Thesis. 1976. Sc.D.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / Microfiche copy available in Archives and Science. Incorrect foliation: leaves 204-219 are bound between leaves 238 and 239. / Vita. / Bibliography: leaves 385-427. / by John H. Pohl. / Sc.D.

Thesis. 1977. Sc.D. cn--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 222-228. / Sc.D.cn

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Economics, 1977. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND DEWEY. / Bibliography: leaves 157-163. / by Leslie I. Boden. / Ph.D.

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography : leaves 75-76. / M.S.

Este trabalho é um estudo híbrido, prospectivo e transversal, de uma coorte de 280 mineiros de carvão de subsolo, selecionados por possuírem espirometrias aceitáveis nas investigações de 1984 e 1989. Em ambas as ocasiões, êles responderam a questionários de sintomas respiratórios e exposições ocupacionais, fizeram espirometrias, e foram submetidos a uma radiografia do torax. Em 1989, em adição, fizeram um teste de provocação brônquica inespecífica. Os métodos de análise empregados foram: análises descritivas, medidas de associação, análises de variância , e modelos de regressão logística e linear. Em 1989, as médias e os desvios-padrão de idade e de anos de subsolo era de 34,9± 5,1, e 10,4 ± 3,9, respectivamente. Todos os mineiros eram do sexo masculino e 252 (90 por cento ), brancos. A tosse, e o catarro foram os sintomas predominantes em ambas as ocasiões. No seguimento, 27,9 por cento dos mineiros apresentavam sintomas compatíveis com bronquite crônica. O chiado foi o único sintoma a evoluir significativamente durante o período de observação. A tosse, o catarro e a bronquite crônica, foram fundamentalmente dependentes do tabagismo e reversíveis com o abandono do hábito, ao passo que a dispnéia e o chiado associaram-se à exposição ocupacional. Dezoito por cento dos mineiros tinham sintomas compatíveis com asma, em 1989, enquanto 12,1 por cento referiram sintomas compatíveis com asma ocupacional. Destes últimos, 44,1 por cento apresentaram hiperreatividade brônquica. A prevalência de pneumoconiose foi de 5,4 por cento em 1984, e 7,9 por cento em 1989. A incidência anual de PMC foi de 11,4/1.000 mineiros expostos. A progressão radiológica associou-se significativamente à exposição ajustada, tabagismo, ao componente sinérgico entre exposição e tabagismo, e a um VEF1 mais baixo. Mineiros com opacidades irregulares ao Rx tenderam a apresentar uma pior função pulmonar. Houve um discreto crescimento da CVF média da coorte durante os 5 anos. O VEF1 e o IT declinaram no mesmo período. O VEF1 identificou apenas 2,5 por cento mineiros com valores anormais, enquanto que o IT identificou 15,7 por cento . O tabagismo foi o principal fator associado a alterações espirométricas. Em relação ao IT, houve ainda um efeito significante do componente sinérgico da exposição e do tabagismo. A hiperreatiVidade brônquica associou-se significativamente a resíduos negativos do VEF1 e do IT. O declínio longitudinal do VEF1 foi superior ao calculado transversalmente, em 1984 e 1989, e superior ao declínio previsto em indivíduos normais. A hiperreatividade brônquica associou-se, também, a um declínio acelerado do VEF1. Concluimos que os resultados aqui descritos são uma estimativa conservadora dos efeitos reais da exposição ocupacional, devido à seleção da coorte, e também a outros vieses. Há fortes indícios da presença de asma ocupacional neste grupo, assim como uma elevada incidência de PMC, e um declínio acelerado do VEF1. O tabagismo foi o principal fator de risco relacionado à deterioração funcional, em mineiros de carvão ativos, com uma média de 10 anos de subsolo, porém houve um efeito potencializador da exposição ocupacional. / This is a hybrid study in a cohort of 280 coalminers, with both prospective and cross sectional components. They were selected when they succeded in having acceptable spirometries and attended the 1984 and 1989 investigations. On both occasions they were submitted to a questionnaire of respiratory symptoms and occupational exposures, spirometry, and a chest x-ray. In addition, in 1989, they had a nonspecific bronchial challenge test. The statistical methods included, descriptive analysis, measures of association, analysis of variance, and logistic and linear regression models. In 1989, the mean age and the mean number of years of exposure were, 34.9 .±. 5.1, and 10.4 .±. 3.9, respectively. All miners were male, and 252 (90 per cent ) white. Cough and phlegm were the most prevalent symptoms. In the follow up, 27.9 per cent had symptoms of chronic bronchitis. Wheezing was the only symptom that increased significantly during the observation period. Cough, phlegm and chronic bronchitis were basically associated with smoking, and reversible upon the cessation of the habit, whereas breathlessness and wheezing were associated with dust exposure. In 1989, 18 per cent of the miners had asthma symptoms, and 12.1 per cent had symptoms compatible with occupational asthma. Forty-four percent of thela ter had bronchial hyperresponsiveness. The prevalence of pneumoconiosis was 5.4 per cent in 1984, and 7.9 per cent in 1989. The annual incidence of CWP was 11.4/1,000 miners at risk. Radiological progression was significantly associated with adjusted exposure, smoking, an interacion term involving exposure and smoking, anda low FEV1 Irregular opacities on the x-ray were non-significantly associated with a worse pulmonary function. During those 5 years there was a discrete growth in the mean FVC. The FEV1 and the FEV1/FVC per cent declined in the same period. The FEV1 identified only 2.5 per cent miners with abnormal results, whereas the FEV1/FVC per cent identified 15.7 per cent . Smoking was the main variable associated with spirometric abnormalities. The interaction term of exposure and smoking was also significantly associated with an abnormal FEV1/FVC per cent . Bronchial hyperresponsiveness was significantly associated with negative FEV, and FEV1/FVC per cent residuais. The longitudinal decline of the FEV1 was greater than the cross-sectional decline, both in 1984 and 1989, and also greater than the predicted decline in normal adults. Bronchial hyperresponsiveness was also associated with a rapid decline in FEV1. We conclude that these findings are an underestimate of the real effects of the dust exposure, because of the cohort selection, and also because of other bias. There are strong evidences of the ocurrence of occupational asthma, of a high incidence of CWP, and of a rapid decline the FEV1 in this cohort. Smoking was the main factor linked to functional deterioration in active coalminers with a mean of 10 years of exposure, but there was a synergistic effect of dust exposure.

