Potential use of liquid metal oxides for chemical looping gasification: A thermodynamic assessment

Highlights: • A liquid chemical looping gasification concept for syngas production was introduced. • Influence of different operating parameters on the syngas production was performed. • Liquid oxygen carrier/feedstock and steam/feedstock ratios were crucial factors. • Exergy efficiency of the liquid chemical looping gasification was 67%. • H₂/CO ratio was as high as 2 suitable for gas to liquid (GTL) processes. - Abstract: A new concept for syngas production is proposed in which a liquid metal oxide (here copper oxide) is implemented as an oxygen carrier for chemical looping gasification. The proposed system consists of two interconnected bubble reactors as the fuel and air reactors, through which a liquid metal oxide is circulated to be successively reduced and oxidised providing the required heat and oxygen for the gasification reaction. The proposed system offers a potential process to avoid challenges such as agglomeration and sintering that are typically associated with the solid metal oxides that have previously been proposed for chemical looping gasification. Thermochemical equilibrium models are presented that show acceptable agreement with the available data. The model is then used to estimate that the carbon conversion of feedstock is up to 84.6% for gasification and 100% for combustion with the proposed concept. In addition, the mole fraction of gaseous copper oxide in the outlet stream from the air reactor is estimated to be 10⁻¹¹, which implies that no further process is required to separate the evaporated copper oxide from the syngas.