Composition and properties of coals from the Yurty coal occurrence

Coals from the Yurty coal occurrence were studied. It was found that the samples were brown non-coking coals with low sulfur contents (to 1%) and high yields of volatile substances (V ^daf to 53.4%). The high heat value of coals Q _s ^daf was 20.6–27.7 MJ/kg. The humic acid content varied from 5.45 to 77.62%. The mineral matter mainly consisted of kaolinite, α-quartz, and microcline. The concentration of toxic elements did not reach hazardous values.     

Production and Use of Lignite-Based Coke Briquets with High Hot Strength

A production technology has been developed for strong briquets (with high CSR and M₂₅) based on coke derived from Kansko-Achinsk lignite. A mixture consisting of lignite coke and binder (Zh and KZh coal) is crushed (to particle size less than 0.2 mm) and mixed with strengthening additive. This blend (57.7% lignite coke + 19.2% binder + 23.1% additive) is shaped into briquets, which are roasted at 1000°C and cooled in the absence of air. For the briquets, CSR = 58.8% and M₂₅ = 97.4%. The strength in drop tests is 99.1%, and the wear resistance is 99.2%. Technical analysis of the briquets shows that W = 1–2%, A^d = 8–10%, V^daf = 3–7%, S^d = 0.2–0.4%, P^d = 0.014%, and C_fix = 85–88%. The briquets are characterized by distinctive physicochemical properties, such as high activity with respect to CO₂ (\(K_{CO_2}\) = 4.6 cm³/g s; CRI = 66.1%). Its electrical resistivity ρ = 8 Ω cm for the 3–6 mm size class; and its developed porosity is 50–56%. Applications of the briquets are outlined.     

Moisture-holding capacity of coals

As a result of a comprehensive study of 63 samples of coal concentrates (from Ukraine, Russia and countries outside the former Soviet Union), it was established that the prediction of the moisture-holding capacity of coals can be appropriately performed according to their values of W ^a, R ₀, O _d ^daf , and O _s ^daf . It was found that the oxidation of coal increased its moisture-holding capacity; however, in this case, the absolute change in this parameter was smaller than the error of its determination (0.5%). Therefore, upon the oxidation of almost 30% of the organic matter of coal, the moisture-holding capacity increased by only 0.4%. There is a close correlation between the maximum moisture capacity of coals and the water pore volume, and this correlation was described by a linear equation in the studies.     

Predicting the classification characteristics of coal. Part 3. Gross calorific value of dry,ash-free coal

For 63 samples of Ukrainian, Russian, and imported coal, equations for predicting the gross calorific value Q_s^daf on the basis of the following coal characteristics are developed: W^a, O_d^daf, Q_s^af, and C_ar. The error is within the standard tolerances (σ ≤ 0.3 MJ/kg). With sufficient accuracy, Q_s^daf may be predicted from equations based on petrographic characteristics such as the vitrinite reflectance, the content of liptinitegroup minerals, and the sum of lean macerals (I + 2Sv/3). In these equations, the coefficients correspond to the heat of combustion of the vitrinite components at different metamorphic stages, the liptinite, and the lean macerals.     

Ignition temperature of coal. 1. Influence of the coal’s composition,structure, and properties

The reactions of coal with the materials used in determining the ignition temperature of unoxidized coal according to Ukrainian State Standard DSTU 7611:2014 are analyzed. First, the ignition temperature of various types of coal from Ukraine, Russia, Canada, Australia, the Czech Republic, Poland, and Indonesia is determined. The influence of the composition, structure, and properties of the coal on its ignition temperature is assessed. The ignition temperature of the unoxidized coal is found to be closely related to the content of organic carbon C^daf and aromatic carbon C_ar, the structural parameter δ characterizing the degree of saturation of the coal’s organic mass, and also the vitrinite reflection coefficient R_o and the yield of volatiles V^daf.     

