Biomass from forestry and agricultural sources has recently drawn a lot of attention as a new source of feedstock for energy and bio products. Size reduction is an important step in preparation of biomass as a feedstock. Each conversion process needs its own specific size or size distribution of particles. Modeling the size reduction process helps to optimize the design and control of the process while ensuring biomass particle sizes for an efficient biofuel conversion process. The objective of this study was to apply the population balance method for modeling the size reduction process. The model was applied to switchgrass size reduction by a grinder. Two population balance parameters, grinding rate (s⁻¹) and breakage distribution function (dimensionless) were estimated using experimental grinding data. The time dependent balance equations were solved using the Euler technique. The accumulation and depletion of the particles belonging to each size category were simulated as a function of time. The simulation predicted the residence time of particles inside the grinder in a way that the ground particles could meet the size and size distribution specifications for the downstream process. The thesis also describes preliminary steps in size reduction. Ground particles were fractionated based on their size by sieving. Weibull distribution was found to be the best probability density function to fit the data.

Mine-mill production faces several operational difficulties, such as fluctuations in ore delivery from mines, random failure of machines, usage of stockpiles and storage bins, and changeover time when switching products. This study was initiated at a particular Canadian mining company. However, changes in the economic condition in the mining industry during 2008 have meant that circumstances have changed to the extent that this work should be seen as an illustration of methods rather than a study of the specific situation at the mining company. This mining company will remain unnamed throughout this thesis. The purpose of this research is to develop a series of production campaigns, each of which uses a specific draw scheme to coordinate the receiving of ore, maintenance planning and product scheduling. The approach includes a combination of mathematical programming model and a simulation model. The solution from the integer programming model is a set of campaigns that minimize the inventory levels of unprocessed ore, the number of days on shutdown, and the number of active piles required at any point in time. The simulation model uses this solution as its production scheduling input with integrated stochastic elements to evaluate mill system performance. In this thesis, the formulation of the mathematical programming model and construction of the simulation model, as well as the maintenance data analysis used as stochastic element of the model is discussed.

Biomass from forestry and agricultural sources has recently drawn a lot of attention as a new source of feedstock for energy and bio products. Size reduction is an important step in preparation of biomass as a feedstock. Each conversion process needs its own specific size or size distribution of particles. Modeling the size reduction process helps to optimize the design and control of the process while ensuring biomass particle sizes for an efficient biofuel conversion process. The objective of this study was to apply the population balance method for modeling the size reduction process. The model was applied to switchgrass size reduction by a grinder. Two population balance parameters, grinding rate (s⁻¹) and breakage distribution function (dimensionless) were estimated using experimental grinding data. The time dependent balance equations were solved using the Euler technique. The accumulation and depletion of the particles belonging to each size category were simulated as a function of time. The simulation predicted the residence time of particles inside the grinder in a way that the ground particles could meet the size and size distribution specifications for the downstream process. The thesis also describes preliminary steps in size reduction. Ground particles were fractionated based on their size by sieving. Weibull distribution was found to be the best probability density function to fit the data.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1900. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed October 27, 2008)

Thesis (Ph. D.)--Columbia University, 1936. / Vita. Published also without thesis note. Bibliography: p. [201]-203.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 133-142b).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 131-136).

Thesis--Frankfurt a.d. Oder, 1703. / Date of publication from Kress Lib. Reproduction of original from Kress Library of Business and Economics, Harvard University. Goldsmiths'-Kress no. 03980.2.

Made available in DSpace on 2014-06-12T16:31:11Z (GMT). No. of bitstreams: 2 arquivo6050_1.pdf: 1162460 bytes, checksum: 5df4cba8ee99c3646cf4e626c8f65f61 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2004 / Ocimum campechianum Mill. é uma erva aromática conhecida popularmente no Brasil como alfavaca de cobra . Pode ser encontrada em Pernambuco e em outras regiões do país. Na medicina popular, é bastante utilizada como analgésico, antipirético, diurético, estimulante e antigripal. Este trabalho apresenta uma investigação acerca da atividade biológica e da composição química das folhas do vegetal. Os testes para avaliação da toxicidade aguda foram realizados através da observação de efeitos gerais sugestivos de ações sobre o sistema nervoso central e periférico, a partir dos quais foi determinada a DL50 que resultou em 1017,4 mg/kg de peso do animal. Um estudo histopatológico com tecidos provenientes dos testículos dos animais, que apresentaram cianose durante os experimentos, demonstrou não haver nenhuma alteração do material analisado. As atividades antiinflamatória, antitumoral e antimicrobiana também foram investigadas, resultando em uma inibição significativa dos tumores sarcoma 180 (47,34%) e carcinoma de Ehrlich (84,86%) e acentuada redução dos edemas na 4a hora do ensaio realizado para avaliar a ação antiinflamatória. Com relação à atividade antimicrobiana, os extratos não se mostraram ativos contra Staphylococus aureus, Micrococus flavus, Escherichia coli, Enterobacter sp., Candida albicans, Candida krusei. O screening cromatográfico realizado com os extratos benzênico e metanólico das folhas permitiu detectar a presença de polifenóis (fenilpropanoglicosídeos e flavonóides), monoterpenos e sesquiterpenos, triterpenos e esteróides, eugenol e açúcares redutores bem como a ausência de cumarinas, derivados cinâmicos, iridóides, proantocianidinas e leucoantocianidinas, alcalóides, saponósidos e taninos gálicos

Biomass from forestry and agricultural sources has recently drawn a lot of attention as a new source of feedstock for energy and bio products. Size reduction is an important step in preparation of biomass as a feedstock. Each conversion process needs its own specific size or size distribution of particles. Modeling the size reduction process helps to optimize the design and control of the process while ensuring biomass particle sizes for an efficient biofuel conversion process. The objective of this study was to apply the population balance method for modeling the size reduction process. The model was applied to switchgrass size reduction by a grinder. Two population balance parameters, grinding rate (s⁻¹) and breakage distribution function (dimensionless) were estimated using experimental grinding data. The time dependent balance equations were solved using the Euler technique. The accumulation and depletion of the particles belonging to each size category were simulated as a function of time. The simulation predicted the residence time of particles inside the grinder in a way that the ground particles could meet the size and size distribution specifications for the downstream process. The thesis also describes preliminary steps in size reduction. Ground particles were fractionated based on their size by sieving. Weibull distribution was found to be the best probability density function to fit the data. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate