A cylindrical spout-fluid bed(182 mm inner diameter) equipped with a 80 mm inner diameter draft tube and loaded with urea particles(2.2 mm average particle size) was used to study gas bypassing fraction of spouting gas.The effects of spout nozzle diameter

draft tube length

bed height

entrainment height

spouting velocity and fluidizing velocity on gas bypassing fraction of spouting gas were investigated. The results showed that with increasing spouting velocity

gas bypassing fraction increased first and decreased later.Gas bypassing fraction increased with increasing entrainment height

but decreased slightly with increasing static bed height.When spout nozzle diameter was less than 50 mm

gas bypassing fraction increased with increasing nozzle diameter

but remained unchanged when nozzle diameter was greater than 50 mm.When spouting velocity was low

gas bypassing fraction increased with increasing draft tube length.The introduction of a small amount of fluidizing gas could effectively suppress gas bypassing.