Experimental trials to make wheat straw pellets with wood residue and binders

Crude glycerol, bentonite, lignosulfonate, and softwood residue (wood residue) were investigated in this study as binders for biomass fuel pellets for thermochemical conversion to enhance pellet quality for transportation and storage. The mass fraction of water of the wheat straw and the wood residue used for pelleting were 0.0676 and 0.0949, respectively. Wheat straw with crude glycerol, bentonite, lignosulfonate, wood residue, and pretreated wood residue with crude glycerol were compressed in a single pelleting unit at a temperature of 95 °C. The specific energy consumption, density, dimensional stability, tensile strength, calorific value, ash content, and chemical composition of the pellets made were determined. Results showed that the specific energy consumption for wheat straw pelletization significantly decreased with the addition of lignosulfonate, bentonite, wood residue, and pretreated wood residue with crude glycerol. With the addition of binders chosen in this study, the tensile strength of wheat straw pellets was improved with values ranging from 1.13 to 1.63 MPa. There was a significant increase in the higher heating value (17.98 MJ kg⁻¹ to 18.77 MJ kg⁻¹) when crude glycerol, wood residue, and pretreated wood residue were used as binders. The addition of both pretreated and non-pretreated wood residue significantly decreased the ash content of wheat straw pellets.     

Ammonia decomposition over citric acid induced γ-Mo2N and Co3Mo3N catalysts

This work focuses on a novel synthesis route, using citric acid as a chelating agent, for the formation of γ-Mo₂N and Co₃Mo₃N bulk catalyst and their application for NH₃ decomposition reaction for hydrogen production having its application for onboard generation of hydrogen for fuel cell in transportation vehicles. Successful formation of the pure bulk phase of Co₃Mo₃N was confirmed by using XRD, XPS, HRTEM techniques. The prepared Co₃Mo₃N catalyst showed high surface area 15.23 m²/g and high catalytic activity compared to bulk γ-Mo₂N for this decomposition reaction, having 97% conversion of NH₃ at 550 °C at 6000 h^?1.     

Ammonia decomposition over citric acid chelated γ-Mo2N and Ni2Mo3N catalysts

A novel synthesis route, using citric acid as a chelating agent, for the formation of γ-Mo₂N and pure phase of Ni₂Mo₃N catalysts and their application for NH₃ decomposition reaction for clean hydrogen production, have been performed. Successful formation of a pure bulk phase of Ni₂Mo₃N was confirmed by using XRD, XPS, HRTEM techniques and found that Ni₂Mo₃N is not air sensitive. Ni₂Mo₃N catalyst showed very high catalytic activity for NH₃ decomposition reaction having ～97% conversion of NH₃ at 525 °C at 6000 h^?1 GHSV, better than previously reported results on any non-promoted, non-precious catalysts, which is mainly due to the formation of pure phase and high surface area for this catalyst using a chelating method of preparation.     

Evolution of hydrogen from magnesium alloy scraps in citric acid-added seawater without catalyst

This work employed a mixture of low-grade Mg scraps (LGMS) and citric acid-added seawater to generate hydrogen gas. Metal catalyst was not required for accelerating the reaction of H₂ generation in the Mg scraps/citric acid solution. LGMS in 20 wt% citric acid-added seawater could produce substantially higher H₂ volume than the LGMS in 5 wt% citric acid-added seawater. Purity of the generated H₂ was about 99% (after dehumidification). By filling H₂-production reactor every 30 min with fresh seawater to which citric acid has been added, ∼70 l of hydrogen could be produced in 100 min.     

