Minimization of air pollutants emissions by process improvement of catalytic reforming unit in an Iranian old refinery

The old oil refineries are largest chemical industries that are responsible for emission of several pollutants and GHGs. It is possible to minimize energy usage as well as air pollution by some process modification. The main objectives of this investigation were the minimization of air pollution and CO₂ emissions in catalytic reforming unit in an oldest and largest refinery in Iran. To assess the air quality, ten sampling stations were selected for measurement of CO, H₂S, SO₂, and PM₁₀ in ambient air. Also concentrations of C₁–C₅, H₂S, and CO₂ were measured in selected unit. In final, structural and process flaws were identified by analyzing real functional circumstances and they were modified. Results show that SO₂, H₂S, and PM₁₀ concentrations are higher than ambient air standard levels in all seasons. Also, according to achieved results, the cold separator gas flow rate is reduced from 38,936 kg/day (once-through gas process) to 9,649 kg/day (recycle gas process). Beside CO₂ and SO₂ emission rates will be reduced 1803 and 136.5 kg/day in this unit, respectively. Furthermore, the modification of this process causes prevention of 1654 kg CO₂ emission into the atmosphere, during each coke burning and catalytic regeneration.     

The preparation and properties of an antimony sulphide glass

A glass has been prepared in the Sb₂S₃PbS system at compositions very close to 80 mol % Sb₂S₃: 20 mol % PbS. It has been studied by powder x-ray diffraction, optical and high resolution transmission microscopy and infra-red spectroscopy, and its decomposition characterised by differential scanning calorimetry. Hardness values are also reported. This glass displays a wide range of transparency from 4.5 to 16.5 μm and may be of interest for a number of infrared applications. Structural studies indicate that it is formed of SbS and PbS polyhedra similar to those found in the crystalline PbSbS sulphides, and recrystallisation of the glass, observed by electron microscopy shows that the rearrangement of the polyhedra in transforming from the glass state to the crystalline state is feasible. The formation of the glass and its limited composition range are discussed in terms of the strain involved in linking the PbS and SbS polyhedra together and this leads to a number of suggestions as to how the existence region over which the glass forms could be expanded.     

The influence of an Austrian fly ash on the reaction processes in the clinker phases of Portland cements

The aim of the paper is to establish the influence of fly ash on the hydration process of the cement and fly ash mixtures. Particular attention was paid to the influence on the main clinker phases, C₃S, C₂S and C₃A being investigated by X-ray methods at various points during the reaction period. The reaction partners used were two normal Austrian Portland cements plus an Austrian brown-coal ash. In addition to the pure cements, a mixture with 30% fly ash and 70% of the respective cements was also investigated. For purposes of comparison, it was also necessary to analyse in each case a cement mixture with an inert substance in the same ratio.     

Reinterpretation of precipitation behavior in an aged AlMgCu alloy

Precipitation behavior of AlMgCu alloy during S phase aging sequence was studied with high resolution transmission electron microscope (HRTEM) and selected area diffraction (SAED) to determine the existence of S″ phase and GPBII zone in the alloy. Fast Fourier transform (FFT) patterns corresponding to GPB zones at different aging stages were observed, and it is revealed that S phase forms instantly after the GPB zone dissolves during aging. Both simulated HRTEM and SAED images illustrate that the S″ phase shows exactly the same characteristics as the S phase does, which is consistent with the experimental observations. A unique phase was also observed, which produced extra diffraction dots near the {012}_Al positions in FFT pattern. This phase was once considered to be either S″ phase or GPBII zone, but none of them has been affirmed so far. In this work, it is found that the unique phase is a distorted and rotated S phase and that S″ phase or GPBII zone does not form during the aging. We further show that the S precipitation sequence of the aged AlMgCu alloy should be SSS → Cu–Mg clusters/GPB zone → S′/S(Al₂CuMg).     

