When powdered bulk materials like flour, sugar, salt or calcium carbonate or others need to be transported efficiently from A to B, a variety of pneumatic conveying systems can be used, dependent on which powder material is handled, what distance has to be covered and what throughput has to be achieved. Further it has to be considered whether the powder material to be pneumatically conveyed is already a mixed product.
In general, there are two different philosophies in terms of pneumatic conveying systems, such as vacuum vacuum conveying systems or pressure conveying systems. Depending on the bulk material handling task, both solutions have their advantages and benefits. For more details of vacuum conveying systems and pressure conveying systems, please go to our microsite.
In principal several different pneumatic conveying methods can be distinguished: Dilute phase pneumatic conveying, semi dense-phase pneumatic conveying, dense phase pneumatic conveying and impulse phase or plug flow pneumatic conveying.
Bulk materials can be conveyed either in batches or continuously. Very small batches could even consist of a single bulk material plug. But normally we are talking about batch handling, respectively discontinuous pneumatic conveying, when filling any kind of receiving volume has to be interrupted in a certain time interval to allow the discharge. This receiving volume could be for example a vacuum receiver with a butterfly valve at the bottom.
On the other hand on large production scales we may convey continuously without interrupting the bulk material conveying. To achieve continuous pneumatic conveying we will use dosing screws or rotary valves at feeding or discharge points.
Depending on the air velocity, the bulk materials physical properties, the thermodynamic condition of the air, and the mass ratio solids to air an observer may see different flow patterns. All these flow patterns can be separated in two major condition of operation, suspension mode and non-suspension mode.
To the suspension mode we count the dilute phase conveying. Suspension means single particles are completely floating in the air or the selected conveying gas, e.g. nitrogen for explosive products.
Please see below a simulation of a bulk material dilute phase pneumatic conveying.
Please see below a dense phase conveying of bulk materials as an example in the non-suspension mode