Granular Dust Research Articles

Design of Innovative High-Performance Polymer for Passive Lunar Dust Mitigation

Dust in space environments is now recognized as a major concern for successful manned and robotic exploration and colonization missions. Indeed, a thin layer of dust covers the lunar surface made of loose granular material, consisting of a broad range of shapes, sizes, and types of sediments, which mainly consists of silicate minerals in the form of micrometric, sharp, abrasive, porous, chemically reactive dust particles. The aim of this paper is to present preliminary results related to the design and development of an innovative, lightweight, high-performance polymer with an elevated strength-to-weight ratio able to mitigate particle contamination. In detail, dust mitigation or the minimization of the surface energy and consequently the adhesion forces among the external layers and the granular dust micrometric particles can be achieved through modifications of the surface properties by means of both chemical and physical methodologies. The proposed approach, to realize an innovative material and not a hydrophobic coating, is potentially applicable to a wide range of technological conditions and it relies on reproducible and controllable chemical modifications of the material’s surface properties through the design and synthesis of suitable base materials i.e., aromatic polyimides and copolyimides and incorporation of special low molecular weight additives, i.e., surface migrating agents, loaded directly within the reacting mixture during the intermediate phases of the copolymerization. The materials investigated in this work exhibit mechanical properties able to withstand the extreme space environment conditions and an elevated non-sticking behaviour of its surface layers in contact with granular, micrometric dust particles of lunar regolith i.e., abhesion capacity.

Комплексная электротермическая переработка пылей производства ферромарганца

This study investigates the feasibility of recovering ferroalloy from dust produced during the smelting of ferrosilicon manganese at the Taraz Metallurgical Plant LLP. Typically, the dust comprises (%wt.): MnO - 53.3; SiO 2 - 24.0; MgO - 5.4; CaO - 9.6; Al 2 O 3 - 3.8; Fe 2 O 3 - 1.5; ZnO - 1.8; PbO - 0.6. To determine the optimal process parameters, thermodynamic modelling was deployed using the HSC-5.1 software package to analyse results from a second-order rotatable experimental design (a Box-Hunter design). Dust was pelletised in a bowl granulator followed by electric smelting in combination with coke and steel chips in a single-electrode arc furnace with a power of up to 15 kV×A; the steel chips were added as a source of iron. The study shows that at equilibrium in the presence of iron, components of the dust reacted with carbon forming manganese silicides and FeSi at temperatures above 1300 º C and 1400 º C, respectively. By increasing the amount of carbon in the charge from 14 to 30% by weight of dust, the extraction of silicon and manganese into the alloy is increased to 44.7 and 92%, respectively, at a temperature of 1800 º C. The MnC22 and MnC25 grades of ferrosilicon manganese are obtained when the amount of carbon is equal to 20-30% by weight of dust, allowing 56.4-79.3% of Si and 67.7-84.3% of Mn to be extracted into the alloy over the temperature range of 1600-1800ºC. The time taken for electric smelting of the dust is reduced by 16-18% by increasing the amount of both carbon from 18 to 36% and steel chips from 2 to 6% which resulted in a corresponding increase in the extraction of Si and Mn into the alloy from 20.9 to 60% and 68.3-82.1%, respectively. Thermodynamic modelling of the system at equilibrium was deployed to determine the temperature effect on the distribution of silicon, manganese, zinc and lead in the "dust components - carbon - iron" system, the extraction efficiency of silicon, manganese and iron into ferroalloy, and the content of these metals in the alloy. The electric smelting produces grade MnC22 of ferrosilicon manganese from a combination of granular dust, 30% coke and 6% steel chips resulting in an alloy containing silicon and manganese at 20.5 and 65.8%, respectively.

FLOWABILITY OF DUSTS FROM DRY OFF-GAS CLEANING: THE INFLUENCE OF PARTICLE SIZE AND THE SPREAD OF THE SIZE DISTRIBUTION

Considerable amounts of fine granular dust result from dry off-gas cleaning systems. The flowability of these dust is an important characteristic for the design of dust-conveying and storage equipment. In this study, the relationship between the flow-relevant properties unconfined yield strength and flowability and important properties of the dust (Sauter mean diameter, the spread of the size distribution) were investigated based on the data of seventy specks of dust from dry off-gas cleaning systems. The results showed that the Sauter mean diameter of a dust from dry off-gas cleaning can be used as the basis for a rough estimate of the unconfined yield strength and the flowability. As is well-known, for coarser dust the unconfined yield strength is typically lower and the flowability is higher. The influence of the spread of the size distribution is comparatively low. However, to obtain reliable flowability data shear tests are obligatory. Article DOI: https://dx.doi.org/10.20319/mijst.2017.32.2632 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Biopersistent Granular Dust and Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

