RCAAP Repository

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Drilling, one of the stages of oil and gas exploration, now has as targets regions of great complexity, with high depths. Coated or contaminated cuttings with drilling fluid are a result of drilling. The drilling fluids are water-based or non-aqueous based liquids. A more restrictive environmental legislation and the need to reduce the costs of drilling (exploration and production) lead to optimization of solid-liquid separation and recycling drilling fluids. Because oil industry has to submit itself to ever more stringent environmental laws it has applied a great deal of investments on sustainability research. In this context, this work provides a study of the characteristics of drilling cuttings and synthetic drilling muds at different steps of the solids control sistem, in order to know their behavior and its change over the process. The concentration of water, organic phase and solids in the mud were measured. The density and particle size of the cuttings were analyzed. The rheology and thixotropy of the mud were investigated. For this, samples of drilling mud were collected throughout the solids control system of five PETROBRAS onshore drilling rigs in Bahia (BA). The concentrations index are so important when investigating the efficiency of operation of the equipments in the solids control. The density of solids is very close to the density of clays. The results show that the rheology of drilling mud in the solids control process behaves as a non-Newtonian fluid, pseudoplastic, viscoplastic and thixotropic. The particle size of solids varies with operating conditions and always presents two average diameters by sample. The cutting dryer, a vertical centrifuge, plays a key role in the waste disposal due the stringent environmental laws, especially on offshore platforms. Thus, in order to research the optimization or restructuration of this step in the waste disposal, a study was carried on this equipment and the main points of its structure and operation were reported.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

A dynamic simplified model based on population balances is used to calculate the population density function of a particles coating process in a spouted bed with a draft tube, considering an independent size growing. The model considers the bed composed by two constant size domains of perfect mixture, where occurs coating and drying of particles, with circulation among them. The model is made dimensionless, so that the independent variable related to the coating mass is equal to the dimensionless residence time in the coating domain. This way, the distribution functions can be treated as residence time distributions, defined for each domain. The model is formed by hyperbolic partial differential equations, being analytically solved by Laplace transform and Moments Method. The model parameters that define the coating and drying domains, the porosity profile at the fountain and the particles circulation rate are obtained through geometric relationships and CFD simulations. The experimental frequency distribution curves related to the soybean seeds coating with inoculant and micronutrients, for different operational conditions and at the final operation time were compared with the simulated ones by the model, showing a good agreement. The values of moments, averages and standard deviations, analytically calculated, are presented for the several simulated cases, allowing the evaluation of the coating uniformity. The representation by normal distributions was not appropriated at the simulated conditions. The effects of the coating suspension flow rate and of the coating domain size over the distributions are analyzed, allowing the identification of operational conditions which make possible larger coating uniformity.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

In the fermentation process for ethanol production, the yeast Saccharomyces cerevisiae are recovered and recycled to a new stage of fermentation. This separation process is a major challenge, because the yeasts are small and low density. For this purpose the hydrocyclone emerges as an interesting alternative, because it uses the same principle of centrifugal separation, requires low maintenance and can be readily sterilized. This study aimed to optimize the separation process of yeast fermentation using hydrocyclones. To this end, was evaluated through experimental studies the influence of geometric and operational variables on the performance of hydrocyclones. A factorial experimental design (34) was applied and the results were used for the determination of empirical mathematical models that describe the capacity, total efficiency of separation, the flow ratio and reduced separation efficiency as a function of different geometric variables (feed inlet diameter, overflow diameter and angle of the hydrocyclone cone) and pressure drop. The geometry "optimum" founded was used in another factorial experimental design which aimed at evaluating the effect of concentration and pressure drop on the performance of the hydrocyclone. The diameters of the feed and overflow pipes studied were 2, 3 and 4 mm, while the angles of the hydrocyclone cone ranged from 6, 8 and 10º. The tests were conducted with suspensions of yeast in water with yeast concentrations from 0.5% to 5.5% by mass. All tests were performed at three different pressure drops (15, 23 and 31 psi). For yeast concentration of 1% was obtained total efficiencies of separation between 36.54 to 92.02%, reduced separation efficiencies from 4.67 to 55.59%, capacities from 0.1183 to 0.4579 m3/h and flow ratios, ranging from 31.74 to 84.30%. It also investigated the centrifugal forces generated within these devices ranging from 291g to 4153g. Analysis and discussion of the results show that the reduction of geometric variables with the increase in pressure drop and use of less concentrated suspensions led, in general, to an increase in total efficiency of separation. For the largest pressure drop conditions, the reduction of viability was checked and presented values below 6.76%. CFD techniques have also been applied in order to simulate the internal flow of a hydrocyclone.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Some factors may influence the sedimentation of a suspension of particles such as particle shape, density and size distribution. Particles with diameters larger settle more quickly, while the very fine particles tend to remain long in suspension. Considering that one way around the small diameter of the particles is the use of flocculating agents, this work has as one of its goals to study the effect of flocculant concentration and pH of the water on the sedimentation rate. In the experimental study was used as flocculant aluminum sulfate to aqueous suspensions of kaolin, with a polyelectrolyte as a coagulation aid. After testing different concentrations of flocculant can be observed that the settling velocities are larger for the concentration of flocculant equal to 5 mg / L suspension. As for pH, settling velocities are larger for the value 7. In a second step, experimental tests were performed in a continuous settler using suspensions with and without the use of aluminum sulfate (0.2 mg / L of suspension). The results revealed that, as expected, the concentration of solids in the underflow was greater for aqueous suspensions of kaolin with aluminum sulfate, even if not observed the formation of flakes. In these experiments, also raised the height of sediment produced in stationary operations. Experiments were carried out aiming at obtaining the constitutive equations for the pressure in solids and to sediment permeability and they perform simulations using two mathematical models, model Tiller and Chen (1988) model and Arouca (2007), in order to get numerically the final height of the sediment in steady state operations, in order to compare the experimental results. The results obtained in the resolution of the models showed that the model Tiller and Chen (1988) produced a deviation of 39.0% in the experimental result for suspensions without aluminum sulfate and 14.3% for suspensions with aluminum sulfate. Already the model Arouca (2007) resulted in values close to those obtained experimentally, with deviations of less than 3% for suspensions with and without aluminum sulfate.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

The importance of food service in the national economy grew at an average of 3% per annum over the past 10 years, which can be explained by the significant changes in the habits of the Brazilians, imposed by the modern world. There is a clear trend of increasing market demand for ready products for consumption, which is a result of changing population lifestyle. Many foods, before the frying process, are breaded with corn flour. This outer layer concentrates a higher oil absorption during the frying process. Some ingredients have been added to the coatings of breaded products to decrease the oil absorption. Among the different gums used as barriers to fat, the use of starch, which has the unique property of thermal gelation, was the target of this study. In this work, a method for treatment of corn flour was developed to reduce the oil absorption of steaks and nuggets, adding a solution of pregelatinized starch. The effect of the amount of gelatinized starch solution on the oil retention in fried corn flour was evaluated. Different amounts of a starch solution (30 %wt) were added to corn flour, keeping the humidity constant. The results showed that the addition of 3 g of gelatinized starch solution to 10 g of corn flour had the lowest oil absorption, with a reduction of about 21.5% in oil absorption when compared with the absorption of the sample without treatment. This condition contained enough solution to coat the flour particles, enhancing the formation of gelatinous film which acted as a resistance to entry of oil, promoting sealing the pores of the corn flour. Thus, this work contributes to the development of a less caloric fried product, enabling consumers to enjoy the unique flavor that the frying process provides to food. Furthermore, the implementation of starch-based coatings in the manufacturing process reduce the oil retention during the pre-frying, decreasing the amount of oil that should be returned to the process, and, consequently, process operational cost.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Companhia Energética de Minas Gerais