Effect Of Coal Ash Research Articles

Effects of Coal Ash and Walnut Shell on the Impact Resistance and Mechanical Properties of Eco-Efficient Self-Compacting Concrete

Effects of Coal Ash and Walnut Shell on the Impact Resistance and Mechanical Properties of Eco-Efficient Self-Compacting Concrete

Effect of coal ash on the reduction and roasting processes of phosphogypsum

Effect of coal ash on the reduction and roasting processes of phosphogypsum

Effect of coal ash and rice husk ash partial replacement in ordinary Portland cement on pervious concrete

Pervious concrete is a common green infrastructure material with a low-impact development technology that provides a water-sustainable engineering solution for urban cities. This study investigates an effective way to reuse coal fly ash (CFA), coal bottom ash (CBA), and rice husk ash (RHA) as partial replacements of ordinary Portland cement in pervious concrete. In experiments, single and binary replacement by these ash materials was conducted via cement material substitution in pervious concrete. The pervious concrete specimens contained 30% ash by volume and had a water-to-cement ratio of 0.21. The ash materials and pervious concrete specimens were characterized by field emission-scanning electron microscopy, X-ray fluorescence spectroscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The compressive strength, water permeability, and toxicity characteristic leaching procedure (TCLP)-released metals were investigated to evaluate the pervious concrete quality. The compressive strength of pervious concrete with single-ash partial replacement by CFA and CBA was higher than that of the control group and two specimens that contain single-ash partial replacement by RHA (sintered to 550 and 900 °C). The five pervious concrete specimens with binary partial replacement of RHA (sintered to 550 and 900 °C), CFA, CBA and CBA (sintered to 1100 °C) showed a synergistic effect and had a higher compressive strength than the control group and single-ash partial replacement with RHA (sintered to 550 and 900 °C) at 90 days. The water permeability ranged between 0.101 and 0.313 cm/sec, and the TCLP-released metal concentrations from all specimens satisfied the regulatory standards of Taiwan. The result of the carbon footprint showed that the replacement of ash materials reduced the total carbon footprint by 9.9%–20.6% per m3 of pervious concrete compared to the control group. The results indicated that CFA, CBA, and RHA replacement in cement materials yielded an acceptable compressive strength and water permeability.

WITHDRAWN: Effect of coal ash on strength characteristics of clayey silt soil treated with cement

Coal-based thermal power plants produce coal ash as a by-product and the major concern is for handling and disposal of coal ash without adversely affecting the environment. There is a feasibility to utilize the coal ash in an environmentally safe manner in geotechnical engineering applications. To achieve this objective, an experimental investigation was conducted in which coal ash was used as replacement material in soil mixtures. A clayey silt soil was used in this study and class F type coal ash (CA) was blended in different proportions up to 50% by mass of the soil. The testing program comprised characterization of soil and coal ash, compaction tests and California bearing ratio (CBR) tests. The stress–strain and strength characteristics of compacted soil with coal ash and cement were analyzed. The test results showed that all the mixes achieved a higher CBR value than the control specimen. The optimum coal ash contents for clayey silt–coal ash mixes were found as 20% and 50% which showed higher CBR value, it could be due to the packing effect and imparting cohesion, respectively. The minimum cement content of 1% to the optimum mixes provided a significant improvement in CBR values of 25.19% and 29.14% as compared to the control specimen of 4.72%. These results are acceptable values and hence, the coal ash blended soil is found to be suitable for pavement subgrade and embankments constructions.

Effect of Coal Ash on Fe-Based Oxygen Carrier in Coal Char Chemical Looping Gasification

