Scielo RSS <![CDATA[Brazilian Journal of Chemical Engineering]]> vol. 33 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[STABILITY IMPROVEMENT OF IMMOBILIZED ALKALINE PHOSPHATASE USING CHITOSAN NANOPARTICLES]]> Abstract Enzyme engineering via immobilization techniques is a suitable approach for improving enzyme function and stability and is superior to the other chemical or biological methods. In this study chitosan nanoparticles were synthesized using the Ionic Gelation method and were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Alkaline phosphatase was successfully immobilized on the chitosan nanoparticles in optimum conditions. Chitosan nanoparticles were used because of their special properties for enzyme immobilization. This study indicated that the immobilized enzyme has improved function at high temperature and during storage. Immobilization resulted in an increased range of optimum pH and temperature, and reusability of enzyme. Furthermore, the binding efficiency calculation indicated that the immobilized alkaline phosphatase conserved 71% of its native activity. Kinetic parameter studies indicated no significant difference between the immobilized and free enzymes. <![CDATA[NOVEL APPLICATION OF POROUS AND CELLULAR MATERIALS FOR COVALENT IMMOBILIZATION OF PEPSIN]]> Abstract Pepsin was immobilized via covalent bonds on different carriers: a silica gel carrier, acrylic beads, and a cellulose-based carrier - Granocel. All carriers were functionalized through the presence of -OH, -COOH, -NH2, or glycidyl groups on their surfaces. Three different cross-linkers were used for activation thereof. The results showed that Granocel activated by glutaraldehyde or carbodiimide and silica gel activated by glutaraldehyde were suitable carriers for the expression of enzyme activity. The optimum pH range for the native enzyme was 2.5-3.5 and this range was extended to the value 6.5 in the case of enzyme immobilized on the silica gel carrier and on Granocel. The optimum temperature values for the native and immobilized enzyme were in the range 37-40 °C and 40-50 °C, respectively. The activity of the immobilized pepsin at different values of pH and temperature was higher in comparison with the activity of the free enzyme. <![CDATA[NITROGEN SOURCES ON TPOMW VALORIZATION THROUGH SOLID STATE FERMENTATION PERFORMED BY <em>Yarrowia lipolytica</em>]]> Abstract This manuscript reports the valorization of two-phase olive mill waste (TPOMW) as raw material and carbon source for solid state fermentation using Yarrowia lipolytica as biocatalyst. Due to its chemical characteristics, a combination of different raw materials (TPOMW and wheat bran, WB) was evaluated and two distinct nitrogen sources were applied as supplementation for lipase production. A TPOMW/WB ratio of 1:1 and supplementation with ammonium sulfate was chosen as the best condition. The productivity in 24 h reached 7.8 U/g*h and, after four days of process, only decreased about 35%. Process pH ranged from 5.5 - 5.9, remaining in an acid range. Thus, the successful use of TPOMW, a watery solid by-product with high content of lipids, as raw material for Yarrowia lipolytica growth and lipase production provided an environmental friendly alternative to valorize such waste. <![CDATA[BATTERY RECYCLING: EFFECT OF CURRENT DENSITY ON MANGANESE RECOVERY THROUGH ELECTROLYTIC PROCESS]]> Abstract This work aims to verify the possibility of using depleted batteries as a source of manganese dioxide applying the electrolytic process. An electrolyte solution containing the following metal ions was used: Ca (270 mgL-1), Ni (3.000 mgL-1), Co (630 mgL-1), Mn (115.3 mgL-1), Ti (400 mgL-1) and Pb (20 mgL-1). The production of electrolytic manganese dioxide (EMD) was performed through electrolysis at 98 °C (± 2 °C) applying different current densities (ranging from 0.61 to 2.51 The materials obtained were analyzed through X-ray fluorescence spectrometry, X-ray diffraction, specific surface area (BET) and scanning electron microscopy (SEM). The best results regarding the current efficiency, purity grade and specific surface area were obtained with a current density ranging between 1.02 and 1.39 The allotropic εMnO2 variety was found in all tests. <![CDATA[ASSESSMENT OF OZONE AS A PRETREATMENT TO IMPROVE ANAEROBIC DIGESTION OF VINASSE]]> Abstract This paper presents an assessment of ozone oxidative effects on the biodegradability of sugar cane vinasse, aiming at increasing the methane yield by anaerobic digestion of this effluent. Furthermore, as a new approach, an economic balance of this process was made. Using a bench scale reactor, ozone was applied at 60, 120, 180, 240 mgO3.gCOD-1 doses in raw vinasse and at three initial pH values (4.8, 7 and 9). Applying 60 mgO3.gCOD-1, the biodegradability of vinasse was increased by 22.7% at the initial pH value of 4.8. The application of the