Search Results (16)

Stope dilution is a major hidden cost driver for the underground operation, especially in terms of reducing ore quality, increasing the amount of processing feed, and effects on operational cost. Accurate calculation and consideration of planned and unplanned dilution and mining loss amounts are essential during mine planning. The user interface named D–Loss has been developed with MATLAB R2023b, which provides a multiparadigm numerical computing environment for faster and more practical calculation of these dilution amounts to address these challenges by quantifying dilution and linking them directly to economic and CO₂ emissions indicators. By determination and analysis of the stope overall dilution amounts, it helps us understand greenhouse gas emissions and ensures the efficient use of underground equipment. Calculation of stope dilution in a practical and rapid manner allows for stope design and operational improvements, which can help reduce dilution in underground operations. This progress is tracked through the D–Loss interface within the short- and long-term production planning. Moreover, by quantifying dilution impacts on comminution and haulage costs, D–Loss becomes a critical software for tracking economic losses and optimizing financial outcomes in the mining industry. D–Loss helps users iteratively assess the efficiency of updates and provides support in mine design, scheduling, and environmental impact control by comparing planning and operational improvements before and after. Full article

Granular samples are often used to characterize the pore structure of shale. To systematically analyze the influence of particle size on pore characteristics, case studies were performed on two groups of organic-rich deep shale samples. Multiple methods, including small-angle neutron scattering (SANS), low-pressure nitrogen gas adsorption (LP-N₂GA), low-pressure carbon dioxide gas adsorption (LP-CO₂GA), and XRD analysis, were adopted to investigate how the crushing process would affect pore structure parameters and the fractal features of deep shale samples. The research indicates that with the decrease in particle size, the measurements from nitrogen adsorption and SANS experiments significantly increase, with relative effects reaching 95.09% and 51.27%, respectively. However, the impact on carbon dioxide adsorption measurements is minor, with a maximum of only 8.97%. This suggests that the comminution process primarily alters the macropore structure, with limited influence on the micropores. Since micropores contribute the majority of the specific surface area in deep shale, the effect of particle size variation on the specific surface area is negligible, averaging only 16.52%. Shales exhibit dual-fractal characteristics. The distribution range of the mass fractal dimension of the experimental samples is 2.658–2.961, which increases as the particle size decreases. The distribution range of the surface fractal dimension is 2.777–2.834, which decreases with the decrease in particle size. Full article

Wood fuel from the agroforestry sector is one of the main strategies cited by the EU for reducing energetic dependance on foreign markets. Its sustainability, both economic and environmental, can be improved through the optimization of harvesting and chipping operations. This study was focused on the dynamic and energetic balance of the chipping phase carried out by a chipper operated by the power-take-off (PTO) of a medium-power tractor. Both machines were equipped with sensors for real-time monitoring of fuel consumption, PTO torque and speed, trunk diameter and working time during the comminution of 61 poplar trees grown in a medium rotation coppice system. The data analysis was carried out on the entire dataset (about 29,000 records) without considering their belonging to different trees. By means of proper data ordinations, it has been possible to define all the intervals in which the chipping stopped (e.g., between two trees) and to exclude them from the intervals of actual chipping. This has allowed forcomputation of operative and actual working time, as well as of the basic power required to operate the chipper and the power for actual chipping. Subsequently, the parameter values observed during actual chipping were related to the cutting diameters measured at the same instant. Subsequently, the dataset was divided according to seven diameter classes, and, for each class, the descriptive statistical indices of working time, work productivity, CO₂ emissions, energy requirement and fuel consumption were calculated. Eventually, the correlation between the variations in trunk diameter and other parameters was verified both on the whole dataset and based on the class average values. The analysis made it possible to identify the conditions of greatest efficiency for the chipper. More generally, the method could help to increase the accuracy of measurements aimed at characterizing the performance of chippers from the point of view of dynamic energy requirements as well as in relation to different wood species. Full article

Wollastonite (CaSiO₃) is the most researched and well-defined mineral in the field of CO₂ mineralization, but it is also a sought-after process mineral and thus, not easily justified for large scale ex situ carbon sequestration, which requires an energy-intensive step of comminution to increase reactivity. Wollastonite-rich mine tailings are a side stream with an already fine particle size resulting from the extractive process, but their effective utilization is problematic due to legislation, logistics, a high number of impurities, and chemical inconsistency. In this study, the accelerated weathering (aqueous carbonation) of high-calcite (CaCO₃) wollastonite tailings was studied under elevated temperatures and high partial pressures of CO₂ to determine the carbon sequestration potential of those tailings compared to those of pure reference wollastonite originating from the same quarry. The main process variables were pressure (20–100 bar), temperature (40 °C–60 °C), and time (10 min–24 h). Despite consisting largely of non-reactive silicates and primary calcite, very fine tailings showed promise in closed-chamber batch-type aqueous carbonation, achieving a conversion extent of over 28% in one hour at 100 bar and 60 °C. Full article

