PRESSURIZED FLUIDIZED-BED COMBUSTION ASH .2. SOIL AND MINE SPOIL AMENDMENT USE OPTIONS

The commercial introduction of pressurized fluidized bed combustion (P FBC) has spurred evaluation of ash management options for this technol ogy. Ashes used in this study were produced in the Foster Wheeler Ener gia Oy's circulating PFBC pilot facility in Karhula, Finland and the A merican Electric Power Tidd PFBC facility in Ohio. The fly ashes conta in numerous compounds, including calcite (CaCO3), anhydrite (CaSO4) an d, in the Tidd By ash, dolomite [CaMg(CO3)(2)], that have the potentia l to be a nutrient source and a soil amendment for the reclamation of acid and sodic soils (soils influenced by high levels of sodium). The objective of this research was to determine if the PFBC ash could be u sed as soil amendments for acid and sodic soils. The research effort c onsisted of three separate tests: (1) a laboratory equilibration study to determine the influence of By ash amendments on pH and EC (electri cal conductivity) of actively oxidizing, acid-forming, mine spoil mate rial, (2) a greenhouse study to determine the influence of fly ash on plant growth; and (3) a hydraulic conductivity evaluation of sodic soi ls treated with the PFBC fly ash materials. The study showed that the PFBC fly ashes were effective acid spoil amendments. In a comparison w ith ag-lime, the fly ash reacted with the spoil at a slower rate and t he final pH of the treated material was slightly lower (similar to 7 V ersus similar to 8). In addition, the EC of the fly-ash-treated spoil was similar to 1 mS cm(-1) higher than that associated with the ag-lim e-treated materials. The greenhouse study demonstrated that the By ash was an effective amendment for the remediation of acid spoil material s. In fact, the soils amended with fly ash supported higher plant prod uction than those amended with ag-lime These findings are possibly due to pH and nutritional effects. The hydraulic conductivity study demon strated that the application of fly ash to sodic soils resulted in enh anced permeability of the treated soil. (C) 1997 Elsevier Science Ltd.