(408c) Development of a Carbon Stripper Particle Separation System for Chemical Looping Applications

Chemical looping combustion (CLC) is a promising new technology for reducing carbon emissions from coal-based energy generation. The most significant limiting factor for implementation of this technology is the ability to remove unburnt carbon (char) from the oxygen carrier material as it is cycled between the fuel and air reactors within the CLC unit, thus preventing formation of CO₂ formation in the air reactor. In an effort to address this critical issue, a novel carbon stripper unit has been developed for the separation of unburnt char from oxygen carrier compounds for use with chemical looping combustion (CLC) systems. The carbon stripper unit consists of a conical spouted bed with a thin annular ring located between the spout cone and the bed wall. A sweep gas is injected into this annular region such that the sweep gas velocity within the annulus falls between the terminal velocities of the oxygen carrier and char particles. This facilitates separation of particles by weight, as the heavier oxygen carrier particles are allowed to fall down through the annular region, while the lighter char particles are prevented from entering the annulus. The char particles are ultimately entrained out of the dense bed region and into the freeboard region by the spouting gas, where they are carried out of the carbon stripper unit via elutriation. Preliminary results from experiments carried out in a cold flow prototype unit have demonstrated favorable separation characteristics.