Coal Combustion Products Research Articles

Study on petrographic characteristics of devolatilization char/coke related to coal rank and coal maceral

Char/coke is the medium product of coal gasification, combustion, and metallurgy, whose morphological and optical characteristics are determined by coal rank and pyrolysis conditions. Twelve coals varying in coal rank from lignite to anthracite, collected in China, were used to study morphological and optical characteristics of char/coke upon different pyrolysis conditions systematically, specifically the char/coke structure and texture influenced by coal rank and coal maceral. Coke and char are distinguished by their caking ability. The morphology of the chars derived from low rank coals and high rank coals are closely related to coal maceral composition, whereas the morphology of cokes derived from high volatile bituminous A, medium, and low volatile bituminous is closely related to coal rank. In lignite, subbituminous, high volatile bituminous C, semianthracite, and anthracite, macerals are infusible during the heating process, but cavities generated in the low rank coals are related to the shapes of the liptinite macerals in the raw coals. Morphological changes of chars derived from high rank coals are difficultly to identify microscopically using an oil-immersion objective with a 1-lambda gypsum plate. in addition, the random reflectance (Rr) range of the chars becomes narrower as pyrolysis temperature increases. Overall, the Rr range of cokes is much larger than that of the chars, which is a result of the optical anisotropy of the caking coals. Although the Rr of vitrinite/huminite in the low and high ranks is distinct, the Rr of their chars is always similar when the pyrolysis conditions are the same. The Rr of char/coke is closely related to both coal rank and the final pyrolysis temperature. Longer residence time of the char/coke at the same pyrolysis temperature did not show a relevant difference in the reflectance of char/coke.

ANALISIS KANDUNGAN LOGAM BERAT ABU BATUBARA PLTU BANGKO BARAT KAB. MUARA ENIM SUMATERA SELATAN

Coal combustion product (CCP) from Bangko Barat Power Plant is used as landfill material in acidic overburden layers. CCP is categorized as hazardous and toxic waste (PP No.101/2014) from specific sources and is known to contain heavy metals. This study aims to analyze the heavy metal content of coal combustion product from Bangko Barat Power Plant, Muara Enim Regency, South Sumatra Province. Heavy metal content of CCP includes Hg, Cd, Cu, Ag, Ni, Pb, As, Cr, Sn, Zn dan Mn. Heavy metal content analysis to ensure overburden piling by utilizing CCP, either with a long-term safe coating or mixing scheme. The analysis was carried out by using ICP-MS test, XRF test, XRD test, analysis of grain size and grain morphology. Samples of fly ash and bottom ash were categorized as non- hazardous and toxic waste based on the results of the ICP-MS test compared to the values of TK-A, TK-B and TK-C. Heavy metal content that needs attention from coal ash is As (4.4-20 ppm), Cr (26-43 ppm), Cu (30.7-42.6 ppm), Pb (22,2-29,3 ppm), Zn (77.5-128 ppm), Ni (10,6-24,8 ppm) and Mn (144-396 ppm). The content of other heavy metals is relatively low (Hg, Cd, Ag and Sn) and the threshold is not exceeded. Monitoring the quality of runoff water from landfill area using CCP to be controlled so that the heavy metal content does not endanger the health of living things.

Mineralogical and Chemical Characteristics of Coal Ashes from Two High-Sulfur Coal-Fired Power Plants in Wuhai, Inner Mongolia, China

