Coal Combustion Products Research Articles

Studying the Aerodynamics of the TPP-210A Boiler Furnace When It Is Shifted to Operate with Dry-Ash Removal and Vortex Fuel Combustion

To reduce the amount of nitrogen oxide emissions and achieve more reliable operation of the TPP-210A boiler, a process arrangement for firing Grade TR Kuznetsk coal that involves using straight-flow burners and shifting the boiler from slag-tap to dry-ash removal is developed. Owing to a large burner downward slope angle and special arrangement of burners and nozzles, four large vertical vortices rotating in opposite directions are produced in the furnace lower part, as a result of which the combustion products dwell for a longer period of time in the burning zone and more complete fuel combustion is achieved. For verifying the operability and efficiency of the proposed combustion arrangement, investigations on a boiler furnace physical model were carried out using a technique for visualizing fuel jets and secondary and tertiary overfire air jets. The fuel jet temperature boundaries in the course of jet propagation in the furnace model are also determined. The study results have shown that staged fuel combustion will be set up with using the proposed arrangement of burners and nozzles. In addition, large vertical vortices produced in the furnace lower part will help to achieve more efficient use of the dry bottom hopper heating surfaces, due to which lower coal combustion product temperature in the furnace upper part and smaller content of combustible products in fly ash will be obtained. Owing to low values of air excess factor at the pulverized coal burner outlet and gradual admission of air into the vortex zone through a few nozzles with intense inner recirculation of combustion products to the jet initial section, staged combustion of pulverized coal and low nitrogen oxide emissions will be secured. Owing to expansion of fuel jets, a rapid growth of mass in the fuel jet is achieved, which is obtained both due to ejection of the jet itself and due to forced admission of hot fuel gases from other jets. Investigations carried out on the physical model have confirmed that the proposed combustion arrangement features high efficiency and that a low content of nitrogen oxides in flue gases is obtained.

Coal combustion residues and their effects on trace element accumulation and health indices of eastern mud turtles (Kinosternon subrubrum)

Coal combustion is a major energy source in the US. The solid waste product of coal combustion, coal combustion residue (CCR), contains potentially toxic trace elements. Before 1980, the US primarily disposed of CCR in aquatic settling basins. Animals use these basins as habitat and can be exposed to CCR, potentially affecting their physiology. To investigate the effects of CCR on eastern mud turtles (Kinosternon subrubrum), we sampled 30 turtles exposed to CCRs and 17 unexposed turtles captured in 2015–2016 from the Savannah River Site (Aiken, SC, USA). For captured turtles, we (1) quantified accumulation of CCR in claw and blood samples, (2) used bacterial killing assays to assess influences of CCR on immune responses, (3) compared hemogregarine parasite loads, and (4) compared metabolic rates via flow-through respirometry between CCR-exposed and unexposed turtles when increased temperature was introduced as an added stressor. Turtles exposed to CCR accumulated CCR-associated trace elements, corroborating previous studies. Blood Se and Sr levels and claw As, Se, and Sr levels were significantly higher in turtles from contaminated sites. Average bacterial killing efficiency was not significantly different between groups. Neither prevalence nor average parasite load significantly differed between CCR-exposed and reference turtles, although parasite load increased with turtle size. Regardless of site, temperature had a significant impact on turtle metabolic rates; as temperature increased, turtle metabolic rates increased. The effect of temperature on turtle metabolic rates was less pronounced for CCR-exposed turtles, which resulted in CCR-exposed turtles having lower metabolic rates than reference turtles at 30 and 35 °C. Our results demonstrate that turtles accumulate CCR from their environment and that accumulation of CCR is associated with changes in turtle physiological functions when additional stressors are present.

