Impact of gas distributor on hydrodynamics in a cold flow annular dual fluidized bed for pressurized chemical looping

A novel reactor being developed for pressurized chemical looping (PCL) is presented in this paper. The reactor is a compact annular fluidized beds configuration incorporating directional jets that circulate solids between fluidized bed sections in a single vessel, eliminating the need for two separate fluidized bed reactors and the associated external solids transfer.

Initial studies on the PCL reactor concept have been done in a cold flow facility, where the associated hydrodynamics and gas leakage in the dual fluidized bed column are assessed. The column has an outer process diameter of 0.57 m, an inner process diameter of 0.114 m and a height of 3.87 m. The studies were completed with 251 μm particles with a particle density of 2987 kg/m3.

The results indicate that there are dead zones within the beds that are present at fluidization ratios as high as 2 U/Umf. A large fraction of the dead zones are likely caused by limitations in tuyere placement due to the small scale of the cold flow unit that will not be present in commercial units. Initial gas leakage tests with this distributor confirm that increasing superficial gas velocity increases the amount of gas leakage between reactor sections. There is an indication that external factors such as a difference in back pressure between PCL reactor sections may increase the gas leakage.

The results presented here provide an introduction to operation of this first-of-its-kind PCL reactor under cold flow conditions. Further tests are being performed to better understand this unique fluidized bed configuration and to validate the computational particle fluid dynamic (CPFD) models being used to design PCL reactors. Consequently, the validated CPFD models will be used to guide geometry selection and set operating conditions for a hot flow pilot facility.