Simulation study on the influence of feedstock feeding position on chemical looping gasification performance

Chemical looping gasification is an innovative process for chemical recycling of residues that enables the production of nitrogen-free syngas without requiring an air-separation unit. Recently, significant advancements of the technology were made such as the demonstration of autothermal gasification at megawatt scale. However, to optimize reactor design, there are still open issues. One such problem is the positioning of the feedstock feeding position, which can have a significant influence on the process efficiency and tar yields. In this work, the influence of the feeding position with respect to the reactor height was analyzed using coupled CFD-DEM simulation. The results indicate that feeding above the oxygen carrier (OC) return results in a higher carbon conversion and cold gas efficiency, while feeding below the OC inlet leads to lower tar yields and OC conversion. The main influences for this behavior are temperature during pyrolysis which increases with the height due to the addition of hot OC from the AR and residence time of the gases in contact with OC. Furthermore, feeding into the OC return line can be advantageous due to the higher temperatures in the air reactor. However, this effect can be diminished by the formation of cold spots during pyrolysis.