Mechanical Comminution Research Articles

Influence of blasting charge distribution on the energy required for communition of rock

The most energy-intensive process in the mining industry is particle size reduction - comminution. The first phase of this process is blasting to fragment the rock from the initial Boussinesq's half-space size. Scientific literature demonstrates that the output of a blast in terms of fragment size distribution can be manipulated by varying the specific charge (powder factor) and charge distribution. This study focuses on the influence of blasting on the internal resistance of the blasted fragments; in particular the influence of the spatial distribution of charges. Small-scale blasts were performed on 14 marble blocks using different powder factors and charge distributions. Three control blocks were fragmented by mechanical means for comparison. The results show the correlations between charge distributions and the specific energy of mechanical comminution. Opportunities for adjusting charge diameter and distribution in opencast blasts to improve the performancet of comminution circuits are discussed.

Sourcing and long-range transport of particulate organic matter in river bedload: Río Bermejo, Argentina

Abstract. Fluvial transport of organic carbon from the terrestrial biosphere to the oceans is an important term in the global carbon cycle. Traditionally, the long-term burial flux of fluvial particulate organic carbon (POC) is estimated using river suspended sediment flux; however, organic carbon can also travel in river bedload as coarse particulate organic matter (POMBed). Estimates of fluvial POC export to the ocean are highly uncertain because few studies document POMbed sources, flux, and evolution during long-range fluvial transport from uplands to ocean basins. This knowledge gap limits our ability to determine the global terrestrial organic carbon burial flux. In this study we investigate the flux, sources, and transformations of POMBed during fluvial transport over a ∼1300 km long reach of the Río Bermejo, Argentina, which has no tributary inputs. To constrain sourcing of POMBed, we analyzed the composition and stable hydrogen and carbon isotope ratios (δ2H, δ13C) of plant wax biomarkers from POMBed at six locations along the Río Bermejo and compared this to samples of suspended sediment, soil, leaf litter, and floating organic debris (POMfloat) from both the lowland and headwater river system. Across all samples, we found no discernible differences in n-alkane average chain length or nC29 δ13C, indicting a common origin for all sampled POMBed. Leaf litter and POMfloat nC29 δ2H values decrease with elevation, making it a useful proxy for POMBed source elevation. Biomarker δ2H values suggest that POMBed is a mix of distally derived headwater and locally recruited floodplain sources at all sampling locations. These results indicate that POMBed can be preserved during transport through lowland rivers for hundreds of kilometers. However, the POMBed flux decreases with increasing transport distance, suggesting mechanical comminution of these coarse organic particles and progressive transfer into the suspended load. Our provisional estimates suggest that the carbon flux from POMBed comprises less than 1 % of the suspended load POC flux in the Río Bermejo. While this represents a small portion of the river POC flux, this coarse, high-density material likely has a higher probability of deposition and burial in sedimentary basins, potentially allowing it to be more effective in long-term CO2 drawdown relative to fine suspended particles. Because the rate and ratio of POMBed transport versus comminution likely vary across tectonic and climatic settings, additional research is needed to determine the importance of POMBed in the global carbon cycle.

Influence of mechanical comminution of raw materials and PEF treatment on the aqueous extraction of phenolic compounds from artichoke wastes

In this study the combined effect of mechanical comminution and pulsed electric fields (PEF) treatments on both cell disintegration and extractability of phenolic compounds during aqueous extraction from artichoke external bracts, was investigated. Different-sized bract discs were treated with varying PEF conditions, namely 0.5–5 kV/cm of electric field strength (E), and 1–20 kJ/kg of total specific energy input (WT). The cell disintegration index (Zp) of bract tissues, as well as the total phenolic content (TPC) and antioxidant activity (FRAP) of the extracts, were assessed.The results showed that increasing the comminution process intensity led to greater cell disintegration, resulting in a peak extraction yield of phenolic compounds (17.61 ± 1.24 mgGAE/100 g FW) achieved with the smallest sample size. Moreover, the application of PEF treatment further increased the Zp value of the bract tissues in a size-dependent manner. The greater the sample size, the stronger the PEF efficiency. Coherently, under optimized PEF conditions (E = 3 kV/cm, WT = 5 kJ/kg), the extracts exhibited higher TPC (+112–361%) and FRAP values (+83–836 %) as compared to the control samples after 120 min of diffusion. The extraction rate of phenolic compounds increased when the comminution degree was increased for both untreated and PEF-treated samples, and this was successfully predicted using Peleg's model.These findings suggest that PEF can be a viable alternative to energy-intensive comminution pretreatment, thus enhancing the extraction of phenolic compounds without requiring finely ground raw material handling.

