Pulsed Corona Discharge for Oxidation of Gaseous Elemental Mercury

Positive pulsed corona discharge has been applied for the oxidation of gaseous elemental mercury (Hg0) from a simulated flue gas. The oxidation of Hg0 to HgO and HgCl2 can significantly enhance the mercury removal from flue gas. At a gas condition of O2 (10%), H2O (3%), and N2 (balance), Hg0 oxidation efficiency of 84% was achieved at an input energy density of 45 J/l. The presence of NO, however, hinders Hg0 oxidation due to the preferential reaction of NO with O and O3. On the contrary, SO2 shows little effect on Hg0 oxidation due to its preferential reaction with OH. It has been also observed that the HCl in gas stream can be dissociated to Cl and Cl2 and can induce additional Hg0 oxidation to HgCl2

Drivers’ Visual Perception Quantification Using 3D Mobile Sensor Data for Road Safety

To prevent driver accidents in cities, local governments have established policies to limit city speeds and create child protection zones near schools. However, if the same policy is applied throughout a city, it can be difficult to obtain smooth traffic flows. A driver generally obtains visual information while driving, and this information is directly related to traffic safety. In this study, we propose a novel geometric visual model to measure drivers’ visual perception and analyze the corresponding information using the line-of-sight method. Three-dimensional point cloud data are used to analyze on-site three-dimensional elements in a city, such as roadside trees and overpasses, which are normally neglected in urban spatial analyses. To investigate drivers’ visual perceptions of roads, we have developed an analytic model of three types of visual perception. By using this proposed method, this study creates a risk-level map according to the driver’s visual perception degree in Pangyo, South Korea. With the point cloud data from Pangyo, it is possible to analyze actual urban forms such as roadside trees, building shapes, and overpasses that are normally excluded from spatial analyses that use a reconstructed virtual space

An Interpretable Time Series Forecasting Model for Predicting NOx Emission Concentration in Ferroalloy Electric Arc Furnace Plants

Considering the pivotal role of ferroalloys in the steel industry and the escalating global emphasis on sustainability (e.g., zero emissions and carbon neutrality), the demand for ferroalloys is anticipated to increase. However, the electric arc furnace (EAF) of ferroalloy plants generates substantial amounts of nitrogen oxides (NOx) because of the high-temperature combustion processes. Despite the substantial contributions of many studies on NOx prediction from various industrial facilities, there is a lack of studies considering the environmental condition of the EAF in ferroalloy plants. Therefore, this study presents a deep learning model for predicting NOx emissions from ferroalloy plants and further can provide guidelines for predicting NOx in industrial sites equipped with electric furnaces. In this study, we collected various historical data from the manufacturing execution system of electric furnaces and exhaust gas systems to develop a prediction model. Additionally, an interpretable artificial intelligence method was employed to track the effects of each variable on the NOx emissions. The proposed prediction model can provide decision support to reduce NOx emissions. Furthermore, the interpretation of the model contributes to a better understanding of the factors influencing NOx emissions and the development of effective strategies for emission reduction in ferroalloys EAF plants

Zeolite-Catalyzed Disproportionation of <i>iso</i>-Propylbenzene: Identification of Reaction Intermediates and Mechanism

The catalytic properties of a series of large-pore (H–Y, H-beta, H-mordenite, and H-UZM-35) and medium-pore (H-NU-87, H-TNU-9, and H-ZSM-5) zeolites are compared in <i>iso</i>-propylbenzene (<i>i</i>PB) disproportionation. Among the zeolite catalysts studied here, H-UZM-35 with a three-dimensional framework consisting of one type of straight 12-ring channels and two types of tortuous 10-ring channels was found to show a di-<i>iso</i>-propylbenzenes (D<i>i</i>PBs) yield comparable to that of H-beta with two intersecting 12-ring channels, the best catalyst tested for this reaction to date. Gas chromatography–mass spectrometry analysis of used zeolite catalysts demonstrates that while mono-<i>iso</i>-propylated 2,2-diphenylpropane derivatives serve as real reaction intermediates of <i>i</i>PB disproportionation over large-pore zeolites, mono-<i>iso</i>-propenylated 2,2-diphenylpropane species, which contain a double bond in the alkyl chain, are intermediates of its side reaction. Unlike that of other aromatic hydrocarbons such as <i>m</i>-xylene, ethylbenzene, and <i>n</i>-propylbenzene, the formation of di-<i>iso</i>-propylated derivatives was not observed as reaction intermediates. A new bimolecular diphenylpropane-mediated reaction pathway, which includes both intermediates of main and side reactions of <i>i</i>PB disproportionation, is proposed based on the experimental and theoretical results