Effects of concentrations of NaCl and organic acid on generation of hydrogen from magnesium metal scrap

The study systematically investigates a catalyst-free method of producing H₂ by mixing low-grade Mg scraps (LGMS) in aqueous organic acids. A concave downward relationship exists between the hydrogen yield and the citric acid concentration in seawater. The H₂ yield was highest when the seawater contained 30 wt% citric acid. Activation energy for the H₂ generation in citric acid-added seawater was calculated. H⁺ mobility and H⁺ concentration in citric acid aqueous affect the total H₂ yield, causing that the highest yield occurred at some intermediate citric acid concentration. A concave downward relationship existed between the H₂ yield and NaCl concentration in citric acid solution. NaCl concentration had strong effect on H₂ yield in citric acid solution but did not have the effect on the H₂ yield in acetic acid solution. The H₂ generation rate from the Mg scraps in 15 wt% acetic acid solution evidently exceeded that in 15 wt% citric acid solution although the two solutions each had approximately equal moles of dissociable hydrogen atoms.     

Low temperature synthesis of Cu1−xAl2.5 spinel solid solution as sustained release catalyst for methanol to hydrogen

In order to find a method to synthesize spinel solid solution at low temperature, in this paper, pseudo-boehmite and copper nitrate were used as raw materials, and citric acid was used as accelerator for the first time, the Cu_1?xAl_2.5 spinel solid solutions were synthesized by ball milling treatment of the solid mixture and then calcined at elevated temperatures. The obtained materials were characterized by X-ray diffraction (XRD), Brunner?Emmett?Teller (BET) measurements, H₂-temperature programmed reduction (H₂-TPR), infrared (IR) and thermogravimetric methods (TG), and the mechanism of citric acid promoting the synthesis of the spinel solid solution was suggested. The results show that an optimal amount of citric acid can significantly promote the formation of the spinel structure, thus substantially decreasing the synthetic temperature from the above 900 °C–700 °C. At 700 °C, the preparation without the accelerator resulted in small amount of the spinel solid solution, while the use of accelerator gave rise to 82.96% spinel solid solution. Importantly, the Cu_1?xAl_2.5 spinel solid solution prepared at 700 °C demonstrates the best sustained release catalytic performance, and the catalytic activity reached more than 90% and remained stable within 50 h. The findings of this report might be provide guidance for the solid phase preparation of catalysts at relatively lower temperatures, thus facilitating the commercialization of the sustained release catalyst system.     

A comparison of heat transfer enhancement in a medium temperature thermal energy storage heat exchanger using fins

An experimental energy storage system has been designed using a horizontal concentric tube heat exchanger incorporating a medium temperature phase change material (PCM) Erythritol, with a melting point of 117.7 °C. Three experimental configurations, a control system with no heat transfer enhancement and systems augmented with circular and longitudinal fins have been studied. The results presented compare the system heat transfer characteristics using isotherm plots and temperature-time curves. The system with longitudinal fins gave the best performance with increased thermal response during charging and reduced subcooling in the melt during discharging. The experimentally measured data for the control, circular finned and longitudinal finned systems have been shown to vindicate the assumption of axissymmetry (direction parallel to the heat transfer fluid flow) using temperature gradients in the axial, radial and angular directions in the double pipe PCM system.     

Anode-supported ScSZ-electrolyte SOFC with whole cell materials from combined EDTA–citrate complexing synthesis process

The potential application of combined EDTA–citrate complexing process (ECCP) in intermediate-temperature solid-oxide fuel cells (IT-SOFCs) processing was investigated. ECCP-derived scandia-stabilized-zirconia (ScSZ) powder displayed low packing density, high surface area and nano-crystalline, which was ideal material for thin-film electrolyte fabrication based on dual dry pressing. A co-synthesis of NiO + ScSZ anode based on ECCP was developed, which showed reduced NiO(Ni) and ScSZ grain sizes and improved homogeneity of the particle size distribution, as compared with the mechanically mixed NiO + ScSZ anode. Anode-supported ScSZ electrolyte fuel cell with the whole cell materials synthesized from ECCP was successfully prepared. The porous anode and cathode exhibited excellent adhesion to the electrolyte layer. Fuel cell with 30 μm thick ScSZ electrolyte and La_0.8Sr_0.2MnO₃ cathode showed a promising maximum peak power density of 350 mW cm⁻² at 800 °C.     

Performance enhancement of air-breathing proton exchange membrane fuel cell through utilization of an effective self-humidifying platinum-carbon catalyst

One issue with air-breathing proton exchange membrane fuel cells (AB-PEMFCs) is that the reactants are not externally humidified, and thus the membrane or the catalyst layers might dry out due to electro-osmotic drag, diffusion and evaporation at the opening cathode. This results in a drop in internal ionic conductivity and thus in cell performance. Here, the preparation and characterization of self-humidifying carbon-supported Pt catalyst using citric acid modified carbon black (CA-CB) as the catalyst support are reported. Pt/CA-CB is highly hydrophilic due to the functional groups attached on the carbon support, which endows the ability to retain water in the membrane electrolyte assembly (MEA) and thereby help to improve the performance of AB-PEMFCs. A maximum power density of 204 mW cm⁻² can be achieved in an air-breathing PEMFC stack using Pt/CA-CB, a thick polymer membrane (NRE212) and a circular opening cathode. A 23.4% enhancement in the output power density is obtained by using Pt/CA-CB in place of a commercial catalyst when oblique slit cathodes are employed. This self-humidifying catalyst is particularly suitable for portable PEMFC applications.     

Morphology tuning of bismuth oxychloride nano-crystals by citric acid variation: Application in visible light-assisted dye degradation and hydrogen evolution by electrochemical method

Bismuth Oxychloride (BiOCl) is a p-type indirect bandgap semiconductor with gaps in the range of 3.2–3.5 eV. In this work, BiOCl was synthesized by a simple hydrothermal method along with variation in the concentration of the capping agent citric acid to perform the tuning of the morphology of the samples. The samples were analyzed by various techniques for insight into phase formation, morphology, chemical composition etc. The as-synthesized nanomaterials exhibited extensive variation in crystal structures due to variation in the citric acid ratio. Finally the as-synthesized samples were utilized for effective photocatalytic degradation of toxic textile dyes like Rhodamine B under visible light irradiation and also for hydrogen evolution by electrochemical method. The structural tuning resulted in a noticeable increment in hydrogen evolution observed in an acidic medium for a low overpotential. The as-synthesized material can thus be utilized for waste-water remediation and various electrochemical water-splitting related applications.     

Heat transfer enhancement in medium temperature thermal energy storage system using a multitube heat transfer array

An experimental energy storage system has been designed using an horizontal shell and tube heat exchanger incorporating a medium temperature phase change material (PCM) with a melting point of 117.7 °C. Two experimental configurations consisting of a control unit with one heat transfer tube and a multitube unit with four heat transfer tubes were studied. The thermal characteristics in the systems have been analysed using isothermal contour plots and temperature time curves. Temperature gradients along the three directions of the shell and tube systems; axial, radial and angular directions have been analysed and compared. The phase change in the multitube system was dominated by the effect of convective heat transfer compared to conductive heat transfer in the control system. The temperature gradient in the PCM during phase change was greatest in the radial direction for both the control and multitube systems. The temperature gradients recorded in the axial direction for the control and multitube systems during the change of phase were respectively 2.5 and 3.5% that of the radial direction, indicating essentially a two-dimensional heat transfer in the PCM. The onset of natural convection through the formation of multiple convective cells in the multitube system significantly altered the shape of the solid liquid interface fluid flow and indicates the requirement for an in-depth study of multitube arrangements.     

