Humidity / Moisture Control is a critical element for various forms of powders such as fine salt, detergents, flour, powdery foods, calcium phosphate, baking powder, wheat starch, plastics resin etc. Pneumatic conveying as a means of powder conveying system is widely used in many powder processing operations such as in handling transfer of food powders, flour in a mill, bakery or confectionery.
The powder is thus always in movement and it may cause obstruction in free flow when contacted by moisture. Generally, every material has an affinity to absorb moisture when contacted by moist air and release moisture when the surrounding air is dry.
Due to the stickiness nature of the hygroscopic powders, they get stuck into nozzles, conveying belts and mixing machines leading to increased maintenance time and bad hygiene.
The level of moisture absorbing affinity differs in case of various hygroscopic ingredients as they are more sensitive. The absorption of moisture causes many hygroscopic ingredients to stick and cluster together.
In order to retain quality of powdery foods, they need to be dried at low temperatures.
| Applications |
Temperature (°C) |
Humidity (% RH) |
| Instant Coffee Processing |
26 |
25 |
| Flour |
24 |
10 |
| Starch |
24 |
20 |
| Gelatin |
24 |
10-30 |
| Milk Powder Storage |
21-36 |
15-30 |
| Confectionary-Chocolate Covering |
21-32 |
45 |
| Coffee Packaging |
18 |
40 |
| Dry Spice Conveying |
<48 |
12-16 Gr/Lb |
Moisture content of chemical powders / tablets is the most important factor controlling the flow properties of conveying process. Chemical powders and tablets are transferred to packaging via high velocity air streams or pneumatic conveying.
Majority of chemical powders are hygroscopic in nature which makes them stick on the surface and ultimately leads to cluster formation. This leads to the clustering and clogging of the powder feed to the tableting press and to high speed two piece capsule filling machines.
