Search Results (22)

Due to changes in the German government’s energy concept, the amount of gypsum produced in flue gas desulfurisation plants (FGD gypsum) will fall from 5 million tons per year to 1 million tons or less by 2038 at the latest. As of 2016, FGD gypsum accounts for 55% of German gypsum mix. The resulting raw material gap must be closed through innovative recycling concepts, such as the processing of existing mine dumps. The process development aims to achieve a calcium sulfate dihydrate content of 85% and a reduction in the stockpile volume by 50%. The main components of the stockpiles are calcium sulfate in the form of gypsum stone as well as clay minerals and organic matter. Successful laboratory tests were transferred to a pilot scale jigging machine with dewatering screening. The process water is circulated throughout the entire process. The gypsum content in the heavy fraction is 76% when measured with ICP OES and 87% when measured via thermogravimetric methods. Furthermore, pilot-scale dry screening on the stockpile took place, and up to 1500 tons of material could be processed. Due to fluctuating weather conditions, the screening quality was subject to significant variations. Under optimal conditions, up to 60% of the feed could be recovered as gypsum stone; however, the screening process was nearly impossible during rain; therefore, a process combination of screening and a downstream jigging machine is recommended. Full article

This paper describes commonly used processes to produce aviation fuel and alternative routes with potential production yields for sustainable aviation fuels (SAF) like HEFA and ATJ. It also presents the possible sources (crude oil, refinery processes), causes (filter clogging, engine failure), and forms of contamination in both conventional and alternatively produced aviation fuels. Special attention is focused on the threats of fuel contamination with solid particles/trace elements, water, microorganisms, and fatty acid methyl esters (FAME). This review also presents the standard and novel advanced methods (ICP-MS, MALDI, ViPA) for identifying contaminations in aviation fuel. It also identifies possible ways to control and eliminate the risk of contamination, such as the fallowing coherent JIG system to ensure the quality of aviation fuel. Another approach that is very interesting and worth considering for future development is the idea of predictive maintenance and machine learning in monitoring and detecting contamination. Full article

Background: To investigate the effect of zirconium dioxide nanoparticles (ZrO₂NPs) on the shear bond strength (SBS) of hard denture lines bonded to different denture base resins. Methods: Five different denture bases were used in this study: conventional heat-cured resin, IvoCad, AvaDent, NextDent, and FormLabs, in acrylic specimens of 10 × 10 × 2.5 mm³ (N = 150, n = 10). Specimens were centered at the bottom of a silicon mold to create an auto-polymerized holder. Three major groups of reline material were used: no ZrO₂NPs (control), 2 wt.%, and 4 wt.% ZrO₂NPs. Reline was bonded to the resin surface using a customized jig. After polymerization, specimens were stored in distilled water, and 5000 thermal cycles were performed. Each specimen was fixed to an Instron machine, and SBS was tested using a blade loaded (1 mm/min) at the resin interface until failure. Data was collected and analyzed using two-way ANOVA and post hoc Tukey test (α = 0.05). Results: AvaDent showed the highest SBS when compared with other denture base materials (p < 0.001) except for IvoCad. The addition of ZrO₂NPs significantly decreased the SBS of AvaDent (p = 0.003) and IvoCad (p = 0.001), while heat polymerized resin, Formlabs, and NextDent showed no significant change in SBS (p > 0.05). Conclusion: CAD-CAM milled denture base resin showed higher SBS with pure denture reline. The addition of ZrO₂NPs decreased the SBS of reline with CAD-CAM milled denture base resins but did not change bond strength with 3D printed and conventional denture base resins. Full article

The interest in using new technologies to obtain recordings of on-water kinetic variables for assessing the performance of elite sprint kayakers has increased over the last decades but systematic approaches are warranted to ensure the validity and reliability of these measures. This study has an innovative approach, and the aim was to develop a new versatile jig including reference force sensors for both the calibration and validation of mutual static and dynamic stroke forces as measured with instrumented paddles at the high force levels used in elite sprint kayaking. Methods: A jig was constructed using a modified gym weight stack and a frame consisting of aluminum profiles permitting a fastening of custom-made kayak paddle shaft and blade support devices with certified force transducers combined with a data acquisition system to record blade and hand forces during static (constant load) and dynamic conditions (by paddle stroke simulation). A linear motion path incorporating a ball-bearing equipped carriage with sensors for the measurement of vertical distance and horizontal displacement was attached to the frame for recordings of various position measures on the paddle. The jig design with all components is extensively described to permit replication. The procedures for assessing the accuracy of the jig force instrumentation are reported, and with one brand of instrumented paddle used as an example, methods are described for force calibration and validation during static and dynamic conditions. Results: The results illustrate that the measured force with the jig instrumentation was similar to the applied force, calculated from the applied accurate mass (within a −1.4 to 1.8% difference) and similar to the force as calculated from the applied mass with the weight stack (within a −0.57 to 1.16% difference). The jig was suitable for the calibration and validation of forces in a range relevant for elite sprint kayaking under both static and dynamic conditions. During static conditions with a force direction equal to the calibration conditions and a force range from 98 to 590 N, all values for the instrumented paddle were within a −3.4 to 3.0% difference from the jig sensor values and 28 of 36 values were within ±2%. During dynamic conditions with paddle stroke simulations at 60 and 100 strokes/min and a target peak force of 400 N, the common force variables as measured by the instrumented paddle were not significantly different from the same measures by the jig (values at 100 strokes/min: peak force; 406.9 ± 18.4 vs. 401.9 ± 17.2 N, mean force; 212.8 ± 15.4 vs. 212.0 ± 14.4 N, time to peak force; 0.17 ± 0.02 vs. 0.18 ± 0.02 s, force impulse; 90.8 ± 11.2 vs. 90.5 ± 10.8 Ns, impulse duration; 0.43 ± 0.03 vs. 0.43 ± 0.03 s). Conclusion: A novel jig with several new functions is presented that enables the calibration and validation of force measurements with instrumented paddles by providing standardized conditions for calibration and force validation during both static and dynamic conditions in a force range relevant to elite sprint kayaking. Full article

The present work analyses the physical characteristics of aggregates recovered with the waterjigging process from comminuted concrete. In this work, conventional concrete (C16/20) was crushed to a top size of 20 mm with a jaw crusher and classified in a size range of 5 to 20 mm. The densimetric distribution analysis was carried out in a densimetric range of 2.4 to 2.8 g/cm³, and the cement paste was dissolved from all granulometric ranges to analyze the composition (sand, cement paste, and aggregates) of each part and define the possibilities of materials to recover. A two-stage water jig concentration process was used, generating a cleaner material in the first stage and a re-cleaner material in the second jigging stage. The physical properties of the material inserted in the feed and the material generated in the first and second stages were analyzed to compare them with natural aggregates. The results indicate the viability of recovering 47.8% of the coarse aggregates present in the concrete feed in the re-cleaner material, with 84% of particles having a density higher than 2.6 g/cm³. These characteristics are similar to those found in natural aggregates. Full article

The increasing concerns regarding water usage in mineral processing have led to a growing interest in dry jigging in recent years. However, there is still a need for a more comprehensive examination of the operational aspects of the technique. In this sense, this study focused on three main elements: (a) examining the air pulse pattern during dry jig operation; (b) assessing the evolution of the stratification profile over time using partition analysis; and (c) evaluating the specific energy consumption of batch dry jigging during operation. Also, an innovative operational strategy known as “transient pulsing” was proposed and analyzed, involving varying the intensity and frequency of the air pulse throughout the stratification process. All tests were conducted using density tracers spread across 11 density ranges (0.4–2.4 g/cm³) and a base bed (gravel) to analyze their separation in a batch, pilot-scale dry jig. Pressure drop and active power data were collected to measure the pulse characteristics and energy consumption. The airflow curves, obtained through pressure drop data, indicated that the pulsation process is more unstable as the airflow increases, possibly due to the pressure fluctuations experienced by air during valve closure. For the pulsation conditions used in the tests, the specific energy consumption was 10.66 Wh/kg of jigged material, with most of it related to the blower drive system. Analysis of the stratification evolution over time showed an oscillatory behavior, alternating between states of better (Ep < 0.1) and worse (Ep > 0.1) separation, especially for the near-gravity material (NGM). Results of the transient pulsation tests suggested that progressively increasing the vertical displacement of the bed during stratification resulted in slightly better segregation levels and more stable jigging evolution over time in comparison to stationary pulse conditions. Full article

This paper presents simulations of different concentration plants that use Inert Construction and Demolition Waste as feed to generate coarse aggregates from old concretes. Different feed materials were studied: CDW generated in Spain; low-strength concretes, C16/20, which are ordinary concrete used in civil construction; and high-strength concretes, C50/60, from specific demolitions, such as old viaducts and bridges. Granulometric and densimetric analyses were performed, and the composition of the granulometric fractions of the proposed concretes were analyzed based on previous studies carried out, to understand the materials that can be recovered and considered for reinvestment in the market. Investment analysis considering the CAPEX, OPEX, revenue, IRR, MIRR, NPV, and DPP of the different concentrating plants with varying streams of concentration to recover the materials of interest (coarse aggregates) are presented and discussed. The results of the analyses indicate greater viability in plants that use mobile plants and the use of water jigs. Full article

One of the most common coal preparations is enrichment in a jig using a float regulation system. The latest solutions propose to compensate for significant measurement errors of the float by introducing a radiometric density meter operating on the principle of gamma radiation absorption into the bottom product discharge zone of the jig. The signal from the radiometric density meter detector is in the form of a sequence of pulses with a Poisson time distribution, which are counted by a counter, as a form of digital low-pass filter. The requirement to maintain accuracy at an appropriate level forces the measurement time to be extended, which worsens the dynamic properties. Changes in the density of the coal–water medium have an unsteady, cyclical course, resulting from the principle of operation of the jig. The research goal was to develop an algorithm for processing the signal from the radiation detector using an IIR filter in the measurement path in a way that ensures optimization of the dynamic properties of the radiometric density meter operating in the control system of the coal enrichment process in the jig. For this purpose, a low-pass IIR filter was introduced into the measurement path to process the signal from the pulse counter. The identified course of the medium density for one cycle (the first) served as a reference signal. A first-order IIR filter was proposed, with a constant parameter selected on the basis of the reference signal and a parameter depending on the time derivative of the identified density of the medium. The mean squared error MSE was adopted as an indicator for assessing the dynamic properties of the radiometric density meter. The results of simulation tests showed that introducing an IIR filter into the measurement path gives better results in terms of the adopted criterion than using a counter with a constant measurement time. The best results (MSE = 2.05 × 10⁻⁴) were obtained using an IIR filter with a parameter that is a linear function of the derivative of the medium density over time, determined for one air pulsation cycle and applied in four subsequent cycles. These results were obtained for an adaptive first-order filter with a variable parameter a from the designated range from 0.833 to 0.999, for a measurement time of 2 ms. Full article

The European Union (EU) is responsible for generating quantities ranging from 310 to almost 700 million tons of construction and demolition waste (CDW) per year. Consisting of over 70% inert material (concrete, ceramics, plaster, bricks, and rocks), CDW can be recycled for various uses, and studies on the concentration of the materials of interest are necessary to improve the management of this material and reduce waste. In CDW recycling plants in Spain, there is a significant presence of limestone from old houses (a common material used in civil construction before new construction materials and technologies emerged) that were demolished and mixed with CDW that can be recovered for use as aggregates in concretes with process density concentration processes such as water jigging. The jigging process is based on the difference in density between materials, allowing the concentration of the densest material at the bottom of the jig. Concrete, conventional construction bricks, and rocks from old houses were taken separately and then were crushed and mixed based on binary and ternary tests, and each test was performed in this study by applying the jigging separation method. The physical characterization tests of these materials was carried out to observe the jigging performance in the concentration of rocks as well as the aggregates present in concrete. Binary tests (with two different materials) and ternary tests (with three different materials) were carried out to analyze the concentration of particles with a density greater than 2.55 g/cm³. The efficiency of jigging in the concentration of these materials was proven, and products were generated with more than 70% recovery of this material, with a concentration comprised of more than 95% rocks and concrete. Full article