Convective Heat Transfer at an Annular Jet Impingement on a Flat Blockage

The experimental results on heat transfer of an annular impinging jet have been. The Reynolds numbers Re = (1.2–3.6) × 10⁴, the distance S from the nozzle to a blockage, S/d₀ = 2, 4, 6, and the circular slit height d₂/d₀ = 0.51 and 0.71, where d₀ and d₂ are the internal and external nozzle diameters, have been varied. It is shown that at the same air mass flow rate, replacement of a round nozzle with an annular one results in heat-transfer intensification (up to 70% at the stagnation point). The maximum heat transfer gain occurs at a small nozzle–wall distance (S/d₀ = 2). The heat-transfer increase is accompanied by an increase in the thermal pulsation intensity. The degree of intensification of the heat exchange depends on the height of the circular slit and the nozzle–wall distance.     

Reactive sputtering of thin Cu2S films for application in solar cells

Thin layers of cuprous sulphide were deposited by reactive r.f. sputtering; the target was pure copper and the sputtering gas was an ArH₂S mixture. We describe here how the composition of the films and their stoichiometry can be derived accurately both from X-ray diffraction and the optical reflection and transmission spectra. Measurement of the electrical resistivity can be used as a quick qualitative identification method.The application of these characterization methods to our sputtered films indicates that the crucial parameters to be controlled are the total pressure of the sputtering gas and, in particular, the partial pressure of the H₂S. Too low partial pressures of H₂S result in the presence of copper precipitations in the Cu₂S film, whereas too high H₂S partial pressures result in the presence of copper-deficient Cu_xS phases; there is an intermediate range of H₂S partial pressures in which pure chalcocite films (Cu₂S) are obtained. When these films were sputtered onto evaporated CdS layers, we obtained Cu₂S/CdS solar cells with a total area efficiency of above 4%.     

Failure analysis of an A333Gr6 pipeline after exposure to a hydrogen sulfide environment

The analysis of an A333Gr6 pipeline failure was conducted after exposure to high H₂S partial pressure for several hours. Chemical composition, metallurgical structure, steel pipe hardness, and the welding joint near the broken position were studied. The chemical compositions of corrosion products inside the steel pipe were also analyzed. Results show that corrosion products consist of Fe₃O₄ and FeOOH without ferrous sulfide. Stress analysis was obtained through the finite element analysis method. The failure analysis and calculation results show that spontaneous ferrous sulfide combustion in a high H₂S environment leads to high temperature and pressure in the pipe, resulting in pipeline breakage.     

Sulfur‐Modified Graphitic Carbon Nitride Nanostructures as an Efficient Electrocatalyst for Water Oxidation

There is an urgent need to develop metal‐free, low cost, durable, and highly efficient catalysts for industrially important oxygen evolution reactions. Inspired by natural geodes, unique melamine nanogeodes are successfully synthesized using hydrothermal process. Sulfur‐modified graphitic carbon nitride (S‐modified g‐CN _x ) electrocatalysts are obtained by annealing these melamine nanogeodes in situ with sulfur. The sulfur modification in the g‐CN _x structure leads to excellent oxygen evolution reaction activity by lowering the overpotential. Compared with the previously reported nonmetallic systems and well‐established metallic catalysts, the S‐modified g‐CN _x nanostructures show superior performance, requiring a lower overpotential (290 mV) to achieve a current density of 10 mA cm^?2 and a Tafel slope of 120 mV dec^?1 with long‐term durability of 91.2% retention for 18 h. These inexpensive, environmentally friendly, and easy‐to‐synthesize catalysts with extraordinary performance will have a high impact in the field of oxygen evolution reaction electrocatalysis.     

