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Brazilian Journal of Chemical Engineering, Volume: 26, Número: 4, Publicado: 2009
  • Recovery of p-TBC from a butadiene washing stream in a pilot plant Environmental Engineering

    Lóss, C. F.; Azevedo, E. B.; Dezotti, M.

    Resumo em Inglês:

    Results obtained in a pilot-scale unit designed for COD removal and p-TBC (p-tert-butylcatechol) recovery from a butadiene washing stream (pH 14, 200,000 mg COD L-1, highly toxic) at a petrochemical industry are presented. By adding H3PO4, phase separation is achieved and p-TBC is successfully recovered (88 g L-1 of washing stream). Information (time for phase separation and organic phase characterization) was gathered for designing a future industrial unit. The estimated heat generation rate was 990 kJ min-1 and 15 min were enough to promote phase separation for a liquid column of approximately 1.15 m.
  • Effects of ultrasound on the performance improvement of wastewater microfiltration through a porous ceramic filter Environmental Engineering

    Rocha, I. C. C.; Marques, J. J.; Silva, A. S.

    Resumo em Inglês:

    Filtration under an ultrasonic field is a technique that is gaining importance in the wastewater treatment research field, not only due to its ability as a cleaning mechanism, but also as a filtration intensifier. The main objective of this research was the study of the influence of ultrasonic waves on the filtration of theoilfield wastewater (known as produced water) in order to increase the operation performance and filter medium regenerative effectiveness. A 0.016 m² hollow cylindrical porous ceramic filter was submitted to the filtration of produced water by two mechanisms: conventional filtration under vacuum and filtration under theinfluence of ultrasonic waves. Experiments were carried out using synthetic produced water by analyzing the variables oil and grease content (O&G) and total suspended solids (TSS) for each filtration run. Backwashing of the filter medium with distilled water was also performed to evaluate the regeneration efficiency. During conventional filtration, permeate flux decreased gradually, becoming stable around 0.06 cm³.cm-2.s-1. Furthermore, in the filtration assisted by ultrasound, the permeate flux was around 0.15 cm³.cm-2.s-1. Therefore, ultrasonic waves provided an increase of about 150% in the permeate flux. Moreover, the sonication improved filter medium regeneration effectiveness, even under conditions of high TSS and O&G contents. Taking into consideration the very positive results associated with the application of ultrasonicwaves, this filtration technique is likely to become an important industrial process.
  • Recovery of tin and copper by recycling of printed circuit boards from obsolete computers Environmental Engineering

    Castro, L. A.; Martins, A. H.

    Resumo em Inglês:

    This paper presents the experimental results for the leaching of printed circuit boards (PCB) from obsolete computers for extracting and recovering tin and copper by means of leaching followed by precipitation. Printed circuit boards were dismantled, cut into small pieces, and fed into a cylinder mill. The powder obtained was leached by using the aqueous solutions 2.18N H2SO4, 2.18N H2SO4 + 3.0N HCl, 3.0N HCl, and 3.0N HCl + 1.0N HNO3. The lowest values for the percentage of metal extraction were obtained with 2.18N H2SO4 (2.7% for Sn and lower than 0.01% for Cu), while the 3.0N HCl + 1.0N HNO3 leach system exhibited an extraction of 98% for Sn and 93% for Cu. Precipitates were obtained at different pH values by neutralizing the leach liquors using NaOH. The 3.0N HCl + 1.0N HNO3 leach system presented the highest recovery values from the powder feed (84.1% for Sn and 31.9% for Cu), as well as from the leach liquor (85.8% for Sn and 34.3% for Cu).
  • Electroflocculation for textile wastewater treatment Environmental Engineering

    Cerqueira, A.; Russo, C.; Marques, M. R. C.

    Resumo em Inglês:

    This work reports on the viability of the electroflocculation (EF) process for chemical oxygen demand (COD), turbidity and color removal from a raw effluent originated from a particular textile industry related to hemp manufacture. Firstly, the following operational parameters were optimized: current density; initial pH; electrolysis time; material of the electrode (iron, aluminum or iron-aluminum); and interelectrode distance. Additionally, the effects of these parameters on specific electrical energy consumption (SEEC) were studied under the optimum conditions. The best removal efficiencies obtained were 93% for color, 99% for turbidity and up to 87% for COD using an aluminum electrode, the initial pH was 5, the cell time operation was 30 min and current density was 15 A/m². These results indicate that, under the studied operational conditions, electroflocculation of these efluents may constitute a viable alternative for COD, turbidity and color removal.
  • Sulfide toxicity kinetics of a uasb reactor Environmental Engineering

    Paula Jr., D. R.; Foresti, E.

