# Experimental Investigation of Oxygen Carrier Aided Combustion (OCAC) with Methane and PSA Off-Gas
## 4 Conclusions  
A laboratory-scale bubbling fluidized bed with an approximate bed height of 15 cm was used for oxygen carrier aided combustion of methane and PSA off-gas. Three bed materials were compared--sand, rock ilmeinte and a manufactured manganese-based perovskite material (C28)--at bed temperatures ranging from 600 \({}^{\circ}\)C to 900 \({}^{\circ}\)C. The gas conversion was monitored by using measurements of temperatures and gas composition over the length of the reactor. The results with methane showed that an improved in-bed fuel conversion could be achieved using oxygen carriers as bed materials instead of sand, where C28 showed the best results. This can be traced to the fact that the oxygen carriers enable improved contact between fuel and oxygen, due to the addition of an additional fuel conversion mechanism in the form of the gas-solid reaction between fuel and metal oxide. At a bed temperature of 900 \({}^{\circ}\)C, close to complete methane conversion was observed, 99.3-99.7%, with ilmeinte and C28 as bed materials 9 cm from the distribution plate, whereas the result for sand was 86.7%. The oxygen carriers also showed significantly higher methane conversion at lower temperatures. A test where the air-to-fuel ratio was varied from 1 to 1.2 showed only a small improvement in methane conversion. The experiments with PSA off-gas as fuel showed overall high gas conversion for all bed materials at moderate temperatures (600-750 \({}^{\circ}\)C), where only minor differences were observed between the bed materials. The suggestion to integrate OCAC with SMR plant is supported by the experimental results in this work, since:  
* High fuel conversion in the bed was detected with PSA off-gas and methane, especially at higher temperatures where close to complete gas conversion was observed. * Very limited NO emissions were observed with methane as fuel apart from cases where close to all of the fuel conversion took place above the bed. The emissions were especially low at high temperatures (< 14 ppm at a bed temperature 900 \({}^{\circ}\)C with all bed materials). * Almost no NO emissions at all were detected using PSA off-gas as fuel (< 11 ppm at bed temperatures \(\geq\) 700 \({}^{\circ}\)C with all bed materials). **Supplementary Materials:** The following are available online at [[https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)]([https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)) 7/11/1/210/s1, Table S1: Measured average temperatures at different measurement points operating with sand, C28 and ilmeinte with methane as fuel. Table S2: Measured average concentrations of CH\({}_{4}\) (%, dry) at different measurement points operating with sand, C28 and ilmeinte with methane as fuel. Table S3: Measured average concentrations of CO (%, dry) at different measurement points operating with sand, C28 and ilmeinte with methane as fuel. Table S4: Measured gas concentrations of CO (%, dry) at different measurement points for all three bed materials using PSA off-gas as fuel. Table S5: Measured gas concentrations of CH\({}_{4}\) (%, dry) at different measurement points for all three bed materials using PSA off-gas as fuel. Table S6: Measured gas concentrations of CO\({}_{2}\) (%, dry) at different measurement points for all three bed materials using PSA off-gas as fuel. Table S7: NO concentration (ppm, dry) at different measurement points with different bed materials and measurement points using PSA off-gas as fuel. **Author Contributions:** Conceptualization, V.S. and M.R. ; methodology, V.S. & M.R. ; formal analysis, V.S. ; investigation, V.S. ; writing--original draft preparation, V.S. ; writing--review and editing, V.S., M.R., T.M. and A.L. ; visualization, V.S. ; project administration, V.S. ; funding acquisition, M.R. All authors have read and agreed to the published version of the manuscript.