Products of incomplete combustion from biomass reburning

Fuel reburning usually serves in mitigating NOx formation in stationary combustion sources. However, the use of biomass as reburning fuel could facilitate the production of relatively more nitrogen-containing aromatic products of incomplete combustion. This study investigates the heterogeneous reaction between biomass and mixtures of NO/O2 gases, employing isothermal high-temperature experiments in a vertically-entrained reactor, and in situ diffuse reflective infrared Fourier transform spectroscopy (DRIFTS) under a non-isothermal heating condition ranging from ambient temperature to 700 °C. The method enables sensitive evaluation of the surface species ensuing during the thermal reaction. Results from this study elucidate the formation of nitrated structures as active intermediate species of the heterogeneous reaction. The nitrogenated signatures persist on the surface of the residual ash, suggesting the production of N-aromatics such as nitro-PAH. Considering the severe toxicity and bioaccumulative properties of these by-products, further research should focus on the relative contribution of various reburning fuels, while favouring sustainable fuels such as non-charring plastics

Combustion chemistry of COS and occurrence of intersystem crossing

This contribution combines results of experiments with kinetic modelling to probe the unusual behaviour of carbonyl sulfide (COS), a sulfur species that frequently arises in fuel systems. The experiments identified CO and SO2 as the primary oxidation products, with no formation of CO2. The low ignition temperature (<600 K) of COS observed in prior experiments conflicts with the high activation barrier for the reaction COS + O2 → CO2 + SO of 211.3 kJ mol−1 on the traditional triplet reaction surface. We proposed that, this kinetic barrier prompts the reaction to transfer onto the singlet surface through intersystem crossing that allows the process to surmount lower-energy hurdles. By considering the oxidation of COS as a single step reaction, we fitted the Arrhenius parameter for the reaction COS + O2 → CO + SO2 directly from our experimental measurements. The fitted activation energy of 70.1 kJ∙mol−1 agrees with that of 85.4 ± 20.0 kJ∙mol−1 as calculated in literature at the Hartree-Fock level of theory, indicating the appearance of the intersystem crossing process in the oxidation of COS. The reaction mechanism based on this comportment leads to excellent agreement between the kinetic model and the experimentally measured quantities, such as the onset temperature and the conversion profiles of detected species. The proposed kinetic model for the oxidation of COS provides a tool to design both the SOx mitigation processes and industrial systems for safe handling of sulfur impurities in fossil fuels

Atmospheric emission of NOx from mining explosives: A critical review

High-energy materials such as emulsions, slurries and ammonium-nitrate fuel-oil (ANFO) explosives play crucial roles in mining, quarrying, tunnelling and many other infrastructure activities, because of their excellent transport and blasting properties. These explosives engender environmental concerns, due to atmospheric pollution caused by emission of dust and nitrogen oxides (NOx) from blasts, the latter characterised by the average emission factor of 5 kg (t AN explosive)−1. This first-of-its-kind review provides a concise literature account of the formation of NOx during blasting of AN-based explosives, employed in surface operations. We estimate the total NOx emission rate from AN-based explosives as 0.05 Tg (i.e., 5 × 104 t) N per annum, compared to the total global annual anthropogenic NOx emissions of 41.3 × 106 t N y−1. Although minor in the global sense, the large localised plumes from blasting exhibit high NOx concentration (500 ppm) exceeding up to 3000 times the international standards. This emission has profound consequences at mining sites and for adjacent atmospheric environment, necessitating expensive management of exclusion zones. The review describes different types of AN energetic materials for civilian applications, and summarises the essential properties and terminologies pertaining to their use. Furthermore, we recapitulate the mechanisms that lead to the formation of the reactive nitrogen species in blasting of AN-based explosives, review their implications to atmospheric air pollution, and compare the mechanisms with those experienced in other thermal and combustion operations. We also examine the mitigation approaches, including guidelines and operational-control measures. The review discusses the abatement technologies such as the formulation of new explosive mixtures, comprising secondary fuels, spin traps and other additives, in light of their effectiveness and efficiency. We conclude the review with a summary of unresolved problems, identifying possible future developments and their impacts on the environment with emphasis on local and workplace loads

DFT + U and ab initio atomistic thermodynamics approache for mixed transitional metallic oxides: A case study of CoCu 2 O 3 surface terminations

This study develops a systematic density functional theory alongside on-site Coulomb interaction correction (DFT + U) and ab initio atomistic thermodynamics approachs for ternary (or mixed transitional metal oxides), expressed in three reservoirs. As a case study, among notable multiple metal oxides, synthesized CoCu2O3 exhibits favourable properties towards applications in solar, thermal and catalytic processes. This progressive contribution applies DFT + U and atomistic thermodynamic approaches to examine the structure and relative stability of CoCu2O3 surfaces. Twenty-five surfaces along the [001], [010], [100], [011], [101], [110] and [111] low-Miller-indices, with varying surface-termination configurations were selected in this study. The results portray satisfactory geometrical parameters for bulk CoCu2O3 and a band gap of 1.25 e V. Furthermore, we clarified the stoichiometrically balanced inverted (010)CoCuO, and the non-stoichiometric (001)CuOCu, (001)CoOCo, (110)OCoO and (110)CoOCu surface terminations as the most stable configurations, out of which, the (001)CuOCu shows the optimum stability in ambient conditions. The systematic approach applied in this study should prove instrumental for the analysis of other 3-element multicomponent systems. To the best of our knowledge, the present study is the first to report DFT + U analysis to any 3-multicompnent systems with two of them requires inclusion of U treatment (i.e., f- and d- orbitals) in the electronic structure calculations

