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Secondary Brine Purification
Sulfate Removal

Secondary Brine Purification

Mercury electrolysis or diaphragm electrolysis method were used for manufacturing caustic soda and chlorine in the past, however, recently it has been converted into ion exchange membrane method in Japan due to pollution control, saving the energy and keeping high quality.
If there contains much hardness in the brine, it is deposited in the membrane and causes the fall in electric efficiency and the increase of the power consumption. This is the reason why the ion exchange membrane method requests high quality of brine.

Only Ca and Mg are noticed as the impurities in the past, however, Sr is also recognized as the impurity as pointed out by some membrane manufacturer and then requested to reduce to the same level as Ca, Mg. Our brine purification plant removes Ca, Mg and Sr to the desired level from the brine which contains small amount of alkaline-earth metal after primary purification process

< Typical plant>
Operating method : Automatic controlled
Chelating resin tower : Number 2 sets
      Dimension 1,900 mm 3,300mmH
      Resin CR11 4.3
Operating condition : Flow rate 100 /h
      Service time 24 h/d
      Regeneration time 6 h/d
      Treatment Two towers merry-go-round
Annual production   80,000 tons/year

< System configuration >

Generally alternate service run by two towers is adopted for the operation of the secondary brine purification plant. This is the most optimum way with respects to the stability of the effluent quality and saving the resin volume for initial charge.
Three tower system can also delivered at your option, while many customers use two tower system. KCl solution can also be purified by the same system as used for NaCl purification.

< Operation result >

Feed brine  
NaCl 300 - 315 g/l
Free chlorine ND
Ionic Ca + Mg2 12 mg/l as Ca
Ionic Sr < 2.5 mg/l as Sr
Heavy metal < 0.2 mg/l
Fe < 0.5 mg/l
Ba < 0.5 mg/l
Suspended solids < 1.0 mg/l
PH 8.5 - 9.5
Temperature 55 - 65 degree C

Ca + Mg < 20 g/l
Sr < 50 g/l

< Property of CR11 >

Color & shape White, Beads
Type & function group Porous, Iminodiacetate
Shipping form Na
Shipping density 730 g/l
Moisture content 55 - 65 %
Cu adsorption capacity > 0.5 m-mol/ml
Ca BTC > 0.35 meq/ml
Screen grading 1,180 - 355m
( < 355m ... < 2% )
Effective size 0.4 - 0.6 mm
Uniformity < 1.6

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