Modeling of ion transport reactor for oxy-fuel combustion

Abstract

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.

Experimental and Numerical Investigation of La2NiO4 Membranes for Oxygen Separation: Geometry Optimization and Model Validation

“…Figure 20 presents the mass fraction distribution of 0 2 in the permeate side of the ITM for increasing ratios of O2/N2 mixture. [17,18,23] that confirm the above stated results. The high values of mass fractions at the edges may be attributed to the possible accumulation of oxygen molecules due to lower sweep gas velocities as can be seen from Fig.…”

CFD (computational fluid dynamics) analysis of a novel reactor design using ion transport membranes for oxy-fuel combustion

“…Therefore, the flow is laminar. Many combustion studies [32,33,55] omit the use of radiation models in their investigations either because its role is less important or to save computational time. The effect of radiation in the case considered here may be important because of the use of wider channels as shown next.…”

“…Their studies paved the way to research on synthesis and analysis of LSCF membranes [14]. Farooqui et al [15] modeled cylindrical ion transport reactor for co-current and counter current flows and found that oxygen to fuel mass ratio increases as the percentage of CO 2 increases in the sweep gas. In a series of papers, Hong et al [16e18] developed accurate and comprehensive analysis of the coupling between heat and mass transfer on both sides of the membrane.…”

Experimental study of ash formation under O2/CO2 combustion

“…The characteristics of combustion, heat transfer, burnout, pollutants, and slagging under oxy‐fuel combustion (Oxy) conditions are very different from those under air combustion (Air) conditions. Many scholars have studied the coal combustion and pollutant emission characteristics of oxy‐fuel boilers . However, there has been little information about the deposition characteristics of ash .…”

“…Many scholars have studied the coal combustion and pollutant emission characteristics of oxy-fuel boilers. [6][7][8][9][10][11][12][13][14][15][16] However, there has been little information about the deposition characteristics of ash. 17,18 Coal contains a certain amount of inorganic material.…”