resumo: Apresenta-se o estudo da sedimentação carbonífera nas diferentes bacias gonduânicas de Moçambique. Neste estudo, o autor posiciona a «Série Produtiva» dentro do Grupo Gonduana e do Sistema do Karoo e faz a descrição dos complexos carbonosos das diversas bacias e do ambiente de sedimentação respectivo.Finalmente, refere-se à tectónica pondo em destaque a implantação das bacias primitivas e o posterior comportamento dos complexos carbonosos face à tectónica de fractura e do dobramento.
resumo: Os depósitos brasileiros de carvão fóssil têm idade variável: Carbonífero Superior – Permiano Inferior, Mississipiano, Pensilvaniano, Cambro-Ordoviciano, Mioceno-Plioceno, Devoniano. As áreas favoráveis à existência de carvão têm uma superfície de 839,690 Km2, equivalente a 9,8% da superfície do Brasil e a 19,5% da área total de bacias sedimentares. Desse total já foram prospectados 77.250 Km2.Os carvões brasileiros têm suas reservas conhecidas (exclusive turfa) no Brasil Meridional, estados de Paraná, Santa Catarina e Rio Grande do Sul. Nesse estado estão localizadas 90% dessas reservas que totalizam 23 x 109 t. O conhecimento limitado que se tem dos depósitos carboníferos no restante do País, especialmente na Amazónia, não permite uma avaliação confiável de reservas; porém, presume-se sejam da ordem de dezenas de biliões de toneladas e que representam mais de 90% das reservas energéticas não renováveis do Brasil.
Esta monografia fornece detalhes quanto à geologia, reservas e actuais usos industriais dos carvões brasileiros: combustão, termoelectricidade, gaseificação, coqueificação. Explana as razões pelas quais estes foram pouco usados: excesso de matéria mineral, dificuldades para sua caracterização e classificação por métodos tradicionais, dificuldades para seu beneficiamento, o fato de serem mediocramente coqueificáveis e, sobretudo, até 1974, a facilidade para o qual substituíamos pelo petróleo ou pelo gás, ou, ainda, por carvões estrangeiros.
resumo: The Barakar Formation is a thick coal-bearing succession wich occurs in a number of individual basins such as the Raniganj, Jharia, Bokaro, Karanpura basins, etc. A systematic investigation of the palaeotransport pattern, primary structures, and isopach maps coupled with the physico-chemical characteristics of the coal seams has revealed the nature of the environment and the origin of the coals. A broad meandering river and its tributaries could be delineated. The coal seams formed within the floodplains of these rivers, and the plant material mainly corresponds to transported remains. The westerly palaeotransport pattern of the basins suggest a selective sorting and dumping of woody tissues and spore exines in the eastern part. The rank of coals also increased eastwards in the tectonically active zone where concomitant subsidence of the basins took place.The abundant presence of inertinite in the western area may have been due to exposure to atmospheric oxygen of the plant material. Petrographic variations in the coal and sandstones can be related directly to the depth of burial which in turn influences the rank and caking properties of the coals.
resumo: Se analizan las sequencias florísticas carbónicas y pérmicas del Gondwana y áreas marginales. Estos datos se distribuyen en mapas paleogeográficos que corresponden a cuatro segmentos cronológicos: eocarbónico-eomesocarbónico, eomesocarbónico-mesoneocarbónico, eopérmico y neopérmico. Sobre la base de los datos más recientes se propone la correlación de zonas y floras para el Neolaleozoico gondwánico.Esta aproximación biostratigráfica incluye la distribuición de sedimentitas posiblemente periglaciales (diamictitas) en las diferentes secuencias analizadas. Se concluye que la paleogeografía fue un factor condicionante del desarrollo de las floras gondwánicas.
La posición paleolatitudinal cambiante de los distintos integrantes del Gondwana sugiere una evolución independiente de cada área. Sud Africa y Sud América tuvieron un desarrollo similar durante el Pérmico y conformaron la Provincia Paleoflorística Nothoafroamericana.
En cambio, durante el mismo lapso, Australia, India y Antártida parecen haber conformado la Provincia Paleoflorística Indoaustraliana, cercana al Polo Sur, com un régimen climático más templado.
resumo: The beginning of coal formation in the Lower Gondwana in India coincided, more or less, with the waning of the Late Palaeozoic Ice Age. Geological and palaeobotanical evidence suggest that temperature conditions existing at the time in Peninsular India were responsible for the development of a special flora dominated by Gangamopteris, Glossopteris and aliied groups. Transformations in the vegetal material during diagenesis and catagenesis, as inferred from biopetrological and rank investigations, reveal that the coal seams of the Karharbari Formation (basal portion of Lower Gondwana coals) experienced high oxidation resulting in excessive fusinization, probably due to rapid sedimentation, shallow basin condition and extensive microbiological action.Thus, the coal seams of Karharbary Formation consist chiefly of the fusic-vitrofusic genetic coal type. From Barakar (Lower, Middle) onwards to Raniganj (coal seams of the upper part of the Lower Gondwana Sequence), a progressive amelioration of the climate, from temperature to humid tropical, facilitated the diversification and proliferation of the glossopterid flora. This change in climatic conditions was accompanied by changes in topographical features and sedimentation pattern. These factors were together responsible for the gradual change in the course of diagenetic and catagenetic processes. The inicial highly oxidative milieu during Karharbari sedimentation became, progressively, less oxidative to partially reducing in the Barakar. Ultimately, high reducing conditions developed fo the Raniganj.
The latter conditions are characterized by extensive vitrinization of the vegetal source material forming the Raniganj coals. The coal seams of the Barakar Formation are rich in trimaceric genetic coal type, whereas those of Raniganj Formation are chiefly of vitric-fusovitric type. It has also been surmized that the geothermal gradient during Lower Gondwana sedimentation was low throughout and that the coal seams attained only low rank. However, in the Damodar and Satpura Gondwana basins, where igneous intrusions ocurred during the later phase of Lower Gondwana sedimentation, the rank of coal seams increased abnormally.
resumo: Discute-se a importância da presença de matéria mineral nos carvões sob a forma de cinzas vegetais, inclusões minerais e estéreis intercalares.Determina-se, pela primeira vez, a natureza mineralógica dos estéreis intercalares presentes em carvões das Bacias Carboníferas de Moatize-Minjova e de Chicoa-Mecúcoè (região de Mucanha-Vúzi) no Vale do Zambeze, República Popular de Moçambique, a saber: caulinite, ilite com interestratificados mais ou menos complexos, nomeadamente de montmorilonite; quartzo; carbonatos e óxidos de ferro.
resumo: Coals are often poorly washable in Southern Hemisphere. Mineral matter (MM) plays an important role in the chemical analysis of such coals, wich is generally done at high temperature (815°C) under oxidizing conditions (except for volatile matter-VM). As the original quantity of MM in coal is greater than the ash content after calcination at 815°C, a correction factor has been established for several coalfields (Brazil, Mexico, etc.), directly from MM measured under oxygen plasma at 150°C. This factor is sometimes greater than 1.10, and a significant ponderal correction has then to be introduced.The influence of MM decomposition amount of H2O (14% from clays), CO2 (44% from carbonates), and SO2 (33% from sulphides) will be added to the actual VM from coaly substance. In consequence, VM is significantly overestimated when minerals are completely transformed. The decomposition of minerals has also an effect on the termal balance.
resumo: In this paper, coal seams from the ‘Productive Series’ of Chicoa-Mecúcoè Coalfield (People’s Republic of Mozambique) are investigated using petrological and palynological techniques.The major aims are to establish the petrographic nature/quality of the coals (washed to 1.5 R.D.) and to classify them in terms of the International Classification of Hard Coals by Type and of Alpern’s Universal Classification of Solid Fossil Fuels. Secondly, the relative age of, and the correlation between, the coal seams is attempted. Finally, broad relationships between the palynological and petrologic data in terms of coal-forming plant communities and palaeonvironments are discussed.
The results indicate that the washed products are vitric in type, mesobituminous in rank, and vary in facies (dependent on ash content). Secondly, the age of the seams range from Lower and Middle Ecca to Lower Beaufort. Finally, the relationships between the petrologic and palynological data suggest that variations in palaeoenvironments are evident. These are discussed in some detail.
resumo: The Lower Gondwana coals (Permian) of India are generally classified as vitric, mixed and fusic types on the basis of quantitative maceral composition. Systematic differences in vitrinite and inertinite contents, and the relative abundance of their macerals have been used by many researchers to describe variations in the coal depositional environment.The authors, while analysing maceral data from the coals of Damodar, Son-Mahanadi, Pench-Kanhan-Tawa (Satpura Gondwana) and Wardha-Godavari valleys, realized that the vitrinite and inertinite ratio may possibly be used for stratigraphic correlation on a regional scale and also for a general assessment of the coals.
resumo: Following the development of improved maceration techniques for the extraction of miospores from southern African coals and thus improved biostratigraphic techniques, a series of Lower Permian coal seams from a proposed type sequence in the Witbank Coalfield, Karoo Basin, South Africa was studied.The results indicated that (i) all the coal seams contained a wide a variety of miospores, and (ii) the relative abundance, diversity and composition of certain biostratigraphically-significant taxa changes progressively throughout the sequence.
These data follow the microfloral pattern recently described in a regional palynobiostratigraphic system for central southern Africa and permit the correlation of these seams with reference strata from elsewhere in the sub-continent. The results also indicate that the coal-forming period in the Witbank Coalfields extended from the lower Ecca (Lower Permian) to the upper Ecca (Mid to Upper Permian) and possibly into the lower Beaufort Groups (Upper Permian). In therms of the microfloral sub-zones proposed by FALCON (1980), this period extends from the Virkkipollenites-Potonieisporites Sub-Assemblage to the Protohaploxypinus-Vittatina-Striatopodocarpites Sub-Assemblage, or Sub-zones C to G.
resumo: The petrochemical caracteristics of the six major coal seams of the Badam area indicate that rank and the cake index both increase with depth, and, in some of the lower horizons, along strike faults. However, in the Tandwa area, the change in rank is minimal with depth, whereas the caking properties still developed despite the coals being on the same horizon. Coals of the Badam area are high in vitrinite and exinite macerals and low in inertinite. The reactive vitrinites (generally R0=0.9 to 1.5), wich are lacking in the coals of the Tandwa area, are essentially the coke forming material. The high exinite contents acts as a binding agent and enhances the fluidity of the associated vitrinite.The palaeotransport pattern suggests that the current moved from E to W and ENE to WSW in the Badam area, dumping the coaly plant matter under anaerobic conditions and, with concomitant subsidence of the basin, producing vitrinites in abundance.
resumo: Because of the scarcity of coking coal in Japan, it is usual to blend 12 to 20 kinds of coal differing in coalification degree, and in the range of softening and resolidification, for the making of good metallurgical coke. It has long been known that the most important coke characters such as strenght, permeability, and reactivity with CO2 deteriorate gradually in the blast furnace after shut down are investigated.Among many physical and chemical causes, which might bring about the deterioration of coke natures, several divise causes could be pointed out. The most important are: solution loss reaction and high temperature attack of hot blast.
To reduce the deterioration of coke strenght the higher rank and higher fluidity of coal blends, the better. Such a result can also be explained by microscoscopic examination of the texture and structure of coke. For a stable operation of blast furnace the coke index should be higher than 92.0.
There is a very good relationship between the coke index and the maximum fluidity of blended coal, and it is experimentally and economically decided that the mean reflectance and the maximum fluidity of blended coal should be 1.5% or more, and 200-1000 ddpm respectively. Thus, the blending target could be defined by these two parameters. As far as these two parameters are concerned, there is not any conspicuous difference on the usage of Gondwana and Euro-American coals in cokemaking.
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