RCAAP Repository

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

The increasing activity of oil and gas extraction in deep water has stimulated several studies to solve problems encountered in drilling wells. During the drilling operation, a fluid (drilling mud) is pumped through the column to the bottom, carrying to the surface the drill cuttings generated, through the annular space formed between the column and the borehole wall. In this type of flow may appear a kind of hydrodynamic instability characterized by the appearance of toroidal vortices. This type of instability (Taylor-Couette) may profoundly alter the pressure drop of the flow, the shear stress at the borehole wall and the ability of carrying the solids. Moreover, during the process of drilling a well it is necessary promotes the well cementing and coating to provide a mechanical support, as well as, to isolate it from different rock formations traversed. For this step to be successful, the drilling mud must be completely removed from the annular space, and this removal may be impaired in wells which have varying eccentricity along the tube. Due to high costs of correction transactions and loss of drilling time, it is crucial to predict the mud flow around the annular. The effects of this variation of the eccentricity have not been much discussed in the literature, and they may have great influence on the displacement of the mud in the annular space. As an initial phase of work, numerical simulations were performed to study the flow and the emergence of Taylor- Couette instabilities in a concentric annular section, in order to compare them with literature data. Numerical simulations were developed in annular periodic sections, concentric and eccentric (E = 0.5) in order to obtain average profiles of axial and tangential velocities using different turbulence models, aiming at a comparison of simulated results with experimental data from literature. Later, it was made an experimental study and simulation to assess the effect of internal axis rotation on the pressure drop in the flow of non-Newtonian fluids (aqueous solutions of xanthan gum and carboxymethyl cellulose with 0.2% by weight) in a section annular concentric and the other with fixed eccentricity (E = 0.75). Finally, it was elaborated an experimental design (3k) with four variables, such as, xanthan gum concentration (0.05%, 0.10% and 0.15% by weight), eccentricity (0.0, 0.23 and 0.46), fluid flow rate (5, 7 and 9 m3/h) and internal rotation axis (0, 100 and 200 rpm). Following this planning, experimental data of pressure drop were collected, as well as, numerical simulations (CFD) in periodic annular sections to get results of axial velocity, in order to evaluate the effect of variable eccentric rotation on the fluid dynamics of non-Newtonian flows in annular spaces.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Pyrolysis is considered to be the most promising thermal conversion technology. The possibility of producing specialty chemicals and higher added value products makes the process very attractive when compared to other sources of green energy. Pyrolysis is characterized by thermal degradation of the solid fuel, what imply on the rupture of carbon-oxygen bond. The products formed during pyrolysis, as coal fines, gases, and volatiles (acid extract and bio-oil), have high calorific power and have been had many application in chemical industries and in energy generation. The chemical reactor is the main element of the applied chemical processes and for showing a good solid-gas contact, high mass, heat transfer and particle recirculation rates, the spouted and fluidized bed have become efficient options to the success of fast pyrolysis because they prone the physic-chemical processes that occur during pyrolysis. This work has as main objective, to study the fundamental aspects of the biomass pyrolysis in spouted bed that are highly important to the process optimization. Among these aspects, the pyrolysis kinetics and the fluid dynamic behavior of the fluid and the particles inside the equipment stand out. The pyrolysis kinetics of the sugarcane bagasse was analyzed, using experimental data of mass loss by thermogravimetry. The parameters of some of the main kinetic models available on literature were estimated. The results were compared and the model that best represents the data was chosen. The results of the investigation of the primary thermal degradation kinetics showed that the mass loss during thermogravimetry is best represented by parallel and independent reactions of its subcomponent. The calculated values of activation energy allow presuming the necessary amount of energy for the reaction to occur. Regarding the fluid dynamics of the process, the particle mixing experiments in spouted bed allowed a better comprehension of the segregation mechanisms in the equipment. Segregation occurs due to the different terminal velocities of the particles, which may occur due to size and density differences. Tests with glass spheres of different diameter showed that the bigger particles concentrate mainly on the superior annular region. Regarding particles with different densities and same size, represented by the mixing of glass sphere and polyethylene with same diameter, it was observed that the less dense particles, polyethylene, concentrate on the superior region of the bed. It may have occurred due to the low elasticity of the collision of the low density particles with the wall and its difficult on sliding into the wall. In this case, it was defined the minimal spout condition as being the air flow that both particles spout and an increase on the air flow did not cause changes on the pressure drop. Varying the particle size and density, experiments in spouted bed using bagasse and sand in different compositions were carried out. In this step, it was identified a range of composition in which the mixture shows good circulation in the bed, as it was evaluated the particle segregation index in bed. CFD simulations involving a multiphase dense system, with more than one particulate phase, were compared to the data obtained experimentally using glass spheres with different diameters, showing good prediction of the axial distribution data of the volumetric fraction of particles. Beyond that, data about the particle segregation in spouted bed, available on literature, were also reproduced by simulation using CFD. The knowledge of the kinetic and fluid dynamic of the process is the initial and preponderant step to implementation of pyrolysis process in pilot scale. As the determination of the ratio between sand mass and biomass is the critical point of the pyrolysis process, a good understanding of the segregation mechanisms of particle mixtures may help on the identification of the optimum conditions to operate the reactor.

