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1

Handling and transportation properties of rapeseed biomass as affected by particle size

Bojanowska Milena

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2023

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nr 74 (146)

5--15

EN

Rapeseed by-products of seeds de-oiling, particularly expellers and post-extracted meal, are currently considered an important biomass that can be used as an alternative energy source, either in raw form or after conversion to biochar. Rapeseed biomass represents a difficult-to-handle cargo, mainly due to its sensitivity to mechanical, climatic, and biological impacts, as well as its dusty nature. This study aims to determine the physical properties of rapeseed meals and their fractions. Morphological and chemical features of six particle sets are investigated in order to explain the variation in their physical properties having importance in handling and transportation processes. The true density of fractions increases when the particle size decreases due to the diminishing quantitative share of seed coats. No correlation is observed between true and bulk densities, as the particle shape, surface sculpture, and adhesion affect the mutual particle arrangements. Along with a decrease in the particle size from 0.4 mm, a rapid decrease in the flowability is observed. The tendency of the finest dust (d < 0.075 mm) to form agglomerated complexes causes its lower bulk density, higher porosity, and higher angles of repose in comparison to coarse dust (0.075–0.4 mm). It is concluded that a relatively low tendency to free flowing of natural RSM is mainly caused by its wide-ranging particle size distribution and their geometry differentiation, which facilitate mutual particle interlockings. The known cases of blockages of silos, bins, hoppers, and transfer chutes may be mainly caused by the powder fractions (< 0.2 mm), with a much lower flowability than other particles.

2

Optimization of flotation conditions in the beneficiation of PGMs tailings

Hlotse Daphney, Mbaya Richard K.K., Shongwe Mxolisi B.

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 6

art. no. 176859

EN

For several years, mining waste has shown a negative impact on both the environment and human health. The mining industry remains the backbone of the economic growth. Different technologies have been implemented to beneficiate and recover platinum group metals from tailings. The recycling of tailings has been a point of research interest due to their extensive applications. Flotation has been the primary process of upgrading and recovering PGMs. The focus of this study was to optimize flotation conditions in the beneficiation of PGMs for particular small-scale mine tailings. This was done to obtain the most favourable conditions for the small-scale mine tailings to improve operating conditions of specific particle sizes. PGMs tailings obtained from a small-scale mine were characterized using XRD, XRF, SEM/EDS, and ICP - OES to understand the properties of the tailings prior to mineral processing. Flotation batch tests were conducted. The results showed that the chosen particle size was 75 µm, and the favorable reagent dosages were 150 g/Mg and 100 g/Mg for SIBX (collector) and Starch(depressant), respectively. At favourable conditions, the recovery was 65.75% (Pt = 70.38%, Pd = 59.33%, Ru = 34.56%), and the grade was 31.46 g/Mg (Pt = 21.43 g/Mg, Pd = 9.62 g/Mg, Ru = 0.41 g/Mg). It can be concluded that all the flotation parameters are related; lower particle sizes yield high recoveries and better grades due to the exposure of the particle surface to the reagents responsible for the flotation of the PGMs. It was observed that the high collector dosages produce high recoveries with low grades of PGMs. High depressant dosages produce low recoveries with high grades of PGMs. The relationship between the collector and the depressant is of essential importance in the flotation process.

3

Optimization of Particle Size and Ramie Fiber Ratio on Hybrid Bio Panel Production from Oil Palm Trunk as Thermal Insulation Materials

Mawardi Indra, Nurdin, Fakhriza, Rizal Samsul, Aprilia Sri, Faisal Muhammad, Jaya Ramadhansyah Putra

Journal of Ecological Engineering

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2023

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Vol. 24, nr 2

39--49

EN

The abundant availability of waste oil palm trunks is one of the potential fibers for new thermal insulation materials. While focusing on the manufacturing of thermal insulation materials, the main points to be considered are particle size, reinforcement fiber ratio, and press durations, besides binders type and temperature. This study aimed to optimize the manufacturing process of hybrid bio panels based on oil palm trunks as thermal insulation material. The response surface methodology (RSM), with a Box-Behnken Design (BBD), was used to model and optimize the manufacturing process variables. A total of 17 hybrid bio panels were in operation and the independent variables used were particle size, ramie ratio, and press duration. The dependent variables were water absorption, thickness swelling, MOR, and thermal conductivity. The hybrid bio panel obtained under the optimum conditions was characterized by thermogravimetric analysis to observe thermal stability. On the basis of analysis of variance and the contour plot, it was discovered that the interaction between particle size and ramie fiber ratio was a significant variable to optimize hybrid bio panel manufacture. The thermal resistance and modulus of rupture of hybrid bio panels also improved with higher particle size and ramie fiber ratio. The optimum manufacturing process was obtained at OPT particle size of 0.248 mm, ramie fiber ratio of 19.775, and press duration of 25 min. This condition produces a thermal conductivity of 0.079 W/mK, modulus of rupture of 17.702 MPa, water absorption of 54.428%, and thickness swelling of 21.974%. In addition, the hybrid bio panel resulted in thermal stability of 341 °C.