Exploiting renewable energy sources is one of the main strategies defined by the EU to overcome dependence on foreign markets for energy supply. Wood fuel sourced from the agroforestry sector can contribute significantly to achieving the goal, though its economic and environmental sustainability is intimately dependent on proper harvesting and chipping operations. In the present article, both economic and environmental aspects of Medium Rotation Coppice (MRC) were investigated regarding chipping. A small-scale chipper and tractor were equipped with real-time sensors to monitor time, t (s); fuel consumption, F (cm³); PTO torque, M (daNm); PTO speed, s (min⁻¹); and stem diameter, D (mm) during the comminution of 61 poplar plants (gathered in 5 classes according to trunk diameter) grown in MRC system. More than 29,000 records were taken and analyzed. Predictive models for working time, working productivity, CO₂ emission, energy consumption, fuel consumption and costs were also produced. Higher diametric classes exhibited lower fuel consumption, less CO₂ emission and less energy demand during chipping. Time and operating costs were statistically different among classes, with minimum values of 0.22 (SD ± 0.02) h·Mg⁻¹ and 12.07 (SD ± 0.93) €·Mg⁻¹ in class 5 and maximum values of 0.64 (SD ± 0.09) h·Mg⁻¹ and 35.34 (SD ± 4.88) €·Mg⁻¹ in class 1, respectively. Fuel consumption ranges from 3.04 (SD ± 0.88) L·Mg⁻¹ in class 5 to 7.32 (SD ± 1.46) L·Mg⁻¹ in class 1. The lowest CO₂ emission of 8.03 (SD ± 2.32) kg·Mg⁻¹ was found class 5. However, the total cost of coppice production did not exceed large-scale MRC production due to the lower purchase price of the machinery involved. Eventually, predictive models showed high reliability as estimating tools for important variables, such as working time, working productivity, CO₂ emissions, energy consumption, fuel consumption and costs. Full article

The technological development propitiates the rapid replacement of electrical and electronic equipment, which makes it indispensable to develop recycling processes for the treatment of this equipment when discarded. Printed circuit boards (PCBs) are fundamental components of electrical and electronic equipment. PCBs are composed of ceramics, polymers, and metals. Copper is the metal that is present in the greatest percentage of mobile phone PCBs. The objective of this study was to recover copper in the form of metallic deposits from a copper solution extracted from comminuted PCBs through supercritical CO₂ in the presence of cosolvents (H₂O₂ and H₂SO₄). A synthetic CuSO₄ solution was employed to determine the ideal current density in the range of 250 to 540 A/m². The electrowinning of the leachate solution from PCBs was performed at the determined current density. Using the current density of 250 A/m², pH equal to 4, and temperature of 25 °C, a current efficiency of around 100% was achieved for the real solution. The deposit obtained showed a copper concentration of 95.97 wt%, recovering 40% of the copper contained in the solution in 300 min of electrowinning. It was observed that for a longer electrowinning time, the percentage of copper recovery could increase. Full article

Polymer composites and blend systems are of increasing importance, due to the combination of unique and different material properties. Blending polybutylene terephthalate (PBT) with polycarbonate (PC) has been the focus of attention for some time in order to combine thermo-chemical with mechanical resistance. The right compounding of the two polymers is a particular challenge, since phase boundaries between PBT and PC lead to coalescence during melting, and thus to unwanted segregation within the composite material. Amorphization of the semi-crystalline PBT would significantly improve the blending of the two polymers, which is why specific miscibility aids are needed for this purpose. Recent research has focused on the functionalization of polymers with shape-anisotropic glass particles. The advantage of those results from their two-dimensional shape, which not only improves the mechanical properties but are also suspected to act as miscibility aids, as they could catalyze transesterification or act as crystallization modifier. This work presents a process route for the production of PBT-PC blends via co-comminution and an in-situ additivation of the polymer blend particles with anisotropic glass flakes to adjust the crystallinity and therefore enhance the miscibility of the polymers. Full article