Inorganic–Organic Hybrid Nanoprobe for NIR‐Excited Imaging of Hydrogen Sulfide in Cell Cultures and Inflammation in a Mouse Model

Hydrogen sulfide (H₂S) is an important gaseous signaling agent mediated by many physiological processes and diseases. In order to explore its role in biological signaling, much effort has been focused on developing organic fluorescent probes to image H₂S. However, these downconversion H₂S probes are impractical for bio‐imaging beyond a certain depth because of the short tissue penetration of UV/visible light (as an excitation source). In most circumstance, these probes are also not suitable for long‐term assay due to photo‐bleaching. Herein, a new design to detect H₂S based on the coumarin‐hemicyanine (CHC1)‐modified upconversion nanophosphors is reported. This inorganic–organic integrated nanoprobe is demonstrated to display a fast response time with a large ratiometric upconversion luminescence (UCL) enhancement, and extraordinary photo‐stability. CHC1‐UCNPs not only can be used for ratiometric UCL monitoring of pseudo‐enzymatic H₂S production in living cells, but can also be used to identify the risk of endotoxic shock through ratiometric UCL imaging of tissue and measurement of endogenous H₂S levels in plasma. The first ratiometric UCL H₂S nanoprobe reported here may be further developed as the next‐generation diagnostic tool for the detection of inflammatory‐related diseases.     

Porous Hollow‐Structured LaNiO3 Stabilized N,S‐Codoped Graphene as an Active Electrocatalyst for Oxygen Reduction Reaction

A nanohybrid based on porous and hollow interior structured LaNiO₃ stabilized nitrogen and sulfur codoped graphene (LaNiO₃/N,S‐Gr) is successfully synthesized for the first time. Such a nanohybrid as an electrocatalyst shows high catalytic activity for oxygen reduction reaction (ORR) in O₂‐saturated 0.1 m KOH media. In addition, it demonstrates a comparable catalytic activity, longer working stability, and much better alcohol tolerance compared with commercial Pt/C behavior in same experiment condition. The obtained results are attributed to synergistic effects from the enhanced electrocatalytic active sites on the rich pore channels of porous hollow‐structured LaNiO₃ spheres and heteroatom doped efficiency on graphene structure. In addition, N,S‐Gr can meritoriously stabilize monodispersion of the LaNiO₃ spheres, and act as medium bridging for high electrical conductivity, thereby providing large active surface area for O₂ adsorption, accelerating reduction reaction, and improving electrochemical stability. Such a hybrid opens an interesting class of highly efficient non‐Pt catalysts for ORR in alkaline media.     

Measurement of sputtered Mg particles in an MgO surface discharge

The experimental analyses of the surface erosion in an MgO surface discharge of an ac plasma display panels (PDPs) were performed. As the result of the surface observation on the MgO layer after accelerated discharge test, the erosion pattern of the MgO surface was spatially non-uniformed and a maximum erosion region existed near the electrode edge side in the MgO surface. To explain the localized erosion of the MgO layer, spatiotemporal distributions of Mg particles emitted from an MgO surface discharge were directly measured using the laser-induced fluorescence (LIF) method. The use of two-level scheme with fluorescence light of 285.2 nm (Mg 3¹P₁-3¹S₀) allowed us to perform measurements at 2 mm above the MgO surface under the condition of S/N (signal to noise ratio) > 3. The result of LIF measurement was found to explain the localized erosion profile obtained from the surface observation on MgO layer.     

Synthesis and characterization of Cu2ZnSnS4 absorber layers by an electrodeposition-annealing route

An electrodeposition-annealing route to films of the promising p-type absorber material Cu₂ZnSnS₄ (CZTS) using layered metal precursors is studied. The dependence of device performance on composition is investigated, and it is shown that a considerable Cu-deficiency is desirable to produce effective material, as measured by photoelectrochemical measurements employing the Eu^3+/2+ redox couple. The differing effects of using elemental sulphur and H₂S as sulphur sources during annealing are also studied, and it is demonstrated that H₂S annealing results in films with improved crystallinity.     

