Ash Fraction Research Articles

Size and density separation for concentrating critical elements in ash fractions

ABSTRACT Coal and lignite ash are emerging as significant sources for extracting rare earth elements (REEs) and critical minerals. Despite lower concentrations of critical elements in ashes, their preconcentration is crucial for enhancing extraction efficiency and reducing energy consumption. Additionally, the simultaneous extraction of base metals could render combustion residue a more appealing raw material alongside the critical elements. Lignite fly ash samples from Neyveli, India, were analyzed using physical separation methods to preconcentrate critical elements. The total rare earth element (REE) content, including Y (REY, 1057 mg/kg) and Sc (REY-Sc, 1086 mg/kg) and the outlook coefficient (1.35), exceeded the cutoff value for economic extraction. Ga content was found to be comparable to that in bauxite residue, used for Ga extraction in India. REEs showed their greatest concentrations in the finer and lighter fractions. In contrast, TiO2, Fe2O3, Gd, Er, Lu, Ba, Cd, CO, Cu, Ga, Mn, Mo, Nb, Ni, and Pb tended to concentrate in the denser fractions. A flow diagram was presented that outlined the preconcentration process for base metals (Fe, Ti) and critical elements within designated ash fractions.

Size fraction characterisation of highly-calcareous and siliceous fly ashes

The properties of coal fly ash vary significantly depending on factors such as coal type, combustion conditions, and flue gas emission reduction methods. This study investigates the influence of particle size fractionation on the chemical composition, mineralogical structure, and thermal behaviour of two types of fly ash: high calcium ash derived from lignite (S1) and silica-rich ash from bituminous coal (S2). Dry aerodynamic separation was used to obtain distinct size fractions, which were then subjected to a comprehensive characterisation including X-ray fluorescence, X-ray diffraction, scanning electron microscopy, and thermal analysis. The results reveal notable differences between the S1 and S2 ashes and between their size fractions. The finer fractions (< 20 μm) of S1 showed an increased calcium and sulphur content, while the coarser fractions (> 100 μm) contained more silica and alumina. The S2 ash exhibited a higher overall silica content, with alkali metals concentrated in finer fractions. Thermal analysis demonstrated distinct behaviours for each type and fraction of ash. Fine fractions of S1 ash showed SO2 emission at elevated temperatures, while S2 ash exhibited greater CO2 gas emission. After thermal treatment, the recrystallisation of the glassy phase was observed for S1, while the S2 ashes were more prone to melting and agglomeration. The study highlights the potential for the customised utilisation of specific ash fractions in various applications, such as geopolymer synthesis, adsorbent materials, and refractory products. This comprehensive characterisation contributes to a better understanding of fly ash properties and their dependence on particle size, providing valuable insights to optimise fly ash utilisation in various industries. The findings suggest strategies for a more efficient use of fly ash resources, particularly relevant in the context of decreasing fly ash availability due to the phase-out of coal power plants.

On the influence of structural and chemical properties on the elastic modulus of woven bone under healing.

Woven bone, a heterogeneous and temporary tissue in bone regeneration, is remodeled by osteoblastic and osteoclastic activity and shaped by mechanical stress to restore healthy tissue properties. Characterizing this tissue at different length scales is crucial for developing micromechanical models that optimize mechanical parameters, thereby controlling regeneration and preventing non-unions. This study examines the temporal evolution of the mechanical properties of bone distraction callus using nanoindentation, ash analysis, micro-CT for trabecular microarchitecture, and Raman spectroscopy for mineral quality. It also establishes single- and two-parameter power laws based on experimental data to predict tissue-level and bulk mechanical properties. At the macro-scale, the tissue exhibited a considerable increase in bone fraction, controlled by the widening of trabeculae. The Raman mineral-to-matrix ratios increased to cortical levels during regeneration, but the local elastic modulus remained lower. During healing, the tissue underwent changes in ash fraction and in the percentages of Calcium and Phosphorus. Six statistically significant power laws were identified based on the ash fraction, bone fraction, and chemical and Raman parameters. The microarchitecture of woven bone plays a more significant role than its chemical composition in determining the apparent elastic modulus of the tissue. Raman parameters were demonstrated to provide more significant power laws correlations with the micro-scale elastic modulus than mineral content from ash analysis.

The influence of selected grain size fractions of coal fly ash on properties of clay-cement mortars used for the flood levees construction

This study examines the influence of different grain size fractions of coal fly ash on the properties of clay-cement mortars used in flood levee construction. Dry aerodynamic separation and mesh sieving were used to obtain ultrafine, fine, and medium fractions of high-calcium and silica fly ash. The experimental results reveal that the rheological properties of fresh mortars are significantly influenced by these fractions. High-calcium fly ash mortars exhibit high reactivity and rapid increase in viscosity, with finer fractions showing the highest reactivity. Silica ashes show increased reactivity in the later stages of suspension hardening. Their spherical shape contributes to reducing internal friction during flow in initial technological operations. Furthermore, the compressive strength of hardened mortars improves as the particle size decreases for both ashes, resulting in a dense and uniform microstructure. The separation and fractionation of fly ashes contribute to the obtaining of fractions that influence the parameters of clay-cement suspension application on different scales. The results show the potential benefits of ash separation, which can bring advantages in terms of economic viability, engineering performance, and ecological sustainability.

Chemical characterization of pellet stove ashes: Elemental fractionation of ashes results in volatile particles with high concentrations of cadmium and lead

Use of wood-based biomass for home heating has increased as a more sustainable and economical alternative to fossil fuel heating sources. However, concerns remain regarding particulate emissions and potential human health effects. Pellet stoves are very efficient combustion sources but still emit high particle numbers of nanoparticles into the environment and generate ash within the stove that could be an exposure source during cleaning. In this study we chemically characterize pellet ash collected from zones (upper and lower) from three stoves and determine the chemical composition of room air during cleaning events. Ash was acid digested using reverse aqua regia and microwave digestion and analyzed by ICP-MS. Indoor air was sampled using impingers before and during stove cleaning to assess ultrafine particulate release and exposure. Within the pellet stove different fractions of ash could be identified by color and macro-scale morphology. Ash fractions collected lower in the stove were predominantly calcium-based, 25 % by weight, and high in refractory trace elements, Fe, Cr, Mn and Ni. In contrast, ash collected higher in the stove was predominantly K and S based (25 and 5 % respectively) and had high concentrations of volatile elements Zn (0.4 %), Cd and Pb. Maximum Cd and Pb ash concentrations were 274 mg/kg and 807 mg/kg respectively corresponding to enrichment factors of 1581 and 870 compared to the respective pellets. Electron microscopy of the particles suggested that ash particles were agglomerates of smaller primary particles and EDS identified areas of high K and S concentration on the particles. Impinger studies of room air during cleaning showed an increase in K, S, Zn, Cd and Pb suggesting a mobilization of upper ash particles into room air upon stove cleaning.

Characterization of a fly ash-based hybrid well cement under different temperature curing conditions for natural gas hydrate drilling

This paper presents a study on the temperature effect (3°C, 10°C, and 50°C, in water bath) and activator effect on the characterization of a fly ash-based hybrid well cement, with a large fraction of fly ash (approximately 70 %), which has potential for natural gas hydrate drilling due to its low heat release. The mechanical strength, micro/nanostructure characteristics were investigated through various tests, including x-ray diffraction (XRD), thermogravimetry analysis (TGA-DTG), nuclear magnetic resonance (MAS NMR), and scanning electron microscope (SEM), to reveal the hydration mechanism of the fly ash-based hybrid well cement. The results indicate that the low curing temperatures (3°C, 10°C) inhibited both the hydration of the well cement and the pozzolanic reaction of fly ash in the cement system. However, the incorporation of solid Na2SO4 significantly contributed to the pozzolanic reaction during the hydration process by consuming more calcium hydroxide, promoting more ettringite formation and reducing the apparent activation energy of the blend cement (from 53.06 kJ·mol−1 to 41.23 kJ·mol−1), resulting in better compressive strength. MAS NMR results showed that the addition of solid Na2SO4 facilitated the substitution of Al with Si atoms, leading to the formation of more C-A-S-H and C-(N)-A-S-H gels in the system with a denser microstructure. Overall, the fly ash-based hybrid well cement can be developed as a cement system for natural gas hydrate drilling in the ocean. This cement not only exhibits low heat release but also shows improved strength development, with a 72-hour compressive strength of 8.05 MPa when cured at 10 °C.

