Demet Demir Sahin; Ibrahim Cavusoglu; Ali Osman Yilmaz
Abstract
Today, energy produced from coal is economical compared to other sources but it faces a very serious waste problem. However, these wastes are evaluated by using them as mineral additives in cement, which leads to lower cement costs, saving resources, producing environmentally friendly cement, reducing ...
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Today, energy produced from coal is economical compared to other sources but it faces a very serious waste problem. However, these wastes are evaluated by using them as mineral additives in cement, which leads to lower cement costs, saving resources, producing environmentally friendly cement, reducing CO2 gas, and producing high-strength cement. In this work, the pozzolanic properties of different types of fly ash (Afşin Elbistan C type and Çayırhan F type) are investigated. The fly ashes used in the study are first subjected to the milling process (10, 20, 30, 45, and 60 minutes), and then the 28 and 90-day pozzolanic activity index tests of the milled and unmilled ashes are performed. The results obtained show that the 28-day pozzolanic activity value of the ashes subjected to 20-, 30-, 45-, and 60-minute milling times are higher than the value specified in the standard, compared to the unmilled and 10 min milled fly ash. In addition, for all fly ash samples, the 90-day pozzolanic activity index results show that while the pozzolanic activity index value of Çayırhan (ÇYH) fly ash is higher than the standard value, that of Afşin Elbistan (AE) fly ash is lower than standard. The outcomes of the present study show that the mechanical properties of the fly ash are generated by the burning of coal increase after milling process, and thus can be used as a mineral additive. With the effect of grinding, both fly ash increase the pozzolanic activity. The results are determined with the experimental results obtained.
Mineral Processing
I. Kursun Unver; M. Terzi
Abstract
Today coal is among the most important energy sources. In order to meet the world's energy demands, low-calorie lignite with a high ash content is generally used in the large capacity coal-fired thermal power plants. As a result of coal firing, wastes such as fly ash, slag, and flue gas are also produced. ...
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Today coal is among the most important energy sources. In order to meet the world's energy demands, low-calorie lignite with a high ash content is generally used in the large capacity coal-fired thermal power plants. As a result of coal firing, wastes such as fly ash, slag, and flue gas are also produced. Subsequently, toxic trace elements within coal are transferred to wastes such as slag, fly ash, and flue gases. Large amounts of these, which are usually stored in collection ponds or stockpiles, are problematic in terms of environment. Although coal fly ash (CFA) has been utilized in construction and several other industries for decades, its current ratio of utilization is still quite limited. As an important fact, CFA also contains many valuable metals including germanium (Ge), gallium (Ga), vanadium (V), titanium (Ti), and aluminum (Al). In addtion, coal and CFA can be regarded as alternative sources of radioactive elements. Therefore, they also have a great potential in terms of the precious metals and trace elements they contain. In this study, the present literature on the distribution of trace elements in coal and coal ash during firing and ore preparation processes and their recovery possibilities with mineral processing practices are reviewed. While many research works on the subject clearly indicate that the large amounts of the ashes produced from firing of coal could be problematic in terms of environment, many studies and practices also show that coal combustion products also have a great potential in terms of the precious metals and trace elements.
U. Yenial; G. Bulut
Abstract
Two common waste materials, red mud and fly ash, were used to produce a new nano-hybrid adsorbent by heat treatment with alkali addition. The new zeolitic structure formation of the hybrid adsorbent was revealed using the BET surface area, XRD, and SEM analyses. This hybrid adsorbent was utilized to ...
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Two common waste materials, red mud and fly ash, were used to produce a new nano-hybrid adsorbent by heat treatment with alkali addition. The new zeolitic structure formation of the hybrid adsorbent was revealed using the BET surface area, XRD, and SEM analyses. This hybrid adsorbent was utilized to remove arsenic from synthetic and real waste waters by batch and column adsorption experiments. The parameters such as the pH, contact time, and effect of the co-existing ions were investigated. Slightly acidic media favored arsenic adsorption by the hybrid adsorbent, the same as the individual use of fly ash and red mud. The effects of ions such as Fe3+, Cu2+, Cl-, SO42-, and PO43- were investigated as the co-existing ions. It was found that arsenic adsorption increased with cationic ions and decreased with anionic ions according to their valance charge. The intra-particle diffusion model showed that adsorption took place at three different rates depending on time. The hybrid adsorbent was formed as a pellet and utilized in a column for treatment of arsenic containing real waste water. The hybrid adsorbent derived from mineral wastes was more successful than their individual usages.
