Performance of a highly reactive impregnated Fe2O3/Al2O3 oxygen carrier with CH4 and H2S in a 500Wth CLC unit

Abstract

A synthetic Fe-based oxygen carrier prepared by impregnation using -Al 2 O 3 as support, successfully tested for gas CLC combustion, has been now evaluated with respect to gas combustion in a 500 W th CLC continuous unit when the fuel, CH 4 , contained variable amounts of H 2 S.Full gas combustion was reached at oxygen carrier-to-fuel ratio values higher than 1.5. The presence of sulfur in the fuel gas hardly affected the reactivity and combustion efficiency of the oxygen carrier, independently of the amount of sulfur in the gas stream. All the sulfur introduced as H 2 S in the fuel reactor (FR) was released in the same reactor as SO 2 . Furthermore, oxygen carrier particles extracted from the CLC unit after the experimental tests with H 2 S addition were 3 characterized by means of different techniques and no sulfur was detected in any case. The impregnated Fe-based oxygen carrier was highly reactive and sulfur resistant, and can be considered as a suitable material for CLC with gaseous fuels that contain sulfur.

Reduction kinetics of lanthanum ferrite perovskite for the production of synthesis gas by chemical-looping methane reforming

“…However, when the temperature is further increased to 1173 K, new characteristic peaks for La(OH) 3 , trace La 2 O 3 and metallic Fe will present, indicating structure collapse of perovskite. Although the metallic Fe can be oxidized to Fe 2 O 3 during cyclic oxidationreduction process, the selectivity of CO will be poor (Monazam et al, 2013;Piekiel et al, 2012;Cabello et al, 2014b;Bhavsar et al, 2014). Assuming that one monolayer of oxygen amounts to 4 μ mol/m 2 (Kaliaguine et al, 2001), the calculated number of O atoms is about 264 μmol/m 2 involving in CLMR process before carbon deposit occurs, which is corresponding to 66 monolayers.…”

Kinetic determination of a highly reactive impregnated Fe2O3/Al2O3 oxygen carrier for use in gas-fueled Chemical Looping Combustion

“…In order to prevent the mixing of fuel and air, a 2-minute flow of N 2 was fed between the reducing and oxidizing period. This material showed excellent stability in redox reactivity over hundreds of cycles [17]. Data obtained during the first redox cycle were selected for kinetic determination.…”

“…These oxygen carriers have shown adequate reactivity under atmospheric [10][11][12] and pressurized [13] conditions and high reactivity with CO and H 2 , and do not present thermodynamic limitations to fully convert CH 4 4 can be formed as a reduced compound and also achieve complete combustion of gas to CO 2 and H 2 O [14][15][16][17]. Thus, the oxygen transport capacity of the oxygen carrier is increased three times in comparison with the Fe 2 O 3 -Fe 3 O 4 redox couple.…”

“…Thus, the oxygen transport capacity of the oxygen carrier is increased three times in comparison with the Fe 2 O 3 -Fe 3 O 4 redox couple. Furthermore, Fe-based oxygen carriers present a low tendency to carbon deposition [18] and no risk of sulphide or sulphate formation at any concentration or operating temperature when H 2 S-containing gases are used as fuels [17,[19][20].…”

“…This material showed complete combustion of CH 4 during continuous operation in a 0.5 kW th CLC unit [16]. Additionally, it presented adequate resistance to agglomeration and attrition, even when H 2 S was present in the gas fuel at very high concentrations [17,[19][20].…”