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Tomo 70, Fasc. 2 (1984)

Tomo 70, Fasc. 2 (1984)


Tomo 70, Fasc. 2 (1984)Categoria: Publicações, Comunicações Geológicas, 1980 a 1989

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Descrição

Artigos

1. Ambiente Geológico dos Carvões Gonduânicos de Moçambique – Uma Síntese
Rui S. Afonso (10 páginas)

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.

2. Carvões Brasileiros – Estado da Arte
Joanna Nahuys ; Slawomir Piatnicki (30 páginas)

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.

3. Combustion Characteristics of Inert Macerals of Gondwana Coals
B. N. Nandi (2 páginas)
resumo: The demand for coal as the principal fuel for power generation is growing rapidly throughout the world. The use of nuclear technology for power stations has been seriously challenged by several European countries because of radiation problems and high cost of production. Therefore, demand of large quantity of cheap thermal coal especially from the Southern Hemisphere (Gondwanaland) are being imported and are in high demand. Hence, there is a need to develop methods of assessing quality of coal prior to import and as an aid to negotiating price. Recently, the combustion aptitude of various ranks of Gondwana coals from South Africa, India and Australia was carried out by microscopic and chemical analyses, and in a bench scale drop tube furnace developed by the author and his group. It was found that high percentages of inertinite such as semifusinite and fusinite are present in Gondwana coals. These semifusinites are quite different from those present in the Carboniferous coals of the Northern Hemisphere. Semifusinites of Gondwana coals are highly reactive and a considerable amount of coke was formed in the combustible residue. High mineral matter content is predominant in Gondwana coals but these minerals are non-agglomerating during combustion. The fusion temperature of the ash is rather high because of the presence of high silica and alumina contents and low contents of Iron and calcium oxides. Alkali metals such as Sodium and Potassium play an insignificant role and to not produce any glassy materials on the boiler tube. Washery rejects, which contain mostly inertinite, oxidized vitrinite, exinite, and high percentage mineral matter have better combustion efficiences than those of washed coal. Determination of incombustible Carbon in the residue of fly ash and combustion efficiency of a particular coal was carried out in a newly developed CANMET drop tube furnace.
4. Environment and Origin of Gondwana Coals as Revealed by a Study of the Barakar Formation, in Some of the Major Coalfields of India
B. C. Mukherjee (8 páginas)

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.

5. Floras Neopaleozoicas del Gondwana y su Zonación Estratigráfica. Aspectos Paleogeográficos Conexos
Sérgio Archangelsky (16 páginas)

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.

6. Lower Gondwana Coals of India – Palaeobotany, Petrology and Genesis
G. K. B. Navale (12 páginas)

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.

7. Matéria Mineral em Carvões de Moçambique. Nota Preliminar
Luís Aires de Barros ; M. J. Lemos de Sousa ; Sílvia Furtado (6 páginas)

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.

8. Mineral Matter in Ashy and Non-washable Coals – Its Infiuence on Chemical Properties
Boris Alpern ; Joanna Nahuys ; Luiz Martínez (20 páginas)

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.

9. On the Origin of Gondwanic South Brazilian Coal Measures
M. Marques Toigo ; Z. C. Corrêa da Silva (10 páginas)
resumo: Palynological and petrological studies of several Gondwanic south Brazilian coalfields have resulted in a better understanding of different aspects relating both moor facies and ancient peat-forming vegetation. From the palaeobotanical affinities of certain miospores a shrub-like plant community comprising herbaceous and arbustive LYCOPHYTA and subordinate GYMNOSPERMAE is supposed to be the main contributors to the formation of coal seams. A dominance of Lundbladispora probably indicates an herbaceous type flora ralated to Selaginellales in opposition to the tall tree forest type of vegetation (Lepidodendron) which caracterizes the Carboniferous Northern Hemisphere coal measures rich in Densosporites and Lycospora. This idea is also supported by the fact some coal seams rest on underclays which may present delicate roots quite different from the strong Stigmaria. On the other hand, according to the petrographic composition, different environmente of coal deposition are considered in relation to both the water level variation and the type of vegetation. The forest-terrestrial moor is poorly developed and the deposition is restricted to coaly shale with fusinite, sporinite-poor durite and resinite. The forest (reed) moor which is supposed to be the most developed in the Carboniferous coal measures, is also subordinate and occurs in some coalfield characterized by the presence of fusinite and/or semifusinite, telinite and sporinite-rich durite and clarite. The limno-telmatic reed moor occurs in the transition to open-water swamp and is very frequent. Coals derived from this environment are characterized by high amounts of monstructured vitrinite, sporinite-rich clarite, trimacerite, associated with alginite and cutinite. The open-moor is the most productive in South Brazilian coal measures and is characterized by the presence of clay minerals in excess of 50% associated with carbargilite, trimacerite and high exinite (sporinite and/or alginite) content.
10. Petrographic Structures in an Australian and a Polish Coal, and their Change During Combustion
Margaretha Bengtsson (8 páginas)
resumo: For a closer evaluation of events that occur during combustion, samples were collected during four different trials conducted in a 4 MW test boiler. Besides conventional chemical analyses, the coal and char structures were also studied in these samples and the results are presented in this paper. A comparison between the chemical analyses and the behavior of coals in our 4 MW experimental furnace and our 10 MW pulverized fuel-boiler is also presented and discussed.
11. Petrology and Palynology of Mozambique Coals – Mucanha-Vúzi Region
R. M. S. Falcon ; M. J. Lemos de Sousa ; H. J. Pinheiro ; M. M. Marques (18 páginas)

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.

12. Significance of Vitrinite/Inertite Ratio in Lower Gondwana Coals of Peninsular India
G. K. B. Navale ; B. K. Misra (8 páginas)

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.

13. Sobre as Primeiras Medidas de Reactividade em Coques Realizadas na Siderurgia Nacional (Portugal)
Diamantino Pinheiro ; M. J. Lemos de Sousa (8 páginas)
resumo: Após uma introdução em que se resume o essencial sobre as funções do coque metalúrgico no alto forno e os critérios de qualidade do coque mais utilizados, nomeadamente a medida da reactividade (em termos de velocidade de gaseificação), descreve-se um aparelho que, devidamente adaptado, tornou possível iniciar o estudo da velocidade de gaseificação de coques em Portugal. Por fim, apresentam-se e discutem-se os primeiros resultados experimentais obtidos.
14. The Palynobiostratigraphy of the Major Coal Seams in the Witbank Basin With Lithostratigraphic, Chronostratigraphic and Palaeoclimatic Implications
R. M. S. Falcon ; H. J. Pinheiro ; P. Shepherd (30 páginas)

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.

15. The Petrological Characteristics of Lower Gondwana Coals from Part of the North Karanpura Coalfield and their Infiuence on Variations in Rank and on the Caking Properties of These Coals
B. C. Mukherjee (4 páginas)

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.

16. Usage of the Gondwana Coal for Metallurgical Coke-Making in Japan
Kenji Matsubara ; Takashi Miyazu ; Ryohei Takahashi (14 páginas)

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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