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Da Silva J.D.,Laboratory of Environmental and Energetic Technology
Chemical Engineering Transactions | Year: 2015

This paper presents an one-dimensional isothermal modelling for a three-phase trickle bed system (N2/H2ONaC6H11O7/ γ-Aℓ 2O3, 298K, 1.01 bar). The transient behavior was studied using a dynamic tracer method. The system has been operated with liquid and gas phases flowing downward with constant gas flow Qg = 2.86×10-6 m3 s-1 and the liquid phase flow Qℓ varying in the range from 4.95×10-6 m3 s-1 to 1.25×10-6 m3 s-1. The evolution of the NaC6H11O7 concentration in the aqueous liquid phase was measured at the exit of the reactor in response to the concentration increase at the reactor inlet. A mathematical model was developed and the solutions of the equations fitted to the measured tracer concentrations. The order of magnitude of the axial dispersion and liquid-solid mass transfer coefficients were estimated based on a numerical optimization procedure where the initial values of these coefficients, obtained by empirical correlations, were modified by comparing experimental and calculated tracer concentrations. The final optimized values of the coefficients were calculated by the minimization of a quadratic objective function. Two correlations were proposed to estimate the parameters values under the conditions employed. By comparing experimental and predicted tracer concentration step evolutions under different operating conditions the model was validated. Copyright © 2015, AIDIC Servizi S.r.l.


Silva J.D.,Laboratory of Environmental and Energetic Technology | Abreu C.A.M.,Federal University of Pernambuco
Brazilian Journal of Chemical Engineering | Year: 2012

The transient behavior in a three-phase trickle bed reactor system (N 2/H 2O-KCl/activated carbon, 298 K, 1.01 bar) was evaluated using a dynamic tracer method. The system operated with liquid and gas phases flowing downward with constant gas flow Q G = 2.50 × 10 -6 m 3 s -1 and the liquid phase flow (Q L) varying in the range from 4.25×10 -6 m 3 s -1 to 0.50×10 -6 m 3 s -1. The evolution of the KCl concentration in the aqueous liquid phase was measured at the outlet of the reactor in response to the concentration increase at reactor inlet. A mathematical model was formulated and the solutions of the equations fitted to the measured tracer concentrations. The order of magnitude of the axial dispersion, liquid-solid mass transfer and partial wetting efficiency coefficients were estimated based on a numerical optimization procedure where the initial values of these coefficients, obtained by empirical correlations, were modified by comparing experimental and calculated tracer concentrations. The final optimized values of the coefficients were calculated by the minimization of a quadratic objective function. Three correlations were proposed to estimate the parameters values under the conditions employed. By comparing experimental and predicted tracer concentration step evolutions under different operating conditions the model was validated.


Silva J.D.,Laboratory of Environmental and Energetic Technology | de Abreu C.A.M.,Federal University of Pernambuco
International Journal of Hydrogen Energy | Year: 2016

This paper presents a dynamics mathematical model to simulate the steam reforming of methane that take place in conventional fixed bed reactor (FBR) as well in fixed bed membrane reactor (FBMR) with steam added both with co-current mode. The model covers all aspects of main chemical kinetics, heat and mass phenomena in the membrane reactor with hydrogen permeation in radial direction across a Pd-based membrane. Firstly, a dynamics study was made for describing that temperatures of gaseous and solid phases reach to steady-state as well as molar flow rates. The effect several parameters including the axial position (z) divided by the reactor length Lz, reaction temperature and hydrogen partial pressure (PH2=Ppz) in permeation side were investigated. The conversion of methane is significantly enhanced by the partial removal of hydrogen from the reaction zone as a result of diffusion through the Pd-based membrane. Simulation results showed that a conversion from 99.85% could be achieved in a FBMR at reaction temperature of 600 °C relative to a conversion from 88.87% to 950 °C in a FBR. Besides, results showed that the yield of H2 reached to level from 1.548 (dynamics-state) and 1.626 (steady-state) in a FBMR at reaction temperature of 550 °C while the yield of H2 achieved to level from 1.261 (dynamics-state) and 1.445 (steady-state) in a FBR at reaction temperature of 725 °C. © 2016 Hydrogen Energy Publications LLC


Silva J.D.,Laboratory of Environmental and Energetic Technology
Chemical Engineering Transactions | Year: 2014

This paper presents an one-dimensional isothermal modelling for a CFBMR (H2 permeable). The work has been developed to simulate the SRM to produce H2. The dynamic simulation for molar flow rates of H2 was analyzed in the permeation side and shell side zones at different temperatures at the exit of the proposed system. The model has allowed the validation for the conversion of CH4 by comparing of optimized values. Additionally, the molar flow rates for chemical species (CH4, H2O, H2, CO and CO2) were analyzed along of the CFBMR (shell side) at t = 14 s, a comparison between permeation side and shell side for H2 and the molar flow rates of H2 in the permeation side and shell side zones at different temperatures.. Copyright © 2014, AIDIC Servizi S.r.l.


Silva F.R.,Laboratory of Environmental and Energetic Technology | Silva J.D.,Laboratory of Environmental and Energetic Technology
Chemical Engineering Transactions | Year: 2015

The biomass gasification is gaining attention of scientists and researchers worldwide to be an innovative and efficient method for producing clean energy. While consuming 'junk' organic, such as sugarcane bagasse or rice husk, the gas produced in the process is used for heat or electricity generation (or gas turbine engines), synthesis of liquid fuels, hydrogen production, chemical synthesis and manufacturing of fuel cells. However, a key challenge in the development and improvement of the biomass gasification process is cleaning the gas produced in order to ensure its quality and applicability. Among the main impurities found in the gasification gas, the tar is one of the worst, the presence of this kind of impurity can prejudice the performance of the process and also damage equipment. There are several methods for tar removal. Catalytic process is the most studied and the one that shows the best results. This paper presents an isothermal mathematical model that characterizes production and consumption of tar, modelled by toluene, reforming reaction using nickelbased catalyst. A computer code in FORTRAN 90 language was developed to perform the simulation, which described the concentrations of the main components (C7H8, O2, H2 and CO), as well as the reaction yield and influence of temperature on generation of products. Then the optimum conditions for carrying out the process were determined. Copyright © 2015, AIDIC Servizi S.r.l.

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