Showing papers on "Fly ash published in 1977"

Physical properties of fly ash-amended soils

Abstract: Fly ash from a coal-fired power generating plant was mixed with five California soils at rates of 0, 2.5, 5.0, 10.0, 25.0, and 50.0% by volume. The physical properties related to the agronomic use of fly ash-amended soils were characterized by determining water-holding capacity, bulk density, hydraulic conductivity, and modulus of rupture on laboratory compacted soil cores. The moisture release characteristics of each mixture were also determined. Results indicated that a small amount of fly ash added to soils does appear to affect some measured physical properties of soils. At application rates >25%, there was a consistent increase in water-holding capacity (except a Domino loam soil), and a decrease in bulk density and modulus of rupture in all soils tested. The hydraulic conductivity increased with small amounts of fly ash, but declined rapidly as fly ash volume increased. Although fly ash application increased the water-holding capacity of soils, the amount of water available to the plant did not change significantly. At a low applicant rate, fly ash amendment appaared useful in improving certain agronomic properties of soils.

Sorptive behavior of trace metals on fly ash in aqueous systems

Abstract: Eleven different fly ashes from coal-fired power plants were subjected to various chemical extractions and washings for determination of their acid-base and heavy metal chemistry. Results suggested that the relative amounts of lime and amorphous iron oxides on the surface define the ultimate acidic or basic character of fly ash in solution. In spite of wide variations in heavy metal content, most metals displayed an association with a specific surface oxide of either iron, manganese, or aluminum. Desorption of metals in aqueous solution followed a predictable pattern of decreasing release with increasing pH. Arsenic was an exception to this at high pH. Mercury behaved anomalously due to the presence of the elemental form. Ranges in reported values are attributed primarily to the variable geochemical matrix in which the heavy metals are found before mining.

Comparison of levels of trace elements extracted from fly ash and levels found in effluent waters from a coal-fired power plant

Abstract: Trace elements were extracted from a coal-fired power plant electrostatic precipitator ash with nitric acid, hydrochloric acid, citric acid, redistilled water, and ammonium hydroxide as extractants. Effluent waters at this plant were sampled to assess the elevation of trace element concentrations compared with intake waters. The results showed a positive correlation between those elements most extractable by water (B, F, Mo, and Se) or acid (As, B, Cd, F, Mo, and Se) and those elements most elevated in effluent waters (As, B, F, Mo, and Se).

National survey of elements and radioactivity in fly ashes. Absorption of elements by cabbage grown in fly ash-soil mixtures

Abstract: An analytical survey of 45 elements was conducted in fly ashes from 21 states in the US, using several instrumental methods. A high degree of correlation was found between the concentrations of pairs of chemically similar elements in the fly ashes and between the magnitude of gamma emission of the fly ashes and their respective concentrations o th or U. Cabbage was grown to maturity in potted soil amended with 7% w/w of the various fly ashes. The concentrations of As, B, Mo, Se and Sr in the cabbage showed a high degree of correlation with those in the fly ashes in which the plants were cultured.

Toxic metals in surface waters from coal ash

Abstract: The concentrations of 10 (titanium (Ti), manganese (Mn), copper (Cu), chromium (CR), zinc (Zn), arsenic (As), selenium (Se), cobalt (Co), cadmium (Cd), and mercury (Hg)) toxic elements were measured in the water, benthic sediment, plants, invertebrates, and vertebrates of an ash basin and its drainage system at a coal-fired power plant of the Savannah River Project, Aiken, S.C., over a period of two years. During 12 months of this period the basin was essentially filled and little settling of ash occurred. In the remaining 12 months, dredging had been completed, adequate settling occurred and most of the effluent turbidity was removed. All elements were more concentrated in sediment and biota than in water, and five (Mn, Cu, As, Zn, and Se) were biomagnified by at least one biotic component as compared to concentration in benthic sediment. Plants had high accumulations of Ti, Mn, As, and Hg: invertebrates had high accumulations of Co, Hg, Cu, Cr, Cd, and As; and vertebrates greatly biomagnified Se and Zn. The streamlined biotic community of the system accomplished major removal of Mn, Zn, As, Se, and Cd from the effluent. The magnitude of bioaccumulation of Ti, Mn, Zn, As, Se, Cd, and Hg was increasedmore » during the period of adequate settling in the basin.« less

Soybean growth on fly ashamended strip mine spoils

Abstract: The use of fly ash as an amendment for strip mine soils has been studied under field conditions. Spoils ranging in pH from 4.0–6.0 were tested. The addition of fly ash in all cases was effective as an acid soil neutralizer and substantially enhanced the growth and development of all experimental plants. The parameters used in growth analyses were plant height, dry weight, root/shoot ratios, nodulation, pod production, and nitrogen fixing capacity for legumes. re]19761004

Electrostatic precipitation of fly ash

Abstract: The main elements and features of precipitator equipment used for the collection of fly ash are presented. The major types of problems encountered in the application of precipitators to the collection of fly ash are enumerated and approaches for solving and avoiding these problems indicated. A summary of the fundamental problems, mechanical problems and operational problems commonly met with in practice is presented. The vital importance of relying on scientific and systematic methods for diagnosing and correcting the varied problems which may arise is emphasized. Several case histories of fly ash precipitators are given to illustrate the principles, methods, and practices covered in the preceding sections of the paper. Performance specifications, design and actual performance data are presented for medium sulfur eastern coal, high sulfur midwestern coal and low sulfur Rocky Mountain coal. In each case the information and data used are based on first-hand knowledge and close association of the author with the installation. Previous installments of the paper appeared in the January, February and March issue of JAPCA.

Revegetation of alumina refinery wastes. 1. Properties and amelioration of the materials

Abstract: Excess soluble salts (EC 30 to 48 mScm-1), high alkalinity (pH 92 to 11 0) and potentially toxic levels of sodium (ESP 49 to 88 per cent) were characteristic of fly ash and bauxite wastes ('red sand' and 'red mud') from the Gladstone alumina refinery In red sand, N and P levels were extremely low and Zn and Mn marginal; extremely low levels of N and P and a marginal amount of Zn were measured in the red mud Fly ash was characterized by a potentially toxic level of B and deficiency levels of N and Zn The physical limitations of low water holding capacity of red sand and the susceptibility of fly ash to wind erosion were reduced by mixing the wastes Excess soluble salts in fly ash-red sand mixtures were effectively removed by leaching without an accompanying decrease in the saturated hydraulic conductivities of the solids Following the reduction in salinity, the pH values of the wastes remained high (84 to 96) Incubation of the ash and sand with NH4NO3, superphosphate, FeSO47H2O, FeS2 and S for up to ten weeks demonstrated that FeSO47H20 was the most effective acidulant in the short term Reduction of the excessive exchangeable sodium percentages in ash (49 per cent) and sand (88 per cent) to levels tolerable to plant growth was achieved by leaching and acidification

Instrumental activation analysis of coal and fly ash with thermal and epithermal neutrons

Abstract: A systematic comparison of thermal and epithermal irradiations in the instrumental activation analysis of coal and fly ash was made. From a total of 44 elements, the epithermal irradiation technique appeared advantageous in 20 cases, namely Ni, Ga, As, Se, Br, Rb, Sr, Zr, Mo, In, Sb, Cs, Ba, Sm, Ho, Hf, Ta, W, Th and U. Data are presented for the National Bureau of Standards’ coal (SRM 1632) and fly ash (SRM 1633).

Determination of forty elements in geochemical samples and coal fly ash by x-ray fluorescence spectrometry

Abstract: A method for the determination of 40 elements in geochemical samples and coal fly ash is described. Pulverized samples are mixed with sulfur powder and specimens are prepared in the form of pressed disks. In addition to acting as a binder, the sulfur matrix dominates the absorption properties of the specimen disks. Thus, matrix absorption corrections can be determined for a single specimen and applied to the analysis of a wide class of samples. Standardization is achieved using nebulized multielement solution deposits, as well as two single element vacuum vapor deposited thin-film standards. Utilizing two 25-min analysis periods, results achieved are typically accurate to within +- 5% when x-ray counting statistics are not the limiting factor.

Fractionator for size classification of aerosolized solid particulate matter

Abstract: A system is developed for collecting kilogram quantities of size-fractionated particulate matter which can be subsequently used for biologic testing purposes. The apparatus consists of a series of two cyclones and a centripeter and yields four size fractions. When used over a 12-day period to classify fly ash from stack gas passed through the electrostatic precipitator of a coal-fired power plant, the collected fractions have volume median diameters of 20, 6.3, 3.2, and 2.2 ..mu..m with geometric standard deviations of approximately 1.8. A total of 8.08 kg of fly ash is collected.

Process for recovering mineral values from fly ash

Abstract: A process for recovering mineral values from fly ash in commercial quantities comprising forming an alkaline aqueous fly ash blend, filtering the alkaline aqueous fly ash blend and recovering a solids blend therefrom, leaching the solids blend with hydrochloric or hydrofluoric acid to form dissolved chloride or fluoride salts of iron, aluminum and other metals, electrolyzing the dissolved chloride or fluoride salt solution to plate out at least iron, and, optionally, one or more other metals, recovering silicon dioxide as a precipitate from the leaching solution, and recovering the leaching solution free of silicon dioxide. Neutralizing the leaching solution in a certain pH range permits precipitation and recovery of aluminum hydroxide as a solid. The hydroxide may then be converted to alum or alumina by conventional methods.

Slag/fly ash cements

Abstract: Investigations have been carried out of cements made from a combination of finely ground blastfurnace slag or synthetic granulate with untreated fly ash using sodium hydroxide solution as activator. Using a combination of 60% slag and 40% fly ash with 7% naoh (relative to combined weight of slag and ash) as activator, concrete has been prepared and tested for compressive strength up to an age of one year. Early strength properties were good but there was little gain in strength beyond 28 days though improved strength might be obtained by varying the proportions of slag and ash or by increasing the fineness of the slag. Whatever cements' of this type have to offer in the way of useful properties is unlikely to be outweighed by the difficulties of handling a strongly alkaline material on site, the risk of alkaline-aggregate reaction and the possibility of efflorescence. /Author/TRRL/

Melting behavior of coal ash materials from coal ash composition

Abstract: The ionic potential (valence divided by ionic radius) may be used as a measure of acids and bases in predicting coal ash melting and viscosity from the chemical composition The role of an acid is that of a complex ion former with anions provided by bases which in coal ash systems are oxide ion donors In systems containing acids and limited oxide ion concentrations, polymers tend to form in the melts Addition of bases reduces polymer size and would decrease viscosity The gaseous environment may alter the relative concentration of ferric and ferrous ions, interconverting acid and base ions In general, bases are reported to be equally effective oxide ion donors The effects of base addition are proportional to the amount of oxide ion provided to the system

Stabilization of earth subsurface layers

Abstract: A method of treating subsurface layers of the earth to either control movement of the subsurface water or build strength of the subsurface layers, or both, characterized by injecting at a predetermined depth and at a plurality of predetermined, spaced apart locations a limefly ash slurry consisting essentially of water, particulate hydrated lime, particulate fly ash and a surfactant. Also disclosed are the preferred proportions, or concentrations, of the components of the slurry; and a finished product; such as, a railroad track subgrade and ballast supporting cross-ties and rails, the subgrade having been injected with masses of lime and fly ash slurry to leave residual masses of lime and fly ash disposed in fissures and any ballast pockets along the railroad track, the masses having a proportion of lime to fly ash in the range of one to 1:1 to 1:3.

