Online deposition measurement and slag bubble behavior in the reduction zone of pulverized coal staged combustion

An online thermogravimetric measurement method of ash deposition was developed. Ash deposition and slag bubble in the reductive zone of pulverized coal staged combustion were investigated. Firstly, a steady pulverized coal staged combustion was achieved in an electrically heated down-fired furnace. Additionally, gas species, coal conversion, and particle size distribution were quantitatively measured. Secondly, real-time ash deposition rates at different temperatures (1100–1400 °C) were measured, and deposition samples were carefully collected with an N₂ protection method. The morphologies of collected samples were investigated through a scanning electron microscope. It was found that the deposited ash transformed from a porous layer composed of loosely bound particles to a solid layer formed by molten slag. Different behaviors of the slag bubble were observed, and bubble sizes were significantly affected by the deposition temperature. A deposition and bubble formation mechanism was proposed and used for modeling. Results showed that the proposed model well predicted the observed ash deposition and bubble formation process.     

Structural and electrochemical characterization of Ce0.85Ca0.05Sm0.1O1.9 oxide ion electrolyte with Sr-doped LaMnO3 and SmCoO3 cathodes

This paper reports on the electrochemical properties and chemical stability of a recently developed Ca²⁺ and Sm³⁺-doped oxide ion conducting electrolyte, Ce_0.85Ca_0.05Sm_0.1O_1.9 (CCS), employed in an intermediate temperature solid oxide fuel cell (IT-SOFC) using conventional Sm_0.5Sr_0.5CoO₃ (SSC) and La_0.8Sr_0.2MnO₃ (LSM) cathodes in air at elevated temperatures. The materials were prepared by conventional solid-state reactions using their corresponding metal oxides and salts in the temperature range of 1,200–1,450 °C in air. Powder X-ray diffraction (PXRD) and impedance spectroscopy were employed for phase formation, chemical compatibility, and electrochemical characterization. PXRD studies on 1:1 weight ratio of heat-treated (1,000 °C for 3 days) mixtures of SSC or LSM and CCS revealed the presence of fluorite-type and perovskite-like phases. The area-specific resistance (ASR) value in air was lower for SSC cathodes (4.3–0.15 Ω cm²) compared to those of LSM (407–11 Ω cm²) over the investigated temperature range of 600–800 °C. As expected, a significant increase in ASR was observed in Ar as compared to air.     

Lower concentration limit of carbon filtration combustion

For mixtures of carbon materials and an inert filler, dependences of the characteristics of the filtration combustion wave on the gaseous oxidizer supply rate at a fuel content in the mixture of less than 7 wt % were obtained. The existence of a lower concentration limit for a steady-state filtration combustion wave was established. It was demonstrated that at a given intensity of heat loss, the concentration limits are determined by the reactivity of the carbon material and the oxidizer supply rate. At the effective coefficient of heat loss α = 8 W/(m² K), effective conductivity of mixture material λ = 2 W/(m K), and air supply rate G = 0.1 m/s, the lowest fraction of carbon in the mixture at which combustion is still possible was 4.5 wt % for carbon-carbon composite, 2.5 wt % for activated birch coal, and 2.0 wt % for birch coal, the most reactive kind of carbon.     

Dynamics of erosion plasma formation and formation of a plasma flame with a condensed disperse phase when quasi-continuous laser radiation acts on bismuth

The dynamics of near-surface plasma formation and the formation of an erosion plasma flame was investigated for quasi-continuous laser radiation (λ=1.06 μm, q=0.1–10 MW/cm², τ∼1.5 msec) acting on bismuth targets in air. The absence of low-threshold plasma formation at q<2 MW/cm² was established and explained. Instabilities in the plasma formation were revealed and the range of laser radiation power densities (2≤q≤4 MW/cm²) at which these instabilities take place was determined. At q≥5.4 MW/cm², brightening of the flame was noted. The dependence of the luminescence temperature of the flame on the laser radiation power density q was determined. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 126–133, January–February, 1998.     

Mössbauer Studies of Thermal Power Plant Coal and Fly Ash

Iron-57 Mössbauer spectroscopic studies were carried out at room temperature on samples of coal, slag (bottom ash) and mechanical ash collected from Bhatinda (India) thermal power plant. Hyperfine parameters such as isomer shift, quadrupole splitting and total internal magnetic field of ⁵⁷Fe nuclei were used to characterize various iron-bearing minerals. The observed parameters indicate the presence of pyrite, siderite and ankerite in coal sample while magnetic fractions of mechanical ash and slag samples show the formation of hematite and Al-substituted magnesio-ferrite. The non-magnetic fraction of slag ash shows the dominance of Fe²⁺ phases while that of mechanical ash demonstrates the formation of both Fe²⁺ and Fe³⁺ phases. These findings are compared with Mössbauer and magnetic susceptibility studies on fly ash samples of Panipat (India) thermal power plant reported earlier.     