On the structural integrity and fatigue performance of additively manufactured Ti-6Al-4V parts processed using mechanically recycled powders

In light of the steadily increasing importance of resource efficiency, powder recycling represents one of the major prospects in additive manufacturing. The present study focuses on Ti6Al4V parts manufactured by electron beam-based powder bed fusion using blends of virgin and recycled powder. The latter powder was gained by mechanical comminution of support structures and, thus, addresses a novel topic beyond the well-known reuse of un-melted powder. Microstructure analysis is conducted by scanning electron microscopy and micro-computed tomography, mechanical properties are analyzed by quasi-static tensile and fatigue tests. Thereby, the applicability of recycled powder is assessed, eventually revealing that mechanically recycled powder can be qualified to partially substitute virgin powder in powder bed additive manufacturing.

Identification of <i>UFGT</i>-gene-associated groups of <i>Vitis vinifera</i> L. by the developed method of PCR-RFLP genotyping of grape

The Vitis vinifera L. UFGT gene is one of the diagnostically significant genes for genetic testing of technical grape varieties as well as wine materials and wines produced from them. The strategy for genetic identification of grape varieties and DNA authentication of wine materials that was previously developed by us and is based on direct sequencing of the specific PCR product with a length of 99 bp gave an impulse to prognostic assessment of feasibility of PCR-RFLP analysis for detection of five diagnostically significant polymorphic positions and the following identification of 13 UFGT gene-associated groups of Vitis vinifera L. The aim of this work consisted in identification of UFGT gene-associated groups of Vitis vinifera L. by detection of diagnostically significant polymorphic positions using the developed PCR-RFLP method for genotyping of grape. Objects of research were 24 samples of technical grape varieties. Their sample preparation was carried out by extracting 50–100 mg of mature grape pulp or stone with its mechanical comminution in a mortar and transfer to an Eppendorf-type tube. Then, nucleic acids were extracted using a commercial innuPREP Plant DNA Kit or DiamondDNA Plant kit. PCR-RFLP with the extracted grape DNA was performed with Phire Plant Direct PCR Master Mix and four selected restrictases (PstI, BsaXI, BtsIMutI and HinfI) according to the protocols presented in the paper. The detection of the PCR-RFLP fragments was performed by visualization of electropherograms in a UV transilluminator after horizontal electrophoresis in 2.5% agarose gel with stained TAE buffer. The method for PCR-RFLP genotyping of grapes developed specially for identification of UFGT gene-associated groups of Vitis vinifera L. by detecting diagnostically significant polymorphic positions demonstrated its feasibility when testing 24 samples of technical grape varieties. With that, the positive result was achieved due to the practical ability of each of four selected restrictases to discriminate the strictly specified polymorphic position generating characteristic PCR-RFLP profiles of 13 UFGT gene-associated groups of Vitis vinifera L., seven of which were revealed during this study. Therefore, as a result of the performed study, the genotypic affiliation of several tested grape varieties was established: six samples were identified as representatives of the UFGT gene-associated group No.1; one sample was assigned to gene-associated group No.2; two samples were characterized by the trait of associated group No.3; four samples belonged to group No. 4; one sample to group No. 5; six samples to group No.13.

Does age matter?-Efficiency of mechanical food break down in Tupaia belangeri at different ages.

