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15 pages, 7414 KiB

Open AccessArticle

Porous Structure and Fractal Dimensions of Activated Carbon Prepared from Waste Coffee Grounds

by Sofiia Victoriia Sklepova, Nataliia Ivanichok, Pavlo Kolkovskyi, Volodymyr Kotsyubynsky, Volodymyra Boychuk, Bogdan Rachiy, Andrzej Uhryński, Michał Bembenek and Liubomyr Ropyak

Materials 2023, 16(18), 6127; https://doi.org/10.3390/ma16186127 - 8 Sep 2023

Cited by 2 | Viewed by 969

Abstract

The present work reports the results of a systematic study on the evolution of the morphological properties of porous carbons derived from coffee waste using a one-pot potassium-hydroxide-assisted process at temperatures in the range of 400–900 °C. Raw materials and obtained carbons were [...] Read more.

The present work reports the results of a systematic study on the evolution of the morphological properties of porous carbons derived from coffee waste using a one-pot potassium-hydroxide-assisted process at temperatures in the range of 400–900 °C. Raw materials and obtained carbons were studied by TG, DTG, SEM and nitrogen adsorption porosimetry. The decomposition temperature ranges for hemicellulose, cellulose and lignin as the main component of the feedstock have been established. It is shown that the proposed method for the thermochemical treatment of coffee waste makes it possible to obtain activated carbon with a controllable pore size distribution and a high specific surface area (up to 1050 m²/g). A comparative study of the evolution of the distribution of pore size, pore area and pore volume has been carried out based on the BJH and NL-DFT (slit-like pores approximation) methods. The fractal dimension of the obtained carbons has been calculated by Frenkel–Halsey–Hill method for single-layer and multilayer adsorptions. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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30 pages, 20369 KiB

Open AccessArticle

Diagnostics of Bolted Joints in Vibrating Screens Based on a Multi-Body Dynamical Model

by Pavlo Krot, Hamid Shiri, Przemysław Dąbek and Radosław Zimroz

Materials 2023, 16(17), 5794; https://doi.org/10.3390/ma16175794 - 24 Aug 2023

Cited by 2 | Viewed by 1339

Abstract

The condition-based maintenance of vibrating screens requires new methods of their elements’ diagnostics due to severe disturbances in measured signals from vibrators and falling pieces of material. The bolted joints of the sieving deck, when failed, require a lot of time and workforce [...] Read more.

The condition-based maintenance of vibrating screens requires new methods of their elements’ diagnostics due to severe disturbances in measured signals from vibrators and falling pieces of material. The bolted joints of the sieving deck, when failed, require a lot of time and workforce for repair. In this research, the authors proposed the model-based diagnostic method based on modal analysis of the 2-DOF system, which accounts for the interaction of the screen body and the upper deck under conditions of bolted joint degradation. It is shown that the second natural mode with an out-of-phase motion of the upper deck against the main screen housing may coincide with the excitation frequency or its higher harmonics, which appear when vibrators’ bearings are in bad condition. This interaction speeds up bolt loosening and joint opening by the dynamical loading of higher amplitude. The proposed approach can be used to detune the system from resonance and anti-resonance to reduce maintenance costs and energy consumption. To prevent abrupt failures, such parameters as second natural mode frequency, damping factor, and phase space plot (PSP) distortion measures are proposed as bolt health indicators, and these are verified on the laboratory vibrating screen. Also, the robustness is tested by the impulsive non-Gaussian noise addition to the measurement data. A special diagram was proposed for the bolted joints’ strength capacity assessment and maintenance actions planning (tightening, replacement), depending on clearance in the joints. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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20 pages, 4654 KiB

Open AccessArticle

Experimental Study on the Cutting Process of Single Triticale Straws

by Dominik Wilczyński, Krzysztof Talaśka, Krzysztof Wałęsa, Dominik Wojtkowiak and Michał Bembenek

Materials 2023, 16(11), 3943; https://doi.org/10.3390/ma16113943 - 24 May 2023

Cited by 3 | Viewed by 1003

Abstract

This paper presents experimental research on cutting a single stalk of triticale straw for the production of biofuel in the process of its compaction using the piston technique. In the first stage of the experimental study of cutting single triticale straws, the variable [...] Read more.