The comminution of fuelwood for efficient transportation and handling exposes the material to various biological and chemical decomposition processes. The stockpiling of fuel chips can result in significant dry matter losses (DML) and consequent release of CO₂ into the atmosphere. The decomposition processes could be controlled by managing the chip moisture content (MC). MC control by utilizing the self-heating of stockpiled stemwood chips together with wind-driven ventilation was tested in a practical storage experiment, using uncovered and plastic-covered piles as references. The data were analyzed with linear mixed models. The predicted DML was 2.4–3.8% during the monitoring period of 5.9 months, but no significant differences appeared between the storage treatments. The increase in the basic density of the chips decreased DML. On average 1.7–3.5% of the recoverable energy content of the chips was lost during the experiment. The predicted average decline in the MC was ca. 4–8 percentage points (p.p.). The MC of the chip samples stored under plastic tarp was 4–5 p.p. lower than those stored in the uncovered piles. Heat generation within the piles was modest due to the high quality of the chips, and the ventilation solution tested only marginally affected the drying process and the mitigation of DML. Full article

This paper presents the research results of the effect of using calcium oxide and potassium permanganate on the combustion of pellets from wheat bran and beet pulp. The measurements were performed in the technical laboratory of the Centre of Energy Utilization of Non-Traditional Energy Sources in Ostrava. The research examined the effect of the use of chemical substances on the amount of air pollutants from biomass thermal conversion in a low-power boiler and the process temperature. First, we performed technical and elementary analyses of agricultural waste. The raw material was then comminuted, mixed with a selected additive, pelletized, and finally burned in a low-power boiler. The additive was added in three proportions: 1:20, 1:10, and 1:6.67 (i.e., 15%) relative to the fuel weight. The combustion process efficiency was measured using a flue gas analyzer and three thermocouples attached to the data recorder. From the measurement results, we were able to determine the percentage reduction of pollutant emissions into the atmosphere (CO, NO_x, and SO₂) due to the use of additives. Because emission standards are becoming increasingly stringent and fuel and energy prices are rising, the results presented in this article may be useful to agri-food processing plants that want to manage these materials thermally. Full article

In this study, two methods based on the use of diluted acids were developed: microwave-assisted wet digestion (MAWD) and microwave-assisted ultraviolet digestion (MAWD-UV). These methods are evaluated for the digestion of oral pharmaceutical drugs and further determination of elemental impurities from classes 1 (As, Cd, Hg and Pb) and 2A (Co, Ni and V) by inductively coupled plasma optical emission spectrometry (ICP-OES). Commercial drugs for the treatment of type 2 diabetes are used. No prior comminution is performed. For MAWD, the optimized conditions were 2 mol L⁻¹ or 3 mol L⁻¹ HNO₃, 1 mL of 50% H₂O₂ and a 45 min or 55 min irradiation program. For MAWD-UV, the condition using 1 mol L⁻¹ HNO₃, 1.6 mL of 50% H₂O₂ and a 55 min irradiation program enabled the digestion of all samples. In this way, efficient methods are proposed for the digestion of commercial pharmaceutical tablets for further determination of class 1 and 2A elemental impurities (ICH Q3D guidelines). Full article

Canada’s mineral reserves can play a very important role in curbing climate change if natural alkaline minerals are used for the process of mineral carbonation. In this work, the potential of using two Canadian natural silicates for accelerated carbonation is experimentally assessed: kimberlite mine tailing (Mg_0.846Al_0.165Fe_0.147Ca_0.067SiO_3.381) from the Northwest Territories, and mined wollastonite ore (Ca_0.609Mg_0.132Al_0.091Fe_0.024SiO_2.914) from Ontario. The aim of this work was to evaluate the weathering reactivity and CO₂ uptake capacity via carbonation of these two comminuted rocks, both of which are made up of a mixture of alkaline minerals, under process conditions that spanned from milder to intensified. Research questions addressed include: does kimberlite contain a sufficient amount of reactive minerals to act as an effective carbon sink; is dehydroxylation necessary to activate kimberlite, and to what extent does it do this; do secondary phases of wollastonite hinder its reactivity; and can either of these minerals be carbonated without pH buffering, or only weathered? Incubator, slurry, and pressurized slurry methods of accelerated weathering and carbonation were used, and the effect of the process parameters (temperature, solid-to-liquid ration, reaction time, CO₂ level, pH buffer) on the CO₂ uptake and crystalline carbonates formation is tested. The reacted samples were analyzed by pH test, loss-on-ignition test, calcimeter test, and X-ray diffraction analysis. Results showed that wollastonite ore (rich in fast-weathering CaSiO₃) is more suitable for accelerated carbonation than kimberlite tailing (containing slow-weathering hydrated magnesium silicates and aluminosilicates) when only its capability to rapidly form solid carbonates is considered. Incubator and pressurized buffered slurry methods proved to be most effective as under these conditions the precipitation of carbonates was more favorable, while the unbuffered slurry reaction conditions were more akin to accelerated weathering rather than accelerated carbonation. Full article