The mineralogical and chemical characteristics of the feed coals and coal combustion products (CCPs) from two power plants (Xilaifeng and Damo) that consume coals from the Wuda Coalfield, Inner Mongolia, were investigated, using XRD, SEM–EDS, XRF, and ICP-MS. The feed coals from Xilaifeng and Damo are both of high ash yield (52.93% and 48.36%, respectively), and medium and high total sulfur content (2.22% and 3.32%, respectively). The minerals in the feed coals are primarily composed of kaolinite, quartz, illite, pyrite, and, to a lesser extent, gypsum and anatase. In addition to the elevated incompatible elements (Nb, Ta, Zr, Hf and Th), Li and Hg are enriched in the feed coals from the Xilaifeng and Damo power plants, respectively. Rare earth elements and yttrium (REY) are more enriched in the feed coals from Xilaifeng (194 μg/g) than those of Damo (93.9 μg/g). The inorganic phases of CCPs from both power plants are mainly composed of amorphous phase, quartz, hematite, illite, and anhydrite. Compared with the feed coals, concentrations of most trace elements in the CCPs are elevated, and they are preferentially enriched in the fly ashes relative to the bottom ashes (*f/b > 1), especially F, As, Sr, Mo, Se, and Hg (*f/b > 2.5). Furthermore, most trace elements (Xilaifeng: excluding Li, Cr, Co, Ni, Rb, Nb and Cs; Damo: excluding Li, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Cs and Ba) are more enriched in the (fine) fly ashes relative to the laboratory high-temperature coal ashes (HTAs). The REY barely differentiate in either the fly ash or bottom ash from Xilaifeng. In contrast, the REY in the fine and coarse fly ashes from Damo have very similar H-type distribution patterns with negative Ce and slightly positive Y anomalies. Attention should be paid to the enriched toxic elements (including F, As and Hg) in the fly ashes from both power plants due to possible adverse environmental effect.

The effect of coal bottom ash as a replacement on subgrade strength

Coal Bottom Ash (CBA) which is one of coal combustion product (CCPs) obtained from thermal power plant will negatively affect the ecological system which human health ultimately depends on. The increase in demands for landfill requirements and the limitations natural aggregates is quite disturbing unless the new alternative to cut the usage of natural aggregates is found. Therefore, this paper present the laboratory investigation work to improve the strength of subgrade by the replacement of CBA with different percentage varies (0%, 15%, 30% & 40%) by weight. California Bearing Ratio (CBR) test is carried out to obtain the optimum percentage replacement CBA and then some physical which are particle size distribution, Atterberg limit test, specific gravity test and compaction test also carried out to observe the mechanical properties of optimum sample. The optimum percentage of CBA replacement obtained is 40.65% at 30% CBA replacement compared to 17.99% of subgrade soil alone. The moisture dry-density of unmodified soil sample is higher (1.99Mg/m3, 15.34%) than optimum sample (1.95Mg/m3, 10.2%). Moreover, 30% CBA replacement resulted in intermediate plasticity than the subgrade soil which is highly plastic. In conclusion, strength of subgrade soil is highest at 20-30% of CBA replacement.

Impact of fly ash fractionation on the zeolitization process.

Coal combustion product in the form of fly ash has been sieved and successfully utilised as a main substrate and a carrier of silicon and aluminium in a set of hydrothermal syntheses of zeolites. The final product was abundant in zeolite X phase (Faujasite framework). Raw fly ash as well as its derivatives, after being sieved (fractions: ≤ 63, 63–125, 125–180 and ≥ 180 µm), and the obtained zeolite materials were subjected to mineralogical characterisation using powder X-ray diffraction, energy-dispersive X-ray fluorescence, laser diffraction-based particle size analysis and scanning electron microscopy. The influence of fraction separation on the zeolitization process under hydrothermal synthesis was investigated. Analyses performed on the derived zeolite X samples revealed a meaningful impact of the given fly ash fraction on synthesis efficiency, chemistry, quality as well as physicochemical properties, while favouring a given morphological form of zeolite crystals. The obtained zeolites possess great potential for use in many areas of industry and environmental protection or engineering.