ObjectiveApplying a systematic review to identify studies eligible for meta-analysis of the association between occupational exposure to inorganic dust and the development of chronic obstructive pulmonary disease (COPD), and conducting a meta-analysis. Data SourcesSearches of PubMed and Embase for the time period 1970–2010 yielded 257 cross-sectional and longitudinal studies on people exposed to inorganic dust at the workplace with data on lung function. These studies were independently abstracted and evaluated by two authors; any disagreement was resolved by a third reviewer. Of 55 publications accepted for meta-analysis, 27 investigated the effects of occupational exposure to biopersistent granular dust (bg-dust).MethodsA random effects meta-analysis allowed us to provide an estimate of the average exposure effect on spirometric parameters presented in forest plots. Between-study heterogeneity was assessed by using I2 statistics, with I2>25% indicating significant heterogeneity. Publication bias was investigated by visual inspection of funnel plots. The influence of individual studies was assessed by dropping the respective study before pooling study-specific estimates.ResultsThe mean FEV1 of workers exposed to bg-dust was 160 ml lower or 5.7% less than predicted compared to workers with no/low exposure. The risk of an obstructive airway disease—defined as FEV1/FVC < 70%—increased by 7% per 1 mg· m-3 respirable bg-dust. ConclusionOccupational inhalative exposure to bg-dust was associated with a statistically significant decreased FEV1 and FEV1/FVC revealing airway obstruction consistent with COPD.

Induction of altered mRNA expression profiles caused by fibrous and granular dust

Natural and synthetic fibres and particles are being introduced into the workplace and environment daily. Comparative analyses of the induced signalling pathways are essential in order to understand the potential hazards of these particles. To identify the molecular characteristics of particles and fibres, we selected crocidolite and chrysotile asbestos as representatives for fibered dust and titanium dioxide (TiO2) (100-200nm), zirconium dioxide (ZrO2) (50-100nm) and hematite (Fe2O3) (20nm) as representatives for bio-persistent granular dust. SV-40 virus-transformed human bronchial epithelial cells (BEAS-2B) were exposed to well-defined fibres and particles. RT2 Profiler™ PCR Array Human Stress & Toxicity PathwayFinder was used to compare the relative mRNA expression of 84genes. A detailed characterization of the dust samples used in this study was accomplished to ensure comparability to other studies. Investigation of mRNA expression of 84 signalling molecules attributed to pathways such as DNA damage and repair; oxidative/metabolic stress; growth arrest and senescence; inflammation, proliferation and carcinogenesis; and heat shock and apoptosis revealed that crocidolite and chrysotile asbestos induced mRNA expression of pathway molecules involved in proliferation and carcinogenesis, as well as inflammation. Titanium dioxide, zirconium dioxide and hematite mainly induced pathway molecules responsible for oxidative/metabolic stress and inflammation. Our findings suggest that the hazards of fibered dust mainly include the induction of direct toxicity by altering signalling pathways such as carcinogenesis and proliferation, while granular dust shows indirect toxicity by altering signalling pathways involved in inflammatory processes. PCR arrays, therefore, may be a helpful tool to estimate the hazard risk of new materials.

Commentary to Gebel 2012: A quantitative review should apply meta-analytical methods—and this applies also to quantitative toxicological reviews

Gebel (In Arch Toxicol 87(5):923-924, 2013) replied to my Letter to the Editor (Morfeld in Arch Toxicol 87(5):921, 2013) in which I criticized the quantitative review of inhalation rat studies on the association of granular biopersistent dust exposures and lung cancer risk (Gebel in Arch Toxicol 86(7):995-1007, 2012). My methodological comments were not understood. The Editors of the Archives invited me to detail and substantiate my criticism. The main issues are as follows: (1) A quantitative summary of the study results was performed without weighting for precision of the single studies (the published unweighted synthesis is potentially biased). (2) No heterogeneity assessment was performed before combining the findings (it is unclear whether overall summaries are sensible). (3) Correlation coefficients were used (correlations are distorted estimates of exposure-response and misleading). (4) An incomplete input data table was published (no transparent reporting, no replication possible for the reader). The quantitative synthesis by Gebel (In Arch Toxicol 86(7):995-1007, 2012) does not fulfil the usual requirements of a scientific quantitative review and should be replaced by an appropriate meta-analysis.

