Application of the magnetic material in incineration bottom ash as oxygen carrier for biomass chemical looping gasification

Concerns about the cost of oxygen carrier (OC) manufacturing and the promotion of resource recovery have led to increasing research interest in the application of solid waste as an alternative to OC for chemical looping process (CLP). Magnetic materials in municipal solid waste incineration bottom ash (denoted as IMF) with ferrous metals as the main component were investigated as potential OCs for biomass chemical looping gasification (BCLG). An iron-based synthetic OC (called syn-75) was prepared for comparative studies. Thermogravimetric analysis (TGA) of IMF coupled chemical looping combustion (CLC) of CO in a fluidized bed confirmed its excellent reactivity and stability. Of all the IMFs tested (IMF-2 to IMF-6 classified by particle size), IMF-4 exhibited the highest CO combustion efficiency (up to 92 %) due to its highest iron content. However, reduction rates do not always follow the order of iron content. For instance, IMF-4 (Fe2O3%=73.3 %) illustrated better performance than syn-75 (Fe2O3 % = 78.0 %) in syngas production from biomass chemical looping gasification (BCLG), suggesting that other active phases in IMF-4 may be involved to exert a synergistic effect, which can promote deeper reduction of iron oxides, echoed from X-ray diffractometry (XRD) results. In addition, IMFs demonstrate limited surface coking throughout the BCLG process. These findings mainly endorse IMF as a promising natural OC for BCLG.