Flow regime study in a circulating fluidized bed riser with an abrupt exit: Fully developed flow in CFB riser

Abstract

Flow regime study was conducted in a 0.3 m diameter, 15.5 m height circulating fluidized bed (CFB) riser with an abrupt exit at the National Energy Technology Laboratory of the U. S. Department of Energy. Solids fraction and particle velocity data for both the high and low density suspension in the riser were analyzed to investigate how the gas-solids flow could reach a fully developed condition in the riser. A fully developed condition in the riser is defined by Parssinen and Zhu (2001a) as: The radial solids distribution in the riser no longer changes with its axial location. Results of the data analysis are discussed in the following sections. Radial solid fraction and particle velocity data generated from the optical fiber probe (the Vector probe) for the 200 micron glass beads during the test series were used to examine the solids flow development in the riser. The test series was a statistical designed factorial experiment included four (4) operating set points and a duplicated center point (therefore a total of 6 operating set points). The riser gas velocity for this RPB test series is to be operated above the upper transport velocity. The operating conditions for the five experiments were riser gas velocity, Ug=5.6 m/s, 6.5 m/s, and 7.7 m/s and solid mass flux, Gs=87 kg/m2 • s, 194 kg/m2 • s, and 303 kg/m2 •s. The conditions for the duplicated center point were Ug=6.5 m/s, and Gs=194 kg/m2·s. However, only the results obtained for the higher solids flux, Gs=303 kg/m2 •s and riser gas velocity, Ug=5.6 and 7.6 m/s are presented in this paper.