This work provides historical information and examines changes in the methods and equipment used in gold recovery and processing operations. Alluvial gold recovery methods, mainly based on gravity separation combined with mercury (amalgamation), have been applied since the early days of mining. Historically, mining gold from the riverbeds was first implemented in Ancient Anatolia (also called “Asia Minor”) and Ancient Greece. As a first attempt to recover gold, the traditional immersion of sheepskin in river water to trap alluvial gold was developed. This technique has been considered a milestone in the famous myth of the Golden Fleece. Since then, gold extraction and processing technologies have evolved. In this respect, Emperor Augustus developed hydraulic gold mining during the period of the Roman Empire. Subsequently, the innovative machines of Georgius Bauer (Agricola) were widely used during the Renaissance, while Spanish colonialists in America improved their techniques by observing the efficient methods of the natives. Finally, the “American Gold Rush” era was perhaps the most crucial period of the alluvial gold mining process. It took place along the rivers of America during the 19th and 20th centuries. Today, in the technologically advanced society, various gold mining machines, including spiral and jig concentrators, provide higher production rates and less environmental harm. Full article

This paper presents the jig operating properties of the selected final parameters of the hard coal concentrate. The quality parameters of the product, such as the yield and ash content, were evaluated in terms of the technical and hydrodynamic parameters of the jig’s operation. The research program included a series of experiments in which the efficiency and the amount of hutch water were changed. The variables selected and analyzed were divided into two categories, i.e., one related to the characteristics of the concentrate produced, and the other to the characteristics of the jig operation. Models were built for narrowed particle size fractions based on concentrate yield and ash content in the concentrate. In addition, a multidimensional analysis was performed, considering variables such as machine throughput, which was determined by the flow rate of the material, the amount of hutch water, the quality of the concentrate, and the amount of concentrate, as well as the accuracy of the jig operation expressed by the imperfection. Two main parameters were taken into account for modeling the operation to examine their significance of influence on the final responses in terms of the possibility of adjusting the value of independent settings of the jig operation. The presented approach to modeling the operation of the jig can be extended by considering the impact of other parameters, taking into account the variability of the final effect, as long as it is allowed under the industrial conditions of machine operation and the assumed production requirements. The approach presented in this paper is a new technique, which was not found in the literature. Full article

Coal beneficiation processes are often based on gravitational enrichment techniques. Therefore, various types of jigs are often used in this area. A number of factors determine the quality of the final product. Therefore, proper and systematic monitoring of such a process is necessary. The present work examined the effect of the hutch water amount and the amount of processed coal (system capacity) on the yield and ash grade in individual density–size fractions. A statistical method in the form of the Kruskal–Wallis test and the Friedman test was used to evaluate the process. These tests were proposed as universal and reliable alternatives to classical analysis of variance (ANOVA) analysis. The performed analysis allowed for the determination of what process conditions should be selected in order to obtain certain effects. Therefore, it allowed us to apply certain combinations of hutch water amount, system capacity and particle characteristics to maximize the expected effects. The application of statistical analysis methods in the form of Kruskal–Wallis and Friedman tests to evaluate process efficiency creates new possibilities to monitor and optimize the jigging process in both context of amount and quality of final product and is very important not only for mining enterprise but also from an environmental point of view. Full article