High performance of bulk Mo2N and Co3Mo3N catalysts for hydrogen production from ammonia: Role of citric acid to Mo molar ratio in preparation of high surface area nitride catalysts

Hydrogen production from ammonia decomposition was studied using a series of unsupported high surface area molybdenum nitride (Mo₂N) and cobalt promoted molybdenum nitride (3%Co-Mo₂N) catalysts prepared with citric acid (CA) as a chelating agent. To elucidate the influence of citric acid amount in preparation conditions on the structure and catalytic activity, we prepared catalysts with different citric acid to Mo molar ratios i.e. CA/Mo = 1, 2, 3 and 4. The catalytic activity was evaluated in the temperature range of 300–600 °C at atmospheric pressure. The catalytic activity of the tested samples has changed in the following order of CA/Mo atomic ratio of 1 < 2 < 3 > 4. Therefore, the catalyst prepared by using CA/Mo ratio = 3 showed the highest catalytic activity. BET, XRD, XPS, SEM and TEM-EDS techniques were been used to characterize the catalysts. The increased activity of Mo₂N-3:1 and 3%Co-Mo₂N-3:1 catalysts was due to increased surface area, decreased particle size and increased relative proportions of Mo₂N and Co₃Mo₃N phases. The ammonia conversion for 3%Co-Mo₂N catalyst was increased from 75 to 97% at 550 °C with the increase of CA/Mo ratio from 1 to 3. This enrichment of activity in 3%Co-Mo₂N-3:1 catalyst is due to increased dispersion of Co₃Mo₃N microstructure on γ-Mo₂N platelets confirmed by SEM and TEM results. No deactivation was observed for any catalysts investigated in this study for ammonia decomposition.     

Production of hydrogen by the electrochemical reforming of glycerol–water solutions in a PEM electrolysis cell

An alternative method for producing hydrogen from renewable resources is proposed. Electrochemical reforming of glycerol solution in a proton exchange membrane (PEM) electrolysis cell is reported. The anode catalyst was composed of Pt on Ru–Ir oxide with a catalyst loading of 3 mg cm⁻² on Nafion. Part of the energy carried by the produced hydrogen is supplied by the glycerol (82%) and the remaining part of the energy originates from the electrical energy (18%) with an energy efficiency of conversion of glycerol to hydrogen of around 44%. The electrical energy consumption of this process is 1.1 kW h m⁻³ H₂. Compared to water electrolysis in the same cell, this is an electrical energy saving of 2.1 kW h N m⁻³ H₂ (a 66% reduction). Production rates are high compared with comparable sized microbial cells but low compared with conventional PEM water electrolysis cells.     

Spray-pyrolyzed silicon/disordered carbon nanocomposites for lithium-ion battery anodes

A new and effective approach to prepare carbon-coated Si nanocomposites as high capacity anode materials for lithium-ion batteries with markedly improved electrochemical performance is described. Initially, nanosized Si particles (<100 nm) were mixed with different concentrations of the carbon source precursor, citric acid in ethanol solution via ultrasonication. Spray pyrolysis of these mixtures at 400 °C in air resulted in an amorphous carbon coating on the spherical Si nanoparticles. High-resolution transmission electron microscopy (HRTEM) analysis confirms a homogeneous layer of amorphous carbon coating of ∼10 nm. These resultant nanocomposites show excellent cycling performance, especially when the disordered carbon (DC) content is above 50 wt.%. The 44Si/56DC nanocomposite shows the highest specific capacity retention of 1120 mAh g⁻¹ after 100 cycles. The carbon-coating on the nanocrystalline Si particles appears to be the main reason for the good cyclability, suggesting the excellent potential of these Si/DC-based nanocomposites for use as alternative anodes for lithium-ion batteries.     

An improved synthesis method of ceria-carbonate based composite electrolytes for low-temperature SOFC fuel cells

SDC-carbonate composite electrolytes for low-temperature Solid Oxide Fuel Cells (LTSOFC) have been synthesized by an improved freeze drying method based on the formation of lanthanide citrate complex solution/gel. This method can not only maintain small particle sizes in composite, but also control the carbonate composition precisely. To optimize the electrochemical performance of the composite electrolytes, SDC-carbonate samples with different carbonate contents were prepared and investigated. SEM, EDS, MPD and XRD analyses were applied to characterize the morphology and carbonate content and EIS was used to determine the ionic conductivity of the electrolyte. The highest conductivity achieved was 400 mS/cm at 600 °C.