Thermodynamics and Kinetics Research of the Fluorination Process of the Concentrate Rutile

The growth in the production of titanium metal and its compounds leads to an increase in the amount of toxic waste. As a result, at the legislative level, emissions of such wastes are limited, which leads to a drop in the production of titanium-containing products and a shortage of titanium in the international market. This paper presents the results of the process of fluorination of rutile concentrate from the Tarsky deposit (Russia, Omsk region) with elemental fluorine using a laboratory setup of a special design. For fluorination, samples of rutile concentrate weighing 0.1–1.0 g were used. The particle size distribution of particles varied from 2 × 10−6 to 2 × 10−5 m. To determine the possibility of carrying out the process, the calculation of the change in the logarithm of the equilibrium constant versus temperature was performed. The influence of the following operating parameters on the fluorination process has been studied: various concentrations of F2 in a fluorinating mixture of fluorine with nitrogen; process time from 0 to 9 min; different ratios of the initial solid phase to fluorine (10 and 50% excess of fluorine and 10 and 50% of its deficiency); fluorination temperature in the range of 300–1800 K. A kinetic equation is selected that most accurately describes the fluorination process. The values of the activation energy and the preexponential factor in the kinetic equation are determined. The obtained results show that with an increase in the fluorine content in the fluorinating gas mixture and the temperature of the process, the fluorination rate increases. Optimal conditions for fluorination: temperature—680 K; time—5 min excess fluorine in the fluorinating mixture—20–25%. The obtained results allow to propose and consider the conditions of process execution on industrial equipment.

Evaluation of particle board production from cotton gin waste and urea-formaldehyde resin

The objective of this study was the evaluation of feasibility of producing particleboard for general use using cotton gin waste generated in Argentina and urea formaldehyde resin. The chemical composition and size distribution of particles of the ginning residue as well as mechanical and physical properties of the particleboards obtained were investigated. Density and flexural strength of particleboards produced with varying levels of urea-formaldehyde resin between 8.3 and 19.3% (solid to solid ratio) were evaluated. The effect of incorporating jute reinforcement on the mechanical properties of these boards was also analyzed. Particle boards with densities between 530 and 700 kg/m3 and variable flexural strength between 0.30 and 5.85 MPa were obtained, allowing the minimum levels required for low-density boards to be reached.

Large hemispheric difference in nucleation mode aerosol concentrations in the lowermost stratosphere at mid- and high latitudes

The details of aerosol processes and size distributions in the stratosphere are important for both heterogeneous chemistry and aerosol–radiation interactions. Using in situ, global-scale measurements of the size distribution of particles with diameters > 3 nm from the NASA Atmospheric Tomography Mission (ATom), we identify a mode of aerosol smaller than 12 nm in the lowermost stratosphere (LMS) at mid- and high latitudes. This mode is substantial only in the Northern Hemisphere (NH) and was observed in all four seasons. We also observe elevated SO2, an important precursor for new particle formation (NPF) and growth, in the NH LMS. We use box modelling and thermodynamic calculations to show that NPF can occur in the LMS conditions observed on ATom. Aircraft emissions are shown as likely sources of this SO2, as well as a potential source of nucleation mode particles directly emitted by or formed in the plume of the engines. These nucleation mode particles have the potential to grow to larger sizes and to coagulate with larger aerosol, affecting heterogeneous chemistry and aerosol–radiation interactions. Understanding all sources and characteristics of stratospheric aerosols is important in the context of anthropogenic climate change as well as proposals for climate intervention via stratospheric sulfur injection. This analysis not only adds to the, currently sparse, observations of the global impact of aviation, but also introduces another aspect of climate influence, namely a size distribution shift of the background aerosol distribution in the LMS.

Examination of ultraviolet germicidal radiation for inactivating microorganisms in melted snow and ice samples

<p>The storage of melted snow and/or ice samples from snow pits and ice cores in a refrigerator for long durations may be limited by an increase in particle concentration caused by microbial growth after approximately 1–2 weeks. In this study, we examined an ultraviolet (UV) disinfection method for the storage of melted snow and/or ice samples. Surface snow obtained from Glacier No. 31 in the Suntar-Khayata Range, eastern Siberia, Russia was divided into two portions for UV treatment and untreated controls. Particle concentrations in the samples were measured using a Coulter counter (Multisizer 4e; Beckman Coulter, USA). Whereas the particle concentration in untreated samples increased, no obvious increase was observed over 53 days in the samples subjected to UV treatment. In addition, the original particle concentrations were unaffected by UV treatment. These findings indicate that the antimicrobial effect of UV radiation is effective for long-term sample storage of melted water samples. A detailed analysis of the particle size distribution for untreated samples indicated that particles of 0.7–1.2 µm appeared within the first 7–14 days. Measurements using a viable particle counter (XL-10BT2 and XL-28A1; RION Co. Ltd., Japan) confirmed that these were biological particles, suggesting that microbial growth occurs during this period. Subsequently, the particles shifted to a smaller size and a higher concentration, suggesting that the decomposition of microorganisms occurred in the water samples. Therefore, the size distribution of particles in untreated samples reflected the growth and decomposition of microorganisms over time.</p>

