Coal Combustion Products Research Articles

Determination of Traces Heavy Metals from Solid Residues Formed by Combustion of Lignite in Relation to Degree of Accessibility in Soil and Plants

The paper evaluates the presence and content of traces of heavy metals Hg, Pb, Ni, Cd (total forms) from coal and solid combustion products, the degree of transfer and accessibility in the area of influence of a lignite power plant. The content of toxic heavy metals in residues are characterized by RE Meiji [ 1 (Pb and Hg) and REMeij �1 (Ni and Cd) for the filter ash. Pb and Ni content in the soil exceeds normal values, and Pb exceeds and alert value for sensitive soils around the residue deposit (70.20 mg.Kg-1). The degree of accessibility of the metals in plants (TF), reported at the Khan reference value (0.5), indicates a significant bioaccumulation level for the metals: Cd (1.9) and Hg (0.6) inside the deposit; Cd (0.39) at the base of the deposit, Hg (0.8) in the area of the thermal power plant. The trace levels of heavy metals analyzed by GFAAS and CVAAS (Hg), indicates a moderate risk potential for food safety and quality of life in the studied area.

The gas heterogeneous flows cleaning technology from corona discharge field

A nanogold capture and extraction from combustion products of Kara-Keche coal, description the process: a coal preparation to experiments, nanogold introducing in its composition, temperature and time performance of combustion, device and function of experimental apparatus, gas-purification of the gas flow process and receiving combustion products (condensate, coke, ash, rags) is offerred.

The comparative analysis of heat transfer efficiency in the conditions of formation of ash deposits in the boiler furnaces, with taking into account the crystallization of slag during combustion of coal and water-coal fuel

The results of the numerical simulation of heat transfer from the combustion products of coal and coal-water fuels (CWF) to the internal environment. The mathematical simulation has been carried out on the sample of the pipe surfaces of the combustion chamber of the boiler unit. The change in the characteristics of heat transfer (change of thermochemical characteristics) in the conditions of formation of the ash deposits have been taken into account. According to the results of the numerical simulation, the comparative analysis of the efficiency of heat transfer has been carried out from the furnace environment to the inside pipe coolant (water, air, or water vapor) from the combustion of coal and coal-water fuels. It has been established that, in the initial period of the boiler unit operation during coal fuel combustion the efficiency of heat transfer from the combustion products of the internal environment is higher than when using CWF. The efficiency of heat transfer in CWF combustion conditions is more at large times (τ≥1.5 hours) of the boiler unit. A significant decrease in heat flux from the combustion products to the inside pipe coolant in the case of coal combustion compared to CWF has been found. It has been proved that this is due primarily to the fact that massive and strong ash deposits are formed during coal combustion.

Numerical simulation of submicron particles formation by condensation at coals burning

The thermodynamic analysis of the composition of the combustion products of 15 types of coals was carried out with consideration for the formation of potassium and sodium aluminosilicates and solid and liquid slag removal. Based on the results of the analysis, the approximating temperature dependences of the concentrations of condensed components (potassium and sodium sulfates) were obtained for the cases of two-phase and single-phase equilibriums; conclusions on the comparative influence of solid and liquid slag removal on the probability of the formation of submicron particles on the combustion of coals were made. The found dependences was make it possible to perform a numerical simulation of the bulk condensation of potassium and sodium sulfate vapors upon the cooling of coal combustion products in a process flow. The number concentration and size distribution of the formed particles have been determined. Agreement with experimental data on the fraction composition of particles has been reached at a reasonable value of a free parameter of the model.

The levels, variation characteristics, and sources of atmospheric non-methane hydrocarbon compounds during wintertime in Beijing, China

Abstract. Atmospheric non-methane hydrocarbon compounds (NMHCs) were measured at a sampling site in Beijing city from 15 December 2015 to 14 January 2016 to recognize their pollution levels, variation characteristics, and sources. We quantified 53 NMHCs, and the proportions of alkanes, alkenes, acetylene, and aromatics to the total NMHCs were 49.8–55.8, 21.5–24.7, 13.5–15.9, and 9.3–10.7 %, respectively. The variation trends in the NMHC concentrations were basically identical and exhibited remarkable fluctuation, which was mainly ascribed to the variation in meteorological conditions, especially wind speed. The diurnal variations in NMHCs on clear days exhibited two peaks during the morning and evening rush hours, whereas the rush hours' peaks diminished or even disappeared on the haze days, implying that the relative contribution of the vehicular emissions to atmospheric NMHCs depended on the pollution status. Two evident peaks of the propane ∕ propene ratios appeared in the early morning before sun rise and at noontime on clear days, whereas only one peak occurred in the afternoon during the haze days, which were attributed to the relatively fast reactions of propene with OH, NO3, and O3. Based on the chemical kinetic equations, the daytime OH concentrations were calculated to be in the range of 3. 47 × 105–1. 04 × 106 molecules cm−3 on clear days and 6. 42 × 105–2. 35 × 106 molecules cm−3 on haze days. The nighttime NO3 concentrations were calculated to be in the range of 2. 82 × 109–4. 86 × 109 molecules cm−3 on clear days. The correlation coefficients of typical hydrocarbon pairs (benzene ∕ toluene, o-xylene ∕ m,p-xylene, isopentane ∕ n-pentane, etc.) revealed that vehicular emissions and coal combustion were important sources for atmospheric NMHCs in Beijing during the wintertime. Five major emission sources for atmospheric NMHCs in Beijing during the wintertime were further identified by positive matrix factorization (PMF), including gasoline-related emissions (gasoline exhaust and evaporation), coal combustion, diesel exhaust, acetylene-related emissions, and consumer and household products. Coal combustion (probably domestic coal combustion) was found to make the greatest contribution (29.6–33.4 %) to atmospheric NMHCs during haze days.

Direct Conversion Fuel Cell of Urine in Animal Wastes and Its Condition Monitoring Sensors for Efficient Water Usage in Agriculture

Over one billion tons of agricultural (e.g. manure), municipal (e.g. biosolids), and industrial (e.g. coal combustion products) wastes with potential uses in agriculture are generated annually in the United States according to the National Agricultural Statistics Service [1]. An annual global production of about 40 billion liters of urine from farm animals is estimated. If urine by humans is added to that figure, 6.5 trillion liters are produced every year. Many of these materials are spread, sprayed or otherwise applied to agricultural land because of the benefits they provide. These benefits include: providing a nutrient source for crops; improving soil chemical, physical and biological properties; improving soil water storage and use; reducing movement of contaminants to water and air; and reducing production costs and energy use. However, improperly managed manure and other byproducts can pose a threat to soil, water and air quality, and to human and animal health. To prevent environmental pollution, it is important to treat them before release with minimal power consumption. For example, in activated sludge process, which is conventional wastewater treatment process, 1kWh/kg carbohydrate of energy is required [2]. If we can recover and use it for wastewater treatment, total power consumption for wastewater treatment will be reduced, and further, if the amount of recovered energy exceeds the amount of required energy for wastewater treatment, energy can be obtained from wastewater. In this project, we demonstrates very efficient and scalable direct urine fuel cells without the use of bacteria to mitigate animal waste, as well as generate electricity from wastewater. Unlike common microbial fuel cells that use electrons produced by bacterial metabolism [3], the proposed fuel cell is to harvest electrons directly from urea in urine by converting urea into H2O, CO2 and N2. Newly engineered electrodes and electrolytes were developed for efficient and rapid electricity generation. Since the mechanisms relating to direct conversion of urea have still not been understood entirely, our condition monitoring sensors will be re-engineered to measure chemical species generated by reactions between animal wastewater and fuel cells. The performance of the fuel cell is enhanced by developing unique sensing probes to monitor conditions of the reactors and animal wastes. Electrochemical sensors based on hierarchically nanostructured functional metal oxides. The measurement of gas and liquid environment of animal waste is demonstrated by addressing sensitivity, sensitivity and response time.

An Evaluation of the Environmental Safety and Geochemical Characteristics of Coal Combustion Products

In this study, the environmental safety and geochemical properties of Coal Combustion Products (CCPs) produced coal-fired power plants were investigated. Samples of CCPs were taken from all of the coal-fired power plants of Korea. Heavy metal concentration, Electrical Conductivity (EC), and pH measurements were conducted to evaluate the environmental stability and geochemical properties of the CCPs. X-ray fluorescence and X-ray diffraction analyses were performed and enrichment factors and an index of geo-accumulation were calculated to evaluate the levels of contamination in the CCPs. The pH value of the CCPs ranged from 7.6 to 9.3, slightly alkaline, and the EC ranged between 110 and 4,940 μS/cm. CCPs from anthracite coal had a lower silica-alumina ratio and lower proportions of CaO and MgO, and greater proportions of K2O, than CCPs from bituminous coal. The EF value of Fe, Ti, and P in some CCP samples classified moderate enrichment category, all other elements in the samples were classified in the deficiency to minimal enrichment category. Also, the heavy metal concentrations in all CCP samples were lower than the environmental standards, indicating that the CCPs satisfied environmental regulations.

The efficiency of heat transfer through the ash deposits on the heat exchange surfaces by burning coal and coal-water fuels

The results of the numerical simulation of heat transfer from the combustion products of coal and coal-water fuels (CWF) to the internal environment. The mathematical simulation has been carried out on the sample of the pipe surfaces of the combustion chamber of the boiler unit. The change in the characteristics of heat transfer (change of thermochemical characteristics) in the conditions of formation of the ash deposits have been taken into account. According to the results of the numerical simulation, the comparative analysis of the efficiency of heat transfer has been carried out from the furnace environment to the inside pipe coolant (water, air, or water vapor) from the combustion of coal and coal-water fuels. It has been established that, in the initial period of the boiler unit operation during coal fuel combustion the efficiency of heat transfer from the combustion products of the internal environment is higher than when using CWF. The efficiency of heat transfer in CWF combustion conditions is more at large times (t ≥ 1.5 h) of the boiler unit. According to the results the numerical simulation of the temperature distributions in the system “pipeline environment — pipe wall — a layer of ash — the products of combustion” have been obtained. A significant decrease in heat flux from the combustion products to the inside pipe coolant in the case of coal combustion compared to CWF has been found. It has been proved that this is due primarily to the fact that massive and strong ash deposits are formed during coal combustion.

Strength activity and microstructure of blended ultra-fine coal bottom ash-cement mortar

Replacing Portland cement with reutilized coal combustion products can have substantial benefits to the environment as well as infrastructure. In this study, a sub-bituminous coal bottom ash is re-utilized as a cement replacement. The bottom ash was pulverized using a high energy vibratory ball mill at two different milling times to achieve a particle fineness approximately two and three-times finer, respectively, than type I cement. The workability and final setting time were found to increase by 21% and 14%, respectively, and the highest strength activity was observed to be 120% at 90days. After normalization for particle fineness, age, and binder replacement using a general linear regression model, the data suggested the bottom ash blended cement mortar had 6.8% less strength activity than a comparative fly ash blended cement mortar. Blended bottom ash-cement paste samples were observed to have densely packed CSH product composed of relatively lower Ca/Si ratio (1.37) compared to that of fly ash blended cement paste (1.43) and the control (2.27). The CH content was also observed to be significantly lower in the bottom ash blended cement paste (19.1%) when compared against the control (27.2%) and fly ash blended paste (23.3%). Within the range of experimental conditions considered here, the results suggest that a coal bottom ash can be pulverized with a high energy ball mill to produce a re-utilizable pozzolan that, depending on the powder fineness, can significantly increase the strength activity, improve the microstructure of cement mortar, and increase the cement replacement tolerances without significant reduction to compressive strength activity.

57Fe Mössbauer spectroscopy investigations of iron phase composition in fluidized beds from the ELCHO power plant in Chorzów, Poland

Abstract The study investigates the physical and chemical properties of fly ash and bottom ash from a power plant ELCHO in Chorzów, Poland. Coal combustion products generated in the process of combustion in circulating fluidized beds (CFBs) are considerably different from fly and bottom ashes obtained from dust furnaces and multi-layer ones. The composition of the iron-bearing phase in the waste of circulating fluidized bed combustion was determined using Mössbauer spectroscopy and X-ray powder diffraction (XRD) methods.

Thermodynamic analysis of the formation of submicron particles on the combustion of coals

The thermodynamic analysis of the composition of the combustion products of 15 types of coals was carried out with consideration for the formation of potassium and sodium aluminosilicates and solid and liquid slag removal. Based on the results of the analysis, the approximating temperature dependences of the concentrations of condensed components (potassium and sodium sulfates) were obtained for the cases of two-phase and single-phase equilibriums; conclusions on the comparative influence of solid and liquid slag removal on the probability of the formation of submicron particles on the combustion of coals were made. The found dependences will make it possible to perform a numerical simulation of the bulk condensation of potassium and sodium sulfate vapors upon the cooling of coal combustion products in a process flow.

A review on the applications of coal combustion products in China

ABSTRACTOwing to the continuous high demand for energy, huge amounts of coals are consumed every year in China, giving rise to large volumes of coal combustion products (CCPs) from coal-fired power plants. Fly ash (FA), bottom ash (BA), boiler slag (BS), and flue gas desulphurization (FGD) gypsum are the primary CCPs generated. The disposal of these CCPs may occupy large areas of useful cultivated land, and cause serious environmental problems. However, these products might be also utilized as recoverable resources. Therefore, it is of economic and environmental significance to carry out research on the utilization of these CCPs. The present review first describes the physicochemical, mineralogical, and environmental geochemical properties of FA, slag, and FGD gypsum. Then the authors focus on the current and potential high value-added applications for these products in China. The utilization of FA for concrete and cement, soil amendment and fertilizer, in the ceramic industry, for catalysis, as adsorbents for the removal of flue gas, heavy metals, dyes and organic compounds, for zeolite and geopolymer synthesis, for recovery of valuable metals, and for recovery of unburned carbon and cenospheres, is discussed. The utilization of slag, such as reclamation of the burnable carbon, use in concrete, cement, and building materials, for roadway pavement and waste-water treatment, and for the production of acoustic barriers is reviewed as well. The current utilization of FGD gypsum includes use as a cement retarder, for the production of building plaster (β-hemihydrated gypsum) and calcium sulphate whiskers (α-hemihydrated gypsum), the production of fire-resistant panels, and use as a fertilizer and soil amendment agent. Furthermore, the possible influence of CCP properties on their utilization, and the advantages and disadvantages of various applications are discussed in this review. Finally, new directions for the future utilization prospects of CCPs in China are proposed.

The Effect of Cold Bending Process and Degradation at Boiler Conditions on the Properties of New Austenitic Creep Resistant Steel Super 304H for Boiler Super-Heaters Tubes

This paper is focused on evaluation of the plastic deformation effect, after the cold bending process for new austenitic material Super 304H designed for supercritical conditions. The aim of the project was to qualify the process of cold bending and then verify the properties of these bends in conditions approaching application. This paper presents the results of the plastic deformation effect on changes in the structure and mechanical properties at operating temperatures in corrosive environments coal combustion products and comparison to results before degradation. The tests were carried out on bends in two dimensions of tubes which are the most common sizes used in super-heaters for supercritical power plant boiler. The bends were produced by the method of cold bending on several bending radii in order to obtain information about the structure and behaviour of materials at various stages of deformation. To obtain reliable information tensile test, hardness test and metallographic examination were used on material from straight tubes of the bends and drawn parts before degradation and after degradation.

Leaching of trace elements from Pittsburgh coal mill rejects compared with coal combustion products from a coal-fired power plant in Ohio, USA

We investigated the leachability of elements from mill rejects from the high-sulfur, bituminous Upper Pennsylvanian Pittsburgh coal, using the synthetic groundwater leaching procedure (SGLP), long-term leaching (LTL), and the U.S. Environmental Protection Agency's (EPA's) toxicity characteristic leaching procedure (TCLP), and compared their leaching behavior with that of three coal combustion products (CCPs)—bottom ash, economizer fly ash, and fly ash—from the same coal. None of the environmentally hazardous Resource Conservation and Recovery Act of 1976 (RCRA) metals analyzed in the leachates from the mill rejects or the CCPs exceeded U.S. EPA toxicity characteristics (As, Ba, Cd, Cr, Hg, Pb, and Se). Most trace elements leached the least from mill rejects and bottom ash and leached the most from fly ash. The elements Ca, Co, Mg, Mn, and Sr, however, were more concentrated in mill reject leachates than CCP leachates. Most trace elements increased in concentration with increasing SGLP and LTL leaching duration, but As and V decreased in concentration with time in mill reject leachates, suggesting sorption or precipitation of these elements was occurring.

Stable isotope composition of mercury forms in flue gases from a typical coal-fired power plant, Inner Mongolia, northern China

Mercury forms emitted from coal combustion via air pollution control devices are speculated to carry different Hg isotope signatures. Yet, their Hg isotope composition is still not reported. Here, we present the first onsite Hg isotope data for gaseous elemental Hg (GEM) and gaseous oxidized Hg (GOM) of flue gases from a typical lignite-fired power plant (CFPP). Significant mass dependent fractionation (MDF) and insignificant mass independent fractionation (MIF) are observed between feed coal and coal combustion products. As compared to feed coal (δ202Hg=−2.04±0.25‰), bottom ash, GEM and GOM in flue gases before and after wet flue gas desulfurization system significantly enrich heavy Hg isotopes by 0.7–2.6‰ in δ202Hg, while fly ash, desulfurization gypsum and waste water show slight but insignificant enrichment of light Hg isotopes. GEM is significantly enriched heavy Hg isotopes compared to GOM and Hg in fly ash. Our observations verify the previous speculation on Hg isotope fractionation mechanism in CFPPs, and suggest a kinetically-controlled mass dependent Hg isotope fractionation during transformation of Hg forms in flue gases. Finally, our data are compared to Hg isotope compositions of atmospheric Hg pools, suggesting that coal combustion Hg emission is likely an important atmospheric Hg contributor.

A review on improvement of coal-fired power plants and environmental benefits of ash utilisation

Electricity generation in coal fired power plants produces large amount of residues. These materials are known as coal combustion products (CCPs) and can release pollutants to the environment. However, CCPs are environmentally and technically suitable for uses in many areas. The utilisation of CCPs in these areas helps to reduce the overall harmful effects of coal combustion for electricity generation by stabilising the environmentally toxic pollutants. The current paper reveals the possible usage areas of improved ash and presents the general approaches have been developed to obtain improved fly ash. Electrostatic separator with tribocharging technique has great potential for utilisation of coal ash. It significantly contributes to reduce fly ash disposal problems. In recent years, triboelectrostatic separators have increased significantly for the feasibility and success of the implementation of electrostatic separation. Studies carried out by various researchers on triboelectrostatic separation for utilisation of fly ash were also compiled in this article.

A review on improvement of coal-fired power plants and environmental benefits of ash utilisation

Electricity generation in coal fired power plants produces large amount of residues. These materials are known as coal combustion products (CCPs) and can release pollutants to the environment. However, CCPs are environmentally and technically suitable for uses in many areas. The utilisation of CCPs in these areas helps to reduce the overall harmful effects of coal combustion for electricity generation by stabilising the environmentally toxic pollutants. The current paper reveals the possible usage areas of improved ash and presents the general approaches have been developed to obtain improved fly ash. Electrostatic separator with tribocharging technique has great potential for utilisation of coal ash. It significantly contributes to reduce fly ash disposal problems. In recent years, triboelectrostatic separators have increased significantly for the feasibility and success of the implementation of electrostatic separation. Studies carried out by various researchers on triboelectrostatic separation for utilisation of fly ash were also compiled in this article.

Leaching Kinetics of As, Mo, and Se from Acidic Coal Fly Ash Samples

Annually, coal-fired electric power plants produce large volumes of potentially hazardous coal combustion products (CCPs) including fly ash. Since majority of the coal fly ash and other CCPs deposited in dry land fills or wet lagoons, they pose risk of contamination to local environment. In this study, we present results of leaching kinetics for As, Mo, and Se from three acidic fly ash samples collected from coal-fired power plants in the southeastern United States. This study shows that the leachate concentrations of As, Mo, and Se increase over time. Three kinetics equations, pseudo-second order, Elovich, and power-function, are able to adequately describe the experimental leaching kinetics data. Experimental leaching data and modeling results indicate that the rate limiting leaching of As, Mo, and Se is controlled by the diffusional process responsible for transferring these elements from interior to the surface of the particles as well as the dissolution of the fly ash particles. Therefore, it is important to adopt effective containment/treatment schemes to avoid potential and persistent dispersion of trace elements from ash disposal facilities to surrounding environment for a long time.

Stability analysis of a dike constructed of anthropogenic materials

Numerical analyses of stability are presented for a hypothetical dikes constructed of dredged materials and bottom ash, in varying proportions. The paper is related to the international research project DredgDikes, which focused on the use of anthropogenic materials in dikes construction and flood protection. The aim of this project was to investigate the possibility of using anthropogenic materials from rivers and sea dredging and coal combustion products in dikes construction. The influence of different proportions of ash and dredged materials on the stability of dike is discussed. Mechanical and hydraulic parameters of various dredged material-ash mixtures are based on the results of laboratory and field tests performed in DredgDikes project. Numerical calculations are carried out using geotechnical software Plaxis. Cementation phenomenon and its effect on the performance of ash and dredged material mixtures is discussed.

Interaction mechanism between coal combustion products and coke in raceway of blast furnaces

The interaction mechanism between the combustion products of pulverized coal injected and coke in the raceway of blast furnace was studied through thermodynamic calculation and experiments. The results indicated that additives significantly affected the melting property of coal ash in high temperature zone. Although the unburnt char, raw coal ash, and catalyzed coal ash failed to wet the coke surface, the wettability of the catalyzed coal ash on the coke was greater than that of the raw coal ash. Since the unburnt char had weak reaction with the coke surface, it showed little influence on the surface morphology of the coke. The interaction between the raw coal ash and the coke gave rise to the increase in the pore size on the coke surface. However, the raw coal ash only affected the coke surface and the entrances of the pores owing to its poor fluidity. After being melted, the catalyzed coal ash was expected to immerge into the inside part of the coke and then react with the coke, resulting in an expansion and increase of coke cavities. The raw coal ash and the unburnt char reduced the coke reactivity, while the catalyzed coal ash improved the coke reactivity. Thereinto, the coal ash containing Fe2O3 exhibited a larger influence on the reactivity than that containing CaO.