OPERATION REGIMES OF FLUIDIZED-BEDS

The state of the art has been reviewed in the analysis and description of flow or contacting pattern in gas-solid contacting units where a g as flows upwards through a bed of solids. The flow regime or contactin g mode varies widely, depending on the particle size, particle density , gas density, gas viscosity, gas velocity and column geometry. The in fluence of such variables is reflected in the particle classification schemes and regime diagrams to cover the operation regions of common g as-solid reactors and contactors. In general, fluidized beds can be op erated in six different regimes: particulate (homogeneous) fluidizatio n, bubbling fluidization, slugging fluidization, turbulent fluidizatio n, fast fluidization and pneumatic conveying. The bubbling beds can be Further classified into three different modes of contacting: fast bub ble regime, slow bubble regime and rapidly growing bubble regime. Char acteristic features of all the regimes as well as the transitions betw een them are discussed. Current research interests, supported by pract ical needs, are oriented toward the operation conditions and contactor geometry of high velocity units.