Innovative dry screening
For a raw coal preparation plant in Baotou in Inner Mongolia/China JÖST GmbH & Co. KG, based in Dülmen/Germany, has supplied non-blinding screens for dry scalping with a total capacity of 1200 t/h (Fig.). On the one hand, this area is an arid region, and for this reason the available water reserves are limited. Every wet sizing process is therefore very complex and cost-intensive. On the other hand, the raw coal in Baotou comes with considerable refuse rock and loam content so that wet sizing screens are usually the preferred equipment.
The solution lies in water-saving, dry scalping with high acceleration. The customer’s first tests with extremely high acceleration on existing screens failed. On machines with screening areas larger than 30 m2, the screening surface was torn and the drive failed. Not even flip-flow screens were able to bring the desired success. JÖST’s solution has concentrated the necessary high acceleration on the screen deck with special rod grids. This protects the drive and screen box. Optimum screening efficiency is nevertheless permanently ensured. Intensive preliminary experiments impressed the customer. The actual machine body has been designed in the proven manner with the help of finite element analysis and is driven with the rugged JÖST exciters. Special screen deck cross beams clamp the different segments of the rod grid system.
Each of the two vibrating screens can be fed with up to 600 t/h raw coal. The smallest separation cut is currently 13 mm. The machines have an effective screening width of 4000 mm and a length of 8000 mm. Without the counter-vibration frame, they weigh 32 t per unit. These screens were part of a big order for several big screens for scalping and fine screening as well as for dewatering of the prepared coal and tailings.
