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11.
M. Kavvadas B. Papadopoulos N. Kalteziotis 《Geotechnical and Geological Engineering》1994,12(2):87-112
Summary The paper describes an investigation of the geotechnical properties of the Ptolemais lignite (brown coal) and shows that the
soil mechanics principles used in the study of natural and cemented soils are applicable. The material has a high and variable
void ratio incompatible with its preconsolidation pressure, which may be attributed to the existence of structure (chemical
bonding). Bond strength and degradation have been studied and are found to be isotropic, while the stress-strain response
in the prevield domain is intensely cross-anisotropic. The shear strength determined from triaxial CU and CD tests is variable
but strongly dependent on the in situ moisture content. Tests on high quality intact specimens having a wide range of moisture contents (100–150%) verify a hypothesis
that the magnitude of bond strength (expressed by the peak shear strength) is inversely proportional to the moisture content.
A Hvorslev-type normalization process shows that the peak shear strength of the material can be estimated from the in situ moisture content with reasonable accuracy, thus facilitating preliminary stability calculations of production cuts in lignite
mines. The properties of the Ptolemais lignite are compared with the properties of a lignite from another location in Greece
(Megalopolis) and an Australian lignite (Morwell). It is shown that the shear strength characteristics of the lignite types
studied are similar and strongly dependent on the in situ moisture content, which seems to be a measure of the magnitude of inter-particle bonding. 相似文献
12.
本文介绍了某地含铀砂岩中有机质的分布、物性、光性、化学成分和含量等特征;指出了有机质以褐煤为主、腐殖酸盐为次,有沉积和再沉积两种成因;讨论了有机质在铀成矿过程中的作用——有相当作用,然而系次要作用,起主要作用的系其它因素——层位、岩相、岩性、构造、层间氧化和蚀变(去硅化、方解石化、红化等);故寻找这类矿床时应将其它因素与有机质并重。 相似文献
13.
The late Tertiary high ash brown coal (Rr=0.26%) of the Schirnding Seam Zone is mainly composed of huminite. The seam is underlain by a thick saprock (mica saprockkaolinite-mica saprock) some tens of meters thick which gradually developed from phyllitic basement rocks and a thin Footwall Series of coarse-grained clastic sediments which, however, occur only in a few places. The roof rocks ‘ Hanging Wall Series' abruptly appear on top of the seam and consist of massive gray mudstones and arenites, intercalated with some tuffites. These Tertiary series were studied in open-pit mines operated for coal and clay and in bore holes. Chemical investigation involved the analyses of TOC, TSC, Ni, Co, Pb, Zn, Ga, Be, V, Cr, U, Th, P, Zr, REE and organic compounds of extracted organic matter (=OM). Early Tertiary chemical weathering was responsible for the monotonous kaolinite-mica-goethite mineral assemblage in the saprock and the footwall series. In the coal-bearing basin a more variegated mineral association including, pyrite, kaolinite, illite, smectite, illite-smectite mixed layers and siderite was brought about by volcanic processes, intrastratal solution set free in course of coalification and early diagenesis and by meteoric waters infiltrating the coal-bearing series from uplifted parts of the basin, which underwent strong oxidation. The environment of deposition is interpreted in terms of peatswamps that were fed by small streams and crevasse splays of a meandering drainage system grading towards the basin margin into a braided stream system on an alluvial fan plain. Strongly fluctuating water levels were responsible for the pronounced cyclicity to be encountered across the coal-bearing series. The processes of element redeposition and element migration in the Schirnding Basin are operative across the interface coal-saprolite (detrital influx of heavy minerals and intrastratal solution, hydrocarbon infiltration and redistribution of organic matter, reworking of duricrusts), in the saprolite proper (weathering leachats) and across the redox boundaries between the Schirnding Seam Zone and the Hanging Wall Series (input of physils and diagenetic alteration) as well as its strongly oxidized stratigraphic equivalents at the basin edge (volcanic influx, intrastratal solutions). Chemical and mineralogical variations across the coal basin which are directly controlled by the variation in the environment of deposition, weathering and groundwater movements may be directly correlated to changes in the saprock due to the immediate contact between coal and bedrock. 相似文献
14.
A numerical experiment carried out to investigate the structural model of the Domenico lignite site is discussed. The model is a 2D structure containing several lignite layers at different depths, and a low-velocity layer at the top of the model. The experiment consists in simulating a measured CDP section by two independent techniques, based on completely different concepts: the finite-difference method and the ray method. Due to the incompleteness of the ray synthetic wave field, as well as to numerical problems of the finite differences at higher frequencies, the agreement between the synthetic seismogram sections for the individual shot points is poor. However, the CDP stacked sections modelled by the ray and finite-difference methods agree rather well. This is because the main differences between the wave fields computed by the two methods are due to the presence of the low-velocity layer (ground roll, head waves, etc.), and just these parts of the wave field can be suppressed by routine data processing such as f–k filtration. Synthetic ray and finite-difference CDP stacks agree relatively well with the observed data. They confirm three lignite seams and a fault in the shallower one. The synthetic data also indicate that many apparent horizons of the measured section may be due to the multiple reflections within the subsurface low-velocity layer. 相似文献
15.
Konstantinos Chassapis Maria Roulia Dimitra Tsirigoti 《International Journal of Coal Geology》2009,78(4):288-295
Lignite samples from two deposits located in the Megalopolis Basin, Southern Greece, were evaluated for their potential applicability as raw materials for the production of organomineral fertilizers. Fundamental chemical analyses were carried out to demonstrate high humic substances and metal contents. To determine their relative distribution in the Megalopolis lignite extract, eight elements, namely Na, K, Cd, Mn, Mg, Pb, Zn, and Cu, were studied both in H2O and in Na4P2O7/NaOH solutions. The behavior of these metals showed significant variations; Zn, Pb, Cd, and Cu associate mostly to the humic substances and proved scarce in the water extract. Contrarily, K and Mg gave a significantly low total yield in the Na4P2O7/NaOH solution, while Mn was classified among the least extracted elements. Further enrichment of Megalopolis humic substances in these metals was achieved; Pb and Mg proved the most and least retained metal, respectively. Decomplexation titration curves of humic matter saturated with these metal ions demonstrated that novel organomineral fertilizing materials may develop based on optimized metal ion and humate contents, which can retain metals in a soluble form within a wide pH range. Formation of complexes between humic substances and Zn, Cd, and Mg was clearly indicated. 相似文献
16.
Andriana Giannouli Stavros Kalaitzidis George Siavalas Adamantia Chatziapostolou Kimon Christanis Stefanos Papazisimou Cassiani Papanicolaou Antonis Foscolos 《International Journal of Coal Geology》2009,77(3-4):383-393
This study evaluates Greek peat and coal samples for applications in the agricultural/horticultural sector and assesses the suitability of a certain peat/coal either as soil conditioner or as raw material for manufacturing organic fertilizers.Twenty-six samples of different rank ranging from peat to subbituminous coal obtained from several Greek peat/coal deposits, were studied. The laboratory tests included: a) pH and electrical conductivity (EC) determinations, as well as proximate, ultimate and maceral analyses, in order to characterize the samples, b) major and trace element analyses of both the total and the easily exchangeable fractions (EEF), in order to assess the phytotoxicity effect, c) cation exchange capacity (CEC) determination in mixtures of the samples (5 wt.%) with a certain soil (95 wt.%), in order to evaluate the peat/coal impact, and d) the determination of the contents of humic substances (HS), as well as of carboxylic and phenolic groups.The majority of the samples reveal moderate to high ash yields (16–80 wt.%), a slightly acidic to neutral character and electrical conductivity ranging from 100–2500 μS/cm. Concerning the environmental impact of the sensitive trace elements, which might be leached, As, Mn, Ni and Sr show relatively strong mobilization in some samples, although severe impacts are not expected. The soil's CEC is generally improved, although it remains at moderate levels. The most interesting aspect is the humic acids content, which ranges between 9.6 and 52.2 wt.% on a dry basis, exceeding 25 wt.% for most of the samples. The obtained results enable an initial correlation among the different parameters and a rating of the samples according to their suitability for soil-amelioration agents. 相似文献
17.
Internationally there is considerable interest in utilizing hydrogen as an energy carrier. The use of hydrogen offers considerable potential benefits such as reducing greenhouse emissions, reducing urban pollution, increased energy security and increased efficiencies from the use of advanced energy conversion technologies.One of the most important questions when considering the development of a hydrogen economy is “where will the hydrogen come from?” Possible answers include electrolysis of water, steam reforming of methane and the gasification of coal. Given the high costs associated with electrolysis of water, and the increase in the cost of methane predicted over time, the gasification of coal is viewed by many as being the cheapest method of hydrogen production in the foreseeable future. These considerations are particularly relevant to New Zealand where gas supplies are dwindling but where there is sufficient coal to last for many centuries at present utilization rates. This, along with the current high international interest in hydrogen energy, has been recognized by the New Zealand Government in the form of a six-year [2002–2008] research project “Hydrogen Energy for the Future of New Zealand”.One important coal property that, in particular, determines the suitability of a particular coal for use in a fluidised bed gasifier is its reactivity towards the gasification reaction. It was found that a high percentage of New Zealand's coal resource is particularly well-suited towards fluidised bed gasification, reacting at anywhere between 0.9 to 1.75 times the rate of Australian brown coals. It was found the New Zealand lignites contained significant levels of organically bound calcium, which was shown to be responsible for not only the high reactivity of the New Zealand lignites, but also a product gas composition with higher than expected hydrogen concentrations. These findings are discussed along with their implications for the gasifier and gas clean-up design. 相似文献
18.
The Cr and Ni contents are high in the Eocene lignite of the Shenbei coalfield, which is a small intracontinental basin located in Liaoning Province, China. In this paper, we studied the distribution, origin and occurrence of Cr, Ni and other hazardous trace elements in the Shenbei lignite on the basis of coal petrology, and geochemistry of the lignite and combustion products. The following conclusions on the Shenbei lignite can be drawn: (1) The dominant maceral group in the Shenbei coal is huminite (humodetrinite), accounting for 96%–99% of the total maceral. Inertinite content is less than 1%. Liptinite content (sporinite and cutinite) is 0.2–1.6%. Common minerals in the Shenbei lignite include clay minerals (kaolinite), pyrite and quartz, and calcite and siderite. Chromite is not present in the lignite. (2) Potentially hazardous trace elements such as Co (22 μg/g), Cr (79 μg/g), Cu (63 μg/g), Zn (93 μg/g), V (88 μg/g) and Ni (75 μg/g) are strongly enriched in the Shenbei lignite compared with average concentration of trace elements in the Chinese coal and worldwide lignite. These elements are mainly associated with fulvic acid (FA) and/or coal organic macromolecular compounds in most of the studied lignite samples, indicating an organic association and enrichment of these elements in the Shenbei lignite. (3) Unusually high trace elements contents in the Shenbei lignite are derived mainly from the olivine basalt (country rock of coal basin) that consists of 52.7% plagioclase, 17.8% pyroxene, 14% olivine and 15.5% Ti–Fe oxide minerals. These olivine basalts have higher Cr, Ni, Pb and Zn contents than other types of rock and worldwide basalts do. (4) Fly ash of the Shenbei lignite, with 90% 1–50 μm amorphous particles and 8% 1–10 μm cenosphere, has high contents of Zn (23,707 μg/g), Be (12 μg/g), Sr (1574 μg/g), Pb (486 μg/g) and Cr (349 μg/g). In particular, the ferruginous micro-cenoshperes contain 1–12.79% Zn. Fine bottom ash (<0.031mm) of the Shenbei lignite has higher contents for most of the elements with the exception of Mo, Sn and Zn. Therefore, the potentially environmental and health impact of the fly ash and fine bottom ash should constitute a major concern. 相似文献
19.
S. Kalaitzidis A. Bouzinos S. Papazisimou K. Christanis 《International Journal of Coal Geology》2004,57(3-4):243-263
The intermontane basin of Ptolemais is part of a major tectonic trench, located in NW Greece and includes around 65% of Greek coal reserves. The Upper Xylite Layer (UXL) is a distinct lignite layer, being 3–6 m thick and outcropping in the upper part of the Pliocene Lignite-bearing Sequence at the Notio Field and Tomeas Eksi Mines of Ptolemais. Compared with the xylite-rich lithotypes, the matrix lithotypes within UXL contain more ash. Micropetrographic studies suggest that the Upper Xylite Layer is rich in huminite (>90%). Textinite dominates in the xylite-rich lithotypes, while attrinite dominates in the matrix lithotypes. The liptinite content is <10%, while inertinite rarely occurs. Palaeobotanical determination revealed that the xylite-rich coal originated from Coniferous vegetation, specifically from Glyptostrobus europaeus. The occurrence of G. europaeus as a coal-forming element is significant because, though this kind of vegetation was common in many Greek coals of Miocene age, this is the first time it has been recorded from the Pliocene. This study suggests that the Upper Xylite Layer is autochthonous. According to coal-facies diagrammes, peat accumulated under pure telmatic conditions in a relatively wet forest fen. Both herbaceous and arboreal vegetation contributed to peat formation. 相似文献
20.
The Rio Maior Basin (Portugal) is a tectonic depression, filled by a Pliocene sequence that comprises, from floor to roof: (i) kaoliniferous fine sands, (ii) diatomites and lignites, (iii) recent deposits of sandstone and clay. The diatomites and lignites form a small dissimetric syncline with alternating seams. Ten lignite seams were identified and named from floor to roof as F, E, D, C.2, C.1, C, B, A, a and a′. Seams A, D, E and F are considered to be the main seams.The organic fraction consists mainly of macerals of the huminite group, with small percentages of inertinite and liptinite groups. However, the petrographic composition of each seam is distinct, particularly with regards to macerals of the huminite and liptinite groups.Calculation of petrographic indices permitted to plot the coals in facies and palaeoenvironment diagrams. Five facies have been defined: (i) aquatic, (ii) herbaceous swamp, (iii) mixed swamp with forest and herbaceous vegetation, (vi) forest swamp (wetter) and (v) forest swamp (drier).These lignites are humic coals formed from organic matter of terrestrial origin. The peat biomass at the origin of these coals formed from a very diverse vegetation comprising gymnosperms and angiosperms. In seams F, and occasionally in seams E and D, Botryococcus algae have also contributed to the biomass. Peat deposition corresponded to a rheotrophic hydrological regime: the water level always remained above the topographic surface of the basin. Nevertheless, during the deposition of seam A in the northern part of the basin, the water level was slightly below the topographic surface. The organic matter was preserved in anaeorobic conditions. 相似文献