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Carbonised fluidised fly ash (CFFA); a new product for mining engineering purposes (discussion of possible applications)

Łączny Marian Jacek, Rompalski Przemysław

Journal of Sustainable Mining

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2022

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Vol. 21, iss. 3

191--199

EN

The article presents and summarises the current state of research and laboratory results on the carbonation of fly ash with carbon dioxide in the context of its use in mining engineering. Based on previous publications and patent applications, the possibilities of using carbonated fly ash from fluidised bed boilers for the following applications were discussed: securing excavations particularly susceptible to fire hazards, shotcreting and securing longwalls and supports, constructing cases, securing decommissioned shafts, and others, which means wherever the use of cement is required. It was pointed out that the removal of excess free calcium oxide makes it possible to use carbonated fly ash in mining applications for placement in workings requiring increased tightness. It was also stated that carbonation allows the removal of hydrogen from fluidised fly ash (FFA) obtained during co-combustion. The research highlighted the potential and importance of granulating carbonised FFA in expanding the applications of this innovative product in mining engineering.

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Evaluation of the possibility of using granulated carbonated volatile fly ash from fluidized beds (G-CVFA) in underground mining techniques

Proksa Jadwiga, Łączny Marian Jacek, Bzowski Zbigniew

Archives of Mining Sciences

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2020

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Vol. 65, no. 4

737--750

EN

The application of fluidized fly ash in underground mining excavations is limited due to its significant content of free calcium and calcium sulfate. In order to increase the amount of utilized fly ash from fluidized beds, it should be converted to a product with properties that meet the requirements for mining applications. This research presents the results of an attempt to adapt fluidized fly ashes for use in underground mining techniques, by means of carbonation and granulation. Carbonation was performed with the use of technical carbon dioxide and resulted in the reduction of free calcium content to a value below 1%. Granulation on the other hand, resulted in obtaining a product with good physical and mechanical parameters. The performed mineralogical and chemical studies indicate that trace amounts of "binding" phases, such as basanite and/or gypsum are present in the carbonized ash. The addition of water, during the granulation of carbonized fluidized fly ash, resulted in changes in the mineral phases leading to the formation of ettringite and gypsum as well as the recrystallization of the amorphous substance. It was confirmed that the carbonization and granulation of flying fluidized ashes positively affects the possibility of using these ashes in underground mining excavations.

3

Odporność filtracyjna zawiesin twardniejących z popiołami fluidalnymi w warunkach agresji chemicznej

Falaciński P.

Prace Naukowe Politechniki Warszawskiej. Inżynieria Środowiska

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2018

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z. 76

3--101

PL

Przesłony przeciwfiltracyjne wykonywane z zawiesin twardniejących mogą być realizowane w obiektach ochrony środowiska, gdzie znajdują się w warunkach filtracyjnego oddziaływania wód zanieczyszczonych. Tym samym kluczowa stała się kwestia odporności filtracyjnej zawiesin w kontekście oddziaływania różnorodnych środowisk agresywnych chemicznie. Przedmiotem rozważań monografii były zawiesiny twardniejące cementowo-bentonitowo-wodne z dodatkiem lotnych popiołów fluidalnych ze spalania węgla kamiennego i węgla brunatnego. Głównym celem pracy było określenie odporności filtracyjnej zawiesin twardniejących w świetle długotrwałej ekspozycji na filtracyjne oddziaływanie substancji agresywnych chemicznie. Omówione zostały właściwości technologiczne i użytkowe zawiesin wraz z metodyką ich badania. Przedstawiono podstawowe pojęcia związane z korozją materiałów budowlanych i agresywnością środowisk. Sklasyfikowano czynniki mogące destrukcyjnie wpływać na trwałość przesłon przeciwfiltracyjnych z zawiesin twardniejących. Omówiono odporność zawiesin na czynniki destrukcyjne natury fizycznej, mechanicznej oraz chemicznej. W monografii zdefiniowano pojęcie odporności filtracyjnej zawiesin twardniejących, która jest rozumiana jako miara szczelności materiału (zawiesin twardniejących) i określana za pomocą przepuszczalności hydraulicznej (współczynnika przepuszczalności hydraulicznej, współczynnika filtracji). Przedstawiono metodykę oraz wyniki badań własnych przepuszczalności hydraulicznej zawiesin twardniejących cementowo-bentonitowo-popiołowo-wodnych poddanych 180-dniowej filtracji roztworów agresywnych chemicznie. Modelowano agresywność kwasową siarczanową, amonową, magnezową ługującą oraz mieszaną. Badano również zmiany współczynnika przepuszczalności hydraulicznej w czasie po filtracji zawiesin substancjami agresywnymi wobec stosowanego spoiwa. Następnie szukano korelacji pomiędzy szczelnością zawiesin a morfologią porów. Analizowano również zmiany odporności filtracyjnej badanych zawiesin w kontekście ewentualnych przemian korozyjnych. W tym celu zostały przeprowadzone badania specjalistyczne: porowatości, rentgenowskiej analizy dyfrakcyjnej, analizy termicznej oraz skaningowej mikroskopii elektronowej. W drugim etapie badań powtórzono badania specjalistyczne, uzupełnione o spektroskopię w podczerwieni, zawiesin eksponowanych przez okres 9 lat w warunkach statycznych, w roztworze kwasu azotowego. W wyniku analizy uzyskanych wyników badań oraz danych studialnych sformuowano wnioski końcowe dotyczące odporności filtracyjnej zawiesin twardniejących poddanych filtracyjnemu oddziaływaniu różnorodnych substancji agresywnych chemicznie. Określono możliwe kierunki dalszych prac badawczych.

EN

Cut-of walls made of hardening slurries may be present in environmental protection structures, where they operate under the conditions of filtration effects of contaminated waters. Therefore, the problem of filtration resistance of hardening slurries has become essential in the context of the effects of various chemically aggressive environments. The subject of the considerations have been cement-bentonite-water hardening slurries with the addition of fluidized fly-ashes from hard coal and brown coal combustion. The primary purpose of the thesis was to identify filtration resistance of hardening slurries under the conditions of long-term exposure to filtration effects of chemically aggressive substances. Technological and functional properties of hardening slurries, along with the methodology of studying them, have also been discussed. Basic terms related to corrosion of building materials and corrosiveness of environments have been presented. Factors that may destructively affect durability of cut-oft walls made of hardening slurries have been classified. Resistance of hardening slurries to destructive physical, mechanical and chemical factors has been discussed. In the monograph the notion of filtration resistance of hardening slurries has been defined, which is understood as the measure of material leak tightness (of hardening slurries) and determined by means of hydraulic conductivity (hydraulic conductivity coefficient, permeability coefficient). The originality and complementarity of the author’s own research have been indicated as compared to data published by other researchers. The methodology and the author’s own research results of hydraulic conductivity of cement bentonite-ash-water hardening slurries subjected to 180-day filtration of chemically aggressive solutions have been presented. Acid, sulphate, ammonia, magnesium, leaching and mixed aggressiveness was modelled. Changes in the hydraulic conductivity coefficient were tested over time. Then, a correlation between leak tightness of slurries and pores morphology was sought. Changes were also analysed in the filtration resistance of the examined hardening slurries in the contex of possible corrosion changes. For this purpose, specialist tests were conducted: porosity, X-ray diffraction analysis, thermal analysis and scanning electron microscopy. At the second stage of the research, the specialized tests were repeated, supplemented with. IR spectroscopy, for slurries exposed for the period of 9 years under static conditions, in a nitric acid solution. As a result of an analysis of the obtained research results and the study data, final conclusion have been formulated concerning filtration resistance of hardening slurries subjected to dynamic, filtering effect of various chemically aggressive substances. Possible directions of further research work have also been specified.

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Wykorzystanie odpadów z przemysłu ceramicznego, energetycznego i budowlanego w technologii adsorpcji

Siemiątkowski G., Nolepa A., Kiprian K.

Prace Instytutu Ceramiki i Materiałów Budowlanych

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2017

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R. 10, nr 31

51--69

PL

Artykuł jest opisem doświadczenia mającego na celu weryfikację możliwości wykorzystania pyłów ceglanych, popiołów lotnych i odpadów dennych ze spalania węgla brunatnego czy pyłów z bypassa, pochodzących z linii wypalania klinkieru w technologii adsorpcji metali ciężkich w środowisku wodnym. Wszystkie te materiały nie znajdywały dotychczas użytecznego wykorzystania, stanowiąc istotny balast odpadowy. Osiągnięte wyniki badań należy uznać za bardzo obiecujące. Analizowane odpady w opisanych w artykule warunkach doświadczenia wykazywały bardzo dobre właściwości sorpcyjne – w większości przypadków sięgające co najmniej 82% skuteczności. Na uwagę zasługuje również trwałość wiązań sorpcyjnych. Uzyskana w doświadczeniu desorpcja metali ciężkich w większości przypadków była znikoma. Pozytywne wyniki badań dają nadzieję na rychłe znalezienie użytecznego wykorzystania dla analizowanych odpadów.

EN

The article is a description of the experience aimed at verifying the possibility of using brick dust, fly ash and bottom waste from lignite combustion or bypass dust, which came from the clinker firing line in the technology of adsorption of heavy metals in the water environment. All these materials have not yet found useful use, constituting a significant waste ballast. The research results achieved should be considered very promising. The analyzed waste in the experimental conditions described in the article showed very good sorption properties – in most cases reaching at least 82% of effectiveness. Noteworthy is the durability of sorption bonds. The desorption of heavy metals obtained in the experiment was, in most cases, insignificant. Positive research results give hope for prompt finding of useful use for the analyzed waste.

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Parametry wytrzymałościowe fluidalnego popiołu lotnego z Elektrowni „Połaniec”

Gruchot A., Zydroń T., Gałowicz E.

Rocznik Ochrona Środowiska

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2015

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Tom 17, cz. 2

1622--1641

EN

Production of electricity and heat energy in Poland is largely based on the combustion of coal and lignite in power plants. Combustion of coal is associated with the production of significant quantities of wastes. Given the possibilities of their using, the most important product of combustion is fly ash and recently – fluidized fly ash. Tests on properties of fluidized fly ash are mainly focused on determining the impact of its addition on the mechanical properties of concrete or the setting time of self-hardening slurries, while little is known about its mechanical parameters. The aim of the study was to determine the impact of density, moisture content and maintenance duration on shear strength, CBR ratio and compressive strength of fluidized fly ash from Power Plant "Połaniec". The study was performed in terms of assessing their possibility of use for the purpose of road construction. CBR ratio was determined at three various values of moisture content determined from compaction curve of the fly-ash. CBR ratio tests were done for samples directly after compaction and after 4 days of the soaking in water. Shear strength was determined in a direct shear apparatus on samples compacted at a moisture content close to the optimum and three values of the compaction index IS = 0.90, 0.95 and 1.00. Determination of compressive strength was carried out on samples immediately after preparation and after 7, 14, 28 and 42 days of air, air-water and air-water maintenance process including 3, 7, and 14 cycles of freezing and de-freezing. The results revealed that in accordance with the geotechnical nomenclature the tested fluidized fly-ash's grain-size distribution corresponds to sandy silts. The fly-ash has high value of maximum dry density. CBR ratio of fly-ash samples after 4 days of soaking in water were very high and ranged from 199 to 277%. It can be underline that in case of both tests series, the obtained CBR indexes were positively correlated with increasing initial moisture content of tested samples. The parameters of the shear strength were high. It was stated that the higher values of compaction indexes, the higher values of the angle of internal friction and cohesion were obtained. The compressive strength of samples was high, ranging from over 2.2 MPa to approximately 6.0 MPa. The largest increase in strength was obtained after 7 days of maintenance. The maximum values of compressive strength after 42 days of maintenance, were obtained for samples which were subjected to air and air-water maintenance process. Freeze-thaw resistance index value obtained for a short 3 cycles of freezing and de-freezing process was greater than 1.0, which means that tested fly-ash was not prone to freezing process. Increasing number of freezing and de-freezing cycles affected the freeze-thaw resistance index value, which was well below 1.0, indicating a significant loss of compressive strength. To sum up, the test results on the fluidized fly ash from Power Plant "Połaniec" revealed that the fly-ash has good compaction properties, bearing capacity and shear strength. In contrast, the particle size of the fly-ash is unfavorable from the viewpoint of its use in road embankments. In turn, the results of the CBR and compressive strength tests confirmed the presence of hydration properties of fluidized fly ash thus indicating the possibility of its use in road hydraulic binders.

6

Durability of autoclaved aerated concrete produced from fluidized fly ash

Drabik M., Balkovic S., Peteja M.

Cement Wapno Beton

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2011

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nr spec.

29-33

EN

The properties of autoclaved aerated concrete (AAC) formed with the utilization of modified raw materials - new generation of fly ash from coal power plants (fluidized fly ash) were studied. The fluidized fly ash is a mixture of bed material and fly ash in the ratio 2:1. The high content of CaSO4, CaO and clay minerals (illit, diaspor) has been proved during the chemical and phase composition investigations. The fluidized fly ash was used as 0%, 30% and 100 % component of the raw mixture respectively. The AAC produced commercially (with fly ash from classical combustion) was used as reference material. The results of long-range experiments, aimed at the durability characteristics within the three years tests, are comprehensively discussed. The strength of samples decreases with the addition of fluidized fly ash, the lowest values are exhibited by samples with 100 % fluidized fly ash content in the raw mixture. The X-ray analysis, TG and OTA, IR spectroscopy, electron microscopy and EOX spectroscopy have been employed. Both phase analysis and strength data show the higher tendency of samples with fluidized fly ash towards the thaumasite formation, being the result of partial conversion of hydraulic C-S-H and tobermorite-Iike phases to nonbinding thaumasite. However, the expansion of tested samples resulted from the formation of thaumasite, as well as gypsum and ettringite in AAC, does not imply the deterioration on such a scale as observed in the concretes. The difference is due to the porosity and pore structure in AAC, developed as a result of air drying. These data contribute also to the discussion of topics of thaumasite formation vs. thaumasite sulfate attack. The results represent a basis of the proposals of modified production of AAC.