Properties of several fly ash materials in relation to use as soil amendments

Fly ash samples from five power stations in Western Australia and Queensland, and two soils used for horticulture in Western Australia, were evaluated for a series of physical and chemical properties. Soils were comprised primarily of coarse sand-sized particles, whereas most of the fly ashes were primarily fine sand- and silt-sized particles. Hydraulic conductivities in the fly ashes were 105- to 248-fold slower than in the soils. The water-holding capacities of fly ashes at "field capacity" were three times higher than those of the soils. Extractable P in the fly ashes (except Tarong and Callide) were 20- to 88-fold higher than in the soils. The pH showed considerable variation among the different sources of fly ash, with samples from Muja being the most acidic (pH = 3.8; 1:5 in CaCl2 extract) and from Gladstone the most alkaline (pH = 9.9). The toxicity characteristic leaching procedure (TCLP) values indicate that the potential for release of trace elements from the fly ashes was well below regulatory levels. When applied at sufficient rates (e.g., to achieve 10% w/w in surface layers) to sandy soils, fly ash altered texture and increased water-holding capacity. Depending on the source of fly ash used, such amendments could also provide P and aid nutrient retention by increasing the phosphorus retention index (PRI) and/or cation exchange capacity (CEC). The considerable variability in physical and chemical properties among the fly ash samples evaluated in the present study supports the notion that field trials are essential to the future development of soil amendment strategies making use of any particular source of fly ash.     

废旧铝、铁片粉煤灰复合混凝剂的制备及在废水处理中的应用

我国粉煤灰和铝、铁片固体废物产量日益增多,危害越来越严重。在高温加热、搅拌条件下,用强酸浸渍粉煤灰和易拉罐碎片,使粉煤灰和废旧铝、铁片资源化,制得废旧铝、铁片粉煤灰复合混凝剂,并用所制得的废旧铝、铁片粉煤灰复合混凝剂处理屠宰废水。在一定条件下,经混凝试验处理后的屠宰废水pH值在7左右,COD去除率为92．0％,SS去除率为98．7％,浊度去除率为98．4％,色度去除率为96．6％。结果表明,粉煤灰和废旧铝、铁片资源化和在废水处理中的应用具有可行性。     

以造粒粉煤灰为过滤介质去除景观水中磷的研究

研究了造粒粉煤灰的最大磷吸附量、磷吸附速率等吸附特征，以及颗粒粒径、磷浓度、水力负荷对景观水除磷效果的影响。还进行了为期21天的连续过滤试验，发现滤床在高水力负荷条件下能持续地去除景观水中的磷。     

Soft subgrades’ stabilization by using various fly ashes

This publication presents the results of research involving different types of self-cementing fly ashes (without any other activators) for the stabilization of four different types of soft subgrades from various road sites in Wisconsin, USA. The strength approaches were applied to estimate the optimum mixture design and to determine the thickness of the stabilized layer. The stabilized soil samples were prepared by mixing fly ash at different contents at varying water contents. The performance of fly ash stabilized subbase depends both on the specific source of fly ash and the engineering properties of soils. It is suggested that the performance analysis of fly ash should be based upon the laboratory tests such as index properties, compaction, unconfined compressive strength and CBR tests of a specific site. This is suggested rather than using the study of the physical properties and chemical composition of fly ash and soil. As disclosed in the literature, the strength gain due to stabilization depends mainly upon three factors; ash content, molding water content and compaction delay. The samples were subjected to unconfined compression strength and California bearing ratio (CBR) tests after 7 days curing time to develop water content–strength relationship. To evaluate the impact of compaction delay that commonly occurs in the field during construction, the sets of samples were compacted 2 h later after mixing with water. The unconfined compression strength and CBR tests were performed and used to determine the thickness of the stabilized layer in pavement design. All of these factors were taken into account throughout this research.     

PHOSPHATE IN WATERS: II. PLANT AVAILABILITY OF LIGNITE FLY ASH EXTRACTED FORMS IN GREENHOUSE TRIALS1

ABSTRACT: Orthophosphate P was removed from municipal waste water, lake waters, and P-spiked solutions by contact with fly ash from lignite burning electric power generating plants. The recovered ash was increased in total P content 3-fold, and Bray No. 1 soluble P, 9-fold. Phosphorus enriched ash so prepared was used in greenhouse trials with sand or soil as the major substrate material. Recovery of added P by barley plants ranged from 3 to 26 percent in the sand cultures and from 2 to 17 percent for soil cultures. Phosphorus contained in normal ash was partially available to barley under the conditions of these experiments. High B and the pozzolanic effect induced by ash reduced plant growth significantly.     

Efficacy of alum and coal combustion by-products in stabilizing manure phosphorus

Animal manures contain large amounts of soluble phosphorus (P), which is prone to runoff losses when manure is surface-applied. Here we report the efficacy of alum and three coal combustion by-products in reducing P solubility when added to dairy, swine, or broiler litter manures in a laboratory incubation study. Compared with unamended controls, alum effectively reduced readily soluble P, determined in water extracts of moist manure samples with 1 h of shaking, for all three manures. The reduction ranged from 80 to 99% at treatment rates of 100 to 250 g alum kg(-1) manure dry matter. The fluidized bed combustion fly ash (FBC) reduced readily soluble P by 50 to 60% at a rate of 400 g kg(-1) for all three manures. Flue gas desulfurization by-product (FGD) reduced readily soluble P by nearly 80% when added to swine manure and broiler litter at 150 and 250 g kg(-1). Another by-product, anthracite refuse fly ash (ANT), was ineffective for all three manures. In all cases, reduction in readily soluble P is primarily associated with inorganic phosphorus (P(i)) with little change in organic phosphorus (P(o)). Sequential extraction results indicate that the by-product treatments shifted manure P from H2O-P into a less vulnerable fraction, NaHCO3 - P, while the alum treatment shifted the P into even more stable forms, mostly NaOH-P. Such shifts in P fractions would have little influence on P availability for crops over the long-term but would retard and reduce potential losses of P following manure applications.     

Leaching characteristics of solid wastes from thermal power plants of western Turkey and comparison of toxicity methodologies

Use of lignite in power generation has led to increasing environmental problems associated not only with gaseous emissions, but also with the disposal of ash residues. In particular, use of low quality coals with high ash content results in huge quantities of both fly and bottom ashes to be disposed of. A main problem related to coal ash disposal is the heavy metal content of the residue. In this regard, experimental results of numerous studies indicate that toxic trace metals may leach when fly and bottom ashes are in contact with water. In this study, fly and bottom ash samples obtained from thermal power plants, namely Yenikoy, Kemerkoy and Yatagan, located at the southwestern coast of Turkey, were subjected to toxicity tests such as the extraction (EP) and toxicity characteristic leaching (TCLP) procedures of the US Environmental Protection Agency (USEPA) and the so-called 'Method A' extraction procedure of the American Society of Testing and Material (ASTM). The geochemical composition of ash samples showed variations depending on the coal burned in the plants. Furthermore, the EP, TCLP and ASTM toxicity tests showed variations such that the ash samples were classified as 'toxic waste' based on EP and TCLP results whereas they were classified as 'non-toxic' based on ASTM results, indicating test results are pH dependent. When the extraction results were compared with the chemical composition of water samples obtained in the vicinity of the thermal power plants, it was found that the results obtained using the ASTM procedure cannot be used to predict subsurface contamination whereas the EP and TCLP procedures can be used.     

改性粉煤灰处理制革废水试验研究

本试验利用硫酸溶液对粉煤灰进行踟陛，研究了改性粉煤灰对制革废水的处理效果及其影响因素。试验结果表明，经酸处理后的改性粉煤灰对制革废水具有较好的处理效果。     

Investigation of the uptake ability of fly ashes produced after lignite combustion

Fly ash samples from the five steam electric power stations of the Lignite Center of Western Macedonia were used in this study. They consisted mainly of anhydrite, lime, quartz and amorphous material as well as feldspars, calcite, micas + clays, portlandite and gehlenite which were all present in minor amounts. Anhydrite, lime and portlandite in the fly ash samples diminished upon treatment with ammonium acetate aqueous solution, whereas quartz, feldspars, gehlenite and amorphous material were enriched. The uptake ability of the fly ash samples ranged from 89 to 101 mequ./100g. The uptake ability of the samples was mainly attributed to the amorphous material and the microporous minerals, micas + clays. The amorphous material content was estimated at between 17 and 20 wt% in the treated fly ashes and may be unburned organic matter and amorphous inorganic material that resulted during the combustion of the lignite. A positive correlation was observed between the uptake ability and the total percentage of amorphous material and micas + clays. The relatively high uptake ability of the fly ash samples could lead to additional industrial and environmental uses of the fly ashes. The environmental advantage of fly ash exploitation will be particularly important for large electric power centers, such as the LCWM.     

Acidification-neutralization processes in a lignite mine spoil amended with fly ash or limestone

A laboratory experiment was conducted to investigate the longterm effects of amending sulfide-rich lignite mine spoil with fly ash (originating from a coal-fired power station and largely comprised of aluminosilicates) and/or agricultural limestone. The experiment was carried out with soil moisture maintained at field capacity or alternate cycles of wetting and drying. Results obtained suggest that the principal acidification processes were oxidation of sulfide and formation of hydroxysulfate (FeOHSO4), whereas the main neutralization processes were weathering of aluminosilicates in fly ash-treated samples and dissolution of calcium carbonate in limestone-treated samples. The highest dose of limestone rapidly raised the pH of the spoil, but this increase was not maintained throughout the one-year experiment. In contrast, fly ash-treated samples showed a more sustained increase in pH, attributable to the gradual weathering of aluminosilicates. The best results (i.e., good short- and long-term neutralization) were obtained in samples treated with both fly ash and limestone. The low liming capacity of the fly ash (47.85 cmol kg(-1)) means that it must be used in large quantities, an advantage in achieving the further aim of disposing of the fly ash.     

Impact of Coal Ash from Electric Power Production on Changes in Water Quality1

ABSTRACT: Since 1972 the use of coal in the U.S. has increased much more rapidly than predicted, with much of this increased use by electric power generating plants. Residue after combustion consists primarily of inorganic materials, with the majority of chemical elements concentrated in fly ash as is sulfate. The concentration of sulfate in this ash fraction most affects the chemical and physical state of other elements when fly ash comes in contact with water by lowering the pH. In a properly constructed and operated ash settling basin, however, major water quality parameters of effluent may be improved as compared to source water. It is necessary, however, to consider the solubility or deposition in sediment of potentially toxic chemical elements from fly ash as these may affect reuse of this water, or as they may impact other parts of the aquatic environment.     

粉煤灰在重金属废水处理中的应用

粉煤灰是一种可再资源化的工业固体废弃物。利用粉煤灰对重金属废水进行处理可谓是一种以废治废、变废为宝、实现废物综合利用的有效途径。综述了粉煤灰吸附法在重金属废水处理中的国内外研究现状,展望了该方法的应用前景。     

Growth and elemental accumulation by canola on soil amended with coal fly ash

To explore the agronomic potential of an Australian coal fly ash, we conducted two glasshouse experiments in which we measured chlorophyll fluorescence, CO2 assimilation (A), transpiration, stomatal conductance, biomass accumulation, seed yield, and elemental uptake for canola (Brassica napus) grown on soil amended with an alkaline fly ash. In Experiment 1, application of up to 25 Mg/ha of fly ash increased A and plant weight early in the season before flowering and seed yield by up to 21%. However, at larger rates of ash application A, plant growth, chlorophyll concentration, and yield were all reduced. Increases in early vigor and seed yield were associated with enhanced uptake of phosphorus (P) by the plants treated with fly ash. Fly ash application did not influence accumulation of B, Cu, Mo, or Zn in the stems at any stage of plant growth or in the seed at harvest, except Mo concentration, which was elevated in the seed. Accumulation of these elements was mostly in the leaves, where concentrations of Cu and Mo increased with any amount of ash applied while that of B occurred only with ash applied at 625 Mg/ha. In Experiment 2, fly ash applied at 500 Mg/ha and mixed into the whole 30 cm soil core was detrimental to growth and yield of canola, compared with restricting mixing to 5 or 15 cm depth. In contrast, application of ash at 250 Mg/ha with increasing depth of mixing increased A and seed yield. We concluded that fly ash applied at not more than 25 Mg/ha and mixed into the top 10 to 15 cm of soil is sufficient to obtain yield benefits.     

PDMDAAC改性粉煤灰预处理油墨废水的研究

本文介绍聚二甲基二烯丙基氯化铵（PDMDAAC）改性粉煤灰的制备,并用制备的改性粉煤灰处理实际油墨废水。研究改性粉煤灰的投加量、反应时间、废水pH值、水温对废水有机物CODG和色度去除率的影响。研究表明在最佳的试验条件下．油墨废水的脱色率高达94％,CODCr去除率也达到了74％。     

A study of the extraction of vanadium and nickel in oil-fired fly ash

Annual production of oil-fired fly ash in Taiwan is approximately 43 000 tons, of this approximately 13 000 tons is electrostatically precipitated, the rest is cyclonically collected. Structurewise, both consist of porous unburned carbon, vanadium and nickel oxide, and water-soluble sulfate. Electrostatically precipitated fly ash contains large amounts of ammonium sulfate. If these ashes are not properly disposed of, they become environmental problems, such as dusting, leakage of acid liquids, and pollution with heavy metals. This paper discusses the experimental extraction of vanadium and nickel from oil-fired fly ash. The results indicated that leaching of oil-fired fly ash in 0.5 N of sulfuric acid led to an extraction of 65% vanadium, 60% nickel, and 42% iron, along with an increase in the concentration of sulfuric acid. When leached in 2 N sodium hydroxide solution, the extraction of vanadium was 80%, and the extraction of nickel was negligible. If leached in an ammonia water, the extraction of nickel increased, along with an increase in the concentration of ammonia in water. When leached with 4 N ammonia water, the extraction of nickel was 60%, the extraction of vanadium was less than that obtainable from leaching in sulfuric acid solution or in sodium hydroxide solution. If electrostatically precipitated fly ash was leached in a solution of 0.25 N ammonia water and 2 N ammonium sulfate, it would yield an extraction of 60% nickel and 8% vanadium—leading to a selective extraction of nickel. This study has established an extraction flowsheet in which fly ash was first leached in an ammoniacal solution containing ammonium sulfate to recover nickel. The leached residues were then leached in an alkaline solution to recover vanadium.     

Characterization of MSWI fly ash through mineralogy and water extraction

This paper investigates the mineralogical characteristics of fresh, aged and hot water extracted MSWI fly ash for providing the baseline information of minerals stability which controls the released heavy metals into the environment. Quantitative determination of bulk phase abundance in the fresh fly ash by the XRD Rietveld refinement method provided composition levels for amorphous and crystalline phases such as potassium tetrachlorozincate (K₂ZnCl₄), gehlenite, halite, quartz, anhydrite, and feldspar. The minerals association in the fly ash is clearly unstable and subject to mineralogical reactions. The phases of K₂ZnCl₄, halite and anhydrite in the fresh fly ash were involved in hydration and dissolution/precipitation processes to form new minerals such as the Zn-bearing mineral gordaite, syngenite, gypsum and hydrocalumite. The solubility-controlling phases and extractability of heavy metals were examined in a Soxhlet hot water-extractor. Here the soluble salts were simply removed from fly ash while Ca-, Al-, Si- and SO₄²⁻-bearing hydrate minerals were precipitated from the extraction solution. Furthermore, a low release of heavy metals Zn, Pb and Cd in hot water was noticed, indicating a strong retention of the trace metals in the mineral phases remaining in the insoluble fly ash residues.     

Use of ready-mixed concrete plant sludge water in concrete containing an additive or admixture

In this study, we investigated the feasibility of using sludge water from a ready-mixed concrete plant as mixing water in concrete containing either fly ash as an additive or a superplasticizer admixture based on sulfonated naphthalene-formaldehyde condensates (SNF). The chemical and physical properties of the sludge water and the dry sludge were investigated. Cement pastes were mixed using sludge water containing various levels of total solids content (0.5, 2.5, 5, 7.5, 10, 12.5, and 15%) in order to determine the optimum content in the sludge water. Increasing the total solids content beyond 5–6% tended to reduce the compressive strength and shorten the setting time. Concrete mixes were then prepared using sludge water containing 5–6% total solids content. The concrete samples were evaluated with regard to water required, setting time, slump, compressive strength, permeability, and resistance to acid attack. The use of sludge water in the concrete mix tended to reduce the effect of both fly ash and superplasticizer. Sludge water with a total solids content of less than 6% is suitable for use in the production of concrete with acceptable strength and durability.     

Strontium isotope study of coal utilization by-products interacting with environmental waters

Sequential leaching experiments on coal utilization by-products (CUB) were coupled with chemical and strontium (Sr) isotopic analyses to better understand the influence of coal type and combustion processes on CUB properties and the release of elements during interaction with environmental waters during disposal. Class C fly ash tended to release the highest quantity of minor and trace elements-including alkaline earth elements, sodium, chromium, copper, manganese, lead, titanium, and zinc-during sequential extraction, with bottom ash yielding the lowest. Strontium isotope ratios ((87)Sr/(86)Sr) in bulk-CUB samples (total dissolution of CUB) are generally higher in class F ash than in class C ash. Bulk-CUB ratios appear to be controlled by the geologic source of the mineral matter in the feed coal, and by Sr added during desulfurization treatments. Leachates of the CUB generally have Sr isotope ratios that are different than the bulk value, demonstrating that Sr was not isotopically homogenized during combustion. Variations in the Sr isotopic composition of CUB leachates were correlated with mobility of several major and trace elements; the data suggest that arsenic and lead are held in phases that contain the more radiogenic (high-(87)Sr/(86)Sr) component. A changing Sr isotope ratio of CUB-interacting waters in a disposal environment could forecast the release of certain strongly bound elements of environmental concern. This study lays the groundwork for the application of Sr isotopes as an environmental tracer for CUB-water interaction.     

LQZ型气力输送系统在电厂除灰中的应用

介绍了气力输送系统在电厂660MW机组除灰中的应用,并对飞灰特性,以及除灰系统设计、关键技术运用、运行情况、设备维护和故障处理等问题进行了分析论述。     

Influence of fly ash on soil physical properties and turfgrass establishment

A field study (1993-96) assessed the benefits of applying unusually high rates of coal fly ash as a soil amendment to enhance water retention of soils without adversely affecting growth and marketability of the turf species, centipedegrass [Eremochloa ophiuroides (Munro) Hack.]. A Latin Square plot design was employed that included 0 (control, no ash applied), 280, 560, and 1120 Mg ha-1 application rates of unweathered precipitator fly ash. The fly ash was spread evenly over each plot area, rototilled, and allowed to weather under natural conditions for 8 mo before seeding. High levels of soluble salts, indicated by the electrical conductivity (EC) of soil extracts, in tandem with an apparent phytotoxic effect from boron (B), apparently inhibited initial plant establishment as shown by substantially lower germination counts in treated soil. However, plant height and rooting depth were not adversely affected, as were the dry matter (DM) yields throughout the study period. Ash treatment did not significantly influence water infiltration rate, bulk density, or temperature of the soil, but substantially improved water-holding capacity (WHC) and plant-available water (PAW). Enhanced water retention capacity improved the cohesion and handling property of harvested sod.