Abstract:wet-process phosphoric acid has been widely used in the production of downstream food phosphoric acid and ammonium phosphate. The raffinate acid and ammoniated slurry produced in the production process of these two products need to be purified and removed by means of sedimentation. In this paper, the sedimentation characteristics of guar gum modified settling agent on raffinate acid and ammoniated slurry of wet process phosphoric acid downstream slurry were studied. The sedimentation effect of guar gum modified settling agent and conventional polyacrylamide was investigated. The results show that two kinds of guar gum modified settling agents are needed to achieve raffinate acid sedimentation, the optimal dosage is 300 g/t and 10 g/t, and the optimal dispersion time is 70 s and 150 s, respectively. A single guar gum modified settling agent can achieve the sedimentation of the ammoniated slurry. The optimal dosage is 8 g/t, the best sedimentation temperature is 70 ℃, and the best dispersion time is 60 s.