4

Mineralogical and Chemical Characteristics of Phosphates from the Djebel Onk Deposits (Tebessa, Algeria)

Tahri Tourkia, Narsis Souad, Bezzi Nacer, Bouzenzana Abdellali, Sekiou Omar, Trirat Tabet, Amrane Theziri, Benselhoub Aissa

Inżynieria Mineralna

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2023

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no. 2, vol. 1

351--359

PL

Algeria has important phosphate reserves (2 billion tons) located in the east of the country at Djebel Onk. This mining district is located in the northwestern part of the Algerian Sahara near the Algerian-Tunisian border. The granulo-chemical and XRD analytical results confirm the phosphate depletion of Bled El Hadba layer and their enrichment in carbonate and dolomite, in comparison with the layer of Kef Essennoun. Phosphorite particles are heterogeneously grained. Although the two deposits are relatively close to each other, they show different mineralogical and chemical characteristics, which may cause the use of different mining exploitation methods.

XX

Algieria posiada ważne rezerwy fosforanów (2 miliardy ton) zlokalizowane na wschodzie kraju w Djebel Onk. Ten obszar górniczy znajduje się w północno-zachodniej części algierskiej Sahary, w pobliżu granicy algiersko-tunezyjskiej. Wyniki analiz granulochemicznych i XRD potwierdzają zubożenie fosforanów w warstwie Bled El Hadba i ich wzbogacenie w węglan i dolomit, w porównaniu z warstwą Kef Essennoun. Cząstki fosforytu są niejednorodnie ziarniste. Chociaż oba złoża znajdują się stosunkowo blisko siebie, wykazują różne właściwości mineralogiczne i chemiczne, co może powodować stosowanie różnych metod eksploatacji górniczej.

5

Influence of surface-modified nanoclay on the flexural strength of unsaturated polyester resin

Stępka Dominik

Inżynieria Materiałowa

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2023

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Vol. 44, nr 5

5--10

EN

This study delves into the influence of surface-modified nanoclay on the flexural strength of Unsaturated Polyester Resins (UPRs). UPRs, known for their robust mechanical properties, find extensive applications across various industries. With the aim of further enhancing these properties, nanofillers, specifically surface-modified nanoclay, were incorporated into the resin matrix. Our research revealed a significant improvement in flexural strength with an optimal nanoclay addition of 0.1% by weight. However, the morphological analysis identified the presence of nanoclay agglomerates, indicating potential areas for optimization in the dispersion process. The findings present a promising direction for developing advanced UPR-based materials, emphasizing the pivotal role of nanofillers in achieving superior mechanical performance.

PL

Analizowano wpływ nanoglinki o modyfikowanej powierzchni na wytrzymałość na zginanie nienasyconych żywic poliestrowych (UPR). UPR, znane ze swoich solidnych właściwości mechanicznych, znajdują szerokie zastosowanie w różnych gałęziach przemysłu. W celu dalszej poprawy tych właściwości do matrycy żywicznej wprowadzono nanonapełniacz, a dokładnie nanoglinkę z modyfikowaną powierzchnią. Badania wykazały znaczną poprawę wytrzymałości na zginanie przy optymalnym dodatku nanoglinki w ilości 0,1% mas. Analiza morfologiczna wykazała obecność aglomeratów nanoglinki, wskazując potencjalne obszary optymalizacji w procesie dyspersji. Odkrycia wyznaczają obiecujący kierunek rozwoju zaawansowanych materiałów na bazie UPR, podkreślając kluczową rolę nanonapełniaczy w osiąganiu doskonałych parametrów mechanicznych.

