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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 L z , reaction temperature and hydrogen partial pressure ( P H 2 = P pz ) 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 H 2 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 H 2 achieved to level from 1.261 (dynamics-state) and 1.445 (steady-state) in a FBR at reaction temperature of 725 °C. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an experimental and modelling study of the kinetics of hydrogen production through the methanol steam reforming (MSR) process using a membrane reactor with a self-made, porous PTFE-nafion membrane. The operating conditions were optimised through an analysis of the hydrogen recovery and the CO selectivity. The membrane reactor was modelled based on the hydrogen production rate, which was linked (chain) to the changes in the reactant concentrations. The analysis of the reaction kinetics provided an overview of the reaction process and the factors that affect the process. Moreover, the size of the membrane was estimated using the distribution of hydrogen concentrations along the reactor. The separation factors, particularly the separation of hydrogen from CO and CO2, are some of the factors that can influence the performance of a membrane reactor. [Copyright &y& Elsevier]

Abstract: The kinetic modeling of homogeneous decomposition of hydrogen iodide (HI) and HI/H2O vapors with the addition of diatomic iodine (I2) using the mechanism proposed in the companion work (part I) in the sulfur–iodine cycle was investigated in this paper. Thermodynamic results calculated by FactSage and the kinetic experiment verified the applicability of the mechanism. The effect of temperature, residence time, pressure, HI/H2O/I2 molar ratio, HI/I2 molar ratio, and sensitivity analysis on the HI conversion was observed in the modeling process. The addition of small amount of diatomic iodine greatly decreases the HI conversion, and the overall pressure could promote the HI decomposition rate in the kinetic process. Sensitivity analysis shows that hydrogen yield was most sensitive to reactions (4) HI + H = H2 + I, (1) HI + HI = H2 + I2, (5) HI + I = I2 + H, and (8) HI + OH = H2O + I. The existence of diatomic iodine increases the reverse reaction of (1) and (5). [Copyright &y& Elsevier]

Abstract: In this paper, the homogeneous decomposition of methane and ethane is modeled in a well stirred flow reactor. The kinetics of this process is represented by a reaction mechanism of 242 reactions and 75 species, based on a mechanism developed for hydrocarbon combustion and soot formation. It is shown that this model correctly predicts the hydrogen yield from pyrolysis in a temperature range of 600–1600°C, and pressure range of 0.1–10atm. Furthermore, the effect of temperature, pressure and residence time on the amount of hydrogen produced from the decomposition of methane, ethane, natural gas, and a mixture of methane and argon is studied. The model predicts that the use of ethane or its addition to methane increases the speed of hydrogen production at low temperatures and pressures. The addition of a noble gas like argon also increases the yield of hydrogen at high pressures. [Copyright &y& Elsevier]