The aim of this work is to evaluate the characteristics of an activated carbon obtained from unburnt carbon in coal fly ashes to be used in the removal of NO. Carbon-rich fraction was obtained by mechanical sieving of fly ashes. The mineral matter was removed by conventional HCl and HF demineralization procedure. Activation was carried out with steam at 900 degrees C in order to develop porosity onto the sample. Characterization of samples was performed by several techniques with a main objective: to follow the mineral matter content, composition and distribution on the samples in order to better understand how to remove it from unburnt carbon in fly ashes. To study the use of this unburnt carbon as a precursor for the preparation of activated carbons for gas cleaning, the NO removal by ammonia using activated carbon as a catalyst at low temperature was performed. Results show a good performance of activated carbon in this reaction that is in relationship with BET surface area.
Carbon-enriched fractions have been obtained from two coal fly ash (FA) samples. The FA came from two pulverized-coal fired power stations (Lada and Escucha, Spain) and were collected from baghouse filters. Sieving was used to obtain carbon-enriched fractions, which were further subjected to two beneficiation processes: acid demineralization using HCl and HF, and oil agglomeration using soya oil-water. Yield in weight after sieving, unburned carbon content, and several physicochemical characteristics of the obtained fractions were used to compare the performance of the beneficiation methods. Low carbon concentration was obtained by sieving, particularly in the case of Escucha FA. However, after acid demineralization or oil agglomeration, fractions containing unburned carbon in a range of 63% to 68% were obtained. These fractions showed differences in mineral phase composition and distribution depending on the FA and on the beneficiation method used. The textural properties of the obtained fractions varied as a function of their carbon content and the beneficiation method used. However, no significant differences in morphology of the carbonaceous particles were found.
Ionic liquids (ILs) present a new alternative for postcombustion CO 2 capture because their properties can be tuned by means of different cation−anion combinations in order to obtain the most suitable properties for a specific task. This work is a novel study that investigates the absorption kinetics and evolution of the chemical transformations produced by CO 2 absorption in ILs at different temperatures. A large range of pure ILs was tested with a screening process based on the pK a anion for efficient and reversible CO 2 capture. CO 2 uptake by selected ILs was determined for a wide range of pressures between atmospheric pressure and 2000 kPa at room temperature. Results show that CO 2 absorption capacities of [bmim][Ac] and [bmim][Phen] at 100 kPa are close to those obtained at higher pressures, suggesting the existence of two solvation regimes. This was confirmed by IR analysis. The kinetics were significantly affected by the temperature and were shown to increase sharply with it. The optimum temperature for CO 2 capture in [bmim][Ac] and [bmim][Phen] was found to be 323.15 and 348.15 K, respectively.
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