Repositório RCAAP

The spouted bed has been increasingly used in coating of particles like pills and seeds, due to the excellent mobility of particles in the bed, to the biggest coating uniformity and the simultaneous coating and drying of the particles. The coating improves the physical and chemical properties of the particles. The spouted has advantages as no mechanical moving components, simultaneous coating and drying, possibility of working with a wide range of particles few agglomerates. Therefore, it requires care when used with fragile particles and coatings, which increase the elutriation. In this work experimental data obtained for the soybean's coating in a spouted bed with draft tube conducted by Duarte (2002) were subjected to a detailed statistical analysis to study the influence of the initial distribution of seeds and effect of the operating variables on the final coating distribution. Besides it, two dynamic balance population models were analyzed, both applied to functional characteristics areas of the conical cylindrical spouted bed with draft tube, to predict the population density function and to evaluate the effect of operational variables on the coating uniformity: the model of Liu and Litster (1993-b) applied to a single domain and the model of Wnukowski and Setterwall (1989) applied to two perfectly mixed regions where occur drying and coating of the particles. Both population balance models have been solved through the Coating1.0 code developed in Maple® and the obtained results were validated against the Duarte (2002) data. The single domain model is used as the basis for the parametric sensitivity and elasticity analysis of the spout air flow, atomization air flow, suspension flow and concentration of the suspension for each of the sixteen experiments through the DDASPK.F code. The analyses showed a great influence of the flow of spout air jet and the flow of suspension on the coating's uniformity. The growth takes place mainly at intermediate mass seeds according to a normal distribution, which is not affected by the initial distribution of uncoated seeds. The parametric sensitivity was more pronounced in seeds of intermediate mass, presenting its highest values for the spout flow air, while the elasticity was more pronounced for seeds of small and big masses.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico

In this work was studied the immobilization process β-galactosidase from Aspergillus oryzae by adsorption and cross-linking with glutaraldehyde, using as carrier ions-exchangers such as Duolite A-568, Duolite S-761, Dowex Marathon A, Dowex Marathon C and Amberlite 252 Na. Through innitial results, Duolite A-568 was choosed for the continuance of the work. The influence of the enzyme concentration and pH in the immobilization process was studied using a Central Composit Design (CCD) for a fixed time of 12 hours and temperature of 25°C. The optimal conditions for enzyme immobilization were pH 4,5 and galactosidase concentration 16 g/L. In the sequence, was studied the influence of glutaraldehyde concentration as cross-linking reagent and reaction time in the activity and in stability of the immobilized biocalyst, which were of 3,5 g/L and 1,50 h. The residual activity of the immobilized enzyme without cross-linking with glutaraldehyde after 30 uses was 51% as compared with the initial activity, while the enzyme immobilized with cross-linking was 90%. The immobilized enzyme with cross-linking presented higher pH stabilyt pH when compared to that without the referred treatment. The simultaneous influence of pH and temperature on the immobilized enzyme activity was studied through a PCC with the biocalyst produced in the optimized conditions of immobilization process. With the technique response surface it was possible to obtain the optimized pH of 4,1 and temperature of 34°C. The influence of the lactose concentration was studied in the range of 5 to 140 g/L and the Michaelis-Menten model was adjusted to the experimental results, with values of Vm and Km of 0,71 U and 12.07 g/L, respectively. In the study of the influence of the galactose as inhibitor of the lactose hydrolysis, the competitive inhibition model was adjusted to the experimental results and the values of Vm, Km and Ki were 0,77 U, 12,07 g/L and 4,94 g/L respectively.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Factors such as global climate change, environmental pollution and reduction of the availability of fossil energy resources make renewable energy a topic of growing importance, and in this context biomass has been considered the major current source of clean energy. Among the technologies of energy conversion from biomass, pyrolysis is a promising tool as it generates products with high energy content in solid (charcoal), liquid (bio-oil) and gas phases. These products have diverse application: energy production, refinery input and in the preparation or activated charcoal (solid product). In the context presented, this work investigates the reaction of pyrolysis of some residues of Brazilian agribusiness (cashew nut shells, sugarcane straw, chicken litter and sawdust) as a way to obtain products of higher energy level. For that, the samples were pyrolyzed in a stainless steel reactor externally heated. The effect of varying temperature and pressure on yield and quality of the products obtained from cashew nut shells was investigated. For the other biomass, the reaction was performed at different temperatures: 300 C, 400 ° C, 500 º C, 600 º C and 700 º C at atmospheric pressure. The products obtained were charcoal, bio-oil, aqueous phase and pyrolytic gas. The experimental results showed that the increase in pyrolysis temperature resulted in decreasing yield of solid product obtained. The yield of charcoal ranged between (19.83 - 27.61) % for cashew nut shells, (27.65 - 47.35) % for sugarcane straw, (37.13 - 53.38) % for chicken litter and (26.86 - 45.29) % for sawdust. The highest oil yield was obtained at 500 ° C for chicken litter (9.50 wt.%) and sawdust (10.00 wt.%). The yield of biooil from cashew nut shells reached its peak at 600 º C (37.83 wt.%). Sugarcane straw produced no measurable amount of oil in the reaction conditions studied.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Universidade Federal de Goiás - Goiânia

