Design and Experimental Investigation of a Novel Interconnected Fluidized Bed for Chemical Looping Conversion of Solid Fuel

Chemical looping offers a versatile platform to chemical conversion and energy utilization in a clean and efficient manner. Except the chemical looping combustion/gasification, novel processes based on the chemical-looping thought have sprung up. Chemical looping conversion of solid fuels attracts more attention, and significant progress has been made in last decades. One technical challenge of using solid fuels involves the reaction enhancement between oxygen carrier and solid fuel. Because both the oxygen carrier and solid fuel are solid particles, the intensified mixing between the two different solid particles in fuel reactor seems to be of importance.

Chemical looping reactors are widely accepted as interconnected fluidized beds. Herein, a novel interconnected fluidized bed for chemical looping conversion of solid fuel was designed. Firstly, aiming to intensify the reaction between solid fuel and oxygen carrier particles, a novel impinging stream feeding device at the top or bottom of the fuel reactor was designed. Both the hot oxygen carrier particles from air reactor and solid fuel particles carried by the high-speed gasification gas flow were impinged in the opposite direction. The impinging stream can ensure the excellent mixing of two type particles by crushing solid fuels into fine particles at the high temperature. Secondly, to reduce unburnt volatiles and gasification products escaping out of fuel reactor, the fuel reactor was designed as two-staged fluidized bed. First stage was selected as riser or downer, of which flow pattern is approximate to plug flow, for the pyrolysis of solid fuel. The other stage was selected as turbulent fluidized bed in order to fully convert the solid fuel char.

To verify the stable operation of the designed interconnected fluidized bed, cold model setup was erected. Flow characteristics of particles in the built cold model were investigated. Experimental results indicated that the designed chemical looping reactor possessed excellent flow performance. It also can provide a new way for solid fuel conversion by the gas-solid-solid reaction system.