Different fisheries, even the same fishery, use different ways of quantifying fishing efforts such as the number of vessels, days, voyages, and hooks. In squid-jigging fisheries, fishing hours, fishing days, and the number of vessels are valid units for calculating the catch per unit effort (CPUE). A vessel monitoring system (VMS) provides vessel position data with high spatial and temporal resolution and offers the possibility to quantify the CPUE at a finer scale. Using the squid fishery in the equatorial waters of the eastern Pacific as a case study, the CPUE was evaluated and standardized based on VMS data. The drifting operating points of the squid fishing vessels were filtered by the speed threshold, solar radiation, and operating time setting methods, leading to the number of fishing hours per day, and the nominal CPUE was calculated by combining the catch data obtained from logbooks. Then, the generalized linear model (GLM) and generalized additive model (GAM) were applied to conduct CPUE standardization considering spatiotemporal factors and environmental variables including sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH), and chlorophyll-a (Chl_a). The results showed that month, latitude, SST, SSH, and Chl-a all have a high significant effect on CPUE as demonstrated through the significance test conducted by GLM. The GAM including the significant factors was judged to be the best model according to the AIC guidelines. The latitude range for high CPUE in the fishery was 3°S~0°S, SST range 24~25 °C, SSH range 4~8 m, and Chl_a range 0.15~0.20 mg/m³. In addition, the nominal and standardized CPUEs were compared based on fishing hours and fishing days. The results indicated that the two types of CPUEs were highly related hence there was no significant difference. Full article

The use of recycled aggregates (RA) to replace natural aggregates (NA) in new concrete production has been pointed out as one of the main strategies to close the loop of construction materials. However, producing RA with properties similar to those of NA has been challenging, since current recycling methods struggle to remove contaminants like ceramics and mortar, whose presence impairs RA properties. In this study, a processing route consisting of a two-stage separation in hydraulic jig was tested, aiming to produce RA from a representative sample of Brazilian construction and demolition waste. All material streams generated in the tests were characterized in terms of composition, size distribution, density, shape index, and water absorption. The results indicated the possibility to produce a high-quality RA, containing more than 99.5% mass of concrete, with adequate properties to replace NA in new concrete production. Also, a conventional RA with suitable properties for downcycling uses (for example, base and sub-base material) could be obtained as a co-product. Finally, the results showed it was possible to recover more than 75% of the original concrete in Construction and Demolition Waste CDW, avoiding its disposal as waste. Full article

This paper discusses the fabrication and characterization of electrospun nanofiber scaffolds made of polystyrene (PS). The scaffolds were characterized in terms of their basis material molecular weight, fiber diameter distribution, contact angles, contact angle hysteresis, and transmittance. We propose an aligned electrospun fiber scaffold using an alignment tool (alignment jig) for the fabrication of highly hydrophobic (θ_W > 125°) and highly transparent (T > 80.0%) films. We fabricated the alignment jig to align the electrospun fibers parallel to each other. The correlation between the water contact angles and surface roughness of the aligned electrospun fibers was investigated. We found that the water contact angle increased as the surface roughness was increased. Therefore, the hydrophobic properties of the aligned electrospun fibers were enhanced by increasing the surface roughness. With the change in the electrospinning mode to produce aligned fibers rather than randomly distributed fibers, the transmittance of the aligned electrospun fibers increased. The increase in the porous area, leading to better light transmittance in comparison to randomly distributed light scattering through the aligned electrospun fibers increased with the fibers. Through the above investigation of electrospinning parameters, we obtained the simultaneous transparent (>80%) and hydrophobic (θ_W > 140°) electrospun fiber scaffold. The aligned electrospun fibers of PS had a maximum transmittance of 91.8% at the electrospinning time of 10 s. The water contact angle (WCA) of the aligned electrospun fibers increased from 77° to 141° as the deposition time increased from 10 s to 40 s. The aligned fibers deposited at 40 s showed highly hydrophobic characteristics (θ_W > 140°). Full article