6

A study on the influence of particle size on the identification accuracy of coal and gangue

Li Xin, Wang Shuang, He Lei, Luo Qisheng

Gospodarka Surowcami Mineralnymi

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2023

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T. 39, z. 1

109--129

EN

In order to explore the impact of coal and gangue particle size changes on recognition accuracy and to improve the single particle size of coal and gangue identification accuracy of sorting equipment, this study established a database of different particle sizes of coal and gangue through image gray and texture feature extraction, using a relief feature selection algorithm to compare different particle size of coal and gangue optimal features of the combination, and to identify the points and particle size of coal and gangue. The results show that the optimal features and number of coal and gangue are different with different particle sizes. Based on visible-light coal and gangue separation technology, the change of coal and gangue particle size cause fluctuations in the recognition accuracy, and the fluctuation of recognition accuracy will gradually decrease with increases in the number of features. In the process of particle size classification, if the training model has a single particle size range, the recognition accuracy of each particle size range is low, with the highest recognition accuracy being 98% and the average recognition rate being only 97.2%. The method proposed in this paper can effectively improve the recognition accuracy of each particle size range. The maximum recognition accuracy is 100%, the maximum increase is 4%, and the average recognition accuracy is 99.2%. Therefore, this method has a high practical application value for the separation of coal and gangue with single particle size.

PL

W celu zbadania wpływu zmian wielkości cząstek węgla i skały płonnej na dokładność rozpoznawania oraz poprawienia dokładności identyfikacji pojedynczych cząstek węgla i skały płonnej przez urządzenia sortujące, w ramach tej pracy utworzono bazę danych różnych rozmiarów cząstek węgla i skały płonnej za pomocą obrazów szarych i ekstrakcję cech tekstury przy użyciu algorytmu wyboru cech reliefowych w celu porównania różnych rozmiarów cząstek węgla i skały płonnej przy optymalnych cechach kombinacji oraz identyfikacji punktów i wielkości cząstek węgla i skały płonnej. Wyniki pokazują, że optymalne liczby cech węgla i skały płonnej są różne dla różnych rozmiarów cząstek. W oparciu o technologię separacji węgla i skały płonnej w świetle widzialnym, zmiana wielkości cząstek węgla i skały płonnej powoduje fluktuacje dokładności rozpoznawania, a te z kolei będą stopniowo zmniejszać się wraz ze wzrostem liczby cech. W procesie klasyfikacji wielkości cząstek, jeśli model uczący ma jeden zakres wielkości cząstek, dokładność rozpoznawania każdego zakresu wielkości cząstek jest niska, przy czym najwyższa dokładność rozpoznawania wynosi 98%, a średni wskaźnik rozpoznawania wynosi tylko 97,2%. Metoda zaproponowana w tym artykule może skutecznie poprawić dokładność rozpoznawania każdego zakresu wielkości cząstek. Maksymalna dokładność rozpoznawania wynosi 100%, maksymalny wzrost to 4%, a średnia dokładność rozpoznawania to 99,2%. Dlatego ta metoda ma dużą praktyczną wartość użytkową do oddzielania węgla i skały płonnej według rozmiaru pojedynczej cząstki.

7

Application of the Critical Shear Crack Theory for calculation of the punching shear capacity of lightweight aggregate concrete slabs

Gołdyn Michał

Archives of Civil Engineering

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2023

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Vol. 69, nr 1

55--70

EN

The paper discusses the principles of the Critical Shear Crack Theory (CSCT) in terms of the punching shear analysis of flat slabs made from lightweight aggregate concretes. The basic assumptions of the CSCT were discussed, explaining the differences with regard to the calculation of ordinary concrete flat slabs, relating mainly to the adopted failure criterion associated with ultimate slab rotation. Taking into account the observations and conclusions from the previous experimental investigations, it was confirmed, that contribution of lightweight aggregate particles in the aggregate interlock effect should be ignored, due to possibility of aggregate breaking. However, the analysis of the profile of failure surface confirmed, that particles of the natural fine aggregate increase the roughness of the surface and should be included by formulating failure criterion for LWAC slabs. The theoretical load-rotation relationships were compared with the results of measurements, confirming good agreement in most cases. The theoretical ultimate rotations were lower on average by about 11% than the experimental ones. The analysis of 57 results of the experimental investigations on punching shear of LWAC slabs made from various types of artificial aggregates showed a very good agreement with predictions of the CSCT. The obtained ratio of the experimental to theoretical load was 1.06 with a coefficient of variation of 9.1%. The performed parametric study demonstrated a low sensitivity of the correctness of the CSCT predictions to a change in a fairly wide range of parameters such as: the longitudinal reinforcement ratio, concrete compressive strength and concrete density.

PL

Jednym z podstawowym problemów przy projektowaniu stropów płaskich z lekkich betonów kruszywowych jest zapewnienie odpowiedniej nośności na przebicie stref podporowych. Mimo niewątpliwych zalet, do których można zaliczyć mniejszy ciężar objętościowy czy też lepsze właściwości izolacyjne, lekkie betony kruszywowe charakteryzują się mniejszą o 10 do nawet ponad 30% wytrzymałością na rozciąganie w porównaniu z betonami zwykłymi o zbliżonej wytrzymałości na ściskanie. W odróżnieniu od obowiązującej obecnie normy EN 1992-1-1, bazującej na formułach pół-empirycznych, za podstawę określania nośności płyt na przebicie w procedurach fib Model Code 2010 i prEN 1992-1-1 przyjęto podejście mechaniczne, nawiązujące do Teorii Krytycznej Rysy Ukośnej (Critical Shear Crack Theory - CSCT). Teoria ta zakłada, że wskutek powstania rys ukośnych, mechanizm przenoszenia sił poprzecznych staje się zależny głównie od efektu zazębiania kruszywa, resztkowej wytrzymałości betonu na rozciąganie, oporu ścinania betonu w strefie ściskanej oraz mechanizmu dyblującego zbrojenia głównego. Nośność na przebicie została powiązana ze zdolnością płyty do deformacji, reprezentowanej w przypadku płyt smukłych przez kąt obrotu ψ, który może zostać wyrażony jako całka z krzywizny płyty w rozważanej strefie.

8

Characteristic of particles created by preparatory operations of the particleboard production process

Pędzik Marta, Iswanto Apri Heri, Muhammad Adly Rahandi Lubis, Fatrisari Widya, Tomaczak Karol, Rogoziński Tomasz

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2023

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No. 121

91--100

EN

Characteristic of particles created by preparatory operations of the particleboard production process. The production of wood-based panels, taking into account material innovations, involves the need to adjust the operation of technological devices to the properties of basic and auxiliary materials. In this study, it was decided to check the particle sizes after sorting raw materials representing 3 groups: forest biomass – pine branches, agricultural biomass - oilseed plant straw, and post-production material. Fractions were taken from the 2.00 mm mesh sieve of a sorter for the core layer of the particleboard and the fractional composition was determined by sieve analysis. The average linear particle dimensions and bulk density of each lignocellulosic raw material were also determined. Due to the varying proportions, it is necessary to adapt the parameters of the technological operations to the specifics of the raw material being processed or to introduce guidelines for the selection of particle sizes guided by their actual average size. Studies have shown differences between the individual materials. This is particularly important, as proper preparation of the raw material translates into the quality of the boards produced from them and the efficiency of the entire process.

9

Hyperspectral indices developed from multi-angular bidirectional reflectance can trace the particle size of granite

Wu Mengjuan, Jin Jia, Wang Jinlin, Wang Quan

Acta Geophysica

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2023

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Vol. 71, no. 1

193--208

EN

The particle size of a rock is one of the critical physical properties related to a series of geological processes. While the prevalent photometric studies performed to quantitatively assess the physical properties of minerals and rocks rely much on radiative transfer model inversions from surface reflectance, the complicated procedures required seriously limit their applications. Instead, this study has attempted an empirical-based approach to trace the particle size of granite based on multi-angular bidirectional reflected information, providing a practical method for quickly assessing the physical properties of minerals and rocks from surface reflectance. Five common hyperspectral index types together with different spectral preprocessing treatments, including the original hyperspectral reflectance, derivative analysis, continuum-removed reflectance, and apparent absorption spectra, were screened to explore the best indices for both measured and Hapke model-simulated datasets. The results suggested that the normalized difference index (ND) calculated from the apparent absorption spectra using the wavelengths of 1 325 nm and 1 800 nm is a robust index for tracing the particle size for both measured and simulated datasets.

10

Kinetic modelling of flotation column and Jameson cell in coal

Karaca Sevgi, Ucar Ali, Sahbaz Oktay

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 5

art. no. 152848

EN

Physical enrichment technologies can be used worldwide in various coal washing plants to enrich up to 500 μm particle size. Conversely, coals smaller than this are discarded as waste, causing storage and environmental issues. In this regard, studies on coal below 500 μm in Turkey have recently acquired attraction. The Jameson flotation cell and flotation column, which have many uses worldwide but are not used throughout the plant in Turkey, were used to investigate the separation possibilities of coals below 500 μm. In the study, the flotation column and Jameson cell performances for three different particle sizes (-500+300, -300+212 and -212+106 μm) were compared. For the first time, both machines operated in a negative bias condition. In addition, the flotation kinetics of the machines were modelled with some critical operating parameters. Models illustrating the main and multiple effects of the parameters were developed using the data derived from the experimental results, and the models were statistically significant at the 95% confidence level. In the experiments performed with both flotation machines, the flotation rate increases with the decrease in particle size in general. According to the results, the velocity increase in the Jameson cell was 0.0050-0.0075 min-1 compared to the flotation column in the experiments performed in the size range of -500+300 μm, and the flotation rate constant increased approximately twice. In the size range of -212+106 μm, the difference became larger, and the flotation rate of the Jameson cell increased up to six times with a difference of 0.0450-0.0500 min-1.

11

Effect of particle size on surface roughness and morphology of heat-treated electroless Ni-YSZ coating

Bahiyah Baba N., Ghazali A. S., Azinee S. N., Abdul Rahman A. H., Sharif S.

Journal of Achievements in Materials and Manufacturing Engineering

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2022

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Vol. 114, nr 1

5--14

EN

Purpose: The paper discusses the surface characterisation of electroless nickel-yttria-stabilised zirconia (Ni-YSZ) coating with varying YSZ particle sizes and undergoes heat treatment at a temperature between 300-400°C for 1-2 hours for wear resistance purposes. This finding will be helpful to the application of Ni-YSZ as an alternative coating for cutting tools. Design/methodology/approach: The surface characterisation was analysed using JOEL Scanning Electron Microscope (SEM) coupled with Energy Dispersive X-ray (EDX) JSM 7800F. The crystallographic structure of materials was analysed by X-ray diffraction (XRD) Bruker D8 Advance instrument. The Ni-YSZ coating was deposited using electroless nickel co-deposition of 8YSZ ceramic particles with a nano, mixed and microparticle sizes onto a high-speed steel (HSS) substrate. The coatings were heat treated at temperature 300-400°C and time 1-2 hours. The surface roughness was measured using Mitutoyo surface roughness tester SJ-301. Findings: The electroless Ni-YSZ coating deposited has an average thickness of 30 μm. It is found that the coating morphology electroless coating without YSZ particle incorporation (EN) and Ni-YSZ nano (N) is smoother compared to the Ni-YSZ mixed (NM) and Ni-YSZ micro (M). The EDS composition analysis shows the YSZ content in the electroless Ni-YSZ coating for N samples is the lowest, whereas NM samples are the highest. This resulted in the surface roughness behaviour where the mixed-size YSZ particle gives the highest roughness at all temperatures. The XRD analysis shows that heating temperatures above 300°C caused the precipitation of Ni3P crystalline. Research limitations/implications: Previous studies in the surface characterisation of electroless nickel composite are scarce; thus, the study has limitations in finding supporting data. Originality/value: The surface characterisation especially related to the surface roughness of the electroless nickel, either the Ni-P or composites or alloys are rarely reported. Thus, this study enlightened the effect of particle size on surface roughness and morphology of heat-treated coatings.

12

Evaluating the effect of hydrofluoric acid etching on quartz grains using microscope image analysis, laser diffraction and weight loss particle size estimate

Poręba Grzegorz, Tudyka Konrad, Szymak Agnieszka, Pluta Julia, Rocznik Joanna, Świątkowski Jakub, Osadnik Rafał, Moska Piotr

Geochronometria

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2022

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Vol. 49, no. 1

1--8

EN

In this work we investigate the quartz etching process using hydrofluoric acid for trapped charge dating (TCD) applications. It is done using material collected from an active sand mine in Bełchatów Nowy Świat, central Poland. Approximately 20 kg of material was collected and prepared using routine procedures that are applied in TCD laboratories. The material was sieved using 180–200 μm meshes, and the selected fraction was etched for various time intervals. Sieved samples were etched for durations from 0 min up to 180 min and measured with microscope image analysis (IA), laser diffraction (LD), and mass loss which were used to estimate the depths of etching. Our results show statistical data on how non-uniform the etching process is. We estimate this as a function of etching time from IA, LD and mass loss. In our investigation, mass loss measurements with the assumption of spherical grains correspond to the decrease of radius of ca. 0.151 ± 0.003 μm ˑ min–1. In case of LD, a rough etch depth estimation corresponds to a range 0.06–0.18 μm ˑ min–1 with median at 0.13 μm ˑ min–1. Microscope IA gives a 0.03–0.09 μm ˑ min–1 with a median at 0.05 μm ˑ min–1. Moreover, quartz grains are fractured into smaller pieces while etching. It means that assumptions that are used in etch depth estimation from mass loss are not correct. They incorrect not only because grains are not spheres but also because the number of grains is not constant. Therefore, the etch depth estimated from mass loss might be overestimated. Using microscope IA we report etch depth ranges that might be used to roughly estimate the etch depth uncertainty.

13

The effect of particle size on the mechanical properties of Alkali Activated Steel Slag Mortar

Ing Doh Shu, Ho Chia Min, Xiaofeng Li, Jaya Ramadhansyah Putra, Abdullah Mohd Mustafa Al Bakri, Chin Siew Choo, Rahim Nur Liza, Nabiałek Marcin

Archives of Civil Engineering

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2022

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Vol. 68, nr 2

51--61

EN

With the rapid development of industry, abundant industrial waste has resulted in escalating environmental issue. Steel slag is the by-product of steel-making and can be used as cementitious materials in construction. However, the low activity of steel slag limits its utilization. Much investigation has been conducted on steel slag, while only a fraction of the investigation focuses on the effect of steel slag particle size on the properties of mortar. The aim of this study is to investigate the effect of steel slag particle size as cement replacement on properties of steel slag mortar activated by sodium sulphate (Na2SO4). In this study, two types of steel slag, classified as fine steel slag (FSS) with particle sizes of 0.075 mm and coarse steel slag (CSS) with particle sizes of 0.150 mm, were used for making alkali activated steel slag (AASS) mortar. Flow table test, compressive strength test, flexural strength test and UPV test were carried out by designing and producing AASS mortar cubes of (50x50x50) mm at 0,10%, 20% and 30% replacement ratio and at 0.85% addition of Na2SO4. The results show that the AASS mortar with FSS possess a relatively good strength in AASS mortar. AASS mortar with FSS which is relatively finer shows a higher compressive strength than CSS up to 38.0% with replacement ratio from 10% to 30%. This study provided the further investigation on the combined influence of replacement ratio and particle size of SS in the properties of fresh and hardened AASS.

14

New method for comparing of particle-size distribution curves

Opyrchał Leszek, Chmielewski Ryszard, Bąk Aleksandra

Archives of Civil Engineering

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2022

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Vol. 68, nr 1

63--72

EN

The article discusses a new mathematical method for comparing the consistency of two particle size distribution curves. The proposed method was based on the concept of the distance between two graining curves. In order to investigate whether the distances between the particle size distribution curves are statistically significant, it was proposed to use the statistical test modulus-chi. As an example, the compliance of three sieve curves taken from the earth dam in Pieczyska on the Brda River in Poland was examined. In this way, it was established from which point of the dam the soil was washed away. However, it should be remembered that the size of the soil grains built into the dam does not have to be identical to the grain size of the washed out soil, because the fine fractions will be washed away first, while the larger ones may remain in the body of the earth structure.

PL

Problem porównywania krzywych uziarnienia powstał po wypłukaniu na dolne stanowisko niewielkiej ilości gruntu z korpusu Zapory w Pieczyskach w 2020 r. Ponieważ w 2016 r. również został wypłukany z dolnej cześci zapory grunt, zadano sobie pytanie, czy na podstawie znajomości krzywej uziarnienia można stwierdzić, ze wypłukany materiał pochodzi z tego samego miejsca. W celu zbadania zgodności krzywych uziarnienia zaproponowano metodę statystyczną opartą o koncepcję odległości pomiędzy tymi krzywymi. Za odległość pomiędzy krzywymi uziarnienia rozumiana jest suma wartości bezwzględnych procentowych zawartości masy przechodzącej przez dane sito podzielona przez odchylenie standardowe wyznaczenia zawartości procentowej (wzory (2.1)–(2.4)). Wzór (2.4) upraszcza się gdy procentowa zawartość masy jest obliczana z takim samym odchyleniem standardowym dla każdej krzywej (2.5). Odchylenie standardowe identyfikowane jest z niepewnością standardową wynikającą z pomiaru masy gruntu zebranego na sitach. Kolejne kroki obliczenia tej wartości podane są we wzorach (3.1)-(3.5). Wzór (3.6) to końcowy rezultat obliczenia niepewności standardowej. Zależy ona od pomiarowej niepewności masy oraz od samej masy zebranej na sicie. Tabela 1 oraz tabela 2 prezentują wartość niepewności obliczoną dla typowych mas pobieranych próbek gruntu (100-500 g) i procentowych zawartości gruntu na sicie, dla dokładności pomiarowej wagi 0,1 i 0,5 g. Następnie porównywano krzywe przesiewu próbek pobranych z wypłukanego gruntu w 2016 i 2020 r. oraz krzywej archiwalnej z 1974 r. reprezentującej typowy grunt korpusu zapory (rys. 1).

15

Dynamic impact compressive performance of expanded polystyrene (EPS)-foamed concrete

Yuan Chen, Wenhua Zhang, Lei Zhang, Wanting Zou, Yunsheng Zhang

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e164, 2022

EN

The mechanical property and thermal insulation capacity of EPS concrete will be reduced due to the uneven distribution and float of EPS particles. In this study, an effective strategy for resolving these issues is provided. Physical foaming was mostly employed in this process to prepare foam and inject it into EPS concrete. Different EPS contents and particle sizes were used to make the 11 groups of novel EPS-foamed concrete specimens. The Split Hopkinson Pressure Bar (SHPB) was used to investigate the dynamic impact performance of the new EPS-foamed concrete. The dynamic increasing factor (DIF), peak stress, energy absorption capabilities, and stress–strain curves were all reviewed. The findings revealed that when the amount of EPS in the system increased, the peak stress fell and the energy absorption capacity gradually increased. The energy absorbed was increased by 7–8 times in comparison to specimens lacking EPS. Furthermore, the optimal EPS con-tent ranged between 30 and 40% by volume. The EPS particle size had a significant impact on the specimen strength under dynamic impact load when the density was the same. It was determined that the optimal distribution of EPS particle size was 3–5 mm, based on the test results and the degree of specimen damage. Under the dynamic impact with the best particle size, EPS-foamed concrete demonstrated a relevant excellent energy dissipation capability, with a maximum DIF of 9.16.

16

Analiza jakości filtratu z filtrów pospiesznych pracujących z przerwami

Zielina Michał

Instal

|

2021

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nr 6

34--38

PL

W literaturze można znaleźć doniesienia sugerujące możliwość pogorszenia się jakości filtratu po przerwaniu pracy filtra pospiesznego na kilka godzin i ponownym jego uruchomieniu bez wcześniejszego płukania. W pracy przeanalizowano przyczyny teoretyczne tego zjawiska. Przedstawiono wyniki badań eksperymentalnych w jednej z krakowskich stacji filtrów. Filtry wyłączano z eksploatacji na kilka godzin dwukrotnie. Po raz pierwszy, w krótkim czasie po płukaniu, gdy złoże było jeszcze w niewielkim stopniu zakolmatowane, a drugi raz, po dłuższym czasie, gdy złoże było już w dużym stopniu wypełnione osadem. Badania wykazały całkowity brak pogorszenia jakości filtratu po pierwszym odłączeniu filtra z eksploatacji. Za drugim razem zaobserwowano przez krótki czas niewielkie pogorszenie efektywności usuwania mętności względem efektywności sprzed wyłączenia filtra. Równocześnie zaobserwowano duże i utrzymujące się przez dłuższy czas spadki efektywności usuwania sumarycznej liczby cząstek i stężenia zawiesiny. Zjawisko to spowodowane było mniejszymi spadkami efektywności usuwania cząstek drobniejszych i większymi, utrzymującymi się dłużej spadkami usuwania cząstek grubszych. Obserwacje wykazały możliwość bezpiecznego odłączania filtrów w niewielkim stopniu zakolmatowanych i ryzyko wyłączania filtrów w późniejszym okresie ekploatacji.

EN

There are reports in the literature suggesting the possibility of a deterioration of the filtrate quality after interrupting the operation of a rapid filter for several hours and restarting it without prior backwash. The theoretical reasons for this phenomenon are analysed in this paper. The results of experimental research at one of Krakow’s filter stations are presented. The filters were taken out of operation for a few hours twice. The first time, shortly after backwash, when the bed was still slightly colmated, and the second time, after a longer period of time, when the bed was already largely filled with sludge. The tests showed a complete lack of deterioration of the filtrate quality after the first removal of the filter from service. The second time, a slight deterioration in turbidity removal efficiency was observed for a short period of time compared to the efficiency before the filter was taken out of service. At the same time, large and sustained decreases in the removal efficiency of total particle number and suspended solids concentration were observed. This phenomenon was caused by smaller decreases in the removal efficiency of finer particles and larger, longer lasting decreases in the removal efficiency of coarser particles. The observations showed a possibility of safe disconnection of filters with a small degree of collimation and a risk of disconnection of filters at a later stage of their exploitation.

17

Effect of Particle Sizes of Slag on Reduction Characteristics of Nickel Slag-Coal Composite Briquette

Li Xiaoming, Li Yi, Xing Xiangdong, Wang Yanjun, Wen Zhenyu, Yang Haibo

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 1

127--134

EN

Nickel slag has a high-content iron and is a secondary utilization resource with great development potential. The coal-based direct reduction is an innovative technology that can be used to utilize the iron resources in nickel slag. The effect of the particle size of nickel slag on the strength and the reduction of nickel slag-coal composite briquettes were investigated. Four samples with particle size of 75~106 μm, 106~150 μm, 150~270 μm, and >270 μm were selected. The drop strength increased 9.4 times and the compressive strength reached 281.1 N when the nickel slag particle size decreased from >270 μm to 75~106 μm. The reduction degree determined by the data from the thermogravimetric experiment indicated that its maximum was 79.545%. The reduction experiments performed at 1200°C for 45 minutes indicated that the nickel slag with particle sizes between 75~106 μm were appropriate for the reduction of the nickel slag-coal composite briquettes.

18

Preparation of yttrium citrate by the reaction of yttrium hydroxide with sodium citrate

Janusz Władysław, Skwarek Ewa, Sternik Dariusz

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 6

51--59

EN

A method of obtaining yttrium citrate by transformation of freshly precipitated yttrium hydroxide in the solutions of sodium citrate under hydrothermal conditions has been proposed. To determine the synthesis time, transformation kinetics consisted in by taking the solid samples for the C and H contents analysis after 6, 12, 24, 48 and 72 hours of synthesis. Simultaneously these samples were subjected to the thermogravimetric analysis. As follows from the thermogravimetric analysis adsorption of citrate dihydrate on yttrium hydroxide is observed in the initial period up to 24 hours. Later the yttrium citrate dihydrate is formed. The thermogravimetric analysis of the final product i.e. amorphous yttrium citrate showed that the decomposition/oxidation of the sample occurs in six stages the particle size analysis method of static light scattering showed that 45% of the particles had a diameter of 0.1-0.9 µm and 55% of particles with sizes from 0.9 to 5 µm.

19

Effects of frothers and particle size on the flotation kinetics of the Jameson Cell

Şahbaz Oktay, Demir Muhammet Kubilay

Physicochemical Problems of Mineral Processing

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2020

|

Vol. 56, iss. 5

829--838

EN

Determination of the flotation kinetic is crucial for optimization, simulation, and plant design for flotation processes. Even though there are many studies carried out to clarify the kinetic properties of the conventional flotation cells, there is not enough detailed study about the Jameson cell which is used more than 300 plants but no application in Turkey yet. One of the most important parameters affects the kinetic of flotation is a frother. The effects of common frothers on the kinetic of Jameson cell can be crucial due to the possible further application of the cell in European and Turkish flotation industries. The present study was performed out to reveal the kinetic properties of the Jameson cell by using both pure quartz and coal particles. Besides, the effects of three different types of frothers on the kinetic of the Jameson cell were investigated for various particles sizes. According to the results, aliphatic alcohol type frother (MIBC) provided higher recovery for fine particles, while polypropylene glycol type frother (AF65) gave a better ability to float medium and coarse size particles. Additionally, the results show that the Jameson cell was four times faster than the mechanical cell for medium size while the ratio was three times for coarse particles. Lastly AF65 can be used for flotation of coarse particles in the Jameson cell while MIBC can be preferred for fines.

20

Effect of particle size on reduction kinetics of hematite ore in suspension roaster

Gaob Peng, An Yaxiong, Li Guofeng, Han Yuexin

Physicochemical Problems of Mineral Processing

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2020

|

Vol. 56, iss. 3

449--459

EN

Suspension magnetization roasting followed by magnetic separation is an innovative and effective way to recover iron from refractory iron ores, and the particle size of the ore greatly affects the roasting index. To identify the effect of particle size on the reduction kinetics for the transformation of hematite to magnetite, a high-purity hematite ore with different size fractions were isothermally reduced using a suspension roaster. The pure hematite ore was divided into -1000+500 µm, -500+150 µm, -150+74 µm, -74+37 µm and -37 µm size fractions, while the gas mixture of CO and CO2 with a volume ratio of 1:4 was used as reductant. The results showed that the most suitable mechanism function for the reduction of -37 µm size fraction hematite ore is the Avrami-Erofeev model. In the case of -500+37 µm size fraction, the reduction process can be described by first-order chemical reaction model. For -1000+500 µm size fraction, the reduction of hematite ore is restricted by the second-order chemical reaction. In addition, scanning electron microscopy (SEM) analysis results demonstrated that the transformation of hematite particles to magnetite is in accordance with the characteristics of shrinking core model. The phase transformation primarily occurs at the edge of hematite particles and then develop towards the inner side of particles. The findings of this paper provide a theoretical basis for the development and utilization of refractory hematite ore via suspension magnetization roasting technology.