Nanolocalized charge writing in thin SiO2 layers with embedded silicon nanocrystals under an atomic force microscope probe

The possibility of temporally stable nanolocalized charging of thin SiO₂ layers with embedded silicon nanocrystals (nc-Si) is demonstrated. The local charge writing and reading in SiO₂ layers were performed using the electrostatic force microscopy (EFM) technique under the probe of an atomic force microscope. The nc-Si inclusions in a 12-nm-thick SiO₂ layer were obtained using the implantation of low-energy (1 keV) Si⁺ ions, followed by annealing in a nitrogen atmosphere containing 1.5% oxygen. This regime of nc-Si formation significantly improved the structure of nanocrystalline inclusions, which ensured the charge localization on a record level and retention for a prolonged time: the diameter of charged regions in SiO₂ layers with nc-Si inclusions did not exceed 35 nm, while the charge storage time reached tens of hours. The localized EFM charging can be used as a basis of the charge nanolithography on oxide layers. Original Russian Text ? M.S. Dunaevskii, A.N. Titkov, S.Yu. Larkin, A.B. Speshilova, S.E. Aleksandrov, C. Bonafos, A. Claverie, R. Laiho, 2007, published in Pis’ma v Zhurnal Tekhnicheskoĭ Fiziki, 2007, Vol. 33, No. 20, pp. 80–87.     

Near-infrared-emitting colloidal Ag<Subscript>2</Subscript>S quantum dots excited by an 808 nm diode laser

Thioglycolic acid (TGA)-coated colloidal Ag₂S quantum dots (QDs) emitting in the near-infrared (NIR) region upon excitation by an 808 nm diode laser were synthesized. The observed photoluminescence (PL) was attributed to the presence of ligand-modified Ag₂S on the QD surfaces and could be easily controlled by a simple dilution process due to the concentration-dependent surface structure of the colloidal QDs. Upon dilution of the solution, the PL intensity initially increased before later decreasing, with a blueshift being observed in the PL spectra. These phenomena can be accounted for by the aggregation of QDs due to a decrease in the content of ligand-modified Ag₂S on the QD surfaces upon dilution, which in turn affected the fluorescence resonance energy transfer (FRET), and re-emission of the surface energy level.     

Surface-modified cathode materials based on an LiCoO2-LiMn2O4 composite

A process has been developed for surface modification of an equimolar LiCoO₂-LiMn₂O₄ composite with a mixture of alumina (Al₂O₃) and boehmite (AlO(OH)). The alumina: boehmite ratio and pH value have been optimized in order to achieve adequate surface adhesion between the coating and powder and good homogeneity of the nanocoatings. The effects of ultrasonic processing, coating conditions, and thermal annealing have been examined. The results demonstrate that the nanocoatings considerably improve the cyclability of the composite in an extended voltage range (up to 4.5 V) in comparison with the unmodified material and slightly increase its average discharge voltage. Original Russian Text ? E.V. Makhonina, Ya.V. Shatilo, V.S. Dubasova, A.F. Nikolenko, T.A. Ponomareva, E.V. Kisterev, V.S. Pervov, 2009, published in Neorganicheskie Materialy, 2009, Vol. 45, No. 8, pp. 1006–1012.     

Effects of Output-coupling Apertures in a Resonator on Spatial Coherence of CO2 Laser

The degree of spatial coherence S n₁₂ (0) S has been measured for a CO₂ laser beam of radiation emerging from a central output-coupling hole, or four output-coupling holes in the centre-symmetric annular region, in a plane mirror of the Fabry-Perot resonator. The effects of these two kinds of output-coupling apertures on the spatial coherence are studied in association with mode structure in the resonator. The value of S n₁₂ (0) S is always above 0·9 for two points in any location in the beams of radiation emerging from the four output-coupling holes, while it varies with the time in the range 0·5 to 1·0 in a beam of radiation emerging from the central output-coupling hole. Some analytical considerations are given, according to which the value of S n₁₂ (0) S should be approximately unity over the cross-sectional area of a beam of radiation emerging from an output-coupling hole of 6 mm in diameter. This is partly in agreement with the results of the measurements. For the central coupling hole, the fact that S n₁₂ (0) S varies with time is explained qualitatively to be due to the intensity fluctuation in every operating mode, competing with each other in the active resonator. For the four coupling holes a particular mode may be made to survive due to relatively strong mode competition arising from the mode selective effects of the off-centred four coupling holes. On this account a high value of S n₁₂ (0) S may be obtained at two points in the beam separated by 25 mm.     