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The São Paulo Brasília Pipeline (OSBRA), owed by PETROBRAS, starts at the Planalto Refinery (REPLAN) and supplies gasoline, Diesel oil and liquefied petroleum gas (LPG) to the mid-west region of Brazil. The pipeline is 786 kilometers long with diameter of 20 inches in its first segment and 178 kilometers with 12 inches of diameter in the second. The fuels are pumped by seven unmanned pump stations and are delivered to five tank farms. Previously, these products were pumped into the pipeline in batches, those of Diesel or LPG located between gasoline batches. These sequences allowed the dilution of the transmix, which are mixtures generated between two products during the pipeline transportation, to the pure product tanks, keeping compliance to the former standards. The Diesel/gasoline transmix were mixed direct to pure product tanks of Diesel or gasoline. The LPG/gasoline transmix were submitted to flashing in a vessel before to be mixed into gasoline tanks or LPG spheres. The National Petroleum Agency (ANP) changed the Diesel and LPG standards, in 2001 and 2004 respectively. The properties which were altered are the flash point of the Diesel and the residues of the LPG. This new regulation turned the OSBRA installations unable to dilute the whole transmix volumes generated during pipeline transportation. Part of the transmix had to be sent back to the REPLAN, increasing the costs and making the LPG pipeline transportation unprofitable. To overcome this situation, a new product was developed the QINTER. The QINTER can be mixed in suitable rates either to Diesel or to gasoline keeping the compliance of these fuels to the new standards at the receiving tanks. The QINTER has been pumped into the pipeline between the batches of Diesel oil and gasoline since then. The standard solution to treat the mixture created between LPG and gasoline batches, which is a distillation tower, was studied, but it showed to be unprofitable and it would compel changes to the existing working schedule time, from Monday to Friday (6:00am to 10:00pm) to a 24:00h/day continuous work. In this thesis, there were studied three new configurations which would need lower capital investment and would not change the working schedule time. It was used the process simulator Petrox, developed by the Research Center of PETROBRAS, to carry out the necessary process simulations. In the first configuration it was studied the change of the actual treatment system operation, from batches to a steady state way, as well as it was made a search of the optimum pair of pressure and temperature operation of the existing system. In the second configuration it was included a new flash vessel in series with the existing flash vessel. In the third configuration it was added two flash vessels and two new heat exchanges to the existing system. The simulations which were carried out showed that in the three configurations studied the compliance with the new standards were achieved. Nevertheless, in the first configuration would be needed more time than the available in the current working schedule to treat the whole transmix generated in the pipeline transportation. The second and the third configurations provided the necessary capacity to treat the transmix. The advantage of the last one is the residue of its vapor stream to be within the standards. This feature turns the operational work easier, because it eliminates the necessity of controlling the proportion in that the vapor stream is mixed with LPG to keep compliance with the standards. Therefore, the desired target, to find technical and operational solution to treat the transmix volumes generated in the OSBRA transportation, was attained.

