Showing papers on "Fly ash published in 1981"

Influence of Pozzolanic, Slag, and Chemical Admixtures on Pore Size Distribution and Permeability of Hardened Cement Pastes

Abstract: Durability of concrete is greatly influenced by the permeability of the cement paste which in turn is governed by the pore size distribution. Some mineral and chemical admixtures are known to enhance the durability of portland cement concrete. The objective of this work was to investigate how the pore size distribution and permeability of portland cement pastes are modified by the addition of pozzolanic admixtures, blast furnace slag, and chloride salts. The effectiveness of pozzolans in reducing the volume of large pores and permeability was found to depend on the reactivity of the pozzolan used. Large additions of granulated blast furnace slag increased the total pore volume, however the pore size distribution was shifted toward finer pores and therefore the permeability of the paste was reduced. Among the chloride admixtures, namely calcium, magnesium, and sodium chloride, magnesium chloride was most effective in reducing both the volume of large pores and permeability of the cement pastes.

Crystalline components of stack-collected, size-fractionated coal fly ash

Abstract: As part of a program to characterize the fly ash which is emitted by coal-fired power plants, qualitative identification and quantitative estimation of the crystalline components of four size-fractionated and one unfractionated fly ash sample are reported. Although fly ash is mostly amorphous to X-rays, the presence of small amounts of quartz, hematite, mullite, gypsum, magnetite, and ferrite have been reported (1-3). However, quantitative determinations of these mineral phases have not been reported, nor have the crystalline phases been studied as a function of particle size. A knowledge of the Crystalline phases is of importance in the consideration of the potential health effects of inhaled particles. Because of the refractory nature of the quartz, mullite, and magnetite phases, these materials will have long residence times in the pulmonary region of the respiratory tract if they are deposited there ( 4 ) . Therefore, it is important to know the particle size distribution and concentrations of these materials in stack-collected coal fly ash. Furthermore, it is generally recognized that crystalline siliceous materials are more toxic than amorphous compounds of the same composition. Such particles are known to have significant effects on lung cells ( 5 ) and appear to be important toxicants to the pulmonary macrophage, the primary effector cell for lung immunosurveillance. Magnetite may also be a hazard to health because of its ability t o occlude biologically active transition-metal ions such as Mn and Ni by isomorphous substitution in the spinel crystal lattice (2). Magnetite could thus act as a slow release carrier agent for toxic elements. For this reason we have performed analyses of the magnetic phase for those metals which are likely to be associated with the magnetic fraction of the ash. The crystalline phases are important in determining the physical and chemical properties of the ash. Data on the crystalline phases may be useful in developing methods for resource recovery from, utilization of, and disposal of the ash (2). The mechanisms of formation of the various crystalline

Variations in concentrations of organic compounds including polychlorinated dibenzo-p-dioxins and polynuclear aromatic hydrocarbons in fly ash from a municipal incinerator

Abstract: The composition of organic compounds in fly ash from municipal incinerators has been characterized for eight samples which were taken weekly from a single municipal incinerator. Samples were extracted in a Soxhlet apparatus with benzene, and concentrated extracts were analyzed by GC and GC/MS including SIM determination for polychlorinated dibenzo-p-dioxins (PCDD) and polynuclear aromatic hydrocarbons (PAH). Gas chromatograms of extracts showed large variations in numbers and concentrations of organic compounds with values of estimated total organic carbon of 1 to 60 ..mu..g/g of fly ash. Concentrations of PCDD varied between 10 and 170 ng/g, while concentrations of PAH were 6 to 1100 ng/g. Differences in concentrations of PAH were parallel to differences in concentrations of estimated total organic compounds. However, concentrations of PCDD showed no such relationship. Ratios of series of PCDD were not constant in these samples.

Strontium isotopes as tracers of airborne fly ash from coal-fired power plants

Abstract: Fly ash generated by coal-fired power plants is in part collected by filters in the emission stacks while a small portion is vented into the atmosphere. Since many of the coalfired power plants in the western United States are located in the desnrt, the ability to monitor fly ash emissions requires a chemical tracer that utilizes desert soil and plant interactions with the fly ash deposited in the desert environment. This investigation presents the results of a controlled greenhouse experiment in which a native desert plant, the brittlebush (Encelia farinosa), was grown on admixtures of desert soils and fly ash. The fly ash is strongly enriched in Sr and the brittlebush is a Sr accumulator. The data demonstrate that (1) the brittlebush isotopically equilibrates with desert soils whose fly ash components are as low as 0.25% by weight, (2) the fly ash Sr is apparently more available to the plant, than Sr derived from the soils, and (3) the difference between the87Sr/86Sr ratio of the fly ash (0.70807) and soils (0.71097 to 0.71117) warrants further investigations in the natural environment to determine the practicality of this method as a natural tracer of fly ash in the environment.

Oxidation state of arsenic in coal ash leachate

Abstract: D.; Prentice, B. A. Enuiron. Sci. Technol. 1979,13,455. ( 7 ) Fisher, G. L.; Prentice, B. A.; Silberman, D.; Ondov, J. M.; Ragaini, R. C.; Biermann, A. H.; McFarland, A. R.; Pawley, J. B. “SizeDependence of the Physical and Chemical Properties of Coal Fly Ash”. In Proceedings of the Division of Fuel Chemisty Symposium on Properties of Coal Ash, 2nd Joint Chemical Institute of CanadalAmerican Chemical Society Meeting, Montreal, Canada, May 1977 (reprints available from G. L. Fisher). (8) Silberman, D.; Fisher, G. L. Anal. Chim. Acta 1979,106,299. (9) McFarland, A. R.; Bertch, R. W.; Fisher, G. L.; Prentice, B. A. Enuiron. Sci. Technol. 1977,11,781. (10) Fisher, G. L.; Prentice, B. A.; Silberman, D.; Ondov, J. M.; Bierman, A. H.; Ragaini, R. C.; McFarland, A. R. Enuiron. Sci. Technol. 1978,12,447. (11) Hansen, L. D.; Fisher, G. L. Enuiron. Sci. Technol. 1978,14, 1111. (12) Hulett, L. D.; Weinberger, A. J.; Ferguson, N. M.; Northcutt, K. J.; Lyon, W. S. “Chemical Speciation Studies of Fly Ash”; Final Report to the Electric Power Research Institute, July 1979, Part 1, Section 1.4.1. (13) Wilson, A. D. Analyst (London) 1960,85,823-7. (14) Weast, R. C., Ed. “Handbook of Chemistry and Physics”, 55th

Method of and composition for producing a stabilized fill material

Abstract: A stabilized fill material and method of producing the stabilized fill material comprising approximately 45-80% fly ash, 1-6% cement, and 20-50% water by weight, and mixing the material and depositing it directly in water by equipment supported on previously deposited fill material to form a causeway or the like. The fill material may include up to 2% lime by weight.

The Effect of Fly Ash on Concrete Alkali-Aggregate Reaction

Abstract: Concrete aggregates may contain reactive constituents that will react with alkalies in cement causing disruptive expansions. Concrete deterioration caused by alkali-aggregate reaction can be prevented by using nonreactive aggregate or using cement with sufficiently low alkali content. However, energy conservation and pollution controls can be expected to indirectly increase the alkali content of some cements. On the other hand, the availability of nonreactive aggregate is continually reduced. Other preventive techniques, such as the use of pozzolan admixtures, can be used. But pozzolans vary in their effectiveness in reducing alkali-aggregate reactions. This paper discusses the use of fly ash pozzolan, a finely divided material collected from the exhaust flues of coal-burning power plants, to reduce alkali-aggregate reaction. The effectiveness of fly ash to reduce this reaction appears to depend, in part, on the chemical composition of the fly ash and also on the percent weight replacement of cement by fly ash.

Boron enrichment of plants and soils treated with coal ash

Abstract: The status of boron (B) in coal, fly ash and other associated residues and its impacts on soils and plants are reviewed and discussed. Laboratory and greenhouse experiments with fly ash derived from a western U.S. coal source were conducted to examine solubility of B in the ash and its mobilization in soils and plants. Increasing dilution of the fly ash aqueous system or the soil‐fly ash mix increased B solubility. Three hours of extraction were sufficient to remove all water soluble B, while extended extraction resulted in readsorption of soluble B. Acid and calcareous soils treated with up to 8% fly ash by weight and cropped under greenhouse conditions contained up to an average of 9 μg B/ml in the extract. Accumulation of B in alfalfa, bermudagrass and white clover grown on the treated soils was found dependent upon rate of application and type of soil, with white clover showing the highest accumulation. Tissue B was positively and linearly correlated with B determined in water saturation extr...

Shaped cementitious products

Abstract: Strong dense shaped articles such as pellets suitable for use as gravel substitutes are produced by the described method from solid fly ash-containing water materials obtained by a lime based dry scrubbing flue gas desulfurization operation. In this method the dry ash-containing waste powder, which also contains calcium sulfite or sulfate reaction products and unreacted lime, is first uniformly contacted with a critical amount of water and then immediately compacted at a critical compaction ratio to provide a handleable green body in which the fly ash particles are positioned with respect to one another so that the interstitial spaces are sufficient to accommodate the volumetric changes in wthe cementitious materials without any deleterious expansion of the article as the article is cured.

Coal fly ash: a review of the literature and proposed classification system with emphasis on environmental impacts. Environmental geology notes

Abstract: This comprehensive review of the scientific literature on fly ash generated by coal burning power plants cites studies reported in 284 publications up to September, 1980. General conclusions are formulated, on the basis of data compiled from this review, on the physico-chemical characteristics of the solid waste and the possible environmental impacts of its disposal.

Fly ash-derived strontium as an index to monitor deposition from coal-fired power plants.

Abstract: The combustion of western U.S. coals releases significant amounts of strontium, which is relatively enriched in the fine particles of fly ash. Fly ash-derived strontium is readily absorbed by agronomic and native plant species when incorporated in soil. The strontium-87 to strontium-86 ratios of fly ash and soils were significantly different, but similar ratios were found in fly ash and plants treated with fly ash. A technique for measuring and monitoring deposition from coal-fired power plants is inferred from the enhanced plant uptake of fly ash strontium and the similarity in the isotopic ratios of fly ash and treated plants.

Fly Ash Characteristics and Radiative Heat Transfer in Pulverized-Coal-Fired Furnaces

Abstract: The properties of a fly ash cloud which determine its radiative influence in furnaces are its dust burden, projected surface area and its mean absorption and scattering efficiency. The first property can be estimated by stoichiometry, the second by laboratory sizing of the ash and the radiative efficiencies should be related to its chemical character. Previous measurements of the absorption and scattering coefficients of ash in several power stations are interpreted in terms of these properties. The resulting estimates of the absorption index of the fly ashes are an order of magnitude higher than the dominant oxides in the ash. Ash is shown to be significant as an emitter and scatterer of radiation, with the present uncertainty in its optical properties leading to unacceptable errors in the calculation of radiative heat transfer.

Process for treating liquids wastes possessing a strong acidity

Abstract: Waste material having a pH not exceeding 2, and which have previously caused a serious disposal problem, are converted into stable, solid, useful, non-polluting products by first mixing the waste material with fly ash using about 30 to 260 parts of weight of ash for 100 parts of waste material, then neutralizing the resultant mixture using lime or calcium carbonate containing materials, next adding a calcium containing binder such as lime or Portland cement, and then solidifying the resultant mixture.

Plant Growth and Trace-Element Uptake on Acidic Coal Refuse Amended with Lime or Fly Ash

Abstract: Two commonly used revegetation species, ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.) and ‘Lincoln’ smooth brome (Bromus inermis Leyss.), were grown for 60 days in pots containing coarse coal mine refuse (referred to as gob, pH = 3.5) amended with either lime or alkaline powerplant fly ash. Both species were also grown in pots containing a silt loam surface soil as a control. Morphological growth parameters were measured over time; dry weights and shoot/root ratios were determined at harvest. Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn in the plant shoots were determined by atomic absorption spectrophotometry. Plant growth of both species was not as good on either lime- or fly ash-amended gob as it was on surface soil; however, more vigorous growth occurred on lime-amended gob than on fly ash-amended gob. Significant differences (p <0.05) in the tissue concentrations of Cd, Co, Fe, Hg, Mn, Pb, V, and Zn were found among the plants grown on the three substrates. Except for Hg and Pb, these elements were higher in plants grown on at least one of the amended-gob substrates than in plants grown on surface soil. Significant substrate differences were not observed for Al, As, Cr, Cu, Ni, and Se. The tissue concentrations of some elements—notably Al, Cu, Fe, Mn, V, and Zn—were high enough in plants from one or more of tbe substrates to either approach or exceed concentrations which have been reported to be associated with toxic effects in some plant species.

Extraction of vanadium from athabasca tar sands fly ash

Abstract: The production of refinery grade oil from the Alberta tar sands deposits as currently practiced by Suncor (formally Great Canadian Oil Sands Ltd.—GCOS) generates a substantial amount of petroleum coke fly ash which contains appreciable amounts of valuable metals such as vanadium, nickel and titanium. Although the recovery of vanadium from petroleum ash is a well established commercial practice, it is shown in the present work that such processes are not suitable for recovery of vanadium from the GCOS fly ash. The fact that the GCOS fly ash behaves so differently when compared to other petroleum fly ash is attributed to its high silicon and aluminum contents which tie up the metal values in a silica-alumina matrix. Results of experiments carried out in this investigation indicate that such matrices can be broken down by application of a sodium chloride/water roast of the carbon-free fly ash. Based on results from a series of preliminary studies, a detailed investigation was undertaken in order to define optimum conditions for a vanadium extraction process. The process developed involves a high temperature (875 to 950 °C) roasting of the fly ash in the presence of sodium chloride and water vapor carried out in a rotary screw kiln, followed by dilute sodium hydroxide atmosphereic leaching (98 °C) to solublize about 85 pet of the vanadium originally present in the fly ash. It was found that the salt roasting operation, besides enhancing vanadium recovery, also inhibits silicon dissolution during the subsequent leaching step. The salt roasting treatment is found to improve vanadium recovery significantly when the fly ash is fully oxidized. This is easily achieved by burning off the carbon present in the “as received” fly ash under excess air. The basic leaching used in the new process selectively dissolves vanadium from the roasted ash, leaving nickel and titanium untouched.

Air pollution control process and apparatus

Abstract: Improved combination wet absorber/spray-dry dry wastes collection air pollution control process and apparatus therefor, employing aqueous solutions of sodium or ammonium alkali sorbents injected in an absorber through which SO x -containing flue or process gases containing fly ash are passed. Fly ash is collected in the absorber wherein the alkali reacts with the SO x to form sodium and ammonium sulfur oxide salts liquor containing collected fly ash in slurry form, which is passed back upstream and injected into a spray dryer through which the gases pass. The heat of the gases in the spray dryer dries the slurry to a powder of salts and fly ash which is removed. The spray dryer simultaneously provides some added preliminary SO x removal.

Analysis of fly ashes produced in texas

Abstract: Five fly ashes produced in Texas from sub-bituminous coals and lignites were analyzed in terms of variability and their effect on fresh properties of mortars As these fly ashes contain significant quantities of CaO, a rapid and reliable method of determining the total CaO content was developed Using the CaO Heat Evolution Test, the CaO content can be determined in a field laboratory in less than 10 minutes The Texas fly ashes, although somewhat variable, exhibit excellent properties for use as a partial lime replacement in soil stabilization and as a partial portland cement replacement in concrete Extremely strong correlations were found between many of the physical characteristics and chemical properties of the five fly ashes (FHWA)