Showing papers in "Brazilian Journal of Chemical Engineering in 2003"
TL;DR: In this article, the authors evaluated the performance of a chitosan support by physical adsorption, aiming at its application in hydrolytic and synthetic reactions, including the direct synthesis of n-butyl butyrate in organic solvent.
Abstract: The objective of this study was to evaluate the immobilization of lipase on a chitosan support by physical adsorption, aiming at its application in hydrolytic and synthetic reactions. Two types of chitosan (flakes and porous) were used for immobilizing lipase from a microbial source (Candida rugosa) and animal cells (porcine pancreas). The best results for recovery of total activity after immobilization were obtained for microbial lipase and porous chitosan beads. This set was selected for further immobilization studies, including full characterization of the immobilized derivative in aqueous and organic media. In aqueous medium, the operational and thermal stabilities of this preparation were quantified. In organic medium, the direct synthesis of n-butyl butyrate in organic solvent was chosen as a model reaction. The influence of several parameters, such as temperature, initial butyric acid concentration and amount of enzyme in the reaction system, was analyzed. Production of n-butyl butyrate was optimized and an ester yield response equation was obtained, making it possible to predict ester yields from known values of the three main factors. Use of this immobilized preparation was extended to the direct esterification of a large range of carboxylic acids (from C2 to C12) with a variety of alcohols (from C2 to C10).
100 citations
TL;DR: In this paper, the Aspergillus niger fungus was used for cadmium removal from oil field water in the oil industry and a technique for biomass recovery was developed with the objective of determining the capacity of the regenerated biomass to biosorb the metals in solution.
Abstract: Sorption experiments using the Aspergillus niger fungus for cadmium removal were carried out to study the factors influencing and optimizing the biosorption of this metal. The effects of pH, time, biomass concentration, and initial concentration of the heavy metal on the rate of metallic biosorption were examined. An experimental design was also used to determine the values of the under study variables that provided the greatest biosorption efficiency. A technique for biomass recovery was also developed with the objective of determining the capacity of the regenerated biomass to biosorb the metals in solution. This research proved that with a pH of 4.75, a biomass concentration of 0.7 g/L, and a heavy metal concentration varying between 5 and 10 mg/L a biosorption process of biosorption with Aspergillus niger could be successfully used for heavy metal removal from oil field water in the oil industry.
97 citations
TL;DR: In this article, the effect of geometrical relations on gas holdup and liquid velocity, and consequently on the gas-liquid mass transfer coefficient, was studied in a 6-liter air-lifted bioreactor with AD/AR = 0.63; AD, downcomer cross-sectional area, and AR, riser crosssectional area.
Abstract: In airlift reactors transport phenomena are achieved by pneumatic agitation and circulation occurs in a defined cyclic pattern through a loop. In the present work, the effect of geometrical relations on gas holdup and liquid velocity, and consequently on the gas-liquid mass transfer coefficient, was studied in a 6-liter airlift bioreactor with AD/AR = 0.63; AD, downcomer cross-sectional area, and AR, riser cross-sectional area. Measurements of the volumetric oxygen transfer coefficient (kLa) were taken in a water-air system using a modified sulfite oxidation method. Different conditions were examined by varying parameters such as superficial air velocity in the riser (UGR), bottom clearance (d1) and top clearance (d2). It was observed from the experimental results that d1 and d2 have a remarkable effect on kLa values. The effect is due to their influence on gas holdup and liquid velocity, consequently affecting kLa. Superficial air velocity in the riser (UGR) ranged from 0.0126 to 0.0440 m.s-1 and kLa varied between 40 to 250 h-1, whereas gas holdup (e) reached values up to 0.2. The volumetric oxygen transfer coefficient (kLa), gas holdup in the riser (eR) and downcomer (eD) and superficial liquid velocity in the riser (ULR) for all the geometrical relations were successfully correlated with dimensionless numbers, namely, the Sherwood number (Sh) and the Froude number (Fr) as well as with geometrical relations such as the bottom space ratio (B = d1/DD) and top space ratio (T = (d2 + DD)/DD).
54 citations
TL;DR: In this article, a bentonite clay from Mendoza, Argentina was activated with H2SO4 at 90oC for 2 and 3.5 hours and several cations were removed from the octahedral sheet (Mg, Al, and Fe) and the DTA-TGA curves of the solids obtained after treatment were modified.
Abstract: In this work, a bentonite clay from Mendoza, Argentina was activated with H2SO4 (4 and 8 N) at 90oC for 2 and 3.5 hours. Under these conditions several cations were removed from the octahedral sheet (Mg, Al, and Fe) and the DTA-TGA curves of the solids obtained after treatment were modified. Treatment time and acid concentration increased the degree of destruction of the bentonite structure. Activated samples were tested in order to verify their capacity to bleach soybean oil and were compared to a standard commercial bleaching clay. Treated samples are more efficient in bleaching than the standard.
51 citations
TL;DR: In this paper, the ion exchange of Na for Cr/K, Cr/Mg and Cr/Ca in Y and X zeolites was studied using breakthrough curves, and it was observed that Cr3+ ions were able to remove some competitive ions that had already been exchanged at the zeolitic sites, producing a sequential ion exchange.
Abstract: The ion exchange of Na for Cr/K, Cr/Mg and Cr/Ca in Y and X zeolites was studied using breakthrough curves. It was observed that Cr3+ ions were able to remove some competitive ions that had already been exchanged at the zeolitic sites, producing a sequential ion exchange. Some mass transfer parameters such as length of unused bed, overall mass transfer coefficient, operational ratio and dimensionless variance were studied. Chromium uptake was influenced much more by the competing ion in the NaX zeolite columns. The dimensionless variance indicated that Cr/K solution produced a greater axial dispersion than the Cr/Mg and Cr/Ca systems, probably due to some interaction between Cr3+ and K+ ions. The order of dynamic selectivity, provided by the cation uptake, was Cr3+ > Ca2+, Cr3+ > Mg2+ and Cr3+ > K+ for NaY zeolite and Ca2+ »Cr3+, Mg2+ > Cr3+ and Cr3+ > K+ for NaX zeolite. Due to the more favorable mass transfer parameters and higher affinity for Cr3+, it was concluded that NaY zeolite was more efficient at chromium uptake in competitive systems.
49 citations
TL;DR: In this article, the physical characteristics of cassava starch extruded using a single-screw extruder, varying acid concentration, feed moisture content and barrel temperature were evaluated using surface response methodology.
Abstract: Some physical characteristics of cassava starch extruded using a single-screw extruder, varying acid concentration, feed moisture content and barrel temperature were evaluated using surface response methodology. The combined effects of different concentrations of sulphuric acid and extruder parameters provided unique physical functionality to the extruded cassava starch. Product hardness and torque value was highly significant for three variables. The addition of sulphuric acid (0.06N) during extrusion cooking gave the highest values for expansion and softness of the extruded samples. The highest torque values (60-70 Nm) were for the samples extruded at the lowest moisture content, while the lowest torque values (23.0-26.0 Nm) were for the samples extruded at the highest values of feed moisture and barrel temperature.
41 citations
TL;DR: In this paper, the adsorption of two metal ions, Cr(III) and Cu(II), in single component and binary systems by Sargassum sp., a brown alga, was studied.
Abstract: The adsorption of two metal ions, Cr(III) and Cu(II), in single-component and binary systems by Sargassum sp., a brown alga, was studied. Equilibrium batch sorption studies were carried out at 30oC and pH 3.5. Kinetic tests were done for a binary mixture (chromium + copper) for a contact time of 72 hours to guarantee that equilibrium was reached. The monocomponent equilibrium data obtained were analyzed using the Langmuir and Freundlich isotherms. The binary equilibrium data obtained were described using four Langmuir-type and Freundlich isotherms. The F-test showed a statistically significant fit for all binary isotherm models. The parameters for isotherms of the Langmuir-type were used to determine the affinity of one metal for the biosorbent in the presence of another metal. The chromium ion showed a greater affinity for Sargassum sp. than the copper ion.
