Untypical rheological behaviour of the lignite–carboxymethylcellulose–water dispersion system

Suspensions of lignite in a solution of a high molecular weight carboxymethylcellulose show peculiar rheological behaviour. Unless the lignite concentration is sufficiently high, apparent viscosity and viscoelastic moduli of the suspension are lower than those of the pure solution. This effect is not suppressed by changing pH and seems to be common for low-concentrated suspensions in solutions of high molecular weight (bio)polymer. It is explained by specific structuring of the suspensions. Lignite particles at lower concentration separate long cellulose chains and facilitate their movement under shear flow. The particles loosen inter-chain contacts, disturb and release elastic gel-like structure formed by the long cellulose chains, which results in the low strain oscillatory deformation, the decrease in the moduli and the increase in the loss angle. If the amount of lignite particles is sufficiently high, suspension stiffening occurs as usual. No such effect was observed for suspensions prepared from the low molecular weight derivative. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Microbial liquefaction of lignite pretreated with dilute acid at elevated temperature and pressure

Two microbial cultures—ML-13 (aCandida sp.) and LSC (a fungal isolate from the University of Arkansas)—have been employed in the direct liquefaction of Louisiana lignite. Lignite samples were pretreated with nitric acid and microbial culture broths at elevated temperatures and pressures. Subsequent treatment with active cultures and culture derivatives resulted in significant solubilization of the lignite. Up to 50% liquefaction of pretreated coal (20% HNO₃ at ambient temperature and pressure) was observed in 4 d with ML-13 cultures, whereas almost 80% liquefaction occurred in a similar time period when exposing pretreated lignite to an autoclaved, cell-free culture broth.     

Analysis of turkish lignite tar by coupled LC/GC,GC/MS,and capillary SFC

This work describes the analysis of a pyrolysis product of a lignite sample obtained from the Turkish Goynuk reserve. The aliphatic, aromatic and polar compounds present in the tar are separated and identified by various chromatographic techniques: Capillary gas chromatography/mass spectrometry (GC/MS), on-line high performance microbore liquid chromatography/capillary gas chromatography (LC/GC) and capillary supercritical fluid chromatography (SFC). The suitability of each technique for this particular application is discussed, and semi-quantitative results are presented for the major components detected.     

峨山褐煤的分子结构和分子模拟

作为重要的化石能源，褐煤资源潜力巨大、分布广泛但综合利用率低。研究褐煤的分子结构模型，有助于预测褐煤在热解、液化和气化过程中的化学反应机理及反应路径，进而提高褐煤的综合应用水平。以云南峨山褐煤为研究对象，利用傅里叶变换红外光谱、13C核磁共振波谱及X射线光电子能谱等分析测试方法，获取了峨山褐煤的含碳、含氧及含氮结构参数。在此基础上，借助Gaussian 09计算平台，采用量子化学建模的方法构建并优化了峨山褐煤的分子结构模型。研究结果表明：峨山褐煤的芳碳率为39.20%，芳香碳结构主要为苯和萘，且芳香桥头碳与周边碳的比值χ_b为0.07；脂碳率为49.51%，脂肪碳结构主要为亚甲基，季碳和氧接脂碳；氧原子主要存在于羟基、醚氧、羰基和羧基结构中；含氮结构则以吡啶为主。基于元素分析、13C 核磁共振波谱分析，又经过热重实验消除褐煤中残余水分的影响后，计算出峨山褐煤的分子式为C₁₅₃H₁₃₇O₃₅N₂。依据分子式及分析结果计算出峨山褐煤的结构单元含量并构建出其初始结构模型，采用半经验法PM 3基组及密度泛函理论M06-2X/3-21G基组对初始分子构型进行优化。优化后的分子模型具有明显的三维立体特征，芳香环之间较为分散且在空间中排列不规则，芳香簇主要通过亚甲基、醚氧基、羰基、酯基和脂肪环连接，含氧官能团主要分布在分子边缘，脂肪族侧链较多。对优化后的分子模型进行振动频率计算进而获得了分子模型的模拟红外光谱，其与实验红外谱图吻合度良好，证明了峨山褐煤分子结构模型的准确性、合理性。分子结构模型的构建有利于直观地了解峨山褐煤的分子结构特征，从而有助于从微观分子角度研究峨山褐煤的宏观性质。同时，峨山褐煤分子结构模型可为其在热解、液化和气化等领域研究中提供理论指导。     

利用激光诱导击穿光谱原位在线检测褐煤及煤烟

褐煤是我国现阶段的主要用煤,但因为其较低的煤化程度,使用时会产生污染环境的二氧化碳和黑灰,而且烟尘中含有的金属离子会危害人体健康,所以开展对褐煤烟尘的研究非常有意义。而激光诱导击穿光谱技术(LIBS)具有快速、多元素同时分析的特点,适合用于煤烟的原位在线探测。实验制备了含铅浓度不同的三种褐煤样本(O, H, L),其中O为原始无铅样本,利用LIBS对褐煤及煤烟进行原位在线探测。实验仪器主要由激光器,反射镜,聚焦透镜,触发装置,载物平台和分析系统组成。用高纯度铅块校准实验中的的波长漂移。分析了褐煤样本O, H, L的元素成分。发现褐煤O中含有C, Si, Fe, Mg, Al, Ca, Sr, Na等元素,同时检测到空气中的元素N,O,H_α和H_β等,且含铅褐煤光谱中多出了8条铅元素的谱线,最后给出了褐煤中主要元素的光谱鉴别表。然后使用447 nm的连续光点燃褐煤,将1 064 nm的脉冲光聚焦在煤烟上,对褐煤煤烟进行了原位在线检测。发现煤烟中含有Mg, Ca, Al, Sr, Pb等金属离子,说明了褐煤中的一些金属离子会随着煤烟排放到空气中并危害人体健康。经褐煤及煤烟的光谱比较,发现煤烟的信噪比更差,且所有元素的谱线强度都比在褐煤中弱很多,另外发现在烟尘中碳原子谱线的相对强度是所有元素中最高的（无明火）,这说明LIBS可以有效探测CO₂。分析了实验中的CN分子谱,给出了CN分子的具体波长,并利用LIFBASE软件拟合了CN分子的转动温度和振动温度,分别为6 780和7 520 K。最后对样本H和L两种煤烟中的铅浓度进行分析,选取参考线(Ca Ⅱ 363.846 nm)归一化之后比较了铅元素在363.956, 368.346和405.780 nm处的相对强度,发现这三条特征谱线的相对强度与自身实际所含的铅浓度呈很好的线性关系,验证了LIBS技术应用于煤烟中重金属元素半定量分析的可行性。     

Permeability anisotropy due to consolidation of compressible porous media

The characterisation of flow through porous media is important for all solid–liquid separation and fluid transport realms. The permeability of porous media can be anisotropic and furthermore, the extent of anisotropy can be increased as a result of an applied compressive force. However, the understanding of how anisotropy develops is incomplete. An overview of research on permeability anisotropy is given and an expression for predicting anisotropy as a function of void ratio is offered. The two underlying assumptions of the proposed model are: flow in different directions occurs within the same network of pores and deformation is primarily due to the compression of the particles in the direction of the applied force rather than due to particle rearrangement. The assumption of network connectivity allows permeability anisotropy to be described as a function of flow path tortuosity only. Results are presented for hydraulic anisotropy measured in lignite that has been upgraded by a compression dewatering method known as mechanical thermal expression. The lignite permeability is shown to be up to eight times greater in the direction perpendicular to compression, suggesting that the rate of dewatering could be significantly increased by choosing the drainage to also be perpendicular to the direction of the applied compressive force. It is illustrated that the proposed anisotropy model can be used to accurately predict the experimentally determined permeability anisotropy ratios for lignite, as well as for other materials including sand, clay and kaolin.     

Rheological aspects of dense lignite-water suspensions; time dependence, preshear and solids loading effects

An investigation of the rheological properties of dense lignite-water suspensions is reported here in order to evaluate the parameters that affect the rheology of these suspensions. Different types of particle size distributions were achieved via wet grinding with particle sizes down to 1 μm. Polyelectrolytes and surfactants were used to improve the stability and rheology of suspensions. The achieved solid volume fraction, φ, with acceptable rheological behavior was 0.45, while the ratio of φ/φ _m was close to 0.85; φ _m is the maximum solid volume fraction. Various types of flow tests were performed on lignite-water suspensions with various preshear times and stress levels. Typical shear rates varied in the range between 10^–2 to 10² s^–1. The low shear behavior was found to be quite different from the high shear behavior for the most concentrated suspensions, with a plateau value at low shear rates indicating the appearance of a yield stress. These plateau values, however, depend on shear history, which is responsible for the development of different structures in the sample. The viscosity curves corresponding to the ascending and descending parts of the flow curve were found to be different; these flow curve parts can be described either by well established models or by modified ones. The non-Newtonian time dependent behavior of the lignite-water suspensions is attributed to the high value of the ratio φ/φ _m , the polydispersity of the particle size distribution, and the non-spherical shape of the lignite particles.     

超声-硝酸联合法提取褐煤腐植酸工艺

实验考察了超声、硝酸预处理、酸化程度、碱液浓度、反应温度、液固比、反应时间等对腐植酸提取率的影响,并通过正交设计选择最佳预氧化条件和褐煤腐植酸的最佳提取条件.结果表明;超声硝酸联合氧化法提取腐植酸的最佳条件为：超声频率80kHz,氧化温度50℃,硝酸液固比（mL/g）为5∶1,氧化时间90min,硝酸浓度1.5mol/L.     

Gas Forming Processes within Lignite Mining Dumps

Abstract

Gas analyses of the soil atmosphere of lignite mining dumps yielded increased contents of carbon dioxide. To get information about the potential sources and the carbon dioxide releasing capacity of the dumps, samples of dump material were investigated for their contents and isotopic compositions of organic and inorganic carbon as well as the carbon dioxide in the soil atmosphere. The contents of organic and inorganic carbon were found to vary depending on type of dump material. The isotopic composition of the organic carbon ranges between ?24.5 and ?26.5‰, which is typical for humous materials. The carbonates are found to be of marine origin (δ¹³C: +0.5 to ?1.1‰). By means of the isotope investigations it could be shown that the carbon dioxide in the lignite mining dump arises from these two different sources. Mixing ratios can be calculated using the isotope balance equation. Both reaction paths are associated with oxygen consumption and do not result in an increased gas pressure within the dump.     

Reactive matrix clean-up of naturally occurring perylene in young lignite

Young lignite from two locations in Sendai City, Japan, were analyzed for polynuclear aromatic compounds (PACs). Lignite samples were extracted with toluene and PACs were isolated by a compound-class-selective, reactive matrix clean-up. This clean-up separates all compounds of polynuclear aromatic structure, for example hydrocarbons and ketones and their primary metabolites, from interfering organic compounds. The result of this isolation procedure is, therefore, a group of a large number of polycyclic compounds with different functional groups. Further analysis is done by glass capillary gas chromatography. Perylene was identified as the only compound obtained by the reactive matrix clean-up of lignite samples from both locations. Concentrations were in the range of 1–10 mg kg⁻¹. Conversely, PACs resulting from particulate emissions from fossil fuel combustion always contain isomeric PAHs (polynuclear aromatic hydrocarbons) with some polycyclic aromatic ketones and thousands of primary and secondary metabolites at very low concentrations. This was demonstrated for a sample of urban air particulate matter, which is the source of PAC contamination of surface soil. The absence of accompanying PAHs and polynuclear aromatic ketones in the lignite samples confirms that perylene did not originate from a combustion process. It is assumed that the high concentrations of perylene are the result of a reduction of perylene quinone. Thus, the high perylene content of the lignite samples investigated is of biogenic origin.