Abstract
The effect of organic halide atmospheres at calcination of limestone on the particle size and shape of a calcined product and the final product, hydrated lime, has been investigated. To prepare the organic halide atmospheres, tetrachloromethane or 1, 1, 1, 2-tetrafluoroethane (HFC134a) was introduced with air stream during the calcination of limestone at temperature range from 1000 to 1200°C. The degree of shrinkage of the calcined product and the fractional part of the dry-hydrated lime passed through 45 μm sieve were measured using four kinds of the limestones, and compared with the result obtained by the same procedure under an air atmosphere.
As the results, the influence of grain size of the limestones was found to be, on the whole, reduced under the organic halide atmospheres. In particular the tetrachloromethane atmosphere contributed to decrease the degree of shrinkage of the calcined product and to increase the fractional part of the fine hydrated lime, while the HFC134a atmosphere resulted to increase the degree of shrinkage, but not to influence for the fractional part of the fine hydrated lime. The change in the particle size and shape of the calcined product and hydrated lime was also observed using scanning electron microscopy. In addition, considerable amounts of the halogens in the organic halide atmospheres fixed in the calcined products depending on the calcination conditions. This calcination process can be expected as the process for improving the physical properties of the resulting quicklime and hydrated lime, simultaneously accompanying with the treatment of waste organic halide compounds.
