RCAAP Repository

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The cheese whey represents the most important reject of the industry of dairy products, mainly due to its expressive generated volume. The cheese whey is a problematic substrate under the environmental point of view, presenting high amounts of carbohydrates, proteins and fats, giving it a chemical demand of oxygen of approximately a hundred times larger than the one of the domestic waste. An alternative for its treatment would be the anaerobic fermentation, which reduces its pollutant impact, making possible even the recovery of the energy from the formed biogas. However, the low biodegradation rate of the fats in the cheese whey difficulties the anaerobic treatment, reducing the mass transfer, leading to biomass loss and to the collapse of the reactor. In this context, this work had as objective to evaluate the effect of the preliminary stage from the alkaline hydrolyses of the fats in the anaerobic biodegradation of the cheese whey. A complet experimental design, being considered as the independent variables factors as time and the concentration of NaOH indicated the best hydrolyses conditions as 0,1% of NaOH, reaction time at 15h in 35°C and 200 rpm. In the study of the biodegradability of the cheese whey was used as inoculum a sludge colleted in a anaerobic reactor from the effluents treatment of a food industry. The COD removal and the biogas production were monitored by time, in different concentrations of the cheese whey solution in the basal medium. The removal of COD and the biogas production were higher in the experiments with the previously hydrolyzed solutions, especially for larger concentrations of cheese whey. These results shows that the alkaline hydrolyzes may be an alternative in the biological treatment of effluents with high fat concentration.

The phophate is an indispensable nutrient to the vegetable and therefore animal development, in Brazil, the mineral wich contains phosphate is the apatite. The progressive content reduction of the ore deposits already discovered and being explored, allied to the growing demand for food, turns imperative the phosphate ore processing in many ways of the processings, mainly in that it says respect to the decrease of contaminants minerals. The flotation process is the main technology applied for the concentrate the apatite mineral, which passed for constants developments in the last decades being distinguished the flotation columns to the improvements of the concentrates gotten and economy in the project investments. Because an increase of the siliceous concentration in the phosphate rock of the Barreiro deposits (Araxá-MG), the objective of this work is developing the flotation of siliceous in column for the process of concentration the apatite. In this context, to quantify the effect of the operational variables as well as of the dosage of reagents in the grade of SiO2 in the product of deep and the recovery of P2O5 in the concentrate, a time that the flotation of siliceous represents in a stage of purification of the ore. In view of the gotten results, a global statistics analysis and a canonic analysis were made in order to optimize the operational conditions. The use of the collector Flotigam EDA showed itself suitable for siliceous flotation in column for the apatite concentration process. The best result carried through the tests realized in this work was a concentrate of flotation with recuperation of 6 wt. % P2O5, and product with grade of 8.12 wt % SiO2. The excellent operational conditions in the explored band was: air flow between 40 e 60 L/h, washed water flow of 0,40 L/min, 0,39 L/min of recycle flow, collector dosage of 450 g/t, depressor dosage of 550 g/t and collector conditioning time of 10 min for 340 g of ore. The results obtained from the benches column had shown the possibility of siliceous flotation in a previous stage of the apatite flotation.

