Chemical-looping gasification of biomass in a semi-Commercial plant using granulated copper smelter slag as oxygen carrier

Chemical looping gasification (CLG) is a novel technology for syngas production that utilizes two interconnected fluidized bed reactors vessels, referred to as the air reactor (AR) and the fuel reactor (FR), The circulating bed material is referred to as oxygen carrier and has the capacity to provide oxygen to the fuel. The experimental campaign that forms the basis of this study was performed in the Chalmers semi-commercial research boiler/gasifier using copper smelter slag as oxygen carrier and wood pellets as fuel. The temperature of the gasifier was kept around 830°C and the total duration of the experiments with fuel was 24 h, spread over three days of operation. The maximum thermal input to the gasifier corresponded to 2 MW th . Variations of fuel feeding rate, solids circulation and fluidization velocity in the gasifier were made to investigate the influence on the fuel conversion. The study focuses on the operational results from the campaign but also includes basic material characterization of the used copper smelter slag. The dry raw gas composition from the gasifier was approximately 40% CO 2 , 20% H 2 , 20% CO, 7% CH 4 , 2% C 2 H 4 , with the balance being mostly N 2 . The total formation of tars was 32–48 g/kg fuel, which is higher than what has previously been found with the reference oxygen carrier material ilmenite, but lower than when using conventional bed material such as silica sand. The char conversion was found to be 34–64% with a clear correlation to the fuel flow. At lower fuel flow, higher conversion of the char could be achieved. The results clearly show the potential for using CLG to generate a valuable product gas from a biomass feedstock, thus enabling the combination of production of transportation fuels and negative emissions of CO 2 .