Synthesis of hierarchical self-supported micropatterns of Cu2S crystals

In this letter, novel hierarchical self-supported micropatterns of Cu₂S polygonal laminae assembled on rod-shaped Cu₂S crystals are successfully prepared by the template-free reaction of Cu₂S and KCN in an aqueous phase. The influence induced by Cl⁻ ions on the self-supported micropatterns of Cu₂S laminae is discussed on the basis of the experimental results.     

Driving force analysis in an infinite anisotropic plate with multiple crack interactions

The methodology and a rigorous solution formulation are presented for stress intesity factors (SIF's, k) and total strain energy release rates (SERR, G _T ) of a multicracked plate, that has fully interacting cracks and is subjected to a far-field arbitrary stress state. The fundamental perturbation problem is derived, and the steps needed to formulate the system of singular integral equations whose solution gives rise to the evaluation of the SIF's are identified. Parametric studies are conducted for two, three and four crack problems. The sensitivity and characteristics of the model is demonstrated.The U.S. Government right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.     

A model on desulfurization characteristics of an entrained bed-bubbling bed hot gas cleanup system for IGCC

A mathematical model has been developed to predict performance of a continuous entrained-bed and bubbling fluidized-bed hot gas desulfurization system in IGCC. The model combines the particle residence time with the kinetic rate in each reactor. The model has been applied to the KIER’s laboratory scale fluidized bed process. The present model provided a reasonable fit in predicting experimental results that the outlet concentration of H₂S from the desulfurizer and SO₂ from the regenerator increased nearly proportionally to the inlet concentration of H₂S to the desulfurizer. The model also could predict well the outlet concentration of O₂ from the regenerator to decrease as the inlet concentration of H₂S to the desulfurizer increased. The present model predicted with reasonable accuracy mean diameter of bed particles and sulfur content of particles in desulfurizer and regenerator.     

Heteroatom‐Mediated Interactions between Ruthenium Single Atoms and an MXene Support for Efficient Hydrogen Evolution

A titanium carbide (Ti₃C₂T_x) MXene is employed as an efficient solid support to host a nitrogen (N) and sulfur (S) coordinated ruthenium single atom (Ru_SA) catalyst, which displays superior activity toward the hydrogen evolution reaction (HER). X‐ray absorption fine structure spectroscopy and aberration corrected scanning transmission electron microscopy reveal the atomic dispersion of Ru on the Ti₃C₂T_x MXene support and the successful coordination of Ru_SA with the N and S species on the Ti₃C₂T_x MXene. The resultant Ru_SA‐N‐S‐Ti₃C₂T_x catalyst exhibits a low overpotential of 76 mV to achieve the current density of 10 mA cm^?2. Furthermore, it is shown that integrating the Ru_SA‐N‐S‐Ti₃C₂T_x catalyst on n⁺np⁺‐Si photocathode enables photoelectrochemical hydrogen production with exceptionally high photocurrent density of 37.6 mA cm^?2 that is higher than the reported precious Pt and other noble metals catalysts coupled to Si photocathodes. Density functional theory calculations suggest that Ru_SA coordinated with N and S sites on the Ti₃C₂T_x MXene support is the origin of this enhanced HER activity. This work would extend the possibility of using the MXene family as a solid support for the rational design of various single atom catalysts.