Pneumatic conveyors can be used to transport dispersed solids over great distances in pipelines.
The solid is transported out of a feed tank via a vibrating trough into an airflow. An interchangeable injector disperses the solid in the airflow. The airflow transports the solid upwards in the tube. The transport terminates in a collector tank.
Depending on the velocity and solid content of the airflow, different transport states may occur. At high velocities, the solid is dispersed evenly across the cross-section of the tube (dilute phase transport). If the velocity is reduced, strands and balls form on the wall of the tube which then slide down owing to their higher settling velocity. The strands and balls disintegrate again in the airflow and reform. Reducing the velocity to below the settling velocity of the individual particles ultimately results in plug transport. The different transport states can be observed through the transparent tube.
To identify the pressure loss and the flow velocity, measuring points are provided at all relevant positions. The velocity of the airflow is adjusted by a pressure regulator. The solid mass flow can be adjusted by way of the throw of the vibrating trough on a potentiometer. The compressed air has to be provided from the laboratory supply.
Peas or plastic granulate are recommended for use as the solid.
The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.
Learning Objectives / Experiments
- learning the fundamental principle and method of
operation of a pneumatic conveyor system - observation of different transport states dependent
on solid content and air velocity - determination of the suspension velocity of the
solid - determination of the solid content of the flow - pressure loss dependent on solid content and air
* Pneumatic pressure-lifting of solids in a vertical
tube1 * Transparent tubes and tanks to observe different
transport states1 * Practical experiments on a laboratory scale
 pneumatic pressure-lifting of solids in a vertical tube  feed of solid into airflow via vibrating trough with adjustable throw  4 interchangeable injectors to disperse the feed material into the airflow  vertical tube made of glass  collector and feed tanks made of transparent material (PMMA)  collector and feed tanks interconnected by tube with plug valve  precision pressure regulator to adjust input pressure and flow rate  measuring points for pressure loss, temperature and flow velocity