Pneumatic conveying is a term used in the transport of bulk goods .
This means the transport of bulk goods with gas (mostly air) using positive or negative pressure. The principle of conveyance takes place through pipes or hoses . The conveyance via fluid channels (square pipes with loosening bottom) is also widespread.
A distinction is made between flight, strand and plug conveyance. Flow conveying is also possible for suitable bulk goods.
When conveying by air, the gas speed is so high (mostly over 20 m / s, based on the empty pipe) that the bulk material is blown or sucked through the conveying line while it is floating. The loading, d. H. the ratio of conveyed goods to conveyed gas is less than 15 kg / kg. The contact with the pipe wall is so intense, especially in deflections, that wear and grain breakage occur.
The strand conveyance takes place at gas speeds of around 15-20 m / s. Part of the material to be conveyed slides over the bottom of the pipe as a strand and is driven by the particles flying over it. The load is in the range of 20–40 kg / kg.
In the case of plug conveyance, the conveying line is filled with material to such an extent that one or more material plugs are pushed through the line by the conveying gas. Higher pressures are necessary here. Loads of up to 100 kg / kg or more are possible. The gas velocities are in the range of about 3–10 m / s and are very much dependent on the material being conveyed.
The gas-solid mixture behaves like a continuum when conveying a flow. Highest loads of up to 300 or 400 kg / kg are possible. The gas velocities are around 7-15 m / s. Most bulk goods, especially those with a wide range of grain sizes, can only be conveyed effectively at low speeds with additional devices on the pipelines (e.g. pressure measuring points, injection valves, etc.).
In addition to the transport of solids, there is also the application area of pneumatic waste water pumping .
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