41 citations
TL;DR: In this paper, the rheological properties of these solutions were determined and the power-law model provided the best fit for experimental data, and the loss coefficients (kf) were calculated and correlated as a function of the generalized Reynolds number.
Abstract: Data on pressure drop were obtained in stainless steel, sanitary fittings and valves during laminar and turbulent flow of aqueous solutions of sucrose and xanthan gum, which were selected as model fluids. The rheological properties of these solutions were determined and the power-law model provided the best fit for experimental data. Friction losses were measured in fully and partially open butterfly and plug valves, bends and unions. Values of loss coefficients (kf) were calculated and correlated as a function of the generalized Reynolds number by the two-k method. The model adjustment was satisfactory and was better in the laminar flow range (0.976 < r2 < 0.999) than in the turbulent flow range (0.774 < r2 < 0.989). In order to test the adequacy of the results for predicting loss coefficients during flow of real fluids, experiments were conducted with coffee extract. Comparison between experimental and predicted loss coefficients showed very good agreement.
37 citations
TL;DR: In this paper, the ability of Thiobacillus thioparus to reduce chromium(VI) using another specie of ThIobacilli, T. Tioparus, was investigated in a fermentation vessel containing medium and sulphur as the sole energy source and maintained at 30oC and 400 rpm.
Abstract: The microbial reduction of chromium(VI) to chromium(III) has been one of the most widely studied forms of metal bioremediation. Recently, we have found that Thiobacillus ferrooxidans and Thiobacillus thiooxidans, growing on elemental sulphur, can indirectly promote chromium(VI) reduction by producing reducing agents such as sulphite and thiosulphate, which abiotically reduce chromium(VI). Those species of Thiobacillus are acidophilic bacteria which grow optimally at pH values lower than 4. However, most of those reducing agents are stabilised at higher pH values. Thus, the present paper reports on the ability to reduce chromium(VI) using another specie of Thiobacilli, Thiobacillus thioparus, which is able to grow at pH close to 7.0. T. thioparus cultures were carried out in a fermentation vessel containing medium and sulphur as the sole energy source and maintained at 30oC and 400 rpm. The pH was adjusted to 6.0, 7.0 or 8.0 and maintained with the automatic addition of KOH. Our results show high chromium (VI) reduction values (close to 100% at the end of bacterial growth) at the three pH values. The results of these experiments are very promising for development of a microbiological process to be used in the detoxification of chromium(VI)-polluted effluents.
28 citations
TL;DR: In this paper, a plate-plate nonthermal plasma reactor driven by AC high voltage was selected for the conversion of heavy oil into light hydrocarbon olefins, to be employed as gasoline components or to be added in small amounts for the catalytic reduction of nitrogen oxide compounds in the treatment of exhaust gas at power plants.
Abstract: During the last decade, nonthermal plasma technology was applied in many different fields, focusing attention on the destruction of harmful compounds in the air. This paper deals with nonthermal plasma reactors for the conversion of heavy oil into light hydrocarbon olefins, to be employed as gasoline components or to be added in small amounts for the catalytic reduction of nitrogen oxide compounds in the treatment of exhaust gas at power plants. For the process, the plate-plate nonthermal plasma reactor driven by AC high voltage was selected. The reactor was modeled as a function of parameter characteristics, using the methodology provided by the statistical experimental design. The parameters studied were gap distance between electrodes, carrier gas flow and applied power. Results indicate that the reactions occurring in the process of heavy oil conversion have an important selective behavior. The products obtained were C1-C4 hydrocarbons with ethylene as the main compound. Operating the parameters of the reactor within the established operative window of the system and close to the optimum conditions, efficiencies as high as 70 (ml/joule) were obtained. These values validate the process as an in-situ method to produce light olefins for the treatment of nitrogen oxides in the exhaust gas from diesel engines.
27 citations
TL;DR: According to the experiments with the bacterium C. perfringens, the reduction in number of microorganisms was higher than 98% after an irradiation time of 152 seconds, independent of color and turbidity, and efficiency of the coliphage inactivation reached approximately 100% between 89 and 104 HDT.
Abstract: This study presents results of the photocatalytic inactivation of two groups of microorganisms: spores of the anaerobic bacterium Clostridium perfringens and coliphage. A cylindrical reactor impregnated with titanium dioxide and irradiated with ultraviolet light (15 W) was used. Parameters such as color, turbidity, hydraulic detention time (HDT) and initial concentration of microorganisms were evaluated in relation to the efficiency of the inactivation process. According to the experiments with the bacterium C. perfringens, the reduction in number of microorganisms was higher than 98% after an irradiation time of 152 seconds, independent of color and turbidity. For solutions with low turbidities efficiency of the coliphage inactivation reached approximately 100% between 89 and 104 HDT, while this value was 98% for solutions with higher turbidities.
TL;DR: In this article, the process of desorption of hexavalent chromium, a toxic metal ion, from the marine algae Sargassum sp, following biosorption experiments 23 factorial design was studied.
Abstract: In this work the process of desorption of hexavalent chromium, a toxic metal ion, from the marine algae Sargassum sp, following biosorption experiments 23 factorial design was studied. A technique was applied to three eluents: HCl, H2SO4 and EDTA. Three factors of importance were evaluated: concentration of eluent, the ratio between mass of biosorbent and volume of eluent (S/L) and process time. A statistical analysis of the experimental results showed that the three variables evaluated are significant for all three eluents. The models for chromium desorption were validated, as the results agreed well with the observed values. Through use of the response surface methodology, a factorial design based optimization technique; it was possible to identify the most suitable eluent and the interval of values for the process variables that resulted in the most significant desorption of chromium, which is relevant information for work aiming at process optimization.
TL;DR: In this paper, a nonlinear model and multilayered neural networks were used to correlate the electric response of the biosensor and the concentration of lactose in wheat effluent.
Abstract: Whey is an abundant effluent in the production of cheese and casein. The biotechnological utilization of this economically important and nutritive source is limited mainly because of the presence of high percentages of lactose. This disaccharide has poor solubility, which can cause crystallization and insufficient sweetness in dairy food; additionally, part of the adult population suffers from associated lactose intolerance diseases. There are several methods to determine lactose such as spectrophotometry, polarimetry, infrared spectroscopy, titrimetry and chromatography. However these methods are tedious and time-consuming due to long sample preparation. These disadvantages stimulated the development of an enzymatic lactose biosensor. It employs two immobilized enzymes, b-galactosidase and glucose oxidase and the quantitative analysis of lactose is based on determination of oxygen consumption in the enzymatic reaction. The influence of temperature on the biosensor signal was experimentally studied. It was observed that a nonlinear relationship exists between the electric response of the biosensor - provided by CAFCA (Computer Assisted Flow Control & Analysis - ANASYSCON, Hannover) - and lactose concentration. In this work, attempts were made to correlate these variables using a simple nonlinear model and multilayered neural networks, with the latter providing the best modeling of the experimental data.
TL;DR: In this paper, the authors presented the optimization results of obtaining a high indium concentration solution and minimum iron poisoning by solvent extraction with D2EHPA solubilized in isoparaffin and exxsol.
Abstract: This experimental work presents the optimization results of obtaining a high indium concentration solution and minimum iron poisoning by solvent extraction with D2EHPA solubilized in isoparaffin and exxsol. The variables studied in the extraction step were D2EHPA concentration, acidity of the aqueous phase and time of contact between phases. Different hydrochloric and sulfuric acid concentrations were studied for the stripping step. The optimum experimental conditions resulted in a solution with 99% indium extraction and less than 4% iron. The construction of a McCabe-Thiele diagram indicated two theoretical countercurrent stages for indium extraction and at least six stages for indium stripping. Finally, the influence of associated metals found in typical sulfate leach liquors from zinc plants was studied. Under the experimental conditions for maximum indium extraction, 96% indium extraction was obtained, iron extraction was about 4% and no Ga, Cu and Zn were co-extracted.
TL;DR: In this paper, a finite difference implicit method was used to solve continuity and momentum equations applied to the entrance region of an axial, incompressible, isothermal, laminar and steady flow of a power-law fluid in a concentric annulus.
