(143c) CFD Simulations of the NETL Chemical Looping Experiment

This paper describes the CPFD® math-based method for modeling three-dimensional gas-solids flows, and application of the method to a prototype chemical looping combustion (CLC) experiment at the USDOE National Energy Technology Laboratory (NETL). Because the calculation method is applied to the cold-flow NETL perspex looping experiment, the calculation is isothermal without combustion and oxygenation of particles. The NETL cold-flow CLC experiment and the CPFD calculation are a complete closed, solid flow loop system representing the basic components of a CLC. The CLC-experiment contains an oxidation riser, cyclone and a three compartment combuster. The calculations are made using the CPFD numerical scheme which solves both the fluid and particle momentum and mass equations. The CPFD method can also solve the energy and chemistry equations, but these are not included in the prediction of the NETL perspex experiment. The particle momentum description is based on the multi-phase particle in cell (MP-PIC) method, and the fluid phase is solution of on the three-dimensional averaged Navier- Stokes equation. The CPFD method has tight coupling between gas-solid phases and can model virtually unlimited number of particle sizes and solid materials. Sorbent particles, carbon-based fuel particles, and any other combinations of solid material can all be mixed with their own size distributions. Video images from CPFD calculated solids flow compare well with measured movies of solids flow in the NETL perspex experiment. Cold flow experiments in concert with proper computational modeling allows many performance aspects of the chemical looping system to be studied. Operating conditions can be varied over a wide range to study the effect on the system pressure balance, the solids circulation rate, the particle residence time distribution, gas leakage between the air and the fuel reactors, and the effectiveness of loop seals. The validation of the accuracy of the CPFD method in predicting the NETL CLC experiments provides confidence when applying the CPFD method when predicting a full scale gasifier with the scaling built into the physics.