Periodica Polytechnica (Budapest University of Technology and Economics)
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Preparation of Magnesium Titanate by Using Magnesium Chloride a Byproduct of Titanium Plant
Get PDFThis study explores the preparation of magnesium titanate using magnesium chloride, a byproduct of the titanium production plant as a precursor. The synthesis involves the reaction of MgCl2 with titanium tetrachloride under controlled thermal conditions. Initially, MgCl2 and TiCl4 are thoroughly mixed in stoichiometric proportions with an excess of oxalic acid solution to produce magnesium titanyl oxalate. The mixture is then subjected to a calcination process at temperatures ranging from 300 °C to 1000 °C in an oxygen-rich environment. The physicochemical properties of the synthesized MgTiO3 were analyzed using EDS, XRD, TG/DTA, SEM, and particle size analysis. This comprehensive set of analytical techniques provides a thorough understanding of the elemental, structural, thermal, morphological and physical characteristics of magnesium titanate. The formation of pure magnesium titanate is confirmed at temperatures above 800 °C, with lower temperatures leading to the presence of intermediate phases such as MgTi2O5. The synthesized MgTiO3 exhibits a homogeneous microstructure with well-defined grain boundaries, indicating successful preparation of the desired ceramic material
Modeling of a PEM Electrolyzer Operating at Part Load Conditions for Dynamic Simulation in DWSIM
Get PDFThe development and integration of renewable energy sources have created a growing need for efficient and flexible energy storage solutions. Proton exchange membrane (PEM) electrolysis offers a promising method for hydrogen production, a key component in the future of sustainable energy. This study focuses on the modeling and dynamic simulation of a PEM electrolyzer operating under part-load conditions using DWSIM, an open-source process simulation software. The ability of a PEM electrolyzer to operate at 10–100% of its nominal power allows for adjusting energy consumption based on current electricity prices. The primary objective is to develop a comprehensive model that represents the behavior of a PEM electrolyzer under varying operational conditions, particularly when the system is not functioning at full capacity. Considering that increasing the supplied power reduces the PEM electrolyzer efficiency due to the increase in overpotentials, the model should be optimized for the most cost-effective energy consumption. The results show that increasing the PEM stack operating temperature reduces both energy consumption and hydrogen production costs. Reducing hydrogen demand lowers energy consumption and production costs, due to the greater part-load flexibility, optimizing PEM electrolyzer operation during low electricity price periods
Numerical Study on the Retrofitting of Exterior RC Beam-column Joints with CFRP Composites Using the Grooving Method
Get PDFRetrofitting seismically deficient beam-column joints (BCJs) in reinforced concrete (RC) structures is crucial to preventing collapse during high-intensity earthquakes. Fiber reinforced polymer (FRP) composites have proven effective for retrofitting these components, but debonding of the FRP from concrete surfaces remains a challenge. Recently, the grooving method (GM) has emerged as a promising solution to mitigate this issue, enhancing the bond between FRP and concrete. This paper presents a numerical investigation of BCJs retrofitted with FRP composites using the GM, focusing on various design parameters. The study utilized finite element models developed in ABAQUS, incorporating the concrete damage plasticity (CDP) model to simulate the nonlinear behavior of concrete. The interface between the concrete and FRP was modeled as a perfect bond, simulating the strong adhesion provided by the GM. The numerical results were validated against experimental data from two BCJ specimens, showing good agreement in terms of load-displacement behavior, peak loads, and failure modes. Key parameters studied include the beam longitudinal reinforcement ratio, column axial load ratio, and joint aspect ratio. The findings reveal that these parameters significantly affect the shear capacity of retrofitted joints, impacting the efficiency of the retrofitting
Failure Mechanism and Control Technology of the Primary Support for Asymmetric Deformation Disaster of Deep Tunnel: A Case Study
Get PDFAsymmetric large deformation disasters inevitably occur when highway tunnels cross active fault zones. Relying on the Nanlangshan No.1 Tunnel Project, the mechanism of asymmetric deformation is analyzed based on the in-situ engineering geology and tunnel monitoring data, and numerical calculations are used for verification. Based on the results of asymmetric large deformation disaster analysis, the control scheme of double-layer primary support is proposed, and the design is optimized with numerical calculation before engineering practice. The conclusions are as follows: 1. The original primary support program cannot withstand the asymmetric surrounding rock pressure, and the slip of the weak interlayer in the engineering geology is the main reason for the asymmetric deformation disaster in the tunnel. 2. According to the results of the numerical calculations, the tilted weak interlayer greatly reduces the stability of the surrounding rock, which leads to the local bending damage in the left shoulder of the tunnel, and the local shear deformation damage in the right arch girdle. 3. When using the double-layer primary support program, the appropriate delay of support timing for the second layer of primary support can effectively decrease the tunnel asymmetric deformation. However, if the second layer of primary support lag distance is too large, it will also lead to tunnel deformation convergence larger, or support failure and other issues. So, it is recommended that the second layer of primary support lags behind the first layer of primary support by 2 m to be applied
Processes Towards Sedimentation around a Reed Island in a Shallow Lake
Get PDFThere are many studies on the hydromorphological impacts of emergent aquatic vegetation, but many of these focus on gravity-driven flows in riverine or tidal environments. However, an added effect of emergent vegetation in lakes is that it reduces the main external force (wind) significantly and in a spatially coherent way. We performed long Monte Carlo simulations using a 2D hydrodynamic model and a spectral wind wave model to study resuspension dynamics around a 100-m-wide reed island in southern Lake Fertő/Neusiedl. Wave-current interaction, computed in a post-processing step, was found to enhance maximum bed shear stresses only on the leeward side of the reed island, and even there to a small extent. We have found evidence that the present bed topography is close to an equilibrium where simulated combined wave-current shear stresses have a reasonably uniform exceedance probability over the critical shear stress of the bed sediment. We also found that an artificially flattened lakebed around the reed island would start evolving towards the present bed topography and grain size distribution (both of which were surveyed in the field). Despite the limitations of our modelling framework, our results illustrate the importance of how wind climate is translated to an uneven distribution of sediment entrainment around the reed island, explaining tendencies of sediment accumulation and sorting. Our results lead to a better understanding of the complicated processes involving interaction among wind, vegetation, circulation, wind waves, sediment and bathymetry
Characterization and the Effect of Different Parameters on Photocatalytic Activity of Montmorillonite/TiO2 Nanocomposite under UVC Irradiation
Get PDFThis study aimed to modify montmorillonite (MMT) with titanium dioxide (TiO2) by wet stirring method combined with ultrasonic to form MMT/TiO2 nanocomposite and used as a photocatalyst in the removal of organic dye rhodamine B (RhB). The characteristics of the synthesized samples were analyzed by methods such as energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). The degradation of RhB was carried out for 210 min under UVC irradiation, and the decolorization efficiency of RhB was evaluated by UV-vis spectroscopy. The results show that the TiO2 anatase nanoparticles are randomly distributed on the surface or the space between the MMT sheets to form a house-of-card structure. After 210 min of exposure under a UVC light source, the decolorization efficiency reached 91.5% for the solution with pH = 6.8, photocatalyst content 0.1 g/L, initial concentration RhB 10 mg/L, and UVC power 15 W. Liquid chromatography–mass spectrometry (LCMS) identified the degradation intermediates that MMT/TiO2 successfully cleaved the chromophore structure and formed more minor broken-ring by-products. The influence of operating parameters on RhB removal efficiency, including solution pH, photocatalyst content, initial dye concentration, inorganic, and organic scavengers, was studied. In addition, the kinetic modeling study shows that the RhB photodegradation reaction is consistent with the Langmuir-Hinshelwood first-order kinetic model
Pervaporation Separation of Tetrahydrofuran/Water Azeotropic Mixtures using Phosphorylated Blend Membranes
Get PDFIn this study, we developed novel phosphoric acid crosslinked blend membranes for the pervaporation separation of tetrahydrofu-ran/water mixtures. Sodium alginate and chitosan blend membranes were prepared by solution casting and solvent evaporation technique. These blend membranes were crosslinked with phosphoric acid in isopropanol/water baths and used for pervaporation separation of feed mixtures ranging from 6 to 43 wt.% water in tetrahydrofuran (THF)/water mixtures at 30 °C. Crosslinking was confirmed by Fourier transform infrared (FTIR) and Ion Exchange Capacity (IEC) study. Thermal stability and crystallinity of the membranes were determined from thermogravimetric analysis (TGA) and X-ray diffraction (XRD) studies respectively. The surface morphology of the membranes was observed using Scanning electron microscopy (SEM). Sorption studies were carried out to evaluate the extent of interaction and degree of swelling of the membranes in THF, water and binary mixtures. The effect of experimental parameters such as feed composition, membrane thickness, and permeate pressure on separation performance of the phosphorylated membranes were determined. These membranes were found to have good potential for breaking the azeotrope of 94 wt.% THF with a selectivity of 459 and normalized flux of 0.25 kg m−2 h−1 10 µm. The membrane performance exhibited a reduction in selectivity and an improvement in flux with increasing feed water compositions. Selectivity improved and flux decreased with increasing membrane thickness. Both flux and selectivity decreased with increasing permeate pressure
New Sustainable Pd(II)/Fe(III) Catalytic System Very Efficient in the Hydromethoxycarbonylation of 1-octene
Get PDFIn order to increase the catalytic activity of the Pd(II)-complexes in the alcoxycarbonylation of 1-olefins, the presence in solution of a strong Brönsted acid together with a phosphine ligand is usually required. From an industrial point of view, such two additives, however, influenced the sustainability of the process mainly caused by the related corrosion of the reaction vessel and the toxicity of the phosphine ligand.In this paper, the methoxycarbonylation of 1-octene has been efficiently carried out by using the [Pd(TsO)2(PPh3)2]/FeCl3 catalyst system. The catalyst is very active also without addition of PPh3, reaching the TON of ca. 1300 (mol/mol) in 2 hours by using the Fe(III)/Pd(II) = 400/1 (mol/mol) system. Such value is higher than the values obtained by using the traditional strong Brönsted acid TsOH or other Lewis acid such as AlCl3, in the presence of PPh3. The reaction takes place with the formation of two isomeric products of linear and branched structures with a yield towards the linear isomer of ca. 80%