Establishing a generalized model for accurate prediction of higher heating values of substances with large ash fractions

The higher heating value (HHV) of biomass is a crucial property for design calculations and numerical simulations in bioenergy utilization. However, existing models for HHV prediction faced challenges in terms of predictive accuracy and generalization capability across various solid waste types, especially for those with high ash content. This work proposed a novel HHV prediction model based on its reduction degree (DR) and ash content (Cash). First, ultimate analysis of biomass was applied to establish the calculation method of DR; then, the correlation between DR, Cash, and HHV was analyzed using the Pearson Correlation Coefficient; subsequently, the HHV = f (DR, Cash) model was developed using regression analysis. Furthermore, the accuracy was compared to previous literature in terms of correlation coefficient (R2), root mean square error (RMSE), and mean absolute error (MAE). Results revealed that this model provided attractive accuracy with R2 = 0.854, RMSE = 0.900, and MAE = 0.773 within a wide range of ash content from 0 to 83.32 wt%. Even higher accuracy was achieved with this model in predicting the HHV of coal, biochar, and bio-oil, with R2 of 0.961, 0.989, and 0.939, respectively. Conclusively, this work proposed the use of DR for HHV estimation, which was not only a simple and accurate approach but also widely applicable to various fuels.

Municipal sludge-based low-carbon phase-change composite towards energy storage: Fabrication and investigation

The integration of municipal sludge with phase change materials for composite energy storage material fabrication benefits to sludge significant reduction and recycling, heavy metal fixation, and minimizing environmental pollution. This groundbreaking work proposed municipal sludge-derived phase-change composites utilizing potassium nitrate as phase change material to produce cost-effective, low-carbon thermal energy storage materials. Five samples with varying mass fractions of municipal sludge incineration ash and potassium nitrate were prepared through a cold-compression & hot-sintering process and then thermal properties, microscopic structure, mechanical strength, and chemical compatibility between components was investigated extensively to explore the feasibility of municipal sludge recycling for composite energy storage material fabrication. The results revealed successful encapsulation of heavy metals within the phase change composites, and the composite with a 50:50 ratio of ash to potassium nitrate exhibited superior overall performance, which boasts a thermal energy storage capacity of 330.34 J/g with temperature rising from 100 up to 380 °C, a peak thermal conductivity of 1.04 W/(m·K), remarkable mechanical strength of 153.78 MPa, and excellent thermal stability. In addition, the components of the municipal sludge incineration ash and potassium nitrate displayed exceptional chemical compatibility. This novel phase change composite holds significant potential for engineering application compared to traditional alternatives.

Thermal Studies of Fractionated Lignite and Brown Coal Fly Ashes.

Coal fly ash (CFA), a by-product of coal combustion, is a valuable raw material for various applications. However, the heterogeneous nature of the composition and properties of CFA provides challenges to its effective usage and utilisation. This study investigates the thermal behaviour of the fly ashes of lignite (FA1) and brown coal (FA2) and their fractions obtained by dry aerodynamic separation. Thermal analysis techniques, including thermogravimetry (TG), differential scanning calorimetry (DSC), and evolved gas analysis (EGA), were used to characterise the behaviour of the fly ash fractions while heating up to 1250 °C. The results reveal distinct differences in the thermal behaviour between ash types and among their different size fractions. For the FA1 ashes, the concentration of calcium-rich compounds and the level of recrystallisation at 950 °C increased with the decrease in particle size. The most abundant detected newly formed minerals were anhydrite, gehlenite, and anorthite, while coarser fractions were rich in quartz and mullite. For the FA2 ashes, the temperature of the onset of melting and agglomeration decreased with decreasing particle size and was already observed at 995 °C. Coarser fractions mostly remain unchanged, with a slight increase in quartz, mullite, and hematite content. Recrystallisation takes place in less extension compared to the FA1 ashes. The findings demonstrate that the aerodynamic separation of fly ashes into different size fractions can produce materials with varied thermal properties and reactivity, which can be used for specific applications. This study highlights the importance of thermal analysis in characterising fly ash properties and understanding their potential for utilisation in various applications involving thermal treatment or exposure to high-temperature conditions. Further research on advanced separation techniques and the in-depth characterisation of fly ash fractions is necessary to obtain materials with desired thermal properties and identify their most beneficial applications.

The rheological characteristics of the dough for semi-finished biscuits with the addition of crickets flour

The article proposes to study the influence of new protein-containing raw materials, namely cricket flour (CF) Acheta domesticus on the quality of whipped flour semi-finished product (WFP) research methods. The study used generally accepted methods for determining the rheological properties of the dough: the dependence of viscosity on shear stress, temperature, and rate of deformation of the dough, as well as the elasticity of finished products and physicochemical properties of the finished semi-finished product. The mass fraction of moisture was determined by drying to constant weight. The mass fraction of ash not dissolved in 10% hydrochloric acid in absolute dry matter was determined using the dry method in a muffle furnace. The mass fraction of protein was determined by the Kjeldahl method. Alkalinity was determined by the titrometric method. The mass fraction of total sugar was determined by the iodometric method. During the manufacture of WFP, cricket flour was added to 5.0-15.0%. The results of rheological parameters showed that adding CF to the dough in an amount of 15.0% significantly affected the viscosity and plasticity of the dough, which led to a decrease in volume and porosity in the finished semi-finished product. According to physicochemical parameters, it was found that with increased BC concentration, the mass fraction of protein increases (from 4.4% in conventional WFP to 62.06% with the addition of CF in the amount of 10.0%). At the same time, the mass fraction of total sugar decreases. The mass fraction of moisture in the finished semi-finished product also changes. The resiliency and elasticity of the finished products were determined by the laboratory method using the "Labor" penetrometer. According to the results of studies of resiliency and elasticity of the finished product, it was determined that the semi-finished product with the addition of 15.0% cricket flour had the lowest indicators compared to the products with the addition of 5.0% and 10.0% cricket.

Study on the influence of coal on coal-to-ethylene glycol process considering the integration of reactor, distillation column, and heat exchanger network

The ethylene glycol (EG) process has low energy efficiency and high emissions. The raw coals purchased from different mines have different compositions and affect the reactor/column parameters and the integration of the heat exchanger network (HEN). An integrated reactor-distillation column-HEN model is built for optimizing the coal-to-ethylene glycol (CTEG) process considering the variation of raw coal. The particle swarm optimization (PSO) algorithm is used to solve this model and target the optimal raw coal for the CTEG process based on the interaction of MATLAB and Aspen Plus software. The influence of raw coal is obtained based on the sensitivity analysis performed for key reactor parameters and energy consumption. For the identified optimal raw coal, the mass fraction of carbon, hydrogen, oxygen, and ash are 84.02%, 6.80%, 1.00%, and 5.00%, respectively; the water added in the coal-water slurry is 62.15 t·h−1, and the water-gas ratio is 0.32, the corresponding energy consumption and the CO2 emission per unit product are 0.093 kgce⋅kmol−1 and 0.247 kgCO2⋅kmol−1, both decreased by 32.61%. The proposed method can be used to optimize the design and operation of the CTEG process and extended to optimize the other coal-based processes to achieve cleaner production.

The Influence of Recycled Coarse Aggregate Content on the Properties of High-Fly-Ash Self-Compacting Concrete

In Vietnam, solid waste from construction activities significantly impacts environmental pollution. Recycled concrete aggregate (RCA), derived from waste concrete, can serve as a coarse aggregate in concrete production. However, compared to natural aggregates, RCA exhibits distinct characteristics, including lower strength, higher water absorption, and an increased angular and rough surface. These properties may influence concrete’s workability, compressive strength, and durability. This research investigates the influence of RCA on the properties of High-Fly-Ash Self-Compacting Concrete (SCC). The study explores various replacement levels of natural coarse aggregate with RCA (0%, 50%, 75%, and 100%), alongside a 50% volume fraction of fly ash. Key concrete properties evaluated include workability, compressive strength, flexural strength, and chloride ion permeability. The findings reveal that using 100% RCA in combination with a high fly ash content (50%) produces SCC that meets workability requirements according to EFNARC standards. However, there are trade-offs: the compressive strength decreases by 4.61%, the flexural strength decreases by 3.1%, and chloride ion permeability increases by 57.57% compared to the control sample (using natural aggregates). Notably, the chloride ion permeability of SCC using 100% RCA falls into the category of low permeability. Doi: 10.28991/CEJ-SP2024-010-04 Full Text: PDF

Effective approach to assess higher heating value of biomass from ultimate and proximate analysis

AbstractFor proper design and operation of biomass‐based energy systems, it is important to determine the higher heating value (HHV) of biomass. In this paper, two machine learning (ML) approaches, namely extra trees (ET) and least squares support vector machine (LSSVM), are used to predict the value of HHV associated with biofuels. The data required for HHV calculation, including proximate and ultimate analyses datasets, were collected from the literature. The performances of these two ML approaches for predicting biomass HHV were then compared with other smart models available in the literature. Even though the available empirical models can predict the biomass HHV with acceptable precision, it was found that our proposed ML techniques have a superior performance based on the error analysis; the proposed approaches also consider all key biomass characteristics in the developed models. In addition, the ET model proved to be slightly more accurate compared to the LSSVM model. Additionally, the developed proximate‐based ET model showed better performance compared to the ultimate‐based ET model. The most influential parameters in the developed ET models for the proximate and ultimate approaches were determined to be ash fraction and carbon fraction, respectively. Finally, it was concluded that the smart modelling techniques can be utilized as a robust and reliable alternative predictive methodology to replace direct laboratory measurement of the biomass HHV.

