We visited a customer to help them optimise their granulation process. They operate a feeco pin mixer and disc with a diesel fired rotary dryer. The material is powdered lime.
The biggest problem they had is that the seed being fed into the pan was too dry. The pan appeared to be making good pellets but they were all breaking down into dust in the dryer. Insufficient moisture within the pellet can lead to rapid breakdown in a dryer where temperatures are typically circa 350c. There are many variables that affect granulation but you need to ensure you get the basics right.
1st. Feed material must have a suitable particle size. Too coarse and it simply won't knit together to form a pellet. Too fine and it requires extra water, binder and time to agglomerate. A typical feed material would usually be between 50-450 micron.
2nd. The dry powder must be conditioned with water and binder before transfer to drum or disc pelletiser. This is usually the point at which you add powdered or liquid binder. We normally form a damp microseed which is minus 500micron. A pin mixer or eirich is suitable.
3rd. With a damp microseed conveyed into the disc the pellets will form rapidly. Additional water can added via water jets in the pan to help control the size of granules. Fine sprays are better and give a more consistant product. Coarse water sprays usually make too much oversize and can wet the back of the pan leading to uncontrollable build up.
4th. If you have managed to get the moisture and binder contents correct the pellets should survive the drying process. There are many critical factors that will affect how the pellets behave during the curing process. To name a few-
Temperature.
Dryer rpm
Lifter design
Dryer angle
Airflow
Burner position. Ie at the feed end or exit end.
Staffs powder processing helps companies to prove the viability of granulating their materials. We have a fully kitted out pilot plant with lab scale eirichs and discs. Once we have decided on a design mix we scale up to produce several hundred kg of finished product for initial testing. If this proves successful we have the ability to produce larger quantities of pellets on our full size production plants.
Visit our website for contact details.
www.staffspowderprocessing.com
