Solid-Solid Separation in a Bubbling Fluidized Bed Cold Model

摘要

Chemical looping combustion (CLC) is a novel technology, which has the potential toproduce a binary mixture of CO_2 and H2O in the flue gas. In a CLC flue gas, the CO_2 canbe separated simply by condensing the H2O, similar to an oxy-fuel process. For a CLCprocess, one unique characteristic is the use of a solid “oxygen-carrier” to transportoxygen from the air to a separate fuel reactor. In recent years, extensive research has beenconducted on CLC of gaseous fuels. However, CLC of solid fuels is a growing area ofresearch, 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 accumulationin the system. One approach is to drain both the carrier and the ash from the systemcontinuously, 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 separatedfrom the carrier material using differences in aerodynamic characteristics between the ashand the carrier particles. The benefits of an aerodynamic solid-solid separation processinclude 1) reducing solid waste streams, and 2) reducing the requirement for fresh oxygencarrier make-up, and 3) reducing the operating cost for carrier make-up.This paper presents the preliminary experimental results of solid-solid separation in abubbling fluidized bed (BFB) cold model. Three series of experiments are reported for a10 cm diameter cylindrical bubbling fluidized bed. In the first series, a copper-basedoxygen carrier and acrylic chips with a particle density ratio of 2.8 are investigated. Theacrylic chips have been chosen to simulate the aerodynamic characteristics of coal-ashand char. In the second series of experiments, ilmenite and glass beads with a particledensity ratio of 1.88 are investigated. The third series includes two different sizedistributions 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 theentrainment of particles from bubbling fluidized beds of binary mixture are discussed inthis paper. Preliminary modeling results using the Barracuda code are also described andcompared to the experimental data.