    Resumo em Inglês:

    The effect of sulfide toxicity on kinetic parameters of anaerobic organic matter removal in a UASB (up-flow anaerobic sludge blanket) reactor is presented. Two lab-scale UASB reactors (10.5 L) were operated continuously during 12 months. The reactors were fed with synthetic wastes prepared daily using glucose, ammonium acetate, methanol and nutrient solution. One of the reactors also received increasing concentrations of sodium sulfide. For both reactors, the flow rate of 16 L.d-1 was held constant throughout the experiment, corresponding to a hydraulic retention time of 15.6 hours. The classic model for non-competitive sulfide inhibition was applied to the experimental data for determining the overall kinetic parameter of specific substrate utilization (q) and the sulfide inhibition coefficient (Ki). The application of the kinetic parameters determined allows prediction of methanogenesis inhibition and thus the adoption of operating parameters to minimize sulfide toxicity in UASB reactors.
  • Drop size in a liquid pulsed sieve-plate extraction column Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Usman, M. R.; Sattar, H.; Hussain, S. N.; Muhammad, H.; Asghar, A.; Afzal, W.

    Resumo em Inglês:

    The (Benzoic acid + kerosene + water) system was studied in a 5.0 cm diameter liquid pulsed liquid-liquid extraction column with a total number of 80 sieve plates. The effect of pulsation intensity, dispersed phase superficial velocity, and continuous phase superficial velocity on volume-surface mean diameter was studied. Generally, the mean drop diameter decreased more rapidly with the increase of pulsation intensities and superficial velocities at low pulsation intensities and superficial velocities. However, the effect was not found to be significant at higher pulsation intensities and higher superficial velocities. In the interpretation of the experimental results, the drop size was observed to be a function of the operating regimes (mixer-settler, dispersion, and emulsion) of the pulsed sieve-plate extraction column. The experimental mean drop diameters were compared to the most acceptable analytical drop size correlation developed by Kumar and Hartland (1986). The correlation proved to be in good agreement for the column operating in the dispersion regime.
  • Prediction of mass transfer coefficients in a pulsed packed extraction column using effective diffusivity Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Torab-Mostaedi, M.; Safdari, J.

    Resumo em Inglês:

    The volumetric overall mass transfer coefficients have been measured in a pulsed packed extraction column using diffusion model for two different liquid-liquid systems. The effects of operational variables such as pulsation intensity and dispersed and continuous phase flow rates on volumetric overall mass transfer coefficients have been investigated. Effective diffusivity is substituted for molecular diffusivity in the Gröber equation for prediction of dispersed phase overall mass transfer coefficients. The enhancement factor is determined experimentally and therefrom an empirical correlation is derived for prediction of effective diffusivity as a function of Reynolds number, Schmidt number and viscosity ratio. Good agreement between prediction and experiments was found for all operating conditions that were investigated.
  • Capillary holdup between vertical spheres Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Heris, S. Zeinali; Hamed Mosavian, M. T.; White, E. T.

    Resumo em Inglês:

    The maximum volume of liquid bridge left between two vertically mounted spherical particles has been theoretically determined and experimentally measured. As the gravitational effect has not been neglected in the theoretical model, the liquid interface profile is nonsymmetrical around the X-axis. Symmetry in the interface profile only occurs when either the particle size ratio or the gravitational force becomes zero. In this paper, some equations are derived as a function of the spheres' sizes, gap width, liquid density, surface tension and body force (gravity/centrifugal) to estimate the maximum amount of liquid that can be held between the two solid spheres. Then a comparison is made between the result based on these equations and several experimental results.
  • Hexene catalytic cracking over 30% sapo-34 catalyst for propylene maximization: influence of reaction conditions and reaction pathway exploration Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Nawaz, Z.; Tang, X.; Wei, F.

    Resumo em Inglês:

    Higher olefins are produced as a by product in a number of refinery processes and are one of the potential raw materials to produce propylene. In the present study, FCC model feed compound was considered to explore the olefin cracking features and options to enhance propylene using 30% SAPO-34 zeolite as catalyst in a micro-reactor. The superior selectivity of propylene (73 wt%) and higher total olefin selectivity was obtained over 30% SAPO-34 catalyst than over Y or ZSM-5 zeolite catalysts. The thermodynamical constraints were found to be relatively less serious in the case of 1-hexene conversion. Most of the 1-hexene follows a direct cracking pathway to give two propylene molecules, due to weak acid sites and better diffusion opportunities. The higher temperature and short residence time could also suppress the hydrogen transfer reactions. From OPE (olefins performance envelop) the products were classified as primary, secondary, or both. Iso-hexene (2-methyl-2-pentene) cracking was also analyzed in order to justify a shape selective effect of the SAPO-34 catalyst. A detailed integrated reaction network together with an associated mechanism was proposed and discussed in detail for their fundamental importance in understanding the olefin cracking processes over SAPO-34.
  • Effect of solid loading and aggregate size on the rheological behavior of PDMS/Calcium Carbonate suspensions Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Behzadfar, E.; Abdolrasouli, M. H.; Sharif, F.; Nazockdast, H.