Abstract Chemical looping gasification (CLG) is a cost-effective alternative to the traditional fossil conversion process. In this article, the effects of three different types of coal ash on Fe-based oxygen carrier in coal char CLG were investigated. The composition of coal ashes and the microstructure of Fe4Al6 oxygen carrier were characterized by SEM-EDS, XRD and BET. The effects of different components of coal ash (SiO2, CaO, and K2O) were examined, and their effect mechanisms were analyzed. The findings suggested that the effect of coal ash on Fe4Al6 oxygen carrier could be divided into three aspects: (i) inhibition effect by forming low-melting-point compounds; (ii) enhancement effect through catalysis or formation of specific structure; and (iii) neutral effect by integrating with oxygen carrier. In addition, the formation of low-melting-point compounds, which is mainly due to SiO2 and CaO, was found to cause sinter and agglomeration of oxygen carrier. Moreover, potassium salts were found to either act as catalysts or cause the formation of K-Fe-O compounds; they promoted the release of lattice oxygen from oxygen carrier while enhanced oxygen carrier’s stability. The findings suggested that coal ash containing high content of K2O and Fe2O3 could enhance the performance of oxygen carrier during CLG.

Effects of coal ash on iron‐based oxygen carrier in chemical‐looping combustion using three different rank coals as fuel

AbstractThe combustion characteristics vary with coal rank changes, and coal ash has a significant effect on chemical looping combustion. In this work, combustion experiments of three coals and their acid‐washing samples were carried out in a bench‐scale fluidized bed reactor. The results showed that low‐rank coal had higher reactivity and shorter reduction time. On account of high volatility and low density, combustion efficiency of high volatile coal was lower than high‐rank coal resulting in lower CO2 concentration. CO2 concentration in combustion products of GY was up to 99.95%, but it was 91.2% for SF. The composition and content of coal ash had a great influence on the activity of the iron‐based oxygen carrier. Reactivity of the oxygen carrier was significantly increased after burning high Ca content coal, and ash shortened reduction time from 46 to 35 min. The coal with high Si content had negative effect on the reactivity of oxygen carriers. The coal ash mainly affected the oxygen carrier at the later stage of the reduction.

Effects of Coal Ash on CuO as an Oxygen Carrier for Chemical Looping with Oxygen Uncoupling

Chemical looping with oxygen uncoupling (CLOU) features the natural release of gaseous oxygen from oxygen carriers to efficiently burn solid fuels, producing a nearly nitrogen-free CO2 stream for c...

Effect of Ash Components on the Performance of Solid Oxide Electrolyte-Based Carbon Fuel Cells

The effect of coal ash on the electrochemical performance of solid oxide electrolyte-based carbon fuel cells (SO-CFCs) is investigated in this study. The polarization and durability performance of SO-CFCs fueled by lignite char, ash-free char, and ash-added char were measured and compared from 1023 to 1123 K. The influence of five different coal ashes and six typical inorganic species was evaluated in SO-CFCs during short-term operation. The anode morphologies were analyzed to clarify the cell degradation. The results indicate that lignite char shows a higher initial cell performance but a lower stability than ash-free char in SO-CFC. The higher initial cell performance is attributed to the superior CO2 gasification reactivity, while the lower stability is more likely caused by carbon and ash deposits. The effect of coal ash on the cell performance is strongly dependent upon the ash composition. Inorganic Ca, K, and Fe species in coal ash improve the initial cell performance by catalyzing char–CO2 gasific...

In situ reclamation of closed coal mine waste in Korea using coal ash

Adding coal ash to acid waste decreases its acidity and supplies essential nutrients to plants. The effects of coal ash on acid coal mine waste and acid mine drainage were investigated in the field. Treatments were mixtures of coal mine waste with coal ash (0, 20, and 40%). Addition of coal ash increased the pH of coal mine waste and leachate by 3.11 and 3.03 units, respectively. After stabilization, the concentrations in the leachate decreased from 4.65 to 0.44 mg L−1 for Fe and from 0.31 mg L−1 to “not detected” for Pb. The organic matter content and cation exchange capacity increased significantly (approximately twofold each), for coal mine waste with coal ash. Moreover, plant growth on coal mine waste that had been treated with coal ash was greatly stimulated. The application of coal ash offers an environmentally compatible, cost-effective way to remediate coal mine waste or leachate contaminated with heavy metals.

Effect of Coal Ash on the Steam Reforming of Simulated Bio-oil for Hydrogen Production over Ni/γ-Al2O3

An improved system for hydrogen production by the steam reforming of simulated bio-oil was developed. The coal ash was packed in front of nickel-based catalysts, acting as a guard catalyst. The model compounds passed through coal ash and were preliminarily reformed to smaller molecular intermediates containing more CO and CH4, which were then further reformed over the following nickel-reforming catalyst. The improved reaction system succeeded in effectively converting the complex simulated bio-oil into hydrogen and exhibited high activity. For 15 wt.% Ni/γ-Al2O3 catalyst with coal ash packing, the catalyst lifetime was extended to 8 h, with simulated bio-oil almost completely converted into hydrogen. In addition, coke deposition was suppressed.

Sulfur transformation during the pyrolysis of coal mixed with coal ash in a fixed bed reactor

The Xiaolongtan coal with different blend ratios (ash/coal) of ash was pyrolyzed in a fixed bed reactor to study sulfur transformation during the pyrolysis of the mixture of coal and coal ash. The addition of coal ash inhibited H2S evolution at low temperatures, and this was because H2S was captured by Fe2O3 of the coal ash. However, the coal ash promoted H2S evolution at high temperatures, which should be due to the reaction 4H2+CaSO4→CaO+3H2O+H2S. More COS was evolved with the addition of coal ash at 700–800°C, and the possible reason was that COS could be produced through the reactions 4CO+CaSO4→CaO+3CO2+COS and 2C+CaSO4→CaO+CO2+COS. The addition of coal ash reduced tar sulfur. The effects of the conditions (temperature of ash preparation and atmosphere) on the sulfur containing gas were also discussed. The evolution of H2S and COS were less affected by the ash prepared under 1000°C than that under 800°C and 900°C. The possible reason was that the reactions among the volatile matters and coal ash were unfavorable due to the sintering of the ash under 1000°C. The effect of coal ash on H2S and COS under simulated pyrolyzed gas atmosphere was similar to that under N2 atmosphere, but higher H2S and COS yields were obtained under simulated pyrolyzed gas atmosphere.

Modeling Fireside Corrosion Rate in a Coal Fired Boiler Using Adaptive Neural Network Formalism

In this paper, an efficient artificial neural network (ANN) model using multi-layer perceptron (MLP) philosophy has been proposed to predict the fireside corrosion rate of super heater tubes in coal fire boiler assembly, using operational data of an Indian typical thermal power plant. The input parameters comprise coal chemistry, namely, coal ash and sulfur contents, flue gas temperature, SOX concentrations in flue gas, fly ash chemistry (wt% Na2O and K2O). An efficient gradient based network training algorithm has been employed to minimize the network training errors. Effects of coal ash and sulfur contents, wt% of Na2O and K2O in fly ash and operating variables such as flue gas temperature and percentage excess air intake for coal combustion on the fireside corrosion behavior of super heater boiler tubes have been computationally investigated and parametric sensitivity analysis has been undertaken. It has been observed that ash and sulfur contents of coal, flue gas temperature and fly ash chemistry have a relatively predominant influence on the rate of fireside corrosion with respect to other parameters. Quite good agreement between ANN model predictions and the measured values of fireside corrosion rate has been observed, which is corroborated by the regression fit between these values. © 2016, Sociedade Portuguesa de Electroquimica. All rights reserved. Modeling Fireside Corrosion Rate in a Coal Fired Boiler Using Adaptive Neural Network Formalism. Available from: https://www.researchgate.net/publication/303782462_Modeling_Fireside_Corrosion_Rate_in_a_Coal_Fired_Boiler_Using_Adaptive_Neural_Network_Formalism [accessed Aug 16, 2017].

Gasification of Inferior Coal with High Ash Content under CO2 and O2/H2O Atmospheres

The gasification reaction of Nantong inferior coal was investigated in a laboratory fixed-bed reactor under CO2 and O2/H2O atmospheres. The effects of the bed temperature and inlet-gas concentration on the yields of CO, H2, and CH4 were studied. The effects of coal ash and particle size on the fixed-carbon conversion were also investigated, and kinetic analysis was conducted with a homogeneous model. The product-gas-heating value and fixed-carbon conversion increased when the temperature was increased from 950 °C to 1100 °C under CO2 atmosphere. When the inlet-CO2 concentration was increased from 50 to 100 vol.%, the low heating value of the product gas and carbon conversion ratio slightly increased. During the gasification of inferior coal under the O2/H2O atmosphere, the CO concentration increased rapidly with increasing temperature. The H2 and CH4 concentrations increased initially and then decreased. The maximum gas heating value of 7934 kJ/m3 was obtained under the O2 concentration of 70 vol.% at a bed temperature of 1050 °C. The cold-gas efficiency increased with increasing temperature and became 40.6% and 86.4% at 1100 °C under the CO2 and O2/H2O atmospheres, respectively. The gasification reaction of the Nantong inferior coal strongly depended on the content of inherent inorganic matter. The gasification rates for both the CO2 and O2/H2O atmospheres were independent of the particle size. The activation energy for the CO2 and O2/H2O gasification reactions were 137 and 81 kJ/mol, respectively. The gasification reactions of the Nantong coal, which was performed under two different atmospheres, were compared and the reaction activity of the gasification reaction under CO2 atmosphere was found to be much lower than that under the O2/H2O atmosphere.

Effect of Coal Ash on Strength and CBR Properties of Lacustrine Soil

Effect of Coal Ash on Strength and CBR Properties of Lacustrine Soil

Effect of coal ash on the performance of alloys in simulated oxy-fuel environments

Oxy-fuel combustion can increase efficiency and reduce pollution from coal power plants. To study material performance in an oxy-fuel environment, both Fe- and Ni-based alloys were exposed to simulated oxy-fuel environments at 750°C for long terms up to 6300h. The effects of ash and gas compositions (SO2, CO2, H2O and O2) on the performance of alloys were studied. Results from these tests are used to address the role of CO2, steam, and ash in the long-term corrosion performance of alloys. Detailed results are presented on weight change, scale thickness, internal penetration, microstructural characteristics of corrosion products, and cracking of scales for the alloys. Oxide scales were studied by synchrotron nano-beam X-ray diffraction.An incubation period and a propagation period were observed for ash corrosion. Before incubation time, alloys gain weight. After incubation time, localized corrosion damages the protective scales, alloys lose weight and corrosion rates dramatically increase. Since the incubation time can be over 4000h, long-term test results are more helpful in evaluating the alloy performance in an oxy-fuel combustion environment with ash than the results from a short-term test. The mechanism of ash corrosion is also discussed.

Environmental Impacts of the Tennessee Valley Authority Kingston Coal Ash Spill. 2. Effect of Coal Ash on Methylmercury in Historically Contaminated River Sediments

The Tennessee Valley Authority Kingston coal ash spill in December 2008 deposited approximately 4.1 million m(3) of fly ash and bottom ash into the Emory and Clinch River system (Harriman, Tennessee, U.S.A.). The objective of this study was to investigate the impact of the ash on surface water and sediment quality over an eighteen month period after the spill, with a specific focus on mercury and methylmercury in sediments. Our results indicated that surface water quality was not impaired with respect to total mercury concentrations. However, in the sediments of the Emory River near the coal ash spill, total mercury concentrations were 3- to 4-times greater than sediments several miles upstream of the ash spill. Similarly, methylmercury content in the Emory and Clinch River sediments near the ash spill were slightly elevated (up to a factor of 3) at certain locations compared to upstream sediments. Up to 2% of the total mercury in sediments containing coal ash was present as methylmercury. Mercury isotope composition and sediment geochemical data suggested that elevated methylmercury concentrations occurred in regions where native sediments were mixed with coal ash (e.g., less than 28% as coal ash in the Emory River). This coal ash may have provided substrates (such as sulfate) that stimulated biomethylation of mercury. The production of methylmercury in these areas is a concern because this neurotoxic organomercury compound can be highly bioaccumulative. Future risk assessments of coal ash spills should consider not only the leaching potential of mercury from the wastes but also the potential for methylmercury production in receiving waters.

Sonochemical decomposition of hydrazine in water: Effects of coal ash and pH on the decomposition and adsorption behavior

Sonochemical decomposition of hydrazine in aqueous suspension of coal ash particles was investigated in the different pH solutions. It was clearly found that the initial rate of hydrazine decomposition and adsorption is strongly dependent on the amount of coal ash and pH. At pH 1, the amount of the hydrazine adsorption on coal ash was very small and hydrazine was mainly decomposed by ultrasonic irradiation. At pH 4, hydrazine was mainly adsorbed on coal ash and not decomposed by ultrasonic irradiation. At pH 8, the sonochemical decomposition and the adsorption on coal ash proceeded simultaneously. These results were due to the interactions between the degree of the protonation of hydrazine, the electric charge of coal ash and the amount of OH radicals formed in the sonolysis of water.

Reactivity deterioration of NiO/Al 2O 3 oxygen carrier for chemical looping combustion of coal in a 10 kW th reactor

A relatively long-term experiment for chemical looping combustion of coal with NiO/Al 2O 3 oxygen carrier was carried out in a 10 kW th continuous reactor of interconnected fluidized beds, and 100 h of operation was reached with the same batch of the oxygen carrier. The reactivity deterioration of the oxygen carriers was present during the experimental period. The reactivity deterioration of reacted oxygen carriers at different experimental stages was evaluated using X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray fluorescence spectrometer. SEM analysis showed no significant change in the morphology of the nickel-based oxygen carrier at the fuel reactor temperature ⩽940 °C, but loss of surface area and porosity of reacted oxygen carriers was observed when the fuel reactor temperature exceeded 960 °C. The results show that the sintering effect have mainly contributed to the reactivity deterioration of reacted oxygen carriers in the CLC process for coal, while the effects of coal ash and sulfur can be ignored. The oxidization of reduced oxygen carrier with air was an intensive exothermic process, and the high temperature of oxygen carrier particles led to sintering on the surface of oxygen carrier particles in the air reactor. Attention must be paid to control the external circulation of oxygen carrier particles in the interconnected fluidized beds in order to efficiently transport heat from the air reactor to the fuel reactor, and reduce the temperature of oxygen carrier particles in the air reactor. Improvement of reactivity deterioration of reacted oxygen carriers was achieved by the supplement of steam into the fuel reactor. Nevertheless, NiO/Al 2O 3 is still one of the optimal oxygen carriers for chemical looping combustion of coal if the sintering of oxygen carrier is minimized at the suitable reactor temperature.

Correlation between organic acid exudation and metal uptake by ectomycorrhizal fungi grown on pond ash in vitro

Experiments were conducted to investigate the effect of coal ash on organic acid exudation and subsequent metal uptake by ectomycorrhizal fungi. Four isolates of ectomycorrhizal fungi namely, Pisolithus tinctorius (EM-1293 and EM-1299), Scleroderma verucosum (EM-1283) and Scleroderma cepa (EM-1233) were grown on pond ash moistened with Modified Melin-Norkans medium in vitro. Exudation of formic acid, malic acid and succinic acid by these fungi were detected by HPLC. Mycelial accumulation of Al, As, Cd, Cr, Ni and Pb by these fungi was assayed by atomic absorption spectrophotometer. Relationship between organic acid exudation and metal uptake was determined using classical multivariate linear regression model. Correlation between organic acid exudation and metal uptake could be substantiated when several metals are considered collectively. The finding supports the widespread role of low molecular weight organic acid as a function of tolerance, when exposed to metals in vitro.

Effect of coal ash on hydrazine degradation under stirring and ultrasonic irradiation conditions

The degradation of hydrazine (N2H4) with concentrations of 0.1–5.0mmol/L was investigated as a function of amount of coal ash (0.0–5.0wt%) under the stirring (300rpm) and ultrasonic irradiation (200kHz, 200W) conditions. It was found that the rate of decrease in the hydrazine concentration depended upon an amount of coal ash under the stirring and ultrasonic irradiation condition. It was considered under the stirring condition that hydrazine was adsorbed and degraded partly on coal ash. Furthermore, the sonochemically formed OH radicals were more effective in the hydrazine degradation than stirring condition in the presence of an intermediate amount of coal ash (0.6–2.4wt%), whereas the effect of OH radicals disappeared in the presence of coal ash more than 2.4wt%.