Universidade Federal do Triângulo Mineiro

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Because of advantages such as low cost, simple structure, large capacity of suspension processing and small dimensions, hydrocyclones are widely used for separating dispersed phase (liquid or solids) from continuous one. The shape and size of a hydrocyclone has a decisive effect on the internal flow structure of the continuous phase, and therefore, the separation or classification of the dispersed phase. Therefore, several geometric changes have been suggested to improve the particle separation efficiency and reduce energy costs of hydrocyclones. In a work of hydrocyclones optimization, Vieira (2006) studied the influence of the main geometrical variables on the performance of the separators, from what he found a hydrocyclone with good separation efficiency and low energy cost, the so-called HC11. In the present work, new geometrical changes have been incorporated to the hydrocyclone HC11 and the impacts of those changes have been evaluated experimentally and by CFD techniques. The proposed geometrical changes were: the modification of the wall thickness of vortex finder; the use of a mantle type vortex finder; the use of a ramped roof feed inlet and the use of a rotating feed. The results indicated that all the proposed modifications have changed the performance of the separator and that it is possible improve the standard HC11. Moreover, based on the data of Vieira (2006), three new geometrical configurations of hydrocyclones have been found through the use of response surface technique combined with the Differential Evolution algorithm. The results obtained through the optimization techniques have been validated by experimental data. The optimized configurations of hydrocyclones found were: (i) hydrocyclone HCOT1, with high separation efficiency (η=85.5%); (ii) hydrocyclone HCOT2, with low underflow-to-throughput ratio (RL=9.37%) and (iii) hydrocyclone HCOT3, with low Euler number (Eu=788) and low underflow-to-throughput ratio (RL=5.08%).

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

The element phosphorus plays key role in plants metabolism. It is widely used as fertilizer. This element is usually found in insoluble forms (Ca10(PO4)6F2). The solubilization in phosphoric acid and/or superphosphates (SSP or TSP) processes are widely used in the fertilizer industry. Impurities (also called contaminants) contained in phosphates exert a significant influence on the processing of fertilizers as well as the quality of intermediates and final products. The objective of this work was to analyze the influence of some of these main impurities (iron, aluminum and magnesium) in the production chain TSPG fertilizer, which is the production of phosphoric acid, the acidulation of TSP and finally granulation of TSPG. Bench experiments were performed at each step. The contaminants concentrations from processing steps are interrelated in order to achieve a systemic analysis of the processing chain. The premises for the application of methodologies were playing the most typical parameters from industrial application. Igneous phosphate concentrate was used in the experiments. For contaminants concentrations variations were used magnetite (Fe2O3 source), the metal aluminum (Al2O3 source) and magnesium hydroxide (MgO source). Reductions in conversions, increases in viscosity and density of phosphoric acid were observed with increasing presence of these impurities. In the phosphogypsum filtration there was found an increase in resistivity of the cake with the increase of the impurities content. The iron mineral element promoted an increase in induction time of crystals nucleation. The increasing impurities concentration in the TSP acidulation caused reductions in P2O5 conversions (Neutral Ammonium Citrate soluble and Water Soluble), that caused the increased levels of residual phosphoric acid and free moisture in the TSP. An analysis of the specification for the TSP granulation in TSPG presented upper limit of impurities (MER) from phosphate concentrate around 0.15. The granulation of TSPG showed effects from the TSP, i.e., higher levels of residual phosphoric acid in the TSP assigned greater hardness, higher hygroscopicity and higher granulation factor to TSPG. The bench tests reproduced the current industrial setting.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Universidade Federal de Goiás - Goiânia

In this work the homolactic fermentation of cheese whey using Lactobacillus helveticus (ATCC 15009) was studied. The experiments were carried out in a batch reactor, with agitation, temperature and pH control during a period of 32 hours. The influences of four variables according to a composite design on the production of lactic acid were analyzed: temperature, pH, concentration of lactose and concentration of yeast extract, used as a supplement for the fermentation medium. The effects of these variables and its interactions were analyzed by the response surface methodology. The biggest influences were exerted by pH and by the concentration of yeast extract. Through a canonic analysis of the adjusted response surface, the optimal variables values that led to the biggest production of lactic acid were determined: 82 g/L of lactose, 23.36 g/L of yeast extract at 40 ºC and pH 6.8. In these conditions, the concentration of the lactic acid reached 59 g/L. Through a kinetic study, it was proved that the homolactic fermentation of whey is inhibited by the substrate as well as by the product. Models were tested to describe the microbial growth, the substrate consumption and the product formation. The logistic equation represented well the growth of the Lactobacillus helveticus. The biggest deviations occurred at the beginning of the fermentation and at the stationary phase, where the condition of instantaneous rate of growth equal to zero is not predicted by the model. The measures of bias from Box and of curvature from Bates and Watts referring to this model demonstrated that there is a statistic confidence for the least square estimators of the parameters. The adjustment of the growth model from Amrane (1999) for the experimental data was slightly better than the one obtained from the logistic equation. However, the measures of bias from Box and of curvature from Bates and Watts demonstrated that the statistical inferences on the parameters estimative are not valid. Therefore, the possibility of using this model was discarded. The models of substrate consumption from Pirt and of formation of product from Luedeking and Piret fitted well to the experimental data.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Researches are done with the aim of select yeast strains that plays a differentiated role in the process of alcoholic fermentation, with the purpose of improve the performance in the ethanol production and decrease the productions costs. In this work it was studied the application of Saccharomyces cerevisiae yeasts with flocculent features in fed batch reactor. It was evaluated the fermentative capacity of six strains of flocculent yeasts. The yeast C2/00 was involved in higher productivity and yield in ethanol compared to other yeasts tested. After it was studied the alcoholic fermentation in fed batch reactor using the yeast C2/00. The fermentations were performed at 32°C and initial pH adjusted in 4.5. The process was optimized in sucrose concentration of 170 g/L, cell concentration in the inoculum of 40% (v/v) and filling time of 6 hours, it is obtaining a yield of 92.20% in relation to the theoretical one, productivity of 6.01 g/L.h and residual sucrose of 42.84 g/L in 10.5 hours of fermentative process. It was studied the influence of cells recirculation during the fermentative process and the influence of initial concentration of ethanol and substrate in inoculum on the fed batch process with the aim of improve the productivity and reduce the residual sugar. From of this study it was obtained 92.75% of yield, 9.26 g/L.h of productivity, 2.9 g/L of residual sucrose concentration and the ethanol concentration produced was 83.37 g/L in 9 hours of fermentative process. The inhibition by the substrate and product model to the kinetics of alcoholic fermentation was proposed. The parameters of model were calculated by means of nonlinear adjust to the experimental results of growth of yeast, substrate consumption and formation of product to the batch reactor. The maximum specific speed of growth was 0.103 h-1 with KI and Ks equal to 109.86 and 30.24 g/L, respectively. With the experimental results of fed batch reactor and fed batch with recycle, it can be noted a good fit to the model proposed, resulting in a maximum specific velocity of growth of 0.080 h-1 to the process in fed batch without recycle and 0.182 h-1 to the fed batch process with recycle of fermentative media. The ethanol concentration in which the production of it is completely inhibited (P max) was 110 gethanol /L , approximately 13.92% (v/v). For the result of maximum concentration of product that inhibits fully the microorganisms growth (Pmax) was 12% (v/v), corresponding to 94.8 g/L of ethanol. The specific velocity of sedimentation (SVS) to the yeast C2/00 in pH 5 was 0.240 min-1 and the sedimentation rate of the test beaker was 0.444 cm/min. The alcoholic fermentation, using the flocculent yeast Saccharomyces cerevisiae in fed batch reactor with recycle of fermentative media provided higher productivity and yields when compared to the reported data by literature, in which used batch reactor or fed batch without recycle of fermentative media.

Coated or contaminated cuttings with drilling fluid are a residue of drilling. A more restrictive environmental legislation and the need to reduce the costs of drilling lead to optimization of solid-liquid separation and recycling drilling fluids. Shale shakers, hydrocyclones and centrifuges are examples of equipments used for processing drilling fluids. Nowadays, vertical filter centrifuges are used to adjust the cuttings into environmental laws. In this context, this work brings a study on the. Exploratory tests were carried out on domestic microwave oven and indicated the use of this technology as a promising alternative for cuttings decontamination. In this stage, residual n-paraffin contents lower than 2% were achieved. From these evidences, a microwave oven in bench scale was developed for drying contaminated cuttings. A set of aspects of the process were evaluated in this experimental unit. This drying methodology applied to contaminated cuttings was studied through several experimental tests and through a Central Composite Design of Experiments where the manipulated variables were drilling fluid concentration, mass and specific energy. The response variables were residual water and n-paraffin content, percentage of n-paraffin removed, mass flow and mass of n-paraffin removed per unit of energy. Initial tests showed that temperature does not affect the removal efficiency of the organic phase, but seems to affect the quality of the recovered material in the process. The power has negative influence on the cuttings decontamination and specific energy positively affects this process. From the Central Composite Design proposed, it is evident that microwave cuttings drying is favored by the increased mass and specific energy and harmed by the increase of the initial fluid concentration. The results show that cuttings drying carried out on microwave dryer reach levels of residual n-paraffin content lower than ones currently achieved by vertical filter centrifuge (about 4 %), reaching percentages below 1 %. Furthermore, the recovered fluid is free of solids and may be directly reused. Finally, this work has produced a set of important information to the oil industry and even has direct application in it.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior