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    Wyświetlanie 1-8 z 8
    Tytuł:
    Dielectric properties of coal ash
    Autorzy:
    González Valdes, Laura
    Friis Aage, Valentin
    Nowak-Woźny, Dorota
    Powiązania:
    https://bibliotekanauki.pl/articles/1818164.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    coal
    mineral matter transformation
    ash sintering
    dielectrical properties
    Opis:
    Mineral matter of coal causes serious operational problems related to ash de- position in coal fired power plants such slagging and fouling, and so it has become the main subject of study in terms of current utilization. Moreover, the standardized tests currently used as the preferred predictive tools for slagging properties of coal sources have been lately reproved in the literature and un- certainties arrive due to the poor repeatability and reproducibility. That is why, methods for determining the sintering temperatures are being extensively investigated across the industry. This study focuses on the electrical properties of coal ash and its relation to the ash sintering process, where physical and chemical processes take part inside the material. The following methodology is based upon the continuous registration of the changes of resistance measured as an AC and DC property. The proposed laboratory stand allows measuring ‘in situ’ a coal ash sample being heated to analyse its electrical properties. It was found that the values measured are temperature dependent and could reflect the chemico-physical changes in the material, which may directly suggest the transformation of the intrinsic properties, giving insight into the sintering process.
    Źródło:
    Zeszyty Energetyczne; 2018, 5; 51--60
    2658-0799
    Pojawia się w:
    Zeszyty Energetyczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of coal slurry properties deposited in impoundments located in the upper silesian coal basin
    Autorzy:
    Lutynski, A.
    Suponik, T.
    Lutynski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/109929.pdf
    Data publikacji:
    2013
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    coal slurry
    tailings
    chemical composition
    impoundments
    Opis:
    Results of investigation of physical, chemical and energetic properties of steam and coking coal slurries deposited in twenty Polish impoundments are presented in the paper. Coal slurry was sam-pled in accordance with a certain procedure from different locations and depths at each impoundment whereas laboratory investigation was performed on averaged samples. The performed investigation in-clude determination of chemical composition, moisture content, volatile matter, sulfur and calorific value at various states. Additionally, properties of coal slurry of particle size below 0.1 mm are presented. The average content of this fraction is approximately 62% and ranges at individual impoundments from 28 to 79%. An average calorific value in analytical state of coal slurries deposited in impoundments in the fraction below 0.1 mm is rather high (12.01 MJ/kg on average) in comparison to the average calorific value of impoundments in analytical state i.e. 16.4 MJ/kg. Average ash and sulfur contents of the coal slurries in analytical state is on average: 42.5% and 1.0% respectively. Transient moisture content of coal slurries in the analytical state is on average 22%, whereas the average volatile matter content is 20.0% Chemical composition is typical for coal tailings with low Al2O3 and TiO2 content. The results indicate considerable variations in the quality of coal slurries deposited in different impoundments due to different geology of coal deposits of the mines. For individual impoundment these differences are smaller which is demonstrated by a lower variation in the standard deviation.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2013, 49, 1; 23-35
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparison of surface properties of anthracite coals before and after high temperature heating process
    Autorzy:
    Xia, W.
    Xie, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/951846.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    heating
    coal hydrophobicity
    XPS
    SEM
    BET
    contact angle
    Opis:
    Surface property plays a very important role on coal hydrophobicity which determines flotation behavior of fine coals. However, coal spontaneous combustion makes coal suffer both oxidation and high temperature heating processes. Coals from the outside of coal piles primarily suffer oxidation (or combustion process) while coals from the inside of coal piles primarily suffer high temperature heating process. It is necessary to investigate the changes in surface properties of coal before and after high temperature heating process. In this investigation, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), surface area (BET) and contact angle measurements were used to indicate the changes in surface properties of anthracite coal before and after high temperature heating process. Throughout this study, surface properties of coal changed significantly after high temperature heating process. Meanwhile, coal hydrophobicity can be also reduced after high temperature heating.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2015, 51, 1; 205-212
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of particle properties on rheology of low-concentration coal suspensions
    Autorzy:
    Hou, Jinying
    Ma, Xiaomin
    Fan, Yuping
    Dong, Xianshu
    Yao, Suling
    Powiązania:
    https://bibliotekanauki.pl/articles/1845222.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    apparent viscosity
    coal suspension
    particle property
    hydrophobicity
    effective volume
    Opis:
    In wet coal preparation, the products of some processes are transported as low-concentration suspensions. Their rheology is greatly affected by the properties of the coal particles that result from the formation and weathering during preparation. In this study, the properties of coal particles, including volumetric properties (i.e., solids content, granularity, and clay mineral fraction) and surface characteristics (i.e., dynamic potential, degree of coalification, and degree of surface oxidization), were studied to determine their effects on the apparent viscosity of low-concentration coal suspensions. With increasing solids content and smaller particle size in the suspension, the interactions between the coal particles became stronger due to the increased particle content, thus increasing the coal suspension’s apparent viscosity. Adding clay minerals to the suspension gradually changed its composition and structure and increased its viscosity. The dynamic potential of the coal particles and inter-particle electrostatic repulsive forces were reduced with the addition of Ca2+ ions, and the coal particles collided and aggregated, which increased the apparent viscosity of the suspension. For coal with a low degree of coalification or coal had been oxidized by a hydrogen peroxide solution, the suspension of the hydrophilic coal particles was associated with a lower apparent viscosity than that of highly hydrophobic solids, which tended to aggregate and form flocculent masses.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2020, 56, 5; 984-995
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Investigation of flocculation properties and floc structure of coal processing plant tailings in the presence of monovalent and divalent ions
    Autorzy:
    Gungoren, Can
    Unver, Ilgin Kursun
    Ozdemir, Orhan
    Powiązania:
    https://bibliotekanauki.pl/articles/1845206.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    coal tailings
    coagulation
    flocculation
    floc structure
    colloidal particles
    monovalent
    divalent ions
    Opis:
    Low-rank coals are generally processed with wet methods including washing, flotation, etc. Fine-sized tailings of these processes are discharged to tailing ponds with a significant amount of associated water which contains a high amount of dissolved ions. These tailings should be dewatered employing coagulation/flocculation in terms of technological and environmental aspects. In this study, the coagulation/flocculation behavior of coal processing plant tailings obtained from Manisa, Turkey was investigated in the presence of monovalent (Na+, K+) and divalent (Mg2+, Ca2+) ions and an anionic flocculant (SPP-600). First, the coagulation properties of coal tailings were determined. Then, the flocculation experiments were carried out, and the turbidity values of the suspensions were measured. Moreover, the sizes of the flocs were determined using a laser diffraction particle size analyzer to analyze the strength of the flocs. The results of the coagulation experiments showed that while divalent ions were more effective at 10-1 mol/dm3, higher settling rate and lower turbidity values were obtained in the presence of monovalent ions at 1 mol/dm3 concentration. The optimum flocculant dosage was obtained as 150 g/Mg from the flocculation experiments. The floc size and strength measurements indicated that the larger flocs were obtained with Na+ than Ca2+ in the presence of the flocculant. The strongest flocs were obtained at 10-1 mol/dm3 Ca2+ + 150 g/Mg flocculant. It can be concluded from this study that the coagulation followed by the flocculation method can be employed to obtain fast flocculation behavior and low turbidity for the dewatering of coal tailings.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2020, 56, 5; 747-758
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Properties of fatty acid/dodecylamine mixtures and their application in steam coal reverse flotation
    Autorzy:
    Shen, L.
    Wang, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/109571.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    steam coal
    surfactant mixture
    reverse flotation
    fatty acids
    surface activity
    Opis:
    A series of surfactant mixtures which consist of DAH (dodecylamine hydrochloride) and fatty acids (FAD) were made in this study. The characteristics of these fatty acids/DAH mixtures, including surface tension, critical micelle concentration (CMC) and adsorption onto coal were investigated. The reverse flotation results with these fatty acids/DAH mixtures (FAD) and DAH were compared with each other. Experimental results showed that the fatty acids/ DAH mixtures have lower CMC and γcmc than DAH. The adsorption test indicated that more amine molecules would adsorb preferentially onto the bubbles surface in FAD solutions than that in DAH solutions. Reverse flotation results showed that about 50% surfactant dosage was saved under the same froth product yield. Only 28% froth product yield was obtained in the presence of 1.66 kg/Mg DAH. However, when 0.83 kg/Mg hexadecanoic acid/DAH mixture (C16D) surfactant was used, the froth product yield reached 29%. Dodecanoic acid/DAH mixture (C12D) surfactant a showed better performance with a high mineral matter recovery similar to that with tetradecanoic acid/DAH mixture (C14D) and higher combustible recovery than with C14D and C16D.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2016, 52, 1; 303-316
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Research on preparation and properties of porous ceramsites sintered with high-ash coal slime
    Autorzy:
    Zhu, Dan
    Min, Fanfei
    Lv, Wenbao
    Powiązania:
    https://bibliotekanauki.pl/articles/27323640.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    high-ash coal slime
    porous ceramsites
    sintering temperature
    ash content
    Opis:
    In order to realize the resource and harmless utilization of high-ash coal slime in coal preparation plants, porous ceramsites were prepared by the high-temperature sintering method with coal slime as raw material. The influences of sintering temperature, sintering time and ash content on the properties of porous ceramsites were studied by experiments, and the phase composition, micro-morphology and pore structure characteristics of ceramsites were analyzed by XRD, SEM and BET. The experimental results showed that with the increase of sintering temperature and sintering time, the amount of molten liquid in ceramsite green bodies increased, the densification degree of ceramsites increased gradually, the bulk density and the apparent density increased gradually, and the water absorption and the apparent porosity decreased gradually. However, with the increase of coal slime ash content, the quantity of pores within ceramsites increased first and then decreased. When the coal slime ash content was 55%, the bulk density of porous ceramsite sample was 0.549g/cm3, the water absorption rate was 64.63%, the specific surface area was 19.40m2/g, the crushing rate and wear rate were 0.14%, with rough surface, porous structure and excellent water absorption performance, which met the optimum performance requirements of porous ceramsites. At the same time, this research also provides a new idea and method for the reuse of high-ash coal slime resource, a by-product of coal washing and dressing.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2023, 59, 6; art. no. 172665
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of controlled dispersion on rheology of swelling clay suspensions in the presence of coal flotation reagents
    Autorzy:
    Zhang, M.
    Cao, Y.
    Chen, Y.
    Yu, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/110619.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    swelling clay
    rheological properties
    controlled dispersion
    flotation reagents
    Opis:
    Swelling clay minerals, which are innately capable of dispersing into thin flakes in water, can significantly depress coal flotation. Some researchers partially attribute depression to pulp viscosity increments. This study sought to understand the role of swelling clay minerals in fine coal flotation, by investigating the rheological behavior of bentonite suspensions under controlled and uncontrolled dispersion conditions. The effect of collector, frother, and solution pH on rheological properties of the pulp was studied. Findings showed that at a natural pH, Newtonian flow properties were displayed when bentonite was directly added into a swelling suppressed solution containing calcium ions. The same process was repeated under uncontrolled conditions, and the suspensions transferred from Newtonian to non-Newtonian flows with pseudo-plastic characteristics, depending on the solid density. Further, pH value, methyl isobutyl carbinol (MIBC) and kerosene had the potential to alter the rheological behavior of controlled and uncontrolled systems, especially pH value in the uncontrolled system.
    Źródło:
    Physicochemical Problems of Mineral Processing; 2017, 53, 2; 1148-1160
    1643-1049
    2084-4735
    Pojawia się w:
    Physicochemical Problems of Mineral Processing
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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