This paper presents experimental research on cutting a single stalk of triticale straw for the production of biofuel in the process of its compaction using the piston technique. In the first stage of the experimental study of cutting single triticale straws, the variable parameters were the moisture contents of the stem equal to 10% and 40%, the offset between the blade and the counter-blade g, and the linear velocity of the knife blade V. The blade angle and rake angle were equal to α = 0° and β = 0°. In the second stage, the variables, including the blade angle values α = 0°, 15°, 30°, and 45° and the rake angle values β = 5°, 15°, and 30°, were introduced. Taking into account the analysis of the distribution of forces on the knife edge leading to the determination of the force quotients F_c″/F_c and F_w/F_c, and on the basis of the optimization performed and the adopted optimization criteria, the optimal knife edge angle α can be determined (at values g = 0.1 mm and V = 8 mm/s) at α ≅ 0° and the angle of attack β within the range of 5–26°. What the value will be in this range depends on the value of the weight adopted in the optimization. The choice of their values may be decided by the constructor of the cutting device. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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10 pages, 1413 KiB

Open AccessArticle

Effect of the Consolidation Level on Organic Volatile Compound Emissions from Maize during Storage

by Aleksandra Żytek, Robert Rusinek, Anna Oniszczuk and Marek Gancarz

Materials 2023, 16(8), 3066; https://doi.org/10.3390/ma16083066 - 13 Apr 2023

Cited by 4 | Viewed by 1244

Abstract

The aim of this study was to determine the emission of organic volatile compounds from maize grain as a function of granularity and packing density of bulk material in conditions imitating processes occurring in silos. The study was carried out with the use [...] Read more.

The aim of this study was to determine the emission of organic volatile compounds from maize grain as a function of granularity and packing density of bulk material in conditions imitating processes occurring in silos. The study was carried out with the use of a gas chromatograph and an electronic nose, which was designed and constructed at the Institute of Agrophysics of PAS and has a matrix of eight MOS (metal oxide semiconductor) sensors. A 20-L volume of maize grain was consolidated in the INSTRON testing machine with pressures of 40 and 80 kPa. The control samples were not compacted, and the maize bed had bulk density. The analyses were carried out at a moisture content of 14% and 17% (w.b.—wet basis). The measurement system facilitated quantitative and qualitative analyses of volatile organic compounds and the intensity of their emission during 30-day storage. The study determined the profile of volatile compounds as a function of storage time and the grain bed consolidation level. The research results indicated the degree of grain degradation induced by the storage time. The highest emission of volatile compounds was recorded on the first four days, which indicated a dynamic nature of maize quality degradation. This was confirmed by the measurements performed with electrochemical sensors. In turn, the intensity of the volatile compound emission decreased in the next stage of the experiments, which showed a decline in the quality degradation dynamics. The sensor responses to the emission intensity decreased significantly at this stage. The electronic nose data on the emission of VOCs (volatile organic compounds) as well as grain moisture and bulk volume can be helpful for the determination of the quality of stored material and its suitability for consumption. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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21 pages, 12468 KiB

Open AccessArticle

Condition Monitoring of Horizontal Sieving Screens—A Case Study of Inertial Vibrator Bearing Failure in Calcium Carbonate Production Plant

by Jacek Wodecki, Pavlo Krot, Adam Wróblewski, Krzysztof Chudy and Radosław Zimroz

Materials 2023, 16(4), 1533; https://doi.org/10.3390/ma16041533 - 12 Feb 2023

Cited by 2 | Viewed by 1559

Abstract

Predictive maintenance is increasingly popular in many branches, as well as in the mining industry; however, there is a lack of spectacular examples of its practice efficiency. Close collaboration between Omya Group and Wroclaw University of Science and Technology allowed investigation of the [...] Read more.

