Analysis of the microelement content in coal

Microelements are present in coal in its organic matter, mineral impurities, and biochemical material. The microelement content in these components will be different, on account of the different forms of migration and access to the organic system. Estimation of the microelement content in the basic components of the coal is of interest in terms of assessing the rare-metal content in coal fields and extracting those metals. Statistical analysis of the microelement contents in different components of the coal is proposed.     

煤制烯烃企业全厂能量系统优化策略及应用

为了实现煤制烯烃企业全厂能量系统优化,提出了煤制烯烃企业全厂能量系统基于单元、子系统和全局划分的渐进协同优化策略,包括全厂用能状况分析、工艺装置用能及换热网络优化、低品位热回收和优化利用、全厂蒸汽动力系统优化等步骤。应用上述优化策略,对某60万t/a煤制烯烃企业全厂能量系统优化进行研究,得到全厂各单元能耗分布,提出了甲醇合成和甲醇制烯烃单元换热网络优化、全厂蒸汽动力系统降低蒸汽减温减压量及低品位热合理匹配利用等节能方案,理论上可以提高全厂系统能效3%以上,年节约标煤10万t以上,投资回收期小于1 a。     

Evaluation of lignin and cellulose contributions to low-rank coal formation by alkaline cupric oxide oxidation

Oxidation with alkaline cupric oxide has been combined with solid-state ¹³C-n.m.r. spectroscopy to evaluate the cellulose and lignin input to the formation of low rank coals. Model studies carried out on lignin-cellulose mixtures, carbonified cellulose, synthetic coals and synthetic humic acids (melanoidins) have established m-hydroxybenzoic acid as a source indicator for cellulose. This product has been found specifically in the oxidation of bio- and geo-macromolecules containing cellulose and/or thermally altered cellulosic material and is chemically distinct from the characteristic oxidation products of lignin-derived materials. Systematic changes in the distribution of the major oxidation products from lignin provide a chemical fingerprint which, in general, can be utilized to trace the thermal history of the sample. Analysis of two lignite coals from the northern hemisphere has demonstrated their predominantly lignitic origin. On the other hand, a Victorian brown coal (pale lithotype) sample is shown to contain a significant amount of highly transformed carbohydrate materials which are presumably incorporated into the macromolecular structure as humic acid derivatives.     

Profile-Icp法测定精盐水中的微量元素

详细叙述了采用Profile-Icp发射光谱仪测定二次精盐水中Ca、Mg、Sr、Ba、Fe、Ni、Al、Si等元素的方法,讨论了分析时应选择的工作条件和参数,并在所选的工作条件下测试,验证了该方法的准确率、精密度符合痕量分析的要求。     

Ignition of single coal particles in high-temperature oxidizers with various oxygen concentrations

In this investigation, coal pellets were combusted using a high temperature oxidizer with varying oxygen concentration, using a small scale batch reactor able to preheat the oxidizer to 1273 K. In base of the experimental results, the influence of oxygen concentration on the ignition mechanism, the solid temperature inside the particle at the moment of ignition, the mass lost at the moment of the ignition and ignition time is analyzed and discussed. A theoretical basis for the division of the conditions tested into three ignition regimes is developed and a formula for the prediction of the ignition time directly from the material and oxidizer temperature and oxygen concentration is proposed.     

影响对作物供应中微肥的因素及中微肥在农业生产中的应用实例

开发与应用中微肥和硅肥是推广科学用肥,建设现代化农业的重要内容之一.阐述影响土壤对作物供应中微量元素的因素;国内中微肥的使用概况及其在农业中的应用实例.中微肥将在我国肥料产业结构调整中占有重要位置,有广阔的市场开发空间.     

Lipophilic contributions to the solvatochromism of analogous betaines

A pair of solvatochromic phenolate betaines that differed only in their lipophilicity was synthesized. Their solvatochromic responses in pure solvents, in a DMSO–MeOH solvent mixture as well as in micellar solutions were different, an observation which confirmed the fact that sensor lipophilicity contributes to the interpretation of solvatochromism. Quantum mechanical calculations reproduced the observed spectral differences. Molecular dynamics simulations shed light on the solute–solvent interactions responsible for their differences in solvent mixtures.     

Molar group contributions to the heat of combustion

Experimental results for the gross heat of combustion of over 140 commercial and developmental polymers and small molecules of known chemical structure were used to derive additive molar group contributions to the heat of combustion. The materials examined contained carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, chlorine, fluorine and silicon in linear, branched and cyclic structures. Values for the molar group contributions were summed and divided by the molecular weight of the molecule or polymer repeat unit to yield the gross heat of combustion as determined by oxygen bomb calorimetry. This new method provides an accurate single step method for calculating the heat of combustion. The average relative error of the calculated gross heats of combustion is 2.8%. Published in 2002 by John Wiley & Sons, Ltd.     

Changes in trace element concentrations and catalyst activity during the hydrocracking of a coal extract solution

A hydrocracking rig has been constructed which involves the passing of coal-derived liquids and hydrogen over a trickle bed packed with a nickel oxide/molybdenum oxide catalyst. The ash and trace metal levels have been measured, before and after hydrocracking, and their variation with catalyst lifetime has been assessed. Al, Ca, Fe, Mg, Mn, K, Si, Na and Ti levels have been determined by a.a.s. and considerable reductions have been observed for Fe, Mg, Mn and Ti after hydrocracking. The ash level of hydrocracked extract increases for the first 50 h and then stabilizes at about 60% of the feed level. Metal levels determined for the catalyst itself show an accumulation of all the metals under consideration, especially for the sections of the catalyst which were hottest. Overall catalytic activity is not seen to decrease markedly but the ability of the catalyst to produce lower boiling material is considerably reduced after only 25 h. Comparisons between catalyst activity and metal deposition are made.     

ICP-AES同时测定二次盐水中微量元素

介绍了以ICP-AES采用标准加入法测定二次盐水中Ca、Mg、Fe等8种微量元素的方法,优化了工作参数,利用国家标准物质验证了方法的准确度,其相对标准偏差均小于2.00%,标准回收率为94.1%~108.6%。     

不同氧浓度下煤挥发分燃烧的化学动力学研究

燃煤有机污染物对人类健康和生态环境存在严重危害,而O₂对火焰中有机产物的形成具有明显的调控作用。鉴于煤挥发分燃烧是燃煤过程中至关重要的一环,本文以煤热解气为燃料,通过数值模拟研究了氧化剂侧O₂浓度对对冲扩散火焰中碳氢产物生成特性和机制的影响。结果表明,O₂浓度升高促进了O和OH的生成,进而提高H浓度,突显了含H和OH参与的反应的重要性。此外,乙炔(C₂H₂)、丙炔(PC₃H₄)、炔丙基(C₃H₃)、乙烯基乙炔(C₄H₄)、苯(C₆H₆)和萘(C₁₀H₈)的浓度均增大。增加O₂浓度促进了C₂H₂向PC₃H₄的转化,并使得C₃H₃更倾向于转化为丁二烯(C₄H₆),而富烯更倾向于通过苯基(C₆H₅)生成C₆H₆,因此C₆H₅作为C₆H₆前体的地位被加强。     

不同氧浓度下煤挥发分燃烧的化学动力学研究

燃煤有机污染物对人类健康和生态环境存在严重危害,而O₂对火焰中有机产物的形成具有明显的调控作用。鉴于煤挥发分燃烧是燃煤过程中至关重要的一环,本文以煤热解气为燃料,通过数值模拟研究了氧化剂侧O₂浓度对对冲扩散火焰中碳氢产物生成特性和机制的影响。结果表明,O₂浓度升高促进了O和OH的生成,进而提高H浓度,突显了含H和OH参与的反应的重要性。此外,乙炔(C₂H₂)、丙炔(PC₃H₄)、炔丙基(C₃H₃)、乙烯基乙炔(C₄H₄)、苯(C₆H₆)和萘(C₁₀H₈)的浓度均增大。增加O₂浓度促进了C₂H₂向PC₃H₄的转化,并使得C₃H₃更倾向于转化为丁二烯(C₄H₆),而富烯更倾向于通过苯基(C₆H₅)生成C₆H₆,因此C₆H₅作为C₆H₆前体的地位被加强。     

Molar group contributions to polymer flammability

The specific heat‐release rate is the molecular‐level fire response of a burning polymer. The Federal Aviation Administration obtains the specific heat‐release rate of milligram samples by analyzing the oxygen consumed by the complete combustion of the pyrolysis gases during a linear heating program. Dividing the specific heat‐release rate (W/g) by the rate of the temperature rise (K/s) of a sample during a test gives a material fire parameter with the units (J/g K) and significance of the heat (release) capacity. The heat‐release capacity appears to be a true material property that is rooted in the chemical structure of the polymer and is calculable from additive molar group contributions. Hundreds of polymers of known chemical compositions have been tested to date, providing over 40 different empirical molar group contributions to the heat‐release capacity. Measured and calculated heat‐release capacities for over 80 polymers agree to within ±15%, suggesting a new capability for predicting flammability from the polymer chemical structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 548–563, 2003     

Mass spectrometric contributions to problems related to the chemistry of atmospheres

Recent mass spectrometric studies of species and processes relevant to the chemistry of atmospheres are reported. New species have been detected, including HO(3); a stratospheric reservoir of OH radicals; the [H(2)O(+)O(2)(-)] charge transfer complex, central to the atmospheric photonucleation theory; and the OSOSO oxide and its cation, likely present in the Io's atmosphere. As to ionic processes, a new route to tropospheric N(2)O in air ionized by lightning and coronas is reported, as well as the complex chemistry promoted by ionization of ozone/freon and ozone/carbonyl sulfide mixtures and the formation of O(5)(+), relevant to the problem of (18)O excess in stratospheric ozone.     

Pyrolysis of subbituminous coal in relation to in-situ coal gasification

Pyrolysis of Roland Seam (Wyodak) subbituminous coal has been investigated from 383 to 1273 K in an inert gas at 0.1 MPa (1 bar). The gas, liquid (condensibles at 0 °C) and solid products were analysed and characterized. Evolution of the major noncondensible gas products was measured quantitatively. By measuring the rate of gas evolution under linear heating conditions the effective activation energy and kinetic frequency factor for release of each gas were determined. These activation energies range from about 80 to 150 kJ/mol. Most of the liquid product was released between 570 and 770 K and was approximately 75% water and 25% organic tar phase. The composition of the organic tar phase was characterized by its elemental composition, boiling-point range, and chromatographic ‘finger-print’. The effect of temperature on the structure of char was determined by analysing changes in elemental composition, surface area, and electrical conductivity.     

The effects of coal dust concentrations and particle sizes on the minimum auto‐ignition temperature of a coal dust cloud

Flash fires and explosions in areas containing an enriched combustible dust atmosphere are a major safety concern in industrial processing. An experimental study was conducted to analyse the effects of atmospheric coal dust particle sizes and concentrations on the minimum auto‐ignition temperature (MAIT) of a dust cloud. Two different coal samples from Australian coal mines were used. The coal dust particles were prepared and sized in 3 ranges, of below 74 μm, 74 to 125 μm and 125 to 212 μm, by using a series of sieves and a sieve shaker. A humidifier was used to increase the moisture content of the particles to the required level. All the experiments were conducted in accordance with the ASTM E1491‐06 method in a calibrated Goldbert‐Greenwald furnace. The results from this study indicate that coal dust properties, such as the chemical nature (H/C), concentration, particle size (D₅₀), and moisture content, impact on the MAIT. For coal dust concentrations less than 1000 g.m^?3, the MAIT decreases with increasing coal dust concentrations. On the other hand, for low concentrations of 100 to 15 g.m^?3, the MAIT becomes more reliable for particle size D₅₀ rather than for volatile matters.     

Maximum solid concentrations of coal water slurries predicted by neural network models

The nonlinear back-propagation (BP) neural network models were developed to predict the maximum solid concentration of coal water slurry (CWS) which is a substitute for oil fuel, based on physicochemical properties of 37 typical Chinese coals. The Levenberg-Marquardt algorithm was used to train five BP neural network models with different input factors. The data pretreatment method, learning rate and hidden neuron number were optimized by training models. It is found that the Hardgrove grindability index (HGI), moisture and coalification degree of parent coal are 3 indispensable factors for the prediction of CWS maximum solid concentration. Each BP neural network model gives a more accurate prediction result than the traditional polynomial regression equation. The BP neural network model with 3 input factors of HGI, moisture and oxygen/carbon ratio gives the smallest mean absolute error of 0.40%, which is much lower than that of 1.15% given by the traditional polynomial regression equation.     

Pseudocapacitive contributions to electrochemical kinetics in NiOx electrochromic anodes

Because of its ability to change optical absorption dynamically by applied electric field, nickel oxide (NiO) is a promising anodic material in smart windows, which can improve energy conversion efficiency in construction buildings. Although many works have achieved high electrochromic performance with different method. The underlying mechanism is still not fully investigated. In this article, we prepared the NiO films with large specific surface area and high stability by electron beam evaporation. X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to figure out the surface morphology and composition of as-deposited films. Afterwards, the electrochemical properties and optical performance of the prepared NiO films were investigated. On this basis, the origin of surface charge was fully analyzed by cyclic voltammetry and diffusion coefficient test. These experimental and theoretical results firmly confirm that both the surface reaction and capacitive effect bring about the excellent EC performance in NiO films. These results not only provide clear evidence about electrochemical kinetics in NiO films, but also offer some useful guidelines for the design of EC materials with higher performance and longer stability.     

Somein situ STM contributions to the characterization of electrochemical systems

We present a critical review on the use of STM as anin situ technique to characterize electrochemical systems based on the work performed in our laboratory. Contributions ofin situ STM studies include: (i) atomic resolution of electrodeposited lead on graphite; (ii) imaging of modifications on metallic electrode surfaces induced by electrochemical oxidation-reduction processes; (iii) imaging of corrosion process on aluminium and Al-Ta alloy electrodes in NaCl solution; (iv) characterization of semiconductor-solution interfaces. These studies allowed: (a) establishment of STM as a technique which, for some systems, yields atomic resolution of metallic surfaces in air and in solution; (b) establishment of a mechanism for the electrochemical growth of oxide films on metal electrodes; (c) establishment of a corresponding mechanism for the reduction of those electrochemically grown oxide films; (d) direct monitoring of corrosion processes on a scale of nm to m; and (e) determination of the presence of surface states and their energy position at the semiconductor-solution interfaces.This paper is dedicated to Professor Brian E. Conway on the occasion of his 65th birthday and in recognition of his outstanding contribution to electrochemistry.