Interaction of molten salts with a semianthracite char at 743-1173 K. Effects on chemical composition, textural properties, and reactivity in air

The effects of chemical heat treatments of a semi-anthracite char (AC) on the mass of sample and on the composition of the mineral fraction of the material, textural properties, and reactivity in air are investigated. The starting char was first treated with a mixture of LiCl/KCl or LiCl/KCl/CaO at 743, 873, or 1173 K in N2 and the products obtained were then washed thoroughly with distilled water. The composition changes were studied by X-ray diffraction. Information on textural modifications was derived from the adsorption isotherms for CO2 at 273 K. The reactivity tests were carried out at 808, 823, and 838 K. Major mineral components of AC were quartz, mullite, muscovite and/or kaolinite, and oldhamite. The mass loss produced in the preparation of the samples was markedly influenced by the composition of the reaction mixture and also by the heat treatment temperature. The treatments of AC resulted in significant changes in the mineral fraction of the material, in particular when LiCl/KCl/CaO was used. In this case, spurrite, γ-calcium orthosilicate, gehlenite, and lithium aluminum silicate were formed. Also, the microporosity developed and the reactivity in air increased. The former effect was stronger for the LiCl/KCl-treated samples and the latter one for a larger number of the LiCl/KCl/CaO-treated samples.