two-way ANOVA test indicated a significant statistical interaction between the pH value and ozone. However, a preliminary energy assessment showed that the amount of electricity consumed in a full-scale ozonation plant would be almost 6 times higher than the energy recovered from the combustion of the additional methane produced (13.6%). These results indicate that ozonation of raw vinasse to increase the methane production in a subsequent anaerobic process is economically unfeasible. <![CDATA[NUMERICAL SIMULATION OF THE INCOMPRESSIBLE TURBULENT FLOW OF A BINARY MIXTURE OF AIR-WATER VAPOR: APPLICATIONS IN DRYING PROCESS]]> Abstract The present work deals with numerical simulation of the incompressible turbulent flow of a binary mixture air-water vapor inside channels. Calculations are performed using the RANS (Reynolds Average Navier-Stokes Equations) formulation in addition to the standart k-ε turbulence model. The mathematical model is discretized by a finite difference scheme, being adopted second order accurate expressions for both convection and diffusion terms. The mesh arrangement is collocated and artificial dissipation terms are added to control the odd-even decoupling problem. The numerical scheme is applied to solve the flow of a binary mixture of air-water vapor inside plane channels and sudden expansions. The validation performed indicates that the present method reproduces satisfactorily the literature data for both concentration profiles and Sherwood number. Furthermore, the parametric analysis performed indicates that the drying process (wall mass flux) is very sensitive to the flow parameters investigated, i.e., inlet flow velocity and channel expansion ratio. <![CDATA[NUMERICAL INVESTIGATION OF NON-NEWTONIAN DRILLING FLUIDS DURING THE OCCURRENCE OF A GAS KICK IN A PETROLEUM RESERVOIR]]> Abstract In this work, a simplified kick simulator is developed using the ANSYS® CFX software in order to better understand the phenomena called kick. This simulator is based on the modeling of a petroleum well where a gas kick occurs. Dynamic behavior of some variables like pressure, viscosity, density and volume fraction of the fluid is analyzed in the final stretch of the modeled well. In the simulations nine different drilling fluids are used of two rheological categories, Ostwald de Waele, also known as Power-Law, and Bingham fluids, and the results are compared among them. In these comparisons what fluid allows faster or slower invasion of gas is analyzed, as well as how the gas spreads into the drilling fluid. The pressure behavior during the kick process is also compared t. It is observed that, for both fluids, the pressure behavior is similar to a conventional leak in a pipe. <![CDATA[EFFECT OF CONTINUOUS CRYSTALLIZER PERFORMANCE ON STRUVITE CRYSTALS PRODUCED IN REACTION CRYSTALLIZATION FROM SOLUTIONS CONTAINING PHOSPHATE(V) AND ZINC(II) IONS]]> Abstract Continuous reaction crystallization of struvite from aqueous solutions containing phosphate(V) (1.0 mass %) and zinc(II) ions (from 0.1 to 2.0 mg kg-1) in a continuous DT MSMPR crystallizer was investigated. The influence of pH (9 - 11) and mean residence time (900 - 3600 s) on the product characteristics and its chemical composition was tested. Struvite crystals of mean size 22-41 µm were produced. An increase in Zn2+ concentration decreased the mean crystal size and homogeneity. An elevation of the pH also decreased the struvite crystal size. Augmenting the mean residence time influenced product quality advantageously. Coexistence of struvite and Zn(OH)2 in the product was confirmed analytically. <![CDATA[DOLOMITE DESULFURIZATION BEHAVIOR IN A BUBBLING FLUIDIZED BED PILOT PLANT FOR HIGH ASH COAL]]> Abstract Although fluidized bed in situ desulphurization from coal combustion has been widely studied, there are aspects that remain under investigation. Additionally, few publications address Brazilian coal desulphurization via fluidized beds. This study used a 250 kWth bubbling fluidized bed pilot plant to analyze different aspects of the dolomite desulphurization of two Brazilian coals. Superficial velocities of 0.38 and 0.46 m/s, flue gas recycling, Ca/S molar ratios and elutriation were assessed. Results confirmed the influence of the Ca/S molar ratio and superficial velocity - SO2 conversion up to 60.5% was achieved for one coal type, and 70.9% was achieved for the other type. A recycling ratio of 54.6% could increase SO2 conversion up to 86.1%. Elutriation and collection of ashes and Ca-containing products did not present the same behavior because a lower wt. % of CaO was collected by the gas controlled mechanism compared to the ash. <![CDATA[TUNING OF MODEL PREDICTIVE CONTROL WITH MULTI-OBJECTIVE OPTIMIZATION]]> Abstract Two multi-objective optimization based tuning methods for model predictive control are proposed. Both methods consider the minimization of the