Molecular probe chromatography of selected lignites

The properties of selected lignites have been studied by a molecular probe technique using several probes. Following the sorption of air components and carbon dioxide at ambient temperature, interesting flow disturbance peaks were observed due to swelling and shrinkage of the packing mass. Both the retention and peak asymmetry of carbon dioxide increase significantly upon column conditioning. Irrespective of their chemical identity, the probe molecules are sorbed on the surface of lignite by an adsorptive mechanism alone up to 175 °C. The probes are retained in the column both by specific and non-specific interaction forces, the former being very large. Water and methanol sorbed in monolayer or submonolayer coverage can only be eluted easily at a temperature of ≈ 175 °C. As well as hydrogen bonding, dative linkages of polar ligands with transition elements associated with brown coal have also been considered to contribute to the observed retention behaviour. The column permeability may depend on the sulphur content of lignites. The very large stationary phase non-equilibrium coefficient for carbon dioxide mass transfer has been ascribed to the slow interfacial mass transport within the micropores.     

Chlorination kinetics of pyrite mineral in two Turkish lignites

The kinetics of the chlorination of pyrite in two Turkish lignites in water and water-carbon tetrachloride media at ambient pressure ( 610 mm Hg) are investigated. The effects of speed of stirring (5–20 s⁻¹), particle size (74–88, 150–180 and 250–425 μm), temperature (13–70°C) and reaction time (0–18 000 s) were studied. The experimental data were analyzed on the basis of the unreacted shrinking core model. The fine pyrite particles are assumed to be embedded inside the coal particles. The rate-controlling step was found to be diffusion of chlorine through the ash (the coal matrix). The activation energies were calculated as 25.1 kJ mol⁻¹ for Dada i coal in water medium and 25.0 kJ mol⁻¹ for Mengen coal in water-carbon tetrachloride medium.     

Petrographic composition and liquefaction behaviour of North Dakota and Texas lignites

Two US lignites (from Texas and North Dakota) were fractionated by density with appropriately prepared mixtures of liquid halogenated and non-halogenated hydrocarbons. Petrographic analyses confirmed that the procedure resulted in density fractions enriched in specific macerals. Liquid yields obtained upon solubilization at 430 °C and 5.5 MPa hydrogen pressure decreased with increase in the density fraction for both lignites. On plotting the total solubilities of lignites and their density fractions versus their huminite contents a reasonably good linear correlation was obtained (particularly for North Dakota lignite). It is tentatively concluded that in North Dakota lignite, as opposed to Texas lignite, macerals other than huminite did not significantly contribute to generation of liquid products.     

Microbial desulphurization of lignites by a thermophilic bacterium

As a possible means of abatement of air pollution the use of thermophilic thiobacilli in lignite desulphurization has been investigated in lab-scale batch experiments and 50% organic sulphur 58% total sulphur removal has been achieved in 10% lignite slurries at 50 °C.     

Enhanced reactivity of some lignites by deashing pretreatment in hydrogen-transferring liquefaction under atmospheric pressure

The reactivities of five lignites were studied in the hydrogen-transfer liquefaction process undet atmospheric pressure, using a hydrogenated petroleum pitch (HA240). Although asphaltene yield from Yallourn brown coal was as high as 70%, other lignites showed inferior yields. Pretreatment in boiling 0.4N hydrochloric acid enhanced the liquefaction reactivity significantly to the extent that the asphaltene yield from Berga lignite increased to as much as 70%.     

A new approach for the prediction of ash fusion temperatures: A case study using Turkish lignites

Prediction of ash fusion temperatures by using the chemical composition of the ash has previously been conducted only with linear correlations. In this study, a new technique is presented for predicting the fusibility temperatures of ash. Non-linear correlations are developed by using the chemical composition of ash (eight oxides) and coal parameters (ash content, specific gravity, Hardgrove index and mineral matter content). Regression analyses are conducted using information for Turkish lignites. Regression coefficients and variances of non-linear and linear correlations are compared. The results show that the non-linear correlations are superior to linear correlations for estimating ash fusion temperatures.     

Desulphurization of some low-rank Turkish lignites with crude laccase produced from Trametes versicolor ATCC 200801

In this paper, data obtained during the oxidative desulphurization of some low-rank Turkish lignites with crude laccase enzyme produced from Trametes versicolor ATCC 200801 are presented. In order to optimize desulphurization conditions, effects of incubation time, pulp density, incubation temperature, medium pH, and also lignite source on the desulphurization have been examined. The values for incubation period, pulp density, temperature and pH in optimum incubation condition were found as 30 min, 5%, 35 °C, and pH 5.0, respectively. Under optimum conditions, treatment of coal samples with crude laccase has caused nearly 29% reduction in their total sulphur content. During the study, the rate of desulphurization of coal sample provided from Tunçbilek with crude laccase was found to be relatively higher than the other examined coal samples. Results of analytical assays have indicated that the treatment of coals with crude laccase has caused no change in their calorific values but reduced their sulphur emissions. 35%, 13%, and 25% reductions of pyritic sulphur, sulphate and organic sulphur in a period of 30 min were achieved, for a particle size of 200 μm under optimal conditions with enzymatic desulphurization. Also, statistical analyses such as Tukey Multiple Comparison tests and ANOVA were performed.     

