... 30%-50% 4.supplier of sinopec and petrochina 20/40 high grade proppant sand Intertek Refractories Co., Gongyi City, founded in ... . The company has strong technical force and advanced production testing equipment, has a production plant of 40,000 square meters, 8 rotary kiln ... than 50 existing types of technical personnel, has developed a high-density, medium density, low density and many other series of ...