In the production process of automobiles, there is one indispensable molding material, that is, coated sand. It is needed for the casting and molding of brake discs, frames, engines and other parts of automobiles. Waste sand after casting and molding contains a variety of pollutants, which will cause environmental pollution if not properly disposed of. Recently, the reporter came to Chongqing Yangtze River modeling materials (clique) Co., Ltd. (Abbreviated as "Changjiang Materials"), to visit th