Local solid-particle concentration and flow development in a long CFB riser

To investigate the non-uniformity in radial distribution of time mean solid-particle concentration and its axial development. Local solid-particle concentrations at 11 radial positions on 8 axial levels of the riser in a CFB riser of 15.1 m high and 0.l m i.d. were systematically measured by a reflective-type fiber-optic particle concentration probe, with superficial gas velocity ranging from 3.5 to 8.2 m·s^-1 and solid-particle circulation rate from 53 to 202 kg·m^-2s^-1. Results showed that the flow developments in various radial locations are not synchronized, but extended gradually from the core region to the wall, until finally a fully developed flow is achieved across the whole cross-section of the riser. The flow development at the annulus region near the wall, as a control process of the whole flow development in the riser, is not only much slower, but also more sensitive to the change of operation conditions than that at the core region. It is also found that in the acceleration section, the radial distribution of reduced solid particle concentration is related not only to the dimensionless radius but also to the axial location of corresponding section, it does not show the similarity distribution as reported in literature.