407 Chronic-obstructive pulmonary disease (COPD) caused by inhalation of inorganic dust at the workplace - Systematic Review and Metaanalysis

ObjectiveA systematic review of the scientific medical literature on COPD and the inhalative exposure to inorganic dust and a metaanalysis.MethodsThe search was done in Medline/EMBASE. The quality of selected papers...

Regeneration of granular-filter dust collectors

Mechanisms and appropriate engineering solutions are considered for improving various methods for regenerating granular dust collectors. Model interpolation calculations for evaluating the efficiency of the recommendations developed are proposed and tested in practice.

Total and Fractional Performance of Granular Dust Traps in Refractory Production

Methods are proposed for designing interpolation models for the preliminary determination and subsequent forecasting of general and fractional breakthrough coefficients for dust used with granular filters, as employed in energy-saving and high-performance dust trapping from technological gases and ventilation discharges in refractory production. The models are supplied with nomograms, which makes them widely suitable for experts working in environmental protection at refractory-producing organizations. The main factors are identified that influence the performance. The results are of interest to experts in related areas of industry such as building materials and engineering ceramics and so on.

Appearance of Mechanical Zinc Coatings and Superficial Pore Sealing Treatment

By using SnSO4 water solution to activate global granular Zn powders of 325 screen mesh, Zn-Sn composite coverage is formed under the action of mechanical impact of the tiny glass beads and work pieces. During and after the formation of coating, acid water liquor will react with metal basal body, and hydrogen gas is bound to emit from the pathway and form micro pores. In addition, there are bond areas between the new and the primary coverage, which may lead to the emergence of micro crack on the coating owing to such causes as too big or uneven impact during plating process, little distortion of global granular zinc dust inside the plating coat, less tight coalescent of the zinc dust flecks. These problems can be confirmed by SEM scanning coating surface and cross section pictures of plating coat. In our study, methyl hydrogen silicone fluid, titanium isopropoxide and benzinum are used as the basal components. This compound has such features as better osmosis for micro pores and cracks formed in the process of dual coverage, strong adhesive force, anti-contraction, high transparence and water proof property. The impact of titanium isopropoxide dosage on the solidifying speed of methyl hydrogen silicone fluid, and that of mechanical plating zinc coating on corrosion proof are studied. Through tests, the proper compound ratio is determined as 11:10:79 of methyl hydrogen silicone fluid to titanium isopropoxide to benzinum(90-120 Centigrade degree). Experiments indicate that when the coating thickness is 0.2 micron, the emergence time of white corrosion on the plating coat doubles, accordingly, that of red rust prolongs, this shows that the anticorrosion of the coverage can be significantly improved through superficial pore sealing in zinc plating coat.

Results of current intraperitoneal carcinogenicity studies with mineral and vitreous fibres

The study includes some 50 groups of male or female Wistar rats tested in three series. Except for one untreated group and 3 vehicle control groups, the animals were injected intraperitoneally (i.p.) once or repeatedly with dust suspensions and then examined, after lifetime observation up to 30 months, for tumours in the abdominal cavity. 1 granular dust (silicon carbide), 2 asbestos dusts (crocidolite, tremolite) and 11 vitreous fibre dust samples were administered. 5 of the vitreous fibre types were fine fibre fractions from 4 commercial insulation wools and 1 experimental wool, the others were prepared by milling glass microfibres, which have, per se, a small diameter range. The dosage per rat differed over a wide range in accordance with experience from earlier studies. The lowest dose was 0.04 x 10(9) crocidolite fibres in 0.5 mg dust, and the highest amounted to 20 x 10(9) glass fibres in 1000 mg divided into 40 weekly injections. Two mesotheliomas were found in a total of 395 rats treated with saline or granular silicon carbide (250 or 1000 mg). Eleven fibre dusts produced dose-dependent mesotheliomas at rates of up to 97 %, but the calculated fibre number > 5 micrometers in length required for inducing a 25 % tumour risk differed between the fibre samples tested in the relation of 1 to about 1000. UICC-like crocidolite heads the ranking order; the glass fibre B-01, which possesses a low durability in the body, ends it together with a rather thin sample of glass fibre type B-09. The stone fibre MMVF-21 takes a high place in the ranking order, similar to the tremolite sample. The results correspond to those of earlier i.p. tests.

A granular dust filter for the exhaust gases of drying drums

A granular dust filter for the exhaust gases of drying drums