降低饲料级磷酸氢钙中砷含量的研究

Study on reducing arsenic content of feed-grade calcium hydrophosphate(DCP)

HG2636—2000标准实施后,饲料级磷酸氢钙产品的砷质量分数指标从0.004%降至0.003%。产品的砷质量分数随原料过磷酸钙水溶性砷质量分数的增加而增加,而过磷酸钙的砷来自于磷矿粉。磷矿粉的砷质量分数高于50μg/g时,需经过脱除砷才能使产品合格。受生产工艺限制,采用硫化法脱除砷。试验证实,在萃取液中加入不同量的硫化钠溶液,搅拌均匀后静置不同的时间,能达到不同的除砷率,而且不会影响脱氟,不会增加磷损。生产中需根据砷的质量分数来确定硫化钠的用量及静置时间。

Mter the implemention of Standard HG2636-2000, the mass fraction index of feed - grade DCP products has dropped to 0.003% from 0. 004%. The product＇s mass fraction increases with the rise of soluble arsenic＇s mass fraction in the raw material - calcium superphosphate, but the arsenic in calcium superphosphate comes from ground phosphate rock. The arsenic must be removed,when the arsenic＇s mass fraction in ground phosphate rock is higher than 50 μg/g. The sulfurizing method must be adopted due to the restriction of production process. Tests proved that： arsenic is separated differently by putting different quantity sodium sulfide liquid and different static settlement time after stirring evenly,and it is not affecting defluorination, not reducing phosphorus pentoxide content. The dosage of sodium sulfide and static settlement time should be determined according to arsenic＇s mass fraction during the production.