Case Study
Russian Power Plant Reduces Cooling
Water Operating Costs by about $120,000
Introduction
Copper and its alloys are widely used in industries because of their good resistance to corrosion, good mechanical strength and high thermal conductivity.
Admiralty Brass is the most widely used alloy for heat
transfer equipment fabrication, especially in petrochemical industry and power plants.
Even though copper and copper alloys have good
corrosion resistance such alloys are not immune from
corrosion. Within cooling water systems, the corrosion
resistance of copper is affected by high concentrations of chloride, sulphate, sulfide and nitrate ions together with pH, oxygen and free chlorine. In
uninhibited fresh water systems the typical copper
corrosion rate could be up to 1 – 2 mpy (0.025 – 0.05
mm/year) while during chlorination the corrosion rate
could be even higher.
Within power plants waterside corrosion of yellow
metal surface condensers will compromise condenser
integrity. However, this is not the only problem caused
by corrosion. The large surface area of power plant
condensers, even with low corrosion rates, could result in the release of significant quantities of toxic
copper corrosion products into the environment.
Faced with discharge limits for copper, power plants
have a strong desire to control corrosion and minimize copper discharge.
One of the techniques for reducing corrosion is to
make the alloy more corrosion resistant by alloying
with tin, lead or chromium. However the most common method is to apply corrosion inhibitors.
Challenge
The Togliatti VAZ is gas fired power plant located in
Samara region, Russia. The power plant provides
power, heating and hot water to the Volga automo-
tive plant and nearby city. With its 1,172 MW electrical power and 4,539 MW thermal power the
plant is considered to be the largest enterprise for
the Samara grid.
The plant comprises 14 boilers and 11 turbines
and associated surface condensers which are
constructed from admiralty brass. Two open
evaporative cooling systems provide the cooling
to the steam condensers and auxiliary equipment.
The systems comprise of 4 and 3 hyperbolic, natural draft cooling towers respectively. The makeup
for both cooling systems is raw water which is
taken directly from the Volga River. Blowdown
from the cooling systems is discharged back to
the river.
Historically the cooling systems were untreated
which resulted in high copper corrosion rates. In
view of the number of condensers, and the large
copper surface area, exposed to corrosion attack,
the plant had to operate the cooling systems at
low cycles of concentration in order to reduce the
discharge penalty caused by the high copper concentrations within the effluent.
Solution
One of the techniques for reducing corrosion is
the use of corrosion inhibitors. The effectiveness of
the corrosion inhibitor varies with the type of corrosion inhibitor, applied concentration together
with the surface properties of the alloy and the
corrosivity of the cooling water. Traditionally azoles have been used for yellow metal corrosion
inhibition. They protect the metallurgy by adsorbing onto the metal surface and forming a very thin
inhibitor film between the metal surface and the
corrosive cooling water.
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To reduce the copper corrosion rates GE recommended the introduction of Inhibitor AZ8101 together
with the following monitoring program to prove the
effectiveness of the cooling water treatment upgrade:

Copper corrosion monitoring by the use of preweighed copper test pieces.

Copper analysis within the recirculating water.

Residual azole monitoring.

Program execution based on results.
The plant improvements provided by GE through
the introduction of Inhibitor AZ8101 can be summarized as follows:

There was about 20 fold reduction in the Admiralty brass corrosion rates from 0.02
mm/year to 0.001 mm/year.

The introduction of Inhibitor AZ8101 has resulted in a reduction in the copper levels being
discharged to the environment.

With the enhanced system protection and the
associated reduction in copper levels, the
power plant was able to increase the cooling
water cycles of concentration from 1.6 to 2.22.5 thereby reducing the amount of blowdown
into the river.

By reducing the make-up water consumption,
admiralty brass corrosion rates and effluent
discharge costs the power plant has saved
approximately $120,000 per year, including
the cost of the Inhibitor AZ8101.
Results
Due to the high copper corrosion rate the plant had to
keep cooling tower operating cycles low in order to
comply with the regulatory copper discharge limits,
within the blowdown water. The application of Inhibitor AZ8101 started in middle of 2011. Admiralty Brass
corrosion rates before the treatment was on average
of about 0.02 mm/year. Within a few months of starting to apply the Inhibitor AZ8101, the admiralty brass
corrosion rate had stabilized around 0.001 mm/year,
as shown on chart below.
This significant reduction in the copper corrosion rate
resulted in lower copper levels within the blowdown
effluent, which allowed the power plant to increase
the cooling tower operating cycles.
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Case Study