Insufficient knowledge of fireside behavior in the near-burner region during biomass combustion is one of major factors preventing widespread use of this renewable fuel in pulverized coal power plants. The current research is aimed to investigate the impact of biomass cofiring on NO formation in the near-burner region through interpretation of computational fluid dynamics (CFD) predictions and data collected from a series of biomass tests in a pilot-scale (0.2 MW), swirling flow burner. Two-dimensional gas species mole fraction data were collected with state-of-theart instruments from nine experiments, composing one herbaceous biomass (straw), one woody biomass (sawdust), a low sulfur sub-bituminous coal (Blind Canyon) and a high sulfur bituminous coal (Pittsburgh #8) and their mixtures of different mass fractions with the same swirl setting. Velocity and temperature are calculated from CFD modeling with FLUENTTM, supplemented with hot-wire anemometer measurements. For the first time, a reverse flow region was predicted during solid fuel combustion simulations for the reactor used. Interpretation of the results was carried on with two original methods: stoichiometric maps and normalized species mole fraction profiles. The impacts of biomass on combustion in the swirling flows were analyzed from several aspects: aerodynamics, fuel properties (particle size, volatile content, and fix-carbon content), and NO formation routes. The species maps show the low-grade fuel combustion under swirling flows is composed of two zones: a high species-gradient combustion region attached to the inlet and flat-profiles dominant across the rest of the reactor. Results from tests involving biomass clearly demonstrate the expansion of the combustion region. CFD calculations demonstrate that there is no obvious alteration of the reverse-flow region by biomass combustion. The larger average particle size of biomass generates a combustion region with further penetration into the reactor. In certain tests involving biomass, more NH3 than HCN was detected in several biomass experiments, though limited by the data collection method and low fuel-nitrogen fuels used (sawdust). Supplemented with kinetic calculations with CHEMKIN, it was found that NO formation is dependent on the nitrogen forms in the parent fuels.

A gradual increase in the price of oil, a decline in the supply of gas, and a lag in nuclear construction leaves coal (a potential major resource for the future energy needs) as a fuel in ample supply. The major portion of the United States' electricity is generated by steam-driven generators where steam is produced by fossil fuel-fired boilers. In 1978, 47 percent of the total electricity generation was fueled by coal, up from 43 percent in 1975. Use of coal in generation of electricity has spawned numerous research projects concerning the economics of the coal-fired electric power industry. The majority of the empirical works employed estimates of cost or production functions derived from the traditional strong separable functions (i.e., Cobb-Douglas or Constant Elasticity Substitution models). In the case of multiple-output, multiple-input models, constancy of elasticity of substitution proves to be highly restrictive. Limitations of conventional models have motivated the use of more general models, specifically the transcendental logarithmic function which imposes no separability restriction a priori. Absence of new empirical studies for the industry, provides sufficient justification for the empirical study of the economic relationship between inputs and outputs in the coal-fired electric power industry. Also absent in previous works is the element of machine mix and air pollution control factors. The analysis of substitution possibilities between inputs and the existence of a technological change from the objectives of the present study. Substitution and price demand elasticities are estimated which provide guidelines and useful information for planning and design of optimally more efficient coal-fired power plants. These estimated elasticities can be used to analyze the impacts of some selected government or industry policies, or they can provide guidance in further policy development and research. A transcendental logarithmic multiple-input, multiple-output cost function is adapted to the cross-section data of the coal-fired electric power industry for 1973 at the plant level. The maximum-likelihood ratio test is used to empirically test the validity of various restrictions on the productive structure. The model used in this study provides for a share-specific elasticity to be computed for each price and share observation. Results drawn from this study suggest that models with constant elasticity of substitution (i.e., Cobb-Douglas, and the Constant Elasticity Substitution and Separable models) do not appropriately represent the structure of the United States' coal-fired electric power industry. Although the empirical findings at the industry level provide substitution possibilities can be found for several vintages. Scale economies are present; and contrary to the findings for the power industry, it was found that the coal-fired power plants do not operate on the flat portion of the average cost curve.

Fluidization characteristics and co-gasification of pulverized sub-bituminous coal, hybrid poplar wood, corn stover, switchgrass, and their mixtures were investigated. Co-gasification studies were performed over temperature range from 700°C to 900°C in different media (N2, CO2, steam) using a bubbling fluidized bed reactor. In fluidization experiments, pressure drop (ΔP) observed for coal-biomass mixtures was higher than those of single coal and biomass bed materials in the complete fluidization regime. There was no systematic trend observed for minimum fluidization velocity (Umf) with increasing biomass content. However, porosity at minimum fluidization (εmf) increased with increasing biomass content. Channeling effects were observed in biomass bed materials and coal bed with 40 wt.% and 50 wt.% biomass content at low gas flowrates. The effect of coal pressure overshoot reduced with increasing biomass content. Co-gasification of coal and corn stover mixtures showed minor interactions. Synergetic effects were observed with 10 wt.% corn stover. Coal mixed with corn stover formed agglomerates during co-gasification experiments and the effect was severe with increase in corn stover content and at 900°C. Syngas (H2 + CO) concentrations obtained using CO2 as cogasification medium were higher (~78 vol.% at 700°C, ~87 vol.% at 800°C, ~93 vol.% at 900°C) than those obtained with N2 medium (~60 vol.% at 700°C, ~65 vol.% at 800°C, ~75 vol.% at 900°C). Experiments involving co-gasification of coal with poplar showed no synergetic effects. Experimental yields were identical to predicted yield. However, synergetic effects were observed on H2 production when steam was used as the co-gasification medium. Additionally, the presence of steam increased H2/CO ratio up to 2.5 with 10 wt.% hybrid poplar content. Overall, char and tar yields decreased with increasing temperature and increasing biomass content, which led to increase in product gas.

The Early Jurassic coal samples for the study were obtained from CRA Exploration Pty Ltd. (CRAE), drilled in the Gairdner and Mintaja Blocks, Gairdner Range of the Hill River Area, northern Perth Basin, Western Australia. The area is located approximately 280 km north of Perth. The coal measures subcrop in a half- graben bounded by the Lesueur-Peron Fault in the west, and the Warradarge Fault in the east. The coal occurs within the shallow sequence of the Cattamarra Member which is also described as the Cattamarra Coal Measures of the Cockleshell Gully Formation.Six sub-seams of seam G, namely G1 to G6, from the six drill cores, were examined for petrological and geochemical investigation. The coal predominantly comprises of banded, dull banded, and dull lithotypes, with minor bright banded, bright and fusainous types. Based on maceral analyses, the dominant maceral groups are vitrinite and inertinite, whilst the exinite and mineral matter are in minor contents. The vitrinite content has a range between 47.2 % to 73.0 %, and it is composed mainly of telocollinite and desmocollinite. The inertinite is dominated by semifusinite, fusinite, and inertodetrinite, and it has a range from 10.4 % to 24.8 %. The exinite group varies between 7.2 % to 20.8 % in content, and it is represented by sporinite, cutinite, alginite and resinite. The mineral matter dominated by clays and pyrite, ranges between 4.5 % to 20.6 %. The microlithotype analyses shows that the vitrite plus clarite content varies from 47.0 % to 70.0 %, intermediates between 8.0% to 26.0 %, whilst inertite plus durite content is relatively low, varying from 6.55 % to 14.0 %. The maximum reflectance of vitrinite has a value between 0.47 % and 0.53 %, which represents rank at sub-bituminous level based on the Australian rank values and corresponding to the sub-bituminous A and B rank of the ASTM classification and ++ / to the metalignitous type of the Pareek classification. On the basis of carbon and hydrogen content, the coal is categorised as per-hydrous meta- to ortho-lignitous type. The trace elements As, B, Be, Cd, Co, Cr, Cu, Ga, Mn, Mo, Ni, Pb, Sr, Th, U, V, Y, Zn, and Zr, are spectrographically analysed in the coal ash. The B content in the coal supports the presence of marine influence during peat deposition in the basin.On the basis of lithotype, maceral, microlithotype, trace element distribution, pyrite and total sulphur in the coal, the depositional environment for coal and the coal measures, is interpreted as an upper to lower delta type within a regressive phase of marine transgression.

Tailgate stability within longwall coal mining is critical to longwall productivity and safety of mine personnel. A mechanistic model was developed and tested to explain observed high deformation tailgate behaviour characterised by lateral strata movement. Field investigations were conducted at three Australian longwall mines with an emphasis on the measurement of; horizontal strata movement about gateroads during longwall extraction, and the load/deformation characteristics of standing supports. 3D numerical modelling was used to simulate tailgate deformation, and interaction of various support types and design strategies. The sensitivity of strata and support behaviour to; variations in roof geology, strength of sliding interfaces, depth of cover, pre-mining horizontal stress magnitude and orientation, and strength and stiffness characteristics of standing supports was modelled. Laboratory investigations of a standing support product, the ???Can???, at reduced scale (one third) were conducted. The tests determined the loading mechanics of the product and provided a basis for optimisation of the engineering properties (strength and stiffness). Horizontal strata movement about longwall extraction was found to have a significant impact on strata behaviour at two of the three mines investigated. The term ???skew roof??? was coined to describe the deformation process. Essentially the roof strata was found to ???skew??? towards the approaching goaf. The key geotechnical factors found to control the skew roof mechanism were; magnitude and orientation of the pre-mining horizontal stress, presence of weak interfaces along which sliding could occur, and shear strength of the interfaces. Measurement of the nature and extent of skew roof deformation specific to each mine provided a sound engineering basis for support design. These included; the relative roles of long tendons versus standing support, optimal pattern (position across and along the roadway) of standing supports, and appropriate strength and stiffness characteristics. The findings were successfully implemented at Metropolitan Colliery in particular, where adequate tailgate serviceability has been achieved within a high deformation environment, and whilst maintaining a relatively small chain pillar width. The research has achieved an alternative to empirical and trial and error tailgate support design methods.