Thermodynamic analysis of the characteristics of producer gas upon the gasification of Moscow brown coal

The thermodynamic calculation of the temperature dependence of the equilibrium composition of the products of the steam-air gasification of Moscow brown coal with the following proximate analysis data was performed at the pressure P = 0.1 MPa: C ^r = 31, H ^r = 2.3, N ^r = 0.6, O ^r = 9.6, S ₁ ^r = 2.7, A ^r = 20.8%, and W ^r = 33%. The temperature dependence of the concentrations of gas-phase components was plotted for the gasification of 100 g of Moscow coal on a dry ash-free basis at the blast coefficient α = 0.3 with steam supply (4 mol of H₂O). It was found that, in this case, the gas phase mainly consisted of N₂, CO, and H₂ at a temperature higher than 800°C. The energy characteristics of the gas phase were calculated.     

Crystal structure,vibration characteristics and microwave dielectric properties of low loss MgMo1-xWxO4 solid solution ceramics

Solid-phase method was used to synthesize MgMo_1-xW_xO₄ (x = 0–0.15) ceramics. The influences of substitution Mo⁶⁺ with W⁶⁺ on crystal structure, vibration characteristics and microwave dielectric properties of MgMo_1-xW_xO₄ ceramics were comprehensively studied. X-Ray diffraction illustrated all samples exhibit single-phase monoclinic wolframite structure when x = 0–0.15, in which W⁶⁺ replaces Mo⁶⁺ sites formed solid solution. W⁶⁺ effectively improves sintering properties of the MgMoO₄, the average grain size and relative density were increased. Raman characterization reveals that suitable W⁶⁺ substitution amount leads to reduction of v₁ A_g peaks FWHM and the enhancement of specific v₃ A_g peak for Mo/WO₄ tetrahedron, which improves the ordered distribution of the crystal structure. The above combined effect results in the increased Q × f value, but has little influence of W⁶⁺ substitution on ε_r and τ_f for MgMoO₄. When x = 0.09, MgMo_0.91W_0.09O₄ ceramic sintered at 1050 °C has optimal microwave dielectric performance: ε_r = 7.21, Q×f = 90,829 GHz, τ_f = ?67 ppm/°C.     

Liquefaction of partially dried and oxidized coals: 1. Coal drying and oxidation

Belle Ayr subbituminous coal was dried with gases including nitrogen, air, and nitrogen-air mixtures (simulated flue gases) to study the effect of drying on the coal characteristics in preparation for subsequent liquefaction experiments. Drying was carried out in micro-, laboratory- and bench-scale units at temperatures from ambient to 200 °C. The net moisture-free oxygen content of the coal increased with time and temperature to 3 wt%. Volatile oxygen-containing species, other than carbon oxides, that may have been released during drying were not investigated as the objective was to characterize oxidation kinetics and changes in coal properties. Two distinct kinetic regimes of oxygen consumption were observed during drying; an initial high-rate period of E_A?42–55 kJ mol^?1 followed by one of low rate, E_A?13 kJ mol^?1. A Powhatan No. 5 (Pittsburgh seam) bituminous coal, which initially had much lower oxygen content than the Belle Ayr coal (7.9 versus 23.3 wt%), gave analogous drying and oxidation results; however, the maximum net moisture-free oxygen uptake was ≈8 wt%.     

Metamorphic development, degree of reduction, and other characteristics of Donets Basin coal

Analysis of the elementary composition and parameters V ^daf , y, and Q _s ^daf of coal from more than 100 beds in the Donets Basin indicates that the considerable difference in the properties of coal characterized by reduction (in terms of S _t ^d ) and uniform metamorphic development (according to C ^daf ) is due to variation in the ratio of the number of hydrogen and oxygen atoms (H/O_at) in the molecular component of the coal’s organic mass.     

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.     

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.     

Composition and Properties of Brown Coal from the Bodonskoe Deposit in Buryatia

The composition and properties of coal from the Bodonskoe deposit were studied. It was shown that this is low-sulfur (S ^d = 0.3–1.0%) and medium-ash grade 1B brown coal with a high yield of volatile substances (V ^daf = 56.1–60.9%). The humic acid content varies from 32.3 to 50.8%. The heat of combustion of coal is Q _s ^daf = 26.0–27.4 MJ/kg. The concentrations of toxic elements in the coal samples are at a background level.     

