Preparation of magnetically separable mesoporous activated carbons from brown coal with Fe3O4

Magnetically separable mesoporous activated carbon was prepared from brown coal in the presence of Fe3O4 as a bi-functional additive.Magnetic activated carbon(MAC)was characterized by lowtemperature nitrogen adsorption,scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and vibrating sample magnetometry(VSM).The evolution behaviors and transition mechanism of Fe3O4 during the preparation of MAC were investigated.The results show that prepared MAC with 6 wt%Fe3O4 addition having a specific surface area and mesopore ratio of 370 m^2·g^-1 and 55.7%,which meet the requirements of adsorption application and magnetic recovery.Highly dispersed iron-containing aggregates with the size of 0.1 lm in the MAC were observed.During the preparation of MAC,Fe3O4 could enhance the escape of volatiles during the carbonization.Fe3O4 could also accelerate burning off the carbon wall during activation,which leads to enlarging micropore size,then resulting in the generation of mesopore and macropore.As a result,a part of Fe3O4 converted into FeO,FeOOH,a-Fe,c-Fe,Fe2SiO4 and compound of Aluminum-iron-silicon.The prepared activated carbon,which was magnetized by both of residual Fe3O4,reduced a-Fe and c-Fe,can be easily separated from the original solution by external magnetic field.

Batch methanogenic fermentation experiments of wastewater from a brown coal low-temperature coke plant

Coke plant effluents with high contents of organic compounds are mainly treated by biological aerobic fermentation after physical pre-treatment. In this study, a brown coal condensate wastewater from a low temperature coking process was fermented under methanogenic conditions in discontinuous experiments. By this fermentation, acetate, propionate, and the main polyphenolic compounds （catechol, resorcinol and hydroquinone） were degraded to a level below the detection limit. The COD was reduced by 72% with a residual concentration of 2.1 g/L. This anaerobic fermented wastewater had a residual BOD5 of 0.66 g/L and 2.2 L CH4 were formed per litre of wastewater. An abiotic pre-treatment for this wastewater with air had a negative effect on the COD reduction and decrease of colour on the methanogenic fermentation due to the autoxidation of polyphenolic compounds to humic-like compounds. This study showed that methanogenic fermentations in the treatment sequence of brown coal coking wastewaters could reduce energy consumption for aeration in further treatment processes and had the potential for a better effluent quality due to a less formation of recalcitrant humic-like compounds.

Gasification kinetic modelling of Victorian brown coal chars and validity for entrained flow gasification in CO_(2)

The gasification kinetic modelling of two Victorian brown coal(Yallourn and Maddingley)chars and the validity for entrained flow gasification were investigated in this study.The study was conducted in a thermogravimetric analyzer(TGA)at 750–1100℃,30%–90%CO_(2)concentration using different char particle sizes within 20–106 mm.It was found that random pore model and modified volumetric model are applicable for TGA results,but volumetric model and grain model are not.The effect of particle size under106 mm on gasification rate is very limited.Activation energies of Maddingley char and Yallourn char in CO_(2)gasification are 219–220 and 197–208 k J/mol,respectively.The pre-exponential factors are in the same order of magnitude,and they increased as particle size decreased.A mathematical model was developed to predict carbon conversion over time for entrained flow gasification of Victorian brown coal chars at 1000–1400℃.

Changes in char reactivity due to char-oxygen and char-steam reactions using Victorian brown coal in a fixed-bed reactor

This study was to examine the influence of reactions of char–O2and char–steam on the char reactivity evolution.A newly-designed fixed-bed reactor was used to conduct gasification experiments using Victorian brown coal at800 °C. The chars prepared from the gasification experiments were then collected and subjected to reactivity characterisation(ex-situ reactivity) using TGA(thermogravimetric analyser) in air. The results indicate that the char reactivity from TGA was generally high when the char experienced intensive gasification reactions in 0.3%O2in the fixed-bed reactor. The addition of steam into the gasification not only enhanced the char conversion significantly but also reduced the char reactivity dramatically. The curve shapes of the char reactivity with involvement of steam were very different from that with O2 gasification, implying the importance of gasifying agents to char properties.

Computer controlled measurement of spontaneous combustion in coal stockpiles of the Western Lignite Corporation, Turkey

The spontaneous combustion event in coal stockpiles is inevitable when appropriate environmental conditions are available. The objective of a computerized measurement system is to measure temperature changes existing in a coal stockpile. In order to achieve this intention, the electrical signal conversion of temperatures sensed by 20 temperature sensors placed in certain points inside the coal stockpile, the transfer of these electrical signals into computer media by using analogue-digital conversion unit after applying necessary filterization and upgrading processes and the record of these information into a database in particular time intervals are provided. Afterwards, the diagrams of these time-temperature data are plotted. With the help of these graphs, the competent company will be able to examine the behavior of coal stockpiles in terms of spontaneous combustion and take necessary precautions against self-combustion beforehand.

