Minimum spouting velocity and segregation behaviour of binary mixtures of particles differing in size have been studied. The experiments were carried out in a bed of 20 cm diameter at superficial gas velocities up to 1.3 Ums by use of silica sand of four different particle sizes from 0.655 to 2.23 mm.
An empirical equation was proposed for the minimum spouting velocity of binary mixtures. The effects of the particle size difference and the superficial gas velocity on segregation were investigated. Results showed that considerable radial segregation as well as axial segregation occurred even for high gas velocity under the condition of large particle size difference.
Radial distribution of particle velocities, solids circulation rate and radial variation in bed voidage in a jet‐spouted bed were investigated in a 0.2 m diameter conical‐cylindrical column. The upward particle velocity is strongly dependent on gas velocity and its radial profile is the Gaussian. The solids circulation rates are of the same order of magnitude as those in a conventional spouted bed and are proportional to the gas velocity. Estimation of the variation in bed voidage in the radial direction revealed that the annulus voidage of about 0.90 was greater than the spout voidage of around 0.70. This tendency is contrary to that in a conventional spouted bed.
Coal gasification has been studied for the production of synthesis gas by use of a laboratory‐scale, two‐stage, jet‐spouted bed reactor. Tests were conducted in the dry ash mode with oxygen‐steam mixtures. The effects of operating conditions on the gasification performance were investigated at atmospheric pressure and temperatures up to 1150°C. Carbon conversions of 75% to 97% and cold gas thermal efficiencies of 62 to 78% were obtained for Taiheiyo coal. Both the carbon conversion and thermal efficiency were mainly affected by the oxygen/coal ratio. The product gases contained 36‐41% hydrogen and 30‐43% carbon monoxide.
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