NOx formation in post-flame gases from syngas/air combustion at atmospheric pressure

Species concentration measurements specifically those associated with nitrogen oxides (NO_x) can act as important validation targets for developing kinetic models to predict NO_x emissions under syngas combustion accurately. In the present study, premixed combustion of syngas/air mixtures, with equivalence ratio (Φ) from 0.5 to 1.0 and H₂/CO ratio from 0.25 to 1.0 was conducted in a McKenna burner operating at atmospheric pressure. Temperature and NO_x concentrations were measured in the post-combustion zone. For a given H₂/CO ratio, increasing the equivalence ratio from lean to stoichiometric resulted in an increase in NO and decrease in NO₂ concentration near the flame. Increasing the H₂/CO ratio led to a decrease in the temperature as well as the NO concentration near the flame. Based on the axial profiles above the burner, NO concentration increases right above the flame while NO₂ concentration decreases through NO₂-NO conversion reactions according to the path flux analysis. In addition, the present experiments were operated in the laminar region where multidimensional transport effects play significant roles. In order to account for the radial and axial diffusive and convective coupling to chemical kinetics in laminar flow, a multidimensional model was developed to simulate the post-combustion species and temperature distribution. The measurements were compared against both multidimensional computational fluid dynamics (CFD) simulations and one-dimensional burner-stabilized flame simulations. The multidimensional model predictions resulted in a better agreement with the measurements, clearly highlighting the effect of multidimensional transport.     

Characterization and comparative evaluation of polysulfone and polypropylene hollow fiber membranes for blood oxygenators

Blood oxygenators are used to saturate oxygen levels and remove carbon dioxide from the body during cardiopulmonary bypass. Although the natural lung is hydrophilic, commercially used oxygenator materials are hydrophobic. Surface hydrophobicity weakens blood compatibility, as long-term contact with the blood environment may lead to different degrees of blood activity. Polysulfone may be considered an alternative hydrophilic material in the design of oxygenators. Therefore, it may be directed toward developing hydrophilic membranes. This study aims to investigate the feasibility of achieving blood gas transfer with a polysulfone-based microporous hollow fiber membrane and compare it with the commercially available polypropylene membranes. Structural differences in the membrane morphology, surface hydrophilicity, tortuosity, mass transfer rate, and material properties under different operation conditions of temperature and flow rates are reported. The polysulfone membrane has a water contact angle of 81.3°, whereas a commercial polypropylene membrane is 94.5°. The mass transfer resistances (s/m) for the polysulfone and polypropylene membranes are calculated to be 4.8 × 10⁴ and 1.5 × 10⁴ at 25°C, respectively. The module made of polysulfone was placed in the cardiopulmonary bypass circuit in parallel with the commercial oxygenator, and pH, pO₂, pCO₂ levels, and metabolic activity were measured in blood samples.     

Short–mid-term solar power prediction by using artificial neural networks

Solar irradiation is one of the major renewable energy sources and technologies related with this source have reached to high level applications. Prediction of solar irradiation shows some uncertainties depending on atmospheric parameters such as temperature, cloud amount, dust and relative humidity. These conditions add new uncertainties to the prediction of this astronomical parameter. In this case, prediction of generated electricity by photovoltaic or other solar technologies could be better than directly solar irradiation.In this paper, firstly, Artificial Neural Networks (ANNs) methodology is applied to data obtained from a 750 W power capacity of solar PV panel. The main objective of this paper is to determine time horizon having the highest representative for generated electricity prediction of small scale solar power system applications. It is seen that 5 min time horizon gives the best solar power prediction for short term and 35 min could be used for medium terms in April. In addition, these time horizons have increased to 3 and 40 min for very short time and medium time prediction respectively during August. During April and August Root Mean Square Errors (RMSEs) between measured and testing values changed between 33–55 W and 37–63 W ranges respectively. Especially, during August for solar irradiation, stationary conditions are observed and these situations let ANN predict easily generated electricity from 30 to 300 min ahead.     

