Gravity Destoner is a kind of use of material and impurity density, suspension speed of different, with the help of mechanical wind, sieve to a certain trajectory to do back-and-forth movement, impurities from the material separated from the miscellaneous equipment, it is an indispensable key equipment in the flour processing process. In the flour processing process, the raw grain impurities less materials, in the clean-up stage, the use of a stone-de-stone process can be, for the raw grain contains impurities more complex situation, it is recommended to use two de-stone process.