Chemical looping combustion (CLC) is a novel technology, which has the potential to produce a binary mixture of CO_2 and H2O in the flue gas. In a CLC flue gas, the CO_2 can be separated simply by condensing the H2O, similar to an oxy-fuel process. For a CLC process, one unique characteristic is the use of a solid “oxygen-carrier” to transport oxygen from the air to a separate fuel reactor. In recent years, extensive research has been conducted on CLC of gaseous fuels. However, CLC of solid fuels is a growing area of research, particularly in the area of future clean coal power generation. One of the technical issues with a coal CLC process is how to minimize ash accumulation in the system. One approach is to drain both the carrier and the ash from the system continuously, but this requires continuous feed of fresh oxygen carrier into the system. The approach investigated in this paper is whether the ash can be effectively separated from the carrier material using differences in aerodynamic characteristics between the ash and the carrier particles. The benefits of an aerodynamic solid-solid separation process include 1) reducing solid waste streams, and 2) reducing the requirement for fresh oxygen carrier make-up, and 3) reducing the operating cost for carrier make-up. This paper presents the preliminary experimental results of solid-solid separation in a bubbling fluidized bed (BFB) cold model. Three series of experiments are reported for a 10 cm diameter cylindrical bubbling fluidized bed. In the first series, a copper-based oxygen carrier and acrylic chips with a particle density ratio of 2.8 are investigated. The acrylic chips have been chosen to simulate the aerodynamic characteristics of coal-ash and char. In the second series of experiments, ilmenite and glass beads with a particle density ratio of 1.88 are investigated. The third series includes two different size distributions of alumina oxide mix with glass beads, which has density ratio of 1.59. Experimental data on the effects of static bed height, gas velocity, and particle size on the entrainment of particles from bubbling fluidized beds of binary mixture are discussed in this paper. Preliminary modeling results using the Barracuda code are also described and compared to the experimental data.
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