Investigation of heat management for CLC of syngas in packed bed reactors

Different configurations for an adequate heat management in dynamically operated packed bed reactors for Chemical Looping Combustion (CLC) have been investigated and compared using syngas from a coal gasification unit as fuel. Ilmenite has been selected as oxygen carrier for the process mainly because its high melting point, allowing to reach high temperature close to 1200°C, excellent selectivity to the formation of CO₂, natural availability and related low cost. Packed bed reactors for chemical looping combustion processes have recently been proposed as alternative to the interconnected fluidized bed reactors for pressurized systems, because solid circulation and gas-solid separation are not required. Due to the transient behavior of packed bed reactors, an adequate heat management is essential to couple these reactors with other units of the power plant. Heat management refers to the dynamic operation of fixed bed reactors to achieve the required solid temperature and conversion and to produce the gaseous streams at the optimal operating conditions for the studied power plant. Two different reactor cycle strategies have been analyzed: (i) Oxidation/Heat Removal/Purge/Reduction/Purge with different air inlet temperatures for different solid active material contents in the oxygen carrier; (ii) Oxidation/Purge/Reduction/Heat Removal with inert gas. The effect of Water Gas Shift (WGS) activity of the oxygen carrier has also been discussed considering the most relevant technical and economic aspects. Due to the low rate of solid conversion of ilmenite with CO-rich syngas during the reduction cycle and due to the change in temperature of the produced gases, the first cycle strategy is not feasible for a continuous operation in a power plant, while the second cycle strategy appears very interesting for implementation of the CLC process using packed bed reactors with ilmenite as oxygen carrier in power plants.