Most part of the energy demand on the planet is derived from petroleum, a nonrenewable energy source that releases large amounts of greenhouse gases in the atmosphere. Many researches have been devoted to the development of renewable energy sources that are less agressive to the environment. Biodiesel is a renewable, non-toxic and less polluent fuel, thus being a potential alternative to mineral diesel. It is produced from vegetable oils or animal fats. The transformation of vegetable oil into biodiesel by transesterification reaction consisting of a reaction between triglyceride oil and a lower alcohol, usually methanol or ethanol. The soil and climate in BR is attractive to a diversity of oil plants that can be used in biodiesel production. Among them, it can mentioned the castor bean, which grows in regions with low rainfall, as the semi - arid northeastern region. This work aimed to study the effect of stirring and mixing in the production of biodiesel from castor oil via transesterification and methyl alkaline catalysis process. Stirring rate, molar ratio oil / alcohol, the impeller type, the reaction time, the temperature, presence or absence of baffles and catalyst type. Therefore, a fractional factorial design 27-2, having as variables was used. We initially determined the physicochemical properties of castor oil. The experiment was performed in duplicate, with the biodiesel yield in each reaction determined by gas chromatography. Separately the effects of binary variables and their interactions were analyzed, providing the preparation of the statistical model for the yield of biodiesel from castor beans. The best conditions for production of biodiesel from castor oil via transesterification methyl were: turbine impeller; without baffles, stirring speed of 500 rpm, molar ratio oil / alcohol 1:7, NaOH catalyst, reaction time of 30 min and temperature of 50ºC. / A maior parte da energia consumida no planeta é proveniente do petróleo, fonte de energia não renovável que lança grande quantidade de gases poluentes na atmosfera. Nesse sentido, pesquisas têm sido desenvolvidas na procura de fontes de energia renovável, que poluam menos o meio ambiente. O biodiesel é um combustível renovável, não tóxico e menos poluente, sendo assim, uma ótima alternativa ao diesel mineral. Ele é produzido a partir de óleos vegetais ou gordura animal. A transformação do óleo vegetal em biodiesel ocorre através da reação de transesterificação, que consiste em uma reação entre os triglicerídeos do óleo e um álcool de cadeia curta, geralmente metanol ou etanol. O Brasil apresenta solo e clima propício para desenvolvimento de uma diversidade de oleaginosas que podem ser usadas na produção de biodiesel. Entre elas, pode-se citar a mamona, que se desenvolve em regiões com baixo índice pluviométrico, como o semiárido na região nordeste. Este trabalho teve por objetivo estudar o efeito da agitação e mistura no processo de produção de biodiesel de mamona, via transesterificação metílica e catálise alcalina. Para tanto, foi utilizado um planejamento fatorial fracionário 27-2, tendo como variáveis: velocidade de agitação, razão molar óleo/álcool, tipo de impelidor, tempo de reação, temperatura, presença ou ausência de chicanas e tipo de catalisador. Inicialmente foram determinadas as propriedades físico-químicas do óleo de mamona. Os experimentos foram realizados em duplicata, sendo o parâmetro de avaliação o rendimento em biodiesel da reação, determinado por cromatografia gasosa. Foram analisados isoladamente os efeitos das variáveis e suas interações binárias, proporcionando a elaboração do modelo estatístico para o rendimento em biodiesel de mamona. As melhores condições para produção de biodiesel de mamona via transesterificação metílica foram: impelidor tipo turbina; ausência de chicanas no reator; velocidade de agitação de 500 rpm; razão molar óleo/álcool de 1:7; hidróxido de sódio como catalisador; tempo de reação de 30 minutos; e, temperatura de 50ºC.

To quench a thermal runaway reaction in a chemical rector, an efficient approach is the introduction of a small quantity of a liquid inhibiting agent, named a “killer”, into the mixing vessel. In this thesis, an experimental approach has been coupled tightly with numerical modelling using Computational Fluid Dynamics (CFD). The first part of this thesis is devoted to a study of the hydrodynamics of partially-baffled mixing vessels, including the free-surface deformation caused by the central vortex. The use of an inhomogeneous, multiphase approach allowed simulation of the free-surface deformation. The capability of this novel method was demonstrated by very good agreement between the numerical predictions and experimental data. In the second part, liquid jet injection at the free-surface was coupled with the vessel hydrodynamics. Numerical results, obtained using an Eulerian-Lagrangian approach, have again shown good agreement with experimental data. These results allowed the jet trajectory to be modelled and its penetration into the agitated vessel was quantified. New mixing criteria were introduced that are specific to this application. Finally, the numerical methods validated at the pilot scale were applied at the industrial scale and allowed the proposal of practical improvements to the safety of the synthesis reactors studied