The effect of cation content of some raw and ion-exchanged Victorian lignites on their equilibrium moisture content and surface area

Six Victorian lignites of known inorganic content have been water and acid-washed. The acid-washed form of one of these lignites (LYLA(R)) was subsequently exchanged with Na, Mg, Ca and Al salts. The equilibrium moisture contents (EMC) of all samples have been determined across a range of relative vapour pressures (RVP) extending previous observations in the case of a single lignite exchanged with a series of cations. Previous measurements for a single lignite exchanged with a series of cations have only been made at a single RVP. The effects of the different metal cations on the EMC values varied depending on the RVP. The surface areas determined by CO₂ adsorption also showed an effect of cation content.     

地球化学参数在沉积古盐度中的应用

在对沉积物进行沉积古盐度分析时,微量元素分析能够起到很好的作用,它们对沉积盐度的变化具有很高的灵敏度,此外稀土元素具有很好的稳定性,能够保存沉积时的古盐度信息,生物标志化合物是生物的化学化石,具有稳定的结构,不易受成岩作用影响,能够记录生物沉积时的古盐度。通过阅读大量的文献,系统的总结了主微量元素、稀土元素和生物标志化合物在不同沉积盐度中的特征及其地质应用。对于沉积相分析不明确的地层,利用地球化学参数能够更直观地分析出沉积盐度。但沉积物在沉积过程中很容易受其他因素影响,因此在利用地化参数对沉积盐度判别时还应与地质背景、岩性岩相等相结合,以便能最大限度反映出沉积时的古盐度。     

Hydrogenation of pitch and lignite chars under pressure in the presence of pyrite

The influence of pyrite or one of its reduced forms on the hydrogenation kinetics of pitch and lignite chars is investigated. The initial chars from pitch and lignite are of low and high reactivity respectively. The experiments were carried out in a symmetrical thermobalance under pressure ranging up to 5 MPa of hydrogen and 950 °C. Addition of pyrite enhanced the reactivity of the pitch char but not that of the lignite char.     

安达次洼陷地区营三段火山岩地球化学分析

根据安达次洼陷地区7口井营三段的火山岩地球化学数据对火山岩岩性进行划分,并且进一步划分出火山岩系列加以分类命名,最后对该区火山岩形成环境进行简要概括。     

古岩溶的识别标志及地球化学研究方法述评

通过检索国内外有关古岩溶的文献,列举了古岩溶的主要识别标志。在此基础上,对国内外关于古岩溶和古岩溶岩研究的方法和技术手段进行总结,主要讨论了古岩溶岩的地球化学研究方法。通过古岩溶岩中稀土元素、微量元素地球化学特征分析,得出古岩溶形成过程中古流体性质、古水文条件等,对预测古岩溶储层以及与古岩溶有关的矿床的分布规律提供地球化学信息,从而有效地、经济地勘探和开发油气田和相关矿产资源。     

Water quality of Vistonis Lagoon, Northern Greece: seasonal variation and impact of bottom sediments

The aim of this study is to present the seasonal variation of nutrients in the water column and the bottom sediments of Vistonis Lagoon, a hypereutrophic Mediterranean coastal lagoon located in Northern Greece, and to estimate the impact of bottom sediments on the water quality of this lagoon. Nutrient concentrations in the water column and in bottom sediments were determined throughout seven seasonal sampling cruises from May 2003 to October 2004. Physicochemical parameters, such as transparency, temperature, salinity, pH and dissolved oxygen, were measured in situ in the water column using suitable equipment. Nutrient concentrations in bottom water were found generally higher than those in surface water. Nitrogen, mainly as nitrates, and phosphorus are released into the water column from the bottom sediments, especially during the summer period. Anoxia in the bottom water, as well as resuspension of the sediments are the main factors affecting nutrient internal loading in this lagoon. An approximate calculation showed that total phosphorus release was about 80 mg m⁻² d⁻¹ for the period March–August 2004. Vistonis Lagoon restoration will be possible only through the minimization or elimination of both external and internal nutrient loadings.     

柴达木盆地北缘马北油田原油地球化学特征

对马北油田各个构造原油样品的生物标志物进行了系统的分析,研究了它们的地球化学特征。生物标志物的分布和组成特征指示马北油田原油形成于弱还原淡水湖相成油环境;具有陆源高等植物和低等水生生物双输入的特征,为成熟原油,来源于侏罗系淡水湖相生油岩。马北2井原油出现高丰度25-降藿烷系列与完整链烷烃系列并存的现象,说明该原油遭受过生物降解作用改造,该构造至少经历了2期油气充注。     

Chemical investigation of lignite samples and their ashing products from Kardia lignite field of Ptolemais, Northern Greece

Twenty-six lignite samples were collected from the Kardia lignite field (Ptolemais, Greece). Ash content, moisture and CO₂ were determined. The lignite samples were heated at 900 °C producing 26 ash samples. The chemical composition (major and trace elements) both of the lignite samples and ash products was determined using INAA, ICP-OES and ICP-MS. CaO, SiO₂ and Al₂O₃ are the dominant oxides both in lignite and ash samples. A relative decrease of SiO₂ and Al₂O₃ as well as an increase of CaO was noticed in the deeper lignite samples. Sr, Cr, Ni, V and Ba were found to be the most abundant both in lignite and ash samples. Sr displays a relative increase while Ni and Cr decrease with depth in the lignite samples. In the ash samples, Ni shows the most obvious decrease with depth.     

Effectiveness of Polish lignites as reburn fuels

The effectiveness of four Polish lignites as reburn fuels was studied in the laboratory-scale drop-tube furnace. The established rank of the lignites and chars used correlates with concentration of calcium in lignite. A comparison of the reburning effectiveness of partially devolatilized chars with that of the parent lignites showed that the parent lignites achieved a higher NO reduction than the chars.     

Desulfurization of a Turkish lignite at various gas atmospheres by pyrolysis. Effect of mineral matter

An investigation was made of the removal of pyritic and organic sulfur by pyrolysis at ambient pressure of a Turkish lignite under nitrogen and carbon dioxide atmospheres and the effect of mineral matter on the sulfur removal in pyrolysis of HCl and HCl/HF-treated coal under carbon dioxide atmosphere. Results obtained indicated that both pyritic and organic sulfur removal increased with increasing pyrolysis temperature. The pyrolysis in carbon dioxide atmosphere had more effect on the organic sulfur removal at high temperatures. As a consequence of treatment of coal with HCl, pyritic sulfur removal increased but organic sulfur removal decreased. This implies that the removal of carbonates from coal negatively affects the organic sulfur removal. The observed decrease in organic sulfur removal may be related to the decrease in pyrolytic conversion. It was observed that HCl/HF treatment has an increased effect on the pyritic removal and organic sulfur removal during pyrolysis. The increase in organic sulfur removal after HF-treatment therefore might be due to the removal of clay minerals in the raw coal structure. In addition, it may be said that the presence of silicate minerals in the coal matrix can be induced that the easily removable organic sulfur compounds are converted to thermally stable and non-removable organic sulfur compounds (thiophenic or condensed thiophenic compounds) at these temperatures. Increase in the pyritic sulfur removal of HCl-treated and HCl/HF-treated coal samples may be attributed to the fact that increase of mass and/or heat transport in comparison with untreated coal as a result of elimination of mineral matter.     

Gel permeation chromatography applied to the study of the nitrohumic acids from coal

Gel permeation chromatography on Sephadex (G-types) was applied to nitrohumic acids (NHA) from lignites. Deionized water and TRIS (Tris-hydroxymethylaminomethane) buffer were tested as eluents. Deionized water provided the same number of fractions and better resolution than TRIS. In both cases, interactions between the gel matrix and the NHA occurred. Five NHA fractions were obtained and characterized by elemental and spectral analysis, which showed significant differences between them. Molecular weights of the fractions, calculated from Cameron's calibration for soil humic acids, are < 9000 or > 100 000 with no significant fractions having molecular weights in the range 9000–100 000.     

Geochemical distribution of trace elements in coal: modelling and environmental aspects

The present work consists of verifying a theoretical model based on mass distribution of trace elements in coal. Many versions of the model were tested using 42 elements in 8 different coals (5 American, 2 Brazilian and 1 Spanish). The calculated partial concentrations of elements in organic and inorganic (sulfide, carbonate and sulfate) fractions were obtained. These results could be summarised as following: B, Be, Br, Ge and V are associated to organic coal fraction while As, Cd, Co, Cu, Dy, Hg, Lu, Mo, Ni, Pb, Se, W and Zn occur mainly in sulfide minerals and Ba, Cr, Cs, Ga, Mn, Rb, Sb, Sn, Sr, Ta, U and Zr are distributed in the non-sulfide fraction. Finally, the volatility of trace elements was estimated using the calculated partial concentrations in organic and sulfide fractions. The applicability of this parameter in related environmental problems was discussed, comparing model results with experimental and theoretical literature data of the mobilisation of these species into atmosphere.     

Demineralisation of lignites by single and successive pretreatment

In this study, two Turkish lignites (Bolu-Mengen, Kütahya-Tunçbilek) were treated under atmospheric and reflux conditions with 10-30% NaOH, 10% HCl and 10% H₂SO₄ solutions, singly and/or successive treatments to determine the effects of this treatment on the mineral matter and acidic functional groups. Characterisation of the treated and untreated samples was by Fourier transform infrared spectroscopy. The process of successive pretreatment was found to be more effective than single steps in terms of demineralisation and removal of carboxylate structures. During NaOH treatment, the first of successive steps, salts soluble in acid but not in water were determined. In successive demineralisation steps with 30% NaOH and 10% HCl, a low level of 3.3% ash was obtained for the Tunçbilek lignite. In addition, during the pretreatment, most of the Ca and K were exchanged with Na.