Abstract: Continuity and momentum equations applied to the entrance region of an axial, incompressible, isothermal, laminar and steady flow of a power-law fluid in a concentric annulus, were solved by a finite difference implicit method. The Newtonian case was solved used for validation of the method and then compared to reported results. For the non-Newtonian case a pseudoplastic power-law model was assumed and the equations were transformed to obtain a pseudo-Newtonian system which enabled its solution using the same technique as that used for the Newtonian case. Comparison of the results for entrance length and pressure drop with those available in the literature showed a qualitative similarity, but significant quantitative differences. This can be attributed to the differences in entrance geometries and the definition of asymptotic entrance length.
TL;DR: In this paper, the authors describe a novel system which has a great potential for use for extractions in biotechnological processes as it uses only polymers and can be operated at moderate temperatures and salt concentrations.
Abstract: This paper describes a novel system which has a great potential for use for extractions in biotechnological processes as it uses only polymers and can be operated at moderate temperatures and salt concentrations. The polymers used in this work are ethylene oxide-propylene oxide 10:90 (w/w) (EO10PO90) and ethylene oxide-propylene oxide 20:80 (w/w) (EO20PO80). The temperature required for thermoseparation decreases with increasing PO content of the copolymer and increasing buffer concentration.
TL;DR: In this article, the adsorption of human IgG onto GMA (a semirigid methacrylate-based chromatography matrix) and His-GMA adsorbents was studied by chromatography and batch equilibrium binding analysis.
Abstract: The adsorption of human IgG onto GMA (a semirigid methacrylate-based chromatography matrix) and His-GMA adsorbents was studied by chromatography and batch equilibrium binding analysis. IgG molecules adsorbed onto GMA gel by nonspecific hydrophobic interactions and the specificities were similar for both adsorbents. Adsorption data were analyzed using three isotherm models, namely the Langmuir, Freundlich and Langmuir-Freundlich models, and the adsorption parameters were computed. The experimental isotherms were best described by a combined Langmuir-Freundlich model, which indicated the presence of unequal binding sites on both adsorbents and/or positive cooperativity in the binding of the IgG molecules.
TL;DR: In this paper, a plug-flow reactor with an RVG 4000 graphite felt electrode was used for electrochemical reduction of hexavalent chromium Cr (VI) to Cr (III) ions in a dilute synthetic solution of K2Cr2O7 and Na2SO4 (0.05N).
Abstract: Even in at very low concentrations, heavy metals in industrial waste constitute environmental and health risks. The U.S. Department of Health and Human Services has recognized as chromium compounds and defined carcinogens the level acceptable in drinking water as being only 0.05 ppm. The objective of this work was the electrochemical reduction of hexavalent chromium Cr (VI) to Cr (III) ions in a dilute synthetic solution of K2Cr2O7 and Na2SO4 (0.05N). A plug-flow reactor with an RVG 4000 graphite felt (Le Carbone Lorraine, France) electrode was used for this work. Its morphological characteristics such as specific variables surface, porosity, average fibre diameter and permeability were determined. The influencing process selectivity such as initial concentration of Cr (VI), solution pH, current intensity and conversion yield are considered. The fractional conversion achieved in the plug-flow reactor in the present work, was about 90%.
TL;DR: In this article, the authors studied the kinetics of hydrogenation of xylose to xylitol on a sponge nickel catalyst (commonly referred to as Raney Ni catalyst) and of catalyst deactivation.
Abstract: The kinetics of hydrogenation of xylose to xylitol on a sponge nickel catalyst (commonly referred to as Raney Ni catalyst) and of catalyst deactivation were studied. Plausible explanations for the decrease in catalytic activity by means of surface studies, nitrogen adsorption and thermogravimetric analyses of the fresh and spent catalysts are presented. The kinetic parameters of the process were estimated by the use of a semi-competitive model, which allows full competition between the organic species and the hydrogen atoms for the adsorption sites on the catalyst surface (competitive case). In the model, a competitiveness factor (a) is introduced to take into account that even after complete coverage of the surface by the organic species, interstitial sites remain for the adsorption of the hydrogen atoms.