Predictive maintenance is increasingly popular in many branches, as well as in the mining industry; however, there is a lack of spectacular examples of its practice efficiency. Close collaboration between Omya Group and Wroclaw University of Science and Technology allowed investigation of the failure of the inertial vibrator’s bearing. The signals of vibration are captured from the sieving screen just before bearing failure and right after repair, when it was visually inspected after replacement. The additional complication was introduced by the loss of stable attachment of the vibrator’s shield, which produced great periodical excitation in each place of measurement on the machine. Such anomalies in the signals, in addition to falling pieces of material, made impossible the diagnostics by standard methods. However, the implementation of advanced signal processing techniques such as time–frequency diagrams, envelope spectrum, cyclic spectral coherence, orbits analysis, and phase space plots allowed to undermine defects (pitting on the inner ring). After repair, the amplitudes of vibration from the damaged bearing side were reduced by five times, while sound pressure was only two times lower. The quantitative parameters of vibrations showed significant changes: time series RMS (−68%) median energy of spectrograms (89%), frequencies ratio of cyclic spectral coherence (−85%), and average amplitude of harmonics in envelope spectrum (−80%). The orbits demonstrated changes in inclination angle (16%) and sizes (−48, … −96%), as well as phase space plots sizes (−28, … −67%). Directions of further research are considered. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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20 pages, 6699 KiB

Open AccessArticle

Moisture-Dependent Physical-Mechanical Properties of Maize, Rice, and Soybeans as Related to Handling and Processing

by Weronika Kruszelnicka, Zhengpu Chen and Kingsly Ambrose

Materials 2022, 15(24), 8729; https://doi.org/10.3390/ma15248729 - 7 Dec 2022

Cited by 8 | Viewed by 1812

Abstract

Knowledge of physical and mechanical properties of cereal grains is important for designing handling and processing equipment. However, there is still a lack of knowledge on the influence of moisture content on the physical-mechanical properties as related to machine design. The aim of [...] Read more.

Knowledge of physical and mechanical properties of cereal grains is important for designing handling and processing equipment. However, there is still a lack of knowledge on the influence of moisture content on the physical-mechanical properties as related to machine design. The aim of this study was to investigate and describe the changes in select physical-mechanical properties of maize, rice, and soybeans at various moisture content (10%, 14%, 18%, 22%, 26%; wet basis) and their compression behavior at two loading rates of 1.25 mm/min and 125 mm/min. The measured physical and mechanical properties include size, shape, and breakage force of single kernels. It was found that an increase in moisture content increased the kernel size, altered the kernel shape, and decreased the bulk density. The effects of moisture content and loading rate on breakage force, stress, and energy varied depending on the grain type. Our results indicated that an increase in moisture content changed the mechanical behavior of grain kernels from brittle to viscoelastic. To prevent kernel damage during processing and handling, the measured force and stress during compression can be used as the limit value for designing equipment. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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Graphical abstract

21 pages, 6103 KiB

Open AccessArticle

Modelling of the Process of Extrusion of Dry Ice through a Single-Hole Die Using the Smoothed Particle Hydrodynamics (SPH) Method

by Krzysztof Wałęsa, Jan Górecki, Maciej Berdychowski, Aleksandra Biszczanik and Dominik Wojtkowiak

Materials 2022, 15(22), 8242; https://doi.org/10.3390/ma15228242 - 20 Nov 2022

Cited by 7 | Viewed by 1319

Abstract

This article presents the outcome of research on modelling the process of the extrusion of crystalline dry ice. The purpose of this process is to densify the material and obtain pellets of several millimeters in diameter. This reduces the sublimation rate in ambient [...] Read more.

This article presents the outcome of research on modelling the process of the extrusion of crystalline dry ice. The purpose of this process is to densify the material and obtain pellets of several millimeters in diameter. This reduces the sublimation rate in ambient conditions of the material whose temperature in a solid state is 195 K. A lower sublimation rate means a reduction of the loss of product in its final applications, which include refrigeration and reduction of atmospheric emissions of gaseous CO₂. A ram-type extruder was considered in this analysis, in which dry ice was extruded through a single-hole die of varying geometry. The article presents the results of numerical analyses of the extrusion process, using a simulation method based on the Smoothed Particle Hydrodynamics (SPH) approach. The results from simulations were verified by the experimental data in terms of the maximum force required to complete the process, in order to assess the applicability of the proposed method in further research on dry ice compression. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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11 pages, 2628 KiB