error between the closed-loop response and an output reference trajectory as tuning goals. The first approach is based on the ranking of the outputs according to their importance to the plant operation and it is solved by a lexicographic optimization algorithm. The second method solves a compromise optimization problem. The former is designed for systems in which the number of inputs is equal to the number of outputs, while the latter can also be applied to non-square systems. The main contribution is an automated tuning framework based on a straightforward goal definition. The proposed methods are tested on a finite horizon model predictive controller in closed-loop with a 3x3 subsystem of the Shell Heavy Oil Fractionator benchmark system. The simulation results show that the methods proposed here can be a useful tool to reduce the commissioning time of the controller. The methods are compared to an existing multi-objective optimization based tuning approach. The computational time required to run the proposed tuning algorithms is considerably reduced when compared to the existing approach and, moreover, it does not need an a posteriori decision to select a solution from a set of Pareto optimal solutions. <![CDATA[3D COMPOSITIONAL RESERVOIR SIMULATION IN CONJUNCTION WITH UNSTRUCTURED GRIDS]]> Abstract In the last decade, unstructured grids have been a very important step in the development of petroleum reservoir simulators. In fact, the so-called third generation simulators are based on Perpendicular Bisection (PEBI) unstructured grids. Nevertheless, the use of PEBI grids is not very general when full anisotropic reservoirs are modeled. Another possibility is the use of the Element based Finite Volume Method (EbFVM). This approach has been tested for several reservoir types and in principle has no limitation in application. In this paper, we implement this approach in an in-house simulator called UTCOMP using four element types: hexahedron, tetrahedron, prism, and pyramid. UTCOMP is a compositional, multiphase/multi-component simulator based on an Implicit Pressure Explicit Composition (IMPEC) approach designed to handle several hydrocarbon recovery processes. All properties, except permeability and porosity, are evaluated in each grid vertex. In this work, four case studies were selected to evaluate the implementation, two of them involving irregular geometries. Results are shown in terms of oil and gas rates and saturated gas field. <![CDATA[ADSORPTION PROCESS OF MOLECULARLY IMPRINTED SILICA FOR EXTRACTION OF LACTOSE FROM MILK]]> Abstract In Brazil, about 25-30% of the population has some degree of intolerance to lactose, a disorder associated with the inability of the body to digest lactose due to a disability or absence of the enzyme lactase. The goal of this study was to evaluate the performance of adsorption of lactose from fresh milk using a fixed bed column of molecularly imprinted polymer (MIP). The polymeric material was characterized using Scanning electron microscopy (SEM) analysis, thermal analysis (e.g., differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), and the method of Braunauer, Emmet and Teller (BET). The adsorption column dynamics and performance were studied by the breakthrough curves using a 24-1 fractional factorial design. The chemical and structural characterization of the pure matrix and imprinted polymers confirmed the molecularly imprinted polymer (MIP) imprinted with lactose. The highest capacity was 62.21 mgg-1, obtained at 307.1 K and a flow rate of 12.5 mL.min-1, with central point conditions, 320.1 K and 9 mL.min-1, with an average value of 50.9 mg.g-1. The results indicate that the molecularly imprinted polymer is efficient. <![CDATA[MATHEMATICAL MODELING OF BATCH ADSORPTION OF MANGANESE ONTO BONE CHAR]]> Abstract The present study investigated the dynamics of batch adsorption of manganese onto bone char by using two distinct mathematical formulations: the diffusion model and the shrinking core model. Both models assumed spherical particles and adequately described the transient behavior of metal adsorption under changing operating conditions. Comparatively, the diffusion model described the manganese adsorption better at distinct particle sizes even when small particles were used (dp ≤ 0.147 mm); the shrinking core model proved to be more reliable when larger adsorbent particles were used (dp &gt; 0.147 mm), and it described experimental data better at changing solid-liquid ratios. Manganese adsorption was favored when: (i) smaller adsorbing particles were used due to the increase in the contact area and easier access to reacting sites of the char; however, such an effect proved to be limited to dp ≤ 0.147 mm, and (ii) higher solid-liquid ratios were used due to the increase in the available reacting sites. External and intraparticle mass transfer dependences on particle size and solid-liquid ratio were also investigated, and results corroborated with prior investigations found in the literature. <![CDATA[EFFECT OF SORBENT PORE VOLUME ON THE CARBONATION REACTION OF LIME WITH CO<sub>2</sub>]]> Abstract The reaction of calcium oxide with carbon dioxide is one of the most important methods for the capture and concentration of greenhouse gas from the flue gases of industrial plants. In this work, the carbonation reaction of CaO obtained from various sources with CO2 was investigated by a thermogravimetric method. These sources include commercial lime or CaO, CaCO3, Ca(OH)2, CaC2O4.H2O, a synthesized nanoporous sorbent, limestone and acetic acid washed limestone. The effect of structural parameters of the sorbents on the reactivity and CO2 capture capacity were studied using pore size distribution data. Also, the changes in the solid texture during the carbonation reaction were investigated. It was found that there is a direct relation between the pore volume of the sorbents and their reactivity. It was found that sintering is one of the main reasons for decreased activity in the carbonation/calcination cycles. <![CDATA[THE COMPLETE MODELLING OF THE FILLING PROCESS OF HYDROGEN ONBOARD VEHICLE CYLINDERS]]> Abstract Complete modelling of the filling process occurring in a hydrogen-fueled vehicle storage cylinder is examined. A simultaneous modelling of the flow and heat transfer within the cylinder and cylinder wall has not been considered in previous studies. Rapid filling may result to an unexpected temperature rise and breaching of the safety standards. In the present study, initially a correlation was developed based on a numerical simulation for predicting the heat transfer rate between in-cylinder flow and the cylinder inside wall. Then, a thermodynamic model was developed for predicting transient variations of temperature and pressure inside the cylinder and wall temperature during the filling. The model was applied to a type III onboard storage cylinder filling process. The numerical results are compared with previously measured values and showed good agreement. The results also show that a great portion of heat dissipation from the in-cylinder flow is stored in the cylinder wall. It is also found that ambient temperature during the refueling process has considerable effects on filling behavior in general and in particular on the final in-cylinder temperature and filled mass. <![CDATA[EVALUATION OF BIOMASS AND COAL CO-GASIFICATION OF BRAZILIAN FEEDSTOCK USING A CHEMICAL EQUILIBRIUM MODEL]]> Abstract Coal and biomass are energy sources with great potential for use in Brazil. Coal-biomass co-gasification enables the combination of the positive characteristics of each fuel, besides leading to a cleaner use of coal. The present study evaluates the potential of co-gasification of binary coal-biomass blends using sources widely available in Brazil. This analysis employs computational simulations using a reliable thermodynamic equilibrium model. Favorable operational conditions at high temperatures are determined in order to obtain gaseous products suitable for energy cogeneration and chemical synthesis. This study shows that blends with biomass ratios of 5% and equivalence ratios ≤ 0.3 lead to high cold gas efficiencies. Suitable gaseous products for chemical synthesis were identified at biomass ratios ≤ 35% and moisture contents ≥ 40%. Formation of undesirable nitrogen and sulfur compounds was also analyzed. <![CDATA[ETHANOL DEHYDRATION IN PACKED DISTILLATION COLUMN USING GLYCEROL AS ENTRAINER: EXPERIMENTS AND HETP EVALUATION]]> Abstract The ethanol-water separation is very important because ethanol is widely applied in the chemical industry and its use as a fuel can reduce the pollution emitted to the air. However, anhydrous ethanol production using conventional distillation is impossible, at atmospheric pressure, due to the presence of an azeotrope. In the present work, experimental tests were carried out in order to evaluate the use of glycerol as an entrainer, in substitution of ethylene glycol in an extractive distillation. The use of glycerol is motivated by the biodiesel production units, due to the fact that it is the main byproduct and a new market is necessary to consume its overproduction. The experiments were carried out in a distillation column packed with Raschig rings, varying the glycerol/feed (ethanol and water) ratio, S/F, from 0.5 to 0.9. The samples were analyzed using a digital densimeter. The results showed that glycerol was effective to promote ethanol dehydration and the presence of an azeotrope was not observed using a solvent to feed ratio (S/F) equal to 0.9. Some empirical correlations were investigated to evaluate the HETP (Height Equivalent to a Theoretical Plate), and the results provided a useful tool for designing a packed bed column for ethanol-water separation.