TL;DR: In this article, the mass transfer process in packed-bed reactors is modeled and taken into account dispersion in the main fluid phase, internal diffusion of the reactant in the pores of the catalyst, and surface reaction inside the catalyst.
Abstract: In this paper, the modeling of the mass transfer process in packed-bed reactors is presented and takes into account dispersion in the main fluid phase, internal diffusion of the reactant in the pores of the catalyst, and surface reaction inside the catalyst. The method of volume averaging is applied to obtain the governing equation for use on a small scale. The local mass equilibrium is assumed for obtaining the one-equation model for use on a large scale. The closure problems are developed subject to the length-scale constraints and the model of a spatially periodic porous medium. The expressions for effective diffusivity, hydrodynamic dispersion, total dispersion and the Darcy's law permeability tensors are presented. Solution of the set of final equations permits the variations of velocity and concentration of the chemical species along the packed-bed reactors to be obtained.
TL;DR: In this article, the design of vessels cooled by helical coils can be further improved by modifying the shape of the coil arrangement, mainly in the region between coils and wall of the vessel.
Abstract: Stirred Tank Reactors are extensively used in chemical industries. When they are used for highly exothermic reactions, jackets or coils are employed for heat removal. Internal coils can be either helical or axial and they considerably affect the flow inside the reactor because they impose an additional resistance to flow circulation. The aim of this work is to show that the design of vessels cooled by helical coils can be further improved. The design of these reactors follows very much the geometry proposed by Oldshue and Gretton (1954), and some minor modifications in the coil arrangements are likely to improve internal circulation inside these vessels mainly in the region between coils and wall of the vessel. Results show a gain in performance when small alterations are made specially in the shape of the coil arrangement.
TL;DR: In this article, the use of pyrolysis reaction as a process for deactivating paint sludge that generates a combustible gas phase, a solvent liquid phase and an inert solid phase was evaluated.
Abstract: The production of large quantities of paint sludge is a serious environmental problem. This work evaluates the use of pyrolysis reaction as a process for deactivating paint sludge that generates a combustible gas phase, a solvent liquid phase and an inert solid phase. These wastes were classified into three types: water-based solvent (latex resin) and solvents based on their resins (alkyd and polyurethane). An electrically heated stainless steel batch reactor with a capacity of 579 mL and a maximum pressure of 30 atm was used. Following the reactor, a flash separator, which was operated at atmospheric pressure, partially condensed and separated liquid and gas products. Pressure and temperature were monitored on-line by a control and data acquisition system, which adjusted the heating power supplied to the pyrolysis reactor. Reactions followed an experimental design with two factors (reaction time and temperature) and three levels (10, 50 and 90 minutes; 450, 550 and 650°C). The response variables were liquid and solid masses and net heat of combustion. The optimal operational range for the pyrolysis process was obtained for each response variable. A significant reduction in total mass of solid waste was obtained.
TL;DR: This work presents an age-structured population balance model (ASPBM) for a bioprocess in a continuous stirred-tank fermentor that relates the macroscopic properties and dynamic behavior of biomass to the operational parameters and microscopic properties of cells.
Abstract: This work presents an age-structured population balance model (ASPBM) for a bioprocess in a continuous stirred-tank fermentor. It relates the macroscopic properties and dynamic behavior of biomass to the operational parameters and microscopic properties of cells. Population dynamics is governed by two time- and age-dependent density functions for living and dead cells, accounting for the influence of substrate and dissolved oxygen concentrations on cell division, aging and death processes. The ASPBM described biomass and substrate oscillations in aerobic continuous cultures as experimentally observed. It is noteworthy that a small data set consisting of nonsegregated measurements was sufficient to adjust a complex segregated mathematical model.
TL;DR: In this article, a model of textile dyeing of a single cotton thread is presented, where the thread moves at a constant velocity within a homogeneous dye solution under steady state conditions.