Distribution of trace elements in coal and coal fly ash and their recovery with mineral processing practices: A review

Today coal is among the most important energy sources. In order to meet the world's energy demands, low-calorie lignite with a high ash content is generally used in the large capacity coal-fired thermal power plants. As a result of coal firing, wastes such as fly ash, slag, and flue gas are also produced. Subsequently, toxic trace elements within coal are transferred to wastes such as slag, fly ash, and flue gases. Large amounts of these, which are usually stored in collection ponds or stockpiles, are problematic in terms of environment. Although coal fly ash (CFA) has been utilized in construction and several other industries for decades, its current ratio of utilization is still quite limited. As an important fact, CFA also contains many valuable metals including germanium (Ge), gallium (Ga), vanadium (V), titanium (Ti), and aluminum (Al). In addtion, coal and CFA can be regarded as alternative sources of radioactive elements. Therefore, they also have a great potential in terms of the precious metals and trace elements they contain. In this study, the present literature on the distribution of trace elements in coal and coal ash during firing and ore preparation processes and their recovery possibilities with mineral processing practices are reviewed. While many research works on the subject clearly indicate that the large amounts of the ashes produced from firing of coal could be problematic in terms of environment, many studies and practices also show that coal combustion products also have a great potential in terms of the precious metals and trace elements.

Numerically Simulating the Parameters of Submicron Particles Generated in Coals Burning

Bulk condensation of substance vapors releasing from the mineral part of coals in burning them is regarded to be the possible mechanism through which environmentally dangerous submicron particles are generated. The possibility of certain toxic microelements contained in coals to condense on the surface of particles is an additional negative factor associated with the generation of particles during coal combustion. To set up a particle trapping process that would make it possible to decrease the emission of submicron particles into the atmosphere in burning coals, information on the parameters of condensation aerosols generated during the combustion is necessary. The required data, in particular about the concentration of particles and their distribution by sizes, can be obtained through numerically simulating the bulk condensation process. A condensation model describing the generation of submicron particles of potassium and sodium sulfate in burning coals is proposed. The proposed model is based on applying a combined approach (involving the use of thermodynamic and kinetic analysis) to describing the bulk condensation process in the coal combustion products. It is assumed that the generation of potassium and sodium aluminosilicates in the volume of a burning coal particles “freezes” after the particle burning process terminates and the particle temperature decreases; part of potassium and sodium in the composition of aluminosilicates is removed from the combustion products with slag and fly ash, and the other part that was not included in the aluminosilicates remains in the gaseous phase and forms sulfate condensation aerosol as the temperature decreases. The proposed model implemented by means of software was used to numerically simulate the bulk condensation of potassium sulfate vapors in the coal combustion products as they are cooled in the process path. Data on the concentration of the generated particles and on their distribution by sizes are obtained. The calculated and experimental data on the fractional composition of particles are compared with each other.

Occurrences of valuable trace elements in Iranian coals as potential coal combustion byproducts

ABSTRACT In Iran, coal as one of the primary energy resources mainly has just one customer (Iranian Steel Corporation); therefore, coal and production of its combustion have recently attracted much attention as promising alternative sources for valuable trace metals (VTM). Since there has been few principle exploration on occurrence modes of VTM for Iranian coal, this investigation assessed possible interactions between various coal conventional properties (proximate and ultimate analysis) and Y, Li, Ga, and V as VTM for Iranian coals. Statistical analyses indicated that on average, the contents of all these elements are higher than the general world coal ranges. Inter-correlation assessments showed that Ga and V in the samples are mainly associated with mineral matter (inorganic fracture of coal), e.g., mostly adsorbed by aluminosilicate (clay minerals) while Y and Li have a mixed organic and inorganic affinity. Strong interactions of Ga and V with inorganic fraction for samples with over 70% ash content released that host rocks of Iranian coal seams may also have the potential for the extraction of these two VTM. On the other hand, the mixed organic and inorganic affinity of Y and Li showed high possibility of their extraction from the coal combustion products. These results could be a critical key not only for geological and environmental information but also for developing possible procedures for their extraction.

Cadmium isotope fractionation during coal combustion: Insights from two U.S. coal-fired power plants

Coal combustion, one of the principal energy sources of electricity in the United States, produces over 100 million tons of coal combustion products (CCPs) per year in the U.S. The reuse and disposal of CCPs has the potential to release toxic trace elements, including cadmium (Cd), into the environment. In this study, we investigated CCPs, including bottom ash (BA), economizer fly ash (EFA), and fly ash (FA), as well as feed coal (FC) and pulverized coal (PC) collected from two U.S. coal-fired power plants in New Mexico and Ohio with different coal supplies. The New Mexico plant uses high volatile C bituminous, low-sulfur coals mined from the San Juan Basin (Cretaceous Fruitland Formation) and the Ohio plant uses high volatile A bituminous, high-sulfur central Appalachian Basin coals (Upper Pennsylvanian Monongahela Formation). Mineralogical and elemental analysis showed that these CCP samples consist of ∼70% amorphous Al-Si-rich glasses and ∼30% mineral phases of quartz (SiO2) and mullite (Ai6Si2O13). The Cd isotope compositions (δ114Cd, normalized to NIST Cd standard 3108) of FA and EFA samples (ranging from −0.51 to +0.47‰) are distinctively heavier than those of BA samples (−0.75 to −0.52‰) in both power plants. We interpret this Cd isotope difference as a result of Cd condensation from the gas phase during flue gas cooling, instead of evaporation of Cd phase during coal combustion. Cd condensation is the main process to generate the isotopically heavy Cd signatures that preferentially partition on the fine FA particles. We also investigated Cd isotope compositions in different leachate products from a series of batch-leaching experiments with these CCPs, using diluted acetic acid, hydroxyl ammonium chloride, hydrogen peroxide followed by ammonium acetate, and 5% nitric acid, as a possible means to identify CCP-released Cd in the environment. Unusually and significantly heavier Cd isotope compositions were observed in each leachate of FA samples (+1.10 to +7.09‰), which fall far outside from the range of Cd isotope ratios observed in natural soils and rocks, but less so for the EFA samples (−0.43 to +1.18‰). Such an observation is consistent with the interpretation that isotopically heavy Cd preferentially partitions on the fine FA particles after coal combustion and is readily to be released during these leaching experiments. This study demonstrates that high-temperature coal combustion can lead to a very large degree of fractionation of Cd isotopes that can be used as a unique tracer for identifying anthropogenic metal inputs in the environment. The major Cd isotope fractionation process occurs as the Cd gas phase condenses on fine FA particles during the flue gas cooling stage after coal combustion.

Methylated PAHs from Household Coal Use and Risk of Lung Cancer Among Never-Smoking Women in Xuanwei and Fuyuan, China

Background: Lung cancer rates for never-smoking women in Xuanwei and Fuyuan, China are among the highest in the world and have been attributed to use of “smoky” (bituminous) coal. However, the key carcinogenic components of coal that drive lung cancer risk here have not been identified. Methods: We conducted a population-based case-control study of lung cancer among 1015 never smoking female cases and 485 comparable controls and linked cancer risk through a multipollutant model to 43 household air pollution (HAP) chemicals and particulates measured in a comprehensive exposure study conducted in the same population. Exposures assessed included methylated polycyclic aromatic hydrocarbons (PAH), which have never been directly evaluated in an epidemiologic study of any cancer. Findings: The strongest detected risk of lung cancer was for 5-methylchrysene, a mutagenic and carcinogenic PAH. In contrast, neither benzo(a)pyrene, a standard marker of PAH exposure used in risk assessment, nor fine particulate matter (PM2.5), commonly used to evaluate health outcomes from outdoor air pollution, were associated with risk of lung cancer in multipollutant models. Interpretation: This is the first study to comprehensively evaluate lung cancer risk from HAP constituents estimated over the entire lifecourse. 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. Funding Statement: Funding provided by the intramural research program of the National Cancer Institute. Declaration of Interests: Authors have no conflicts of interest to declare. Ethical Approval Statement: The study protocol was approved by the institutional review boards of the National Cancer Institute (NCI) and China National Environmental Monitoring Center.

Simulation of the ceramic products composition using furnace-waste filler

Modern rates of construction stimulate ceramic-bricks factories to increase volume and variety of their production. At the same time, price of production should not exceed a certain limit. It can be reached by technological process optimization and with using waste of nearby industrial plants. Last time, brick factories try to use solid waste as filler. For regional production, it can be final product of coal combustion from Kazan CHP (Combined heat and power plant). The successful experience of foreign companies in furnace-waste recycling and the production of ceramic products from them, allow us to hope in acceptable results.The purpose of work was modeling composition of ceramic charge for Shelangovsk brick factory using Kazan TPP furnace-waste as filler. As experiment, to composition of clay gross products and working charge (75% clay + 15% sand + 10% buckwheat husks) of the Shelangovsk plant were added 10, 15, 20 and 25 percent of waste dopant. After molding of ceramic small brick, samples were fired at T = 980°C and then the end products were tested for strength.The results showed that addition 10, 15 and 20 percent of ash to working charge are consistently increases the strength of ceramic products in compression tests. According to the requirements of GOST (USSR Standard-Setting Authority) 530-95 for brick and ceramic stones, received products on compression match by brand not lower than M 100; by bend - not lower than M 300. The furnace-waste additive is not so effective with working natural clay. To determine specificity of reactions between waste and charge minerals was used X-ray analysis. Results are showed that ash and slag waste behaves as active fillers and forming new mineral phases.Thus, the use of ash and slag wastes of Kazan CHP as fillers for ceramic charge improves to physical and mechanical characteristics of wall bricks. At the same time, the ash-and-slag additive actively participates in mineral formation and increasing the amount of crystallization contacts in the resulting ceramic products.

Rare earth elements in superhigh-organic-sulfur Raša coal ash (Croatia)

The Raša coal from Istria belongs to a special type of superhigh-organic-sulfur coals, with organic sulfur content of 11%. This study encompasses culm and coal ashes from old landfills left behind after many decades of the Raša coal use with regards to their rare earth element geochemistry. Regarding the studied coal ashes, obtained results suggest a substantial variability in the content of rare earth elements and Y (REY) in coal combustion products generated from the Raša coal. Although samples of coal ash and culm of the Raša coal have REO (oxide of REY) content (up to 464 mg kg−1) below the level considered as the cut-off grade for beneficial recovery of these metals (1000 ppm, ash basis), they contain relatively high share of critical REY (>30%). The coutl values (outlook coefficient of REY ores; based on Seredin-Dai's criterion) range from 0.78 to 1.45 while Eu and Ce anomaly display slightly positive and negative values, respectively. With LaN/SmN ratios below unity, from 0.65 to 0.88, and LaN/LuN and GdN/LuN ratios ranging from 0.53 to 1.17 and from 0.80 to 1.41, respectively, they dominantly correspond to M-type of enrichment and only sporadically to H-type of enrichment.Previous studies attributed the formation of superhigh-organic-sulfur Raša coal to the seawater percolation. However, the geochemical data presented in this study suggest that the Raša coal-bearing strata, representing the Upper Paleocene lacustrine and brackish facies, were influenced by both the seawater and the hydrothermal solutions under conditions which led not only to sulfur enrichment but also to REY accumulation.From the economic standpoint and currently available data, Raša coal ash cannot be considered as the secondary raw material for rare earth elements, but its significantly variable composition and relatively high REO found in culm highlights the need for future studies of Raša coal and related combustion products.

Relationships between noble metals as potential coal combustion products and conventional coal properties

Increasing coal consumption has generated million tons of ash and caused various environmental issues. Exploring statistical relationships between concentrations of valuable metals in coal and other coal properties may have several benefits for their commercial extraction as byproducts. This investigation studied relationships between conventional coal concentrations and concentration of noble metals for a wide range (708 samples) of eastern Kentucky coal samples (EKCS) by statistical methods. The results indicate that there are significant positive Pearson correlations (r) > 0.90 among all noble metals (Au, Pt, Pd, Ru and Rh) except for Ag (r < 0.2). The results also showed that the noble metals (except Ag) are associated with the minerals of the coal and have high positive correlations with ash (and high negative correlations with the organic fraction). Modeling through the database demonstrated that the highest Au concentrations in the EKCS occur when Si is between 6000 and 8000 ppm and Fe is below 10000 ppm, and the highest Ag was observed when both Cu and Ni were over 40 ppm. Outcomes suggested that aluminosilicate minerals and pyrite are possibly the main host of noble metals (except Ag) in the EKCS whereas Ag might occur in various forms including organic association, mineral species, and as a native metal.

Compositional Data Analysis of Coal Combustion Products with an Application to a Wyoming Power Plant

A mathematically sound approach for summarizing chemical analyses of feed coal and all its combustion products (bottom ash, economizer fly ash, and fly ash) is presented. The nature of the data requires the application of compositional techniques when conducting statistical analysis, techniques that have not been applied before to the study of partitioning of elements between the coal that enters the boiler and the associated coal combustion products. A collection of descriptive and inferential compositional techniques was used to analyze the coal combustion products from a Wyoming power plant burning Paleocene Wyodak–Anderson coal. The significance of the fluctuation in ash composition is determined by using a Hotelling’s T-squared test and bootstrapping. Tree displays allow for visualization of the progressive effect of filters in removal of chemical species based on their geochemical composition. Results indicate that, in general, as the suspended combustion products entrained in the flue gases move closer to the stack, chemical species are removed from the combustion gas, starting with minerals associated with elements having the lowest volatility.

The implementation of Circular Economy Concept in the Polish Coal Combustion Products Sector – selected problems

The implementation of Circular Economy Concept in the Polish Coal Combustion Products Sector – selected problems

Ternary binder made of CFBC fly ash, conventional fly ash, and calcium hydroxide: Phase and strength evolution

Coal combustion products present a source of aluminosilicate materials for further utilization. The ternary binder studied here is such an example, consisting of circulating fluidized bed combustion (CFBC) fly ash, conventional fly ash and Ca(OH)2 activator. The paste yields a compressive strength of 32 MPa after 28 days of standard sealed curing. Volumetric evolution of crystalline and amorphous phases during hydration is quantified using XRD analysis, differential thermal gravimetry, porosimetry and electron microscopy. A micromechanical model is applied to interpret the evolution of compressive strength due to the growing proportions of C-S-H and ettringite in the system. This opens the way for further optimization and utilization of this ternary binder.

A random forest approach for predicting coal spontaneous combustion

The accurate prediction of coal temperature plays a vital role in preventing and controlling the spontaneous combustion of coal in coal mines. In this study, a large-scale 2-ton experimental furnace was constructed to implement an oxidation experiment by using a Dafosi coal sample. The aim was to simulate the spontaneous combustion of coal at low temperatures (<100 °C). A random forest (RF) approach based on the oxidation experiment was proposed to predict coal spontaneous combustion, which exhibited satisfactory results. Moreover, to verify the performance and effectiveness of the RF approach in a practical application, a long-term in-situ observation test was conducted in a fully mechanized caving mining face (the Dafosi Coal Mine), where the in-situ data were employed to establish the RF model. Methods such as back-propagation neural network (BPNN) and multiple linear regression (MLR) were also adopted and compared with the RF model. The results indicated that the MLR model had the least reliable predicted results, regardless of whether the model was based on the oxidation experiment data or the in-situ data. This demonstrated that linear regression methods are not ideal for determining the complicated relationship between the temperature and gaseous products of coal spontaneous combustion. The BPNN model exhibited the most reliable prediction results during the training stage; however, overfitting occurred in the training stage, and the predictive performance at the testing stage was poorer than that of the RF model. The RF model accurately predicted the temperature of coal spontaneous combustion when it was applied to the in-situ data, and almost no deviation existed in the predictive performance indicators between the training and testing stages. The modeling and application results suggested that the RF model, which possesses high precision, strong generalization ability, and sound practical performance is more suitable for the prediction of coal spontaneous combustion. This method can potentially be further applied as reliable approach for the assessment of intricate relationships through fuel and energy investigations.

Possibility of Coal Combustion Product Conditioning

This paper is focused on properties of materials known as green binders. They can be used to produce aluminium-siliceous concrete and binders known also as geopolymers. Comparing new ecological binders to ordinary cements we can see huge possibility of reducing amount of main greenhouse gas which is emitted to atmosphere by 3 to even 10 times depending of substrate type used to new green material production. Main ecological source of new materials obtaining possibility is to use already available products which are created in coal combustion and steel smelting process. Most of them are already used in many branches of industry. They are mostly civil engineering, chemistry or agriculture. Conducted research was based on less popular in civil engineering fly ash based on lignite combustion. Materials were examine in order to verify possibility of obtaining hardened mortars based of different factors connected with process of geopolymerization, which are temperature, amount of reaction reagent and time of heat treatment. After systematizing the matrices for the basic parameters affecting the strength of the hardened mortars, the influence of the fly ash treatment for increasing the strength was tested.

Hydraulic Conductivity of Compacted Soil Liners Permeated with Coal Combustion Product Leachates

AbstractTests were conducted on eight soils to determine how coal combustion product (CCP) leachates may affect the hydraulic conductivity of compacted soil liners (CSLs) used for CCP disposal faci...

Hydraulic Conductivity of Geosynthetic Clay Liners with Sodium Bentonite to Coal Combustion Product Leachates

AbstractExperiments were conducted to evaluate the hydraulic conductivity of geosynthetic clay liners (GCLs) containing granular sodium bentonite that were permeated with coal combustion product (C...

The technology of gold-containing concentrates recovery from the coal combustion products of the Yerkovetskoye brown coal deposit (the Amur Region, Russia)

The results of experimental research of the native gold distribution in the coal combustion products (CCP) obtained out of the brown coals of the Yerkovetskoye deposit combustion material in the experimental technological complex “Amur” (ETС “Amur”) are described in the article. The technology of the formation of slag, fly ash and products of wet cleaning of flue gases in the process of various combustion modes of coal combustion is examined. The possibility of the obtaining of enriched gold-containing concentrate by gravity and magnetic methods from the brown coal combustion products and extraction of native gold out of the concentrate is shown.

Influence of cement substitution by calcareous fly ash on the mechanical properties of polymer-cement composites

The aim of the presented research was to determine the influence of cement substitution with calcareous fly ash on the mechanical properties of polymer-cement composites. Coal combustion products such as calcareous fly ash have been already used in traditional cement composites as a part of cement and considered potential additions for concrete but its introduction into polymer-cement composites is still under preliminary investigation. The morphology of fly ash causes problems with its compatibility with polymer-cement binders but its insertion into those building materials is another way to utilize mineral combustion products that are cumbersome in storage and recycling. The influence of the mineral addition on polymer-cement composites containing 20% of polymer was especially taken into consideration. Mechanical properties of polymercement mortars modified with calcareous fly ash were tested after 28 and 90 days of curing. As a part of preliminary study, activity index of mineral addition was determined. Polymer-cement composites containing calcareous fly ash were characterized by higher flexural and tensile strength comparing to standardized mortar, even for the mortars containing 40% of mineral addition. The negative effect of the polymer-cement composites modification with calcareous fly ash was especially observed on the compressive strength of this composites.

State of the art in the field of emission reduction of sulphur dioxide produced during coal combustion

ABSTRACTThe need for clean coal technologies to reduce the adverse environmental impact of coal combustion products has been grounded. The article deals with information concerning present and future technologies, directed towards the struggle against air pollution by SO2, produced during coal combustion. Their classification and critical rating from economical and technological points of views (including those developed by authors) have been performed. The method of comparing the effectiveness of flue gas desulphurization (FGD) processes and technologies of coal preventive desulphurization were offered.