Oil by-products, such as lubricating oils, gasoline, diesel and their constituting organic compounds, pollutants hard to degrade, are constantly released into the hydrographic basins as a result of different industrial processes, accounting for serious pollution problems to sea life. An increasing concern at the environment has intensified the study of techniques for the removal of these polluting charges from liquid effluents. In this respect, adsorption has drawn much attention because it presents itself as an effective, money-saving, highly selective method at molecular level besides having low energy consumption. Besides the concern at the efficacy of the removal of pollutants, the final destination of the adsorbing solid once its life-span is over, must also be taken into consideration. Thus, the research for low-cost adsorbing materials likely to be reused for other purposes has been intensified, having their aggregate value increased by the adsorption process. Once sugar-cane bagasse is abundant throughout Brazil, it has a high surface area and is highly hydrophobic, its use as a bioadsorbent for organic contaminants has aroused the interest of the academic community. Thus, the aim of the present work is to assess the adsorption ability of sugar-cane bagasse for the removal of oil by-products contaminating liquid effluents, with the aim of treating those and carrying out the concomitant energetic enrichment of bagasse for its later use as fuel in boilers. This way, adsorption experiments in agitated reactor were carried out to investigate the factors which influence and optimize the bioadsorption of oil by-product contaminants on sugar-cane bagasse and to understand the mechanisms of this process. Therefore, the assessment of the kinetic curves and of the adsorption isotherms of gasoline and of n-heptane in aqueous solutions at room temperature was carried out. The results show the promising trait of bagasse as an adsorbent, being able to adsorb up to 99 % of gasoline and 90 % of n-heptane contained in solution containing about 5 % of these contaminants. Furthermore, the adsorption kinetics of gasoline is very quick (with equilibrium times lower than 5 minutes) and adsorption is favourable and takes place in multi layers. When describing experimental isotherms the models of Langmuir, Freundlich, Langmuir-Freundlich, Jovanovic-Freundlich, Dual-Site Langmuir Model (DSL) and Multispace Adsorption Model (MSAM) were assessed. The DSL and MSAM models are the ones which better describe the isotherms for gasoline adsorption, however, they are still poor to describe the isotherms of n-heptane adsorption.

Spouted bed has been studied intensively because of its potential of application in several processes. Identification and characterization of flow regimes in spouted bed based on visual observation have been reported in literature. However, the characterization of flow regimes based on visual observation is not either usual or possible in industrial equipments. Therefore, the aim this thesis is to design an experimental apparatus dotted a data acquisition system in order to identify the flow regime of the spouted bed. The experimental data obtained from the experimental apparatus were compared with data obtained from simulation studies by using a computational fluid dynamic technique (CFD). Soybean and cotton seeds were used in this study. The spouted bed was build in stainless steel with the following dimensions: H = 85 cm, Dc = 21 cm, Di = 3.5 cm e θ = 60°. The pressure drop fluctuations in the bed were acquired on line by using the LabVIEW® 7.1 software. A 100 Hz sampling frequency was used in all runs. Graphical analysis of the pressure fluctuations versus time showed to be not appropriate for identification of the flow regimes. On the other hand, the use of the fast Fourier transform technique (FFT) over the pressure drop signals yielded a power spectrum. Based on this power spectrum it was possible to propose an effective identification criterion. By using this criterion it was possible to identify clearly all flow regimes in the bed: fixed, transition and spouting. Simulation results used for comparison with experimental data were obtained by using the commercial package FLUENT® 6.1.18. The porosity profiles and the characteristic curve of the spouted bed were calculated by using an Eulerian multiphase model. The comparisons showed a very good agreement between experimental and simulation results.

