Qualitative improvement of xylite by mechanical preparation

The experiments were performed to obtain high purity raw material for activated carbon making, by mechanical preparation of xylite recovered from the Oltenia lignite Basin. The study analyzes the most important parameters that involves the selective grinding of a representative amount of 15.7 t xylite (moisture, mineral content, botanic origin), using a production equipment (a hammer-crusher of 50 t/h) and the yields and characteristics of the fractions obtained for the activated carbon manufacturing, with high usage value. The key objectives of this study are: (1) to establish yields and quality of the fractions obtained by processing a representative amount of xylite; (2) to reveal the decisive role of the preparation stages on the characteristics of the final product; and (3) to reveal the occurrence, selection methods and preliminary assessment of the xylite reserves necessary for designing a capacity for activated carbon commercial-scale processing unit. This paper presents the results obtained at semi-industrial level of xylite preparation (by crushing and volumetric classifying), for obtaining structural unchanged variety sizes suitable for experiments to obtain activated carbon. It was proved that selective crushing and sieving is a very effective technique taking into account also obtaining the convenient output (yields of over 80%) of useful fraction of xylite (greater than 10 mm with an ash between 2.0 and 2.5%). The results point out that the higher the selection and preparation go, the more lower the ash in the upper grain size fractions. The xylite fractions represent an appropriate raw material used for activated carbon making, characterized by a pore volume of 0.32 cm3/g, developed mainly in the range of very narrow pores (over 70% under 10 Å) which give high surface area BET up to 800 m2/g for granular type, the average radius of open pores being 6-9 Å.