COAL ASH AS A POTENTIAL SCRUBBER FOR QUARRY SLUDGE

The main fuel for electricity in Israel is Bituminous coal of which ~13Mtons of are fired in the utilities annually. The process produces ~1.4Mtons of coal fly ash and bottom ash as residues. Strict environmental regulations in Israel do not allow imports of high sulfur content in the coal, therefore the fly ashes in Israel are Class F and have high pH levels upon immersion in water due to the high lime content (South African Fly Ash -SAFA ~8.5%w, and Colombian Fly Ash -COFA, ~5%w).

As all the fly ashes and bottom ashes formed are utilized in the construction industry it's economic value is not high and research efforts are directed into determination of improved modes of utilization for these residues.

It has been found that the Class F fly ashes show excellent scrubbing and fixation properties for acidic wastes, mainly from the phosphate and oil industries, that contain variety of toxic trace elements.

This study was directed on using these fly ashes as a scrubbing reagent to fixate sludges from the marble quarries industry of the Israel and the West Bank (The Palestinian Authority).

The results showed that class F fly ashes act as an efficient encapsulation reagent for the quarry sludges. During the fixation process an aggregate is being formed, which can be used in the concrete production as a partial substitute for concrete mixture. Leaching experiments, via improved 1311 TCLP EPA and European Directive (EN12457-2) methods, proved that no leaching of toxic trace elements from the scrubbed sludge and the concrete produced did occur.