ppchem-05-2011-3

8/9/2019 ppchem-05-2011-3

1/8

8/9/2019 ppchem-05-2011-3

2/8263PowerPlant Chemistry 2011, 13(5)

PPCHEM

chemistry. All drum units in the sys-

tem have a mixed metallurgy feed-

water heater system and no con-

densate polishing. The cycle

guidelines are listed in Table 1.

These operating parameters have

served the system well. The peri-

ods between chemical cleanings of

the boilers have averaged ten

years or better over the last 20

years. The cleaning solvents used

are either diammonium or tetra-

ammonium ethylenediaminetetra-

acetic acid (EDTA) depending on

whether the boiler is natural or

forced circulation. No extensive

layup techniques were used on theunits during scheduled or forced

maintenance outages because

outage and down time was kept to

a minimum. Because of chronic

reheater tube failures due to out-

of-service corrosion suffered by all

the units, dry air blower systems

were installed on the reheater sec-

tions on all units. Unit unavailability

from boiler tube leaks averaged approximately 5 %, and a

majority of these failures were from corrosion fatigue.

CHANGING OPERATING CONDITIONS

With the slowdown in the economy, electric generation

needs reduced. In 2009 a majority of the drum units in the

FirstEnergy system were placed on an economic reserve

condition. That is, the units were shut down but needed to

be available within a 72 h timeframe for operational dis-

patch. 72 h were needed because many of the plant staff

were assigned elsewhere in the company (normally to the

Transmission and Distribution Departments) while the

units were not operating. To assure that the units were

ready for operation, boiler or feedwater systems were notdrained. In addition, boiler pressure checks were per-

formed to assure that during the shutdown and subse-

quent cool-down of the unit corrosion fatigue cracks did-

n't occur or could be immediately repaired. After the first

week of unit shutdown and subsequent leak checks, a

nitrogen blanket was applied to the drum.

The requirements of economic reserve along with the

boiler leak checks made cycle protection very difficult to

obtain. Corrosion in a unit cycle is most easily shown by

the 'corrosion triangle' (Figure 1).

Corrosion occurs when all three elements are allowed to

come together, much in the same way as in the firefight-

ers' fire prevention triangle. When any one of the con-

tributing elements is removed from the situation, corrosion

cannot occur. There are two basic ways this may be

accomplished in an electric utility boiler. The first is to dry

out all components. Once water, or moisture, is removed

from the system, corrosion is stopped, hence the reason-

ing for the installation of dry air blowers on the reheat sec-

tions of the boiler. The second option is to remove all the

air, or oxygen, in the system. This is accomplished by

evacuating all the air from an area and replacing it with

nitrogen.

Boiler Parameters

pH 9.1 to 9.6

Specific conductivity [S cm1] 5 to 20

Cation conductivity [S cm

1

] < 10Silica [mg L1] < 0.2 (pressure dependent)

Feedwater Parameters

pH

Specific conductivity [S cm1] 1.6 4.0

Cation conductivity [S cm1] < 0.2

Sodium [g L1] < 3

Dissolved oxygen [g L1]< 20 at the condensate pump discharge

< 5 at the economizer inlet

ORP [mV] 200 350Hot Reheat Steam

Sodium [g L1] < 3

Cation conductivity [S cm1] < 0.2

Table 1:

Cycle chemistry guidelines.

Water Oxygen

Exposed metal

Figure 1:

Corrosion triangle.

An Alternative Chemistry for Both Operational and Layup Protection of High-Pressure Steam-Water Cycles

8/9/2019 ppchem-05-2011-3

3/8

8/9/2019 ppchem-05-2011-3

4/8

An Alternative Chemistry for Both Operational and Layup Protection of High-Pressure Steam-Water Cycles PPCHEM

PowerPlant Chemistry 2011, 13(5) 265

Case History I

The Eastlake #2 unit is a 124 bar, 130 MW forced circula-

tion Combustion Engineering boiler with a GE turbo-gen-

erator located in Eastlake, Ohio, on the shore of Lake Erie.

This unit had spent various amounts of time throughout

2009 in an economic reserve condition ranging from one

week to two months. During the off-line periods the unit

was available at all times to restart. Analyses for iron were

conducted by grab sampling in an effort to understand

when the greatest amount of corrosion was occurring and

if our current efforts in unit layup were satisfactory. This

grab sampling and iron analysis was also conducted on

the other units with similar results. Sampling was con-

ducted at the condensate pump discharge, low-pressure

(LP) heater outlet (deaerator inlet), economizer inlet, boiler,

and hot reheat. Figures 68 show the typical iron results

that were observed.

EPRI best practice for iron corrosion transport [3] is

2 g L1 maximum at the economizer inlet. At steady

state loads, the Eastlake units were able to maintain below

5 g L1 maintaining the guideline limits given in Table 1.

Iron corrosion throughout the cycle was at its maximum

during transient load and startup conditions. More trou-

bling were the iron concentrations at the hot reheat point.

Dry air had been used on this section for the last several

years when the unit came off line. Although

there were no large spikes in iron as seen on

the feedwater section, it was obvious therewas corrosion in the hot reheat.

Anodamine was injected into the conden-

sate pump discharge of the Eastlake #2 unit

on March 30, 2010. The injection rate was set

for approximately 350 g L1 and as pre-

dicted cycle cation conductivity increased.

Within 24 hours the amine formulation was

throughout the cycle and all chemistry control

parameters were being met and maintained

with the exception of the cycle cation conduc-

tivity. The cycle cation conductivity had

increased by 0.17 S cm1 from the back-

ground normal 0.18 S cm1 to approximately

H O2

Cathode

(O being the most common)2

Anode (Fe)

2H O + 2e2

2OH + H2

Fe 2+Fe + 2e Fe O2 3 Fe O3 4, (FeO Fe O ) 2 33+Hematite, Fe 2+Magnetite, Fe

Figure 5:

Protection triangle.

350

300

250

200

150

100

50

0

1

TotalIron

[g

kg

]

Unit off line

Sampled during

load increase

Startup

Condensate pump discharge

LP heater outlet

Economizer inlet

Sampled during

load increase

Time [d]

1 2 3 4 5 6 7

Figure 6:

Feedwater iron analyses.

140

120

100

80

60

40

20

0

1

TotalIron

[g

kg

]

Unit off line

Time [d]

1 2 3 4 5 6 7

Figure 7:

Boiler iron analyses.

80

60

40

20

0

1

TotalIron

[g

kg

]

Unit off line

Time [d]

1 2 3 4 5 6 7

Figure 8:

Hot reheat iron analyses.

8/9/2019 ppchem-05-2011-3

5/8266 PowerPlant Chemistry 2011, 13(5)

PPCHEM An Alternative Chemistry for Both Operational and Layup Protection of High-Pressure Steam-Water Cycles

0.35 S cm1. The unit was scheduled for a

shutdown over the weekend two days later,

which gave an excellent chance to determine if

corrosion rates had been reduced during this

short injection period. Sampling commenced

immediately after the unit was placed back inservice with amine injection. The unit was

again taken off line because of a tube failure.

Amine injection continued at a rate of approxi-

mately 350 g L1. The results of the grab

sampling are shown in Figure 9.

The addition of the proprietary amine formula-

tion to Eastlake #2 continued until November

30, 2010. Transient and startup iron corrosion

analyses continued; long-term results are

shown in Figure 10. Analyses of organics were

also made during this period with the resultsgiven in Table 2. As expected, the organic acid

levels throughout the cycle had increased,

accounting for the increase in the cycle cation

conductivities.

All iron data was averaged to determine the

numerical reduction in iron transport and is

shown in Table 3. These averages are derived

from grab sampling; the majority of the sam-

ples were taken during transient loading con-

ditions.

Iron results given in the graphs and tables are

total iron concentrations, that is, the combina-

tion of Fe2+ and Fe3+ analyzed by way of the

ferrozine method. While reductions in total

iron are seen in the data, it is very interesting

to note these reductions include significantly

lower Fe2+ ( 2 g L1) and copper oxides

(highest 1 g L1). A direct reaction occurs

between iron and reducing water to form solu-

ble species and hydroxides. When iron cor-

rodes in an aqueous solution, both oxidation

and reduction occur at the anode and cathode

respectively. At the anode, an oxidationprocess occurs [6]:

Fe Fe2+ + 2e (1)

2H2O + 2e 2OH + H2 (2)

Reduction of Fe2+ concentrations is seen as the metal sur-

face (anode) is protected by the filming amine. Validation

of this protection was also demonstrated on Eastlake #2

when the amine feed was interrupted for a one-week

period several months into the testing period, resulting in

both corrosion product oxides once again increasing out

of specification (iron increased to 15 g L1 and copper to

11 g L1). Note that during the Anodamine chemical

injection period and once again after reinstallation of

dosage following the interruption in feed, during base load

and during transient load situations both copper and iron

were measured as equal to and/or lower than control lim-

its (iron) or below detectable limits (copper).

With any proposed change in operation, management

needs to understand immediate pay back. Listing num-

bers and showing graphs may not generate interest if real

dollar savings are not shown. Unfortunately, reductions in

corrosion transport may not correlate directly to reduc-

tions in corrosion fatigue failures for quite some time.

Pitting damage from past corrosive conditions remains

within the tubes and residual stresses will continue to

cause cracking [7]. Savings can be found elsewhere.

200

180

160

140

120

100

80

60

40

20

0

1

TotalIron

[g

kg

]

Date [mm/dd/yyyy]

03/31/2010

04/02/2010

04/04/2010

04/06/2010

04/08/2010

04/10/2010

04/12/2010

04/14/2010

04/16/2010

04/18/2010

04/20/2010

04/22/2010

04/24/2010

04/26/2010

Off-reserve Off-FO

LP heater discharge

Hotwell pump discharge

Economizer inlet

Boiler

Hot reheat

Morning ramp-upRamp-up in load

(startup)

Figure 9:Subsequent startups and transient load sampling after addition of proprietary

amine formulation.

FO forced outage

350

300

250

200

150

100

50

0

1

T

otalIron

[g

kg

]

Condensate pump discharge

LP heater outlet

Economizer inlet

Date [mm/dd/yyyy]

02/17/2010

02/24/2010

03/03/2010

03/10/2010

03/17/2010

03/24/2010

03/31/2010

04/07/2010

04/14/2010

04/21/2010

04/28/2010

05/05/2010

05/12/2010

05/19/2010

05/26/2010

06/02/2010

06/09/2010

06/16/2010

06/23/2010

06/30/2010

Anodamine injection

Normalchemistry

parameters

Figure 10:

Results of iron sampling before and after addition of proprietary amine

formulation.

8/9/2019 ppchem-05-2011-3


PPCHEMAn Alternative Chemistry for Both Operational and Layup Protection of High-Pressure Steam-Water Cycles

Assuming that corrosion product oxide release and trans-

port from the economizer inlet are responsible for all the

deposit buildup within the boiler, the approximate

34 g L1 iron calculates to 95 kg of iron being trans-

ported to the boiler. A chemical cleaning on this particular

unit occurs approximately every ten years with 950 kg of

iron (Fe3O4) removed. Hence, the iron corrosion product

oxide transport rate measured at the economizer is very

closely verified by previous chemical cleaning history on

the boiler. Using the averaged iron maximum corrosion

product rate of 6.7 g L1 now measured, this equates to

18 kg iron transported. Using the same cleaning criteria of

approximately 950 kg removed, a chemical cleaning

would be required every 50 years for this particular boiler.

I leave it to the reader to calculate the money and

improved availability/generation saved from reducing out-

age, in addition to the time, costs and environmental limi-

tations required to complete necessary boiler cleanings.

Case History II

Anodamine has been used on four other drum units as a

preservation method when the unit is taken off line.

Approximately 72 hours before a known unit shutdown,the amine is injected at a rate of approximately 300

500 g L1 and applied until the

unit is removed from service. As

with the Eastlake #2 experience, all

unit cycle cation conductivities

increased from approximately 0.2

to 0.4 S cm1. Initial injectionsvaried in success however. Several

of the units' cycle cation conduc-

tivity values increased dramatically

to nearly 1.0 S cm1 even though

amine injection rates were kept at

300 g L1. Unfortunately no sam-

ples were obtained during these

high cation conductivity periods. In

subsequent injections of the

amine, however, the cation con-

ductivity values did not increase to

the originally seen high values(~ 1.0 S cm1). This phenomenon

seems to depend upon the boiler cleanliness and last

chemical cleaning. 'Clean' unit boilers do not see unusu-

ally high cation conductivities (an approximately

0.2 S cm1 increase over ambient values due to organic

acid production). 'Dirty' boilers, or those with higher mag-

netite deposition loading, seem to experience a higher

cycle cation conductivity increase (an approximately 0.4

to 1.0 S cm1 increase) for several days. After the initial

amine injection and several days of operation with the

chemical, the cycle cation conductivity values decrease to

the approximate 0.2 S cm1increase over ambient val-

ues. Acetate levels in all units are comparable to those

listed in Table 2. Figures 11 and 12 show visual inspec-

tions of the condenser and a superheater tube during a

unit outage. Similar results were found after the unit was

idle for two months. Notice the hydrophobic characteris-

tics and that the water droplets do not touch the metal

surfaces.

Case History III

FirstEnergy management was concerned about the

increased cycle cation conductivities and acetate concen-

tration levels. These measurements were clearly outsiderecommended turbine manufacturers guidelines [3,9,10].

Before Anodamine Use Anodamine Injection

Feedwater and steam BDL 40 60 g L1 acetate

Boiler BDL 0.2 0.3 mg L1 acetate

Table 2:Average boiler and cycle acetate concentrations. Detection limit = 0.03 mg L1.

BDL below the detection limit

Condensate LP Heater Econ Boiler Hot

Pump Out Inlet Reheat

Previous chemistry 21.8 47.9 34.4 23.8 17.5

Anodamine use 8.5 7.9 6.7 9.9 7.4

Table 3:

Total average iron corrosion levels before and after amine use. All data is stated in g L1 Fe.

Figure 11:

Condenser

door.

Figure 12:

Superheater

tube.

8/9/2019 ppchem-05-2011-3

7/8268 PowerPlant Chemistry 2011, 13(5)

PPCHEM An Alternative Chemistry for Both Operational and Layup Protection of High-Pressure Steam-Water Cycles

The supplier R & D proposed a

newly developed formulation,

Anodamine HPFG, a fully water-

soluble, non-toxic, cyclohexyl-

amine-free thermally stable amine

formulation designed to continueexisting levels of metal protection

throughout the entire steam-water

cycle but to effectively eliminate

cation conductivity increases.

On November 30, 2010 the

Anodamine HPFG solution was

introduced into the Eastlake #2

and #3 condensate pump dis-

charges. As discussed, unit #2 had

been on a constant feed of the

original formulation while the #3unit had been subjected to injec-

tions only 72 hours before a

scheduled unit shutdown. After an

initial increase in the cycle cation

conductivity on Eastlake #3, the

cycle cation conductivity de-

creased during steady amine injec-

tion until the unit was taken off line

for a scheduled economic reserve

off (see Figure 13). Eastlake #2 has

been injected continually with the

new amine formulation to date at a

rate of 300350 g L1. Econo-

mizer inlet cation conductivity data

for that unit is given in Figure 14.

Increases in the economizer inlet

cation conductivity are normally

seen during a drop in unit load

(feedwater flow) or during a unit

startup. Analysis of the cycle

waters revealed organic acids,

acetate, etc. to be BDL (below

detection limits). Inspections of the

condenser have given the same

positive visual evidence of metalhydrophobic characteristics and water beading as with

the previous amine formulation as discussed and shown

under case history II (see Figure 11).

CONCLUSION AND FURTHER STUDY

Apart from the ever important cycle treatment require-

ments of ongoing system protection, stability of oxides,

lowering of iron transport, preventing or limiting of FAC,

and protection of both ferrous and admiralty alloys in

mixed metallurgy systems, there is also a simultaneous

occurrence of moisture and oxygen during unit off condi-

tions causing corrosion within the cycle. Traditional miti-

gation strategies include dry layup of the system, which

requires the use of nitrogen. Capital investment of bulk

storage and piping systems needs to be undertaken to

adequately protect the cycle if this path is chosen [11,12].

In addition, the safety aspects of using nitrogen should

never be minimized and include asphyxiation (> 18 % oxy-

gen is fatal), compressed gas dangers, and freeze poten-

tial. The other traditional option is wet layup. This option

includes increasing the feedwater ORP with a reducing

chemical [11] (hydrazine) in mixed metallurgy feedwater

heater systems, which can lead to FAC. Wet layup also

requires capital investment of deoxygenation equipment

or, at the very least, techniques to deoxygenate makeup

water to the unit as the recommended guidance for dis-

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

1

Conductivity[S

cm

]

11/30/2010,

09:00

11/30/2010,

12:00

11/30/2010,

15:00

11/30/2010,

18:00

11/30/2010,

21:00

12/01/2010,

00:00

12/01/2010,

03:00

12/01/2010,

06:00

12/01/2010,

09:00

12/01/2010,

12:00

12/01/2010,

15:00

12/01/2010,

18:00

12/01/2010,

21:00

Unit off line

Injection of Anodamine HPFG

Date [mm/dd/yyyy, h:min]

Figure 13:

Eastlake #3 economizer inlet cation conductivity during injection of the new amine

formulation.

1

Cond

uctivity[S

cm

]

11/30/2010

12/02/2010

12/05/2010

12/12/2010

12/19/2010

12/26/2010

01/02/2011

01/09/2011

01/16/2011

01/23/2011

01/30/2011

02/02/2011

02/04/2011

02/06/2011

02/13/2011

02/20/2011

Unit off line



Unit off

Unit off

Date [mm/dd/yyyy]

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

Figure 14:

Eastlake #2 economizer inlet cation conductivity during Anodamine HPFG injection.

8/9/2019 ppchem-05-2011-3


PPCHEMAn Alternative Chemistry for Both Operational and Layup Protection of High-Pressure Steam-Water Cycles

solved oxygen in the boiler is < 100 g L1 before firing

[11]. In addition, the feedwater system piping and other

susceptible piping throughout the cycle is prone to FAC if

all chemistry conditions are not at optimal levels. These

non-optimal conditions also occur during normal unit

operation.

The use of filming amine technology to protect out-of-ser-

vice metal surfaces would eliminate the use of nitrogen

and other traditional deoxygenation techniques for metal

protection along with the costs and safety concerns asso-

ciated with it. Utility equipment would be ready for imme-

diate operation while also being protected from corrosive

conditions. An excellent balance of unit protection and

unit availability would be achieved. A one-year monitoring

period that included continuous operation with a film-

forming amine, Anodamine, along with use for layup

protection in multiple units has shown that this type ofchemical control program can protect both iron and cop-

per systems even when exposed to oxidizing all-volatile

treatment and ammonia cycle conditions. Testing of this

program also indicates a significant reduction in Fe2+, an

indication of protection against FAC. Introduction of the

filming amine chemistry in all units did not cause corrosion

product increases or any other unwanted side affects.

Recent positive testing of the water-soluble Anodamine

HPFG product showed thermal stability throughout the

entire steam-water cycle. This grade was able to keep

cycle cation conductivity values equal to previous condi-

tions, below and in compliance with turbine manufacturer

guidelines of 0.2 S cm1 (not degassed cation conduc-

tivity) and showed no appreciable levels of organic degra-

dation products like carbon dioxide, acetate/formate, etc.

FirstEnergy has entered into a tailored collaboration (TC)

project with EPRI and several other U.S. utilities to further

test the use of this proprietary amine formulation and its

effectiveness for cycle preservation.

REFERENCES

[1] Interim Consensus Guidelines on Fossil Plant Cycle

Chemistry, 1986. Electric Power Research Institute,

Palo Alto, CA, U.S.A., CS-4629.

[2] Cycle Chemistry Guidelines for Fossil Plants: Phos-

phate Treatment for Drum Units, 1994. Electric

Power Research Institute, Palo Alto, CA, U.S.A., TR-

103665.

[3] Cycle Chemistry Guidelines for Fossil Plants: Phos-

phate Continuum & Caustic Treatment, 2004. Electric

Power Research Institute, Palo Alto, CA, U.S.A.,

1004188.

[4] Deoxygenation in Cycling Fossil Plants, 1992. Elec-

tric Power Research Institute, Palo Alto, CA, U.S.A.,

TR-100181.

[5] Flow-Accelerated Corrosion in Power Plants, 1998.

Electric Power Research Institute, Palo Alto, CA,

U.S.A., TR-106611-R1.

[6] Guidelines for Controlling Flow-Accelerated Corro-

sion in Fossil and Combined Cycle Plants, 2005.

Electric Power Research Institute, Palo Alto, CA,U.S.A., 1008082.

[7] Verib, G. J., Conversion of a Drum Boiler from

Phosphate to Caustic Treatment. Eighth International

Conference on Cycle Chemistry, 2006, Calgary,

Canada.

[8] Dooley, B., McNaughton, W., Boiler Tube Failures:

Theory and Practice Volume 2: Water-Touched

Tubes, 2007. Electric Power Research Institute, Palo

Alto, CA, U.S.A., 1012757.

[9] Steam Purity Requirements for Turbine Operation,

Alstom Power, HTGD 90 486 V0001F.

[10] Steam Purity Recommendations for Utility Steam

Turbines, 2004. General Electric Company, GEK

72281c.

[11] Cycling, Startup, Shutdown, and Layup Fossil Plant

Cycle Chemistry Guidelines for Operators and

Chemists, 2009. Electric Power Research Institute,

Palo Alto, CA, U.S.A., 1015657.

[12] Cycle Chemistry Guidelines for Startup, Shutdown,

and Layup of Combined Cycle Units with Heat

Recovery Steam Generators, 2009. Electric Power

Research Institute, Palo Alto, CA, U.S.A., 1015657.

THE AUTHOR

George J. Verib (B.E., Chemical Engineering, Cleveland

State University, Cleveland, OH, U.S.A.) is the cycle chem-

istry consultant at the FirstEnergy Corp. He has held vari-

ous positions in fossil-fired plant laboratories and corpo-

rate laboratories for over 32 years and now serves as the

company water quality consultant. George Verib has

authored 15 papers on various aspects of makeup water

production, condensate polishing, and boiler water treat-

ment. He is a registered professional engineer in Ohio

(U.S.A.) and a recipient of the EPRI Innovators Award for

oxygenated water treatment in once-through boilers and

of the Technical Transfer Award for caustic treatment

chemistry in subcritical drum boilers.

CONTACT

George J. Verib

76 South Main Street

Akron, Ohio 44308

U.S.A.

E-mail: [email protected]

Documents

ppchem-05-2011-3