# Experimental Investigation of Oxygen Carrier Aided Combustion (OCAC) with Methane and PSA Off-Gas
## 1 Introduction
One example of such manufactured material is the calcium-manganite-based material of single perovskite structure CaMn0.775 Mg0.1 TiO.125O3-8 (also referred to as C28). This material was developed within EU-FP7 research projects, named INNOCUOUS and SUCCESS, between 2010-2017 [13]. The overall goal of the INNOCUOUS project was to develop efficient synthetic oxygen carrier particles with zero or at least very little nickel, specifically for fuels rich in methane. In the material screening, it was observed that materials based on calcium manganite with the addition of small amounts of magnesium and titanium were regarded among the most promising. Based on this work, the SUCCESS project aimed at finding suitable materials for low-cost production and the adaptation of a large-scale production process of these materials. A summary of the INNOCUOUS project was published by [PERSON] et al. [14] and the development process of calcium manganite materials is summarized by [PERSON] et al. [13] and additional articles presenting experimental work with C28 can be found in [15, 16, 17, 18]  
There are a few examples where the addition of oxygen carrier particles to BFB systems for methane combustion have been attempted. At a bed temperature of 700 \({}^{\circ}\)C it was shown that, by replacing as little as 0.13-1.3% of the inert bed material with iron oxide (Fe2O3), a significant reduction in methane and CO concentration could be achieved in the dense bed by increasing the oxygen carrier inclusion rate [1]. The effect of replacing more inert bed material with oxygen carrier material has also been attempted, where it could be seen that a 50% inclusion rate of manganese ore decreased the concentration of CO in the exhaust gas at 800-850 \({}^{\circ}\)C in general and especially at low air-to-fuel ratios [19]. However, since no temperature profile nor concentration profile for CH4 or CO was determined for the system, it is difficult to use this as proof that higher inclusion rates move the methane conversion into the dense bed. Results from experimental campaigns in a 12 MWth CFB boiler with wood chips using ilmenite [9], manganese ore [20] and steel converter slag [21] as a bed material all indicate that the partial substitution of silica sand as a bed material with these oxygen carrier bed materials increases fuel conversion and thus also the heat generation in the dense bed. This was concluded mainly based on the temperature profile of the boiler. In all instances, the temperature profile was significantly altered, such that the temperature at the top of the dense bed [20,21] was higher when the oxygen carrier was present in the bed compared to using only silica sand. Additionally, the temperature drop in the cyclone [9,20,21] was more pronounced when oxygen carriers were present, suggesting that less combustion took place here compared to when sand was used. One example of a possible application of bubbling fluidized beds with methane/light hydrocarbons as fuel is to use the bed as a heat source for steam reforming [22, 23, 24, 25, 26]. In this process, the fuel gas is expected to be a mix of PSA off-gas consisting of mainly CO\({}_{2}\) but also H\({}_{2}\), CO and CH\({}_{4}\) and supplementary fuel in the form of light hydrocarbons. The aim is to burn the fuel gas to enable the transfer of heat from the combustion to the immersed steam reforming tubes, which is envisaged to enable improved overall process performance. Methane constitutes a significant part of this fuel gas and it is therefore important to convert the fuel in the dense bed of the bubbling fluidized bed to generate the heat of combustion inside the bed. If it is possible to display experimental results, showing that it is possible convert the methane inside the dense bubbling bed, it should be possible to also convert other targeted gaseous fuels with most common oxygen carriers. This reasoning is in line with the results presented by [PERSON] et al.