Coals Of Different Rank Research Articles

Coal-based graphene derived from different coal ranks: exceptional sodium storage performance in sodium-ion batteries.

Coal is a premium carbon material precursor as anode materials for sodium-ion batteries (SIBs). Additionally, developing anode materials with large capacity and rapid charging performance is essential for the advancement of SIBs. Consequently, in this work, coal-based reduced graphene oxide (CrGO) was prepared as an anode materials for SIBs by a modified Hummers-high temperature thermal reduction method with different ranks of coal (coal-based graphite, CG) as a precursor. The CG prepared from higher-rank coal exhibits a higher degree of graphitization, and its graphene layers are easier to exfoliate. The unique microstructure of CrGO provides stability during the sodium storage process and exhibits fast ion capacitive adsorption behavior, enhancing reaction kinetics. CrGO, with an initial reversible capacity of up to 331 mA h g-1 at a current density of 0.03 A g-1, achieves a specific capacity of 75 mA h g-1, even at a high current density of 10 A g-1. Notably, CrGO also maintains a good specific capacity of 123 mA h g-1 after 1000 cycles at a current density of 1 A g-1, with a capacity retention rate of 91.8%. This study highlights the potential for using coal-derived materials in the development of high-performance anode materials for SIBs, promoting the green and high-value utilization of coal.

Spectral signatures of solvent-extracted macromolecules in Indian coals of different rank: Insights from fluorescence excitation-emission matrix

Solvent-extracted fractions of six Indian coal samples of different ranks were investigated using multiple geochemical, petrological and spectroscopic proxies and an attempt was made to indicate possible fingerprint regions for different polycyclic aromatic hydrocarbons (PAH) with the help of excitation-emission matrix (EEM). In this study, for the very first time, the influence of rank and maturation of organic matter in the characterisation of coal solvent-extracts from Indian coals were perceived from the viewpoint of fluorescence EEM. Vitrinite reflectance (VRo) values were used to determine the general ranks of the original coal samples viz. lignite, subbituminous, bituminous and anthracite. Different fluorescence peak regions corresponding to different fused aromatic ring (FAR) systems were delineated using the EEM and their indicative depositional environments could be inferred. Our observations indicate that solvent-extracted fractions of low rank coals comprise of a larger number of shorter carbon chains compared to the other samples. For the low rank coal samples, the solvent-extracts show a strong humic influence and the presence of smaller PAH rings while for the medium rank coals, the extracted fractions tend to show a more bimodal distribution of PAHs, possibly comprising of different sized PAHs. Higher fluorescence sensitivity and quick response of smaller PAHs impart a singular centralised region in the EEM for the low rank coal samples while interference in the fluorescence of differently sized PAHs indicate a multimodal distribution of the fluorophores in the medium rank coals. The high rank coal used in this study shows a bimodal distribution with very low intensity of the peaks, indicating the low abundance of extractable macromolecules, possibly as a result of deformation.

Pyrolysis kinetic analysis and model constructions of different ranks of coal and validation by GA–BP neural networks

In the current steel industry, environmental pressures are mounting. If the reducing gases generated from coal pyrolysis can be utilized for reducing iron ore, the goal of low-carbon production with controllable costs can be achieved. However, the release of volatile content in coal has a significant impact on the pyrolysis process and final products. Therefore, in this study, the pyrolysis characteristics and gaseous products of four types of coal with different volatile matter content was investigated by thermogravimetry-mass spectrometry (TG-MS) technology. The results showed that coals with higher volatile matter content demonstrated stronger reactivity during pyrolysis. As the volatile matter content in coal increased, the starting temperature for releasing the reducing gases decreased, leading to a significant increase in the released gas volume. In addition, the three kinetic factors were calculated by isoconversional method, distribution of the activation energy model (DAEM) and Coats-Redfern (CR) method respectively, and the pyrolysis reaction mechanism function suitable for all coal types was reconstructed based on common solid reaction models. Finally, a predictive model based on a GA-improved back-propagation neural network (BPNN) was developed, which useing 21 input parameters to predict the TG curves, activation energy (E), lnA and mechanism function (fα) and achieving R2 values above 0.95. This study contributes to a comprehensive understanding of the pyrolysis mechanism of coals with different volatile matter content, providing scientific guidance for effective utilization.