Application of Organic Fuel Additives to Enhance Coal Combustion Efficiency

The results from numerical and experimental investigations into the influence of organic fuel additives (OFAs) on the efficiency of combusting high-ash Ekibastuz coal are presented. Technology and a special combustion chamber equipped with a plasma-assisted startup system are proposed. The thermodynamic and kinetic parameters of cocombustion of coal with OFA are numerically analyzed, as a result of which the optimum process temperatures, air-to-coal mass consumption ratios, and combustion chamber geometrical parameters have been selected. Thermodynamic analyses of the coal combustion process have shown that 7 kg of air is required to burn 1 kg of coal. A tendency toward increasing the concentrations of CO2 and Н2О and, accordingly, toward decreasing the concentrations of NO, СО, and O2 in the coal combustion products in using OFA has been revealed. The kinetic analysis results have shown that the coal combustion process with a consumption rate of 10 kg/h is fully completed in a combustion chamber 0.2 m in diameter and 0.9 m in height. A series of experiments on cocombustion of Ekibastuz coal with OFA was carried out. The investigation results made it possible to evaluate the effectiveness of Omstar-DX1 and Open Flame OFAs, which are prepared as mixtures of light ethers. Comparative experiments of coal combustion with and without OFAs in different concentrations (0–5 cm3 per kg of coal) have shown that the OFAs increase the flame temperature in the combustion chamber’s initial part and decrease this temperature at the chamber’s outlet. This means that the air–coal mixture takes less time to ignite and, accordingly, it burns out more rapidly. The introduction of OFAs results in a noticeably more efficient combustion of low-grade coal, in smaller emissions of CO and NO, and in an increased concentration of CO2, which points to the more complete combustion of fuel.

Study Of The Utilization Of Carbide Waste And Fly Ash On Geopolymer Paste

Portland cement is made of the main ingredients are limestone / lime are included in natural resource that is not renewable. So that needs holding replacement with environmentally friendly materials one of which is of geopolymer concrete. Fly Ash is the waste coal combustion products also include natural resources that can not be refurbished Based on data obtained from PT. Z, carbide waste generated in a year on average around 1978.72 m3, it can be put to good use for waste carbide itself has a high CaO content. The composition of the material used in this study was 100% waste carbide, carbide waste 50%: 50% fly ash, as well as 100% fly ash and the activator used as NaOH and Na2SiO3. This study aims to determine how much influence the utilization of waste carbide and fly ash in geopolymer paste in the testing setting time, compressive strength, porosity, UPV, and permeability. The highest compressive strength besides there on the composition of a 100% fly ash is also present in 50% of waste carbide composition: 50% fly ash with activator ratio of 0.5 at the age of 56 days amounted to 39.59 Mpa. The use of fly ash in geopolymer still can not be eliminated 100%, due to the utilization of waste carbide can only be used as an additive or filler.

Quantitative assessment of the impact of ecological energy sources on atmospheric pollution

Environmental pollution, in particular atmospheric pollution, is largely associated with the production of thermal energy. Suspended dusts and chemically aggressive gases generate a significant danger for as well human health as biosphere. In recent years there has been a growing conviction about decisive impact of greenhouse gasses emission generated by the economic and civilizational activity of humanity on global climate changes. Hopes of breaking these adverse trends is connected with the mass use of renewable energy sources or rather so called ecological energy sources, that are relatively less environmentally aggressive. The quantitative comparative assessment of their negative impact on the environment is important in the proper classification of energy sources. Comparing of quantities of emitted suspended dusts and aggressive gases including greenhouse gases is good parameter for evaluation of air pollution. In Polish conditions, atmospheric pollutions are predominated by products of coal combustion. A good indicator of the ecological quality of energy sources is therefore the reduction of emitted harmful substances as a result of coal substitution. In this work examples of ecological effects of geothermal installations have been presented. Geothermal energy is generally considered to be renewable and ecological, while the substitution of coal fuels by hydrocarbons, including natural gas, is more problematic. The comparative analysis performed for a single-family house shows a radical reduction in the emission of suspended dust and chemically aggressive gases associated with replacing the coal furnace by natural gas-fired boiler and reducing the emission of carbon dioxide by half.