Phenol dissociation on pristine and defective graphene

Phenol (C6H5O‒H) dissociation on both pristine and defective graphene sheets in terms of associated enthalpic requirements of the reaction channels was investigated. Here, we considered three common types of defective graphene, namely, Stone-Wales, monovacancy and divacancy configurations. Theoretical results demonstrate that, graphene with monovacancy creates C atoms with dangling bond (unpaired valence electron), which remains particularly useful for spontaneous dissociation of phenol into phenoxy (C6H5O) and hydrogen (H) atom. The reactions studied herein appear barrierless with reaction exothermicity as high as 2.2 eV. Our study offers fundamental insights into another potential application of defective graphene sheets

Probing the reactivity of singlet oxygen with cyclic monoterpenes

Monoterpenes represent a class of hydrocarbons consisting of two isoprene units. Like many other terpenes, monoterpenes emerge mainly from vegetation, indicating their significance in both atmospheric chemistry and pharmaceutical and food industries. The atmospheric recycling of monoterpenes constitutes a major source of secondary organic aerosols. Therefore, this contribution focuses on the mechanism and kinetics of atmospheric oxidation of five dominant monoterpenes (i.e., limonene, α-pinene, β-pinene, sabinene, and camphene) by singlet oxygen. The reactions are initiated via the ene-type addition of singlet oxygen (O21Δg) to the electron-rich double bond, progressing favorably through the concerted reaction mechanisms. The physical analyses of the frontier molecular orbitals agree well with the thermodynamic properties of the selected reagents, and the computed reaction rate parameters. The reactivity of monoterpenes with O21Δg follows the order of α-pinene > sabinene > limonene > β-pinene > camphene, i.e., α-pinene and camphene retain the highest and lowest reactivity toward singlet oxygen, with rate expressions of k(T) (M–1 s–1) = 1.13 × 108 exp(−48(kJ)/RT(K)) and 6.93 × 108 exp(−139(kJ)/RT(K)), respectively. The effect of solvent on the primary reaction pathways triggers a slight reduction in energy, ranging between 12 and 34 kJ/mol

Pressure Evolution of a Field Induced Fermi Surface Reconstruction and of the Neel Critical Field in CeIn3

We report high-pressure skin depth measurements on the heavy fermion material CeIn3 in magnetic fields up to 64 T using a self-resonant tank circuit based on a tunnel diode oscillator. At ambient pressure, an anomaly in the skin depth is seen at 45 T. The field where this anomaly occurs decreases with applied pressure until approximately 1.0 GPa, where it begins to increase before merging with the antiferromagnetic phase boundary. Possible origins for this transport anomaly are explored in terms of a Fermi surface reconstruction. The critical magnetic field at which the Neel ordered phase is suppressed is also mapped as a function of pressure and extrapolates to the previous ambient pressure measurements at high magnetic fields and high pressure measurements at zero magnetic field.Comment: 15 pages, 5 figure

Strategic intent, high-performance HRM, and the role of the HR director: an investigation into attitudes and practices in the country of Jordan

There is an implicit undercurrent in the HRM literature that the role of present day HR director has become ‘strategic’ as opposed to ‘routine’, as in the past. In this paper, we empirically test these assertions in the context of the country of Jordan—a context within which little past research into HRM has been undertaken. The design includes a detailed survey instrument sent to all financial firms within the country. We find that the reliance on routine functions has indeed fallen for HR directors surveyed; however, there is only weak evidence to support that the perceived importance of strategic functions has increased substantially. Results show that male HR directors and those longer serving, with higher qualifications, and those working for companies with lower employee turnover, are more likely to rate as ‘high’ the importance of the most strategic HR functions. Neither company size nor years of establishment moderated this relationship. The empirical evidence from this study—as one of a few conducted in non-Western environment—adds to the literature with some interesting implications and avenues for future work. Importantly, implications from our findings for strategic HRM and the role of the HR director are considered in conclusion

To What Extent Iron-Pnictide New Superconductors Have Been Clarified: A Progress Report

In this review, the authors present a summary of experimental reports on newly discovered iron-based superconductors as they were known at the end of 2008. At the same time, this paper is intended to be useful for experimenters to know the current status of these superconductors. The authors introduce experimental results that reveal basic physical properties in the normal and superconducting states. The similarities and differences between iron-pnictide superconductors and other unconventional superconductors are also discussed.Comment: 20 pages, 32 figures. Open selec

High-Field Fermi Surface Properties in the Low Carrier Heavy Fermion Compound URu2Si2

We performed the Shubnikov-de Haas (SdH) experiments of the low carrier heavy fermion compound URu2Si2 at high fields up to 34T and at low temperatures down to 30mK. All main SdH branches named alpha, beta and gamma were observed for all the measured field-directions (H // [001] -> [100], [100] -> [110] and [001] -> [110]), indicating that these are attributed to the closed Fermi surfaces with nearly spherical shapes. Anomalous split of branch alpha was detected for the field along the basal plane, and the split immediately disappears by tilting the field to [001] direction, implying a fingerprint of the hidden order state. High field experiments reveal the complicated field-dependence of the SdH frequencies and the cyclotron masses due to the Zeeman spin-splitting associated with the Fermi surface reconstruction in the hidden order state with small carrier numbers. A new SdH branch named omega with large cyclotron mass of 25m0 was detected at high fields above 23T close to the hidden order instabilities.Comment: 6 pages, 7 figures, accepted for publication in J. Phys. Soc. Jp