One-pot preparation of fluorinated mesoporous silica nanoparticles for liquid marble formation and superhydrophobic surfaces

One-pot synthesis of fluorinated mesoporous silica nanoparticles (FMSNs) is reported. Uniform mesoporous nanoparticles are prepared by condensation of tetraethyl orthosilicate (TEOS) and fluoroalkyl containing organotriethoxy silane monomers, respectively. The method enables selective deposition of fluorine atoms on the surface of the particles. FMSNs are used to prepare stable liquid marbles with water. An organo-modified silica sol is used with FMSNs to prepare mechanically stable superhydrophobic surfaces (water contact angle of 161°). The mechanical stability of the surface is investigated with water dripping and adhesive tape tests. The prepared FMSNs are promising building blocks for robust, large-area, and multifunctional self-cleaning surfaces.     

Understanding mercury binding on activated carbon

Understanding the mechanism by which mercury adsorbs on activated carbon is crucial to the design and fabrication of effective capture technologies. In this study, the possible binding mechanism of mercury (Hg) and its species, i.e., HgCl and HgCl₂ on activated carbon is investigated using ab initio-based energetic calculations. The activated carbon surface is modeled by a single graphene layer in which the edge atoms on the upper side are unsaturated in order to simulate the active sites. In some cases, chlorine atoms are placed at the edge sites to examine the effect of chlorine on the binding of Hg, HgCl and HgCl₂. It has been concluded that both HgCl and HgCl₂ can be adsorbed dissociatively or non-dissociatively. In the case of dissociative adsorption, it is energetically favorable for atomic Hg to desorb and energetically favorable for it to remain on the surface in the Hg¹⁺ state, HgCl. The Hg²⁺ oxidized compound, HgCl₂ was not found to be stable on the surface. The most probable mercury species on the surface was found to be HgCl.     

Allyl phosphonium salt–modified clay for photocured coatings: Influence on the properties of polyester acrylate‐based coatings

In this study, bentonite clay was modified with a phosphonium salt and this modified clay was used to prepare polyester acrylate based coatings to improve their flame retardancy and mechanical properties. Photocured composites were prepared with 1, 2, and 3 wt% phosphonium salt modified clay and for comparison 1 wt% nonmodified clay containing composites were also prepared. Modified clay displayed good dispersion properties due to its increased basal spacing. Composites were characterized by FT‐IR and XRD measurements. According to XRD results, it was found that the modified clay was exfoliated in the composites. Furthermore, we investigated the effect of allyl phosphonium salt modified clay on the thermal, mechanical, and flame retardant properties of polyester acrylate based composites coatings. When compared with neat clay containing coatings, modified clay containing photocured coatings exhibited increased modulus and enhanced thermal properties due to increased crosslinking density. Moreover, the presence of the phosphonium salt enhanced the flame retardancy of the polyester based coatings. POLYM. COMPOS., 36:946–954, 2015. © 2014 Society of Plastics Engineers     

Effect of fuel composition on NOx formation in high‐pressure syngas/air combustion

In this study, an experimental investigation of lean premixed syngas/air flames with H₂/CO ratio of 1.0 and equivalence ratio of 0.5 has been conducted in a high‐pressure burner facility to investigate the effects of pressure and the presence of hydrocarbons on NO_x speciation. Detailed NO_x speciation measurements in the post‐flame region were conducted for various pressures up to 1.5 MPa (15 bar) using Fourier transform infrared (FTIR) spectroscopy. When the pressure is increased, NO concentration decreases while NO₂ increases due to pressure dependence of NO to NO₂ conversion. For a given pressure, the presence of hydrocarbons in syngas leads to an increase in NO_x concentrations possibly due to prompt NO formation. Comparison of NO concentrations in presence of CH₄ at different pressures shows that the effect of CH₄ due to prompt NO formation is more dominant than the effect of pressure on NO. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3134–3140, 2018