Precipitated silica Drying: Equipment Selection

Precipitated silica is a typical light powder and three quarters of the selection is aerodynamics. Its bulk density is low, so a given weight occupies a volume more like flour, and pneumatic conveying is sensitive to both velocity and duct size: too slow and it will not move, too fast and the bed disperses and the dust collection load rises with it. So the first question at selection is whether the air volume range of the system can carry this powder steadily. The second characteristic is that it lifts very easily, so closed conveying and a high extraction grade are needed, or after a few months the workshop is covered in white powder. Our configuration is a flash airflow line: the material is carried the whole way inside a closed duct and never drops to the floor.

Precipitated silica is a typical light powder and three quarters of the selection is aerodynamics. Its bulk density is low, so a given weight occupies a volume more like flour, and pneumatic conveying is sensitive to both velocity and duct size: too slow and it will not move, too fast and the bed disperses and the dust collection load rises with it. So the first question at selection is whether the air volume range of the system can carry this powder steadily. The second characteristic is that it lifts very easily, so closed conveying and a high extraction grade are needed, or after a few months the workshop is covered in white powder and the maintenance load on the casing, the bearings and the instruments climbs visibly. Our configuration is a flash airflow line: the material is carried the whole way inside a closed duct and never drops to the floor, so the dust problem is solved structurally rather than operationally. The rotary drum is the alternative for larger throughput where the air volume cannot carry the powder stably, with the flights replacing pneumatic conveying. Silica does not absorb moisture, does not cake and is not particularly heat sensitive, which means its selection rests almost entirely on the conveying end.

What should be asked first when selecting for precipitated silica?
The air volume range. Whether the ducting can carry this powder steadily is the first question. Too slow and it will not move, too fast and the bed disperses and the dust collection load rises with it. Until that is settled, temperature and throughput are not worth discussing.

How is the dust around the machine controlled?
At the level of structure rather than by sweeping. The material is carried the whole way inside a closed duct and never drops to the floor, so the dust problem does not arise in the first place. Workshop extraction still has to be specified at a high grade, or the casing, the bearings and the instruments pick up a maintenance load that shows up after a few months.

What if the airflow line runs out of air volume at high throughput?
Move to a rotary drum, where the flights replace pneumatic conveying. The drum does not depend on duct air volume, at the cost of a larger footprint and higher capital. Which one applies depends on the headroom left in the air volume and the investment budget.