The relationship of food comminution and individual age in Tupaia belangeri is investigated. It is hypothesized that with increasing age the performance of the molar dentition decreases due to progressive tooth wear. While this relationship is well-documented for herbivores, age-related test series are largely lacking for insectivorous mammals. 15 individuals of Tupaia belangeri were fed exclusively with mealworms, and their faeces were analyzed for the number and size of chitin particles. The exoskeleton of a mealworm is resistant to digestive fluids in the gastrointestinal tract, and the size of individual chitin particles indicates the effectiveness of mechanical comminution that occurs in the oral cavity during mastication. It is hypothesized that a more precise occlusion of the dentition results in smaller particle size. Although individuals of all ages (juvenile, adult, and senile) were able to effectively process mealworms with their dentition prior to digestion, a larger area of very large chitin particles (98% quantile of all particles in senile animals as compared to in the same quantile in adults) in the feces of senile animals was detected. Even though the particle size of indigestible material is irrelevant for the digestive process, these findings either document somatic senescence in the functionality of the teeth, or alternatively a change in chewing behaviour with age.

Применение ферментов при выработке фруктового сока: обзор

Enzymatic treatment is a common method of fruit juice production that facilitates juice extraction from plant cells. The choice of enzyme depends on the fruit composition. Pectinase and cellulase are the most popular enzymes while amylase remains less wide-spread. For some raw materials, enzymatic procedures are more efficient than mechanical comminution or thermal processing. The fruit juice industry uses enzymes for streamlining. Enzymes maximize juice extraction from raw materials and improve such processes as pressing, solid settling, and solid removal. Juices that underwent enzymatic treatment are clear and, as a result, more aesthetically appealing to consumers.
 The review covered the most recent and influential publications on the enzyme treatment of fruit juices (2000–2021). The list of enzymes included pectinase, cellulase, and amylase. The research included the factors that affect the juice fermentation process, i.e., hydromodule, enzyme concentration, incubation time, temperature, and enzyme combination. The methods included data extraction, data analysis, and data compilation, as well as literature search and screening.
 The review focuses on the effects that individual parameters have on specific responses, e.g., yield, viscosity, total soluble solids, acidity, turbidity, clarity, pigment concentration, phenolic content, color, and solids. A greater enzyme concentration, incubation time, and temperature decrease the viscosity of juice and turbidity but cause color changes. If used in different combinations and at different concentrations, enzymes boost the production of bael pulp, banana, sapodilla, durian, pawpaw, grape, white pitaya, and water melon juices. A longer incubation period improves the production of bael pulp, citron, date, and pawpaw juices. However, higher incubation temperatures seem to have no positive effect on the juice yield. Cellulases, pectinases, amylases, and their combinations are able to produce more fruit juice of higher quality with a more favorable time-temperature combination of incubation.
 The optimal enzyme concentration, incubation time, and temperature can increase the juice yield. Therefore, enzymatic treatment is an effective method that ensures favorable properties of the finished product.

Investigation of the friction weldability of an AlSi10MnMg-alloy reinforced with 30 Vol.-% silicon carbide particles with the adequate monolithic material

Due to their positive properties, AMC materials represent a current trend in industrial applications and thus a major research focus. But currently their difficult machinability limits a full establishment. Therefore, suitable joining processes are needed which allow a targeted and punctual use of the AMC-materials and thus minimize the machining effort.This paper presents a feasibility study of a direct material bond between an AlSi10MnMg-alloy reinforced to 30 Vol.-% with silicon carbide particles and the adequate monolithic material by using friction welding. For this purpose, in addition to the general feasibility, the achievable strengths are evaluated and the underlying material behavior as well as metallurgical processes are analyzed.As a result, the principle friction weldability of the used AMC material is demonstrated. Essentially, the joint results from a material bond between the aluminum alloy and the matrix material. The reinforcing phase contained in the latter remains unaffected by the joining process. The test results show neither transport nor mechanical comminution of the silicon carbide particles. It is proven that the quality of the produced material joint as well as the process stability depend on the setting of the variable process parameters. In particular, the ratio between frictional and forge pressure as well as the burn-off length are shown to have a major influence on the joint quality. The intensity of the individual influences is illustrated by the presentation of the parameter main and interaction effects as well as predominant significances. Because the used AMC material is softened by process- and material-related annealing effects, a large proportion of the weld specimens fail outside the joining zone. On the part of the unreinforced aluminum alloy, the absence of such temperature-induced softening is demonstrated. As a consequence, the investigated friction welding process can unusually not be aligned with the lower-strength material.