Open AccessArticle

Numerical Simulation of Dry Ice Compaction Process: Comparison of the Mohr–Coulomb Model with the Experimental Results

by Maciej Berdychowski, Jan Górecki and Krzysztof Wałęsa

Materials 2022, 15(22), 7932; https://doi.org/10.3390/ma15227932 - 10 Nov 2022

Cited by 6 | Viewed by 1095

Abstract

How to reduce consumption of energy in manufacturing has become a topical issue nowadays. Certain manufacturing processes are known for being highly energy-intensive and compression of materials belongs to this group. This article presents the simulation of the process of compression of dry [...] Read more.

How to reduce consumption of energy in manufacturing has become a topical issue nowadays. Certain manufacturing processes are known for being highly energy-intensive and compression of materials belongs to this group. This article presents the simulation of the process of compression of dry ice snow with the use of the Mohr–Coulomb model. Two simulation variants were considered in this research. In the first one, constant input parameters were used and in the second one, the input parameters were variable, depending on the changing density of the compressed material. The experimental data were compared with the predicted values to find that the model using constant input parameters was inferior as regards to the goodness of fit. On the other hand, the model with variable input parameters was less accurate in predicting the maximum compression force acting in the process. The last section of this article deals with simulations performed with the Drucker–Prager Cap and modified Cam-Clay models. Finally, it was concluded that the Mohr–Coulomb model yields a more accurate representation of the compression process while requiring less information on the variation of the material parameters. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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Review

Jump to: Research

13 pages, 1461 KiB

Open AccessReview

Pellet Production from Pruning and Alternative Forest Biomass: A Review of the Most Recent Research Findings

by Rodolfo Picchio, Nicolò Di Marzio, Luca Cozzolino, Rachele Venanzi, Walter Stefanoni, Leonardo Bianchini, Luigi Pari and Francesco Latterini

Materials 2023, 16(13), 4689; https://doi.org/10.3390/ma16134689 - 29 Jun 2023

Cited by 4 | Viewed by 1284

Abstract

Typically, coniferous sawdust from debarked stems is used to make pellets. Given the high lignin content, which ensures strong binding and high calorific values, this feedstock provides the best quality available. However, finding alternative feedstocks for pellet production is crucial if small-scale pellet [...] Read more.

Typically, coniferous sawdust from debarked stems is used to make pellets. Given the high lignin content, which ensures strong binding and high calorific values, this feedstock provides the best quality available. However, finding alternative feedstocks for pellet production is crucial if small-scale pellet production is to be developed and used to support the economy and energy independence of rural communities. These communities have to be able to create pellets devoid of additives and without biomass pre-processing so that the feedstock price remains low. The features of pellets made from other sources of forest biomass, such as different types of waste, broadleaf species, and pruning biomass, have attracted some attention in this context. This review sought to provide an overview of the most recent (2019–2023) knowledge on the subject and to bring into consideration potential feedstocks for the growth of small-scale pellet production. Findings from the literature show that poor bulk density and mechanical durability are the most frequent issues when making pellets from different feedstocks. All of the tested alternative biomass typologies have these shortcomings, which are also a result of the use of low-performance pelletizers in small-scale production, preventing the achievement of adequate mechanical qualities. Pellets made from pruning biomass, coniferous residues, and wood from short-rotation coppice plants all have significant flaws in terms of ash content and, in some cases, nitrogen, sulfur, and chlorine content as well. All things considered, research suggests that broadleaf wood from beech and oak trees, collected through routine forest management activities, makes the best feasible feedstock for small-scale pellet production. Despite having poor mechanical qualities, these feedstocks can provide pellets with a low ash level. High ash content is a significant disadvantage when considering pellet manufacture and use on a small scale since it can significantly raise maintenance costs, compromising the supply chain’s ability to operate cost-effectively. Pellets with low bulk density and low mechanical durability can be successfully used in a small-scale supply chain with the advantages of reducing travel distance from the production site and storage time. Full article

(This article belongs to the Special Issue Mechanical Processing of Granular and Fibrous Materials)

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