Recycling of coal combustion wastes.

The separation of unburned carbon from coal-fired power plant bottom ashes was conducted in order to increase the possibility of the recycling of coal combustion wastes. A two-stage flotation technique was used for this study. In the rougher flotation experiments the amounts of collector, dispersant and frother, pulp density, pH, particle size distribution, flotation time and flotation temperature were tested as variables. After rougher flotation experiments, at optimum conditions, the carbon content of the concentrate increased from 13.85 to 51.54% at a carbon recovery of 54.54%. Under the same conditions, the carbon content was reduced to 4.54% at a weight yield of over 80% in the tailings fraction. This fraction meets the industrial specifications and can be utilized as a cement additive. After the cleaner flotation experiment the carbon content of the product was enhanced to 64.81% with a 52.16% carbon recovery. This fraction can be blended back into the coal feed to the power plant boilers.

Beneficiation of graphite fines from moulding factory wastes.

As the costs of waste disposal increase, more attention is being placed upon the re-use and recycling of valuable minerals contained within the waste streams. In this article, the waste streams from a moulding factory were treated by physical methods to obtain a re-usable graphite fraction. Multi-gravity separators (MGS) and shaking tables (ST) are being used in coal processing and heavy minerals beneficiation. In the present study, the possibility of using an MGS and ST to separate graphite from moulding sand was analysed as part of such investigations. The effects of changes in different process variables on the concentrate sand content and graphite recovery values were studied. Several parameters, thought to have an effect on the separation were tested. After the ST experiments, a graphite concentrate was obtained having 4.5% sand content with 60.8% recovery. After the investigations carried out by MGS, a graphite concentrate was obtained having 0.95% sand content with 68.0% recovery. The results demonstrated that recovered graphite fractions can be re-used in the factory, thus reducing the quantity of waste and costs.