Method of removal of permanent hardness

For this purpose the ion exchangers are used. Cation bed of about 1 m3 and similar size of anion bed is used here. In these beds brown colored globular resins zeolite is used. Upper and lower parts are perforated caps of 2m high and 0.5m Dia. Water about 6 m3/hr at 3 bar is allowed to flow first through cations and the through anions are removed and at the anion side all the positive ions are removed and at the anionic side all the negative ions are removed. There will be one active and one stand by ion exchangers.

Before entering the boilersthe O2 dissolved should be removed. To reduce the percentage of dissolved oxygen, sudgard solution of less than10% concentration is used to scavenge the dissolved O2. The actual composition of sudgard solution is 1:6 or 1 volume of surged and 6 volume of water. It is a brownish solution. A piston pump is adjusted to get 1 l/hr. Sudgard isNalco 1700

When the amount of absorbed ions increase, the analyzer shows the conductivity/pH value has been increased. This shows the less efficiency in anionic exchangers. The process by which the efficiency of anionic beds increases through certain sequence is called Regeneration. Actually it is a fleshing process. The materials used in regeneration are NaOH in anionic bed and HCl in cationic bed.

Sequence of Regeneration

100 ml of HCl is passed through the cation bed, at the same time; 100 ml of caustic soda (liquid) is passed through the anion bed for ½an hour. Then water is flown for 2 hrs. These acid, base and water are given up as waste.

H+Cl-+Ca+ CaCl2

MgCl2

NaOH NaS2, NaCl

After finishing the regeneration process pH value should equal to 7. For this purpose we use Nalco -1742 a type of NaOH.

Pumps:

Centrifugal pumps are used to pump water. There would be one active and another standby pumps.

Boilers:

There are two types of boilers.

1. Fire tube boilers:(Thermax)

In these types of boilers, burner gas will be inside the tube, and water outside the tube in a drum. About 10, 20 tons/hr of boilers are there. The feed water is pre heated up to 80-900. The dissolved oxygen is scavenged using sudgard (Nalco-1700).

2.Water tube boilers:

Water inside the tube and gas in the drum.

pH value

pH value = -log[H3O+]

The concentration of neutral water,

[H2O] = [H3O+][OH-]