(43a) Internally Circulating Fluidized-Bed Reactor for Inherent CO2 Capture Using Chemical Looping Combustion

Chemical looping process is one of the most promising technologies for CO₂ capture on terms of efficiency and economy. Hence, it provides the means to convert fossil fuel to electricity and/or chemical products with inherent separation of CO₂ and without significant energy penalties. Pressurized operation of chemical looping based processes is however necessary for maximizing their energy efficiency and speeding up their industrial deployment.

This study provides the prospects and opportunities that exist for novel application of the internally circulating reactor (ICR) to be used as an alternative to the conventional dual fluidized-bed reactor. The concept consists of a single reactor that combines two sections, (i.e., the fuel and air sections) with internal physical separations. Specifically the concept aimed to simplify the design, ease the solid circulation, avoid using costly gas/solid separation system, (i.e., cyclone and loop seals), operate at high pressure easily in a single pressurized vessel and eventually bring the chemical looping technology a step closer to commercialization.

Hydrodynamic study carried out in a pseudo-2D cold-flow unit have confirmed that the principle of ICR can be successfully applied to a chemical looping technology process, with easy control of solid circulation and minimum gas leakage between the two sections [1,2]. In this study a hydrodynamic study carried out in the 3D ICR reactor under cold conditions to identify an operation window in which solid circulation is stable and gas leakage is minimum. The effects of the static bed height, bed material properties and gas fluidization velocities on solid circulation rate and gas leakage were determined. The solids circulation rate in the 3D reactor is quantified based on the correlation extracted in the pseudo 2D experiments linking solids circulation rate to the pressure difference between the reactor chambers. Ergun equation is used as a verification of the accuracy of the estimated solids circulation rate based on the measured gas leakage and pressure difference between the reactor chambers. The same equations are used to design the operation window for the ICR under CLC conditions. Reactive experiments are ran to validate the Ergun equation prediction of solids circulation rate by using pressure and gas composition measurements.

Finally, scaling laws are used to translate the operating window designed via hydrodynamic experiments to reactive experiments with the aim of maximizing the fuel conversion and CO₂ capture efficiency. Reactive CFD simulations are completed to verify the accuracy of this scaling and some initial reactive experimental results will be presented to quantify the validity of these methods.

References:

1. A. Zaabout, S. Cloete, S. Amini, Innovative Internally Circulating Reactor Concept for Chemical Looping-Based CO2 Capture Processes: Hydrodynamic Investigation, Chemical Engineering & Technology, 39 (2016), pp. 1413-1424.
2. S. Cloete, A. Zaabout, and S. Amini, The Internally Circulating Reactor (ICR) Concept Applied to Pressurized Chemical Looping Processes. Energy Procedia, 2017. 114 (Supplement C): p. 446-457.