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Sulfate Removal

< Preface >

The cationic impurity such as Ca, Mg and Sr can be removed by the secondary brine purification plant at the ion exchange membrane method of caustic soda and chlorine producing process.
Regarding the removal of anionic impurities such as sulfate and chlorate, physical-chemical separation method by adding barium salt or the drainage method of the concentrated impurities along with the brine have been adopted to keep the allowable level and prevent the membrane damage in the past.
Both methods affect the environment, the former causes mud problem of barium sulfate and the latter wastes the resources of salt.
The chlorate generated in the electrolysis cell as by-product causes the fall of caustic soda quality.
Our system using amphoteric ion exchange resin gives economical solution for this problem. The sulfate and the chlorate can be removed at the same time by passing the brine and water ( softened or demineralized water ) as the eluent through the resin bed.

< Location of sulfate removal system >

< Typical plant >

Operation method Automatic controlled
Separation tower Number 1 set
Dimension 1,800 mm x 4,200 mmH
Resin DSR01 5.45 m3
Operating condition Flow rate 21.8 m3/h
  Service run 23 h/d
  Backwash 1 h/d
  No of cycles 115 c/d
Na2SO4 removal 1,300 kg/d

< Simple flow scheme >

The operation can be executed by passing the diet brine and the water alternately through the separation resin bed. Softened or demineralized water is used as the eluent water to prevent the resin from fouling by the hydroxide, if there contains the hardness in the water.
As the separation principle is chromatographic technology, the resin bed is kept at high temperature to achieve highly separation efficiency at about 60 degree C which is maximum allowable temperature of the resin. The salt fraction in the effluent is recovered and the sulfate and chlorate fraction is discharged by using conductivity meter at the outlet of the
resin tower. All the operation is done automatically.

< Typical separation profile >

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