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Bulk solids can be transformed from a fixed bed into a fluidised bed when liquids or gases pass through them. The areas of application of fluidised beds include the drying of solids and a wide variety of chemical processes.
CE 220 features two transparent test tanks for fluidised bed formation in water and air. A diaphragm pump delivers water from a storage tank into the bottom of the left side test tank. The water flows upwards through a porous sintered-metal plate. On the sintered-metal plate is a bulk solid. If the velocity of the water is less than the so-called fluidisation velocity, the flow merely passes through the fixed bed. At higher velocities the bed is loosened to such an extent that individual solid particles are suspended by the fluid. If the velocity is increased further, particles are carried out of the fluidised bed. A filter at the top of the test tank holds these particles back. The water flows back into the storage tank.
The right-side test tank is similar in construction to the left-side one. An air flow generated by a compressor flows through it.
Manometers are mounted on both test tanks to measure the pressure loss. The flow rates are adjusted by way of valves, and can be read from flow meters. The test tanks are removable. This makes it easy to change the bulk solid filling.
Glass-shot beads in a range of particle sizes are provided as the bulk solid filling.
The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.
Learning Objectives / Experiments
- fundamentals of the fluidisation of bulk solids
- observation and comparison of the fluidisation process in water and air
- pressure loss dependent on flow velocity
- pressure loss dependent on the type and particle size of the bulk solid
- determination of the fluidisation velocity and comparison with theoretically calculated values (Ergun equation)
- dependency of the height of the fluidised bed on the flow velocity
- verification of Carman-Kozeny equation