The hydrodynamics of the high-density bottom zone in a CFB riser analyzed by means of electrical capacitance tomography (ECT)

摘要

The hydrodynamics of the bottom region of a CFB riser have been investigated. Experiments were performed an a DJ4-m LD. CFB riser user using FCC catalyst. The riser solids mass flux was varied between 148 and 302 kg/rn2 s and the superflcin1j~s idoc~ty between 17 and 4.7 m,’s. Pressure transducers were employed to evaluate the axial profile, especially the height of the bottom n~oe in the CFB tber. The bottom zone itself was ar~alyzed by means of electrical capacitance tomography (ECT). Radial solk9~oncaiha6oe profiles. ~obability density distribution profiles. standard deviation profiles and frequency spectra were determined a orderto quantif~- the bottom zone hydrodynamics. The different investigation methods are in a good agreement and indicate a core~mawmtse ~ructure in Ac bottom zone of the CFB riser. A lean core region with a narrow probability density distribution and a small sia.4siS deviation of flue solids concentration exists, while the wall region exhibits a high solids concentration with a wide probability ~iibution and a large standard deviation of the solids concentration. Within the bottom zone the hydrod,~ynamics vary a danuge in beight or external solids mass flux.