Predicting the classification characteristics of coal. Part 2. Maximum moisture content

Analysis of 63 samples of coal concentrates (from Ukraine, Russia, the United States, Canada, Australia, and Poland) currently employed at Ukrainian coke plants indicates that the prediction of the maximum moisture content of coal may expediently be based on R _o and Q _s ^daf , determined, respectively, in plant laboratories and in power-station laboratories. The maximum moisture content of metamorphically distinct coals does not depend on their ash content (in the range 3.7–35.3%) nor on the chemical composition of the ash, expressed by the basicity index B _b (in the range 1.24–27.18) and the base/acid ratio I _b (in the range 0.198–1.832). Although the oxidation of coal also increases the maximum moisture content, this change is less than the error in its determination (0.5%). The oxidation of practically 30% of the coal’s organic mass increases the maximum moisture content by no more than 0.4%     

Oxidation of coke with petroleum-based coking additives

The properties of coking batch may be stabilized by means of DK coking additive based on the products of petroleum pyrolysis, characterized by low ash content (A^d = 0.4%), high sulfur content (S_t^d= 4.1%), and high yield of volatiles (V^daf = 17.2%) relative to coal concentrates. Individual coking of DK coking additive yields a product (particle size >40 mm) with postreactive strength CSR = 77–79%, reactivity CRI = 18–22%, and density 1200–1400 kg/m³. Differential scanning calorimetry of experimental coke samples reveals six stages in their heat treatment in air: preliminary heating, intense oxidation, gasification of carbon, surface combustion of the gaseous products, their flare combustion, and oxidation of the residue. The use of DK coking additive in the coking batch shifts the oxidation process to higher temperatures and ensures the largest interval of heat liberation at elevated heating rate, with up to 50% DK additive. With increase in the content of DK additive from 30 to 50%, the activation energy is increased by 4.56 kJ/mol for each additional 10%. In that case, the supply of atmospheric oxygen to the combustion zone must be improved     

IR Spectroscopy in Rank and Group Assignment of Coal

The possibility of express determination of the characteristics V _IR ^daf , R_{o, IR}, y_IR, ΣLC_IR, and A _IR ^d used in the ranking of coal on the basis of IR spectroscopy is assessed for a specific example: Kuznetsk coals of different maceral composition and metamorphic development. The IR characteristics are compared with values obtained by standard methods (V^daf, R_{o, r, y}, ΣLC, and A^d).     

Assessing the technological value of coal in coking

Coking coal of the same rank from different countries and fields may be distinguished in terms of use value by rating on the basis of seven technological and petrographic characteristics that determine the coke yield and properties: the ash content A^d; the total sulfur content S_t^d; the yield of volatiles V^daf; the plastic-layer thickness y; the vitrinite reflection coefficient R_o; the content of vitrinite-group macerals Vt; and the basicity index B_b. A range of values and a rating (on a scale from 1 to 10) are established for each of these parameters. Each rating corresponds to a particular score (from 0.1 to 1.0). Ranges of A^d, S_t^d, Vt, and B_b are established for the whole metamorphic series, while ranges of V^daf, y, and R_o are established for individual ranks and groups of ranks. Altogether, 105 coking coals from Ukraine, Russia, the United States, Australia, and Canada that are used at Ukrainian coke plants are investigated. The range of rating scores and their mean values are determined for individual coal ranks and groups. As an example, three bituminous coals from Ukraine, the United States, and Australia are compared by the proposed method. This method permits objective assessment of the technological value of coal within a single rank and the selection of the best purchase option.     

Properties of adsorbents prepared by the alkali activation of Aleksandriisk brown coal

Highly microporous adsorbents (micropore fraction of ～70%) were prepared by the alkali activation-thermolysis (800°C, 1 h) of brown coal (C ^daf = 70.4%) in the presence of potassium hydroxide at the KOH/coal weight ratio R _KOH ≤ 2.0 g/g. The dependences of the specific surface areas and adsorption capacities of the adsorbents for methylene blue (A_MB, mg/g), iodine (A_I, mg/g), and hydrogen (\(A_{H_2 } \), wt %) on R _KOH were determined. The adsorbents obtained at R _KOH ≥ 1.0 g/g exhibited developed specific surface areas and good adsorption characteristics (A_I = 1000–1200 mg/g, A_MB = 200–250 mg/g, and \(A_{H_2 } \) ≤ 3.16 wt % at 0.33 MPa). The high capacity for hydrogen allowed us to consider brown coal adsorbents as promising materials for use as hydrogen accumulators.     

Rapid Quality Assessment of Coal

No satisfactory methods are available for rapid and reliable prediction of one or more coal characteristics. The ignition temperature t_ig of coal, determined in assessing the oxidation of coal in accordance with Ukrainian State Standard DSTU 7611:2014, may be regarded as a useful predictor of coal quality. Research shows that t_ig depends on the composition and ordering of the coal’s organic mass. Mathematical and graphical means of predicting the V ^daf and R_o values of coal are developed.     

Properties of the solid thermolysis products of brown coal impregnated with an alkali

The mechanism of formation of a porous active carbon framework is considered, and the properties of the solid thermolysis products of brown coal (Aleksandriisk deposit, Ukraine) with potassium hydroxide are studied. The yields of the solid thermolysis products (Y _STP, %) and potassium humates, the rate of the interaction of the solid thermolysis products with KOH at 700–900°C, the specific surface areas (S _BET, m²/g), the adsorption capacities for methylene blue (A _MB, mg/g) and iodine (A _I, mg/g), and the specific activities of surface areas A _MB ^′ = A _MB/S _BET and A _I ^′ = A _I/S _BET (mg/m²) are determined under variation of the KOH/coal ratio (R _KOH < 18 mol/kg) and temperature (110–900°C).     

Properties of Kuznets Basin gas coal

Six samples of G coal characterized by different vitrinite reflection coefficient (R _o,r = 0.64–0.74%) are investigated. With increase in R _o,r , the plastic-layer thickness y increases from 7 to 17 mm, the free-swelling index SI from 0.5 to 3.5, and the Roga index RI from 1 to 21. The temperature range of plasticity expands from 34 to 94°C. The results clarify the difference in clinkering properties of the gas coal.     

Local Turbulent Energy Dissipation Rate in an Agitated Vessel: Experimental and Turbulence Scaling

The hydrodynamics and the flow field in an agitated vessel were measured using 2-D time resolved particle image velocimetry (2-D TR PIV). The experiments were carried out in fully baffled cylindrical flat bottom vessels 300 and 400 mm in inner diameter. The 300 mm inner diameter tank was agitated by a Rushton turbine 100 mm in diameter, and the 400 mm inner diameter tank was agitated by a Rushton turbine 133 mm in diameter. Three liquids of different viscosities were used as the agitated liquid: (i) distilled water (ν = 9.35 × 10^–7 m²/s), (ii) a 28 vol % aqueous solution of glycol (ν = 2 × 10^–6 m²/s), and (iii) a 43 vol % aqueous solution of glycol (ν = 3 × 10^–6 m²/s). The velocity fields were measured at an impeller rotation speed in the range from 300 to 850 rpm, which covers the Reynolds number range from 50000 to 189000. This means that fullydeveloped turbulent flow was reached. The experiments were performed to investigate the applicability of the following relations: ε* = ε/(u⁴/ν) = const, vK/u = const, Λ/ηK = const, τ_Λ/τ_K = const, ε* = ε/((Nd)4/ν) = const, Λ/d ∝ Re^–1, ηK/d ∝ Re^–1, vK/(Nd) = const, Nτ_Λ ∝ R^–1, Nτ_K ∝ Re^–1, and ε/(Nq) ∝ Re. These formulas were theoretically derived in our previous work, using turbulence theory, in particular, using turbulence spectrum analysis. The correctness of the proposed relations is investigated by statistical hypothesis testing.     

Basic functional relations in coal petrology

Functional relations between the parameters of the organic system and external factors are established. The following parameters of the organic system are considered: the petrographic composition of the coal’s organic mass, expressed as the ratio of newly formed components F/Vt; the ash content A ^d ; and the concentration of microelements in the coal. The external factors considered are the partial pressure \({p_{{O_2}}}\) of pfree oxygen (in aerobic conditions), the oxygen activity [O₂] (in anaerobic conditions), and the activity of HCl^–, HS^–, and Cl^– in the infiltrating aqueous solution. The microelement content in the coal’s organic mass is determined from the concentrations in the infiltrating solution that reaches the organic system. The influence of the petrographic composition and the ash content of the coal on its microelement concentration is assessed. The characteristics of the mic roelements and their removal from associations in paragenesis are discussed.     

Local turbulent energy dissipation rate in an agitated vessel: New approach to dimensionless definition

Using theory of turbulence, particularly using turbulence spectrum analysis, the relations ε^* = ε/(u ⁴/ν) = const., v_K/u = const. and Λ/η_K = const. were derived. Assuming that u ∝ (Nd) from this it follows that the widely used dimensionless local turbulent energy dissipation rate defined as ε/((N ³ d ²) is directly proportional to impeller Reynolds number, i.e. ε/((N ³ d ²) ∝ Re, and length scale ratio Λ/d is indirectly proportional to impeller Reynolds number, i.e. Λ/d ∝ Re^–1, in an agitated vessel at high Reynolds number. The relations obtained by turbulence spectrum analysis were used for estimation of local turbulent energy dissipation rates experimentally measured by Ståhl Wernersson and Trägårdh (1998, 1999) covering the range of Re = 87600–910200 and own experimental data covering the range of Re = 50000–189000. The experiments have been performed in tanks of 300 mm and 400 mm in the inner diameter for three different viscosities and for various impeller rotational speeds.     

Production of high-carbon ferrochrome from dry-quenched semicoke

The quenching of semicoke by saturated steam (heating-gas temperature 550°C) is described. The working-moisture content W^r in the semicoke is 3.0–6.7% for the new quenching method. As a reducing agent, semicoke has good characteristics: relatively low ash content (A^d = 7.1%), low sulfur content (S^d = 0.13%) and phosphorus content (P^d = 0.029%), and high reactivity (\({K_{C{O_2}}}\) = 4.0 cm³/g s) and electrical resistivity (ρ > 1.9 × 10⁶ Ω cm). In tests, dry-quenched semicoke performs well in the production of high-carbon ferrochrome: decreased power consumption; increased furnace productivity; decreased consumption of chromium ore; and decreased sulfur content in the ferrochrome when Karaganda coal is completely reduced by the semicoke. The optimal semicoke content in the batch is up to 50 kg.     

Solution-Combustion Synthesis of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> as a Cathode Material for Lithium-Ion Batteries

A cathode material for lithium-ion batteries–LiNi_1/3Co_1/3Mn_1/3O₂–was prepared by solution combustion synthesis and characterized by XRD, SEM, and galvanostatic charge/discharge cycling. The sample calcined at 950°C for 10 h showed best charge/discharge performance. An initial discharge capacity (C) of 150.5 mA h g^–1 retained 95.7% of its value after 75 charge/discharge cycles at I_c = 14 mA g^–1 (0.2C rate), I_d = 70 mA g^–1 (0.5C rate).     

Influence of batch composition and clinkering properties on the hot strength of coke and blast-furnace operation

The relation of the basic characteristics of coking batch to the hot strength CSR and reactivity CRI of coke is established. The plastic layer of the batch components influences CRI and CSR. The relation of the batch composition to CSR and CRI is determined. When using enrichment batch that contains ～50.4% cokeforming coal, the best results are obtained: CSR = 61.8–62.3% and CRI = 26.4–26.7%.     

Thermal expansion and phase transitions in K<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Rb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>BSi<Subscript>2</Subscript>O<Subscript>6</Subscript> leucite borosilicate solid solutions

Continuous solid solutions and the reversible phase transition from the I-43d cubic phase to the Ia-3d cubic phase are revealed in the borosilicate series K_{1 ? x} Rb _x BSi₂O₆. Samples in the KBSi₂O₆-RbBSi₂O₆ system are prepared by solid-phase synthesis and crystallization of glasses and investigated using the annealing and quenching technique, high-temperature X-ray diffraction, and dilatometry. The above polymorphic phase transition is observed in all solid solutions at temperatures in the range from 330 to 430°C depending on the composition: an increase in the rubidium content in the solid solution leads to a gradual decrease in the phase transition temperature. The linear thermal expansion coefficients α are determined for solid solutions of different crystalline modifications and glasses. The linear thermal expansion coefficients α for the I-43d low-temperature phase are equal to (20–23) × 10^?6 K^?1 according to the X-ray diffraction data and (21–24) × 10^?6 K^?1 according to the dilatometric data. The values of α for the Ia-3d high-temperature phase lie in the range (4–9) × 10^?6 K^?1 according to the X-ray diffraction data and in the range (6–9) × 10^?6 K^?1 according to the dilatometric data. The linear thermal expansion coefficients for both modifications decrease with an increase in the rubidium content in the solid solutions. The linear thermal expansion coefficients for glasses α = (10–11) × 10^?6 K^?1 are close to those for the high-temperature modification and virtually independent of the sample composition. The I-43d (cubic) ai I4₁/a (tetragonal) o Ia-3d (cubic) polymorphic phase transitions in the KBSi₂O₆ compound are revealed by differential scanning calorimetry (DSC) and dilatometry. Their reversibility is confirmed by the DSC data.