Revegetation of alumina refinery wastes. 2. Glasshouse experiments

Abstract: In the absence of chemical limitations, the emergence and yield of Rhodes grass (Chloris gayana) on a 20 per cent fly ash : 80 per cent red sand mix were higher than those on fly ash or red sand alone or on the other mixes investigated. The poor emergence and yield in the red sand was attributed to the medium's low available water capacity and low unsaturated hydraulic conductivity. Mixtures containing from 40 per cent to 100 per cent fly ash were characterized by very low air contents at field capacity and were susceptible to water-logging. The extremely poor emergence and low yields observed in the mixtures containing 40 per cent and 60 per cent fly ash were considered to be due to high mechanical resistance to root ramification in addition to lack of aeration. In the absence of the limitations of excess salinity, alkalinity and sodicity, deficiencies of nitrogen and phosphorus were the major restrictions to the growth of Rhodes grass on fly ash, red sand and a 20 per cent fly ash : 80 per cent red sand mix. Manganese was also limiting in red sand, and boron was slightly deficient in fly ash, but these deficiencies were not present in the ash : sand mix. In a nitrogen (NH4NO3) by phosphorus (Ca(H2PO4)2.H2O) interaction trial on fly ash and red sand, maximum yields of Rhodes grass were obtained with 100 kg N ha-1 (red sand) to 200 kg N ha-1 (fly ash) and 400 kg P ha-1. The severe yield depression which occurred at nitrogen rates greater than 200 kg ha-1 on both wastes was attributed to NH4+ toxicity aggravated by the dearth of nitrifying bacteria and the wastes' low cation exchange capacities.

Using simultaneous three colour X-ray mapping and digital-scan-stop for rapid elemental characterization of coal combustion by-products

Abstract: A system is described for rapid, simultaneous three colour elemental mapping with a scanning electron microscope (SEM) and an energy dispersive X-ray analyser. The technique, which use a SEM scanning at TV rate, minimizes the disadvantages of long scan times such as inefficient use of linear amplifer and observable dead-time shadowing. The system also employs a digital scan-stop assembly utilizing a light pen to rapidly and reproducibly direct the beam to an object of choice for spot-mode analysis. Application of the system to analysis of fine particulates with emphasis on fly ash derived from coal-fired electric power plants is discussed. Chemical heterogeneity of fine particles in standard reference material fly ash and in phagocytized fly ash within pulmonary macrophages is demonstrated. This system combines the morphologic capability of the SEM with X-ray multielement mapping to provide a needed tool for particulate source identification.

Process for removing sulfur dioxide in a wet scrubber

Abstract: The method for removing oxides of sulfur from a waste gas stream in a wet scrubber using a controlled amount of a fly ash solution as one of the sulfur dioxide reacting materials.

Regeneration of lime from sulfates for fluidized-bed combustion

Abstract: In a fluidized-bed combustor the evolving sulfur oxides are reacted with CaO to form calcium sulfate which is then decomposed in the presence of carbonaceous material, such as the fly ash recovered from the combustion, at temperatures of about 900° to 1000° C., to regenerate lime. The regenerated lime is then recycled to the fluidized bed combustor to further react with the evolving sulfur oxides. The lime regenerated in this manner is quite effective in removing the sulfur oxides.

Gasification of solid fuels - with combustion of the ash in oxygen and recycling of the hot gas produced

Abstract: Gasification of carbonaceous fuels with air and/or O2, steam and CO2 in a fluidised bed generator, in which ash contg. unburnt carbon, taken from the product gas and from the generator, is burnt in a fluidised bed of ash at below the m.pt. of the ash. The combustion gas contg. mostly CO2 is recycled to the generator as a addnl. gasifying agent and heat carrier. Efficiency is improved by almost complete use of the unburnt carbon, and disposal of the ash simplified. Maintenance of the ash bed at below its m.pt. reduces demands made on the construction material, and avoids molten droplets of slag which deposit in the equipment. Unpurified water, e.g. condensate, from the process can be sprayed into the ash during combustion to produce superheated steam for use in the generator.

Animal litter composition

Abstract: Fly ash, bottom ash and/or boiler slag are used as animal litters and particularly as cat litters. These materials exhibit remarkable absorbent and deodorizing capabilities and their low cost makes them a commercially more attractive substitute for Fuller's earth and other currently available cat litter compositions. These materials are also effective when used in admixture with Fuller's earth or other known cat litters.

Leachability of neutron irradiated fly ash

Abstract: Leachability of neutron irradiated fly ash is investigated as a method for studying element leaching properties of this material with various leaching media. Quantitative aspects of radiation damage are shown to be minor. Therefore, the technique should be applicable for this purpose. It is further shown that this technique affords significant advantages over the conventional post-leaching analysis with respect to utilization of natural solutions for the investigation of fly ash leachability. However, for a few elements such as Pb, Bi, V, and Al, the various nuclear parameters involved invalidate applicability of the present technique.

Determination of traces of arsenic in siliceous materials

Abstract: Finely ground rocks, slags, and fly-ash are completely converted to soluble form by HF-HNO/sub 3/ vapor phase attack at approximately 70/sup 0/C. The treatment chamber is a commercially available 1-L Teflon jar. Arsenic is not volatilized by this procedure if in the As(V) form. Arsenic contaminating the acid mixture is carried over to the sample if the arsenic is trivalent. Potassium permanganate, added to the acid mixture in advance, converts any As(III) present to As(V), thus preventing contamination of the sample. Accurate results were obtained with NBS Coal Fly Ash (SRM 1633) and standard rocks.

Fly Ash and Furnace Gas Characteristics

Abstract: The particle and gas properties that profoundly affect design and performance of fly ash precipitators are discussed and evaluated in this section. Relation of the coal burned to these properties and to the precipitator gas cleaning problem is broadly examined. The need for a high order of technology consistently applied to cope successfully with the wide and often uncertain variations in coal and ash properties encountered in precipitation practices is emphasized.

Performance of a Pulse-Jet Filter at High Filtration Velocity I. Particle Collection

Abstract: The fly ash collection characteristics of a pulse-jet fabric filter have been studied Fly ash penetration was found to decrease as the dust deposit increased from 0 to 60 micrometers in thickness, to increase as face velocity through the bags increased from 5 to 15 cm/s, and to remain relatively constant for particles from 03 to 40 µm in diameter Experiments employing chemically tagged fly ash were performed to investigate three dust penetration mechanisms On resumption of filtering after cleaning, penetration by straight through dust loss declined rapidly from its maximum, reached a minimum, and then increased Seepage of dust through the fabric was found to be constant throughout the filtration cycle Dust lost as pinhole plugs increased after cleaning, passed through a maximum, and then declined The pinholes appeared to open the way for further penetration by the straight through mechanism

Means for producing cementitious product from quenched fly ash

Abstract: A cementitious product is produced from a combination of two groups of materials: the first group consisting of lime or Portland cement or Linfan (which is defined as a thermally cracked shell of calcium sulfate surrounding a core of lime) or Linvein (a lime particle coated with cracked calcium carbonate); and a second material consisting of thermally cracked fly ash which is cracked by thermally quenching such finally divided particulate material from an elevated temperature at least above 300° C. and preferably higher than 450° C. to ambient or below ambient temperatures. The two materials are blended together. They are mixed with water, placed in a form, and then allowed to cure. Filler materials can also be used in the form of sand, gravel, and other aggregates, depending upon the strength and compositional characteristics desired in the final product.

Compositions of sulfur and fly ash and shaped articles produced therefrom

Abstract: Shaped articles are produced from compositions of sulfur and a particulate inorganic material, at least 10% by weight of the particulate inorganic material being fly ash. The initial compositions are uniform dry blends, and the finished products are formed by converting the sulfur of the composition to molten form and then cooling while, as in casting, the molten material is confined in the desired shape. Use of fly ash provides articles having a hardness more than twice that of sulfur alone and a compressive strength approaching three times that of a typical aged poured concrete.