Influence of complex enzyme drug and phytase on growth, digestibility and use of nutrients of wheat and soya compound feed and mineralization of the drumstick in broiler chickens

Plant feeds contain anti-nutritional factors. Thus, non-starchy polysaccharides are poorly digested and can serve as a barrier to enzyme access to nutrients. Phytate can form a complex with other divalent cations (Ca, Mn, Mg, Fe, Zn), amino acids. Phytate is the largest reserve of phosphorus in plants, but this compound cannot be effectively absorbed by poultry, which requires the inclusion of expensive inorganic sources of phosphorus in feed. The purpose of the research was to evaluate the possible effects of separate and combined inclusion of the complex enzyme drug Sunzyme (matrix as an ingredient) and the phytase-containing enzyme drug Sunface 5000 (matrix in nutritional value) on the digestibility and absorption of nutrients of wheat and soybean compound feed by broiler chickens. During the experiment, 204 day-old broiler chickens were divided according to the principle of analogues into 4 groups of 51 heads in each. The broiler chickens of the control group received compound feed without enzyme drugs, the 1st experimental group received compound feed with Sanzyme (matrix as an ingredient), the 2nd experimental group received compound feed with Sanzyme (matrix as an ingredient) and Sunface 5000 (matrix in nutritional value), the 3rd experimental group received compound feed with Sunface 5000 (matrix in nutritional value). Compound feeds were fed from one day to 42 days of age. In order to determine the digestibility of the main nutrients in compound feeds of broiler chickens aged 35–42 days, a physiological experiment was carried out based on the results of which a animal science analysis of the fed compound feeds and litter was carried out using generally accepted methods. When studying feed and litter, the mass fraction of dry matter, crude protein, crude fat, fiber, nitrogen-free extractives, ash, calcium and phosphorus were determined. It was found that compared with the control group broiler chickens received Sunzyme and Sunface 5000 had higher coefficients of digestibility and nutrient utilization of wheat and soybean compound feeds and as a result achieved a high average final live weight with low feed intake per unit of gain during the rearing period.

Speciation of antimony and vanadium in municipal solid waste incineration ashes analyzed by XANES spectroscopy

The use of ashes from municipal solid waste incineration as secondary building materials is an important pillar for the circular economy in Germany. However, leaching of potential toxic elements from these materials must be at environmentally acceptable levels. Normally, a three-month ageing period immobilizes most hazardous heavy metals, but antimony (Sb) and vanadium (V) showed previously unusual leaching. In order to clarify the mechanisms, we analyzed the Sb and V species in various bottom and fly ashes from municipal waste incineration by XANES spectroscopy. Antimony oxidizes from Sb(+ III) species used as flame retardants in plastics to Sb(+ V) compounds during waste incineration. However, owing to the similarity of different Sb(+ V) compound in the Sb K- and L-edge XANES spectra, it was not possible to accurately identify an exact Sb(+ V) species. Moreover, V is mainly present as oxidation state + V compound in the analyzed ashes. However, the coarse and magnetic fraction of the bottom ashes contain larger amounts of V(+ III) and V(+ IV) compounds which might enter the waste incineration from vanadium carbide containing steel tools. Thus, Sb and V could be critical potential toxic elements in secondary building materials and long-term monitoring of the release should be taken into account in the future.

Combustion Completeness and Sample Location Determine Wildfire Ash Leachate Chemistry

AbstractUnderstanding past fire regimes and how they vary with climate, human activity, and vegetation patterns is fundamental to the mitigation and management of changing fire regimes as anthropogenic climate change progresses. Ash‐derived trace elements and pyrogenic biomarkers from speleothems have recently been shown to record past fire activity in speleothems from both Australia and North America. This calls for an empirical study of ash geochemistry to aid the interpretation of speleothem palaeofire proxy records. Here we present analyses of leached ashes collected following fires in southwest and southeast Australia. We include a suite of inorganic elemental data from the water‐soluble fraction of ash as well as a selection of organic analytes (pyrogenic lipid biomarkers). We also present elemental data from leachates of soils collected from sites in southwest Australia. We demonstrate that the water‐soluble fraction of ash differs from the water‐soluble fraction of soils, with trace and minor element concentrations in ash leachates varying with combustion completeness (burn severity) and sample location. Changes in some lipid biomarker concentrations extracted from ashes may reflect burn severity. Our results contribute to building a process‐based understanding of how speleothem geochemistry may record fire frequency and severity, and suggest that more research is needed to understand the transport pathways for the inclusion of pyrogenic biomarkers in speleothems. Our results also demonstrate that potential contaminant loads from ashes are much higher than from soils, with implications for the management of karst catchments, which are a critical water resource.

Deep learning with TabNet: rapid coal ash content estimation via X-ray fluorescence

ABSTRACT As a paramount index of coal quality, the quick and accurate prediction of ash content bears substantial significance for the coal preparation plant. In this study, an innovative approach that integrates SHapley Additive exPlanations with a deep learning model Tabular Networks has been introduced, which efficiently predict the ash content by employing the compositional data obtained from rapid elemental analysis. Pictures of the relationship between elemental and ash content reveal a significant correlation. To further elucidate this relationship, Polynomial regression, Random Forest regression, and eXtreme Gradient Boosting are used as comparison prediction models to verify the accuracy of the deep learning model. The R2 for TabNet, Poly, XGBoost, and RFR are 0.9867, 0.9755, 0.9797, and 0.9714, respectively. The optimization is continued based on SHAP averages, and the best combination of elemental feature contributions obtained is used to continue the prediction of the experiments. The experimental results show that the TabNet model has better predictive performance than other models (RMSE, MAE, and R2 are 1.5126, 1.0953, and 0.9903). An examination and exploration of the contributions and roles of elements to the ash prediction model has been conducted. The case study presented in this paper illustrates that the interpreted deep learning model holds promising prospects for industrial ash fraction prediction.

Mechanical Properties and Failure Behavior of Epoxy Rubber Powder Composites Reinforced with Hollow Beads

In this paper, new epoxy resin/rubber powder/hollow beads three-phase composites were prepared by designing the incorporation of fly ash hollow beads with different mass fractions (5%, 10%, 15%, and 20%) as new reinforcing phases into epoxy resin/rubber powder two-phase composites with 5% mass fraction of carbon black rubber powder. Quasi-static compression tests were conducted at room temperature to test the compressive properties of the oxygen resin/rubber powder/hollow beads composites. Calculate the energy absorption properties and energy absorption efficiency of the composites from the compression curves. Fracture characteristics of compressed material specimens with microscopic morphology were observed by scanning electron microscopy. By systematically analyzing the effect of fly ash hollow beads content on the mechanical properties of epoxy resin/rubber powder/hollow beads three-phase composites, it was found that fly ash hollow beads as reinforcing materials can effectively improve the brittleness and yield strength of epoxy resin/rubber powder as well as the energy-absorbing properties and efficiency of the composites. The energy absorption properties of the epoxy resin/rubber powder/hollow beads composites increased and then decreased with the increase in the mass fraction of fly ash hollow beads. In the epoxy resin/rubber powder/hollow beads composites, the most significant performance was observed when the mass fraction of fly ash was 10%.

Estimating the bioaccessibility of atmospheric trace elements within the Athabasca bituminous sands region using the acid soluble ash fraction of Sphagnum moss

Total concentrations of trace elements in Sphagnum moss increase in concentration with distance toward bitumen mines and upgraders, but their solubility in the ash fraction after leaching in nitric acid is variable.

Comprehensive studies of coal tar pitch components

By methods of electron microscopy, adsorption porometry, NMR, IR- EPR spectroscopy, X-ray diffractometry, thermal analysis, chromatography-mass spectrometry the composition, structure and particle morphology of β- and α2-fraction powders of medium-temperature coal ash were investigated. The morphology and structure of coke residues depending on the heating temperature were investigated. Polyaromatic hydrocarbons in the composition of volatile products of coal ash thermolysis were found to be formed mainly by the decomposition of components of β-fraction. The results obtained are of interest from the point of view of the feasibility of using the isolated fractions of coal ash as precursors for the production of functional carbon materials.