The Occurrence and Distribution of Nitrogen in Coal of Different Ranks and Densities

Nitrogen is one of the significant pollutants emitted from coal combustion, and the study of its distribution and occurrence is very important for the efficient and clean utilization of coal resources. Four kinds of coal with different metamorphic ranks from major coal-producing provinces of China were studied. A gravity float-and-sink experiment was applied to obtain coal samples with different densities from Shanxi Province. The microscope optical method, Kjeldahl method, and X-ray photoelectron spectroscopy (XPS) were used to assess the occurrence, form, and distribution of nitrogen in the coal. The results show that the nitrogen content was about 0.47%–1.85%, and the maximum nitrogen content was positively correlated with the rank of coal, but the difference was not obvious. In the low-rank coal, the nitrogen content was mainly related to vitrinite and inertinite, while in the middle–high-rank coal, the nitrogen content was mainly related to inertinite and minerals. Pyrrolic (N-5) and pyridinic (N-6) were the main forms of nitrogen in the low-rank coal. The contents of N-6 and N-5 decreased with increases in the coal density, but the contents of quaternary N-Q1 and quaternary N-Q2 increased. N-Q2 mainly comes from fixed ammonia nitrogen in minerals, and vitrinite and liptinite contain more N-6 and less N-Q1 than inertinite. This research provides valuable evaluation guidance for the efficient utilization of coal.

PH-responsive HMDS terminated m-Cresol for inhibiting the spontaneous combustion in different-rank coals

In this study, pH responsiveness of 1, 1, 1, 3, 3, 3-hexamethyldisilazane terminated m-Cresol (HTMC) in different-rank coals was investigated, and its inhibition performance regarding the spontaneous combustion of coal was explored. First, color changes in the deprotection reaction of HTMC under different acidic conditions were analyzed. Then, surface microstructures of these coals and pH values of their filtrates were tested. Subsequently, experiments were performed on different coal samples for grasping their low-temperature oxidation characteristics, weight loss rates, pore characteristics, and free radical variations. The experimental results show that HTMC can effectively protect phenolic hydroxyl groups in inhibitors, and the acidity of coal can promote the conversion rate of its deprotection reaction. For instance, in XAM coal (pH ≈ 6), sufficient H+ stimulates HTMC to release massive m-Cresol which contains highly reactive phenolic hydroxyl, thereby effectively suppressing increases of the concentration and type of free radicals. The crossing point temperature (177.2 °C) and inhibition rate at 110 °C (75.9 %) of the HTMC-inhibited XAM sample are 33.1 °C and 17.9 % higher than those of the m-Cresol-inhibited one, respectively. This study confirms the applicability of pH-responsive HTMC to different-rank coals and may lay a theoretical foundation for the design of efficient reactive inhibitors.

The structure of appalachian coal: Experiments and Ab initio modeling

This study focuses on the construction of small-scale atomistic representations of three Appalachian coals of different ranks– high volatile bituminous, low volatile bituminous, and semi-anthracite. Ultimate, proximate, 13C NMR, FTIR, and XPS data were used to infer 2D and construct multiple 3D molecular models for each coal. A new simulation strategy for structure optimization, termed “Sectioned Optimization”, is introduced to ensure energetically stable configurations of the 3D coal models. Density functional methods are applied to the models, improving their quality, and giving insight into the limitations of empirical simulations in this complex system. The structural models were validated ex post facto using a density functional code, VASP. We describe the distribution of local atomic environments in the models to emphasize the significant structural distinctions between the three coal ranks. We also report the first ab initio vibrational density of states calculations for coal and compare it to FTIR and Inelastic Neutron Scattering experiments and identify vibrational modes using ab initio calculations. We also provide animations of the vibrational normal modes in coal that are consistent with FTIR band assignments. We show that the specific heat capacity compares favorably with experimental data.

Determining the pore structure and fluid characteristics of different ranks of coal using nuclear magnetic resonance

The microstructure of coal reservoirs and their fluid-endowment characteristics are important indicators for evaluating coalbed methane during mining. This study aimed to investigate the influence mechanism of the nanopore structure of different coal ranks on the fluid distribution characteristics. Low-field nuclear magnetic resonance (NMR), centrifugal force, and heat treatment tests were conducted. The results indicated that as the degree of coal metamorphism increases, micro-transition pores increase significantly, mesopores–macropores decrease, and the nonhomogeneity of the pores increases. The optimum centrifugal forces for low-, middle-, and high-rank coals were 1.68, 1.08, and 1.08 MPa, respectively. The corresponding mean T2C1 (first T2 cutoff) values were measured as 8.01, 1.61, and 5.09 ms, respectively, while the mean T2C2 (second T2 cutoff) values were 0.23, 0.26, and 1.25 ms, respectively. Pore sizes less than 11.6 nm indicate unrecoverable fluid, those higher than 88 nm indicate free fluid, and the rest (11.6–88 nm) indicate capillary bound fluid. As the degree of coal metamorphism increases, free fluid saturation decreases, capillary bound fluid saturation increases and then decreases, and unrecoverable fluid saturation increases.

Water saturation characteristics of coal of different ranks and its effect on capillary pressure

AbstractSaturation characteristics of water and capillary pressure are important for hydrofracturing or water flooding, which is widely adopted in dust suppression, methane displacement, and gas and coal outburst elimination. In this paper, we have studied the water saturation characteristics of coal samples with different coal ranks and their effect on capillary pressure. It was found that the isothermal adsorption of water vapor from coal samples can be divided into three processes: monolayer adsorption, multilayer adsorption, and capillary condensation. The dent isothermal adsorption model can well describe water vapor adsorption of coal samples, indicating water molecules were first adsorbed on the first‐order adsorption site of pore surfaces at low relative humidity and then on the second‐order adsorption site with increasing relative humidity. An obvious hysteresis occurred in the process of water imbibition and drainage. A capillary pressure of ~325 MPa or even larger was required to displace the water from the coal. Besides, micro‐ and mesopores play a more important role in capillary pressure. The capillary pressure of coal samples was positively correlated with wettability at lower water saturation, but it is not significant at higher capillary pressures. Therefore, the article's results provide a new direction for solving the water‐locking effect in coal seams.

Impact of N-Methyl-2-pyrrolidone Erosion on Surface Functional Groups and Pore Evolution in Coals of Different Ranks.

In low-permeability coal reservoirs, utilizing the organic solvent N-methyl-2-pyrrolidone (NMP) has emerged as an effective approach to improving the coal pore structure and enhancing coalbed methane productivity. However, the exact mechanisms of how solvent erosion alters functional groups and develops pores remain incompletely understood. This study utilized Fourier transform infrared spectroscopy and low-field nuclear magnetic resonance to assess the impact of NMP on the functional groups and pore structures of lignite, bituminous coal, and anthracite. The results indicate that a 6 h treatment with NMP led to an increased proportion of oxygen-containing functional groups in all coal samples, accompanied by a decrease in hydroxyls and aliphatic hydrocarbons. The aromaticity of the coal samples was enhanced to varying degrees, most notably for lignite. In terms of pore modification, the porosity of lignite and bituminous coal increased by 84.82 and 43.56%, while anthracite experienced a porosity increase of 3.04%, indicating a diminished effectiveness of NMP as the coal rank increased. These findings suggest that NMP selectively dissolves specific organic molecules in coals, thereby enhancing pore connectivity and promoting a transition from micro- to meso- and macropores. These findings highlight the potential of NMP in enhancing coalbed methane production and advance our understanding of the mechanisms behind solvent erosion.

Pore structure of deep coal of different ranks and its effect on coalbed methane adsorption

To study the influence of coal metamorphism on the pore system development characteristics of deep coal reservoirs, coal samples of different ranks were collected as research objects. Based on maceral identification and industrial analysis, the pore structure of the coal samples of different ranks was characterized on multiple scales by combining low-pressure CO2 adsorption (L-PA), low-temperature N2 adsorption (L-TA) and high-pressure mercury intrusion porosimetry (MIP) experiments. In this paper, the distribution and variation in pores in coal samples of different ranks were investigated, the relationship between the pore structure characteristics and coal metamorphism was examined, and the influence of coal metamorphism on the pore structure was analysed. CH4 isothermal adsorption experiments of the coal samples of different ranks were conducted to reveal the relationship between the Langmuir parameters and Ro,max. According to the shape of the hysteresis loop of the nitrogen adsorption–desorption curves, the pores in the low-rank coal samples mainly included slit pores and cylindrical pores, while those in the medium- and high-rank coal samples mainly included slit pores, semiclosed wedge pores and ink-bottle pores. There were significant differences in the pore structures of the coal samples of different ranks. With increasing metamorphism, the pore volume (PV) and specific surface area (SSA) first decreased and then increased according to a U-shaped trend, reaching minimum values at a Ro,max of 1.7 %. According to the characterization results of the coal sample pore diameter, the pore size distribution (PSD) type was mainly the unimodal micropore-dominated type. Coal micropores with pore diameters smaller than 1.5 nm largely contributed to the SSA and PV. In addition, the coal rank linearly increased with increasing Langmuir volume (VL), while the Langmuir pressure (PL) first decreased and then increased, indicating that the CH4 adsorption capacity increased with increasing metamorphism.

Further application of the D-A model to evaluate the isothermal CO2 ad/desorption characteristics of coal

The CO2 ad/desorption characteristics is essential for evaluating the effectiveness and suitability of CO2 injection into coal-bed to storage and enhances CH4 recovery (CO2-ECBM). We performed the isothermal CO2 ad/desorption experiments on four different ranks of coal by using the self-developed coal seam high-pressure gas ad/desorption test system in this study. It was found that the isothermal CO2 ad/desorption behavior can be adequately explained by the D-A model, as its parameters can reflect the adsorption capacity, the desorption hysteresis characteristic, and the micropore structure in coal samples. The saturation CO2 adsorption amount (Vmax) for the four coal samples is CC > YW > XLH > HG, showing a “decreasing-increasing-decreasing” trend as the coal rank growth, which is in general consistent with the relation between the total specific surface area, the total micropore volume and the micropore content in coal samples. The difference value in the characteristic adsorption energy (ΔE) in the D-A model can be used as a parameter to quantitatively characterize the hysteresis in the CO2 desorption processes compared to the adsorption processes in coal samples, and the larger ΔE implies the more significant desorption hysteresis. The desorption hysteresis of four coal samples is XLH ≈ HG > YW > CC in order, showing a trend of decreasing first and then increasing as the coal rank growth. The coefficient of structural heterogeneity n reflects the distribution of micropore structure, the larger value of n indicates a higher micropore volume and micropore content in coal. The pore structure is changed by the effect of CO2 ad/desorption, which increases the micropores content in coal, resulting in a larger structural heterogeneity coefficient in the desorption process.

Lithium isotopic composition of two high‑lithium coals and their fractions with different lithium occurrence modes, Shanxi Province, China

Coal and coal-bearing strata have been considered as potential economic sources of lithium, and, as such have attracted significant attention. Significantly high concentration of lithium has been found in the coals from Shanxi Province, North China. This study examined the lithium isotopic composition of two high-Li coals of different ranks (XJ-8 anthracite and DLT-11 bituminous coal) and their fractions (such as organic-, silicate-) obtained through sequential chemical extraction. Lithium was found to be predominantly associated with silicates. Lithium isotopic compositions in DLT-11 are more positive (δ7Li > 0‰) than those in XJ-8 coal (δ7Li < 0‰) irrespective of which are bulk coals or leachates. Specifically, the carbonate fraction in DLT-11 had the most positive lithium isotopic composition among all fractions. Carbonate fluid hosting positive lithium isotopic composition seems to have had an effect on the lithium isotopic composition of DLT-11 coal. Lithium isotopic composition of XJ-8 anthracite may be a result of lithium re-distribution between organic and inorganic components during coalification, and this was also responsible for lithium isotopic homogeneity in the coal seam.

Effect of cyclic load on mechanical properties and failure mechanisms of different rank coals

Underground coal is often subjected to periodic loads caused by mining stress. To determine the effect of cyclic load on mechanical properties of coal of different ranks and failure mechanisms, nanoindentation experiments and molecular dynamics (MD) simulations were used to study different rank coals. The results indicated that cyclic hardening occurred in all the coal matrices under cyclic loading. With the increase in coal rank, the change of the elastic modulus and the hardness, the energy dissipation rate, and the damage layer decreased, the cyclic hardening weakened, and the resistance of the six-membered ring structure increased. The plastic failure of the coal matrix was mainly connected with the bending and stretching of the bond, the dihedral angle twisting, and the out-of-plane bending vibration. The elastic deformation was correlated with the variation of the Coulomb force and the van der Waals force, the twisting and recuperation of the dihedral angle, and the out-of-plane bending vibration. With increasing coal rank, the effect of the elastic deformation of the Coulomb force weakened. When the coal rank exceeded a certain range, the influence of the plastic failure of the out-of-plane bending vibration was transformed into the elastic deformation, and the effect of the elastic deformation of the van der Waals force was transformed into the plastic failure.

Study on mechanism and characteristic of CO evolution of loading coal in inert atmosphere

To clarify the influencing factors and mechanism of CO generation during loading coal, coal loading experiments were conducted within nitrogen atmosphere to study CO evolution characteristics with different ranks of coal and temperatures. Macromolecular structures of different coals were established to reveal more details of CO generation at molecular level. The mechanism of CO generation was analyzed by combining Materials Studio simulations of the molecular evolution characteristics under the mechanical force of coal molecules, so as to provide theoretical support for mine fire prevention and control and improve the prediction accuracy of coal spontaneous combustion. The results showed that low rank coal produced more CO when subjected to mechanical forces. The increase of temperature had a promotion effect on the decomposition of coal samples by crushing to produce CO. The chemical bonds connected to the carbonyl group of coal molecules were more likely to be broken when subjected to external force.

A Comparative Investigation of the Adsorption Characteristics of CO2, O2 and N2 in Different Ranks of Coal

The adsorption mechanism of carbon dioxide, oxygen and nitrogen in coal is important for preventing and controlling coal spontaneous combustion and for understanding the technology of CO2 storage in goaf. Adsorption amount and adsorption heat are key adsorption parameters that are required to understand the material and energy conversions during adsorption in coal. In this study, we studied the factors that influence the adsorption amounts and adsorption heat values of carbon dioxide, oxygen and nitrogen in coal by testing four different coal samples using conventional coal quality analysis, low-pressure nitrogen and carbon dioxide adsorption, Fourier transform infrared spectroscopy and three gas adsorption experiments at different temperatures. Then, we analyzed the relationships between the structural parameters of the coal samples and the adsorption amounts and the adsorption heat values of carbon dioxide, oxygen and nitrogen. The results show that the adsorption isotherms of carbon dioxide conform to the Langmuir equation, and the adsorption isotherms of oxygen and nitrogen conform to Henry’s law between 0 and 110 kPa. The adsorption amounts of carbon dioxide, oxygen and nitrogen decreased with an increase in temperature, and the change in the rate of the adsorption amount with temperature was determined by the adsorption heat. The results of the pore structure show that the pores of the coal samples are composed of mesopores and micropores; the micropores contribute to the main specific surface area. The micropore and mesopore structures are the main determinants of the adsorption amounts of carbon dioxide, oxygen and nitrogen in coal. The gas adsorption heat is affected by the pore structure and the chemical composition of coal. The adsorption heat of nitrogen correlates positively with the pore structure of the coal. The adsorption heat of oxygen correlates positively with the ash, elemental nitrogen, elemental sulfur and mineral contents of the coal. The adsorption heat of carbon dioxide correlates positively with the elemental sulfur content of the coal.

Effect of coal type on the physical properties and CO2 adsorption performance of activated coke prepared by a single-step method

ABSTRACT Activated coke is considered to be one of the promising CO2 adsorbents. It could be prepared using coals by a single-step method, but the physical properties and CO2 adsorption performance of the prepared activated coke were significantly different when different ranks of coals were used as the raw materials. In this study, a single-step rapid pyrolysis activation method based on entrained-flow bed was proposed to prepare powdered activated coke (PAC) for CO2 adsorption. Six typical coals covering lignite, bituminous coal and anthracite were selected as raw material to prepare PACs by the proposed method. The pore structure, surface morphologies and surface functional groups of the prepared PACs were characterized and the yields were calculated. The CO2 adsorption capacities and adsorption selectivity for CO2/N2 were determined. Results show that the PAC prepared from lignite had the maximum specific surface area of 479 m2/g, the most abundant oxygen-containing functional groups and the highest CO2 adsorption capacity of 3.35 mmol/g at 0°C and 1.2 bar. The physical properties and CO2 adsorption performance of PACs prepared using bituminous coals were greatly affected by the caking property. The PACs prepared using non-caking/weak-caking bituminous coals, such as Zhundong coal and Jinjie coal had good physical properties and CO2 adsorption performance, while those prepared using strong-caking coals had poor physical properties and CO2 adsorption performance. The yields were higher than those of PACs prepared from lignite. The PAC prepared using anthracite had the similar physical properties and CO2 adsorption performance to PAC prepared using medium-caking bituminous coal, but the yield of 72.17% was the most. It could provide references and basic support for the selection of coal for rapid preparation of coal-based adsorbents related to CO2 adsorption by the single-step method.

K2CO3-catalyzed gasification of coal of different ranks in supercritical water for hydrogen production: A general kinetic model with good coal adaptability

Supercritical water gasification (SCWG) of coal provides a new solution for the green transformation and upgrading of traditional coal industry. Considering the good coal adaptability of SCWG and the excellent catalytic performance of K2CO3, a new kinetic model was developed in this work for predicting the catalytic gasification characteristics of coal of different ranks in supercritical water (SCW). In this model, various ranks of coal are characterized by the combination of three types of primary coal in different proportions, and the proportions can be obtained based on elemental analysis data and matrix computation. The SCWG of various ranks of coal can be considered as a combination of reactions of three types of primary coal in SCW. The model contains a total of 18 reactions, and various intermediates are represented by phenol and a high-carbon hydrocarbon. K2CO3-catalyzed SCWG experimental data of three different coal samples obtained in an improved quartz tube reactor system were used for the determination of model kinetic parameters. Then the experimental results of catalytic SCWG of other coal samples were used for the model validation, and it was found that the model can effectively predict the variations of gaseous products within an acceptable error. Afterward, the model was used to predict carbon gasification efficiency and gas compositions for coal of different ranks and to analyze carbon distribution and reaction rates for specific coal. The proposed kinetic model fits well with the good coal adaptability of SCWG technology, and it has great significance for the promotion of SCWG technology.

Investigation of cleat and micro-fracture and its aperture distribution in the coals of different ranks in North China: Relative to reservoir permeability

The apertures of cleats and micro-fractures in coal play an important role in the permeability of the coal bed. In this study, optical microscopy and scanning electron microscopy were used to investigate the morphology of cleats and micro-fractures and their apertures, distribution of minerals, and matrix/fracture interactions. The neighboring mineralized and unmineralized cleats suggest the possibility of multi-stage evolutionary processes of cleat formation during the coalification process. The micro-fracture distribution of coals is closely related to their components, including organic macerals and inorganic minerals. Micro-fractures are prone to developing at the junction surface of organic macerals or the surface of organic and inorganic minerals. A mineral-genetic micro-fracture can be classified as an intra-crystal micro-fracture, an extra-crystal micro-scale fracture, or a grain-edge micro-scale fracture. Compared with the low- and middle-ranking coals, cleat and micro-scale fractures in high-ranking coal are usually filled with carbonate minerals and clay minerals. Statistical analysis reveals that the aperture distribution of cleat and micro-fracture in coal shows a log-normal distribution. The aperture of cleat and micro-fracture shows a decreasing trend with increase in coal rank. For low-ranking coal, cleats contribute more to the permeability than micro-fractures. However, for the middle- and high-ranking coals, the contribution of cleats and micro-fractures to the coal reservoir permeability will be close. As the rank of coal increases, the degree of cleat contribution to reservoir permeability decreases, while the degree of micro-fracture contributing to the reservoir permeability increases. Possible reasons for the extremely low reservoir permeability in China may be the following: 1) subsurface cleats and micro-fractures close their apertures significantly due to the in situ geo-stress or 2) cleats and micro-fractures have better permeability in the geological history, which makes the precipitation of minerals decrease the coal reservoir permeability. Therefore, the acid solvent (e.g., HAc, HCl, and HF) added to the drilling or hydraulic fracturing fluid or the geo-stress relief technologies may be an effective way of enlarging the cleat or micro-fracture aperture and enhance the reservoir permeability for coalbed methane production.

Interaction between Droplets and Particles as Oil–Water Slurry Components

The characteristics of the collisions of droplets with the surfaces of particles and substrates of promising oil–water slurry components (oil, water and coal) were experimentally studied. Particles of coals of different ranks with significantly varying surface wettability were used. The following regimes of droplet–particle collisions were identified: agglomeration, stretching separation and stretching separation with child droplets. The main characteristics of resulting child droplets were calculated. Droplet–particle interaction regime maps in the B = f(We) coordinates were constructed. Equations to describe the boundaries of transitions between the droplet–particle interaction regimes (B = nWek) were obtained. The calculated approximation coefficients make it possible to predict threshold shifts in transition boundaries between the collision regimes for different fuel mixture components. Differences in the characteristics of secondary atomization of droplets interacting with particles were established. Guidelines were provided on applying the research findings to the development of technologies of composite liquid fuel droplet generation in combustion chambers with the separate injection of liquid and solid components, as well as technologies of secondary atomization of fuel droplets producing fine aerosol.

Estimation and forecasting of carbon dioxide emissions from coal-fired thermal power plants in Ukraine

Purpose. Development and verification of a method for calculating and forecasting CO2 emissions from coal combustion at thermal power plants based on proximate analysis data. Calculation of gross and specific CO2 emissions per unit of output energy and mass of coal consumed at Ukrainian thermal power plants (TPPs). Methodology. Methods of mathematical statistics were used for processing the data of ultimate and proximate analysis of 170samples of A, L, G, and LFG coal ranks with low heat value on operating state in the range of 17.2 to 31.0 MJ/kg and ash content on dry state (Ad) in the range of 3.8 to 38.0% to determine relationships between carbon emission factors (kc), calorific value, and ash content. Findings. The values of emission factors and gross CO2 emissions for mixtures of coals of grades A and L, G and LFG at Ukrainian TPPs in 20172021 were calculated. For 2021, the average value of for coals of grades G and LFG was 94,128 g/GJ, and for coals of grades A and L it was 104,987 g/GJ. Gross CO2 emissions at Ukrainian TPPs have been in the range of 3849million tons in recent years, and their annual reduction is due to a decrease in energy production and fuel consumption at TPPs, primarily of grades A and L. Originality. Empirical dependencies kc for steam coal of different ranks are determined in the form of The coefficients a, b, and c are determined for grades A, L, G, and LFG and their mixtures. The relationship between the carbon content in coal and the low heat value for coal is linear: where K is a coefficient depending on the coal grade. The values of K are determined for coal of grades A, L, G, and LFG. Practical value. Verification of the created method shows that the calculation error is less than 1.0%. This is in line with the requirements of the Monitoring Procedure and Directive 2003/87/EC. In 2021, the specific CO2 emission per unit of output energy at TPPs in Ukraine was 1,084 g/kWh for all ranks of steam coal. The values of specific CO2 emissions per unit mass of consumed coal were 1.94 t/t for coals of all grades, 1.91 t/t for grades G and LFG, and 2.21 t/t for grades A and L. The official annual reports of the Ministry of Energy of Ukraine contain information on the amount of produced electricity, consumed coal, and forecast balances of electricity production at TPPs, therefore, the values of specific emissions established by us are convenient to use for estimating and forecasting carbon dioxide emissions.