“Lots of New Challenges for Power Plant Chemicals” - Hot Topic Yesterday
The level of knowledge demonstrated by the speakers relative to the challenges
of preventing corrosion and malfunction of gas turbine combined cycle power
plants which are cycling hundreds of times per year and may be using poor
quality source water, makes a persuasive case for continuing expert advice.
Chemicals are a big expense. Failure to maintain the right chemistry is even
more expensive. The average combined cycle power plant does not have the
staffing of a large nuclear plant. So it pays to contract with experts who can
monitor the chemistry programs.
The recorded webinar yesterday is available to you as a Utility E-Alert
subscriber. It is also available free of charge as part of two free systems for
power plants around the world. One
knowledge system deals with all the gas turbine issues and another with all the
coal issues. Power plants are
encouraged to use the systems for decision making but also to use the websites
and recordings for training programs. The session yesterday will be valuable for
both purposes.
Overview of Power Plant Chemicals
Bob McIlvaine reviewed some of the challenges:
•
Use of municipal treated wastewater (Chemtreat article posted)
•
Rapid cycling (reviewed in monitoring session earlier)
•
Air Cooled Condenser and iron transport (reviewed in monitoring recording)
Steam
Generator - Continuous Analyses
•
Effluent standards (CCR
and Effluent - Continuous Analyses
•
Zero liquid discharge
MIOX Summary – Tom Muilenberg
The Mixed oxidant system is providing savings in terms of cooling tower chemical
usage and power plant output.
Ø
The NIPSCO power plant achieved cleaner condensers, saving ~$640,000/yr.
Ø
Proprietary biocides could not control biofilm in 90,000 ton tower. Visible
biofilm buildup in the condenser.
Ø
Mixed oxidant chemistry eradicated the biofilm. Replaced the biocide regime.
Ø
Paul Schrock, NIPSCO Senior Chemist stated, “Reducing our treatment regimen…down
to a single mixed oxidant product generated on site has resulted in substantial
treatment chemical and labor cost savings.”
HDR Summary – Colleen Layman
o
Program needs to factor in unit specific design and operational aspects
Use of amine blends with different vapor/liquid distribution ratios
Kiewit Summary – Brad Buecker
Brad answered some of the most important questions facing the industry.
“Bob McIlvaine and his staff posed a set of questions to me that are very
important regarding HRSG water/steam chemistry and prevention of corrosion and
fouling in steam generators. Even seemingly minor issues have been known
to cause failures that cost power producers millions of dollars and in some
cases even claimed lives. This is the ultimate cost.
Each question and a straight forward answer follows:
Question #1
�
Are chemical treatment methods available to reduce flow-accelerated corrosion
(FAC) in HRSGs?
Answer #1
�
Yes. For starters unless the
feedwater system contains copper alloys (virtually non-existent in HRSGs) do
not use an oxygen scavenger/reducing agent.
�
Second, keeping the pH elevated in a mid 9 range or even a bit higher,
particularly in the LP circuit, will help with single-phase FAC.
�
The situation is more complicated for two-phase FAC.
Please feel free to contact me directly for a more detailed discussion of
FAC.
(brad.buecker@kiewit.com
Question #2
�
With fast start HRSGs and constant cycling, what chemical additions will counter
some of the negative consequences of this operating mode?
Answer #2
�
I have worked with my friend Dan Dixon of Lincoln Electric System on this issue,
and we co-authored an article for Power Engineering on the subject.
�
Keep oxygen out of the system during shutdowns.
The best method is nitrogen blanketing.
Nitrogen generators are available that can do a great job in producing
99.9-plus percent N2.
�
Remove oxygen from makeup water.
Membrane systems are available that can reduce water saturated with oxygen to
low ppb levels.
Question #3
�
If the plant has an ACC rather than a water-cooled condenser and the condensate
iron content is much higher, how can this problem be solved?
Answer #3
�
Install a full-flow particulate filter in the condensate line. Most of the iron
generated from corrosion in ACCs is particulate in nature.
�
I purchased one of these units at a coal-fired plant where I worked to remove
iron particulates following boiler chemical cleanings. The equipment paid for
itself several times over after the first use.
�
The original system had filters with 7-micron pore size, but plant personnel
found that 10-micron worked just as well.
Question #4
�
What are the water chemistry issues facing GTCC operators that are unique to
this type of power generation?
Answer #4
�
Several major issues are facing plant operators, some of which transcend many
industries.
�
Dealing with less-than-pristine raw water sources. Municipal wastewater
treatment plant effluent is one example.
�
Discarding the idea that an oxygen scavenger/reducing agent is needed for
condensate/feedwater treatment.
�
Handling the different chemistry regimes in multi-pressure HRSGs.
�
New requirements for cooling tower chemical treatment.
�
Dealing with increasingly stringent wastewater discharge guidelines.
Question #5
�
What are the chemical treatment needs if zero liquid discharge (ZLD) technology
is mandated?
Answer #5
�
ZLD is a complex subject, not to be taken lightly.
�
One method gaining popularity is treatment of the discharge with membrane
technologies to greatly reduce the volume. Even so, a waste stream still
remains. Methods, all of which can
be problematic, to deal with the final waste stream include:
�
Evaporation ponds
�
Deep-well disposal
�
Truck the liquid off-site.
�
Thermal evaporation/crystallization with solids disposed in an approved landfill
Question #6
�
Treated wastewater often contains much higher concentrations of ammonia,
phosphorus, organics, and suspended solids than fresh water. These impurities
can cause induce excessive microbiological fouling in cooling systems, can carry
over into the wastewater stream, and can be problematic for makeup water
systems.
Answer #6
�
Treated wastewater often contains much higher concentrations of ammonia,
phosphorus, organics, and suspended solids than fresh water. These impurities
can cause induce excessive microbiological fouling in cooling systems, can carry
over into the wastewater stream, and can be problematic for makeup water
systems.
�
Makeup water clarification and solids precipitation may be a requirement to
treat these streams.
�
Selection of an alternative to chlorine (bleach) such as chlorine dioxide may be
necessary.
�
Cooling tower sidestream filtration is never really a bad idea.
Question #7
�
How can plugging of combustion turbine inlet air fogging nozzles be prevented,
and what is necessary to prevent introduction of contaminants to a combustion
turbine?
Answer #7
�
Any water injected ahead of or into a combustion turbine for cooling, NOx
control, or power augmentation must be very high-purity, i.e., a stream from the
makeup water system. Impurities can
be very harmful to combustion turbine blades and rotors in the extremely harsh
environment. Far more often than fogging systems I see evaporative coolers used
for inlet cooling. I also have assisted a group that developed an ammonia-based
chilling system for inlet air cooling (and heating in the winter). It eliminates
the issue of poor water possibly being inducted into the turbine.
You can view and listen to the recording at
Power
Plant Water Treatment Chemicals
100 minutes.
You will need to enter your name and email address after clicking link to view
recording.
Presentations follow:
Power Plant Chemicals Webinar - Hot
Topic Hour September 25, 2014
The level of knowledge demonstrated by the speakers relative to the challenges
of preventing corrosion and malfunction of gas turbine combined cycle plants
which are cycling hundreds of times per year and may be using poor quality
source water makes a persuasive case for continuing expert advice.
Revision Date:
9/25/2014
Tags:
221112 - Fossil Fuel
化石燃料,
221112 - Fossil Fuel
化石燃料,
McIlvaine, Kiewit, Miox, HDR Engineering, Chemical, Cooling Tower, Sodium
Hypochlorite, Hydrogen Peroxide, Consulting
Cooling Towers by Tom Muilenberg, Miox
- Hot Topic Hour September 25, 2014
The Mixed oxidant system is providing savings in terms of cooling tower chemical
usage and power plant output.
Revision Date:
9/25/2014
Tags:
221112 - Fossil Fuel
化石燃料,
221112 - Fossil Fuel
化石燃料,
Miox, Chemical, Cooling Tower, Sodium Hypochlorite, Hydrogen Peroxide
Colleen Layman advised that chemistry limits developed for traditional
industrial watertube boilers are not generally applicable to HRSGs. Chemistry is
unique.
Revision Date:
9/25/2014
Tags:
221112 - Fossil Fuel
化石燃料,
221112 - Fossil Fuel
化石燃料,
HDR Engineering, Chemical, Consulting
Questions answered regarding HRSG water/steam chemistry and prevention of
corrosion and fouling in steam generators. Even seemingly minor issues have been
known to cause failures that cost power producers millions of dollars and in
some cases even claimed lives. This is the ultimate cost.
Revision Date:
9/25/2014
Tags:
221112 - Fossil Fuel
化石燃料,
221112 - Fossil Fuel
化石燃料,
Kiewit, Chemical, Consulting
Power Plant Chemicals Overview by Bob
McIlvaine - Hot Topic Hour September 25, 2014
Bob McIlvaine reviewed some of the challenges.
Revision Date:
9/25/2014
Tags:
221112 - Fossil Fuel
化石燃料,
221112 - Fossil Fuel
化石燃料,
McIlvaine, Chemical, Consulting