Showing papers on "Fly ash published in 1978"

Physical and morphological studies of size-classified coal fly ash

Abstract: A study of the physical and morphological properties of four fractions of size-classified coal fly ash is reported. Volume medium diameters of the four size fractions are 2.2, 3.2, 6.3, and 20 millimicron, respectively. The size distributions of the four fractions are compared to isokinetically collected samples. Density variations and results of three standard particle sizing techniques are discussed in terms of particle size and morphological properties. Eleven morphological particle types are quantified by light microscopy. Relative abundances of the 11 morphological particle types within each size cut appear to be particle size dependent. The finest fraction is composed of 87% nonopaque solid spheres and 7.9% cenospheres in contrast to the coarsest fraction composed of 26% nonopaque solid spheres and 41% cenospheres. The density variation with particle size is explained in terms of the relative abundances of predominant particle types. On the basis of morphological appearance, a coal fly ash morphogenesis scheme is developed. /Author/

Mutagenicity of filtrates from respirable coal fly ash

Abstract: Incubation of histidine-requiring auxotrophs of the bacterium Salmonella typhimurium with cyclohexane-, saline-, and serum-soluble surface components of respirable fly ash particles produced an increased number of revertants in two frameshift tester strains. The results are consistent with the hypothesis that both organic and inorganic mutagens are present in coal fly ash.

Separation and chemical characterization of finely-sized fly-ash particles

Abstract: The concentrations of 43 major, minor, and trace elements were measured by x-ray fluorescence, atomic absorption, and instrumental neutron activation for nine well-defined size fractions, with mass median diameters of 0.5 ..mu.. to 50 ..mu..m, of fly ash from a western coal-fired steam plant. There was generally good agreement in concentrations of elements analyzed by more than one technique. Concentration profiles as a function of mean particle size were established for various elements. Based on the concentration profiles, the elements can be divided into three distinct groups. One group consists primarily of the volatile elements or elements partially volatilized during coal combustion (examples include As, Se, Zn, Ga, etc.), and their concentrations decrease with increasing particle size. A second group, which shows a minor or direct dependence on particle size, as in the case of Si, is apparently associated primarily with the fly-ash matrix. The last group of elements, which includes Ca, Sr, Y, and the rare earths, shows small changes in their concentration profiles with a maximum in concentration at approximately 5 ..mu..m. 6 tables, 6 figures.

Laboratory measurements of ground water leaching and transport of pollutants produced during underground coal gasification

Abstract: Two series of laboratory experiments dealing with release and migration of pollutants produced during underground coal gasification are discussed. In the first series of experiments coal ash samples prepared by heat treatment to 1000, 1100, and 1200/sup 0/C have been subjected to water leaching at 23/sup 0/C. The leachate, was analyzed for concentrations of Ca, K, Al, Ba, Fe, SO/sub 4/, OH, Mg, and Na ions likely to be present. The data provide a quantitative picture of the amount and rate of release of these various elements from coal ash left underground. Furthermore, the measured concentrations of the various elements studied in the laboratory experiments are generally in good agreement with results from ground water measurements conducted at the LLL Hoe Creek 1 coal gasification site. A second set of experiments deals with transport of pollutants away from a gasification site by the natural ground water flow through the coal seam. Two idealized cases have been studied: transport of NaBr and transport of phenol. The experiments were carried out by flowing solutions of these materials through a 1.5 m packed column of coal and measuring the breakthrough curves at various points along the column. The results are analyzed using amore » simple one-dimensional transport model. The results show the strong adsorption of phenol by the coal (K/sub d/ = 40). These results are compared with recent measurements of the cocentration of phenolic material left near an underground gasifier.« less

Portland cement-fly ash-aggregate concretes

Abstract: Concretes containing Portland cement, fly ash and aggregate are disclosed which are capable of attaining high compressive strength and which contain relatively low proportions of Portland cement and relatively high proportions of a select fly ash component. The inventive concretes may be formulated as highly dense masses particularly suited for use in the manner of conventional structural concretes in buildings, bridges, dams, etc. Comparatively low density concrete masses may also be produced which are light in weight and have thermal insulation value rendering them particularly suited for use as thermal insulating components of roofs and as protective coatings for a variety of substrates.

Treatment of hazardous waste

Abstract: Oily wastes which are immiscible with water are treated by mixing them with powdered chalk or other absorbent substance and a liquid hazardous waste. The mixture thus obtained then has added to it cement and fly ash thereby producing a slurry which sets into a detoxified rock.

Availability of sulfur in fly ash to plants

Abstract: Fly ash from a coal-fired power plant was added to soil in variable amounts and the availability of sulfur to a variety of plant species from this source was compared to that of gypsum. The study was conducted under greenhouse conditions with a calcareous and two acid soils which were low in plant-available sulfur. The fly ash used contained 0.4% S, all of which is extractable by NH/sub 4/OAc. When mixed with a calcareous and an acid soil at rates of 1 to 2% by weight, the fly ash corrected a S deficiency in the soil and maximized the yield of alfalfa (Medicago sativa L.) and bermudagrass (Cynodon dactylon L.). The increase in yield (twofold to threefold in alfalfa and 40 to 70% in bermudagrass) was accompanied by an increase in the S content of the plant tops from a deficiency level (<0.1%) to a sufficiency level (greater than or equal to 0.2%). The availability of fly ash-S and gypsum (CaSO/sub 4/ . 2H/sub 2/O)-S was compared by the addition of equal amounts of S from the two sources (25-, 50-, and 100-mg S/kg soil) to an acid soil. Yield and S content of turnip (Brassica rapa L.) and whitemore » clover (Trifolium repens L.) were equally improved, demonstrating that the availability of fly ash derived-S is equivalent to that of gympsum-S.« less

Method and apparatus for conditioning flue gas with a mist of H{HD 2{B SO{HD 4

Abstract: In order to reduce the electrical resistance of entrained fine particles of fly ash resulting from the burning of low sulfur coal and to enhance the efficiency of their collection by an electrical precipitator means, there is a conditioning of the particles carried in the flue gas stream by having a very fine mist of H2SO4 condensed and adsorbed on the particles themselves. Sulfuric acid is mixed with air in an acoustic nozzle to form a mist having a mean particle size of less than 10 microns which is injected uniformly into the flue gas stream at a zone ahead of the precipitator unit so that the acid can condense on the particles. The acid is preferably transported through the apparatus at ambient temperature and then heated just prior to injection to a temperature less than its vaporization temperature.

Elemental deposition downwind of a coal-fired power plant

Abstract: Dry deposition of fly ash emitted by a coal-fired power plant has been calculated using a surface depletion Gaussian plume model. The subject plant is located in the southwestern United States. Soil samples collected downwind of this power plant have been chemically analyzed for selected trace elements (As, B, F, Hg, Se, Sr, U, and V) to determine concentration vs. distance trends. Gaussian plume deposition calculations predict very little increase of trace element concentrations in soils, except for those elements highly concentrated in fly ash emissions compared to soils. Trace element soil concentrations as a function of downwind distance generally confirm these predictions, with the possible exception of Se.

Process for converting coal ash slag into portland cement

Abstract: Disclosed is a manufacturing process for converting coal ash slag from a slagging coal gasifier into a marketable cement product having the characteristics and qualities of portland cement. This process comprises the steps of transferring molten slag from a slagging coal gasifier to a melt chamber and reacting it with a mineral containing lime, for example: calcium oxide, calcium hydroxide or calcium carbonate, to form a homogeneous cement product. This cement product is then transferred to a quench chamber where it is allowed to cool and solidify in the form of clinkers, which are later reduced to powder form. This process also provides an efficient means to conserve energy when producing a portland cement and provides an effective and economical way to dispose of a waste product while increasing the cost efficiency of a slagging coal gasifier.

Characterization and reuse of ash pond effluents in coal-fired power plants

Abstract: TVA has been characterizing wastewaters from coal-fired power plants since 1968. Information on ash pond effluents and schemes for reusing ash sluice water and other waste streams within power plants is provided. The main factors that affect the characteristics of TVA's ash pond discharges are the coal source, the firing method, the quantity and quality of water used for sluicing, efficiency of flyash collection methods, and performance of settling ponds. Four of 12 schemes for reuse of ash pond effluents are detailed. (7 diagrams, 6 graphs, 16 references, 4 tables)

Distribution of trace metals during oil shale retorting

Abstract: Three samples of raw oil shale from the Green River formation of western Colorado were retorted under conditions simulating the Tosco II process, a potentially commercial process. The raw shales and all resulting retort products were analyzed for various trace metals in an attempt to ascertain migratory patterns and resulting distributions through the retort so that effective environmental control measures could be implemented if necessary. Some evidence of low-level fluoride, boron, and copper partitioning to the water fraction was found. Similar behavior of arsenic and zinc partitioning to the shale oil product was observed with the ramainder of the metals investigated predominantly retained in the spent fly ash. 20 references, tables.

Application of X-ray Photoelectron Spectroscopy to the Study of Fly Ash

Abstract: X-ray photoelectron spectroscopy has been used to identify and determine the oxidation states of a number of major and minor elements present on the surface of fly ash particles. With the use of a sputtering-etching procedure, relative concentrations as a function of depth were obtained for Si, Al, Fe, Ca, Na, C, O, and S. The concentrations of Na, C, O, and S were found to decrease and Si, Al, and Fe were found to increase upon sputtering to a depth of approximately 50 A.

Utilising fly ash and calcium sulphate obtd. from flue gas - of coal burning furnace desulphurisation units, by heating aq. suspension to form anhydrite, and casting into bricks, etc.

Abstract: A process is claimed for utilising fly ash and calcium sulphate obtd. during desulphurisation of flue gases from coal-fired burners using lime. In the desulphurisation unit, the fly ash and oxides of sulphur are washed out to give an aq. slurry of calcium sulphate and fly ash. The calcium sulphate in the slurry is subjected to thermal treatment to convert it into gypsum with an alpha- and/or beta-anhydrite structure and/or the hemihydrate, and the resulting suspension of fly ash and anhydrite and/or hemihydrate is cast into moulds and allowed to set into bricks or building panels. Process allows prodn. of useful prods. from power station by-prods. The prods. have a fine uniform structure, a compressive strength of >50 kp/cm2 and specific gravity of 0.9-1.6 g/cm3.

Metal recovery and environmental protection by bacterial leaching of inorganic waste materials

Abstract: Industrial waste materials contain valuable metals in high total amounts but in low concentrations. Sulfidic dust concentrates and oxidic fly ash from a copper process, slag from a lead smelting process and “Jarosite” from a zinc electrolysis were leached with different thiobacillus species. The leaching efficiency was specific to materials, treatment and inoculated bacteria species. The maximum output for zinc was around 95%, for copper around 70%. We were concerned about the high concentrations of 32 mg Cd/l, 5 mg Pb/l and 30 mg As/l in the leaching liquors because these values exceed the allowed toxic levels in drinking water.

Chemistry and biological hazard of a coal ash seepage stream

Abstract: Despite careful control and monitoring of overflows from coal ash settling ponds, a significant potential exists for environmental impacts from uncontrolled seepage of rainwater and slurry water through ash deposits and containment dikes. This potential has been demonstrated through an analysis of seepages, now controlled, from the Tennessee Valley Authority's Bull Run Steam Plant on the Clinch River near Oak Ridge, Tenn. Acidic, iron-rich seepage water is produced within the ash deposits through physical and microbiological (presumably) processes. These seepage conditions also may mobilize other contaminants. An iron floc, which results when the acidic seepage enters the slightly alkaline river water, is detrimental to fish and bottom organisms in the vicinity. The particular flow problem addressed in this report may not occur at all coal-fired power plants with ash-settling ponds. However, the case for careful design and proper maintenance for disposal of this solid waste has been demonstrated.