Terry H. Brown

Pressurized fluidized bed combustion ash 2. Soil and mine spoil amendment use options

Abstract The commercial introduction of pressurized fluidized bed combustion (PFBC) has spurred evaluation of ash management options for this technology. ashes used in this study were produced in the Foster Wheeler Energia Oys circulating PFBC pilot facility in Karhula, Finland and the American Electric Power Tidd PFBC facility in Ohio. The fly ashes contain numerous compounds, including calcite (CaCO 3 ), anhydrite (CaSO 4 ) and, in the Tidd fly ash, dolomite [CaMg(CO 3 ) 2 ], that have the potential 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 used as soil amendments for acid and sodic soils. The research effort consisted of three separate tests: (1) a laboratory equilibration study to determine the influence of fly ash amendments on pH and EC (electrical conductivity) of actively oxidizing, acid-forming, mine spoil material; (2) a greenhouse study to determine the influence of fly ash on plant growth; and (3) a hydraulic conductivity evaluation of sodic soils treated with the PFBC fly ash materials. The study showed that the PFBC fly ashes were effective acid spoil amendments. In a comparison with ag-lime, the fly ash reacted with the spoil at a slower rate and the final pH of the treated material was slightly lower (∼7 versus ∼8). In addition, the EC of the fly-ash-treated spoil was ∼1 mS cm −1 higher than that associated with the ag-lime-treated materials. The greenhouse study demonstrated that the fly ash was an effective amendment for the remediation of acid spoil materials. In fact, the soils amended with fly ash supported higher plant production than those amended with ag-lime. These findings are possibly due to pH and nutritional effects. The hydraulic conductivity study demonstrated that the application of fly ash to sodic soils resulted in enhanced permeability of the treated soil.

Pressurized fluidized bed combustion ash 1. Construction-related use options

Ash collected from the low-sulfur subbituminous coal-fired Foster Wheeler Energia Oy pilot-scale circulating PFBC tests in Karhula, Finland, and from AEPs high-sulfur bituminous coal-fired bubbling PFBC in Brilliant, Ohio, were evaluated in laboratory and pilot-scale ash use tests. Options evaluated for these ashes were construction-related applications, such as cement production, fills and embankment, soil stabilization and synthetic aggregate production, as well as an amendment for acidic and sodic soil and mine spoil as described in Part 2 of this paper. The tests related to construction applications, described herein, led to the following conclusions. (1) PFBC ash does not meet the ASTM chemical requirements as a pozzolan for cement replacement (ASTM C618). However, there is potential for its use as a pozzolan and as a set-retardant (gypsum replacement) in type-IP Portland cement production. (2) PFBC ash shows relatively high strength development ( > 2.75 MPa), low expansion ( 27.5 MPa), manageable early expansion, and whet-dry and freeze-thaw cycle durability ( 135 kg), resistance to Los Angeles (LA) abrasion resistance (10-30 wt% loss) and soundness resistance (< 5%), making the ash an excellent material for synthetic aggregate production for construction applications. In summary, PFBC ash appears to be a viable material for use in a number of construction-related applications.

Salinity and sodicity of weathered minesoils in northwestern new Mexico and northeastern Arizona.

Evolving relationships between electrical conductivity (EC) and sodium adsorption ratio (SAR) in reconstructed soils at surface mines have been insufficiently documented in the literature. Some minesoils (i.e., rootzone material) are classified as saline, sodic, or saline-sodic and are considered unsuitable for revegetation. Weatherable minerals such as calcite and gypsum are common in alkaline minesoils and on dissolution tend to mitigate elevated SAR levels by maintaining or increasing electrolytes in the soil and providing sources of exchangeable calcium and magnesium. Topsoils (i.e., coversoils) contribute to mitigation of sodic conditions when soluble cations are translocated from coversoils into the underlying minesoils. This study evaluated the weathering characteristics of minesoils sites from three surface coal mines in northwestern New Mexico and northeastern Arizona. Minesoils were grouped into 11 classes based on EC and SAR. After 6 to 14 yr, differences between upper and lower halves of the coversoils suggest general increases occurred with EC, SAR, chloride (Cl(-)), and sulfate (SO(4)(2-)) with depth. Within the reclaimed minesoils, there were several significant (P < 0.05 or < 0.10) relationships among EC and SAR that related to Minesoil Class. Lower SAR levels with corresponding increases in EC compared to baseline minesoils were more apparent in upper minesoil depths (0-5 and 5-15 cm). Minesoil anion concentrations suggested coversoil leachates and gypsum dissolution influenced EC and SAR chemistry. Over time, chemical changes have increased the apparent stability of the saline and sodic reclaimed minesoils studied thereby reducing risks associated with potential aggregate slaking and clay particle dispersion.