N2O molecular tagging velocimetry

A new seeded velocity measurement technique, N₂O molecular tagging velocimetry (MTV), is developed to measure velocity in wind tunnels by photochemically creating an NO tag line. Nitrous oxide “laughing gas” is seeded into the air flow. A 193 nm ArF excimer laser dissociates the N₂O to O(¹D) that subsequently reacts with N₂O to form NO. O₂ fluorescence induced by the ArF laser “writes” the original position of the NO line. After a time delay, the shifted NO line is “read” by a 226-nm laser sheet and the velocity is determined by time-of-flight. At standard atmospheric conditions with 4% N₂O in air, ∼1000 ppm of NO is photochemically created in an air jet based on experiment and simulation. Chemical kinetic simulations predict 800–1200 ppm of NO for 190–750 K at 1 atm and 850–1000 ppm of NO for 0.25–1 atm at 190 K. Decreasing the gas pressure (or increasing the temperature) increases the NO ppm level. The presence of humid air has no significant effect on NO formation. The very short NO formation time (<10 ns) makes the N₂O MTV method amenable to low- and high-speed air flow measurements. The N₂O MTV technique is demonstrated in air jet to measure its velocity profile. The N₂O MTV method should work in other gas flows as well (e.g., helium) since the NO tag line is created by chemical reaction of N₂O with O(¹D) from N₂O photodissociation and thus does not depend on the bulk gas composition.     

Brewster window and windowless resonant spectrophones for intracavity operation

We report a new design for an acoustically resonant spectrophone well suited for intracavity operation with widely tunable lasers. Operation with Brewster angle windows or in a windowless mode is possible, and high quality factors (560 and 509, respectively) are achieved. Windowless operation permits continuous monitoring of ambient air. We discuss factors limiting the sensitivity, ∼10⁻⁷ cm⁻¹, and present a double chopping scheme capable of significantly reducing the acoustical background encountered in windowless operation. The sensitivity of the spectrophone's performance to misalignment is also examined.     

Mechanisms of coupling of aeroelectric and temperature fields in the lower atmosphere

Based on synchronous observations of the aeroelectric field and the air temperature, performed in August–October 2002 and June–September 2003 at the measuring facility of the mid-latitude geophysical observatory “Borok” (Yaroslavsl’ Region, Russia), we conclude that correlative relations exist between the aeroelectric-field intensity E and the air temperature T in the atmospheric surface layer. We reveal positive correlation between the temperature and electric-field variations under conditions of unstable stratification (late morning-day) and negative correlation under stable stratification (late evening-night). A simultaneous increase in the amplitude of pulsations of the electric field and the temperature occurs most frequently near the local midday. Intense variations in the electric field correspond to variations in the temperature field with a close time period. A positive temporal shift of variations in E with respect to variations in T, which reaches 40 min, is observed during enhanced temperature activity. The structure-temporal analysis of experimental data from remote sensing of the temperature and electric-field variations at five points is performed. We find simultaneous aeroelectric and temperature coherent structures accompanied by short-period pulsations of the field intensity and the air temperature in the atmospheric surface layer. We discuss possible mechanisms of coupling of the aeroelectric-field intensity and the atmospheric air temperature to describe their positive correlation under conditions of unstable stratification (late morning-day) and negative correlation in the late evening and at night. Enhancement of electric activity, which is stipulated by the intensification of turbulent convection and the formation of aeroelectric structures, seems the most significant process. With allowance for nonlocality of the electric field, this process can in particular explain a substantial lead of the aeroelectric-field perturbations compared with the correlated positive temperature perturbations. In this case, the formation of warm “quasi-front,” which is accompanied by the lifting of the near-surface air abundant in moisture and charged particles to the higher atmospheric layers, can play an important role. Other mechanisms of the field-temperature coupling take into account a decrease in the conductivity of near-surface air due to the condensation of water vapor during its cooling, as well as an increase in the mobility of light ions with increasing air temperature. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 1, pp. 35–52, January 2006.     

A new activity phase in Hongqi brown coal liquefaction

The higher coal conversion yield is associated with the greater γ-Fe/Fe_1−x S ratio in Hongqi brown coal liquefaction. The γ-Fe species possesses higher catalytic activity than Fe_1−x S. Formation of γ-Fe species during liquefaction is related with the dispersity of iron in the coal.     

基于SEM与FTIR研究改性钢渣/橡胶复合材料的热氧老化机理

钢渣是冶金工业中产生的主要固体废弃物,其产量约为每年粗钢产量的15%~20%。由于技术的局限,导致我国钢渣利用率较低,仅为年钢渣产量的10%,同时加之管理制度的不健全,导致钢渣大量露天堆放,对土地资源、地下水源,以及空气质量形成严重影响。面对上述问题,以热闷渣、电炉渣和风淬渣研发改性钢渣微粉,并且将改性钢渣微粉与复合橡胶进行复合制备改性钢渣/橡胶复合材料。依据《硫化橡胶或热塑性橡胶热空气加速老化和耐热试验》（GB/T3512—2014）对改性钢渣/橡胶复合材料进行热氧老化处理,采用平衡溶胀法测定改性钢渣/橡胶复合材料的交联密度,扫描电子显微镜（SEM）、热重分析仪（TGA）和傅里叶转换红外光谱仪（FTIR）分别测试其微观形貌、失重率和结构组成,从微观层面阐述改性钢渣/橡胶复合材料的热氧老化机理。结果表明在热氧老化前期老化作用在改性钢渣/橡胶复合材料表面,其内部以交联键形成反应为主;在热氧老化中期老化作用已经作用改性钢渣/橡胶复合材料内部,造成交联键断裂反应速度高于交联键形成反应速度,形成大量断裂交联键;在热氧老化后期由于改性钢渣/橡胶复合材料内部已经存在大量断裂交联键,导致主链及交联键断裂速度降低,交联键形成反应占优势。改性钢渣微粉以热闷渣（SiO₂含量高）为原材料,有利于形成聚合物大分子链贯穿炭黑网络的结构,提高综合性能,尤其是物理机械性与滞后性;以电炉渣、风淬渣（Fe₂O₃含量高）制备改性钢渣微粉,有利于热传导性能的改善,不仅提高改性钢渣/橡胶复合材料的耐热性,而且提高其硬度与脆性。热氧老化过程中改性钢渣/橡胶复合材料内部在橡胶分子链α-H上发生了不同程度的氧化反应,并在橡胶分子链周围生成了羟基、羧基和醇类化合物,双键烯氢含量降低。     

Electrical conductivity of Sr1−xTiO3−δ materialsmaterials

The high temperature conductivity of polycrystalline Sr_1−xTiO_3−δ samples in air was found to be lower than the conductivity of SrTiO₃ samples. However, the dependence of the electrical conductivity on the oxygen partial pressure showed that this trend can be reverted under reducing conditions. Both trends contradict the expected effects of A-site deficiency on the defect chemistry. Differences in average grain sizes give a plausible explanation for these findings. The dependence of the conductivity on the oxygen partial pressure suggests that p-type conductivity is dominant in air, for every sample, and one can thus assume that the number of grain boundaries plays a negative role on this contribution. Electrochemical permeability measurements confirmed that the ionic transport number of strontium titanate in air remains small. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

The oxidation of dodecane on a vanadium-molybdenum catalyst

The catalytic oxidation of dodecane by air oxygen on a mixed vanadium-molybdenum oxide (V₂O₅ · MoO₃, 40 mol % MoO₃) was studied over the temperature range 300–350°C. The reaction at 300–330°C occurred on oxygen vacancies with the rupture of C-H bonds and formation of α-acid. Oxidation above 350°C occurred with the splitting of the C-C bond and formation of two and more acids. Singlet oxygen ¹O₂ generated in the oxidation of oxide catalyst lattice oxygen participated in the reaction. A possible mechanism of the process was considered.     

X-ray surface radiolysis: Kinetics of the metal-organic interface formation

Grazing incidence x-ray irradiation of a Langmuir monolayer deposited at the interface between an aqueous silver salt solution and the air leads to the formation of a metallic silver layer of thickness about 4.5 nm, in agreement to the x-ray penetration depth at the air – water interface. Moreover using the scattering and fluorescence induced by the x-ray, we show that it is possible to follow the kinetics of formation of the layer. It appear that the silver layer is formed in two steps: first, the formation of small oriented cristallites, and second, the coalescence of the cristallites forming large plates.     

Repetitive hydrogen pellet injector utilizing a screw extruder

A new injector for the continuous formation of an unlimited supply of fuel pellets and their injection into the plasma of fusion reactors is described. A solid hydrogen rod of length in excess of 50 m has been extruded at an average rate of 20 mm/s, and more than a thousand pellets of diameter 2 mm have been formed from it in continuous operation at frequencies of 1 Hz and 2 Hz and have been accelerated to 0.6–0.8 km/s. Zh. Tekh. Fiz. 68, 117–120 (May 1998)     

Study of some dipolar complexes involving long chain aliphatic alcohols

The mechanism of 1:1 dipolar complexation of some long-chain aliphatic alcohols with chlorobenzene and acetic acids in a non-polar medium is studied. The interaction dipole moment △^→μ, the excess molar polarization ΔP and apparent complex formation constantK _app are evaluated following two independent methods. It is observed from the value of △^→μ that the complex formation is mostly due to polarization interaction and is of the same type as involving lower alcohols. ΔP andK _app are, however, of different nature compared to those in lower alcohols suggesting that the unlike molecules form relatively stable linear linkage resulting in antiparallel orientation prior to forming complexes.     

Investigation of the ozone formation process in a nanosecond microwave discharge in air and oxygen

Results are presented from an investigation of the dynamics of ozone formation in a freely localized discharge generated by a periodic train of 3-cm nanostructured microwave pulses in oxygen and air at a pressure p=3–30 Torr. Conditions for the efficient generation of ozone in air with the minimum production of nitrogen oxides are demonstrated experimentally. It is shown that when the microwave pulse repetition frequency is high, heating of the gas and the buildup of nitrogen oxides in the discharge in air reduce the ozone formation efficiency while under prolonged exposure the ozone formed initially is destroyed. The energy cost of forming ozone in oxygen and air is determined as a function of the microwave pulse length and repetition frequency and the gas pressure. The lowest energy cost of forming a single ozone molecule in these experiments is 16 eV per molecule for a discharge in air and 4 eV per molecule in oxygen. It was observed that circulating the gas through the discharge zone enhances th ozone formation efficiency. It is shown that there are optimal conditions for ozone formation as a function of the reduced electric field in the plasma. Zh. Tekh. Fiz. 67, 9–18 (March 1997)     

Thermodynamics of a gas-coal massif and a nonuniform gas distribution in a coal bed

The thermodynamic potential of a coal bed is calculated, and the gas pressure in the crack-pore system of the bed is shown to be nonuniformly distributed. This pressure is high in “weak“ regions in the bed, i.e., at the sites of a high porosity, low elastic moduli, and low solubility, as well as at high bearing pressure sites. All these phenomena are caused by the elastic interaction of a gas with a solid-state coal frame and the possibility of the formation of a solid solution in the coal. The relative increase in the gas pressure at these sites is estimated. The results obtained can be used to predict the localization of explosive and outburst regions in coal beds.     

Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

Changes in individual groups of paramagnetic centers after reduction and reductive butylation of Polish flame coal (70.8 wt.% C) were studied by electron paramagnetic resonance (EPR) spectroscopy. The modern method of reductive butylation of coal in a potassium-liquid ammonia system was used. This process increases the solubility of coal in organic solvents. Microwave saturation of EPR spectra was applied to test the spin-lattice relaxation in coal. The measured EPR spectra were a superposition of broad (ΔB _pp, 0.42–0.49 mT) and narrow (ΔB _pp, 0.09–0.13 mT) Lorentz lines. Paramagnetic centers located in simple and multiring aromatic structures were responsible for the broad and narrow lines, respectively. Microwave saturation indicates that slow and fast spin-lattice relaxation processes are characteristic for these two types of structures in the original coal. A decrease of the microwave power saturation of the broad Lorentz line after a single reduction of coal was observed. It increased for both 4 times reduced coal and reductively butylated coal. As the result of multiple reduction and butylation, spin-lattice relaxation processes in simple coal aromatic units were fastened. The narrow Lorentz lines of both 4 times reduced and reductively butylated coal were saturated and the spin-lattice relaxation time increased.     

Plasma formation by high-repetition rate pulsed periodic laser irradiation of metals in air at atmospheric and reduced pressures

High-speed spectroscopy with spatial and temporal resolution is used to determine the basic plasma parameters and to examine the shift from an air plasma to an erosion plasma during multipulse laser irradiation of various metals at repetition rates ranging from 5 to 50 kHz with irradiances q > 2∙10⁸ W/cm². The formation of a distinctive surface plasma structure is observed which (a) facilitates the expulsion of the shielding layer of "air" plasma produced during the first of a series of laser pulses by vapor from the target and (b) inhibits the propagation of a metal vapor plasma front into the air during the subsequent pulses.     

Development of conductive transparent indium tin oxide (ITO) thin films deposited by direct current (DC) magnetron sputtering for photon-STM applications

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10^-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range 3.0–5.7×10^-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities in the range 2.9–4.0×10^-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C, and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated. Received: 10 July 2000 / Accepted: 27 October 2000 / Published online: 9 February 2001