Late Cretaceous-Paleogene Palynostratigraphy from the Arkhara-Boguchan Brown Coal Mine of Zeya-Bureya Depression, Russia

A well-preserved Late Cretaceous-Paleogene palynological flora from the middle member of the Tsagajan Formation and the upper member of the Tsagajan Formation including the Kivda Beds is reported for the first time from the Arkhara-Boguchan brown coal mine, southeastern part of the Zeya-Bureya Basin. Four palynocomplexes were established for the Cretaceous-Tertiary transition. The climate and phytocoenoses were also analyzed,based on the detailed palynological data. The results are coincident with those of mega-flora studied by Akhmetiev et al. (2002).

Stratigraphy of southeastern flanks of Raichikhinsk brown coal field (Zeya-Bureya sedimentary basin)

The results of the palynologic and paleobotanic analyses have allowed determining the Paleocene (including Danian) and Eocene deposits in the series of coal-bearing sediments of southeastern flanks of the Raichikhinsk brown coal field. Their age was corroborated by the palynologic and paleobotanic data. The detailed biostartigraphic data were obtained in the area"Pioneer"for the first time. The coal-bearing strata were correlated with those from the sections of the Arkhara-Boguchan brown coal field and the stratotype of the Tsagajan Formation of the Bureya Belogor’ye.

An Experimental Study on the Production of Fulvic Acid from Brown Coal Using N-Mn-TiO_2 as a Catalyst and H_2O_2 or HNO_3 as an Oxidizer

[Objective] The study aimed to extract fulvic acid from brown coal using N-Mn-TiO2 as a catalyst and H2O2 or HNO3 as an oxidizer. [Method] The effects of catalyst N-Mn-TiO2 on the yield and structure of fuMc acid were studied, and the content of functional groups in fulvic acid was analyzed qualitatively and quantitatively. [ Reselt] Two catalysts could improved the yield of fulvic acid, that is, catalyst 1 （N： Mn： 13 = 16： 0.001：1, roasting temperature was 400 ℃） and catalyst 2 （N： Mn： Ti = 16： 0.001：1, roasting temperature was 100 ℃） increased OFA yield by 10.69% and 32.17% and NFA by 8.61% and 7.49% respectively. After the addition of catalysts, the content of total acid radicals in OFA changed little, and carboxyi content increased slightly, but phenolic hydroxyl content decreased. When HNO3 was used as an oxidizer, the content of total acid radicals and phenolic hydroxyl in NFA decreased. In addition, the structure of OFA was different from that of NFA. [Condusion] The research could provide scientific references for the development and application of brown coal in future.

STRUCTURAL ORIGIN OF THE FAULTED BROWN COAL BASIN IN YUNNAN, CHINA──The role of strike-sliping in basin formation and inversion of Xianfeng coal basin

Based on the analysises of regional structural setting, basin formation and deformation, this paper demonstrates that the Xianfeng basin has been formed and inverted under the strike-slip regime. The article is a partial result of the whole research.

Evaluating the Technical and Economic Feasibility of Adding a Power Recovery System to the Steam Condenser of a Lignite Coal-Fired Power Plant

Steam is the typical working fluid to drive turbo-generators in coal-fired power plants. It is an effective working fluid, but some of its energy is extracted in an unusable form when condensed. A Power Recovery Cycle (PRC) using a more volatile Secondary Working Fluid (SWF) added to the steam cycle could improve energy efficiency. PRCs have been applied to the flue gas and for combined cycle systems but not to traditional plant steam cycles. This paper details an analysis of adding a steam cycle PRC to a 500 MW lignite coal-fired power plant. A validated model of the plant was developed and PRCs using the three most attractive SWFs, benzene, methanol and hydrazine, were then added to the model. Adding a benzene, methanol, or hydrazine steam cycle PRC will produce an additional 59, 34, and 49 MW, respectively. An AACE Class 4 factored broad capital cost estimate and comparable operating costs and revenue estimates were developed to evaluate PRC feasibility. The benzene, methanol, and hydrazine processes had 2019 Net Present Values (NPVs) @12% of -$32, -$59, and +$35 million ± 40%, respectively. Thus, a PRC may be profitable at current or modest increases to U.S. Upper Midwest electricity prices of around $0.0667/kWh.

Experimental Study on the Method of Extracting Humic Acids from Brown Coal Using Hydrogen Peroxide

[ Objective l The study aimed to discuss the optimal conditions of extracting humic acids from brown coal using hydrogen peroxide （H202）. [ Method] Fulvic acid （FA） was prepared through oxidizing the brown coal from Qujing City, Yunnan Province using H202, and humic acids were extracted from the original brown coal and its residues respectively, then the dominate constituents of humic acids were obtained by using pH grading method, finally their chemical composition of humid acids was characterized by Fourier transform infrared spectrometry and func- tional group content analysis. [Result] The mass ratio of the brown coal and oxidant affected the yield of FA most obviously, followed by oxidization temperature and duration, while oxidant concentration had no obvious effect. The optimum conditions were determined as follows： coal-oxidant ratio was 1 ： 0.60, oxidization temperature was 45 ℃, oxidization duration was 210 min, and the concentration of hydrogen peroxide was 20%. Under the conditions, the yield of FA was up to 20.40%. Analysis of component properties indicated that the content of carboxyl and total acidic groups in FA improved obviously under the optimum conditions, and the content of active functional groups in OHA was higher than that of HA, while the domi- nate constituents of OHA needed higher pH during precipitation compared with those of HA. [ Conclusion] The research could provide a new method to prepare good humic acids using brown coal,

Geochemical and Mineralogical Characteristics of Pleistocene Lignites and Associated Sediments of Marathousa Coal Field,Central Peloponnese,Greece

The mineralogy and geochemistry data are presented for thirty-seven shales, four concretions, two carbonate sediments and seven lignites from the Marathousa coal field of the Megalopolis Basin in Greece. The argillaceous rocks consist of chlorite, illite, kaolinite, albite,quartz, opal-A, calcite and dolomite; the concretions of aragonite, gypsum and pyrite; and the carbonate rocks of calcite, quartz and illite. The mineral matter in the lignites consists of gyp-sum, quartz, albite, chlorite, illite, opal-A, dolomite, pyrite, and rarely calcite and kaolinite.A three-factor model explains the total variation of major and trace elements in the argillaceous sediments. The first factor is an aluminosilicate factor and involves the following elements: Al,Si, Mg, Na, K, Ti, Mn, Nb, Y, Rb, Zn, Cu, Ni, Cr, Nd and V, associated with chlorite,albite and illite. The second factor involves the elements Ca, Sr, Ba, Zn and Sc and is related to carbonate lithology and mainly the carbonate concretions with gypsum. The third factor in-volves Fe and Ce with a weak association with Mn. The diagenesis of the Marathousa sedi-ments and lignites was ot very advanced as indicated by (a) the total thickness of the sequence (500 m), (b) the presence of biogenic silica (opal-A) and (c) the age of the deposit (Pleis-tocene). For these reasons the presence of chlorite, illite and kaolinite in the sediments and lig-nite is due not to diagenetic reactions but to weathering of the flysch and metamorphic rocks at the edges of the Megalopolis Basin and transport of the weathering products (illite, chlorite,kaolinite) into the basin of deposition. The diagenetic minerals of the Marathousa sequence in-clude pyrite, gypsum, dolomite and aragonite.

Discussion on Selection of Pulverizer and Moisture of Pulverized Coal for Lignite Boilers

In China,the abrasion index and the free moisture are regarded as the criteria for determining whether the medium-speed pulverizer or the fan pulverizer could be selected.Based on comprehensive studies on foreign methods for choosing the pulverizing system for lignite boilers,it is suggested that the particle size of coal,the drying time,the drying temperature and the humidity should be taken into account when measuring the free moisture of lignite,and the total moisture could also be the principle for type selection of pulverizer for lignite boilers.Furthermore,the determination of pulverized-coal moisture has great influence on the running of pulverizing systems.The actual moisture of certain pulverized coals is compared with that calculated with different methods and a feasible method for determining the moisture of the pulverized coal is suggested.

Future of Renewable Resources in an Area Burdened by Brown Coal Mining

This contribution is focused on a possible utilization of renewable energy resources in the Podkrušnohoří?region (Chmomutov, Most, Teplice, ústí nad Labem districts) in the northern part of the Czech Republic after the end of brown coal mining in 2055. Results of the research describe current share of renewable energy resources (solar, wind, water, biogas) in the model area, and a future energy potential in order to ensure sustainable development of an anthropogenically burdened region. Aim of this contribution is to determine, which renewable energy resources would be the most suitable for energy production after the end of brown coal mining. It also describes current and possible use of geothermal power as there are registered heat flow anomalies in the area.

Change in Grain-Size Composition of Lignite under Cyclic Freezing-Thawing and Wetting-Drying

The paper presents the change in grain-size composition of lignite under cyclic freezing-thawing (FTC) and wetting-drying (WDC). The article shows that in the spring and autumn periods the lignites can be subjected to repeated freezing-thawing and wetting-drying, which determines the possibility of changing their grain-size composition and structure. Experimental studies in laboratory conditions on the influence of cyclic freezing-thawing (FTC) and wetting-drying (WDC) on the quality indicators of lignites have been carried out, their granulometric (fractional) composition has been studied. Freezing-thawing cycle conditions are as follows (FTC): minimum exposure temperature: -20°C;maximum: +5°C;relative humidity: 30%;number of processing cycles: 3. Wetting-drying cycles are as follows (WDC): drying temperatures are +20, +40, +60, +80°C, drying time 90 minutes, the coals are further subjected to rain (soaking) for a period of water saturation to humidity of 30% - 40% and dry again. The number of wetting-drying cycles is 3 times. The tests have revealed the destructive effects of FTC and WDC on the samples of lower metamorphic grade coal, and the cycles of wet-dry lead to the much higher yield of fine sizes (-6+0;-13+0 mm) than the cycles of freeze-thaw. Furthermore, it is found that the increase in the yield of fines depends on the heating temperature: coal disintegration proceeds more intensively at a higher temperature of drying.

基于Hoek-Brown参数确定方法的多煤层开采工作面矿压显现规律模拟研究

结合宁东矿区任家庄矿的生产实例,利用基于Hoek-Brown强度准则确定煤、岩体力学参数的方法,运用FLAC3D软件模拟分析了任家庄矿3号和5号煤层开采中的矿压显现规律,并根据现场工作面巷道围岩应力和表面收敛监测结果,对比分析了数值模拟结果的准确性。研究发现:基于Hoek-Brown经验强度准则所确定的煤、岩体力学参数与标准煤岩样的实验室测定值有明显差异,两者间并非简单折减关系,而与岩体结构特点、完整岩石强度和开挖影响等因素有关。现场多煤层开采中矿压显现规律的实测与数值模拟结果的比对,进一步验证了基于Hoek-Brown准则确定煤、岩体力学参数的有效性和合理性。

基于Hoek-Brown准则的深部煤层钻井坍塌压力弹塑性分析

利用三轴压缩实验确定了沁水盆地平定区块深部煤岩在高围压条件下的弹塑性特征。以Hoek-Brown准则为极限平衡条件,提出了基于工程允许塑性区半径的深部煤层井眼坍塌压力弹塑性计算方法,得到控制深部煤层井壁坍塌的主要参数:煤岩地质强度指标GSI值、非均匀地应力系数及工程允许塑性区半径。以平定区块PD-095井为例,分析了深部煤层坍塌压力弹塑性结果与弹性结果的差别,讨论了坍塌压力弹塑性结果随影响因素的变化规律。结果表明,当工程允许塑性区半径为井眼半径的1.5倍时,PD-095井坍塌压力弹塑性结果较Hoek-Brown准则、Mohr-Cou-lomb准则弹性结果分别降低6.52%,4.66%;随着工程允许塑性区半径的增大、地应力非均匀性的降低,井眼坍塌压力下降;坍塌压力与地质强度指标GSI值呈负乘幂函数关系。

基于Hoek-Brown准则的节理扩展煤层破碎分级方法

考虑地应力作用下煤层节理扩展特性对煤层破碎的影响,给出了煤层节理扩展的判别方法。应用小波神经网络方法和逐级加载算法,联合反演分析节理扩展煤层应力场,获取煤岩单点最大、最小主应力,并结合霍克-布朗准则提出煤层破碎分级定量研究方法。依据煤层破碎系数大小和能量法判据将煤层破碎程度划分为A、B、C、D四个等级,并确定煤岩破碎分级标准。应用本文提出的煤岩破碎分级方法和标准,对沁水盆地晋城区块煤层破碎分布规律进行预测,结果表明:晋城区块南部的阳城、町店、樊庄、潘庄等地区煤层破碎严重(A级),而区块的西北部煤层破碎程度最轻(D级)。理论结果与现场实测的煤层地质资料一致,验证了本方法的预测结果。

基于Hoek-Brown应变软化模型的煤柱稳定性特征数值模拟研究

以研究煤柱稳定性和设计合理煤柱尺寸为目的,基于岩体本构特性的基础,分析不同煤柱尺寸条件下的承载特征和稳定性特征,给出了煤柱承载的阶段性特征、强度特征、峰后强度衰减特征及煤柱尺寸的相关性。