    Resumo em Inglês:

    The purpose of this study is to examine the effect of solid loading and aggregate size on the rheological behavior of PDMS (polydimethylsiloxane)/CC (calcium carbonate) suspensions. Mixtures containing 10 to 40 vol% of CC were prepared; the effect of shear rate and particle content on aggregate size and rheological properties was studied. Rheological properties including viscosity, loss modulus, storage modulus and yield stress were measured using rotational and oscillatory rheometry. Casson's equation was found to satisfactorily model the samples' stress response as a function of shear rate for different solid content. While solid content did not have any effect on the aggregate size, shear rate did influence the aggregate median diameter. It was observed that suspensions with higher aggregate size had a higher viscosity. In general, for a given volume fraction, a small change in the aggregate size had a significant impact on the viscosity, particularly at low shear rates.
  • Lumping procedure for a kinetic model of catalytic naphtha reforming Kinetics And Catalysis; Reaction Enginneering; And Materials Science

    Arani, H. M.; Shirvani, M.; Safdarian, K.; Dorostkar, E.

    Resumo em Inglês:

    A lumping procedure is developed for obtaining kinetic and thermodynamic parameters of catalytic naphtha reforming. All kinetic and deactivation parameters are estimated from industrial data and thermodynamic parameters are calculated from derived mathematical expressions. The proposed model contains 17 lumps that include the C6 to C8+ hydrocarbon range and 15 reaction pathways. Hougen-Watson Langmuir-Hinshelwood type reaction rate expressions are used for kinetic simulation of catalytic reactions. The kinetic parameters are benchmarked with several sets of plant data and estimated by the SQP optimization method. After calculation of deactivation and kinetic parameters, plant data are compared with model predictions and only minor deviations between experimental and calculated data are generally observed.
  • In-line estimation of sulfur and nitrogen contents during hydrotreating of middle distillates Process System Engineering

    Pacheco, M. E.; Salim, V. M. M.; Pinto, J. C.

    Resumo em Inglês:

    The main objective of this work is analyzing whether it is possible to develop an empirical correlation for in-line estimation of the sulfur and nitrogen contents of the middle distillates Hydrotreating (HDT) products for control purposes. Correlations are based only on readily available in-line information of specific gravity variation between feedstock and products, without considering any piece of information about the kinetic behavior of the catalyst. Experimental data were obtained in pilot plants under operating conditions that are representative of refinery operations. Results indicate that the removal of nitrogen and sulfur compounds during middle distillates HDT can be monitored in-line in real time, based on the available measurements of specific gravity. This allows for development and implementation of advanced in-line procedures for monitoring and control of the HDT process in real time.
  • Thermodynamic simulation of biomass gas steam reforming for a solid oxide fuel cell (SOFC) system Thermodynamics And Separation Processes

    Sordi, A.; Silva, E. P. da; M. Neto, A. J.; Lopes, D. G.; Pinto, C. S.; Araújo, P. D.

    Resumo em Inglês:

    This paper presents a methodology to simulate a small-scale fuel cell system for power generation using biomass gas as fuel. The methodology encompasses the thermodynamic and electrochemical aspects of a solid oxide fuel cell (SOFC), as well as solves the problem of chemical equilibrium in complex systems. In this case the complex system is the internal reforming of biomass gas to produce hydrogen. The fuel cell input variables are: operational voltage, cell power output, composition of the biomass gas reforming, thermodynamic efficiency, electrochemical efficiency, practical efficiency, the First and Second law efficiencies for the whole system. The chemical compositions, molar flows and temperatures are presented to each point of the system as well as the exergetic efficiency. For a molar water/carbon ratio of 2, the thermodynamic simulation of the biomass gas reforming indicates the maximum hydrogen production at a temperature of 1070 K, which can vary as a function of the biomass gas composition. The comparison with the efficiency of simple gas turbine cycle and regenerative gas turbine cycle shows the superiority of SOFC for the considered electrical power range.
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