Brazil holds second place in world production of dicalcium phosphate, which represents the main source of phosphorus for complementing the mineral salt that makes up the daily feed for cattle, hogs and fowls. Considering the fact that the increase in consumption of phosphates due to the increased annual consumption of meat by the world population, development of the technology necessary to guarantee quality and productivity has become imperative in order to supply this competitive market. The requirement for BUNGE Fertilizantes S.A. to accompany the world trend, reflected by client suggestions for sales of bulk quantities, originated the search for a new technology to produce microgranulated dicalcium phosphate. Due to characteristics adverse to forming the microgranulated dicalcium phosphate grain (particle size, monocalcium phosphate and residual acidity), it has become necessary to apply a final product classification process to guarantee compliance with the physical specifications of the material at the moment of expediting to clients. The purpose of this dissertation is to perform a study of the classification system used for fluidization, seeking scale-up information for construction of an industrial unit to be installed at the Cajati Facilities of BUNGE Fertilizantes. Fluidization is utilized commercially in a wide range of processes such as: catalytic operations, cooling, drying, recovery, etc, it utilizes the elutriation effect in wich the relatively small components are entrained by the gas flow for physical classification of materials. Within this concept an effort was made to quantify the effects of operational and dimensional variables of the fluidized bed system: porosity of the distribuition screen, residence time and freeboard angle. In accordance with the main experimental results, a statistical analyses was made by multiple regression, thus obtaining parameters related to the isolated variables and the interactions among them. It was observed that the operational and dimensional conditions that promote the best Separation and Recovery efficiencies for the system were those for which the screen porosity was 11 %, the residence time was 5,34 minutes and the freeboard angle was 33,62o. On the basis of the optimum data obtained from the fluidization pilot system, an industrial system was designed for the Cajati Facilities, having classification capacity of microgranulated dicalcium phosphate of 100 Tons/h. The resultant Separation end Recovery efficiencies of the industrial system demonstrate an excellent application of technology for FBC (dicalcium phosphate) classification and the model obtained from the pilot project precisely predicts the efficiencies for industrial systems. Thus, the mathematic model obtained from the pilot plant can be used as a reference for design and scale-up of microgranulated dicalcium phosphate industrial classification units, having characteristics similar to those studied in this dissertation.

Slaked lime is a suspension of hydrated lime in water that can contain up to 40% of solids in suspension. It is a cheap base with high alkaline content. It is used in a variety of industrial applications such as process of treatment of water and sewerage, treatment of waste, in the stages of sugar clarification, in gas cleaning systems, among several other processes. The quality of the suspensions of slaked lime depends on the quality of lime used and on a careful choice of the conditions during the hydration process. A high quality slaked lime is a product with a small quantity of insoluble residues, high specific surface area, high alkaline content, small particle size and low viscosity. Therefore, the objective of this work was study the best conditions of temperature, concentration (relation lime/water), lime particle size, and agitation to produce a superior slaked lime. A statistic analysis was performed using the results obtained in order to optimize the operational conditions of the hydration process. It was observed that the use of small lime particle size, a temperature around 74 °C and concentrations between 217 g/L e 228 g/L minimize the amount of insoluble residue. The use of the same particle size and temperature, with a concentration around 175 g/L contributes to increase of the specific surface area of calcium hydroxide. It was observed that the degree of agitation does not interfere in any slaked lime properties investigated. The majority of the slaked lime suspensions presented a pseudoplastic fluid behavior. It was verified that the samples with high reactivity and high surface area presented smaller agglomeration observed by images of scanning electron microscopy. Parametric optimization disclosed the conditions necessary to produce a slaked lime suspension of fine quality.

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Batch processes are usually systems for which defined raw materials quantities are combined in specific recipe during a designated time to produce intermediate or final high added value products and generating the smallest waste of raw material. Most of the batch processes with economic interest are inherently nonlinear, making the control task a challange. The iterative learning control is a methodology that involves the use of learning strategies in order to achieve the better reference trajectory tracking and disturbance rejection. Thus, the addressedmethodology uses important features for the control of industrial batch plants, as the disturbances rejection, the inclusion of restrictions on the control variables making control more realistic, added to the ability to track reference trajectories over the batch, among others. In this context, this work presents the iterative learning control methodology successfully applied to various plants with distinct features, ranging from minimum and nonminimal phase SISO and MIMO linear systems and nonlinear systems. Comparative studies about the proposed control quality against classical control methods were also performed to show the degree of increasing performance due to the iteractive learning strategy. The results of the use of iterative learning control strategies looked promising since they provide versatility and tuning with easy, making the controller intuitive. For LTI minimum phase processes, the learning was almost immediate. The iterative learning controller was able to compensate for nonminimum phase behavior resulting from delay or nonminimum phase zeros, leading to a perfect tracking of the reference trajectory. The use of the methodology for nonlinear plants control was evaluated for reaction systems in which are tried two different ways to get the learning matrix, such as FIR models and locally linearized models. The iterative learning control methodology brought improvement on the setpoint tracking in all studied cases.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais