Waltron 9072, User Manual

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Waltron User Manual 101-054-A.1
9072 Hydrazine Analyzer
INTRODUCTION
1
INTRODUCTION
1.1 AREAS OF APPLICATION
The Waltron 9072 Hydrazine Analyzer is used for the automatic, continuous
measurement and control of hydrazine concentration in aqueous solutions. Examples of
the applications of the unit include the determination of residual hydrazine concentration
in boiler feedwater in power plants, the monitoring of hydrazine concentration in the
primary loop of a nuclear power plant, the monitoring of hydrazine concentration during,
or the indication of the hydrazine concentration during the reduction of oxygen in water
treatment plants etc.
Hydrazine is used as a reducing agent and oxygen scavenger in fossil fueled boiler
systems, generally in AVT (All Volatile Treatment) process streams. The hydrazine
creates a reducing environment to protect copper containing metallurgy and serves to
reduce the dissolved oxygen concentrations to protect iron containing metallurgy.
Hydrazine concentration needs to be continuously monitored to provide feedback to the
chemical injection systems and to ensure that the correct concentrations are present in the
system.
In the primary loop of a nuclear power plant the hydrazine should reduce or mitigate the
oxygen which is produced by radiolysis. As a result the electro-chemical corrosion
potential (ECP) of the tube material is reduced. In nuclear power plant applications,
hydrazine is added to scavenge oxygen or recombine with the oxygen that is produce by
radiolysis. In the pressurized water reactor (PWR) primary loop, hydrazine is measured
in the range 25-50cc/kg. Hydrazine in boiling water reactors (BWR) feedwater and
reactor coolant is measured in ppm’s. Hydrazine in feedwater is typically 0-2ppm and
hydrazine in reactor coolant water will vary between 0.1-0.5ppm.
For boilers that operate with a pressure higher than 62 bar (900 psi), hydrazine is often dosed
to scavenge oxygen. Hydrazine (N
2
H
4
) reacts with oxygen as follows:
N
2
H
4 +
O
2
=> H
2
O + N
2