Miscanthus bioprocessing using HNO3-pretreatment to improve productivity and quality of bioethanol and downstream ethylene

Miscanthus, which can grow on marginal lands and capture CO2, has great potential as an industrial crop. A complete cycle to convert Miscanthus sacchariflorus, grown in Western Siberia (Russia), into bioethanol has successfully been implemented on a pilot scale and employed in downstream ethylene production for the first time. The Miscanthus bioprocessing technology involved mechanical comminution; HNO3-pretreatment; hydrolysis with commercial enzyme preparations CelloLux-A and BrewZyme BGX with cellulase–glucanase–xylanase action; pre-saccharification with substrate feed; simultaneous saccharification and fermentation with delayed inoculation (dSSF) with non-GMO Saccharomyces cerevisiae Y-1693 supplemented with or without (NH4)2SO4, KH2PO4 and yeast extract; rectification; and alumina-catalyzed dehydration to ethylene. Here we discussed pulp reactivity, yield and composition of Miscanthus products at each step (including ethylene), and compared the quality of the bioethanol obtained in the study with published data. The pulp feeding from 80 to 100 g/L resulted in a bioethanol concentration of ~40 g/L. It is the HNO3 pretreatment that provided pure bioethanol with an impurity content as low as 6.5 g/L. Bioethanol (92%-w) contained ~0.85 g/L impurities, mainly n-propanol and isobutanol; the latter weakly influenced the catalyst activity in ethylene production. The supplement slightly increased the yields of bioethanol and fusel alcohols, thereby reduced the yield of byproducts and improved the ethylene quality. The achieved yields of bioethanol and ethylene were 260 L/ton and 115 kg/ton Miscanthus, respectively. The expected yield of absolute ethylene under pilot-scale conditions can be 122 kg/ton Miscanthus.

Novel separation process for obtaining recycled cement and high-quality recycled sand from waste hardened concrete

Separation is a fundamental step for concrete recycling, enabling not only the achievement of reliable and cleaner recycled aggregates but also the better re-use of the remaining concrete constituents. Recently, a new hydraulic binder produced from the hydrated cement paste contained in waste concrete, which is associated with lower processing temperatures and carbon dioxide emissions, has gained momentum in the history of concrete recycling. However, a decisive turning point for its application lies in the successful individualisation of the cement paste and aggregate initially contained in concrete debris. This paper describes a new patented method involving a mechanical comminution stage and a high-intensity magnetic separation process to obtain the cementitious fraction in concrete and retrieve cleaner fine aggregate. The efficiency of the proposed method was assessed through image analysis, thermogravimetry, X-ray diffraction and acid attack. In addition, cement pastes produced with the obtained recycled cement after thermal activation were characterised in terms of mechanical strength. Findings suggest that the proposed method effectively separated the main concrete constituents, especially when the waste material was reduced to the size range 150–500 μm. It was possible to obtain a recycled binder at the current laboratory scale with up to about 80% cement content by weight (nearly 90% in volume). Furthermore, a cleaner recycled fine aggregate, with minimal cement paste contamination, as low as less than 3 wt%, was also obtained. The mechanical strength of pastes with recycled cement retrieved from waste concrete was about 70% of that of reference pastes of equal water/binder produced with recycled cement from non-contaminated waste cement pastes.

Removal of barite from zircon using an aqueous solution of diethylenetriaminepentaacetic acid and potassium carbonate

Abstract In most geologic applications, if barite is present, it must be separated from zircon to enable analysis of the zircon. Current methods of barite removal include mechanical comminution in a ball mill or conversion to barium carbonate by boiling in an aqueous solution of sodium carbonate. Both procedures have potentially serious drawbacks. We optimized an alternative technique for barite removal to avoid these shortcomings. In repeated experiments, boiling in an aqueous solution of 0.1 M diethylenetriaminepentaacetic acid (DTPA) and 6 wt% potassium carbonate for one hour dissolved about 90% of sand-size barite grains. Examination of barite after boiling in DTPA solution revealed evidence for attacks on crystal surfaces in the form of microscopic scallops and pits. In contrast, zircon crystal surfaces were not detectably altered at the microscopic scale by a boiling solution of DTPA and potassium carbonate. The DTPA and potassium carbonate solution procedure may be superior to the other two barite removal methods in two ways. First, it might not introduce bias into the sample, in contrast to both of the other two methods. Second, it requires less time than the sodium carbonate solution technique. If future research shows that the DTPA and potassium carbonate solution technique does not affect isotopic systems in zircon, this method appears to be a favorable alternative to both milling and boiling in sodium carbonate solution.

