(816c) On the Design and Modeling of a Rotary Reactor for Chemical-Looping Combustion With a Nickel-Based Oxygen Carrier

Chemical-looping combustion (CLC) is a novel and promising option for carbon capture and sequestration (CCS). Currently almost all the research has been focused on developing CLC-based interconnected fluidized-bed reactors. In this report, a rotary reactor with a nickel-based oxygen carrier (OC) for gas fueled CLC is designed and analyzed. In the reactor, a solid wheel rotates between the fuel and air streams at the reactor inlet and exit. The rotary wheel consists of a large number of micro-channels with nickel oxide coated on the inner surface of the channel walls. The OC oxidizes the fuel in the fuel zone to generate undiluted CO₂ and then it is regenerated in the air zone. Thus pure CO₂ can be readily obtained from the flue streams of the fuel zone and the dilution from the air is avoided. Gas flows through the reactor at elevated pressure and it is heated to high temperature by fuel combustion which can then be used to drive the gas turbine. Design parameters have been selected on the basis of the characteristics of the nickel-based OC and for a thermal capacity of 1MW, the reactor has a diameter of around 1.0m, and a height of about 0.5m. Owing to a relatively slow oxidation rate, an intermediate range of the OC conversion as well as a relatively large share of air sector is used for the design. A one-dimensional plug-flow model has been developed to predict the performances of the reactor. The results indicate that both the fuel conversion and the carbon separation efficiencies are close to unity. In the periodic stationary operation, stable performances are obtained with the gas temperature increasing monotonically from 550℃ to 1200℃. The overall energy in the solid phase is balanced between the reaction heat release, conduction and convective cooling. Sensitivity study has been conducted on the base-case design and the results revealed that the most important parameters are the reduction kinetics, the operating pressure and the feed stream temperatures. Advantages of the rotary design with the nickel-based OC include the compactness, up-scaling feasibility, periodic and stationary operation with limited energy penalty from operation. The potential challenges are also discussed in the report.