50:50 wt.%) is sprayed onto a Nafion 115 membrane and used as dual function oxygen electrode, whereas 30 wt.% Pt/C is used as dual function hydrogen electrode in the URFC. Electrochemical activity of the membrane-electrode assembly (MEA) is investigated in a single cell at room temperature and atmospheric pressure both under electrolysis and fuel cell mode to assess the perspectives of the URFC to operate as energy storage device in conjunction with renewable power sources. [Copyright &y& Elsevier]

Abstract: The electrochemical properties of a proton exchange membrane (PEM) stack electrolyzer (9 cells of 100 cm2 geometrical area) were investigated at different temperatures. An amount of H2 of ∼270 l h−1 was produced at 60 A (600 mA cm−2) and 70 °C under 876 W of applied electrical power. The corresponding specific energy consumed in the process was 3.24 Wh·l−1H2. The Faradic and electrical efficiencies were determined. Overall stack efficiencies of 73% and 85%, at 60 A and 70 °C, with respect to the low and high heating value of hydrogen, respectively, were obtained. These results confirmed the successful scale-up of a previous lab-scale device. [Copyright &y& Elsevier]

Abstract: The introduction of inorganic compounds into the Nafion polymeric matrix represents a possible solution to increase the operative temperature (T > 100 °C) without losing the conductivity, water transport properties and above all improving the mechanical characteristics. Two silica materials with different morphologies were synthesized via sol–gel method (SiO2 and SBA-16) by a tetraethyl orthosilicate (TEOS, 98%, Aldrich). Composite Nafion membranes were prepared using a 3%wt/wt of each powder and a standardized casting method. The influence of morphology on chemical–physical properties of membranes was investigated. It was highlighted that the silica introduction reduces the swelling parameters compared to bare Nafion membrane (NRecast) at room temperature. A similar behaviour was observed also in the proton conductivity measurements, in fact values of 0.144 S/cm, 0.114 S/cm and 0.078 S/cm were recorded at 80 °C for NRecast, NSBA-16 and NSiO2 respectively. Polarisation curves carried out at 100 °C have revealed a better performance for composite membranes (NSBA-16) than NRecast with a similar trend of proton conductivity. [Copyright &y& Elsevier]

Abstract: IrO2 electrocatalysts were prepared and electrochemically characterized for the oxygen evolution reaction in a Solid Polymer Electrolyte (SPE) electrolyzer. By using a sulfite complex-based preparation procedure, an amorphous iridium oxide precursor was obtained at 80 °C, which was, successively, calcined at different temperatures: 350 °C, 400 °C and 450 °C. A physico-chemical characterization was carried out by X Ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray-photoelectron spectroscopy (XPS). The various IrO2 catalysts were sprayed onto a Nafion 115 membrane with a loading of 2.5 mg cm−2 to form the anode. A Pt/C catalyst (Pt loading 0.5 mg cm−2) was used as cathode. The best electrochemical performance was obtained for the cell based on the IrO2 calcined at 350 °C. The maximum current density at high potentials (1.8  V) was about 1.75 A cm−2. Accelerated time-tests at 2 A cm−2 demonstrated a suitable stability of the IrO2 calcined at 350 °C; however, the intrinsic stability appeared to increase with the calcination temperature. The sample calcined at 400 °C could represent a good compromise between performance and intrinsic stability. [Copyright &y& Elsevier]

Abstract: The aim of this work is to incorporate inorganic compounds into the Nafion matrix (composite membranes) for high temperature of a polymer electrolyte fuel cell (T cell >100°C). Three silicon oxides having a different morphology were synthesized starting with a tetraethyl orthosilicate as a precursor via sol–gel method: SBA15, SBA15-SH and SiO2. Successively, composite Nafion membranes were prepared using a 3% (w/w) of each powder through a standardized casting method. The influence of SiO2 morphology on chemical–physical properties of the membranes was highlighted resulting in a reduction of the swelling parameters of the composite membranes if compared at T ≥80°C to a recast bare Nafion membrane, used as a reference. Good proton conductivity was also observed for all composite membranes with values of 0.144Scm−1, 0.136Scm−1, 0.090Scm−1and 0.078Scm−1 recorded at 80°C (100% RH) for Nrecast, NSBA15, NSBA15-SH and NSiO2, respectively. The polarisation curves carried out at 120°C (75% RH, 1.5abs.bar) have revealed a higher stability for NSBA15 membrane after a short time-test, probably because the silica morphology is able to retain water within the polymer matrix and, in accordance to the swelling data. [Copyright &y& Elsevier]

Abstract: An optimization study of components and assembling characteristics for a proton exchange membrane (PEM) short stack electrolyzer (3 cells of 100 cm2 geometrical area) was carried out. The electrochemical properties were investigated by polarization, impedance spectroscopy and chrono-potentiometric measurements. A decrease of the ohmic contact resistance between the bipolar plates and the electrode backing layer was obtained by using an appropriate thickness for the gas diffusion layers/current collectors as well as by an optimization of stack compression. The amount of H2 produced was ∼90 l h−1 at 60 A (600 mA cm−2) and 75 °C under 300 W of applied electrical power. No significant leakage or gas recombination was observed. The stack electrical efficiency was 75% and 88%, at 60 A and 75 °C, with respect to the low and high heating value of hydrogen, respectively. [Copyright &y& Elsevier]

Abstract: A nanosized IrO2 anode electrocatalyst was prepared by a sulfite-complex route for application in a proton exchange membrane (PEM) water electrolyzer. The physico-chemical properties of the IrO2 catalyst were studied by termogravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrochemical activity of this catalyst for oxygen evolution was investigated in a single cell PEM electrolyzer consisting of a Pt/C cathode and a Nafion® membrane. A current density of 1.26Acm−2 was obtained at 1.8V and a stable behavior during steady-state operation at 80°C was recorded. The Tafel plots for the overall electrochemical process indicated a slope of about 80mVdec−1 in a temperature range from 25°C to 80°C. The kinetic and ohmic activation energies for the electrochemical process were 70.46kJmol−1 and 13.45kJmol−1, respectively. A short stack (3 cells of 100cm2 geometrical area) PEM electrolyzer was investigated by linear voltammetry, impedance spectroscopy and chrono-amperometric measurements. The amount of H2 produced was 80lh−1 at 60A under 330W of applied electrical power. The stack electrical efficiency at 60A and 75°C was 70% and 81% with respect to the low and high heating value of hydrogen, respectively. [Copyright &y& Elsevier]

Abstract: The high temperature behaviour of a solid polymer electrolyte (SPE) water electrolyser based on a composite Nafion–SiO2 membrane was investigated and compared to that of a commercial Nafion membrane. The SPE water electrolyser performance was studied from 80 to 120°C with an operating pressure varying between 1 and 3barabs. IrO2 and Pt were used as oxygen and hydrogen evolution catalysts, respectively. The assemblies were manufactured by using a catalyst-coated membrane (CCM) technique. The performance was significantly better for the composite Nafion–SiO2 membrane than commercial Nafion 115. Furthermore, the composite membrane allowed suitable water electrolysis at high temperature under atmospheric pressure. The current densities were 2 and 1.2Acm−2 at a terminal voltage of 1.9V for Nafion–SiO2 and Nafion 115, respectively, at 100°C and atmospheric pressure. By increasing the temperature up to 120°C, the performance of Nafion 115 drastically decreased; whereas, the cell based on Nafion–SiO2 membrane showed a further increase of performance, especially when the pressure was increased to 3barabs (2.1Acm−2 at 1.9V). [Copyright &y& Elsevier]

Abstract: An investigation of carbon-supported Pt/C and PtCo/C catalysts was carried out with the aim to evaluate their stability under high temperature polymer electrolyte membrane fuel cell (PEMFC) operation. Carbon-supported nanosized Pt and PtCo particles with a mean particle size between 1.5nm and 3nm were prepared by using a colloidal route. A suitable degree of alloying was obtained for the PtCo catalyst by using a carbothermal reduction. The catalyst stability was investigated to understand the influence of carbon black corrosion, platinum dissolution and sintering in gas-fed sulphuric acid electrolyte half-cell at 75°C and in PEMFC at 130°C. Electrochemical active surface area and catalyst performance were determined in PEMFC at 80°C and 130°C. A maximum power density of about 700mWcm−2 at 130°C and 3bar abs. O2 pressure with 0.3mgPtcm−2 loading was achieved. The PtCo alloy showed a better stability than Pt in sulphuric acid after cycling; yet, the PtCo/C catalyst showed a degradation after the carbon corrosion test. The PtCo/C catalyst showed smaller sintering effects than Pt/C after accelerated degradation tests in PEMFC at 130°C. [Copyright &y& Elsevier]

Abstract: A nanocomposite re-cast Nafion hybrid membrane containing titanium oxide calcined at T =400°C as an inorganic filler was developed in order to work at medium temperature in polymer electrolyte fuel cells (PEFCs) maintaining a suitable membrane hydration under fuel cell operative critical conditions. Nanometre TiO2 powder was synthesized via a sol–gel procedure by a rapid hydrolysis of Ti(OiPr)4. The membrane was prepared by mixing a Nafion–dimethylacetammide (DMAc) dispersion with a 3wt% of TiO2 powder and casting the mixture by Doctor Blade technique. The resulting film was characterised in terms of water uptake and ion exchange capacity (IEC). The membrane was tested in a single cell from 80 to 130°C in humidified H2/air. The obtained results were compared with the commercial Nafion115 and a home-made recast Nafion membrane. Power density values of 0.514 and 0.256Wcm−2 at 0.56V were obtained at 110 and 130°C, respectively, for the composite Nafion–Titania membrane. Preliminary tests carried out using steam reforming (SR) synthetic fuel at about 110°C have highlighted the benefit of the inorganic filler introduction when PEFC operates at medium temperature and with processed hydrogen. [Copyright &y& Elsevier]