Jornandes Dias da Silva

This paper presents a one-dimensional isothermal model of a hydrogenpermeable circulating fluidized bed membrane reactor (CFBMR) for hydrogen production via steam reforming of methane (SRM). Dynamic simulations were conducted to evaluate hydrogen molar flow rates on the permeation and shell sides at different outlet temperatures. Model validation was performed by comparing the predicted methane conversion with optimized reference data. Additionally, axial profiles of the molar flow rates of CH₄, H₂O, H₂, CO, and CO₂ along the shell side were analyzed at t=14 s. The effects of temperature and reactor zone on hydrogen production were also assessed.

The heat and mass transfer processes of the steam reforming of toluene (SRT) in a solar thermochemical reactor (STR) have been numerically studied. The mathematical modeling is focused on the heat and mass transfer phenomena integrated to thermochemical kinetic model in STR. The action of several parameters including the superficial velocity (Vsg), residence time (tr) and operating temperature (Top.) were evaluated. As results, when the Vsg is increased, the temperature profiles of the gas phase are remarkably decreasing. The reactant mole concentration (C7H9 and H2O) distributions decrease sharply along the STR length. On the other hand, product mole concentration distributions increase remarkably along the STR length. According to simulated results, the overall conversions of C7H9 reach the maximum value of 94.58% at the operating time of 3.0 hours. The dimensionless flow rate (DFR) of (H2 and CO) products is remarkably increased with the operating temperature and the maximum values of H2 and CO can be achieved 1.6521, 0.2548 at 1250K.

Sugarcane bagasse was processed via aqueous acid hydrolysis to produce xylose and glucose solutions from hemicellulose and cellulose, respectively. These monosaccharides were then hydrogenated using a nickel catalyst to yield polyols. The hydrolysis resulted in yields of 21.67% (xylose) and 14.03% (glucose), based on the dry weight of lignin-free bagasse. The hydrogenation process produced xylitol (78.62% yield) and sorbitol (39.64% yield). Kinetic analysis revealed activation energies of 12.92 kJ/mol for hemicellulose hydrolysis, 29.88 kJ/mol for cellulose hydrolysis, 42.74 kJ/mol for xylose hydrogenation, and 49.08 kJ/mol for glucose hydrogenation.

Pd-based membrane reformers have been substantially studied in the past as a promising reformer to produce high-purity H₂ from thermochemical conversion of methane (CH₄). A variety of research approaches have been taken in the experimental and theoretical fields. The main objective of this work is a theoretical modelling to describe the process variables of the Steam Reforming of Methane (SRM) method on the Pd-based membrane reformer. These process variables describe the specific aims of each equation of the mathematical model characterizing the performance from reformer. The simulated results of the mole fractions of components (MFCs) at the outlet of the Fixed Bed Reformer (FBR) and Packed-Bed Membrane Reformer (PBMR) have been validated. When the H₂O/CH₄ ratio decreases in PBMR, the Endothermic Reaction Temperature (ERT) is notably increased (998.32 K) at the outlet of the PBMR’s reaction zone. On the other hand, when the H₂O/CH₄ ratio increases in PBMR, the ERT is remarkably decreased (827.83 K) at the outlet of the PBMR’s reaction zone. An increase of the spatial velocity (S_sp) indicates a reduction in the residence time of reactant molecules inside PBMR and, thus, a decrease of the ERT and conversion of CH₄. In contrast, a reduction of the S_sp shows an increase of the residence time of reactant molecules within PBMR and, therefore, a rise of the ERT and conversion of CH₄. An increase of the H₂O/CH₄ ratio raises the conversion rate (CR) of CH₄ due to the reduction of the coke content on the catalyst particles. Conversely, a reduction of the H₂O/CH₄ ratio decreases the CR of CH₄ owing to the increase of the coke content on the catalyst particles. Contrary to the CR of CH₄, the consumption-based yield (CBY) of H₂ sharply decreases with the increase of the H₂O/CH₄ ratio. An increase of the ERT raises the thermochemical energy storage efficiency (η_tese) from 68.96% (ERT = 1023 K), 63.21% (ERT = 973 K), and 48.12% (ERT = 723 K). The chemical energy, sensible heat, and heat loss reached values of 384.96 W, 151.68 W, and 249.73 W at 973 K. The selectivity of H₂ presents higher amounts in the gaseous mixture that varies from 60.98 to 73.18 while CH₄ showed lower values ranging from 1.41 to 2.06. Our work is limited to the SRM method. In terms of future uses of this method, new works can be undertaken using novel materials (open-cell foams) and the physical-mathematical model (two-dimensional and three-dimensional) to evaluate the concentration polarization inside membrane reactors.

The transient behavior in a three-phase trickle bed reactor system (N2/H2O-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 x 10-6 m³ s-1 and the liquid phase flow (Q L) varying in the range from 4.25x10-6 m³ s-1 to 0.50x10-6 m³ 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.