Introduction; Description; Ion-Exchange; Ion Exchange Column Construction - ABB 2155 User Manual

Cation Exchange Column
2155

1 Introduction

1.1 Description

The measurement of contaminants by using ion exchange
columns has been established in the power industry for many
years.
Alkaline chemicals such as Ammonia and Sodium Hydroxide are
added routinely to the feed and boiler water to control corrosion
by increasing the pH. The effect of this is a significant increase
the conductivity of the water, thereby masking the conductivity
of any contaminants.
To counter this increased conductivity, a sample is passed
through the ion exchange column where the alkali is removed.
After the sample has passed through the ion exchange column,
the conductivity of the contaminants can be measured
accurately. For example, corrosive anion contaminants such as
chloride, carbonate and sulphate can be found.
Other similar systems include a conductivity measurement
before the column in order to calculate the levels of pH and
Ammonia.

1.2 Ion-Exchange

Ion exchange is the process where ions incorporated within a
solid material (the ion exchange resin) are exchanged with ions
in a solution. This can be used to purify or remove unwanted
chemicals from the solution.
The resin has the appearance of smooth spherical beads usually
between 0.5 and 1 mm (0.02 and 0.04 in.) in diameter. However,
at the molecular level each bead has a skeleton-like structure
that presents a large surface area to the solution. Feed water is
passed through the clear acrylic column containing the resin
beads.
Before use, the resin is pre-treated with a Hydrochloric acid
solution to condition the resin into its hydrogen form. When put
into service the resin exchanges these hydrogen ions with
cations (positive ions) from the solution forming acid equivalents
of the salts. For example:
Ammonia
NH OH + RH <--> RNH + H
4 4
Sodium Chloride
RH + NaCl <--> RNa + HCl
The above sodium reaction results in a three-fold increase in
conductivity, therefore smaller levels of contaminants can be
detected.

1.3 Ion Exchange Column Construction

The 2155 Cation Exchange Column is supplied as a single
acrylic column with quick-release couplings end fittings and a
resin pack.
Note. The connecting tubes and mounting clips are not
supplied.
2
O
2
Flow Guage
(optional)
Isolation/Flow
Regulation
Valve
Sample Inlet
Mounting Clip
End Cap
Quick-release
Coupling
Fig. 1.1 Typical Cation Column Arrangement
1 Introduction
Quick-release
Coupling
End Cap
Mounting Clip
Cation Column
Stainless Steel
Conductivity
Cell
Sample
Outlet
IM/2155 Rev. G