Animal manure represents a major source of renewable energy that can be converted into biogas using anaerobic digestion. In order to most efficiently utilize this resource, it can be co-digested with energy dense, high biomethanation potential feedstocks such as energy crops. However, such feedstocks typically require pretreatments which are not feasible for small-scale facilities. We investigated the use of single-stage and the sequential co-digestion of comminuted but otherwise non-pretreated Salix with animal manure, and further investigated the effects of coppicing frequency and clone choice on biomethanation potential and the area requirements for a typical Swedish farm-scale anaerobic digester using Salix and manure as feedstock. In comparison with conventional single-stage digestion, sequential digestion increased the volumetric and specific methane production by 57% to 577 NmL L⁻¹ d⁻¹ and 192 NmL (g volatile solids (VS))⁻¹, respectively. Biomethanation potential was the highest for the two-year-old shoots, although gains in biomass productivity suggest that every-third-year coppicing may be a better strategy for supplying Salix feedstock for anaerobic digestion. The biomethane production performance of the sequential digestion of minimally pretreated Salix mirrors that of hydrothermally pretreated hardwoods and may provide an option where such pretreatments are not feasible. Full article

Centella asiatica has been included in Thai traditional medicinal plants and recipes, as a well-established historical use as a vegetable and tonic. However, when applied in modern formulations, the progressive degradation of the plant pigments occurs, causing color-fading and color variation in the products. Depigmentation of the comminuted sample using supercritical carbon dioxide (scCO₂) fluid extraction with a cosolvent was introduced as a pretreatment to solve the color-fading problem. The contents of compounds with known biological activities and the wound healing activities (antioxidant screening by DPPH and ABTS⁺ scavenging activities; cell migration assay; matrix metallopeptidase [MMP]-2 inhibition on human skin fibroblast; endothelial cell tube formation assay) of the C. asiatica leaf extracts obtained by conventional ethanolic extraction (CV) and pretreatment using scCO₂ extraction, were determined. Total triterpenoids (madecassoside, asiaticoside B, asiaticoside, madecassic acid, terminolic acid and asiatic acid) and total triterpenoid glucosides (madecassoside, asiaticoside B and asiaticoside) were notably more abundant in the extract that had been pretreated using scCO₂ than the extract obtained by CV. Moreover, the scCO₂ pretreatment not only caused greater relative MMP-2 inhibition (58.48 ± 7.50% of the control), but also exhibited a higher cell migration (59.83 ± 1.85% of the initial) and number of vessels (18.25 ± 4.58) of angiogenesis in the wound healing process. Additionally, positive correlations were observed between the DPPH antioxidant activity and madecassoside content (r = 0.914, p < 0.01), as well as between the cell migration activity and asiaticoside content (r = 0.854, p < 0.05). It can be concluded that the scCO₂ pretreatment of C. asiatica can eliminate color pigments from the extract and improve its in vitro wound healing activity. Full article

Mathematical models of particle size distribution (PSD) are necessary in the modelling and simulation of comminution circuits. In order to evaluate the application of the Swebrec PSD model (SWEF) in the grinding circuit at the Punta Gorda Ni-Co plant, a sampling campaign was carried out with variations in the operating parameters. Subsequently, the fitting of the data to the Gates-Gaudin-Schumann (GGS), Rosin-Rammler (RRS) and SWEF PSD functions was evaluated under statistical criteria. The fitting of the evaluated distribution models showed that these functions are characterized as being sufficiently accurate, as the estimation error does not exceed 3.0% in any of the cases. In the particular case of the Swebrec function, reproducibility for all the products is high. Furthermore, its estimation error does not exceed 2.7% in any of the cases, with a correlation coefficient of the ratio between experimental and simulated data greater than 0.99. Full article

In this study, the feasibility of co-grinding and the subsequent thermal rounding to produce spherical polymer blend particles for selective laser sintering (SLS) is demonstrated for polybutylene terephthalate (PBT) and polycarbonate (PC). The polymers are jointly comminuted in a planetary ball mill, and the obtained product particles are rounded in a heated downer reactor. The size distribution of PBT–PC composite particles is characterized with laser diffraction particle sizing, while the shape and morphology are investigated via scanning electron microscopy (SEM). A thorough investigation and characterization of the polymer intermixing in single particles is achieved via staining techniques and Raman microscopy. Furthermore, polarized light microscopy on thin film cuts enables the visualization of polymer mixing inside the particles. Trans-esterification between PBT and PC during the process steps is investigated via vibrational spectroscopy and differential scanning calorimetry (DSC). In this way, a new process route for the production of novel polymer blend particle systems for SLS is developed and carefully analyzed. Full article