Abstract: In this work the modelling of a process of textile dyeing of a single cotton thread is presented. This thread moves at a constant velocity within a homogeneous dye solution under steady state conditions. The method of volume averaging is applied to obtain the mass transfer equations related to the diffusion and adsorption process inside the cotton thread on a small scale. The one-equation model is developed for the fiber and dye solution system, assuming the principle of local mass equilibrium to be valid. On a large scale, the governing equations for the cotton thread, including the expression for effective diffusivity tensor, are obtained. Solution of these equations permits the dye concentration profile for inside the cotton thread and in the dyeing batch to be obtained and the best conditions for the dyeing process to be chosen.
TL;DR: In this article, the influence of operating temperature (500, 600, 700 and 800oC), superficial gas velocity (0.8, 1.0 and 1.2 m/s) and Ca/S molar ratio (1, 2 and 3) on SO2 removal efficiency for an inlet concentration of 1000 ppm was examined.
Abstract: In this work, SO2 was treated by reaction with dolomite limestone (24 µm) in a fluidized bed reactor composed of 500-590 µm sand particles. The influence of operating temperature (500, 600, 700 and 800oC), superficial gas velocity (0.8, 1.0 and 1.2 m/s) and Ca/S molar ratio (1, 2 and 3) on SO2 removal efficiency for an inlet concentration of 1000 ppm was examined. Removal of the pollutant was found to be dependent on temperature and Ca/S molar ratio, particularly at 700 and 800oC. A maximum removal of 76% was achieved at a velocity of 0.8 m/s, a temperature of 800°C and a Ca/S of 3. The main residence time of the powder particles was determined by integrating normalized gas concentration curves as a function of time; the values found ranged from 4.1 to 14.4 min. It was concluded that the reactor operated in bubbling fluidization under every operational condition.
TL;DR: In this paper, the performance of all the above-mentioned catalysts was comparable to that of the commercial one, except for in loss of mass, where the values was higher, which was attributed to the lower mechanical resistance of the support.
Abstract: Ir/Al2O3, Ir-Ru/Al2O3 and Ru/Al2O3, catalysts with total metal contents of 30% were prepared using the methods of incipient wetness and incipient coimpregnation wetness and were tested in a 2N microthruster. Their performances were then compared with that of the Shell 405 commercial catalyst (30% Ir/Al2O3). Tests were performed in continuous and pulsed regimes, where there are steep temperature and pressure gradients, from ambient values up to 650 oC and 14 bar. Performance stability, thrust produced, temperature and stagnation pressure in the chamber and losses of mass were analyzed and compared to the corresponding parameters in Shell 405 tests. It was observed that the performance of all the above-mentioned catalysts was comparable to that of the commercial one, except for in loss of mass, where the values was higher, which was attributed to the lower mechanical resistance of the support.
TL;DR: In this article, the aerodynamic properties of a movable block swirl burner were investigated using the RNG k-e isotropic turbulence model, which is characterized by the ability to adjust continuously and dynamically the intensity of the swirl by means of the simultaneous rotation of eight movable blocks inserted between eight fixed blocks.
Abstract: Computational fluid-dynamics techniques were employed to study the aerodynamics of a movable block swirl burner, developed by the International Flame Research Foundation, IFRF, which is characterized by the ability to adjust continuously and dynamically the intensity of the swirl by means of the simultaneous rotation of eight movable blocks, inserted between eight fixed blocks. Five three-dimensional grids were constructed for the burner, corresponding to five positions of the movable blocks. Both the k-e and RNG k-e isotropic turbulence models were applied. Only the latter described the existence of a central reverse flow along the annular duct. The employment of first-order and second-order interpolation schemes provided distinct results. The later provided results closer to the experimental tests. The swirl number decayed in the annular duct. The predicted swirl numbers for this movable block swirl burner were lower than the corresponding IFRF's experimental data, as was also observed by other researchers. This gave rise to the suspicion of some possible measurement error in the IFRF's experiments. On the other hand, the lack of agreement between the experimental data and the predictions regarding swirling flows could be attributed to the possible inadequate performance of the k-e model, as a consequence of its isotropic approximation. Still another possible explanation could be a phenomenon called bifurcation, in which one given swirl number can be associated with two distinct conditions of steady state flow. In addition, this complex flows requires a scrupulous development of the grids for the boundary condition and the employment of adequate interpolation schemes.
