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

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

Contaminated water runoff from dam slopes of tailings pond of flotation plant of Zn-Pb Mississippi Valley-type ores at Bolesław near Olkusz

The paper presents results of studies on storm-generated surface runoff, a phenomenon belonging to the least known factors responsible for migration of pollutants to water environment. The results of determinations of pH, conductivity as well as content of Ca, Zn, Cd, and Pb are found to be useful as the main indicators of pollution spread by waters running from dam slopes of pond in which tailings from flotation of Zn-Pb ore are disposed. Rain water leaches fine fractions of carbonate-sulfate wastes (represented mainly by dolomite, 73%, and Fe sulfides – marcasite, up to 20%) which leads to change in character of surface runoff water to that of SO4-Ca hydro-chemical type. Among the leached metals significantly important for the environment are Zn, Cd and Pb whose concentrations exceed threshold values for surface and/or groundwater of IV quality class. Acceptable concentrations in waste waters are frequently exceeded by sulfates and incidentally by zinc. Variability of the analyzed concentration indices from the years 2008 and 2009 indicates influence of weather conditions on chemical composition of surface runoff water from slopes of tailings pond of flotation plant of MVT ores

Influence of anti-pyrogenic materials on coal mining waste's tendency to self-ignite

The aim of this work was to investigate the influence of anti-pyrogenic materials with use of Combustion By-Products (CBP) on the tendency of coal mining waste to self-ignite in laboratory conditions. The tested material sample was a mixture of coal waste with an addition of anti-pyrogenic material based on coal combustion by-products. The laboratory installation to test the properties of anti-pyrogenic materials is presented. The temperature of the tested sample as well as the concentration of carbon monoxide in exhaust gas were chosen as the parameters which determine the properties of anti-pyrogenic materials to reduce the self-heating process of coal waste. Laboratory tests of material samples were performed in a temperature range from 40 °C to 500 °C, at time interval of 350 s

Transformations of calcium sulphates in solidified carbonated volatile fluidized ashes

Carbonation of volatile fluidized ashes with the use of carbon dioxide can be a means to their transformation into a product with a possible application as an additive to cement and concrete. Currently, due to its physical-chemical characteristics and particularly because of the high concentration of free calcium oxide, the possible applications of this product are highly limited, perhaps even none existent. A significant reduction or even the complete elimination of CaO can be achieved by its transformation into calcium carbonate. In carbonated volatile fluidized ashes, two components relevant to the binding time of mortar, as well as its durability, can be found: calcium carbonates and calcium sulphates. During the investigation it was assumed that calcium carbonate, being poorly water-soluble, would not react with the remaining components of the porous water of the volatile fluidized ash. Crystalline phases of calcium sulphates, anhydrite, gypsum and bassanite occurring in bound volatile fluidized ashes after carbonation demonstrate the possibility of crystallization in the presence of calcium carbonate. In particular, a change in the concentration of bassanite indicates that this phase, as a precursor to the crystallization of gypsum, may play a significant role in the process of binding carbonated volatile ashes

Hazard from PAH compounds in the working environment during demolition of post-mining waste dumps

W pracy przedstawiono wyniki wstępnych badań dotyczących emisji do powietrza atmosferycznego zanieczyszczeń organicznych, w szczególności wielopierścieniowych węglowodorów aromatycznych (WWA) ze składowiska odpadów powęglowych. Badania miały na celu ustalenie wielkości emisji z zapożarowanej hałdy karbońskich odpadów wydobywczych oraz określenie stopnia narażenia pracowników biorących udział w pracach rozbiórkowych. Próbki gazowe pobrano w trzech różnych punktach na terenie zwałowiska odpadów powęglowych w rejonie Rudy Śląskiej (woj. śląskie) podczas prac gaśniczo-prewencyjnych. Do poboru zastosowano próbniki ze stałym sorbentem typu PUF (pianka poliuretanowa) z filtrem z włókien kwarcowych oraz aspirator. Na podstawie uzyskanych wyników wstępnie oszacowano narażenie (zawodowe i całożyciowe) pracowników uczestniczących w procesie rozbiórki zapożarowanych składowisk odpadów górniczych.The paper presents results of preliminary investigation concerning emission of organic pollution to the atmospheric air, focusing on polycyclic aromatic hydrocarbons (PAHs) from a post-mining waste dump. The goal of the research was to determine emission quantity from a burning mine-waste dump and to define exposure of workers employed in disassembly work. Gaseous samples were collected using the PUF (polyurethane foam) sampling cartridges with quartz filters and the aspirator in three different sample points during the extinguishing and prevention work on the mine-waste dumping ground located in Ruda Śląska (Upper Silesia, Poland). The research was the basis for a preliminary assessment of the exposure (professional hazard and lifelong exposure) of workers involved in the mine-waste dump disassembly process

Mechanical Properties of Polylactide Matrix Composite Reinforced with Long Maize Stalk Fibers

The aim of presented study was to investigate the effect of using long rotation maize stalk fibers as filler on the mechanical and thermomechanical properties of an injection molded biocomposite with a polylactide matrix using different fiber percentages. To evaluate the effect of maize stalk particle reinforcement on the PLA matrix, the mechanical properties of the biocomposites including tensile strength, tensile modulus, relative strain at maximum stress, strain at break, stress at break and Charpy unnotched impact strength were determined. From a mechanical point of view, the best fiber content was at 15% as it caused the least reduction in strain at break, stress at break, and strain at maximum stress relative to the polylactide matrix

Process Kinetics of the Carbonation of Fly Ashes: A Research Study

The aim of the paper is to present the results of research on the carbonation process kinetics of coal combustion ashes originating from fluidized bed boilers used in power plants. Based on the thermogravimetric analysis (TGA), the hypothesis that carbon dioxide is bounded by the mineral substances (calcium compounds) in the fly ashes was confirmed. Determining the kinetic parameters of the carbonation of fly ashes requires simultaneously taking into consideration the kinetics of the drying process of the sample. The drying process of the sample masks the effect of the reaction of CO2 with calcium compound. Unlike the ashes generated in pulverized fuel boilers, fly ashes contain irregular amorphic mineral components or poorly crystalized products of complete or partial dehydroxylation of claystone substance present in shale formations constituting the gangue as well as anhydrite (CaSO4), a desulfurization product. The content of free calcium oxide (CaO) in such ashes ranges from a few to several percent, which is a significant obstacle considering their use in cement and concrete production as type II admixtures understood to be inorganic grained materials of pozzolanic or latent hydraulic properties. The paper presents effective mechanisms which reduce the content of free CaO in ashes from Fluidized Bed Combustion (FBC) boilers to a level that allows their commercial utilization in the cement industry

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

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

Factors influencing the selection of preventive, prophylactic and extinguishing technologies used on objects formed from coal wastes

W artykule przedstawiono technologie prewencyjne, profilaktyczne i gaśnicze stosowane w kraju i za granicą na obiektach uformowanych z odpadów powęglowych, w aspekcie czynników decydujących o ich wyborze. Do najważniejszych metod prewencyjnych należą obecnie: dobór optymalnego uziarnienia składowanych odpadów powęglowych, zmniejszenie procentowego udziału zawartości węgla w materiale oraz wysokie zagęszczenie odpadów w fazie realizacji obiektu. Metody profilaktyczne, to: iniekcja otworowa i wykonywanie wierzchniej warstwy rekultywacyjnej. Metody doraźnego zwalczania zagrożenia pożarowego, to: iniekcja otworowa, wykonywanie rowów ekranujących (chłonnych) i robót ziemnych, zastosowanie gazów obojętnych i antypirogenów, a także kontrolowane przepalenie zwałowiska. W artykule podano przykłady zastosowania technologii na konkretnych obiektach wraz z oceną poszczególnych rozwiązań, stosowanego sprzętu oraz medium gaśniczego. Przeanalizowano również czynniki zewnętrzne i wewnętrzne, które zadecydowały o wyborze metody w przypadku wystąpienia podwyższonego stanu termicznego lub zjawisk pożarowych.The article presents preventive, prophylactic and extinguishing technologies used in Poland and abroad on objects formed from coal wastes in the aspect of factors deciding about their selection. To the most important preventive methods belong currently: the selection of optimum graining of disposed coal wastes, decrease of the percentage share of coal content in the material and high waste consolidation in the phase of object realisation. The prophylactic methods comprise: borehole injection and carrying out of the upper reclamation layer. The methods of immediate fighting of the fire hazard cover: borehole injection, carrying out of absorption trenches and earth work, application of inert gases and antipirogens as well as controlled burning of the dumping ground. The article presents examples of application of technologies on specific objects, along with the assessment of individual solutions, equipment used and the extinguishing medium. Moreover, external and internal factors were analysed, which decided about the selection of the method in the case of occurrence of increased thermal state and fire phenomena