Theoretical Investigation of the Isomerization and Disproportionation of <i>m</i>‑Xylene over Medium-Pore Zeolites with Different Framework Topologies

The strain energies of three trimethylated diphenyl­methane (3mDPM) and six tetramethylated diphenyl­methane (4mDPM) isomers serving as the main reaction intermediates of <i>m-</i>xylene isomerization and disproportionation over eight medium-pore zeolites with different framework topologies have been determined theoretically in order to elucidate the effects of zeolite pore structure on this aromatic transformation. Although the strain energies of 3mDPM and 4mDPM derivatives in MCM-22, TNU-9, and NU-87, all of which have large 12-ring cavities/channels, are always lower than 40 kJ mol^–1, some of them in cavity-free ZSM-5, ZSM-57, and TNU-10 are characterized by the strain energies higher than 40 kJ mol^–1. In particular, all the species in ZSM-22 and ZSM-23 with narrower one-dimensional 10-ring channels have the strain energies much higher than 40 kJ mol^–1. On the other hand, the energy difference (<30 kJ mol^–1) between the (dimethylphenyl)­methylium ion and the transition state for formation of the tetramethylated benzenium-type carbenium ions was calculated to be much lower than the energy barrier (183 kJ mol^–1) to the hydride transfer from the reactant molecule. The overall results of this study clearly show that transition-state shape selectivity is responsible for the formation of 3mDPM derivatives, as well as of slightly larger 4mDPM ones, in medium-pore zeolites

Insight into the Unique Oxidation Chemistry of Elemental Mercury by Chlorine-Containing Species: Experiment and Simulation

This work investigated the oxidation chemistry of elemental mercury (Hg-0) by chlorine-containing species produced indirectly through the gas-to-solid phase reaction between NO, gases and NaClO2 powder (NaClO2(s)), where both experiment and simulation results were compared to clarify which species are responsible for the oxidation of Hg-0. At first, we introduced 30 ppm of NO2 into the pack-bed reactor containing NaClO2(S) to produce OCIO species and then injected NO and Hg-0 (260 mu g/Nm(3)) to Mixer, where the concentration of NO was varied up to 180 ppm and the reaction temperature was set to 130 degrees C. We observed for the first time that the degree of Hg-0 oxidation is completely controlled by the introduced concentration of NO: for example, the oxidation efficiency of Hg-0 is drastically increased to become 100% at near 7 ppm NO, but further increasing NO concentration results in the oxidation efficiency of Hg-0 being gradually decreased. The simulation results indicated that such a propensity of Hg-0 oxidation efficiency to NO concentration can be attributed to the NO concentration-dependent Cl, CIO, and Cl-2 formation which plays a critical role in the oxidation of Hg-0.X11810sciescopu

<i>n</i>‑Propylbenzene Disproportionation: An Efficient Tool for Assessing the Framework Topology of Large-Pore Zeolites

The mechanisms of <i>n</i>-propylbenzene (<i>n</i>PB) disproportionation over various large-pore (LaNa-Y, H-Y, H-mordenite, and H-beta) and medium-pore (H-NU-87, H-TNU-9, and H-ZSM-5) zeolites were investigated. The GC–MS results from the used zeolite catalysts demonstrate that monopropylated 1,1-diphenylpropane and dipropylated 1,1-diphenylpropane derivatives are serving as the main reaction intermediates of bimolecular <i>n</i>PB disproportionation, whereas 1-phenyl-2-propylphenylpropane, 1-propylphenyl-2-phenylpropane, and 1-propylphenyl-2-propylphenylpropane species are the intermediates of some particular side reactions. It was found that the intrazeolitic buildup of these five different groups of diphenylpropane-based species is strongly influenced by the size and shape of zeolite void spaces, as was also corroborated by DFT calculation results. This allows <i>n</i>PB disproportionation to be quite useful for estimating the framework topology of zeolites with unknown structures, especially those of large-pore materials