The factory originally used a three-stage flat ring machine with diameter of 2000. For the production line with an hourly output of 20 tons, the whiteness of raw ore slurry is less than 17 ℃ and the iron content is about 0.9% before entering pinghuan. After three-stage pinghuan iron removal, the whiteness is between 38-42 ℃ and the iron content is about 0.3%. The product quality is not up to standard. Later, four KJLSL-500GG high gradient magnetic sepeartor of our company were added, with an hourly output of more than 20 tons, iron content ≤ 0.05%, and whiteness above 65 ℃.