The raw grain entering the gravity destoner should be fully screened and air-selected to avoid adverse effects on the stone removal effect.

If the raw grain contains a lot of impurities, large impurities will influence the normal material feeding and make the material layer uneven; small impurities will easily block the mesh holes, making the classification difficult; light impurities are easily causing dust flowing into air.

These impurities are not only not beneficial to production, but also seriously affect the stone removal effect, so the gravity destoner is better arranged after the precleaning and screening.