TL;DR: In this paper, the authors used polyfurfuryl alcohol polymer on activated carbon to separate O2/N2 mixtures and CO2 in a fixed bed at room temperature.
Abstract: The emission of CO2 from power plants that burn fossil fuels is the major cause of the accumulation of CO2 in the atmosphere. The separation of CO2 from CO2/air mixtures can play a key role in alleviating this problem. This separation can be carried out by using suitable adsorbents, such as carbon molecular sieves. In this work, a CMS was prepared by deposition of polyfurfuryl alcohol polymer on activated carbon. After deposition of the polymer, the material was carbonized at 800oC for 2 hours. This material was used to separate O2/N2 mixtures and CO2 in a fixed bed at room temperature. Experimental breakthrough curves obtained were fitted to theoretical models in order to establish the main mechanisms of mass transfer. The breakthrough curves showed that it is possible to separate O2, N2 and CO2. The shape of the breakthrough curves was not influenced by the total flow, indicating that the gas contact for the gas mixture was good. The experimental data were fitted to theoretical models and it was established that the main mechanism of mass transfer was intraparticle diffusion.
TL;DR: Two groups of isoforms of rhEPO, at a concentration of 300 µg/ml, were tested as putative inhibitors of the lectinic hemagglutination reaction in order to obtain affinity ligand(s) for hormone purification.
Abstract: Two groups of isoforms of rhEPO, at a concentration of 300 µg/ml, were tested as putative inhibitors of the lectinic hemagglutination reaction in order to obtain affinity ligand(s) for hormone purification: groups I (pI: 3.80; 3.89; 3.95; 4.07, 4.15 and 4.26) and groups II (pI: 4.15, 4.26; 4.38; 4.51; 4.72 and 4.93) Crude extracts from the vegetable materials Abrus precatorious (Abrin), Artocarpus incisa (Frutalin), Artocarpus integrifolia (Jacalin), Canavalia ensiformes (ConA), Canavalia brasiliensis (Conbr), Cratylia floribunda, Dioclea altissima (DAL), Dioclea grandiflora (DGL), Erythrina vellutina (EVL), Erythrina cristagalli, Lutaelburgia auriculata (lectin not fully characterized yet), Lycopersicum esculentum (LEA), Phaseolus vulgaris (PHA), Ricinus communis (Ricin) and Triticum vulgaris (WGA) were used. Only some of the galactose-specific lectins and the GlcNAc-specific lectins showed rapid full inhibition of the hemagglutination reaction for the less acidic isoforms and the total isoforms of rhEPO, respectively. On this basis, the selected lectins were purified by affinity chromatoghraphy and covalently coupled to cyanogen bromide activated Sepharose® (Amersham-Pharmacia). CHO.K1 cell culture supernatant containing rhEPO was loaded onto the lectin resins and the recoveries were calculated by using specific elutions.
TL;DR: Two receptor-binding sites for hGM-CSF are described and it is demonstrated that MAb M1B8, CC5B5 and M7E10 bind to domains which are responsible for the interaction of the cytokine with the GM- CSF receptor.
Abstract: Two receptor-binding sites for hGM-CSF are described. Competitive binding ELISA using four monoclonal antibodies (MAbs) showed different epitope recognitions. The antibody combining sites were mapped using sets of overlapping peptides and hexapeptide libraries prepared by the SPOT synthesis technique. We identified the conformationally dependent epitopes A18E21R23R24F119 and R23E21N17W13 bound by MAb CC5B5 and the nonlinear epitope P118F119W13E14 bound by MAb M1B8. The epitopes recognized by these two MAbs are very closely located on the native protein surface. The peptide L61YKQGKLRGSLTK72 was recognized by MAb M7E10 and the peptide A1PAR4, representing the N-terminal sequence of the protein, was bound by the nonneutralizing MAb CC1H7. Inhibition assays of the GM-CSF biological activity demonstrated that MAb M1B8, CC5B5 and M7E10 bind to domains which are responsible for the interaction of the cytokine with the GM-CSF receptor.