Composition, structure, and properties of Donetsk Basin and United States coal of the same metamorphic stage

The composition, structure, and properties of Donetsk Basin and United States coal of the same metamorphic stage are compared. The samples represent coal from the whole metamorphic series, with vitrinite reflection coefficient R _o = 0.7?C1.8%. Separate regression equations for Donetsk Basin and United States coal describe the relation between the composition (C ^daf , H ^daf , O ^daf ), structural characteristics (C_ar, f _a, ??, and B) calculated from the elementary composition, the technological properties (V ^daf , y, Q _s ^daf ), and the vitrinite reflection coefficient. Significant differences are found in these properties for Donetsk Basin and United States coal of the same metamorphic stage. These differences are mainly due to the different degrees of reduction of the coal. With a vitrinite reflection coefficient up to 1%, the degree of reduction is greater for United States coal than for Donetsk Basin coal. With greater metamorphic development (R _o ?? 1.0%), Donetsk Basin coal is characterized by even lower degrees of reduction.     

Infrared spectral studies of nanostructured Co2+-substituted Li-Ni-Zn ferrites

Polycrystalline Li_0.5Ni_0.25–0.5x Co_0.5x Zn_0.5Fe₂O₄ ferrites (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared by standard auto-combustion method and characterized by XRD and IR spectra. The XRD results suggest that all samples were single-phase with a cubic spinel-type structure. The lattice constant, particle size, metal-oxygen bond length (R _A and R _B), cation radii (r _A and r _B) on A and B-sub lattices were found to increase while the X-ray density and porosity, decrease with increasing x. The IR spectra show two absorption bands, at ν₁ about 600 cm^?1 and ν₂ at about 425 cm^?1, which were attributed to tetrahedral (A) and octahedral (B) sites of the spinel structure, respectively. The band positions were found to depend on x. The force constants, K _t and K _o, were calculated and plotted against cobalt concentration x. Compositional dependence of the force constants is explained in terms of cation-oxygen bond distances and redistribution of cations.     

Accumulation of trace elements in coals from various basins of Russia

The average concentrations of trace elements in coals from the South Fergana, North Sos’va, Kizelovsk, South Yakutian, Transbaikalia, Pechora, and Zyryansk deposits and some deposits of the Kuznetsk and Primor’e Basins are compared. The degrees of trace element concentration were calculated both on a total coal weight basis (Q _i ) for individual basins and on a mineral matter basis (Q _i ^A ) with reference to Clarke numbers in clay rocks. Ratios between the concentrations of typomorphic trace elements on a coal mineral matter basis were calculated for the deposits of basins with different geologic-geochemical formation conditions (X _i ^A ); the concentration ratios between the pairs of typomorphic trace elements in the considered coal basins (Z _i ) were also calculated. Typomorphic elements are the trace elements with Q _i > 1.4 or Q _i ^A > 2. Coal basins of different origin have different numbers of typomorphic trace elements calculated in terms of the parameter Q _i and, to a lesser degree, the parameter Q _i ^A . Coal basins differ considerably from each other in both the ratios between the average concentrations of the same trace element in the mineral matter of coal (parameter X _i ^A ) and the ratios between the concentrations of two different trace elements (parameter Z _i ). In the basins under discussion, the mineral matter of coals from formations created in areal rift genesis regions, in particular, Triassic-Jurassic coals and, to a lesser degree, Carboniferous coals, are enriched in trace elements to the greatest extent. Coals from subgeosynclinal formations have a maximum number of typomorphic trace elements (in terms of the average concentrations in the mineral matter), practically the majority of the test elements with the exception of Nb, Sn, Ni, and Sc. Coals from young mobile platforms are characterized by a similar number of typomorphic trace elements with the exception of Nb, Zn, Y, and Yb. Coals from geosynclinal formations have a somewhat smaller set of typomorphic trace elements, whereas a minimum number of typomorphic elements is characteristic of coals from platform basins.     

Characterization of pH-dependent micellization of polystyrene-based cationic block copolymers prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization

A series of block copolymers composed of a fixed length of an (ar-vinylbenzyl)trimethylammonium chloride (Q) block (the number average degree of polymerization of the Q block, DP_n,Q=57) and varying lengths of an N,N-dimethylvinylbenzylamine (A) block (the number average degrees of polymerization of the A blocks, DP_n,A, ranging 11-50) were prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization, and their pH-dependent micellization was characterized by potentiometric titration, ¹H NMR spectroscopy, dynamic and static light scattering, and fluorescence techniques as a function of the A block length. At pH<5.5, the A block is fully protonated, and hence the block copolymers act as a simple polyelectrolyte, dissolving molecularly in acidic water. At pH>7, the A block becomes deprotonated, and thereby the block copolymers aggregate into a micelle composed of hydrophobic microdomains formed from the deprotonated A blocks. Results of light scattering and fluorescence measurements indicated that the micellization behavior depended strongly on the length of the A block. The number of polymer chains comprising one micelle (i.e. mean aggregation number, N_agg) increased from 3 to 12 as DP_n,A increased from 11 to 50 at pH 10.0. In the case of a random copolymer of Q and A with an A/Q molar ratio similar to that of a block copolymer with DP_n,A=50, N_agg∼1 (i.e. unimolecular micelle) was confirmed by static light scattering at pH 10.0.     

Solvent de-ashing from heavy product of brown coal liquefaction using toluene:: 2. concentration and separation of ash with a continuous de-ashing system

The brown coal liquefaction (BCL) process is a two-stage liquefaction (hydrogenation) process developed for Victorian brown coal in Australia. The BCL process has a solvent de-ashing step to remove the ash and heavy preasphaltenes from the heavy liquefaction product (vacuum residue) derived from the coal in primary hydrogenation and named CLB (coal liquid bottom). This solvent de-ashing step uses toluene or coal-derived naphtha as a de-ashing solvent (DAS). After dissolving the CLB into the solvent (CLB/solvent ratio, 1/8–1/4, w/w) under high temperature (200–290°C) and high pressure (4–5 MPa), insoluble solid particles which consist of ash and heavy preasphaltenes are settled by gravity and separated from the solution as an ash-concentrated slurry. The ash-concentrated slurry and the de-ashed solution are withdrawn from the settler as an underflow and overflow, respectively. The de-ashed heavy product is recovered from the solution by eliminating the solvent and is further hydrogenated in secondary hydrogenation. The authors have reported on the solubility of CLB in toluene and the settling velocity (V) of the boundary of ash content in the settler under de-ashing conditions. This paper discusses the effects of de-ashing conditions on ash concentration in the settler bottom and the operating conditions of a continuous de-ashing system. The ash content in underflow (C_UF, kg/kg or wt.%) at the settler bottom was found to increase with temperature and to decrease with the rate (flux) of downward flow (underflow). The maximum C_UF, Z, is expressed by the equation: Z=B_CLB(FL/0.35)^−0.32(T/523)^4.26, where B_CLB, FL and T are the characteristic parameters of organic CLB (kg/kg or wt.%), flux of underflow in the settler (kg/m² s) and temperature (K), respectively. B_CLB is also expressed by using the analytical results of organic insolubles in the CLB under de-ashing conditions. Finally, stable operating conditions of a continuous de-ashing system are confirmed to be determined as the following qualifications: |V_u|<|V|, W_UF>W_SA/C_UF and Z>C_UF, where |V_u|, |V|, W_SA and W_UF are the upward velocity of the solution in the settler (mm/s), settling velocity of the ash boundary (mm/s) in the settler, flow rate of ash in the feed slurry (kg/h) and flow rate of underflow (kg/h), respectively. Under these qualified conditions, the 50 t/d pilot plant constructed in Australia was operated under stable conditions for 3700 h using toluene as a DAS.     

Improved microstructure and high quality factor of Li2Ti0.9(Zn1/3Ta2/3)0.1O3 microwave ceramics with LiF additive for LTCC applications

In this study, LiF was utilized to decrease sintering temperature, improve microstructure, enhance Q×f, and regulate τ_f of Li₂Ti_0.9(Zn_1/3Ta_2/3)_0.1O₃ (abbreviated as LTZT) ceramics. A complete solid solution together with a phase transition from monoclinic to cubic rock salt structure occurred. The cell volume of LTZT ceramics decreased as the LiF content increased. Relatively dense and uniform microstructures were observed for the ceramics as the LiF content was not less than 2 wt%. The dielectric constant of LTZT ceramics initially increased and then decreased with the increasing LiF content. The FWHM of the Raman band at about 808 cm^?1 was closely related to the Q×f value. Notably, the samples with 3 wt% LiF exhibited the highest relative density of 97.4 % and satisfactory microwave dielectric properties of ε_r = 23.14 ± 0.16, Q×f = 110,090 ± 1100 GHz, and τ_f = +3.25 ± 1.45 ppm/°C when sintered at 950 °C. Good chemical compatibility with silver indicated the ceramic is a promising candidate in LTCC applications.     

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).     

A3Y2Ge3O12 (A = Ca,Mg): Two novel microwave dielectric ceramics with contrasting τf and Q × f

Two garnet-structured microwave dielectric ceramics of A₃Y₂Ge₃O₁₂ (A = Ca, Mg; called CYG and MYG, respectively) were synthesized. CYG was crystallized in a normal cubic garnet structure with Ca²⁺ fully occupying the dodecahedral (A) site, whereas MYG was an inverse garnet with mixed distribution of Mg²⁺/Y³⁺ at the A site. The difference in ionic occupation resulted in anomalies in microwave dielectric properties, with dielectric constant (ε_r) = 14.1, quality factor (Q × f) = 12,600 GHz and positive temperature coefficient of resonant frequency (τ_f) =120.5 ppm/°C for MYG ceramic and ε_r = 10.8, Q × f = 97,126 GHz and τ_f = −40.6 ppm/°C for CYG ceramic. The large deviations in measured ε_r from theoretical ε_th possibly resulted from the garnet structural constraints leading to ‘rattling’ Mg²⁺ and Y³⁺ in A site of MYG. Infrared reflectivity spectra analysis revealed ion polarization contributed mostly to the permittivity of both ceramics in microwave frequency ranges.     

Nonlinear dielectric effect of Fe2O3-doped PMS–PZT piezoelectric ceramics for high-power applications

Piezoelectric ceramics of Pb_0.98Sr_0.02(Mn_1/3Sb_2/3)_0.05Zr_0.48Ti_0.47O₃ with 0.25 wt% CeO₂, 0.50 wt% Yb₂O₃, and x wt% Fe₂O₃ (x = 0.02, 0.05, 0.1, 0.15, and 0.2) additives were synthesized using a conventional solid-state reaction. Their piezoelectric properties and, in particular their nonlinear dielectric behaviors were systematically investigated. Iron was mainly present in the form of Fe³⁺ based on X-ray photoelectron spectroscopy; a small amount of the iron was reduced to Fe²⁺. Iron occupied the B-site of the perovskite structure, as shown in the refinement results. The samples displayed both “soft” and “hard” properties because Fe³⁺ can be incorporated at the Mn²⁺, Zr⁴⁺, Ti⁴⁺, and Sb⁵⁺ sites. The domain wall motion was found to be related not only to the type of deficiency but also to the grain size and grain boundary effects based on the nonlinear dielectric behaviors under alternating electric fields. The optimal overall properties of d₃₃ = 360 pC/N, tan δ = 0.295%, Q_m = 1500, k_p = 0.61, ε_r = 1055, α_ε = 4.574*10⁻⁴ m/V, and tan δ = 2.76% (under 500 V/mm) were obtained for samples sintered at 1150 °C(x=0.15).     

Analysis of energy-size reduction relationships in batch tumbling ball mills

A theoretical energy-size reduction relationship is derived for tumbling ball mills based on a solution of the integro-differential equation of comminution kinetics, in which the proportional relationship is applied between the grinding rate constant and the net mill power. The derived formula is similar to an empirical energy law, dW ∝ dx_r/x_rⁱ, where W is the specific energy input, x_r is the particle size of product and the exponent i is shown to be a variable depending upon the ground material, the type of mill and the method to measure energy. Derived results are confirmed with reported data in reasonable agreement. Also, the Bond's energy law is examined and a method for the correction of the Bond work index is discussed.     

Water recovery from humidified waste gas streams: Quality control using membrane condenser technology

In this work “membrane condenser” is utilized for the selective recovery of evaporated waste water from industrial gases and for the control of the composition of the recovered liquid water. A simulation study of the process has been developed for predicting the membrane-based process performance. The achieved results indicate that feed flow rate (Q^Feed), interfacial membrane area (A^Membrane), the ratio Q^Feed/A^Membrane, the temperature difference (ΔT) between the fed flue gas T_feed and the membrane module are the parameters controlling the process. In particular, the amount of recovered water rises at increasing ΔT and Q^Feed/A^Membrane, whereas its quality is made worse at increasing ΔT and Q^Feed. The data obtained have been also supported by an experimental study of the process, confirming the validity of the simulation study and its suitability for a screening of the operative conditions to be chosen in a membrane condenser.     

Raman spectra and surface structure of CaO-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> glass leached in potassium hydroxide solutions

It is difficult to research on the surface structure of amorphous phase in fly ash during leaching reaction due to crystalline phase and complex structure. In the present work, in order to reveal the effects of leaching reaction on the surface structure of amorphous phase in fly ash, the modelling CaO-Fe₂O₃-Al₂O₃-SiO₂ glass was prepared by the traditional melting methods. The leaching reaction of CaO-Fe₂O₃-Al₂O₃-SiO₂ glass with 7.5 M KOH was investigated by spectroscopy, spectrophotometer and wet chemical method. The results show that the content of Q ¹, Q ², Q ³ and Q ⁴ of glass without corrosion was 4.21, 9.51, 23.03 and 52.55%, respectively, which shows that the network polymerization of glass is compact. The leaching reaction of glass can be described by the following equation: dS/dt = k/(r + S ₀). Leaching in KOH for various times induces the content of Q ⁴ and Q ¹ to be decreased, and Q ² and Q ³ increased, resulted in the depolymerization of network and the surface glass dissolved in alkaline solution to form a gel phase. In stage one of leaching reaction, the rate of iron ion leached from glass surface was slow, which resulted in the small slope of straight-line relationship of leaching curve. In the following stage, the leaching rate of iron ion increased with the prolongation of time.