FULLY AUTOMATIC R O + D M PLANT 10,000 LPH
Demineralization process is used when the dissolved solids are to be almost completely removed from water. A two bed DM plant consists of a cation exchanger and anion exchanger. The cation exchanger contains strongly acidic cation exchanger resins in "H+" form. When filtered water is passed through the cation exchanger, the resin retains calcium, magnesium, and sodium ions and gives an equal number of hydrogen ions to the water.
R – H + + Ca 2+ =======> R Ca + H +
R – H + + Mg 2+ =======> R Mg + H +
R – H + + Na + =======> R Na + H +
When the resin is exhausted it is regenerated with hydrochloric acid or sulfuric acid. The reactions are:
R Ca + HCl =======> R – H + + CaCl2
R Mg + HCl =======> R – H + + MgCl2
R Na + HCl =======> R – H + + NaCl
Thus the water, which comes out of the cation exchanger is slightly acidic as the mineral salts are converted to respective mineral acids.
When water passes through cation exchanger the Alkalinity gets converted into carbonic acid. The reactions are as follows
R-H + NaHCO3 =======> R-Na + H2CO3
R-H + Ca (HCO3) 2 =======> R-Ca + H2CO3
R-H + Mg (HCO3) 2 =======> R-Na + H2CO3
The water coming out from the cation exchenger is acidic and it contains HCL corresponding to the Chlorides present in the raw water, H2SO4 corresponding sulphate in the raw water and carbonic acid corresponding to bicarbonate in the raw water. The carbonic acid is quite unstable and breaks into carbandioxide and water.
H2CO3 =======> H2O + CO2
This CO2 can be easily removed by means of degasser. In the degasser water flow in the downward direction through the bed of packed Rasching ring. Air is introduced in the bottom of the degasser and it passes through the bed and rasching ring in the upward direction. The rasching bed ensures intimate contact between the water and the air. The air scrub in the water is free of carbon dioxide escape from the top of the degasser along with the air.
The water from the degasser tower is collected in the Degasser Sump Tank. It is then transfer to the Strong Base Anion unit through a degasser transfer pump.
The anion exchanger contains strong base anion exchange resin in Hydroxyl (OH) form. In the anion exchanger the resin removes anions like chlorides, sulfates, bicarbonates, etc. and equal number of hydroxyl ions are given to water.
The reactions are as under
R – OH - + Cl - =======> R Cl + OH -
R – OH - + SO42- =======> R SO4 + OH -
R – OH - + HCO3- =======> R HCO3 + OH -
When the resin is exhausted it is regenerated with a dilute solution of sodium hydroxide. The reactions are as under :
R – Cl - + NaOH =======> R OH + NaCl
R – SO42- + NaOH =======> R OH + Na2SO4
R – HCO3- + NaOH =======> R OH + NaHCO3
The water from the anion exchanger is passed through a Cation Polisher Unit. It acts as a Polisher and give acidic water as per user requirement. The function of Cation Polisher is same as Strong Acid Cation Exchanger
Electrical conductivity is used for expressing the purity of de-mineralized water. Conductivity is proportional to the residual ionized solids in the water. Low conductance indicates water of high purity, and typical Cation polished de mineralized water has a conductivity of less than 5 mS / cm. All de-mineralizers are provided with a conductivity meter for measuring the conductivity thereby indicating the purity of the treated water