Investigation of Chemical Looping Combustion with a novel two stage fuel reactor for reduction of CO2 emissions

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Compared to conventional thermal power plant processes, Chemical Looping Combustion (CLC) enables an inherent CO2 capture without the need for costly separation of N2 and CO2. At the Institute of Solids Process Engineering and Particle Technology at Hamburg University of Technology, a 25 kWth pilot-scale CLC reactor with two combustion reactor stages is being operated. The second reactor stage enables higher conversion of volatile fuel gases. Experience has been gained with the combustion of methane and coal. Recently conducted first experiments with wood as fuel showed very high conversion rates. In the future, negative CO2 emissions, which are unavoidable for reaching the world’s 1.5 °C climate targets, should be achieved by using biomasses as a fuel. The aim of this project is to investigate wood particles, sewage sludge, agricultural waste and torrefied biomass as fuel in the two-stage 25 kWth CLC system. Due to the different compositions of the fuels, a detailed investigation of the different reaction mechanisms and optimization of the operating conditions of the pilot plant will be performed. Process dynamics such as start-up and shut-down as well as load changes will be investigated. Furthermore, a new reactor concept will be developed: The fuel reactor stages will be replaced by a spouted bed with an annular gas inlet to achieve lower pressure losses, which are essential for future scale ups. The experimental investigations will also be used to validate and extend a model in the open-source flowsheet simulation environment DYSSOL (Dynamic Simulation of SOLids Processes), which can then be used in the future to design and optimize new plant configurations. DYSSOL was developed in the DFG priority program (SPP1697) with a total of 27 subprojects across Germany and published in 2020. The focus of this work is on the formulation of enthalpy balances as well as an interface to connect DYSSOL and a software for CFD multiphase particle-in-cell method simulation. At last, a flowsheet simulation of an entire hypothetical 100 MWth industrial scale bio-CLC plant will be performed. Here for a first time, the whole process with the hydrodynamics and the chemical reactions including gasification and devolatilization of biomass particles will be included into one simulation. Pilot-scale biomass experiments and industrial-scale numerical simulations are essential for the development and design of future larger scale facilities. This work will evaluate if CLC is a potential candidate for future use for bioenergy with carbon capture and storage.