Increasing coal combustion product utilization in Russia as a crossindustry goal

Increasing coal combustion product utilization in Russia as a crossindustry goal

Partitioning of rare earth elements and yttrium (REY) in five coal-fired power plants in Guizhou, Southwest China

As indispensable strategic materials for high-tech industries, rare earth elements and yttrium (REY) have become particularly important in recent years, raising the demand of developing new approaches for reclamation of REY from REY-rich materials such as coal combustion products (CCPs). In this study, five coal-fired power plants (CFPPs) in Guizhou of southwest China were selected for investigating REY concentrations of solid samples, atmospheric emissions, and recovery potentials. REY concentrations of feed fuels are higher in this study (147.2–468.6 mg/kg) than what have been reported previously for coals in China and the world. REY atmospheric emissions are extremely low (38.70–180.11 mg REY/t coal). REY are enriched in bottom ash and fly ash, with average of 658 ± 296 mg/kg and maximum of 1257 mg/kg from the five CFPPs. Relative enrichment factors (REF) of REY in bottom ash and fly ash compared with the feed fuel are 0.86–1.02 and 0.91–1.04, respectively. REY concentrations in desulfurized gypsum are very low (6–17 mg/kg), and that is mostly inherited from limestone. Critical REY (Nd, Eu, Tb, Dy, Y, and Er) in bottom/fly ash account for 34%–39% of the total REY and the outlook coefficients (Coutl) are in the range of 0.89–1.11. This study indicates a promising prospect to reclaim REY from REY-rich CCPs (bottom and fly ash) in CFPPs in Guizhou, especially in the central-north Guizhou, although such practices require further technology advancement.

Supercritical solvent extraction of lignite combustion products by water and HNO3 – Rare Earth Elements recovery study

Coal Combustion Products (CCPs) are anthropogenic materials generated during coal burning in coal-fired power plants and in case of lignite majority of these materials is disposed on land. CCPs contain various metals including Rare Earth Elements (REE). The purpose of this study was to assess if supercritical solvent extraction of CCPs, i.e. fly ash and bottom slag is effective to recover Rare Earth Elements. For that purpose two methods were compared: atmospheric and supercritical solvent extraction with the use of water and 10% HNO3. Result show that extraction of REE is unjustified when considering efficiency of solvent extraction process and obtained REE concentrations.

Mercury in Coals and Soils from Coal-Mining Regions

The article reviews data on the mercury concentrations in coals of the South of Kuznetsk basin (Kuzbas) in Kemerovo region in Russia and in the surrounding soils. The Hg concentrations in the soil (30 samples) and coal (207 samples) were determined by the atomic absorption using RA-915+ mercury analyzer with pyrolytic attachment. The comparison with previous research showed that over the last 25 years the mean Hg concentration in the soils decreased by a factor of 2.8. Based on the dominating contribution of the coal dust and coal combustion products into the total Hg influx in the environment, it is possible to predict increase of the Hg background level in the city and the surrounding area along with the coal production growth in the area without using modern effective dust suppression.

Identification of polycyclic aromatic hydrocarbons in roadside leaves (Ficus benghalensis) as a measure of air pollution in a semi arid region of northern, Indian city-A smart city

Abstract In this work, the semi-arid region of northern India was selected to observe the contamination levels, scattering pattern, seasonal distribution, the ratio of low and high molecular density carcinogenic PAHs (Polycyclic Aromatic Hydrocarbons) in the roadside plants (Ficus benghalensis). Total 48 samples [DAV College Jalandhar (inside city) as well as CT Group of Institutions Jalandhar (outside city)] were collected during the year 2017 (within four varying seasons). In order to understand the distribution pattern of PAHs we applied, Principal Component Analysis (PCA) and Cluster Analysis with Multivariate Linear Regression (MLR). The major resources of PAHs on roadside plants were the source of Petrogenic and Pyrogenic. Involvements of Coal Combustion Products (CCPs), automobiles exhaust emission and trickles of lubricate products (Petrogenic) were the key contributors with 36%, 36% and 28% using PCA/MLR, respectively. The mean concentration of total (low and high molecular weight) PAHs (Inside city) were 5.77 and 6.99 ng/m3 (1:1.44) whereas at outskirts of the city was 4.59 and 6.99 ng/m3 (1:1.93), respectively. Total PAHs mean concentration of PAHs (Inside city) was 105.81ng/m3, whereas in the outskirts of the city it was 97.34 ng/m, 3 respectively. The results of total PAHs concentrations (Inside city), indicated that the 4-ringed carcinogenic PAHs were at alarmingly surpassing concentrations (i.e., 30.35 ng/m3), whereas, at city outskirts 4, 5, and 6-ringed hydrocarbons were found in elevated concentration (i.e., 28.49, 25.59, and 23.46 ng/m3). The Two-tailed t-test, ring distribution pattern and toxic equivalency factor were applied for the statistics significance of results.

Distribution characteristics and migration patterns of hazardous trace elements in coal combustion products of power plants

Trace elements in coal produce migration and enrichment after combustion, the enrichment and release of hazardous trace elements will cause effective harmful to human health and the environment. In this paper, the distribution characteristics and occurrence state of hazardous trace elements in coal combustion products were studied by measuring the concentration of harmful trace elements in coal, slag, coarse ash, fine and fly ash. The experimental study of step-by-step chemical extraction was carried out, the migration and transformation model of trace elements in coal combustion process was investigated. The results show that the trace elements are easily enriched in fine particles of coal ash. The occurrence state of elements in combustion products has changed obviously, and the concentration of residual state has increased for example aluminosilicates. According to the enrichment index REI (Relative Enrichment Index), hazardous elements can be classified into three categories: (I) The elements left in both solid waste slag and fly ash are Cr, Mn and Ni (REI > 0.85); (II) The elements left in solid waste are Be, Co, Cu, Zn, Cd, Ba, Pb and U (0.1 < REI < 0.85); (III) The elements mainly volatilized into the atmosphere are few, only Sb (REI < 0.1).

Constituents of Household Air Pollution and Risk of Lung Cancer among Never-Smoking Women in Xuanwei and Fuyuan, China.

Background:Lung cancer rates among never-smoking women in Xuanwei and Fuyuan in China are among the highest in the world and have been attributed to the domestic use of smoky (bituminous) coal for heating and cooking. However, the key components of coal that drive lung cancer risk have not been identified.Objectives:We aimed to investigate the relationship between lifelong exposure to the constituents of smoky coal (and other fuel types) and lung cancer.Methods:Using a population-based case–control study of lung cancer among 1,015 never-smoking female cases and 485 controls, we examined the association between exposure to 43 household air pollutants and lung cancer. Pollutant predictions were derived from a comprehensive exposure assessment study, which included methylated polycyclic aromatic hydrocarbons (PAHs), which have never been directly evaluated in an epidemiological study of any cancer. Hierarchical clustering and penalized regression were applied in order to address high colinearity in exposure variables.Results:The strongest association with lung cancer was for a cluster of 25 PAHs [odds ratio (OR): 2.21; 95% confidence interval (CI): 1.67, 2.87 per 1 standard deviation (SD) change], within which 5-methylchrysene (5-MC), a mutagenic and carcinogenic PAH, had the highest individual observed OR (5.42; 95% CI: 0.94, 27.5). A positive association with nitrogen dioxide () was also observed (OR: 2.06; 95% CI: 1.19, 3.49). By contrast, neither benzo(a)pyrene (BaP) nor fine particulate matter with aerodynamic diameter () were associated with lung cancer in the multipollutant models.Conclusions:To our knowledge, this is the first study to comprehensively evaluate the association between lung cancer and household air pollution (HAP) constituents estimated over the entire life course. Given the global ubiquity of coal use domestically for indoor cooking and heating and commercially for electric power generation, our study suggests that more extensive monitoring of coal combustion products, including methylated PAHs, may be warranted to more accurately assess health risks and develop prevention strategies from this exposure. https://doi.org/10.1289/EHP4913

