Ion transport membrane reactors for oxy-combustion–Part II: Analysis and comparison of alternatives

Ben‐Mansour

et al. 2016

Summary The present work investigates the performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ ion transport membrane for separation of oxygen and its simultaneous reaction with gaseous fuels. A 2‐D axisymmetric model is considered to investigate the flow and combustion characteristics of methane in a button cell experimental model. A model that includes surface kinetics on the permeate and feed sides together with the bulk diffusion for BSCF membrane is developed and validated well against the experimental results. The effects of reaction on oxygen permeation and combustion characteristics are presented. Firstly, the nonreactive cases are investigated for oxygen permeation only. Later, the effects of increasing CH4% on the reactivity are explored. Finally, the effect of an increase in the operating temperatures on permeation of oxygen and reactivity are presented and quantified. It is found that the permeation of oxygen increases as the CH4% is increased in the sweep side because of an increase in the volume flow rates. The reactivity increased with an increase in the CH4%, however, beyond CH4 = 2% in the sweep side the amount of unburned CH4 also increased. It is also indicated that raising the operating temperatures results in shortened flame zones with more concentration in the vicinity of the ITM. Copyright © 2016 John Wiley & Sons, Ltd.

Section: Reactive Casessupporting

confidence: 91%

Investigation of oxygen permeation through disc-shaped BSCF ion transport membrane under reactive conditions

Ahmed

Ben‐Mansour

et al. 2016

“…As the percentage of CH 4 in the sweep gas changes from 100% to 10%, the counter-current regime results in permeation rates that are 6.62-12.75% higher than those of the co-current regime. Manccini and Mitsos [39,40] have developed a block box model for modeling an ITM reactor and obtained similar results, which showed that the counter-current regime is more viable than the co-current.…”

Section: Resultsmentioning

confidence: 84%

Modeling of ion transport reactor for oxy-fuel combustion

Farooqui

Badr

et al. 2012

SUMMARY This paper aims at investigating the performance of a cylindrical ion transport reactor designed for oxy‐fuel combustion. The cylindrical reactor walls are made of dense, nonporous, mixed‐conducting ceramic membranes that only allow oxygen permeation from the outside air into the combustion chamber. The sweep gas (CO2 and CH4) enters the reactor from one side and mixes with the oxygen permeate, and the products are discharged from the other side. The process of oxygen permeation through the reactor walls is influenced by the flow condition and composition of air at the feed side (inlet air side) and the gas mixture at the permeate side (sweep gas side). The modeling of the flow process is based on the numerical solution of the conservation equations of mass, momentum, energy, and species in the axisymmetric flow domain. The membrane is modeled as a selective layer in which the oxygen permeation depends on the prevailing temperatures as well as the oxygen partial pressure at both sides of the membrane. The CFD calculations were carried out using fluent 12.1 (ANSYS, Inc., Canonsburg, PA, USA), whereas the mass transfer of oxygen through the membrane is modeled by a set of user defined functions. The model results were validated against previous experimental data, and the comparison showed a good agreement. The study focused on the effect of oxygen partial pressure and temperature on the resulting combustion zones inside the reactor for the two cases of co‐current and counter‐current flow regimes. The results indicated that the oxygen to fuel mass ratio increases as the percentage of CO2 increases in the inflow sweep gas for both co‐current and counter‐current flows. The obtained sweep mixture ratio (CO2/CH4) of 24 is found within the stoichiometric limit over most of the reactor length in the co‐current configuration, whereas the sweep mixture ratio of 15.67 is found in the counter‐current configuration owing to the high O2 permeation. Copyright © 2012 John Wiley & Sons, Ltd.

“…For chemical reaction modelling, the generalized single finite‐rate chemical kinetics model used is described as .

R_{C H_{4}} = - k {[C H_{4}]}^{n_{C H_{4}}} {[O_{2}]}^{n_{C O_{2}}}

…”

Section: Mathematical Modelingmentioning

confidence: 99%

Investigation of performance of fire-tube boilers integrated with ion transport membrane for oxy-fuel combustion

Ben‐Mansour

Adebiyi

2016

Summary The performance of a carbon free fire‐tube boiler utilizing two‐pass oxygen transport reactors was numerically investigated. The influences of the oxygen transport reactors wall temperature on the reaction rate, oxygen permeation and heat flux were quantified. The performance of the reactors has been investigated at elevated temperature. It is observed that both heat transfer and combustion characteristics can be optimized at an elevated temperature of 1373 K. Increasing the mass fraction of methane in this reactor to 6% results in improvement of the heat transfer and combustion characteristics in the reactor. Further increase in CH4% did not lead to any significant improvement. The fuel flow rate variation did not have any significant impact on the reactor performance. It is indicated that the membrane temperature has significant effect on the reaction rates and oxygen flux in the upstream region in particular. Copyright © 2016 John Wiley & Sons, Ltd.