This study investigated the influence of the attainable region technique to ball milling as applied in reactor technology. Flow rate, ball filling, mill speed, ball size and mill density were varied. When each was varied, the rest of the parameters were kept constant in-order to determine the influence of each parameter on the process of milling. Selection function and breakage function parameters were selected for the mill model. These were kept constant for all four circuit configurations: open milling circuit, normal closed circuit, reverse closed circuit, and combined closed circuit. Flow rate was varied from 10 tph to 150 tph. It was observed that in all circuit configurations the optimum results were obtained from 90 tph upwards. When ball filling was varied, the optimum results were obtained between 30 % and 40 % of ball filling. At this range the mill is neither experiencing under-filling nor over-filling. When the mill speed was varied, at 60 – 80 % of critical speed the product specification was achieved and for grinding balls, sizes of between 60 mm and 90 mm yielded the optimum results. Varying the mill density resulted in insignificant changes. From the results, the combined closed circuit produced more of the product specification. / School of Engineering / M. Tech. (Engineering: Chemical)

A escolha de um sistema de tratamento de efluentes deve levar em conta aspectos técnicos e econômicos, dentre os quais a eficiência do processo. Assim, o objetivo desta pesquisa foi avaliar a remoção de nitrogênio e fósforo em um reator anaeróbio-aeróbio de leito fixo, operado em escala de bancada, com recirculação da fase líquida. O reator, com volume útil de 6,95 L, foi operado com meio suporte de espuma de poliuretano e mantido à temperatura ambiente, sendo o efluente tratado sintético, simulando o esgoto sanitário. Foram testadas diferentes razões de recirculação (0,5; 1,0 e 1,5) e diferentes TDH (4, 8, e 12) e, com vazão de ar constante de 10 L min-1. Com a variação destes fatores foi possível verificar a influência da razão de recirculação na remoção de nitrogênio e fósforo e a influência do TDH na remoção de nitrogênio e fósforo. Durante o período de operação foram analisados os parâmetros físico-químicos: temperatura, pH, alcalinidade a bicarbonato, ácidos voláteis, oxigênio dissolvido, demanda química de oxigênio, demanda bioquímica de oxigênio, sólidos totais, sólidos suspensos totais, nitrogênio total kjeldahl, nitrogênio amoniacal, nitrito, nitrato e fósforo. Também foram realizados ensaios hidrodinâmicos por meio de testes estímulo-resposta tipo pulso com o traçador eosina Y, para avaliar o comportamento hidrodinâmico e verificar a existência de anomalias. E por fim realizou-se a análise estatística para encontrar a condição ótima de operação e os modelos estatísticos para validação. Tanto para a variação de razão de recirculação quanto para a variação de TDH, a temperatura, oxigênio dissolvido e pH contribuíram para o desenvolvimento dos microrganismos. A alcalinidade a bicarbonato e ácidos voláteis indicaram estabilidade no interior do reator. A razão de recirculação 50% foi a condição de maior eficiência de remoção para sólidos totais (83%). A razão de recirculação 100% foi a de maior eficiência para NTK (97%) e Namon (99%). Para a razão de recirculação de 150% a maior eficiência de remoção foi para fósforo (33%). Avaliou-se também a influência da sobrecarga hidráulica no desempenho do reator quanto à remoção de nitrogênio e fósforo e foi possível perceber que o TDH de 12 h foi a condição que resultou em maiores eficiências de remoção. E em relação ao comportamento hidrodinâmico do reator, ele se assemelha a mistura completa, isso pode ser verificado por meio das curvas DTR e coeficientes de correlação. Quando variado o TDH observou-se a presença de zonas mortas (exceto para o TDH de 12 h), que indica ocorrência de caminhos preferenciais. No TDH de 12 h foi observado curto circuitos hidráulicos e eficiência hidráulica insatisfatória. Pela análise estatística no delineamento do composto central rotacional, foi possível encontrar por meio da desejabilidade a condição ótima de operação com TDH de 12 h e razão de recirculação de 122,36%. Ainda foi possível encontrar os modelos estatísticos para nitrificação, desnitrificação e nitrogênio total e valida-los para as condições operadas. / The choice of an effluent treatment system must take into account technical and economic aspects, among which the process efficiency. The objective of this research was to evaluate the removal of nitrogen and phosphorus in an anaerobic-aerobic fixed bed reactor, operated at bench scale, with recirculation of the liquid phase. The reactor, with a volume of 6.95 L, was operated with polyurethane foam support and maintained at room temperature with the synthetic effluent treated by simulating the sewage. Different recirculation ratios were tested (0.5, 1.0 and 1.5) and different HRT (4, 8, and 12) with constant air flow rate of 10 L min-1. With the variation of these factors was possible to verify the influence of the recirculation ratio on nitrogen removal and the influence of HRT in removing nitrogen. During the operation period, was analyzed the physical and chemical parameters: temperature, pH, bicarbonate alkalinity, volatile acids, dissolved oxygen, chemical oxygen demand, biochemical oxygen demand, total, total suspended solids solids, nitrogen total kjeldahl ammonia nitrogen , nitrite, nitrate and phosphorus. It was also developed hydrodynamic tests through stimulus-response pulse with eosin Y tracer to evaluate the hydrodynamic behavior and check for abnormalities. And finally, there was the statistical analysis to find the optimal operating condition and statistical models for validation. For any variation due to recirculation as variation of HRT, temperature, dissolved oxygen and pH contributed to the development of microorganisms. The bicarbonate alkalinity and volatile acids indicated stability within the reactor. The recirculation ratio 50% was highest efficiency condition for total solids removal (83%). Recirculation ratio 100% was the highest efficiency for TKN (97%) and Namon (99%). A recirculation ratio of 150% was a higher removal efficiency for phosphorus (33%). It was also evaluated the influence of hydraulic overload in the reactor performance as the removal of nitrogen and phosphorus and it was revealed that the HRT of 8 h was the condition which resulted in higher removal efficiencies. Regarding hydrodynamic behavior of the reactor, it resembles complete mixture, verified by DTR curves and correlation coefficients. When varied HRT can observe the presence of dead zones (except for HRT of 12 h), which indicates occurrence of preferential paths. In HRT of 12 h was observed hydraulic short circuits and poor hydraulic efficiency. For the statistical analysis in the design of the central composite, was found by the desirability optimum operation condition with HRT of 12 h and recirculation ratio of 122.36%. It was still possible to find statistical models for nitrification, denitrification and total nitrogen and validates them for the operated conditions.

Orientadores: Rubens Maciel Filho, Liliane Maria Ferrareso Lona / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T02:31:19Z (GMT). No. of bitstreams: 1 MendozaMarin_FlorentinoLazaro_D.pdf: 8929110 bytes, checksum: 9041b9e7f02f9a324fa10cde9a962f54 (MD5) Previous issue date: 2004 / Resumo: O modelo determinístico e processo homopolimerização na emulsão do estireno são aplicados em reator tubular contínuo sem e com deflectores angulares internos sob condição isotérmica e não isotérmica. Os resultados de modelagem e simulação foram realizados a estado estacionário, modelo unidimensional, coordenada cilíndrica, fluxo pistão laminar completamente desenvolvido, modelo Smith-Ewart para estimar a conversão do monômero, cinética química de Arrhenius corno modelo de velocidade finita laminar para computar a geração química. O objetivo é modelar, simular e analisar o comportamento do reator de homopolimerização na emulsão do estireno com deflectores angulares inclinados internos, e comparar com reator tubular. Os métodos experimental e matemático-dedutivo foram aplicados para obter resultados, por meio de programação computacional, usando Dinâmica de Fluido Computacional através do método de volumes finitos. As seguintes variáveis como temperatura de reação constante e variável, reator tubular sem e com deflectores, temperatura de alimentação, diâmetro de reator, processo adiabático e exotérmico, calor de reação constante e velocidade axial completamente desenvolvida foram investigados. Os efeitos de conversão de monômero, área transversal interna, temperatura axial, concentração do polímero, radicais e iniciador, outros corno densidade de polímero e monômero, perda de carga e queda de pressão foram determinados e simulados. Os produtos foram caracterizados com Número de Partículas (nucleação homogênea e heterogênea), distribuição de peso molecular, tamanho de partículas de polímero e distribuição de viscosidade. Estes resultados foram validados com resultados da literatura sob condição igualou aproximada. Os resultados sob condições não isotérmicas foram melhores que os resultados isotérmicos em termos de caracterização do polímero. Isso mostra que o desenho alternativo proposto (com deflectores) permite obter o polímero com propriedades melhores em termos de número de partículas, distribuição de peso molecular, distribuição do tamanho de partículas e viscosidade / Abstract: Deterministic model and emulsion homopolymerization process of styrene are applied in continuous tubular reactor without and with internal angular baffles under isothermic and no isothermic conditions. The modeling and simulation results were approximate to steady state, one-dimensional model, cylindrical coordinate, fully developed laminar plug flow, Smith-Ewart model to estimate the monomer conversion, Arrhenius chemical kinetics as laminar finite-rate model to compute chemical source. The objective is to model, simulate and to analyze the emulsion homopolymerization reactor performance of styrene with internal-inc1ined angular baffles, and to compare with continuous tubular reactor. The experimental and mathematical-deductive methods were applied to obtain results, by means of computational programming, using Computational Fluid Dynamics (program code), finite volume method. The following variables such as constant and variable reaction temperature, tubular reactor without and with baffles, feed temperature, reactor diameter, adiabatic and exothermic process, constant reaction heat and fully developed axial velocity were investigated. The monomer conversion, internal transversal are a, axial temperature, concentration of polymer, radicals and initiator, others as density of polymer and monomer, head loss and pressure drop effects were determined and simulated. The products were characterized by partic1es number (homogeneous and heterogeneous nuc1eation), molecular weight distribution, polymer partic1es size and polymer viscosity distribution. These results were validated with literature results under same or approximate condition. The results under no isothermic conditions were better than isothermic results in terms of polymer characterization. It is shown that the proposed alternative design (with baffles) allow to obtain the polymer with better properties in terms of number of partic1es, molecular weight distribution, particle size distribution and viscosity / Doutorado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Indiana University-Purdue University Indianapolis (IUPUI) / Ignition of a combustible mixture by a transient jet of hot reactive gas is important for safety of mines, pre-chamber ignition in IC engines, detonation initiation, and in novel constant-volume combustors. The present work is a numerical study of the hot-jet ignition process in a long constant-volume combustor (CVC) that represents a wave-rotor channel. The mixing of hot jet with cold mixture in the main chamber is first studied using non-reacting simulations. The stationary and traversing hot jets of combustion products from a pre-chamber is injected through a converging nozzle into the main CVC chamber containing a premixed fuel-air mixture. Combustion in a two-dimensional analogue of the CVC chamber is modeled using global reaction mechanisms, skeletal mechanisms, and detailed reaction mechanisms for four hydrocarbon fuels: methane, propane, ethylene, and hydrogen. The jet and ignition behavior are compared with high-speed video images from a prior experiment. Hybrid turbulent-kinetic schemes using some skeletal reaction mechanisms and detailed mechanisms are good predictors of the experimental data. Shock-flame interaction is seen to significantly increase the overall reaction rate due to baroclinic vorticity generation, flame area increase, stirring of non-uniform density regions, the resulting mixing, and shock compression. The less easily ignitable methane mixture is found to show higher ignition delay time compared to slower initial reaction and greater dependence on shock interaction than propane and ethylene. The confined jet is observed to behave initially as a wall jet and later as a wall-impinging jet. The jet evolution, vortex structure and mixing behavior are significantly different for traversing jets, stationary centered jets, and near-wall jets. Production of unstable intermediate species like C2H4 and CH3 appears to depend significantly on the initial jet location while relatively stable species like OH are less sensitive. Inclusion of minor radical species in the hot-jet is observed to reduce the ignition delay by 0.2 ms for methane mixture in the main chamber. Reaction pathways analysis shows that ignition delay and combustion progress process are entirely different for hybrid turbulent-kinetic scheme and kinetics-only scheme.