Incorporating bioaccessibility into health risk assessment of heavy metals in particulate matter originated from different sources of atmospheric pollution

Rapid industrialization and urbanization have resulted in widespread pollution of airborne particulate matter (PM) containing various heavy metals with adverse human-health effects. Health risk assessment of PM calls for accurate evaluation of the bioaccessibility, instead of the total content, of heavy metals in PM. Here, we demonstrated that the leachable fraction of particle-bound As, Pb, Cr, Mn, Cd, Cu, Ni and Zn in lung fluid within the typical retention duration of particles in human lungs varied drastically among particles originated from different air pollution sources, including coal combustion, biomass combustion, fugitive dust, road dust, construction dust, cement and soil. Moreover, bioaccessibility of heavy metals, particularly in biomass combustion, cement and soil particles, was strongly dependent on pollution sources, and the particulate Cu, Ni, Pb and Cd appeared to be the primary indicators of the source dependence of heavy metal bioaccessibility. Using total rather than bioaccessible concentrations of particle-bound heavy metals not only led to overestimation of the health risk of source particles, but more importantly, inaccurate identification of the high-risk pollution sources and the priority metal pollutants in the source particles. When considering bioaccessibility of particle-bound heavy metals examined in this study, coal combustion products exhibited the highest carcinogenic and noncarcinogenic risks among all source particles, whereas cement particles would be the source with highest risk based on total metal content. As and Mn appeared to be the main drivers for the noncarcinogenic risks of source particles, while As, Ni and Cr were the major contributors to the carcinogenic risks of source particles, significantly different from those based on total contents. This research underlines the importance of incorporating bioaccessibility into health risk indexes of frequently occurring particle-bound heavy metals from specific air pollution sources, which will facilitate risk-based assessment of source contribution and hence effective source regulation of airborne PM.

Mineralogical and Environmental Geochemistry of Coal Combustion Products from Shenhuo and Yihua Power Plants in Xinjiang Autonomous Region, Northwest China

The mineralogical and geochemical characteristics of feed coals and coal combustion products (CCPs) from the Shenhuo and Yihua Power Plants in Xinjiang Autonomous Region, were studied by means of proximate analysis, Power X-ray diffraction (XRD), scanning electron microscopy with Energy Dispersive X-ray analyzer (SEM-EDX), inductively coupled plasma atomic emission spectrometry (ICP-MS) and inductively coupled plasma mass spectrometry (ICP-AES). The environmental geochemistry of CCPs was evaluated by Al-normalized enrichment factor as well as European Standard EN-12457 leaching test. Two feed coals have the characteristics of low sulfur content, medium to high volatiles matter yields, medium moisture content, super low to medium ash yield, medium to high calorific value and low mineral content. The main crystalline facies in fly ash and slag are quartz and mullite, with a small amount of calcite, and some unburned carbon. Hematite, SrSO4 and barite also can be observed in fly ashes by SEM. Typical plerophere occurs in fine fly ash rather than the coarse fly ash. The concentration of most trace elements in CCPs falls within the lower concentration range of European fly ashes. With respect to the partitioning behavior of trace elements during coal combustion, S is highly volatile, and Mg, Na, Zn, B, Co, As, Nb, Zr, Cu and K also show certain volatility, which may to some extent emit to the atmosphere. Furthermore, leaching experiments show that leachable concentrations of most of the potentially toxic elements in CCPs are low, and the CCPs fall in the range between inert and nonhazardous landfill material regulated by the 2003/33/EC Decision.

Distribution of rare earth and selected trace elements in combustion products of Yerkovetskoe brown coal deposit (Amur Region, Russia)

Major, trace, rare-earth elements, and noble metal have been analyzed from the brown coal of the Amur region (Russian Federation) and coal combustion products to understand the provenance and depositional environment. It was discussed that weathering crusts of ore deposits and host rocks located in the mountain-folded frame of the Zeya–Bureya coal-bearing sedimentary basin were the main source of mineral substance and chemical elements in brown coals. The distribution of minerals and elements inside the forming coal seams was influenced by the type of vegetation incorporated into coal-forming peat mires bog by catastrophic floods along the existed hydraulic network, the physicochemical parameters of plant debris transformation during their conversion to coal, as well as the sorption properties of inclusions and interlayer of bitumen and humic acids in coal beds. An experimental technological complex was created to study the microelements transfer process in the dust–gas stream and the distribution of rare earth and trace elements separately in varieties of coal combustion products (slag, fly ash, dust-like part of the dust–gas flow, and technogenic cleaning water). The resulting combustion products of coal have been studied by inductively coupled plasma (ICP)-spectrometry methods (ICP-mass spectrometry and ICP-atomic emission spectroscopy). Sample preparation technique for analysis was improved to determine the elemental composition. It was established that more than 60% of trace and rare earth elements were concentrated in ash and sludge. Data on these elements’ concentration in the wash water sediment demonstrated a sufficiently high efficiency of the dust–gas flow cleaning. The use of a wet scrubber, of course, solves the problem of collecting the dust and gas flow cleaning from harmful and toxic elements of coal smoke, which should be a part of the technological chain of a coal combustion process in industrial boilers. Rare earth elements, scandium, and yttrium are considered economically valuable components in the coal combustion products of the Yerkovetskoe brown coal deposit in the Amur Region.

Shear Strength of Coal Combustion Product by Vane Shear

The objective of this study was to evaluate the shear strength of a coal combustion product (CCP) by using the vane shear test. A series of small-scale vane shear (SS-VS; diameter = 12.7 mm and height = 25.4 mm) and large-scale vane shear (LS-VS; diameter = 25 mm and height = 50 mm) laboratory tests were conducted. Undrained and drained strength envelopes were determined using consolidated undrained triaxial compression tests, and drained strength was checked via consolidated drained direct shear. In addition, effects of (1) rate of vane rotation, (2) time delay between vane insertion and beginning rotation, and (3) elapsed time under the final vertical effective stress before shear were evaluated via SS-VS. Vane shear strength results were represented in terms of peak shear strength and the initial horizontal effective stress acting on the vertical-oriented failure surface during rotational shear. Both SS-VS and LS-VS yielded shear strengths that plotted between the drained and undrained triaxial strength envelopes. Shear strength of CCP increased with increasing time under load, which was potentially attributed to diagenesis. Peak shear strength in SS-VS was reached after approximately 72 hours of elapsed time under constant vertical effective stress. Peak shear strength in SS-VS and LS-VS compared favorably to the drained strength measured via direct shear testing.

Shear Strength of Coal Combustion Product by Vane Shear

The objective of this study was to evaluate the shear strength of a coal combustion product (CCP) by using the vane shear test. A series of small-scale vane shear (SS-VS; diameter = 12.7 mm and height = 25.4 mm) and large-scale vane shear (LS-VS; diameter = 25 mm and height = 50 mm) laboratory tests were conducted. Undrained and drained strength envelopes were determined using consolidated undrained triaxial compression tests, and drained strength was checked via consolidated drained direct shear. In addition, effects of (1) rate of vane rotation, (2) time delay between vane insertion and beginning rotation, and (3) elapsed time under the final vertical effective stress before shear were evaluated via SS-VS. Vane shear strength results were represented in terms of peak shear strength and the initial horizontal effective stress acting on the vertical-oriented failure surface during rotational shear. Both SS-VS and LS-VS yielded shear strengths that plotted between the drained and undrained triaxial strength envelopes. Shear strength of CCP increased with increasing time under load, which was potentially attributed to diagenesis. Peak shear strength in SS-VS was reached after approximately 72 hours of elapsed time under constant vertical effective stress. Peak shear strength in SS-VS and LS-VS compared favorably to the drained strength measured via direct shear testing. © 2019 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved.