At present, most mineral processing plant back to sand ratio control between 300-500, the better. Potassium Sulphate,Potassium Sulfate,Potassium Sulphate Fertilizer,Soluble Sop Potassium Sulfate Hebei Woldi Trading Co.,LTD , https://www.woldigroup.comWhen the grinding machine and the classifier are enough to work in a closed circuit, the coarse product returned from the classification to the grinding machine is called returning sand. The weight of the return sand and the original amount of the ore miner are called the return sand ratio.