Thomas L. Robl

Comparison of the HF-HCl and HF-BF3 maceration techniques and the chemistry of resultant organic concentrates

Abstract The common approach used to concentrate and isolate dispersed organic matter and to demineralize coal is by attack with HF. This reagent reacts with silicates to form SiF 4 , a volatile gas, and leaves the organic matter largely unaltered. Hydrofluoric acid also reacts with other inorganics to form fluoride salts, the most important being CaF 2 which is very insoluble. Hydrochloric acid is usually used as a pretreatment to remove carbonate minerals and to inhibit fluoride salt formation in the final deashing step with HF. The approach taken in this work is to selectively dissolve neo-formed fluorides in a two step demineralizing process, by reaction with BF 3 , which is a highly water soluble gas. The BF 3 is generated by the reaction of H 3 BO 3 with HF, in water. It then reacts with neo-formed fluoride salts to form water soluble fluoroborates. Several coals and organic rich sediments were demineralized with both techniques. The total ash in the test samples varied from ∼1% in samples of Wyoming subbituminous coal and a North Dakota lignite to 33% in an Irati oil shale sample. For high ash samples, the HF-BF 3 technique resulted in a final deashed product which is lower in ash by an average of 19% over those from the HF-HCl technique. Elemental analysis, FTIR and microscopic examination did not indicate any relative difference in organic alteration. The HF-HCl macerated samples however, were found to have a much higher Cl and F content, suggesting a lesser degree of organic alteration for HF-BF 3 macerated samples.

Characterization of fly ash from Kentucky power plants

Abstract Fly ashes from 21 Kentucky power plants were grouped according to the sulfur content of the feed coal. The highest-carbon fly ashes tended to be from the lowest-sulfur feed coals, partly because many of those plants were smaller and older than the higher-sulfur units. Iron oxide content increased at the expense of aluminium and silicon oxides in the higher-sulfur feed ashes. An increase in calcium and magnesium oxides towards the higher-sulfur feed ashes was due to the greater abundance of carbonate minerals in the higher-sulfur Illinois Basin coals. The highest arsenic values were among electrostatic precipitator ashes from medium-sulfur sources. The arsenic and lead contents of low- and medium-sulfur central Appalachian coals could be higher than those of high-sulfur Illinois Basin coals. Where direct comparison of fly ash and bottom ash was possible, the bottom ash was enriched in Fe 2 O 3 relative to the fly ash and most minor elements were depleted in the bottom ash relative to the fly ash. TCLP testing of selected fly ashes indicated that all of the leachates would pass the established RCRA limits. Some of the higher As and Cr levels were from fly ashes in the highest-sulfur category. For As, though, there is no significant correlation between fly ash As and leachate As.

Changes in the quality of coal combustion by-products produced by Kentucky power plants, 1978 to 1997 : consequences of Clean Air Act directives

The original US Clean Air Act (CAA), implemented by the Environmental Protection Agency in 1971, and the amendments to the act in 1977 and 1990 have required a considerable evolution of the quality of coal burned by utilities and in the type pollution control equipment needed to reduce SO2 and NOx emissions. Any change in coal quality or emission’s control implies a change in the amount, type, and quality of coal combustion by-products (CCB). CCB is a collective term for fly ash, bottom ash and boiler slag, and flue-gas desulfurization (FGD) or fluidized-bed combustion produced in coal burning. Studies by the University of Kentucky in 1978, 1992, and 1997, the latter two conducted by the Center for Applied Energy Research, have focussed on the amount, quality, and end use of CCBs from Kentucky power plants, with particular emphasis on fly ash. The evolution of clean air standards has impacted the quality and volume of CCBs in a variety of ways: (1) switching from high sulfur to lower sulfur coal generates lower quantities of spinel phases and greater amounts of alumino-silicate glasses; (2) switching to Powder River Basin subbituminous coals produces Class C fly ash, compared to Class F fly ash from the combustion of the typical eastern bituminous coals; (3) the wider use of beneficiated coals reduces the amount of fly ash and bottom ash produced; (4) use of a wider rank range into the coal blend increases the potential of unburned carbon caused by inefficient combustion of non-design coals; (5) the inclusion of non-coal fuels, such as petroleum coke and with tire-derived fuel, in the coal blend; (6) reduction of NOx emissions has generally meant an initial increase in the amount of carbon in the fly ash; (7) addition of FGD means an added CCB stream, either a calcium sulfite which in generally mixed with fly ash and landfilled, or a calcium sulfate, which is sold for wallboard manufacture. The modification of the petrology and chemistry of the fly ash impacts the potential for utilization.

Case study of the conversion of tangential- and wall-fired units to low-NOx combustion: Impact on fly ash quality

Conversion of boilers to low-NOx combustion can influence fly ash quality in terms of the amount and forms of carbon, the overall fly ash fineness, and the relative amount of glass versus crystalline inorganic phases. All of these factors can influence the potential for a fly ash to be marketed for utilization. In this study, three coal-fired combustors, two tangentially fired and one wall-fired, all burning high-sulfur Illinois coal at the same power plant, were studied before and after conversion to low-NOx combustion. In all cases, the post-conversion fly ash was higher in carbon than the pre-conversion ash from the same unit. The fly ashes in at least two of the units would appear to have post-conversion ashes which still fall within the regional guidelines for the limit of carbon (or loss on ignition).

Pervious Concrete: Compaction and Aggregate Gradation

Pervious concrete is very different from traditional portland-cement concrete (PCC). Therefore, there are open questions regarding the suitability of the current standard concrete testing protocols as they may be applied to pervious concrete. There are unique features associated with pervious concrete that may require special testing considerations. This paper examines the compaction and consolidation of pervious concrete. This study presents cylindrical specimen preparation techniques that will produce laboratory specimens that are similar to the field pervious concrete slab. Additionally, a simple correlation is provided that allows concrete designers to estimate the porosity ofpervious concrete based on its aggregate bulk density when crushed limestone is used. This practical tool saves time when designing pervious concrete mixtures.

Application of hot stage micro-FT-i.r. to the study of organic functional group changes during pyrolysis

Abstract A modified Leitz hot stage fitted to a Spectra-Tech microscope and interfaced with a Nicolet 20-SXC Fourier transform infrared (FT-i.r.) analyser was used to collect infrared (i.r.) spectra from a series of heat treated coal or kerogen samples. Hot stage modifications included installation of an i.r. transparent ZnSe cover disc and routing of a microthermocouple to the interior of a 50 μl platinum sample pan. Spectra were collected in the reflected light mode prior to and then during or after heat treatment. This provided a means to monitor organic functional group changes or depletion resulting from heat treatment. Obstacles encountered and their solutions are discussed.

Changes in the quality of coal delivered to Kentucky power plants, 1978 to 1997: responses to Clean Air Act directives

Abstract Burning of coal supplies more than 95% of the electricity generated in Kentucky. Coal-burning utilities have responded to evolving clean air standards in a number of ways, including adding flue-gas desulfurization (FGD) to existing plants or switching to lower sulfur coals. No power plant in Kentucky burned 2 reduction option. The expansion of FGD has maintained a market for higher sulfur coal. The newest power plants were designed in tandem with the FGD system and can handle coals with >4% sulfur. Quality of delivered coals has changed significantly over the past 20 years, and will continue to change as coal-fired power plants continue to work to meet the challenges presented by existing and potential new clean air standards.

Organic petrography of Mississippian and Devonian shales in east-central Kentucky

The Devonian and Mississippian oil shales of east-central Kentucky are classified as marinites. The petrographic composition of the kerogen in the shales is complex, and significant amounts of macerals from all of the major groups are present. Unfigured alginite (lamalginite) and bituminite are the most abundant macerals present, followed by vitrinite and inertinite (fusinite and semifusinite). Figured alginite (telalginite) includes Leosphoridia and Tasmanites; a minor amount of sporinite (~1% or less) is also present. The maceral composition of the Cleveland and Sunbury Shale interval from a core taken in Fleming County, Kentucky was determined quantitatively. The liptinite suite in the Sunbury interval was dominated by bituminite, while the Cleveland contained higher proportions of alginite. The total amount of inertinite plus vitrinite was found to be relatively constant. Variations in maceral composition affect the scatter of Fischer assay oil yield versus organic carbon relations for Eastern US oil shale. The kerogen macerals were found to correlate selectively with certain trace elements (e.g. Cr, Cu, V and Zn), suggesting that the maceral composition may be related to shale provenance. Bituminite:alginite ratio was found to correlate selectively with trace element concentration and supports the concept that the organic precursors for this maceral were bacterial decay products.

Interfacial Bond between Reinforcing Fibers and Calcium Sulfoaluminate Cements: Fiber Pullout Characteristics

The results of an experimental investigation on the influence of the interfacial bond of reinforcing fibers embedded in a calcium sulfoaluminate matrix on the fiber-pullout peak load and energy consumption are presented. Bonding at the fiber-matrix interface plays an important role in controlling the mechanical performance of cementitious composites - in particular, composites formed from sulfate-based systems (calcium sulfoaluminate [CSA] cements), as opposed to the silicate systems found in portland cement. Various types of fibers were selected, including polyvinyl alcohol (PVA), polypropylene, and copper-coated steel. The fibers were embedded in three different matrixes: two sulfate-based cements including one commercially available CSA cement and a CSA fabricated from coal-combustion by-products. The third matrix was a silicate-based ordinary portland cement (OPC). In this study, the results of the single-fiber pullout test were coupled with scanning electron microscopy (SEM) to examine the interfacial bond between the fiber and CSA matrix for evidence of debonding and possible hydration reaction products.

Using digital mapping techniques to evaluate beneficiation potential in a coal ash pond

Abstract Coal-fired power plants produce energy and many by-products (unburned carbon, fly ash, and bottom ash) that are normally stored in permitted ponds and landfills. When the storage facility fills to capacity, it is necessary to haul material off-site for disposal, construct a new storage facility, or find a use for some of the material. Because certain criteria must be met to successfully beneficiate the ash, mapping the ash reserve provides data that shows where the most promising recovery sites will be. The University of Kentucky Center for Applied Energy Research (CAER) in conjunction with Western Kentucky Energy (WKE) and the US Department of Energy are constructing an ash beneficiation plant to recover high quality fuel and lightweight aggregate from the ash ponds at WKEs Coleman Station in Hawesville, KY. To determine the locations of the most productive areas, an extensive sampling and mapping project is underway. An amphibious ATV-mounted hydraulic drill has been employed to take core samples throughout the pond. These samples are then evaluated for particle size distribution, carbon content, chemical and leaching properties. With this information as well as each drill-holes GPS coordinates and aerial photographs of the plant site, digital maps have been produced showing trends of deposition of material in the pond. Using a Geographical Information System to compile the data, the feasibility of removing ash for beneficial re-use can assessed.