(53g) Computational Fluid Dynamic Simulation of a Chemical Looping Process for Methane Combustion

Chemical Looping Combustion is an emerging technology for the “carbon-capture ready” production of energy from fossil fuels.  Two chemical looping units have been recently constructed at the National Energy Technology Laboratory to specifically investigate and develop this technology: a high-temperature chemical looping reactor and cold flow system with a similar geometry and optically accessible.   Computational fluid dynamic simulations were performed of the cold flow system and compared to experimental pressure measurements and high-speed video at several operating conditions.  The short-term goals of the experiments and simulations of this cold flow unit are to help plan and analyze the future experiments in high-temperature reactor.

The chemical looping reactor consists of two interconnected fluidized beds.  The first bed, the air reactor, consists of a lower mixing zone with a diameter of 6 inches and 30 inches high connected to a riser 2.5 inches in diameter and 115 inches high.  Two additional ports are provided to add secondary fluidization air to help transport solids through the riser.   The second bed, the fuel reactor, is 8 inches in diameter and 64 inches high. The exit of the air reactor is connected to the fuel reactor via a cyclone, loopseal and dip leg.  An L-valve connects the exit of the fuel reactor to the air reactor inlet.   The pressure is measured at 19 locations around the system at 5 Hz.  The circulation rate is estimated from rate of change in pressure drop across the fuel reactor bed after the solid flow to the fuel reactor has been stopped.  This procedure assumes that the circulation rate is regulated by the L-valve.  In the tests which were simulated glass beads are circulated.  In addition to circulating experiments, the data set includes fluidization tests for the air reactor, fuel reactor and loop seal.

Predictions for methane conversion in a NETL experimental facility will be presented. The performance predictions will be assessed for a variety of operating conditions including the effects of fuel gas composition, fuel gas flow rate as well as oxygen carrier type and particle size.