2002
Issue: 2002, 4(1), 5-11
Title: Study of the Electrochemical Properties of Liquid Films
Formed on Turbine Stages
Author(s): Oleg A. Povarov Tamara
I. Petrova Valeri N. Semenov Valeri I. Kashinski Alexander N. Troitskii Andrei
Yu. PetrovR. Barry Dooley
Abstracts: Loss of efficiency and corrosion failures of blades
and disks of turbine stages operating in the phase transition region persist as
one of the important problem areas in the utility industry. In recent years many
countries have been dealing with this problem, but so far electrochemistry
phenomena occurring Inside the turbines have been poorly studied. The
oxidation-reduction potential is one of the basic parameters which control the
conditions for the formation of protective films on the surface of construction
materials; the metal po- tential may be used to estimate the occurrence of
corrosion processes. The conductivity of the early liquid films formed on metal
surfaces of the turbine flow path is one of the factors which largely influence
the rate of electrochemical corrosion. Previous tests have shown that liquid
films generated on the surface of the turbine now path may contain large amounts
of corrosive impurities. This problem is also related to recent EPRI research
aimed at modifying the moisture condensation process and improving unit
efficiency and capacity.The paper presents the results of a study on the
oxidation reduction potential, metal potential, and conductivity of liquid
films performed under an EPRI research program at the Mos cow Power Institute.
Issue: 2002, 4(1). 13-17
Title: Measurement of the Con ductivity of Liquid Films in the
Turbine Flow Path
Author(s): Valeri N. Semenov Alexander
N. Troitskii Roman V. Agapov Konstantin 0. PovarovR. Barry Dooley
Abstracts: This paper describes a new technique of liquid film
conduc- tivity measurement on the surfaces of the turbine flow path. In
addition, it contains the results of a study on the effect of dif- ferent
chemistries with controlled addition of impurities on the liquid film
conductivity on the turbine surface and a study on the dependence of the
conductivity level in liquid films on the initial wetness of steam at the Inlet
on the test channel. The information presented is based on experimental results
pro- duced on a test turbine with an attached test channel at theMoscow Power
Institute.
Issue: 2002, 4(1). 18-21
Title: Chemistry On-line Instru mentation - What Will Be the
Needs of the Power Plants of Tomorrow?
Author(s): Albert
Bursik
Abstracts: In the last decade, the power industry has undergone
im- portant changes. The most important changes have been privatization and/or
the breaking up of large state-owned utilities, deregulation of the power market
in many countries, the appearance of new independent power producers on the
power market, and the introduction of heat recovery steam generators and
combined cycles in the power industry. These changes markedly influence
conditions on what optimum power plant chemistry can be realized. The most
serious consequences for power plant chemistry are the reductions in staff and
the reduced willingness to spend money on a seemingly unproductive power plant
area - power plant chemistry. Under these conditions, it is very important to
take advantage of and to exhaust all the features of the modern chemistry
on-line instrumentation. Here, some deficiencies are clear, particularly
deficiencies in the communication between the respective instruments, the
central process control unit, and the remote users of the produced data. In
addition, many of the on-line instruments available on the market require
extensive calibration and validation.The contribution focuses on these aspects
and tries to spec ify the future needs of the power industry with respect to
thechemistry on-line instrumentation.
Issue: 2002, 4(1), 23-27
Title: Possibilities for Avoiding Deposits and Fouling in River
Water-Cooled Con densers and Heat Exchang ers
Author(s):
Walter Wied Christoph Randt
Abstracts: For the last 30 years or so, BASF
Al
Issue:
Title:
Author(s):
Abstracts: back flushing and filtration, with automatic
wedge-wire filters having proved very successful. Biofilms can be efficiently
countered with biocides. Even small concentrations are very effective, so that
the legally prescribed limits are readily andreliably observed.
Issue: 2002, 4(1). 31-33
Title: General Instructions for Unit Layup
Author(s):
Michael Rziha
Abstracts: These instructions summarize the most important
general layup actions. When applying these instructions. as a rule, the
individual plant-specific issues have to be considered. Im- portant aspects are,
e.g., the planned mode of operation and the type of readiness for startup. For
this reason, individual instructions have to be tailored to each individual
plant cycle.
Issue: 2002, 4(1). 34-38
Title: Deposits of Ammonium Chlo- ride at Heat Exchanger Tubes
of a Flue Gas Clean- ing System
Author(s): Martin Mineur
Manfred Rotermund
Abstracts: Deposits in flue gas apparatus and channels belong
to the everyday annoyances of many operator teams. In the sew- age sludge
combustion plant VERA in Hamburg (Germany) first intense investigations and
extensive experiments led to a valid explanation and to the solution of a
problem in the countercurrent heat exchanger of the flue gas cleaning sys-tern.
Issue: 2002, 4(2), 69-71
Title: A Tool for Cross-System Calculation of Water Chem- istry
Parameters in Power Plants
Author(s): Helmut Nopper
Wolfgang Metzner
Abstracts: The WaChem water chemistry analysis program was
devel- oped for the calculation of cross-system water chemistry pa- rameters in
power plants. The PC program has a graphical user interface for modeling a plant
heat flow diagram and performs an Iterative cycle calculation of water chemistry
parameters. The calculation results are presented graphically and can be output
in diagrams and tables. WaChem can be used to analyze the existing power plant
chemistry and to optimize it with case studies. The program can also be usedas a
knowledge base for on-line monitoring.
Issue: 2002, 4(2), 73-79
Title: Chemical Operation Experi- ence with the CCPP Cottam
Author(s):
Michael Rziha Bernd Senger Stephen Merry Alistair Greig
Abstracts: The heat recovery steam generator in the combined
cycle power plant Cottam is a new development in that it incorpo- rates both
drum type and once-through evaporators, the low pressure evaporator being a
conventional drum type and the Intermediate and high pressure evaporators having
a once- through configuration. Both once-through and drum boilers are fed from
the same condensate source. Flow through par- allel, vertical evaporator tubes
in this horizontal heat recovery steam generator is only upward, as in a
natural-circulation boiler with horizontal gas pass. In contrast to standard
once- through evaporators, a special fluid dynamics design results in a higher
mass flow rate in tubes with increased heat ab- sorption.This system requires
different chemistries to be applied to the LP and the HP/IP evaporator
water/steam circuits in order to minimize:• corrosion of the plant,• transport
of corrosion products around the water/steam cycle, and• deposition of
impurities within the water/steam cycle. Insufficient control of the water/steam
cycle chemistry can result in dissolution of metal from the tubes and can cause
them to weaken or fail. Several factors affect the process of corrosion in a
boiler system. These include the type of metal used for construction. the
dissolved gases and ions present in the water, and the temperature in the boiler
and tubes. A boiler can outlast the economic life of the plant if the water
chemistry and passivation are controlled to limit the type or corrosion to
general surface corrosion. Experience gained during the commissioning and
operating phase of the com- bined cycle power plant Cottam regarding cycle
chemistry isoutlined.
Issue: 2002, 4(2), 81-85
Title: Once-through Boiler as an Autoclave for Testing an
Organic Cycle Treatment Chemical
Author(s): Ladislav
Bursik
Abstracts: An early condensate sampler supplied by Alstom
Switzerland AG was employed to Investigate the early condensate pH and the
concentration of organic anions on Unit IV of the Munich South power station of
SWM Munich. A mixture con- taining a low-volatile film-forming polyamine and
volatile neu- tralizing and alkalizing amines was used for cycle chemistry
treatment.Despite the unavoidable partial decomposition of the testedchemical,
the pH of the early condensate Is more alkaline than the main unit condensate.
Issue: 2002, 4(2), 91-92
Title: Layup Prac1ice at ELSAM
Author(s):
Karol Daucik
Abstracts: This paper discusses the layup procedures for large
power utility units. As almost all large units al ELSAM are once- through boiler
units, the discussion is limited to these installa-tions.
Issue: 2002, 4(2), 93-97
Title: Pulse-Chlorination®, the Best Avallable Technique in
Macrofouling Mitigation Using Chlorine
Author(s): Harry J.
G. Polman Henk A. Jenner.
Abstracts: In 1998, KEMA developed a new chlorination method
called Pulse-Chlorination®. It enables optimal antifouling treatment with a
minimum use of chlorine. This technology is based on the principle that In
general mussels and clams have a re- covery period after exposure to
chlorination before opening fully and restarting filtration. The method takes
advantage of this recovery lime by using short successive periods of
chlorination, alternating with periods without chlorine. The tests undertaken
between 1998 and 2001 resulted in chlorine savings up to 50 % on a yearly basis,
compared to regimes applied in earlier years. Results on site after one year
with Pulse-Chlorination® show improved control of macrofouling and a better
overall performance of the cooling water system. This in turn allows longer
intervals between planned outages, thus spreading the running costs over three
years rather than two years. There are additional advantages for power plants
that use electrochlorinalion plants to produce hypochlorite. As the
Pulse-Chlorination® reduces the hypochlorite dosage up to 50 %, only part of the
installed equipment is used at any one time allowing maintenance of the unused
electrochlori- nation plants. Because less hypochlorite is dosed, there is a
reduction in chlorination by-products discharged and thusless environmental
impact.
Issue: 2002, 4(2), 101-102
Title: Reducing the Costs of Ultrapure Water Production - A
Case Study
Author(s): John Murrer Steve Latter
Abstracts: The 380 MW combined cycle gas turbine power station
In Peterborough changed its water supply from town mains to high purity reverse
osmosis permeate in October 2000. The high purity water is produced from
secondary treated sewage effluent using advanced membrane technology.Alpheus
Environmental and British Gas staff have recently completed a study on the power
station's demineralilation plant to identify the differences in operating costs
associated with the change in feedwater. The results show that the ul- trapure
water produced after the change to a high purity feed is of improved quality and
that the demineralization plant regeneration operating costs have been reduced
by over 90 %. The demineralization plant availability has increased from 78 to
98 % enabling almost 20 % more ultrapure water to be produced.The change in
feedwater has also improved the local envi- ronment by significantly reducing
the amount of waste chemi-cats discharged from the site.
Issue: 2002. 4(2), 103-105
Title: The Impact of Steam Con- denser Performance upon Power
Plant Efficiency
Author(s): Brad Buecker
Abstracts: Efficient operation of steam-generating plants is of
primary importance in these times of concern about environmental protection and
rising energy costs. A steam generator has many features that improve
efficiency, yet often they are taken for granted by plant personnel. These
include the steam reheater, regenerative feedwater heaters, and the condenser.
This article examines the basic thermodynamics of these systems, and illustrates
why they improve efficiency. The forecast growth In world population will
continue to in- crease electricity demand, which will require efficient
designand operation of power plants around the world.
Issue: 2002, 4(3), 133-137
Title: Radiation Exposure Man- agement Update December 2001
Author(s):
Howard Ocken Sean Bushart
Abstracts: Nuclear utilities are obligated to implement
technology to protect plant personnel from the adverse effects of ionizing
radiation. EPRl's Radiation Exposure Management Program supports two main
activities to address this issue: (i] radiation control technology reduces
shutdown radiation fields and (ii] radiation protection technology optimizes
worker safety and productivity. This paper summarizes recent EPRI successes,
which have helped U.S. nuclear utilities reach historic lowlevels of collective
exposure.
Issue: 2002,4(3), 139-146
Title: lnterfacial Behavior at Above-Ambient Tempera- tures of
Ionic and Non-IonicAqueous Solutions Important in Boiler Water Chemical
Conditioning
Author(s): Ian A. Mclure Andrei Yu. Petrov
Duncan H. Gordon Malcolm BallR. Barry Dooley
Abstracts: The reliability and efficiency losses in steam
turbines have been one of the major problems faced by the utility industry
worldwide. The size of droplets in the last low pressure stages of the turbine
is one of the most important factors affecting these losses. One method of
controlling the droplet sile might be by changing the surface tension in the
turbineenvironment.
Issue:
Title:
Author(s):
Abstracts: The paper presents results or EPRI sponsored
research on the surface tension of various substances which might be present in
or added to the power plant cycle as conditioning chemicals (inorganic salts,
ammonium and amine com pounds) and discusses whether they can exert a
significant effect on surface tension in amounts typical for power
plantoperation.
Issue: 2002, 4(3), 148-153
Title: Cold-End Corrosion in HRSGs
Author(s):
Frank Gabrielli Stephen Goodstine Thomas Mastronarde
Abstracts: Many of the processes for increasing the efficiency
of com- bined cycle plants can result In lower fiue gas temperatures exiting the
heat recovery steam generators and/or increased flue gas moisture content. These
conditions can as a conse- quence increase the potential for corrosion of the
low tem- perature gas-path components. The attack of these surfaces is generally
referred to as cold-end corrosion. There are vari- ous aspects and components of
cold-end corrosion, of which the most significant is dew point corrosion. The
paper dis- cusses these corrosion mechanisms of major significance to heat
recovery steam generators as well as presents resultsfrom field and laboratory
test programs.
Issue: 2002, 4(3), 157-161
Title: Avoiding HRSG-Tube Fail ures
Author(s):
Pierre J. Ploumen
Abstracts: Based on long-standing experience with the analysis
of boiler lube failures, KEMA has expertise in the aspects that are crucial to
avoiding tube failures. In particular, KEMA has gathered experience with heat
recovery steam generator tubes over a period of 25 years. The crucial aspects
concern the design of the boiler, the choice of design values, heat flux, and
the water treatment.An overview of failures in heat recovery steam generators in
the Netherlands Is presented, including an explanation of the cause of the
failure. Design aspects of heat recovery steam generators are also discussed,
especially the necessity of achieving an equal flue gas flow distribution and
water distri bution.Furthermore, the influence of an unequal flow distribution
on the tubes in a horizontal LP evaporator, resulting in increased heat flux,
changes in steam quality and void fractions are discussed. The results are based
on two-phase flow calcula tions of an LP evaporator with its own computer
programs.Guidelines for water treatment are given to avoid tube fail ures.
Issue: 2002, 4(3), 169-172
Title: Boiler Tube Failures in In dustrial Drum-Type Steam
Generators - Part 2: Boiler Water Treatment
Author(s):
Albert Bursik
Abstracts: Boiler tube failures in industrial drum-type steam
generators are very frequent. The root causes of the most serious boiler tube
failure mechanisms occurring in industrial boilers are related to plant cycle
chemistry. Unfortunately, the interna- tionally accepted fossil cycle chemistry
guidelines drawn up and published by VGB and EPRI do not reflect conditions
typical In Industrial steam generating Installations.Part 1 of this paper dealt
with the major differences between steam generation in utility boilers and in
industrial steam boil ers and other steam generating apparatus (e.g.,
differences in design, material selection, and cycle contaminants) and treated
some site-specific issues influencing cycle chemistry. The applicability of VGB
or EPRI feedwater guidelines was evaluated and discussed. This paper (Part 2 of
a planned 4- part publication) deals with the applicability of internationally
accepted boiler water treatments and with their influence onthe occurrence of
boiler tube failures.
Issue: 2002, 4(4), 197-208
Title: Prediction and Prevention of Stress Corrosion and Corro
sion Fatigue Cracking in LP Steam Turbines
Author(s):
Stuart R. Holdsworth
Abstracts: The current ability to predict and prevent s_tress
corrosion and corrosion fatigue cracking in LP steam turbines has devel- oped
from the knowledge base accumulated during the past 30 years from unilateral and
collaborative R&D activities, in particular in Europe, Japan and the US, and
from service experience. The two environmental cracking mechanisms are due to
the combined influences of (i) material condition, (ii) environment and (iii)
applied stress (static or cyclic). The influence of these factors on the
material parameters used to predict stress corrosion and corrosion fatigue
behavior is reviewed in the paper. The appropriate control of these fac- tors
and an understanding of the underlying damage mecha- nisms provide the basis for
preventing stress corrosion andcorrosion fatigue cracking in turbine components.
Issue: 2002, 4(4), 209-219
Title: Troubleshooting Turbine Steam Path Damage
Author(s):
Thomas Mccloskey
Abstracts: Steam path damage, particularly of rotating and
stationary blading. has long been recognized as a leading cause of steam turbine
unavailability for large fossil fuel plants world- wide. Turbine problems cost
the utility industry as much as one billion dollars per year. Failures of
blades, discs, and rotors in both fossil and nuclear steam turbines represent a
serious economic loss of availability and reliability for electric power
generation suppliers and other energy supplies world- wide. Turbine problems
such as deposition and erosion of blades can result in severe efficiency losses,
resulting in sig- nificant economic penalties. The primary objective of this
paper is to provide a methodology to identify the underlying damage or failure
mechanisms, determine the root cause, and choose immediate and long-term actions
to lessen orprevent recurrence of the problem.
Issue: 2002, 4(4), 221-228
Title: Operational Tube Failures in Heat Recovery Steam Gen
erators: Metallurgical and Water Chemistry Perspec tives
Author(s):
Kevin J. Shields Ewa Labuda
Abstracts: Operators of combined cycles with heat recovery
steam gen- erators are reporting an increasing extent of boiler tube fail- ures.
The most important failure mechanisms include flow- accelerated corrosion in low
pressure evaporators and under- deposit corrosion in high pressure evaporators.
Careful ex- amination of the failed tubes and the cycle chemistry applied is
essential for identifying the actual failure mechanism and for determining or
confirming the actual failure root cause.The failure appearance and other likely
microscopic and met allurgic features as well as the failure location help to
identify the possible failure mechanisms. Determining the root cause includes,
among other things, evaluation of possible envi ronmental factors (e.g.. cycle
chemistry in the case of water touched tubes).This paper describes the
troubleshooting procedure and ap proach applied in two tube failure cases, in
the low pressure evaporator of a dual pressure unit and in the high pressure
evaporators of two dual pressure units.
Issue: 2002, 4(4), 229-234
Title: Root Cause Failure Assess ment of Waterwall Tubing
Author(s):
Fred V. Ellis
Abstracts: An in-depth study of the waterwall tubing failures
at Unit 1 of the Newington Station was performed. The service related
damage/failure mechanisms were hydrogen damage, oxygen pitting, and corrosion
fatigue. The tubing failure history showed a significant increase in the failure
rate from ap- proximately four tube failures per year for the years prior to the
middle of 1991, to failure rates from approximately seven to twenty failures per
year for the years after the third quarter of 1993. The cycle chemistry data
analysis showed that the principal reason for the increased failure rate is
ingress of contaminants, primarily chlorides and oxygen. The chloride ingress
was due to both minor and major condenser leaks. The condenser problems are the
direct result of wiring the cathodic protection system in reverse polarity, the
significant corrosion activity due to this error, and the failure of remedial
measures (application of plastic coaling) to stop the leaks. The oxygen ingress
was attributed to possible leaks at the deaerator and unit layup procedures. The
stress ranking, environment parameter, and equivalent operating hours in-
formation were used in determining the probable root cause of failure for the
corrosion fatigue failures. For the locations with the higher stress ranks of B
and C (burner comers/at- tachments, buckstay and economizer door attachments),
the major root cause of failure influence is excessive stresses/ strains.
Corrective action requires redesign and modifications to alleviate the applied
stresses/strains. For the locations with the lowest stress rank of D, the major
root cause of failure is the environmental factors of poor water chemistry and
boiler layup. Corrective actions are to rehabilitate and/or replace the
condenser tubing, utilize the nitrogen blanket system during unit shutdown. and
to inspect the deaerator for possible leak paths and repair as required.
Issue: 2002, 4(4). 235-239
Title: Study of Flue Gas Emissions of Gas Microturbine-Based
CHP System
Author(s): Andrei Yu. Petrov Abdolreza
ZaltashD. Tom Rizy Solomon D. Labinov
Abstracts: The number of distributed energy resources such as
gas microturbines and combined cooling, heating and power systems has increased
markedly over the last several years. Environmental issues (i.e., emissions.
noise) are among the most important aspects of operating these systems. This
paper presents the results of an emissions study of the Com- bined Cooling,
Heating and Power Integration Test Facility(microturbine-based with heat
recovery) located at the ORNL.
Issue: 2002, 4(5), 261-265
Title: Recent Developments in PWR Zinc Injection
Author(s):
Howard Ocken Keith Fruzzetti Paul FrattiniChristopher J. Wood
Abstracts: This paper reviews the status of zinc injection In
PWRs. Initial field applications have been undertaken to mitigate degrada- tion
of Ni-base structural alloys by primary water stress cor- rosion cracking. The
first U.S. demonstration was at Farley 2 in 1994; zinc injection was later
initiated at Farley 1 and Diablo Canyon 1 and 2. Reactor water zinc levels are
in the 30-40 µg•kg-1 range, since laboratory results have shown that this
concentration is needed to mitigate primary waterstress corrosion cracking. Zinc
injection at low levels (- 5 µg •kg-I) has been started at three
Siemens-designedPWRs and at Palisades, where the aim is to lower shutdown
radiation fields.All U.S. PWRs injecting zinc have seen significant decreases in
shutdown dose rates. Available data suggests it is prema ture to conclude if
zinc mitigates primary water stress corro sion cracking.
Issue: 2000, 2(5), 269-276
Title: Overview of PWR Chemistry Options
Author(s):
Francis Nordmann Agnes Stutzmann Jean-Luc Bretelle
Abstracts: This paper describes the main options for the
primary and secondary water chemistry of PWRs. After having focused on corrosion
mitigation in the past. the options now emphasize cost saving, ease and
reliability of operation, low activities, and limitation wastes.For the primary
coolant, the main options concern ways to get the optimum pH (lithium increase
or enriched boric acid use), zinc addition, fuel axial offset anomaly
limitation, and the best shutdown procedure to save time and efficiently
eliminate radioactive elements.For the steam-water system, the main options
concern miti gation of Alloy 600 MA stress corrosion cracking of steam
generator tubing, flow-accelerated corrosion of carbon steel and the control of
steam generator fouling by selection of the most appropriate secondary water
treatment (pH, amine,hydrazine concentration, dispersant addition).
Issue: 2002, 4(5), 281-284
Title: Cation Conductivity and Power Plant Reliability: A 20-
Plant Survey
Author(s): Luis Carvalho Rosa Crovetto Gerry
W. Sauve Paul Sehl
Abstracts: The purity of steam and boiler feedwater is one of
the most important criteria for ensuring component availability and reliability
in power plants. Steam turbine manufacturers are tying Increasingly stringent
steam purity requirements to warranty clauses of their machinery. Cation
conductivity. with its many limitations, Is the most prominent control pa-
rameter for steam purity enforced by turbine manufacturers. Low molecular weight
aliphatic organic acids, carbon diox- ide, and Inorganic anions affect cation
conductivity. Ac- cording to the literature, specific corrosion effects of
organic acids are Inconclusive and deserve more research.Independent power
producers (IPP), unlike most utility gen- erating stations, operate with minimal
staff. IPP owners, in trying to comply with the lighter steam purity
requirements, incur higher capital and operating expenditures with sophis-
ticated water treatment equipment and more complex moni- toring instrumentation.
Additional on-site laboratory com- plexity and meaningful interpretation of all
the collected data also burden the typical high-efficiency IPP operation.This
paper reports on a survey of twenty operating plants (mostly power plants)
across Canada ranging in pressure from 6.2 to 19.65 MPa. The paper presents data
collected during the survey. Organic acid concentration, cation con- ductivity,
and selected inorganic anions showed no correla-tion to system reliability in
any of the plants surveyed.
Issue: 2002, 4(5), 285-289
Title: Thermal Scaling in the Context of Life Assessment and
Microstructural Degradation of Weldments Steels in Steam Generation Systems
Author(s):
R. K. Singh Raman
Abstracts: The paper discusses the estimation of remnant creep
life and determination of crack velocity using thickness of oxide scales that
are generally present on the in-service steam generating systems. The prevalence
of in-service failures in the welds of Cr-Mo ferritlc steels causes great
concern in steam generating/handling systems of power plants. This paper
discusses the non-uniform scaling behavior across microstructural gradients In
weldments of pressure vessel steels. The necessity for developing a global model
for life assessment by relating oxide scale thickness with the time- temperature
history of in-service welded components is also discussed. The paper also
presents evidence of steam corro- sion-assisted deterioration in microstructure
that can pro-foundly affect the creep life.
Issue: 2002, 4(5), 293-295
Title: Chemiluminescence Method for the Determination of Sub
µg •kg-1 Copper Concentra tions
Author(s): Andrei Yu.
Petrov Caibin Xiao Donald A. Palmer0. Whitney King
Abstracts: Copper deposition in high-pressure steam turbines
repre sents a significant source of performance and reliability loss to fossil
power plants with mixed-metallurgy feedwater sys tems. Provisions for reliable
and prompt monitoring of low concentrations of copper compounds at power plants
as specified by recent copper guidelines have become more crucial. This paper
presents the chemiluminescence method for the determination of low (µg• kg-1 and
sub-µg •kg-1) cop per concentrations and provides a comparison with ion
chromatography and graphite furnace atomic absorption.
Issue: 2002, 4(5), 297-299
Title: Use of Ion Chromatography for Measuring Ions In Water to
Protect the New Genera tion Gas-Fired, Combined Cycle Power Plants
Author(s):
Beverly Newton
Abstracts: The use of ion chromatography for monitoring
corrosive ions In water has been implemented at several new combined cycle, gas
fired power plants in the U.S. Due to stringent requirements for clean water to
prevent corrosion and plug ging of turbine components, this methodology Is
predicted to have a significant impact in extending useful operating life times
and to measurably increase the availability of compo nents in contact with
water. Ion chromatography, due to its ability to identify individual anion and
cation species, to achieve parts-per-trillion detection limits, and to operate
on line, has played a central role in the effectiveness of these water
chemistry monitoring programs. Ion chromatography has provided the capability to
distinguish between corrosive and non-corrosive ionic intrusions, identify and
eliminate sources of corrosive ingress, optimize and extend the lifetime of
demineralizer resins, measure hideout return, determine mass balances, and
maintain neutral anion-to-cation bal ances. Cost savings due to chemistry
monitoring programs using ion chromatography have been estimated to be in the
millions of dollars per year.This paper provides an overview of the applications
and justification (using case studies) for using ion chromatography for the
analysis of water In these new generation power plants.
Issue: 2002, 4(5), 301-303
Title: Major Reliability and Lubri cant Consumption Savings at
Tutuka Power Station
Author(s): Anton E. Cattaert
Abstracts: The proper selection and management of lubricants is
very important for both improvement of equipment reliability and reduction of
operating cost. The paper briefly describes ac tions undertaken as part of the
establishing and optimizing of a basic lubricant condition-monitoring program.
These efforts have resulted in considerable cost savings,
Issue: 2002,4(6), 320-327
Title: The Relationship between Cycle Chemistry and Per
formance of Fossil Plants
Author(s): Barry Dooley
Abstracts: Cycle chemistry influenced failures and performance
losses have increased recently on fossil plants worldwide. These directly affect
the overall performance and cost the industry enormous amounts of money in
availability loss and replace ment power. For instance, the number of hydrogen
damage incidences is at an all-time high, and the percentage of or ganizations
experiencing each of the major chemically influ enced boiler tube failures has
increased drastically since 1997. The paper analyzes this situation in a number
of ways. Firstly, the case is made that cycle chemistry is the major business in
a fossil plant, and to be successful an organiza tion needs to address the
performance gaps associated with day-to-day operation. as well as the
introduction of new tech nology and new ways of doing business. Secondly, a
bench marking process is introduced that has been applied to around 100 fossil
plant organizations/plants/units. Deeper analysis of the areas "behind" the
benchmarks illustrates how organizations need to link together all aspects of
cycle chemistry around the plant, and that dealing with only one or two Items Is
not sufficient and will lead to an increasing num ber of chemically influenced
activities. Finally, analysis of all the results from this large number of
organizations/ units/plants leads to an Indication of the most reliable chem
istry treatmenUplant system/materials combination. Thus, the way is clear for
any organization that desires to improve or build in reliability and performance
either in a new unit or asretrofit.
Issue: 2002, 4(6), 329-335
Title: The Electrochemistryof IGSCC Mitigation
Author(s):
Digby D. Macdonald
Abstracts: A brief review is presented of the electrochemical
mitigation of intergranular stress corrosion cracking (IGSCC) in water cooled
reactor heat transport circuit structural materials. Electrochemical control and
mitigation is possible because of the existence of a critical potential for
intergranular stress corrosion cracking and due to the feasibility of modifying
the
Issue:
Title:
Author(s):
Abstracts: environment to displace the corrosion potential to a
value that is more negative than the critical value. However, even in cases
where the corrosion potential cannot be displaced sufficiently in the negative
direction to become more negative than the critical potential, considerable
advantage is accrued, because of the roughly exponential dependence of the crack
growth rate on potential. The most important parameters in affecting
electrochemical control over the corrosion potential and crack growth rate are
the kinetic parameters (exchange current densities and Tafel constants) for the
redox reactions involving the principal radiolysis products of water (02,
H2,H2O2). external solution composition (concentrations of 02, H2O2, and H2),
flow velocity, and the conductivity of the bulkenvironment. The kinetic
parameters for the redox reactions essentially determine the charge transfer
impedance of the steel surface, which is shown to be one of the key parame- ters
in affecting the magnitude of the coupling current and hence the crack growth
rate. The exchange current densities, in particular, are amenable to control by
catalysis or inhibi- lion, with the result that surface modification techniques
are highly effective in controlling and mitigating intergranularstress corrosion
cracking in reactor coolant circuit materials.
Issue: 2002, 4(6), 339-346
Title: Chemical Cleaning of UK AGR Boilers
Author(s):
Andy Rudge Phil Turner Ajit GhoshWolfgang Clary David R. Tice
Abstracts: For the first time in their operational lives, UK
AGR once- through boilers have been chemically cleaned. Chemical cleaning was
necessary to avoid lost output resulting from boiler pressure drops, which had
been increasing for a num- ber of years. Chemical cleaning of these boilers
presents a number of unique difficulties. These include lack of access to the
boilers, highly sensitised 316H superheater sections that cannot be excluded
from the cleaning flow path, relatively thin boiler tube walls and an
intolerance to boiler tube failure be- cause of the role of the boilers in
nuclear decay heat removal. The difficulties were overcome by implementing the
clean in a staged manner, starting with an extensive materials testwork
programme to select and then to substantiate the cleaning process. The selected
process was based on ammoniated citric acid plus formic acid for the principal
acid cleaning stage. Materials testwork was followed by an in-plant trial clean
of six boiler tubes. further materials teslwork and the clean of a boiler tube
In a full-scale test rig. An overview is presented of the work that was carried
out to demonstrate that the clean could be carried out safely, effectively and
without leading to unacceptable corrosion losses. Full-scale chemical cleaning
was implemented by using as much of the existing plant as possible. Careful
control and monitoring was employed to ensure that the cleaning was implemented
ac- cording to the specified design, thus ensuring that a safe and effective
clean was carried out. Full-scale cleaning has re- suited in significant boiler
pressure drop recovery, eventhough the iron burden was relatively low and
cleaning was completed In a short time.
Issue: 2002, 4(6), 349-353
Title: Thermally Stable Anion Ex- change Resin and Postu- lated
Effect by Application in Condensate Polishing Sys- tern
Author(s):
Keiko Kudo Masako Yasutomi Hirohisa Kubota
Abstracts: A strongly basic anion exchange resin which has a
butylene spacer between the ion exchange group (trimethylammonium group) and the
benzene ring has been found to have higher thermal stability than conventional
anion exchange resin, which places the trimethylammonium group in the benzyl
position. Thus it is now possible to operate anion exchange resin at higher
temperatures than was previously acceptable. Elevated temperatures decompose the
chemical structure of anion exchange resin at the anion exchange site. The rate
of thermal decomposition is much higher with conventional an- ion exchange resin
as compared to thermally stable anion exchange resin. In addition, it is known
that in condensate polishing systems polystyrenesulfonic acid leaches out of
cation exchanger. These polystyrenesulfonic acid species can be adsorbed at
anion exchange sites of anion exchange resin. Thus, thermally stable anion
exchange resin exhibits a higher adsorption capability for polystyrenesulfonic
acid than does conventional anion exchanger. especially when they are utilized
at elevated temperatures. In condensate polishing systems, the requirement for
anion exchange resin with higher sulfate capability at elevated temperatures has
been increasing in order to generate higher power levels for longerperiods and
to maintain the reliability of the power plant.
Issue: 2002, 4(6), 357-362
Title: Probabilistic Analysis of Tur- bine Disc Stress
Corrosion Cracking Incubation and Propagation
Author(s):
Tony C.-T. Lam Robert P. Dewey
Abstracts: Stress corrosion cracking (SCC) is a common problem
found on aging low pressure turbine rotors that operate in a weVdrystream
environment. While much has been published on the growth rate of sec in turbine
rotor disk materials, Incubation time is rarely addressed. Since no effective
way has beendemonstrated to prevent disk rim sec from occurring otherthan to
replace the damaged rim with a weld repair of higher chromium content, a better
understanding of incubation timecould provide operators with a means to treat
sec beforecracks are large enough to start to grow. This paper dis- cusses the
critical mechanisms involved in the SCC incuba- tion process and describes a
probabilistic approach to makemeaningful assessments of incubation time. Data
published for General Electric turbine rotors is used to test the model.
Issue: 2002, 4(6), 365-375
Title: What Have We Learned in Seven Conferences on Unburned
Carbon on Utility Fly Ash? - A Review of Past Conferences
Author(s):
Thomas C. Ruppel Alfred N. Mann Leo E. Makovsky
Abstracts: The information presented in the previous seven
Confer- ences on Unburned Carbon (UBC) on Utility Fly Ash. dating from 1995 to
2001, is reviewed. The objectives of the con- ferences have been (1) to provide
a forum for ash associa- lions. boiler manufacturers, entrepreneurial companies,
fed- eral and stale government agencies, research personnel and utilities lo
discuss technical, regulatory and economic issues associated with UBC, and (2)
to facilitate progress toward mitigating the problem.Past conference subjects
have consisted of regulatory up- dates, experiences and observations, predictive
performance tools, processing and utilization of high-UBC fly ash, high- UBC ny
ash characterization, effects on specifications and resultant sales, and
economics. The impact of the confer- ences towards understanding and mitigating
the problem ofUBC on fly ash is analyzed.
Issue: 2002, 4(7), 384-390
Title: Importance of ECP in the Prediction of Radiation Fields
in PWR and WER Primary Circuits
Author(s): Mirna
Urquidi-Macdonald Stefany Lyn Jacesko Digby D. Macdonald Monica
Salter-Williams
Abstracts: A model has been developed for predicting mass and
activity transport in the primary coolant circuits of PWRs and WERs with the
objective of demonstrating and quantifying the im- portance of the
electrochemical corrosion potential (ECP) in determining the impact of both
processes on reactor opera- tion. The model initially employs a radiolysis/mixed
potential code to calculate the ECP at four locations (core, hot leg, steam
generator, cold leg) and the ECP is then used to esti- mate the local magnetite
solubility. The solubility is then av- eraged around the loop to yield the
"background" solubility. Comparison of the bac;:kground solubility with the
local solu- bility determines whether precipitation or dissolution will occur at
any given point in the circuit under any given set of condi- tions. It is
further assumed that the concentration of 59Co in the coolant is given by the
isotopic fraction of this species compared with iron averaged over all materials
and weighted by the respective wetted areas. Activation of 59Co to 6°Co Is
assumed to occur in the coolant phase by fast, epithermal, and thermal neutron
capture. The calculated activity is then used to train an artificial neural
network to establish relation- ships between activity at any given location and
the operating properties of the reactor, Including coolant pH, ECP. tern-
perature. power level, etc. The model predicts that during shutdown, magnetite
(and hence 59Co) migrates to the core, where it is irradiated and activated,
particularly during subse- quent startup. During startup, the magnetite (and
hence &>Co)migrates from the core to out-of-core surfaces, where it es-
tablishes the radiation fields.
Issue: 2002,4(7). 393-399
Title: Power Station Chemists - Recent Past, Present Life and
Visions of the Future
Author(s): Craig Torville
Abstracts: Challenges and key result indicators for power
station chem- ists are economic, technical, and managerial. Whal should we carry
from the past. to manage the present and meet future economic, technical, and
managerial challenges? The results of an Australia-wide survey are presented in
an attempt to develop a view of future impacts on the powerstation chemist's
role.
Issue: 2002, 4(7), 401-405
Title: My Dream Plant
Author(s): Sallie
Fisher
Abstracts: A chemist with over 50 years experience in systems
design for and monitoring the performance of high purity water pro- duction
systems puts together pieces for primary treatment and condensate polishing for
a future power plant with em-phasis on reliable performance rather than capital
cost.
Issue: 2002, 4(7), 407-410
Title: Spotlight on the Cation Resin
Author(s):
Sallie Fisher
Abstracts: A review of the overall dependence of sulfonic acid
resin performance on divlnylbenzene content shows that resinselection based on a
single property is probably unwise.
Issue: 2002, 4(7), 411-412
Title: Legionella - An Appendix to the Saga
Author(s):
Geoff Spowart
Abstracts: This paper deals with the issues racing power
stations at- tempting to manage Legionella in large scale cooling water systems.
Australian power stations are keen to minimise Legionella levels and therefore
are seeking to establish a standard suitable for the industry without the
prescriptive requirements of the existing air conditioning standard. The issues
surrounding metallurgy, environmental discharges. system complexity and makeup
water quality and quantity are examined. The work that has been done over the
past twoyears is detailed.
Issue: 2002, 4(7), 413-417
Title: Reducing the Volume of Water in Tarong Power Sta- lion's
Ash Dam
Author(s): David Knights
Abstracts: Tarong Power Station, a major supplier to
Queensland's electricity grid, recently faced a potentially severe operational
problem. A prolonged drought in the first half of the 1990s significantly
depleted supplies of raw water. Water conserva- tion measures were implemented,
but required cooling tower blowdown to be stored in the on-site ash dam.
Consequently, rising water levels In the ash dam posed a significant envi-
ronmental risk. Several methods of water removal were con- sidered, but a novel
approach, using installed plant, was eventually chosen, with a very successful
outcome. This pa-per traces the problem and its eventual solution.
Issue: 2002, 4(7), 419-423
Title: Power Stations and the ANZECC/ARMCANZ WaterQuality
Guidelines
Author(s): Graeme E. Battey Kenneth W. Riley
Abstracts: The release of waters from coal-fired power stations
may be of environmental concern in some environments. The man- agement of large
volumes of ash dam water can be particu- larly difficult. "Dry" landfill sites
may also release trace ele- ments where groundwater or rainwater comes into
contact with the ash residue. A number of these elements are toxic or accumulate
in organisms to an extent that biological function is impaired. The biological
activity of the leached elements Is a function of factors such as speciation
(including organic complexatlon), pH and water hardness. Simple limits of water
release based on concentration alone are often used in the licensing of power
stations but are an inadequate parameter with which to manage water quality. The
Australian and New Zealand Environment Conservation Council Water Quality
Guidelines provide broad holistic guidance on discharge lim- its as well as
detailed advice on the monitoring and assess-ment of environmental impact.
Issue: 2002, 4(8), 449-455
Title: Oxygenated Treatment at Huntly Power Station Unit 2:
Preliminary Results from Steady State and 2-Shifting Operation
Author(s):
David Addison Keith Hopkins Brad White
Abstracts: Concerns over flow-accelerated corrosion (FAC)
damage in the feed systems of the four Huntly Power Station 250 MW units and the
corresponding risk to personnel and plant led to a decision in 1995 to eliminate
the use of an oxygen scaven- ger (hydrazine) on all units and in February 2000
to a deci- sion to go ahead with a trial of oxygenated treatment (OT) on Huntly
Power Station Unit 2.The injection system, designed in-house, incorporates a
sin- gle oxygen injection point between the condensate polisher and LP heater 1,
injecting to a concentration of 50 µg •kg·' dissolved oxygen based on condensate
flow.Oxygen injection on Unit 2 commenced in October 2001. During oxygen
injection, the deaerator is operated with the vent to condenser shut. Soluble
and insoluble iron and cop- per measurements are made at the economiser inlet,
boiler downcomer and main steam primary sample points. Prob- terns have been
experienced with the injection system con- trol, passing valves in the deaerator
leading to oxygen loss, air inteakage at the chemical analyser wet racks and
ana- lytical issues with dissolved oxygen and oxidation reduction potential
measurements.Immediate changes in oxide layer morphology were observed during an
internal inspection after two weeks of OT operation with previous FAG-damaged
areas now showing the growth of a hematite dominated layer, giving an early
favourable result for OT operation.Preliminary results from corrosion product
sampling have indicated that no copper migration in the steam to the turbine has
occurred and there is a decrease in insoluble iron levels during steady state
operation. 2-shifting operation has led to a slight increase in the insoluble
iron levels being detectedabove steady state values.
Issue: 2002, 4(8), 457-465
Title: lntergranular Corrosion in a Stainless Steel Reheater
Author(s):
Charles Emslander Alan Waddingham
Abstracts: Stainless steel has been used In power boilers for
over 40 years In the hottest sections of the superheater and reheater. One of
the most common alloys used in these sections is SA 213 TP304H. It provides a
good balance of mechanical properties and corrosion resistance to minimize the
effects from coal ash corrosion, high temperature oxidation and long term creep
mechanisms. However, recurring failures in astainless steel reheater prompted a
root cause analysis and the development of an eddy current testing method.
Issue: 2002, 4(8), 467-472
Title: The Resin on Resin Tech nique for Minimising Sodium
Levels in Water from CP Mixed Beds
Author(s): Michael A.
Sadler
Abstracts: The mechanisms by which traces of impurities can
escape being removed by the ion exchange resins used in conden- sate polishing
plants are generally well known. They can still be a problem when attempting to
prepare very high quality water such as when using condensate polishing to
purify condensate. Some of these mechanisms can be controlled by attention to
the design and operation so that the effect known as equilibrium leakage often
becomes the predominant mechanism controlling the leakage of ionic impurities in
the treated condensate. Equilibrium leakage can itself be con- trolled by
reducing the levels of ionic impurities remaining on resins after regeneration
and so a considerable amount of effort has been directed at improving
regeneration processes. When regenerating mixed beds It is essential to achieve
as complete separation as possible, but although improvements can be made. some
resin cross-contamination Inevitably occurs. Several proprietary processes exist
that seek to cor- rect this problem and some have proved very effective. A
simple non-proprietary technique, ''Resin on Resin", repre- sents a different
approach to reducing the trace leakage of sodium that result from a small
quanUty of cation resin being entrained In the anion resin and so becoming
sodium con- taminated. The paper discusses the application of "Resin on Resin",
the possible theoretical basis for its action and the results that have been
reported by power stations that haveadopted its use.
Issue: 2002, 4(8), 475-481
Title: Quantitative Air Ingress Leak Detection In Power Plant
Turbine Condensers
Author(s): S. Ian Garbutt Robin
Walker
Abstracts: Power plant main turbine condensers often suffer
from deg- radation in back pressure resulting in reduced output. When this is
due to increased air ingress, it is not necessarily a function of ineffective
detection, but had more to do with the fact that the source of the air ingress
is often difficult to lo- cate. Current methods or detection are either
qualitative or quantitative in terms of the overall air ingress into the system.
This, however, presents the problem to plant engineers of establishing the
largest source(s) of air ingress. By their very nature, power plant vacuum
systems are extensive and have remote/tortuously linked connections with the
condenser, thereby providing a multitude of potential air ingress sites. Working
on the 80/20 rule, the ability to quickly locate, from a few measurements, the
largest sources of air ingress would represent a powerful tool and one of
significant financial benefit.A technique developed over several years by
QuantiFlo and used successfully in UK power plants is that of "Quantitative Air
Ingress Measurement". Using strategically located tappings, the technique
enables the plant engineer to rapidly focus on areas of high air ingress rather
than spend valuable lime finding "in-leakage" that when sealed, produces little
or no change in condenser back pressure.Two case studies have been conducted
within British Energy power plants. The first reduced the average condenser back
pressure by 2.3 kPa (approximately 13 MW electrical) and highlighted areas for
further potential gain. The second reduced the total air ingress from 0.0374
kg· s-1 (0.0288 m3 • s-1) to 0.0160 kg· s-1 (0.0123 m3 • s-1).
Issue: 2002, 4(8), 483-486
Title: Cooling Tower Experience at Osborne Cogeneration
Author(s):
Michael Thompson Anthony Dal-Corobbo Bassam Zaid
Abstracts: Cooling water for the 180 MW Osborne Cogeneration
plant is sourced from a saltwater river. To comply with the local Envi-
ronmental Protection Authority licensing requirements for the cooling water
discharge temperature and concentration, a cooling tower and dilution water
system are employed. The tower is a five-cell, counter flow, induced draught
type. Bio- cides are dosed intermittently with no cooling tower blow- down and
recirculated until measured chemical residuals decrease below detectable limits
before blowdown is rein-stated.
Issue:
Title:
Author(s):
Abstracts: To date, the adopted cooling water system chemical
dosing and operational regime is providing good scale control and biological
activity has been confined to the cooling tower proper with no reported drop in
performance of the single main condenser.Slime growth is problematic and ongoing
below the tower fill, particularly on the outer structure. Bacteria testing of
slime samples indicates vibrio strains are the main species present. Biocide
dosing automation is being pursued and alternative biological control programs
investigated for the effective con-trol of this slime growth.
Issue: 2002,4(9), 513-520
Title: Dispersant Trial at ANO-2: Results from a Short-Term
Trial Prior to SG Replace- ment
Author(s): Keith Fruzzetti
Paul Frattini Phil Robbins Alan D. Miller Robert D. Varrin Marc Kreider
Abstracts: Corrosion products that make their way to the
secondary side of pressurized water reactor (PWR) steam generators (SGs) via the
feedwater can deposit on the SG tubes. These de- posits can form an occluded
region which inhibits heat trans- fer, leads to thermal hydraulic Instabilities
through blockage of tube supports and creates regions where corrosive species
can concentrate along tubes and tube to tube support plate crevices. The
performance of the SG is compromised not only by formation of an insulating
scale, but by the removal of tubes from service due to corrosion.A promising new
method for significantly reducing corrosion product deposition on the secondary
side of recirculating steam generators is the use of online dispersant addition
to help prevent the corrosion products from adhering to the steam generator
surfaces. By inhibiting the deposition of the corrosion products, they are more
effectively removed from the steam generator via blowdown. After completion of a
significant and comprehensive qualification program, a short- term dispersant
trial was performed at Arkansas Nuclear One Unit 2 (ANO-2) In Winter/Spring
2000, lasting approximately 3 months. A high purity, high molecular weight
polyacrylic acid (PAA) dispersant produced by BetzDearborn was in- jected at low
concentrations (0.5 µg •kg-1 to 12 µg •kg-1) into the final feedwater. The
blowdown iron removal efficiency was observed to increase by an order of
magnitude and more with use of PAA. Normal chemistry parameters, such as
blowdown cation conductivity and TOC/TIC, were unaffectedby PAA application. The
results and conclusions from the trial are presented and discussed.
Issue: 2002, 4(9), 521-526
Title: HRSG Waterside Failure Mechanisms
Author(s):
David G. Daniels
Abstracts: Heat recovery steam generators (HRSGs) are
responsible for more and more of the steam generating capacity of many
utilities. Unfortunately, they are also increasingly responsible for the number
of tube failures in the system. Corrosion that leads to failures often begins
before commissioning and is exacerbated by cycling operation. This article
reviews com- mon waterside failure mechanisms in HRSGs, where theyoccur, and
what can be done to prevent failures In the future.
Issue: 2002, 4(9), 535-541
Title: Reducing Dissolved Oxygen under Conditions of High Air
Ingress
Author(s): Joseph W. Harpster
Abstracts: Recent considerations of steam and air mixture
dynamics in operating condensers have led to a more thorough under- standing of
how condenser performance is affected by air in- leakage. Results of this
model-based theoretical description, which are in agreement with measurement
data from oper- ating condensers, are reviewed and used to propose benefi- cial
design features for new and re-tubed condenser assem- blies.It is anticipated
from this work that condensers can be de- signed which significantly reduce the
amount of dissolved oxygen in condensate from locations of free air ingress
above the hotwell level. This reduction also applies to other undesir- able
noncondensables that enter condensate driven by the same mechanism contributing
to dissolved oxygen. When air in-leakage becomes sufficiently high, it
contributes to excess back pressure on the turbine. In this region of high air
in- leakage, the amount of dissolved oxygen can become very high. The design,
therefore, minimizes or eliminates the cor- rosive effects of air in-leakage,
both high and low, which is particularly important during periods of high demand
whenload must be maintained.
Issue: 2002, 4(9), 543-547
Title: Closed Cooling and Heating Systems in Power Plants
Author(s):
K. Anthony Selby
Abstracts: Closed recirculating systems are used for cooling
and heating tasks in power plants. In the power plant environment, these
"balance of plant" systems often do not receive the same attention as the steam
generating/turbine cycle. Nonetheless, closed recirculating systems play an
important role in the consistent and safe operation of the plant.Closed
recirculating systems experience problems of corro sion, microbiological
growth, and fouling. These problems can be minimized through appropriate
chemical and physical treatment. Closed systems must be adequately monitored to
determine treatment needs, control treatment programs anddetect problems.
Issue: 2002,4(9), 549-555
Title: Fireside Corrosion of Alloys for Combustion Power
Plants
Author(s): Ken Natesan Ankur Purohit David L.
Rink
Abstracts: A program on fireside corrosion is being conducted
at Ar gonne National Laboratory to evaluate the performance of several
structural alloys in the presence of mixtures of syn thetic coal ash, alkali
sulfates, and alkali chlorides. Candidate alloys are also exposed in a
small-scale coal-fired combustor at the National Energy Technology Laboratory in
Pittsburgh. Experiments in the present program, which addresses the effects of
deposit chemistry, temperature, and alloy chemistry on the corrosion response of
alloys, were conducted at temperatures in the range of 575 •c - 800 •c for time
periods upto ==1850 h. Alloys selected for the study Included HR3C, 310TaN,
HR120, SAVE25, NF709, modified 800, 347HFG,and HCM12A. In addition, 800H clad
with Alloy 671 was in cluded in several of the exposures. Data were obtained on
weight change, scale thickness, internal penetration, micro structural
characteristics of corrosion products. mechanical integrity. and cracking of
scales. Results showed that the relationship of corrosion rates to temperature
followed a bellshaped curve, with peak rates at ==725 •c, but the rate
itselfwas dependent on the alloy chemistry. Several alloys showed acceptable
rates in the sulfate-containing coal-ash environ ment; but NaCl In the deposit
led to catastrophic corrosion at650 and 800 •c.
Issue: 2002, 4(9), 557-561
Title: Elemental, Mercuric and Organic Mercury: Biological
Interactions and Dilemmas
Author(s): H. Vasken Aposhian
Abstracts: The greatest exposure of the general population to
mercury appears to be from the elemental mercury emitted by dental amalgams. The
next greatest exposure Is from methylmer cury in seafood. One of the major
sources of this methylmer cury is from mercury emitted by power plants burning
fossil fuel. After the mercury enters the atmosphere, some of it will be
deposited In lakes, rivers. bays, seas and oceans. In an aquatic environment,
inorganic mercury is converted to methylmercury by bacteria. Once in the
methylmercury form, it is bioaccumulated up the food chain. The bacteria are
con sumed by other unicellular organisms that are eaten by small fish; small
fish are eaten by bigger fish; then bigger fish are eaten by other animals and
humans. Methylmercury and elemental mercury are efficiently absorbed by humans
and are transported rapidly to and deposited in the brain. In the brain,
methylmercury is converted very slowly to mercuric mercury while the elemental
mercury is converted very quickly. Methylmercury and elemental mercury are
extremely toxic to the developing central nervous system. Those at greatest risk
are fetuses, very young children, women of childbearing age and pregnant women.
There are no safe or reliable methods to remove these two forms of mercury and
their biotransformant mercuric mercury from the human brain. The chelating
agents DMPS (sodium dimercaptopropanesul fonate) and DMSA (dimercaptosuccinic
acid) decrease the body's burden of mercury but not the brain's. Because of the
toxicity of methylmercury, the major source of mercury emis sions, namely,
emissions from power plants, needs to becurtailed.
Issue: 2002,4(10), 582-589
Title: Flue Gas SO3 Determination- Importance of Accurate
Measurements in Light of Recent SCR Market Growth
Author(s):
Jack Bionda
Abstracts: This paper presents background information on SO3
forma tion, SCR operation, as well as a discussion of the inter-re lated
nature of SCR performance and SOa, and how each can affect balance of plant
operation. A detailed discussion of applicable EPA, ASTM and instrument test
methods for the determination of sulfuric acid mist is also presented. Testing
challenges associated with flue gas sampling downstream of wet scrubbers is also
discussed, as well as the !Imitations ofeach of the relevant test methods.
Issue: 2002, 4(10), 590-596
Title: Thermal Shock Cracking in Carbon Steel Boiler Pressure
Equipment - Guidelines for Initiation and Growth
Author(s):
John W. H. Price Brian Kerezsi
Abstracts: Thermal shock cracking is an important damage
mechanism for many pressurised components. The growth of thermal shock cracks is
influenced by a combination of several fac- tors including geometry, the
severity of the thermal shocks, the applied mechanical loads and the
environment.In the work reported here it is shown that thermal shock cracks will
arrest if these factors are below certain limits. In other cases, the cracking
can progress and eventually cause failure or other operational problems. This
work seeks to determine the relevant levels of these factors.This paper presents
an analysis of the crack growth mecha nisms Involved, including an assessment
of the environ mental effects. Proposals are presented as to the guidelines
which might be used for design and operation of vessels to prevent the
initiation of thermal shock cracking. The guide lines presented here are much
more nexible than the highly restrictive guidelines published by EPRI in 1989
for econo miser headers.The work also includes a study of the nature of the
growth of the cracking. Most of the cracks are found to grow in condi tions
leading to arrest. This presents the possibility of fitness for purpose
assessment of the cracking when it is found in service.
Issue: 2002, 4(10), 597-603
Title: Cation Conductivity - What Are We Talking About?
Author(s):
Albert Bursik
Abstracts: Cation conductivity monitoring in a plant cycle is
the basic surveillance tool for detecting the ingress of contaminants in the
cycle. Unfortunately, cation conductivity of a sample is a non-specific
parameter. The kind of substances contributing to or causing a cation
conductivity increase are not known. For this reason, evaluating the value
measured is not easy or is hardly possible.The results of calculations performed
show that more precise information about the cycle contamination during periods
with slightly or markedly increased cation conductivity is required. Whereas a
steam contamination with chlorides, sulfates, and formates is dangerous even at
very low contaminant con centrations, the presence of acetates and in
particular of carbon dioxide appears to be relatively harmless.Further
evaluation for cycles using amines as alkalizing agents and additional or
improved surveillance techniques for interpreting the cation conductivity values
measured are re quired. The focus should be on contaminants that may toinitiate
or take part in local environment-related turbine dam age mechanisms.
Issue: 2002, 4(10), 605-620
Title: Conversion Factors
Author(s):
Barry N. Taylor
Abstracts: This publication gives factors for converting values
of quan- lilies expressed in various units - predominantly units outside the
International System of Units (SI) that are unacceptable for use with it - to
values expressed either in (a) SI units, (b) units that are accepted for use
with the SI (especially units that better reflect the nature of the unconverted
units), (c) units formed from such acceptable units and SI units, or (d) decimal
multiples or submultiples of the units of (a) to (c) that yield numerical values
of convenient magnitudes.The factors for units are listed by kind of quantity or
field of science.
Issue: 002, 4(11), 641-649
Title: Evaluation of LP Rotor Rim Attachment Cracking Using
LPRimlife
Author(s): Darryl A. RosarioS. S. (Stan) Tang
Peter C. Riccardella David W. Gandy Ramaswamy (Vis) Vlswanathan
Abstracts: Stress corrosion cracking (SCC) in the blade
attachment region of low-pressure (LP) turbine rotors has emerged as one of the
most significant problems affecting both nuclear and fossil steam turbines
today. To assist turbine operators in evaluating the remaining life of LP rotors
with known or suspected cracking, an easy-to-use PC-based computer program,
LPRimlife, was developed for EPRI by Structural Integrity Associates. The first
phase of development. incor- porating the methodology for evaluating cracking in
General Electric (GE) dovetail (straddle-mount) attachments, was completed in
1999 (1). The second phase, which included evaluation of cracking in
Westinghouse axial-entry (steeple) attachments, was completed in 2000 [2]. The
third phase, to address cracking in GE multi-pin-finger attachments, is cur-
rently under way.Since initial development, the LPRimlife computer code has been
successfully employed at nuclear and fossil plants, providing the basis for
deferring or eliminating major
Issue:
Title:
Author(s):
Abstracts: unscheduled and costly repairs, such as "pressure
plating," which would have significantly extended the outages. Defer ring
unscheduled repairs for even one more fuel cycle allows for advance planning to
evaluate and select the most-effec tive repair/replacement option and lead time
needed for pro curement of appropriate materials/services. In today's com
petitive marketplace with ever-tightening outage schedules, timely application
of LPRimUfe has resulted in significant cost savings to utilities.This paper
provides a summary of the LPRimlife program methodology, software features and
recent utility applications.
Issue: 2002, 4(11), 653-659
Title: Solubility of Sodium Chloride in Superheated Steam
Author(s):
J0rgen Peter Jensen Karol Daucik
Abstracts: The solubility of sodium chloride In superheated
steam was investigated in laboratory-scale experiments up to 20 MPa and 475 °C.
These experiments were carried out using a dynamic method where deionized steam
was passed through a packed bed of salt crystals in a 500 ml Hastelloy auto-
clave. The residence time of the steam in the salt bed was sufficient to
saturate the steam with the salt. The steam sam- ples were cooled and analyzed
by ion chromatography.Correlations based on temperature and density were
selected to describe the solubility of sodium chloride In superheated steam. The
density dependence is much stronger than the temperature dependence. By using
these correlations, it is possible to estimate the solubility of salt in steam
at lower densities than those used in the experiments.Enthalpy-entropy diagrams
are given that show the steam expansion line in turbines, including curves for
constant con- centration of sodium chloride solubility in steam. These can be
used to analyze where in the steam cycle this salt maydeposit.
Issue: 2002, 4(11), 665-668
Title: Condensation of Steam
Author(s):
Vitaly A. Prisyazhniuk
Abstracts: An equation for nucleation kinetics in steam
condensation has been derived, the equation taking into account lhe con- current
and independent functioning of two nucleation mechanisms: the homogeneous one
and the heterogeneous one. The equation is a most general-purpose one and In-
cludes all the previously known condensation models as spe- cial cases. It is
shown how the equation can be used in ana- lyzing the process of steam
condensation in the condenser of an industrial steam-turbine plant, and in
working out new ways of raising the efficiency of the condenser, as well as
ofthe steam-turbine plant as a whole.
Issue: 2002, 4(11). 671-683
Title: Chemical Cleaning's Role in Tube Failure Prevention and
Correction
Author(s): Kevin J. ShieldsR. Barry Dooley
Abstracts: Properly applied, chemical cleaning is a valuable
tool used to prevent tube failures Involving overheating and corrosion due to
waterside deposits. In many cases, however, cleaning becomes yet an additional
cost associated with correction of tube failure incidents. Discussion is focused
on approaches taken to appraise tube waterside cleanliness and determine the
need to clean, as typically practiced in conventional fossil plants. Also
presented is an assessment of the suitability and limitations of these
approaches to plants with heat recoverysteam generator units.
Issue: 2002, 4(11), 687-690
Title: Sodium to Phosphate Ratios
Author(s):
George J. Verib
Abstracts: Phosphate chemistry is widely used in fossil-fired
utility boil- ers and many of these phosphate programs use the sodium to
phosphate ratio as the controlling parameter. This paper steps through the
fundamental chemical analyses to deter- mine a systems Na/PO4 ratio. A
mathematical equation is introduced to simply calculate the ratio using the pH
and phosphate concentration. This equation is also used to build graphs to chart
the boiler's phosphate chemistry. By looking at the dynamic nature of the
chemistry, boiler health can bedetermined.
Issue: 2002, 4(11), 693-696
Title: Heavy Metal Discharge from Coal-Fired Power Plants - How
Does This Affect the Environment and Cost-Ef- fective Production of Electric
Power?
Author(s): Ernest Beinrohr Walter Labhart Eric V.
Maughan
Abstracts: Although heavy metals are naturally occurring
elements, there are rather draconian laws, imposed by global authori- ties and
institutions, which forbid their discharge from industry into the environment.
Most of these elements have limits of concentration which are not readily
measured by standard laboratory techniques. Even if measurable, how may these
contaminants be adequately dealt with?Fossil-fired power plants without a
dry-ashing facility suffer the risk of accidental discharge of undesired heavy
metals leached from the disposed ash via the wet-ashing disposalsystem.
Issue:
Title:
Author(s):
Abstracts: This paper investigates:a continuous method of rapid
identification and measurement of heavy metals and• an economical method for the
safe removal and disposal of these contaminants.
Issue: 2002, 4(12), 707-711
Title: Dissociation Quotients of Aqueous Dimethyl ammonium
Ion
Author(s): Pascale Benezeth Donald A. Palmer David J.
Wesolowski
Abstracts: The acid dissociation equilibria involving aqueous
dimethyl- ammonium ion in the reaction(CH3)iNH2' ,=! (CH3)2NH+ H'were measured
potentiometrically with a hydrogen-electrode concentration cell from O 0c to 290
•c in sodium trifluoromethanesulfonate (NaTr) solutions at ionic strengths of
0.1,0.3 and 1 molal. The molal dissociation quotients and se lected literature
data at infinite dilution were fitted by an em pirical equation involving six
adjustable parameters involving functions of temperature, solvent density and
ionic strengtlh. This treatment yielded the following thermodynamic quanti ties
at 25 °C and infinite dilution:logKd = -10.77 :1: 0.02,LlHd = (50.8 :1: 0.7) kJ
•mor'.L'ISo = (-35.8 :I: 2.5) J • K-' •mol 1,LlCp
Issue: 2002, 4(12), 712-719
Title: Performance of Automatic GMAW Overlays for Water wall
Protection in Coal Fired Boilers
Author(s): George Lal
Abstracts: The paper reviews the performance history of modern
weld overlays applied by the automatic gas-metal-arc welding (GMAW) process in
mitigating the severe wastage problems encountered for the waterwalls of
coal-fired boilers. Com- monly used overlay alloys of Type 309 stainless steel,
Alloy 625 and Alloy 622 are discussed. Many boilers with overlaid water walls
have accumulated service experience approach- ing 10 years with great success.
Approximately 100 boilers with about 21 000 m2 (227 000 ft2) of total waterwall
area have been overlaid with the three overlay alloys. The weld overlay has been
considered by the boiler owners/operators to be the most viable waterwall
protection method for miti- gating the severe waterwall wastage problems.
Nevertheless, a couple of boilers of one boiler design have been found to show
circumferential cracking for the 625 overlay. It has been found that this
circumferential cracking was the result of pref- erential sulfidation attack due
to overheating of the overlay surface layer to possibly 593 °C (1100 °F).
Metallurgical ls- sues on the overlay alloys are discussed. An alternate alloy
for mitigating the preferential sulfidation attack due to over-heating is
recommended.
Issue: 2002, 4(12), 721-731
Title: Monitoring for Corrosion and Microbiological Activity in
a Cooling Water System
Author(s): Michael H. Dorsey George
J. Licina Brian J. Saldanha Richard C. Ebersole
Abstracts: Corrosion of heat exchanger tubes and carbon steel
piping at a chemical processing plant had been attributed to a high level of
microbiological activity in the cooling water. Two electrochemical biofilm
activity sensors with integrated data acquisition and data analysis capabilities
were installed in the plant's cooling system to augment the coupon-based corro-
sion monitoring activity. Those sensors provided the plant with an on-line
measurement and early detection of biofilm activity on metallic surfaces. Sensor
response was correlated with coupon examinations, determinations of biocide
residuals, and determination of the numbers and types of microorganisms. Results
from the plant monitoring activity are described. These results emphasize the
necessity to Integrate the various types of field and laboratory data to monitor
and effectively control microblologically influencedcorrosion.
Issue: 2002, 4(12), 735-740
Title: Solubility of Sodium Sulfate and Sodium Hydroxide in
Superheated Steam
Author(s): J0rgen Peter Jensen Karol
Daucik
Abstracts: The solubility of sodium sulfate in superheated
steam wasinvestigated in laboratory-scale experiments up to 25 MPa and 600 •c.
These experiments were carried out using adynamic method where deionized steam
was passed through a packed bed of salt crystals in a 500 ml Hastelloy auto-
clave. The residence time of the steam in the salt bed was sufficient to
saturate the steam with the salt. The steam sam- ples were cooled and analyzed
by ion chromatography.A "density" model was selected to correlate the
experimental data of the solubility of sodium sulfate in superheated steam. The
density dependence is much stronger than the tempera ture dependence. By using
this type of correlation, it is possible to estimate the solubility of salt in
steam at lower densities than those used in the experiments.
Issue:
Title:
Author(s):
Abstracts: Enthalpy-entropy diagrams are given that show the
steam expansion line in turbines, including curves for constant con- cenlralion
of sodium sulfate and sodium hydroxide solubility in steam. These can be used to
analyze where in the steamcycle sodium sulfate and sodium hydroxide may deposit.
Issue: 2002,4(12), 743-746
Title: Boiler Tube Failures in In- dustrial Drum-Type Steam
Generators - Part 3:Alterna- live Cycle Chemistry Treat- ments
Author(s):
Albert Bursik
Abstracts: Part 1 of this paper dealt with the major
differences between steam generation in utility boilers and in industrial steam
boll- ers and other steam generating apparatus (e.g., differences in design,
material selection, and cycle contaminants) and treated some site-specific
issues influencing cycle chemistry. Part 2 dealt with the applicability of
internationally accepted boiler water treatments and with their influence on the
occur- rence of boiler tube failures.This part (the third part of a four-part
publication) discusses the applicability of amine-based plant cycle treatments
which are covered neither by the VGB Guideline for Boiler Feed- water, Boller
Water, and Steam of Steam Generators with a Permissible Operating Pressure of >
6.8 MPa nor by the setof EPRI Cycle Chemistry Guidelines for Fossil Plants.