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Distillation is the most applied unit operation in industrial plants due to its large application for ideal and non-ideal mixtures. Residue curve map is a tool used when one wants to test the feasibility of separation of a given mixture in a distillation column. This tool can be used as a preliminary estimate of probable products will be obtained after distillation of a mixture. Residue curve maps are usually calculated assuming equilibrium between liquid and vapor phases. However, it is known that the inclusion of mass transfer parameters can correct the assumption of equilibrium data presented closer to real distillation. An important property of residue curve maps is the presence of the distillation boundaries. A distillation boundary breaks the residue curve map in different regions of distillation, making it impossible to obtain any pure components of the mixture. In the 90 decade, few scientific studies have been published indicating the possibility of crossing distillation boundaries when non-equilibrium models were applied to calculate the residue curves. This verification contests the concept of distillation boundaries and should be analyzed in the further. The main purpose of this work was to develop software suitable for the construction of residue curve maps for ideal and non-ideal mixtures applying equilibrium models with and without correction for efficiency. Conventional activity models (NRTL, UNIQUAC and Wilson) were evaluated to describe the non-ideality liquid phase. Was considered the correlation of BARROS and WOLF (1997) for the calculation of efficiency in order to correct the assumption of the equilibrium phase. For this study, we evaluated the sensitivity of the residual curves when this correlation was employed, and also to examine the possibility of crossing the distillation boundaries. Using case study the ideal mixture of pentane-hexane-heptane and the mixture is non-ideal ethanol-water-acetone for validation of the developed software. The use of different activity models did not result in significantly different of residue curve map, showing that, for the case evaluated formed by acetone-chloroform-benzene three activity models behavior were quite similar and efficient displaying clearly the residue curve of the mixture evaluated. To study the sensitivity of residual curves as well as the possibility of crossing the distillation boundary five different cases were studied. The first case of study involved again the ideal mixture formed by pentane-hexane-heptane with relative deviation between the modeling of 3.83%. To a mixture of ethanol-water-acetone the relative deviation was approximately 3.67% were not observed the crossing of distillation boundary. For methanol-isopropanol-water were performed a comparison of data from this study with the literature pointing the model corrected by efficiency was closest to the real values of a distillation process. For the mixture formed by chloroform-acetone-benzene the relative deviation was 5.21% and was not found crossing the distillation boundary. Finally, we analyzed the mixture formed by acetone-chloroform-methanol where the relative deviation was 4.82%. Thus, it becomes apparent that the use of different models can create different regions of distillation due the distillation boundaries sensibility, so it is recommended to use non-equilibrium modeling or correlation for efficiency, because these models take into account parameters of mass transfer and energy generating more accurate data for the distillation process, particularly in regions near the distillation boundaries.

There is a growing interest in renewable and sustainable energy sources. Biomass is an important alternative source of energy, with several advantages. Huge amounts of biomass waste are generated worldwide, among them is the soybean hulls. Pyrolysis is an attractive alternative to use of this waste generating appreciable economic value products. Thermogravimetric analysis (TGA) is a widely used analytical technique to observe the thermal decomposition and kinetics of pyrolysis of materials. The main objectives of this work were to determine the physical and chemical properties of soybean hulls and conduct a study on the kinetics of pyrolysis for pure soybean hulls and with the addition of inorganic salts. Thermogravimetric analysis was performed at different heating rates (5, 10, 15, 20 and 25 °C/min) under an inert atmosphere of nitrogen for soybean hulls, to the main components present in biomass (cellulose, hemicellulose and lignin ) and for soybean hulls with addition of some salts (NaCl, ZnCl2 and MgCl2) at concentrations of 10, 20 and 30%. The curves of weight loss (TG) and derived of the weight loss curve (DTG) for the main components present in biomass indicate that cellulose degradation occurs in a temperature range between 240 ° C and 370°C, for hemicellulose occurs between 170 and 350 ° C and for lignin occurs between 250 and 900° C, approximately. TG and DTG curves for soybean hulls with addition salts showed that there was a reduction of the degradation temperature for the samples with added 20 and 30% of ZnCl2 and all samples with addition of MgCl2. For samples with addition of NaCl there was a increased of the degradation temperature The kinetics of decomposition of samples was represented by isoconversional models (model of Flynn-Wall- Ozawa - FWO and the Friedman model) and for independent parallel reaction models. The activation energy for soybean hulls ranged from 110 178 kJ/mol for the FWO model and from 131 212 kJ / mol for the Friedman model. For the soybean hulls with addition of salt, it was observed that only the samples with added 20 and 30% of MgCl2 presented a reduction of the activation energy. Among the results of the kinetic parameters determined by the independent parallel reaction models, cellulose presented the highest activation energy (201.1 204.0 kJ/mol), followed by the hemicellulose (109.5 112.5 kJ/mol) and lignin (57.3 61.3 kJ/mol).

Turbulence is a complex and chaotic phenomenon which is extremely sensitive to initial and boundary conditions. Due to the wide range of time and length scales generally present, it requires a large amount of computational resources to be completely captured. Approaches to turbulence models are used to simplify this situation. However, they may reduce the ow description quality. In this context, 2D and 3D numerical simulations of backward-facing step ows, in laminar and turbulent regimes, were experimented in the present work. These simulations were done with a computer code developed in FORTRAN, based on nite volumes with Centered Dierences Scheme and Backward Dierence Formula as spatial and temporal discretizations, respectively, using the Large- Eddy Simulation methodology. This method is based on the appliance of a spatial lter to the equations of motion. Scales larger than this lter are resolved, while the smallest ones are modeled. Three alternatives for subgrid modeling were tested (models proposed by Smagorinsky 1963, Germano et al. 1991 and no turbulence modeling) and the application of three dierent turbulent inlet conditions generators were analyzed. A better turbulent ow characterization was achieved when the turbulence dynamic model was used with turbulent inlet conditions generators, which presented time and space correlations.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The thermal food sterilization is based on the application of temperature conditions for established periods that perform a commercial sterilization of microorganisms, spores and enzymes that has as main goal the attainment of safe products for consumption during extended periods of time. This work addresses the sterilization processing of canned food for the action of heat and introduces a novel mathematical model capable of describing the heat transfer during the thermal treatment of canned vegetables, simulating a processing in a retort. The adopted retort works with vapor, it is horizontal with multiples stages during a batch sterilization cycle. With a modeling methodology, representative partial models of the thermal exchange in the grain/vegetable and can were developed, with posterior coupling of these models in a retort unit model. The considered dynamic models possess 1D level of detail for vegetables, 2D level of detail for the can. The used numerical methods for the solution of the coupled set of partial and ordinary differential equations were the orthogonal collocation technique coupled to the method of lines (MOL). The model was validated through a comparison of the results with values based on thermal penetration curve during peas sterilization reported in the literature. The results for this study show that the proposed model satisfactorily represents the process of canned food sterilization. It also indicates that the lethality could be defined as the monitoring function for online process control, leading to suitable and safe methods for safe production of a sterilized canned product.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

In the process of drilling, the rock fragments generated by the drill are taken from the well to the surface by the drilling fluid. The drilling fluid used in Brazil is made by synthetic oil, it presents several advantages over other types of drilling fluid. However, it has the disadvantage of having high toxicity and low biodegradability, requiring a separation system of drilled cuttings contaminated with this drilling fluid. Currently, the responsible equipment for reducing these levels to the permitted by law is working under extreme conditions and residual levels generated are very close to permitted by environmental legislation. For this reason, the technique of microwave drying has been studied for use in remediation of drilled cuttings and has shown very promising because it presents high efficiency and low operational problems when it is compared to conventional equipment. Therefore, the aim of this work are to investigate the influence of various operating parameters of a microwave dryer, analyze the efficiency of the dryer microwave suited for this job and to obtain operational conditions and information for operating a industrial microwave operating in continuous flow. So were tested influence of temperature, flow rate of inert, initial fluid content, reuse of drilled cuttings, rock type, fluid type and mechanical agitation in microwave drying; tests of drying kinetics and the mapping drying inside the microwave were made. The results showed no difference in drying with the influence of inert flow and the type of fluid, but there was influence of drying temperature, the initial salt content, initial fluid content and rock type. Drying with agitation can increased the removal efficiency in 17 % with 27 mm of bed thickness, rocks with slow heating improve the removal efficiency, drilled cuttings with similar physical aspects have similar removal efficiency. The heating of rocks in the microwave depends strongly of the oxides content in its composition. The temperature control of the bed should be the upper limit of the boiling range of the hydrocarbons present in the drilling fluid. The mapping study showed that there are drying gradients inside the microwave, besides showing the intrusive effect of metals in the material, effect of the edges of the recipes and the position of exhaust fan. The equipment showed to be as efficient as others listed in the literature, which can reduce the levels of n-paraffin to below 1 % by mass.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior