RCAAP Repository

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Urea is the most used nitrogen fertilizer in the world and little has been done in order to characterize their behavior in solution. In this work we experimentally determined the solubility of urea in water, ethanol, isopropanol, methanol and mixtures of these solvents, at temperatures from 274.9 to 336.5 K at constant atmospheric pressure. The gravimetric method was used to obtain experimental data. The experimental equipment used consisted of two solid-liquid equilibrium cells connected in series, joined by a latex hose and connected to a thermostatic bath. The experiment was conducted with two hours of stirring followed by two hours of decanting. Samples were withdrawn only from the supernatant liquid mixture by glass syringe and analyzed by gravimetric. Central planning compounds were performed with varying temperatures and concentration of solvents to determine the effect of each response in solubility. In experimental studies, it was also possible to correlate the experimental data estimating parameters of rational equations available in the literature. The results of the adjustments were compared with the data obtained in the experiments. The obtained results are in agreement with literature. This work also contribute sought in order to determine the solubility curves and parameters of thermodynamic equilibrium models Margules, Van Laar, Wilson and NRTL for urea solutions in water, ethanol , isopropanol, and methanol. With the thermodynamic adjustments, it can be concluded that the model proposed by Wilson was best represented the experimental data of solubility of urea, with low average percentage deviations and quadratic correlation coefficient close to one.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Brazil has a fairly diversified energy matrix, whose main sources consist of the use of the hydroelectric potential of its rivers and oil reserves, the latter being a non-renewable energy and very polluting. Even if Whimsy percentage when compared to the usual forms of energy in Brazil (hydroelectric and oil), the country have meteorological and agro-industrial conditions suitable to be a great producer, potential, solar energy and chemical energy coming from biomass. With regard to biomass, Brazil is one of the biggest producers of this form of energy, especially in the form of waste. If the purpose is not the direct combustion, biomass can be converted into fuels or even the noblest same in chemical precursors to other sectors of the economy. That said this thesis was to investigate the pyrolysis characteristics of mango seed and then evaluate the viability of pyrolysis process using techniques of solar concentration. Was used as the residual biomass core sleeve due to the highlight of the fruit on the world stage and also regionally where about 1300 t/year are discarded this waste in the region. The sleeve core is divided into two main parts: the kernel and the husk, being rich in the first and second bioactive compounds mainly composed of lignin, cellulose and hemicellulose. With regard to the kernel, there was a significant range of bioactive compounds (phenolic, flavonoids, ascorbic acid and citric acid), with emphasis on phenolic compounds with a content of about 3000 mg/100 g and is high compared to other fruits studied as acerola seed, soursop and guava. Concerning the integument, this presented a good indicator for the formation of liquid products, high volatile content and low ash content. With respect to thermogravimetric analysis, it was evaluated in two stages: the first related to the loss of water (drying) and the second referring to the pyrolysis reactions . For the first stage, after studies nonlinear model best described the drying step was Henderson, yielding an average activation energy of about 20 kJ/mol. As for the second stage, isoconversionais models showed activation energy for 157-175 kJ/mol. The Independent Reactions model (RPI) showed activation energy between 70 and 78 kJ/mol, 160 and 190 kJ/mol and 90 and 97 kJ/mol for lignin, cellulose and hemicellulose, respectively. There was also a tendency of decrease in activation energy with decreasing particle size both in the drying step as described in the second step isocorversionais models (Ozawa and Kinssinger). For the RPI model this trend was observed only for the major component of biomass (cellulose). Analytical pyrolysis has shown that the temperature at 500°C was the most suitable for production of liquid. In the temperature to 350°C, had become a low energy cost and the production of furfural which is of commercial interest. Concerning the study of the feasibility of solar pyrolysis by Response Surface technique was possible to predict simulations the best combination of the size of the solar collector (D), the system size to be heated (d) and solar radiation (G ) for significant temperature levels for industrial applications requiring this condition (for example, pyrolysis). Numerical simulations showed good agreement with the experimental data of solar heating, showing that with the optimization of operating conditions, particularly the effective area of the paraboloid, it would be possible to reach temperatures capable of providing the pyrolytic conversions.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The search for renewable energies and sustainable processes has made the biodiesel became an important fuel in the energetic matrix. In relation to the environment, biodiesel has important advantages compared to petroleum diesel it has greater biodegradability and low environmental impact. However, the increasing production and consumption of biodiesel has created a need to develop technologies for treating contaminated areas with this fuel. Bioremediation, a process that transforms through biological activity, contaminants in inert substances, is the form of treatment most applied for the remediation of contaminated soils with fuel. However, this method has limited application by factors such as high concentration of the contaminant or unfavorable environmental conditions for microorganisms. In such cases, it is reasonable to use a combination of two or more treatments to achieve the necessary efficiency to meet the environmental standards. A procedure that can be applied as a pretreatment before the bioremediation is the removal of contaminants from soil by physical treatment of washing. The objective of this study was to evaluate the removal of the pollutant load in the soil contaminated with biodiesel, combining techniques of physical and biological treatment. The physical treatment was performed by an agitation system of turbine Rushton, using the reuse water from a manufacturing industry as the basis of extraction solution. In the washing pretreatment, for the system using the surfactant Tween 80 (0.25% w/v), 60% solids concentration and 60 minutes of stirring, were obtained biodiesel removal percentages above 70%. In the case of not using the surfactant, the best result was shown by setting a 30% solids concentration and 35 minutes stirring. The removal percentage obtained in this case was near 65%. By separation of oil-water phases, it was able to recover about 43% of removed soil biodiesel and acid analysis, moisture and calorific value indicated that the recovered biodiesel has characteristics that allow its reuse. The treatment of the effluent from the washing step was done by biological process using the mixed culture C1 previously adapted into medium containing the contaminant. After 11 days of treatment, the concentration of biodiesel in the effluent approached zero and the value of the total organic carbon became constant with a decrease of up to 75.4%. The techniques used in bioremediation were biostimulation with temperature, humidity and nutrients (N and P) controls and bioaugmentation in two types of bioreactors: a) rotating bioreactor in laboratory scale (0.3 kg), b) bioreactor type rotary drum on a pilot scale (15 kg). The mixed culture inoculated soil was the same used in treatment of the liquid effluent. After 14 days of bioremediation, was obtain a cell concentration of approximately 1010 CFU/g soil for bacteria and fungi, showing that there was an adaptation of the microorganisms to soil. The concentration of the contaminant in the soil was determined by analysis of total petroleum hydrocarbons. The results indicated the percentage biodegradation above 90% in 35 days for treatments with rotating lab scale bioreactor and the same percentage in 70 days for the rotating pilot scale bioreactor.

The study of the filtration and thickening of particulate systems are used in many industrial processes that involve processes of solid-liquid separation, such as settling, filters, tanks, in the drilling of oil wells, among others. This paper aims to move forward in the empirical mechanisms involved in the processes of solid-liquid separation and to obtain constitutive equations that relate the pressure and permeability in porous solids from fluids Newtonian and non-Newtonian media, studying the process of sediment compaction in non-Newtonian fluids and constitutive equations to obtain high pressures in the solids. Aqueous solutions of xanthan gum concentration of 0.1% by weight were used in the experiments, in order to ensure a non-Newtonian solution. For the preparation of suspensions, was used as calcium carbonate particulate material in the separation process involved an initial concentration of 11 to 12% by volume. The settling tests were carried to term and the resulting pellets from each assay were evaluated by using the attenuation technique Gamma (TARG) which is a non-destructive technique based on measuring the attenuation of gamma rays. The concentrated sediment and remained stable between 30 and 48% by volume. Assays were performed at high pressures in a commercial HTHP filter type with a capacity of 400 ml, where suspension concentration used was 5% by volume. The results show that TARG was effective in determining sediment concentration distributions formed from Newtonian and non-Newtonian solutions, allowing for constitutive equations to obtain the solids pressure, permeability of the porous medium as well as to obtain the distribution of compaction of the sediment as a function of position and time, showing that sedimentation behavior of Newtonian and non-Newtonian fluid exhibit similar concentration distribution of solids settling time already quite distinct.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

The spouted bed has been used in several processes as drying, granulation, catalytic polymerization, residues treatment and materials coating. This application is due to the excellent fluid-particle contact and to the characteristics of the solids circulation. In spite of its extensive application, the spouted bed has some scale-up limitations, so it s necessary a better understanding about its fluid dynamic behavior. So, the knowledge of fluid and particles flows inside the spouted bed is of great interest for this equipment project, although the quantification of the solids motion is difficult to measure, even in regions of smaller density as in the spout. Another limitation presented by the conventional configuration of the spouted bed is the "short-circuit" of particles, in other words, the return of the particles that are in the spout-annulus interface for the spout before traveling the whole annulus area. This shortcircuit provokes a larger distribution of particles residence time, resulting in a heterogeneous product. An alternative to outline this limitation is to introduce a central tube (draft) that besides preventing this problem can also significantly alter the fluid dynamic of the bed, bringing other relative consequences to the fluid-particle contact. In the Computational Fluid Dynamic (CFD) modeling of two-phase gas-solid flows the drag force is one of the principal forces that acts in the particles, and has an important paper in the coupling among the two phases. Besides, in the spouted bed, the solids volume fraction can vary of practically zero to the maximum value of the packing limit, taking to a much more compound behavior of drag force than in conventional fluidized systems. So, it s necessary a special care in the choice of the drag model that best describes the multiphase flows studied. Among the drag models analyzed in the present work, the model of GIDASPOW et al. (1992) shows the best agreements with experimental data in the minimum spout condition. In this work, the fluid dynamics characteristic profiles of the spouted bed with and without draft tube were simulated by the CFD technique, through a Multiphase Granular Eulerian Model, using soybean seeds as particulate material. The characteristic curves of pressure drop in function of the air flow simulated, for the different configurations of the spouted bed (conventional and with tube draft located at different distances of the base), were compared with the experimental data presenting good agreement. Besides, were obtained simulated profiles of void in the spout area and of particle velocity in the annulus for air flows 20% higher than experimental minimum spout condition of each configuration (Q=1,2QJM exp). Finally was made an analysis of the influence of the distance of the draft to the base (Hd) on the air velocity simulated profiles in the spout areas and to annulus for a same feeding air flow.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Brazil is one of the greatest producers of fruits in the world which involves the generation of a large amount of agro-industrial residues whose potential still needs to be better studied. The yellow passion fruit (Passiflora edulis f. flavicarpa) is rich in minerals, vitamins and fibers and its production generates a large number of by-products as peels and seeds, which can reach 70% of the fruit weight. Within this reality, the methods of dehydration stand out as an alternative to remove moisture of this material, preventing the proliferation of microorganisms and creating opportunities for its reutilization. In this work, it was studied the impact of four techniques of dehydration in the passion fruit s residue: hot air, infrared, microwaves and freeze drying. In all was possible to obtain a material with satisfactory final moisture levels, highlighting the use of microwaves as the most efficient in terms of time. Dehydration by hot air was positively affected by velocity and temperature conditions, but the bioactive compounds had impact of temperature and time (80oC and 7 hours). The temperature of 95oC was the most efficient for the moisture removal and contends of bioactive compounds in the dehydration of infrared, but an overexposure to this radiation beyond the observed limits must be avoided. The use of microwaves show that is possible to obtain a material with good final quality and quickly, since intermediate levels of powers (480 W) are used to avoid over exposure. Freezer drying produced a final product with better visual appearance but its great operation times and the final content of bioactive compounds found wasn t better to other methods, in exception of pectin contents. Analyzing the bioactive compounds, phenolics and flavonoids were positively impacted by dehydration, reach values near and above of the residue in natura in all techniques. Citric acid showed deterioration in all conditions observed, indicating its sensibility to thermal processes as much as freeze drying. The ascorbic acid was strongly influenced by heat exposure an increased its levels, except in the freeze drying samples. Overall, the best dehydration methodology was the microwave technique, indicating a potential future use of this method in the use of passion fruit residues.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Instituto Federal de Ciencia e Tecnologia do Triangulo Mineiro