Showing papers on "Fly ash published in 1990"
TL;DR: In this article, the removal of Omega Chrome Red ME (a popular chrome dye) from its aqueous solutions by adsorption on a homogeneous mixture of fly ash and coal in different proportions has been carried out.
334 citations
TL;DR: In this article, the ability of fly ash to remove fluoride from water and wastewaters has been studied at different concentrations, times, temperatures and pH of the solution, and the rate constants of adsorption, intraparticle transport, mass transfer coefficients and thermodynamic parameters have been calculated at 30, 40, and 50 °C.
Abstract: The ability of fly ash to remove fluoride from water and wastewaters has been studied at different concentrations, times, temperatures and pH of the solution. The rate constants of adsorption, intraparticle transport, mass transfer coefficients and thermodynamic parameters have been calculated at 30, 40, and 50 °C. The empirical model has been tested at various concentration for the present system. The removal of fluoride is favorable at low concentration, high temperature and acidic pH.
192 citations
TL;DR: In this article, the authors present data on the durability of a new type of concrete incorporating high volumes of low-calcium (ASTM Class F) fly ash, which has excellent durability with regard to frost action, has low permeability to chloride ions and shows no adverse expansion when highly reactive aggregates are incorporated into the concrete.
Abstract: Research on structural concrete incorporating high volumes of low-calcium (ASTM Class F) fly ash has been in progress at CANMET since 1985. In this type of concrete, the cement content is kept at about 150 kg/m3. The water-to-cementitious materials ratio is of the order of 0·30, and fly ash varies from 54 to 58% of the total cementitious material. A large dosage of a superplasticizer is used to achieve high workability.
This paper presents data on the durability of this new type of concrete. The durability aspects considered are: freezing and thawing cycling; resistance to chloride ion permeability; and the expansion of concrete specimens when highly reactive aggregates are used in the concrete.
The investigations performed at CANMET indicate that concrete incorporating high volumes of low-calcium fly ash has excellent durability with regard to frost action, has very low permeability to chloride ions and shows no adverse expansion when highly reactive aggregates are incorporated into the concrete.
164 citations
TL;DR: In this paper, the feasibility of using shell and fiber ash as a construction material was studied and the experimental results indicated that no significant effects of ash addition on the segregation, shrinkage, water absorption, density, and soundness of cement.
Abstract: The palm‐oil industry produces large amounts of solid wastes. Shell and fiber wastes are used extensively as fuel for steam production in palm‐oil mills. After combustion, a large quantity of ash is produced and creates problems of disposal. The feasibility of using the shell and fiber ash as a construction material is studied. The material differs from PFA from coal‐fired power plants in that it has a higher content of residual organic, a higher alkali content, is coarser. The experimental results indicate that no significant effects of ash addition on the segregation, shrinkage, water absorption, density, and soundness of cement. The workability of concrete blended with the shell and fiber ash is good, and setting times are well within the requirements of both American and British standards. The shell and fiber ash is only weakly pozzolanic, the decrease in compressive strength of concrete is almost proportional to the amount of ash in the blended cement, except when only 10% ash is used. The results sh...
151 citations
TL;DR: In this article, the influence of various combination levels of alkaline (pH 12.2) powerplant fly ash and sewage sludge on soil microbial activity and numbers was evaluated.
Abstract: Incubation studies were conducted to assess the influence of various combination levels of alkaline (pH 12.2) powerplant fly ash and sewage sludge on soil microbial activity and numbers. A Glynwood (fine, illitic, mesic. Aquic Hapludalf) silt loam soil was mixed with 0, 5, 10, or 20% (w/w) ash and 0 or 5% composted sewage sludge. Respiration was strongly depressed in the 10 and 20% ash treatments over 28 d. Sludge addition improved respiration in all ash treatments except the 20% treatment. Total bacterial, actinomycete, and fungal counts in the soil typically decreased with increasing ash content. Counts were depressed by 57, 80, and 86%, respectively, at the 20% ash application rate. Sludge application increased microbial numbers but all populations were lower at the highest ash rates compared to the untreated control. Soil phosphatase, sulfatase, dehydrogenase, and invertase were inhibited as ash treatment levels increased. Catalase activity was not significantly affected by ash concentration. Addition of the sludge to the ash-soil mixtures generally enhanced enzyme activity. The results indicate that high rates of fly ash to soils may hinder normal decomposition and nutrient cycling processes. This may be partially alleviated, however, by coapplication of a readily oxidizable organic substrate such as sewage sludge.
142 citations
TL;DR: In this article, the catalytic effects of copper and iron compounds were examined for their behavior in promoting formation of chlorine (Cl2), the major chlorinating agent of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorined dibenzofurans (PCDFs), in an environment simulating that of municipal waste fly ash.
135 citations
TL;DR: This article used an equilibrium speciation/solubility code to test the hypothesis that the solubilities of at least some species in the fly ash leachate were controlled by solid phases.
Abstract: Samples of pore fluids and leachates were obtained from a large fly ash field lysimeter in central Pennsylvania. The samples were analyzed for major and trace inorganic anions and cations. The resulting analyses were modeled by using an equilibrium speciation/solubility code to test the hypothesis that the solubilities of at least some species in the fly ash leachate were controlled by solid phases
133 citations
TL;DR: In this article, compressive strength tests of slag mortars indicate that alkali-activated ground granulated blast-furnace slag has potential as a replacement for portland cement in concrete.
131 citations
TL;DR: An alternative use for coal ash was investigated, based on the metakaolin type material present in the ash as discussed by the authors, which was treated with sodium hydroxide at different concentrations and various times and temperatures of crystallization.
125 citations
TL;DR: In this article, the physical and chemical properties of high-volume fly ash and Portland cement binders have been characterized up to 365 days of curing by X-ray diffraction and thermal analysis, and porefluid composition by high pressure extraction and analysis.
Abstract: This paper describes investigations of high-volume fly ash (HVFA)-Portland cement (PC) binders, the physical and chemical properties of which have been characterized up to 365 days of curing Physical investigations were made of compressive strength development, pore structure by porosimetry, and morphology by scanning electron microscopy Chemical examination was conducted for solid phase composition and degree of hydration by X-ray diffraction and thermal analysis, and for pore-fluid composition by high pressure extraction and analysis Up to 365d the cement in the HVFA pastes is not fully hydrated However, the ash participates in both early (sulpho-pozzolanic) and late (alumino-silicate) hydration reactions In addition to the usual products of cement hydration, ettringite (AFt) has been identified as a product of the early hydration of the fly ash It has not been possible to identify long term hydration products of fly ash which appear to be non-crystalline A two-step mechanism for pozzolanic reaction between fly ash and Portland cement has been proposed involving: (a) depolymerization/silanolation of the glassy constituents of the ash by the highly alkaline pore fluids, followed by (b) reaction between solubilized silicate and calcium ions in solution to form CSH
120 citations
TL;DR: In this paper, a high-volume fly ash concrete for structural applications was developed at CANMET, where the fly ash-cememt reaction occurred relatively early at 3 to 7 days and was concluded that the cement matrix and residual unreacted fly ash form a good mechanical bond.
Abstract: High-volume fly ash concrete for structural applications was developed at CANMET. In this concrete fly ash to ‘total cementitious material’ was maintained over 55%. The purpose of this work was to investigate, by the use of similar paste mixtures of the same fly ash and cement, the mechanism by which the mechanical properties were developed. Mechanical property-porosity relations, pore size distribution, permeability, degree of hydration and Ca(OH)2 content measurements were made. It was observed that the fly ash-cememt reaction occurred relatively early at 3 to 7 days and it was concluded that the cement matrix and residual unreacted fly ash form a good mechanical bond.
TL;DR: X-ray analysis shows that mullite and silica are the major crystalline phases in fly ash and the weight fractions of these phases are 14.2 and 5.1 wt%, respectively as discussed by the authors.
Abstract: X-ray analysis shows that mullite and silica are the major crystalline phases in fly ash. The “method of known additions” from X-ray diffraction techniques was used to calculate changes in the significant peak intensities of mullite and silica to determine their weight fractions in fly ash. This furthers the efforts of characterizing fly ash, which are being conducted to supplement the search for applications of this abundant material. The weight fractions of crystalline mullite and silica were determined to be 14.2 and 5.1 wt%, respectively. Thermal gravimetric studies as well as SEM and particle size analysis were also conducted on the fly ash.
TL;DR: In this paper, the physical and chemical properties of these ashes are presented, and their suitability for various purposes are assessed, including information on leachate generation and how inorganic species interact and are transported in porous media.
Abstract: Combustion processes for power generation or waste volume reduction result in the generation of mostly inorganic ash residues. Recycling or reuse of these materials is sometimes possible; however, presently, the major portion must be disposed of in an environmentally acceptable way. In this review, the physical and chemical properties of these ashes are presented, and their suitability for various purposes are assessed. Included is information on leachate generation and how inorganic species interact and are transported in porous media. In view of these principles, appropriate environmental control strategies are presented and discussed.
TL;DR: In this paper, various combinations of Type I portland cement (OPC), Type F fly-ash, blast furnace slag, lime, and silica fume have been used to treat the contaminated soils, which are then leached using a slightly modified EP Tox1 leaching procedure.
TL;DR: In this paper, the results of large-scale lysimeter tests in which two pulverized coal fly ashes (PCFA) have been exposed to natural weather conditions for up to seven years are presented and compared with those of laboratory leaching tests.
TL;DR: Coal fly ash was applied at rates of 0, 3, 6 and 12% to a sandy soil and a sandy loam to evaluate its effect on yields of two vegetable crops, Brassica parachinensis and B. chinensis.
TL;DR: Co-application of 5% composted sewage sludge to the ash-soil mixtures improved respiration in both soils except for the 20% alkaline ash rate, and high pH appeared associated with decrease in respiration.
Patent•
24 May 1990TL;DR: In this article, a fly ash byproduct is obtained by gravitationally separating and collecting a first material fraction of the fly ash having a density less than the liquid by skimming off floating slurry material.
Abstract: A wet process for the beneficiation of a fly ash by-product has the following steps: a) forming a slurry mixture of a fly ash material and a liquid; b) gravitationally separating and collecting a first material fraction of the fly ash having a density less than the liquid by skimming off floating slurry material; c) separating a first magnetic fraction from the slurry by subjecting the slurry to a magnetic field of from about 300 gauss to about 10 kilogauss; d) separating the unburned carbon from the remaining slurry components by adding an effective amount of an oil having a carbon chain greater than octane, and a frothing agent whereby the oil coats the unburned carbon forming hydrophobic carbon materials and inducing air into the system for frothing the slurry mixture wherein the hydrophobic unburned carbon froths to the surface and is removed by skimming off the frothing layer; and e) collecting the remaining fraction of silicate spheres and silicates.
TL;DR: Inverse addition experiments were used to show that a surface-bound chlorinating agent is produced by the interaction of hydrogen chloride with the fly ash surface as mentioned in this paper, indicating that an electrophilic mechanism is likely for the chlorination reaction.
Abstract: Aromatic substrates were adsorbed on the surface of fly ash from a municipal incinerator. Treatment with gaseous hydrogen chloride gave aromatic chlorination. Relative yields and isomer distributions indicate that an electrophilic mechanism is likely for the chlorination reaction. Inverse addition experiments were used to show that a surface-bound chlorinating agent is produced by the interaction of hydrogen chloride with the fly ash surface. Recycling experiments indicate that the fly ash surface functions as a stoichiometric oxidant, and not a catalyst, in promoting aromatic chlorination by HCl. The yields of aromatic chlorination on three different fly ash samples were found to be quite different. A variety of physical and chemical characterizations revealed no simple relationship between properties and yields. It was noted that the reaction of hydrogen chloride with the fly ash surface led to release of metal ions from the surface upon solvent extraction. It was found that the release of iron from the surface corresponded to the changing yields noted.
Patent•
27 Feb 1990
TL;DR: In this article, a process and apparatus for the vitrification of fly ash produced from an incineration system for solid waste materials, including the combining of the fly ash extracted from the pollution control device in the incineration process with fusible material, particularly glass, was described.
Abstract: A process and apparatus for the vitrification of fly ash produced from an incineration system for solid waste materials, including the combining of fly ash extracted from the pollution control device in the incineration system with fusible material, particularly glass, and preferably recycled glass extracted from the solid waste material before it is incinerated, and subsequently melting the combined glass and fly ash in a vitrification furnace in order to vitrify the fly ash and its toxic contaminants, including lead, mercury, cadmium and other heavy metals, to produce an inert vitrified ash product. The flue gas from the vitrification furnace is returned to the flue gas stream from the incinerator for introduction into the pollution control device.
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TL;DR: In this paper, the compressive strength of coal fly ashes and their activity in the sintering process measured by means of viscosity and surface tension were investigated. But the results showed that the strength of sintered pellets produced from crystallized Beulah lignite ash is weaker than those produced from the amorphous form of the ash.
TL;DR: In this paper, the effect of high-lime (Class C) fly ash on water demand, workability, time of set, and compressive strength of concrete was investigated on nominal 3000, 4000, and 5000 psi structure grade concrete utilizing fly ash produced at Wisconsin Electric Power Company's Pleasant Prairie Power Plant.
Abstract: The paper presents research performed to report the effect of high-lime (Class C) fly ash on water demand, workability, time of set, and compressive strength of concrete. Tests were carried out on nominal 3000, 4000, and 5000 psi structure grade concrete utilizing fly ash produced at Wisconsin Electric Power Company's Pleasant Prairie Power Plant. Fly ash replacement improved workability, decreased water demand, and increased strength. The initial and final set times were not significantly different when fly ash replacement for cement was increased up to levels of 5 %.
TL;DR: In this paper, the authors present long-term data on the initial work carried out on high-volume fly ash concrete at CANMET laboratories, which reached a maximum compressive strength of 70 MPa at 1 1 2 years.
Abstract: This paper presents long-term data on the initial work carried out on high-volume fly ash concrete at CANMET laboratories. In the laboratory investigations, a concrete block measuring 1·5 m × 1·5 m × 1·5 m was cast indoors under controlled temperature conditions. The concrete contained 147 kg/m 3 of ASTM Type II cement and 187 kg/m 3 of ASTM Class F fly ash. The density of the concrete was high, of the order of 2500 kg/m 3 . The strength development of the concrete has been monitored over a period of 3 1 2 years, and it reached a maximum compressive strength of 70 MPa at 1 1 2 years. The modulus of elasticity of this concrete at 2 years was 47 GPa. The penetration of chloride ions in this concrete, when measured according to AASHTO T277-831, was 53 coulombs at 3 1 2 years. Following its excellent performance in the laboratory investigations, this concrete was utilized in a field application, a brief description of which is also presented.
TL;DR: In this article, an investigation on the pozzolanic reactivity of some lightweight aggregates based on expanded clay and sintered fly ash was carried out, but the effect was not very pronounced.
TL;DR: In this paper, the compressive strength and durability of concretes containing substitute materials at a 50% replacement level (by mass) of Portland cement was investigated, and the results showed that the substitute material was more robust than the original concrete.
Abstract: Results are presented from an investigation on the compressive strength and durability of concretes containing substitute materials at a 50% replacement level (by mass) of Portland cement. Seven fl...
TL;DR: In this article, the major depositional problems experienced by utilities and several approaches used to understand the mechanism of coal ash deposit formation are described. And a classification and sampling system for ash deposits is described and the analytical work used to characterize them is referenced.
TL;DR: The 3R Process as mentioned in this paper recovers fly ash and HCl from the flue gases; removes heavy metals from the fly ash by extraction with HCl; and returns a pelletized fly ash to the incinerator.
Patent•
03 Apr 1990TL;DR: In this article, a method for controlling emissions of a fossil fuel fired boiler including a high temperature fabric filter house with an SCR catalyst situated therein for receiving flue gases along with an injected ammoniacal compound and sorbent.
Abstract: A method for controlling emissions of a fossil fuel fired boiler including a high temperature fabric filter house with an SCR catalyst situated therein for receiving flue gases along with an injected ammoniacal compound and sorbent. The sorbent reacts with the SO x while the ammoniacal compound reduces the NO x in the presence of the SCR catalyst inside the high temperature fabric filter house. Both the SO x and the particulates are removed upstream of the SCR catalyst to diminish the problems of SO 2 or SO 3 poisoning of the catalyst and erosion and fouling of the catalyst with the fly ash. Since the sulfur oxides and particulates are removed prior to the heat recovery system, the fouling and corrosion potential are substantially decreased thus allowing the heat recovery system to be operated at a lower outlet flue gas temperature which yields an incremental improvement in energy recovery.