Abstract: The saline wastewater of coal chemical industry contains a large amount of inorganic salt ions.For saline wastewater,the discharge will cause environmental pollution,while the treatment and recovery cost is relatively high.In this paper,saline wastewater of coal chemical industry was used as a coagulant for coal slurry as the inorganic salt ions in the saline wastewater were similar to the effective ionic components of the coagulant.The influence of saline dosage on the sedimentation characteristics of coal slurry was discussed with non-stick coal sample from Inner Mongolia.The stability of coal slurry was analyzed by a turbiscan lab.The changes of the coal particle size were measured by a laser particle size analyzer.The effects of saline dosage on the sedimentation effect and supernatant turbidity were studied with polyacrylamide as a flocculant.The results show that the coal slurry system is relatively stable when no saline wastewater is added and the turbiscan ability index(TSI)has no obvious change.With the increase of saline dosage at 0-62.5 kg/t,the coal particles begin to agglomerate,and the TSI value increases significantly.The TSI at the top area of the coal slurry reaches a maximum value when saline dosage is 50.0 kg/t,then the TSI value begins to decrease when saline dosage is further added.Simultaneously,the zeta potential of the coal slime surface increases rapidly and then tends to be steady with the increase of saline dosage,indicating that the cations in the saline have an effect on compressing electric double layer and reducing the surface potential.The results of particle size analysis show that the D_(50)and D_(90)of the coal slime particles is 9.43μm and 45.57μm separately without adding saline wastewater.And these two values increase to 11.92μm and 63.77μm,separately,when 12.5 kg/t saline dosage is added,demonstrating that the addition of saline wastewater promot the coagulation among particles.The results of slurry water sedimentation test are basically consistent with TSI,and the settling rate of the coal slurry gradually accelerates with the increase of saline dosage.When the saline dosage is 50 kg/t,the settling rate reaches the maximum value and the supernatant turbidity reaches the minimum value.The results show that the saline wastewater can effectively promote the coagulation of coal slime particles and improve the sedimentation effect of difficult-to-settle slurry water.Therefore,saline wastewater from coal chemical industry can be considered to use as a coagulant for coal slurry in order to reduce the treatment cost of saline wastewater and improve the sedimentation effect of coal slurry.However,the influences of saline wastewater on the separation index,product performance and equipment life in the whole coal preparation process system need further study.