MARKET ASSESSMENT AND TECHNICAL FEASIBILITY STUDY OF PRESSURIZED FLUIDIZED BED COMBUSTION ASH USE

Western Research Institute, in conjunction with the Electric Power Research Institute, Foster Wheeler International, Inc. and the US Department of Energy, has undertaken a research and demonstration program designed to examine the market potential and the technical feasibility of ash use options for PFBC ashes. Ashes from the Foster Wheeler Energia Oy pilot-scale circulating PFBC tests in Karhula, Finland, combusting (1) low-sulfur subbituminous and (2) high-sulfur bituminous coal, and ash from the AEPs high-sulfur bituminous coal-fired bubbling PFBC in Brilliant, Ohio, were evaluated in laboratory and pilot-scale ash use testing at WR1. The technical feasibility study examined the use of PFBC ash in construction-related applications, including its use as a cementing material in concrete and use in cement manufacturing, fill and embankment materials, soil stabilization agent, and use in synthetic aggregate production. Testing was also conducted to determine the technical feasibility of PFBC ash as a soil amendment for acidic and sodic problem soils and spoils encountered in agricultural and reclamation applications. The results of the technical feasibility testing indicated the following conclusions. PFBC ash does not meet the chemical requirements as a pozzolan for cement replacement. However, it does appear that potential may exist for its use in cement production as a pozzolan and/or as a set retardant. PFBC ash shows relatively high strength development, low expansion, and low permeability properties that make its use in fills and embankments promising. Testing has also indicated that PFBC ash, when mixed with low amounts of lime, develops high strengths, suitable for soil stabilization applications and synthetic aggregate production. Synthetic aggregate produced from PFBC ash is capable of meeting ASTM/AASHTO specifications for many construction applications. The residual calcium carbonate and calcium sulfate in the PFE3C ash has been shown to be of value in making PFBC ash a suitable soil amendment for acidic and sodic problem soils and mine spoils. In conclusion, PFBC ash represents a viable material for use in currently established applications for conventional coal combustion ashes. As such, PFBC ash should be viewed as a valuable resource, and commercial opportunities for these materials should be explored for planned PFBC installations.

Simulated Weathering of Saline and Sodic Minesoils from the Four Corners Region, USA∗

The effects of weathering on alkaline minesoil (root-zone material) chemistry are poorly documented in literature. Coversoils (i.e., topsoils) enhance the remediation of minesoils through physical and chemical buffering between saline/sodic root-zone material and the reconstructed soil surface. Weatherable minerals (e.g., calcite, gypsum, pyrite, and other geologic substrates) present in minesoils can also effectively remediate or mitigate elevated sodium adsorption ratio (SAR, mmol1/2 L−1/2) conditions by maintaining soil solution electrical conductivity (EC, dS m−1) levels to promote clay particle stability and by providing sources of exchangeable calcium (Ca2+) and magnesium (Mg2+). A laboratory column study was used to evaluate the weathering potential of 10 minesoil materials from three mining operations in northwestern New Mexico and northeastern Arizona. Columns consisted of: 1) 15 cm of coversoil and 2) 15 cm coversoil over 30 cm of minesoil that were subjected to leaching with simulated precipitation. Chemical evaluations of weathered materials indicated significant reductions in EC and SAR and overall improvement of minesoil quality. Results suggest the three coversoils acted as chemical buffers by supplying Ca2+ and other electrolytes to underlying saline-sodic materials, thereby enhancing remediation of minesoil materials. Generally, reduction in SAR was inversely related to minesoil SAR levels. This was partially due to the reduced irrigation treatment for minesoils with EC of 4–8 and SARs > 40 mmol1/2 L−1/2. The least amount of weathering with regard to SAR was associated with minesoils that had EC < 5.0 dS m−1 and SAR > 35 mmol1/2 L−1/2. Minesoils with a high saturation percentage and associated low hydraulic conductivity (K) values showed the least reduction in SAR levels.

Identification of the mineral phases responsible for cementation of Lurgi spent oil shale

ABSTRACT Very large volumes of solid waste are generated during oil shale retorting. The reclamation and use of these wastes are desirable from an environmental and economical point of view. Two of the primary considerations in the disposal of these wastes are their structural integrity and the leaching of toxics into groundwater. The spent shale used in this study was generated from oil shale mined from the Green River Formation in the Piceance Basin of western Colorado. The oil shale was processed using the Lurgi-Ruhrgas method (Schmalfeld 1975). The spent shale was packed in the Harvard miniature apparatus (Soiltest 1964) forming columns using three different water contents. Subsequently, the columns were allowed to cure for periods ranging from one day to eight weeks. Pour types of analyses were performed on the cured columns. X-ray diffraction (XRD), scanning electron microscopy with an energy dispersive X-ray analyzer