Recycling Potential of Lithium–Sulfur Batteries—A First Concept Using Thermal and Hydrometallurgical Methods

High-energy battery systems are gaining attention in the frame of global demands for electronic devices and vehicle electrification. This context leads to higher demands in terms of battery system properties, such as cycle stability and energy density. Here, Lithium–Sulfur (Li–S) batteries comprise an alternative to conventional Li-Ion battery (LIB) systems and can be asserted to next-generation electric storage systems. They offer a promising solution for contemporary needs, especially for applications requiring a higher energy density. In a global environment with increasing sustainable economics and ambitions towards commodity recirculation, the establishing of new technologies should also be evaluated in terms of their recycling potential. In this sense, innovative recycling considers highly valuable metals but also mobilizes all technologically relevant materials for reaching a high Recycling Efficiency (RE). This study uses an approach in which the recycling of Li–S batteries is addressed. For this purpose, a holistic recycling process using both thermal and hydrometallurgical steps is suggested for a safe treatment in combination with a maximum possible recycling efficiency. According to the batteries’ chemical composition, the containing elements are recovered separately, while a multi-step treatment is chosen. Hence, a thermal treatment in combination with a subsequent mechanical comminution separates a black mass powder containing all recoverable resources from the metal casing. The black mass is then treated further in an aqueous solution using different solid/liquid ratios: 1:20, 1:50, 1:55, and 1:100. Different basic and acidic leaching solutions are compared with one another: sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl), and NaOH. For further precipitation steps, different additives for a pH adjustment are also contrasted: sodium hydroxide (NaOH) and potassium hydroxide (KOH). The results are evaluated by both purity and yield; chemical analysis is performed by ICP-OES (inductively coupled plasma optical emission spectrometry). The aim of this recycling process comprises a maximum yield for the main Li–S battery fractions: Li, S, C, and Al. The focal point for the evaluation comprises lithium yields, and up to 93% of lithium could be transferred to a solid lithium carbonate product.

Vivid techniques of pretreatment showing promising results in biofuel production and food processing

AbstractDifferent pretreatment techniques help to overcome many barriers in achieving desirable bioproducts at low cost as well as at lower energy requirement. This review predominantly aims to summarize all the pretreatment methods for the production of biofuel from biomass. The massive use of fossil fuel led to several huge problems Predominantly, Bioenergy has attained great importance due to rapid depletion in fossil fuel because biofuels are considered to be one of the promising alternatives of nonrenewable sources. The main objective of pretreatment methods is enhancement of sugar production by hydrolyzing the biomass and help in achieving maximum yield. Pretreatment is a significant tool for the conversion of cellulose as well as it is also very important to change the structure of cellulosic biomass. All the major pretreatment techniques are broadly classified into physical, chemical, physicochemical and biological methodologies which includes techniques like Mechanical Comminution, Acid hydrolysis, steam explosion, microwave pretreatment etc. The motive of these pretreatments is to make cellulose more available to the enzymes that assist in the conversion of carbohydrate polymers into fermentable sugars. Biological pretreatments have been analyzed to have immense advantages over physical and chemical pretreatments. Presently, Biomass almost produce about more than 13% of the world's energy. There are many high‐throughput testing ideas and processing technologies which can add up additional values for a better biomass processing in future. Thus, a systemic and computational approach can combine multistage formulation with multistage problem solving so that novel technology can be encouraged for the biorefinery production. This review has done extensive literature study of the various pretreatment technologies which will assist us to produce bioethanols and other biofuels that can be helpful in reducing the adverse effect on the environment.Practical ApplicationsPredominantly, Bioenergy has attained great importance due to rapid depletion in fossil fuel because biofuels are considered to be one of the promising alternatives of nonrenewable sources. Biofuel Production and Food Processing of various pretreatment technologies produce environmentally friendly methods. All methods of pretreatment help to overcome many barriers and achieving desirable products at low cost as well as lower energy requirement with efficient yield. This article assists us to produce bioethanols and other biofuels that can be helpful in reducing the adverse effect on the environment and on the diminishing amount of fossil fuel.

P.577 Elements of desire questionnaire assessment of bremelanotide efficacy for hypoactive sexual desire disorder in the reconnect studies

Sustainable circular economy is introducing new industrial challenges, including recycling, to move from the cradle-to-grave paradigm to the innovative cradle-to-cradle concept. The core of several recycling systems consists of mechanical comminution, which aims at producing homogeneous mixtures of highly liberated particles. However, the complexity of comminution processes requires adequate models to control and optimize their behavior within the entire recycling system. In the literature, the so-called Population Balance Model has been proposed, which is however limited to the mining industry. In this paper, we examine the applicability of the Population Balance Models in the Waste Electrical and Electronic Equipment recycling industry. In particular, we include the homogeneity and multiplication assumptions, and analyze the impact of the comminution chamber saturation. These simplifications reduce the number of model parameters to be estimated, as the set of parameters remains the same over a wide range of working conditions. We tested our assumptions on a real system for recycling Printed Circuit Boards. Results showed the validity of the multiplication assumption and a marginal effect of saturation (p values for rotor velocity and saturation were always above 25% in an ANOVA with the Bonferroni correction). The homogeneity assumption is also tenable, with the exception of the initial transient, as the null hypothesis of constant output mass distribution under equivalent shredding times was never rejected at the 5% significance level. Outcomes of an out-of-sample validation confirmed the effectiveness of our simplified Population Balance Model (values of the Kolmogorov-Smirnov metric lower than 0.1).

To Study the Effect of Pretreatment on Dry Sugarcane Leaves

It is anticipated that oil and natural gas will deplete within next 40-50 years. Moreover, the expected environmental damages such as the global warming, acid rain and urban smog due to the production of emissions from these sources have forced the world to try to reduce carbon emissions by 80% and shift towards utilizing a variety of renewable energy resources which are less environmentally harmful such as solar, wind, biomass etc. in a sustainable way. Biomass is one of the earliest sources of energy with very specific properties and abundantly available. The sources of biomass are forestry, agricultural and municipal waste and residues. The agriculture waste as biomass is either destroyed or burnt inefficiently causing air pollution. The use of agriculture waste for making briquettes to generate power can be an alternative solution to the problems related to their disposal & pollution. Various pretreatment techniques change the physical and chemical structure of the lignocellulosic biomass and improve hydrolysis rates. The present work high light on pretreating dry sugarcane leaves (biomass) with physical treatment (Mechanical Comminution) by using aggregate impact test apparatus. It was found that effects of number of drops had upgraded the lignin percentage and and reduces the moisture content and ash content.

A Preparation System for Grinding Brittle Materials to Submicron and Nano Particles via Mechanical Comminution

Among industrial and laboratory-scale mills currently employed for producing submicron and nano particles, the high energy media mills occupy an important place. The strength characteristic of ultra-fine particles of brittle materials is analyzed, and the size effect of ultra-fine particle is considered. A kind of high energy media mills i.e. a stirred media mill designed and manufactured. Based the stirred media mill, the corresponding process route by wet grinding and the preparation system via mechanical comminution for grinding submicron and nano particles of brittle materials are proposed and built. Experiments were made through the stirred media mill with different size of the grinding media and at different levels of rotational speed of the mill and the grinding time, and at a fixed filling ratio with unitary size of the grinding media. From the experiment results, it is expected that the preparation system and the corresponding process route based on the stirred media mill is suitable to grind particles to submicron and nano size range for brittle materials.

A review of the benefits for comminution circuits offered by rock blasting

Abstract Rock blasting is the first phase of comminution, completed by mechanical means downstream in the crushing and milling phases. Nevertheless, mineral processers and blasters seldom work together. The total energy of mechanical comminution depends on feeding grain size and on the internal resistance of the material to grinding. Blasting heavily influences both of these aspects: i) it induces visible fracturing: this is the particle size distribution visible to the naked eye, that is measurable by means of image analysis or sieving; ii) it induces invisible fracturing: this is the system of micro-fractures, invisible to the naked eye, that are detectable only by microscopic analysis but show their direct effect by reducing the grinding energy (softens the material). A proper management of blasting can greatly benefit the comminution circuit. In this article, the author analyzes data from literature and from field experiments and discusses the benefits that rock blasting can produce for the comminution process.

A comminution model with homogeneity and multiplication assumptions for the Waste Electrical and Electronic Equipment recycling industry

Sustainable circular economy is introducing new industrial challenges, including recycling, to move from the cradle-to-grave paradigm to the innovative cradle-to-cradle concept. The core of several recycling systems consists of mechanical comminution, which aims at producing homogeneous mixtures of highly liberated particles. However, the complexity of comminution processes requires adequate models to control and optimize their behavior within the entire recycling system. In the literature, the so-called Population Balance Model has been proposed, which is however limited to the mining industry. In this paper, we examine the applicability of the Population Balance Models in the Waste Electrical and Electronic Equipment recycling industry. In particular, we include the homogeneity and multiplication assumptions, and analyze the impact of the comminution chamber saturation. These simplifications reduce the number of model parameters to be estimated, as the set of parameters remains the same over a wide range of working conditions. We tested our assumptions on a real system for recycling Printed Circuit Boards. Results showed the validity of the multiplication assumption and a marginal effect of saturation (p values for rotor velocity and saturation were always above 25% in an ANOVA with the Bonferroni correction). The homogeneity assumption is also tenable, with the exception of the initial transient, as the null hypothesis of constant output mass distribution under equivalent shredding times was never rejected at the 5% significance level. Outcomes of an out-of-sample validation confirmed the effectiveness of our simplified Population Balance Model (values of the Kolmogorov-Smirnov metric lower than 0.1).

The stripping effect of using high voltage electrical pulses breakage for waste printed circuit boards

In this study, high voltage electrical pulses were utilized to process waste printed circuit boards to cost effectively liberate metal and nonmetal materials. Relative mass ωiand particles content ηiindexes were defined to assess the stripping effect produced by high voltage electrical pulses breakage. For relative mass level in the 0–10% range, in the −6+3 mm fraction, particles content accounted for 84.84% of the total particles, while the mechanical crushing only occupied 8.84%. Voltage and pulse experiments were carried out to investigate the crushing effect of high voltage electrical pulse breakage for printed circuit boards. It was found that when the voltage and pulse number was at 160 kV and 300, the stripping rate of copper was 98.56% and 92.58% in the −25+13 mm fraction respectively. The measured bending strength of the material revealed the selective crushing effect of high voltage electrical pulses in the different material interfaces. A liberation mechanism was elaborated by using the energy band theory, and a process model was utilized to reveal the mode of crushing. Furthermore, the microscopic appearance of the resulting product confirmed that copper underwent high-temperature melting, while the resin was decomposed during the crushing process. Compared to conventional mechanical crushing process, high voltage electrical pulses can better liberate metal-bearing than mechanical comminution technology.

High voltage fragmentation of composites from secondary raw materials – Potential and limitations

The comminution of composites for liberation of valuable components is a costly and energy-intensive process within the recycling of spent products. It therefore is continuously studied and optimized. In addition to conventional mechanical comminution innovative new principles for size reduction have been developed. One is the use of high voltage (HV) pulses, which is known to be a technology selectively liberating along phase boundaries. This technology offers the advantage of targeted liberation, preventing overgrinding of the material and thus improving the overall processing as well as product quality.In this study, the high voltage fragmentation of three different non-brittle composites (galvanized plastics, carbon fibre composites, electrode foils from Li-ion batteries) was investigated. The influence of pulse rate, number of pulses and filling level on the liberation and efficiency of comminution is discussed. Using the guideline VDI 2225 HV, fragmentation is compared to conventional mechanical comminution with respect to numerous criteria such as cost, throughput, energy consumption, availability and scalability. It was found that at current state of development, HV fragmentation cannot compete with mechanical comminution beyond laboratory scale.