Mineralogy Optimization for Metal and Chloride Immobilization in Co-Disposed Flue Gas Desulfurization Brines and Bituminous Coal Fly Ash

Investigator: Georgia Institute of Technology

Start Date:
November 2016

Award Amount:
$195,917

The United States coal-fired power industry faces increasing demands to improve coal fly ash (CFA) and flue gas desulfurization (FGD) wastewater disposal practices. The zero liquid discharge (ZLD) options for FGD wastewater are attractive but the ZLD residuals present new challenge for the solid waste industry due to significant concentrations of mobile heavy metals and Cl-. We have developed a novel ZLD method by coupling brine concentration with a solidification/stabilization (S/S) process through co-disposing FGD brine with CFA and a pozzolanic agent. The immobilization of oxyanions (particularly SeVI) and Cl- by S/S of concentrated FGD brines and CFA from bituminous coal plants is most challenging.

Thus, this project aims to optimize the immobilization of SeVI, and Cl- in the co-disposed concentrated FGD brines and bituminous CFA (BCFA) by S/S. The specific research objectives are to (1) optimize oxyanion immobilization in concentrated FGD brine S/S with BCFA through a combination of chemical reduction and chemical incorporation in cement minerals, (2) evaluate BCFA S/S conditions including temperature, pH, CaO content, temperature, and reactive Al2O3 that promote chemical incorporation of oxyanions and Cl- in the AFm phase, (3) evaluate the stability of immobilized oxyanions and Cl- in short- and long-term leaching tests under varied conditions, and (4) optimize the impact of S/S solid mineralogy on oxyanion and Cl- stabilization over the short- and long-term.