STUDY OF MECHANOACTIVATION EFFECTIVENESS OF GRANITE SCREENING IN MILLS OF VARIOUS TYPES WHEN SYNTHESIS OF NANOSTRUCTURED BINDER

In this paper, the possibility of obtaining nanostructured binders (NB) based on acidic igneous intrusive rocks is considered by the example of screening out granite using milling units of different types, followed by an assessment of the degree of effectiveness of their application for this type of aluminosilicate raw material. A comparative analysis of the degree of mechanoactiva-tion impact of them is carried out. A comparative analysis of the microstructure of samples of granite screening, crushed in three different milling units has been realized. It has been found that the type of milling unit significantly affects not only the degree of dispersion and the nature of the particle size distribution of particles, but also on morphological features of them. It was revealed that the most effective milling unit for obtaining (synthesizing) a binder system from granite screening is a ball mill, as the content of nano- and micro-level particles in this system are maximum, which ultimately determines its quality as a binder. The analysis of the structural, morphological, and strength characteristics of NB obtained from the granite screening in a ball mill, which is following similar data on a quartz NB and allow us to speak about the effectiveness of the use of a ball mill is a grinding machine and granite screening as a raw component for the synthesis of NB.

MODELLING OF THE BREAK UP MECHANISM IN GAS ATOMIZATION OF LIQUID METALS

An integrated model of the atomization of a liquid column perturbed by a flowing gas phase is proposed. The algorithm termed Surface Wave Formation (SWF) is based on the concept of the formation of sinusoidal waves travelling along the surface of the liquid. The amplitude of such instabilities can grow exponentially under specific conditions, effectively causing the detachment of liquid particles either by shearing of part of a wave crest or by detachment of a liquid body at negative amplitude nodes. The SWF model covers both primary and secondary atomization and can in principle describe the break up of any well defined liquid shape. Model predictions compare favourably with experimental data from close coupled atomization of metals. The implications of the SWF algorithm are important, since - unlike empirical correlations - it can predict the size distribution of particles inside a spray in space and atomization time. Future integration could include calculations of cooling histories of drops in flight.

Effect of different sediment dewatering techniques on subsequent particle sizes in industrial derived effluent

A paucity of literature has compared geotextile dewatering methods to more conventional dewatering methods (i.e., centrifuge, sedimentation) in the context of how geotextile dewatering performs at reducing particulate matter in dewatering effluent. Particulate matter is the primary source of inorganic and organic contaminants (i.e., dioxins and furans) in an unconsolidated sediment (estimated 577 000 m3) that has accumulated in a wastewater stabilization basin in Nova Scotia, Canada. Physical and chemical properties of contaminated sediment were initially characterized, and subsequent laboratory experiments were carried out for three common dewatering methods: sedimentation, centrifugation, and geotextile filtration. Filtrate quality of suspended solids (number, particle size distribution of particles) was examined for differences based on three dewatering techniques assessed. All three methods provided effective removal of particulate matter during dewatering, but geotextile dewatering could be a more cost-effective and practical solution for dewatering of these sediments.

Dust size and spatial distributions in debris discs: predictions for exozodiacal dust dragged in from an exo-Kuiper belt

ABSTRACT The spectral energy distributions of some nearby stars show mid-infrared (IR) excesses from warm habitable zone dust, known as exozodiacal dust. This dust may originate in collisions in a planetesimal belt before being dragged inwards. This paper presents an analytical model for the size distribution of particles at different radial locations in such a scenario, considering evolution due to destructive collisions and Poynting–Robertson (P–R) drag. Results from more accurate but computationally expensive numerical simulations of this process are used to validate the model and fit its free parameters. The model predicts 11 μm excesses (R11) for discs with a range of dust masses and planetesimal belt radii using realistic grain properties. We show that P–R drag should produce exozodiacal dust levels detectable with the Large Binocular Telescope Interferometer (LBTI) ($R_{11} \gt 0.1{{\ \rm per\ cent}}$) in systems with known outer belts; non-detection may indicate dust depletion, e.g. by an intervening planet. We also find that LBTI could detect exozodiacal dust dragged in from a belt too faint to detect at far-IR wavelengths, with fractional luminosity f ∼ 10−7 and radius ∼10–80 au. Application to systems observed with LBTI shows that P–R drag can likely explain most (5/9) of the exozodiacal dust detections in systems with known outer belts; two systems (β Uma and η Corvi) with bright exozodi may be due to exocomets. We suggest that the three systems with exozodiacal dust detections but no known belt may have cold planetesimal belts too faint to be detectable in the far-IR. Even systems without outer belt detections could have exozodiacal dust levels $R_{11} \gt 0.04{{\ \rm per\ cent}}$ which are problematic for exo-Earth imaging.