CONTINUATION OF PACIFICORP NOx ANALYSIS
Moving forward with Session 3
Session 3 will cover the back end technologies. Utilities participating in the
2nd session liked the opportunity of interfacing with PacifiCorp who has similar
boilers and problems. The fact that the utility can not only hear presentations
for the experts but also the questions or challenges to those presentations from
other experts is unique. Most importantly all of the material is organized in
the 44I Power Plant Air Quality Decisions (Power Plant Decisions Orchard). This
is free of charge to any utility employee, so you can register for the free
services as well as the next webinar. Others can register free of charge for the
webinar, but the 44I is $1600/yr.
Lotox, catalytic filters, H202, SNCR and In-duct SCR will be examined in the
Third Session
We have yet to hear from suppliers of catalytic baskets for APH. The options for
hydrogen peroxide and ozone will also be discussed. Some H2O2 testing was done
at Jim Bridger. However, both H2O2 and ozone generation rely on a downstream
scrubber for NO2 capture. The lack of success at Jim Bridger where limestone is
used may not apply at Hunter and Huntington where lime is used. There is also
the question of conversion of H2O2 to O3 prior to reaction with the NO. This is
not a problem with ozone. Some work with H2O2 indicates it can be used along
with urea in the firing zone where it will be an additional effective reductant.
So these are some of the questions remaining. Bob Crynack will be in the
discussion and can address some of the H2O2 questions
We have presentations by AECOM on the Linde Lotox systems in our PPAQD. We have
contacted DuPont to provide their advice base on installation of LoTox at a
number of refineries and industrial plants. Both Filtration Group and AFT (FLS)
have been contacted relative to utilizing catalytic filters
Keith Moore will talk briefly about the catalytic burner which greatly reduces
fuel NOx
Lots of insights from Speakers in the Second Session
In the second session on July 19, presentations were made by Jeff Williams of
Emerson, Peter Spinney of GE, Bin Xu of Doosan and Don Hatch of Siemens relative
to controls. The options for optimization include both the model-based as well
as the neural network learning approach. Each of the presenters referenced
successful case studies and clear evidence that NOx can be reduced by 4 to 20
percent.
We want opinions and recommendations from our readers on many questions. The
SootOpt GE approach cycles the soot blower operation based on results. How
important is it to have this kind of focus? The presenters referenced laser and
acoustic instrumentation to determine the distribution of oxygen and CO. How
important is the more precise measurement? What are the advantages and
disadvantages of each of the approaches? GE recently purchased Neuco. So they
must buy into the neural networks and learning-based operation of the soot
blowers and other variables. Doosan is another boiler supplier who weighed in.
What do Babcock & Wilcox, Foster Wheeler and MHPS utilize for retrofits and new
boilers?
How does what we are learning about solving PacifiCorp’s problems apply to
boilers in the rest of the world? We have included a paper in the intelligence
system on the successful use of the Siemens optimizer at a large Chinese
supercritical plant. Is the ROW behind or ahead of the U.S. in optimizing boiler
operations? We have included a Yokogawa paper on their successful application of
the TDL. What is their experience in Europe and Asia?
The third session will focus on back-end solutions such as SNCR, ozone, hydrogen
peroxide and in-duct catalyst. One area for discussion will be the adaptability
of the optimization systems to performance on the back end. The optimizer
speakers addressed the degree to which their systems could cope with changing
conditions. One additional input will be the outlet NOx after, for example, the
hydrogen peroxide addition. If the efficiency still needs to be raised, do you
add more hydrogen peroxide in the back end, urea in the front end or is it your
damper settings on the combustion air?
Dale Pfaff of Fuel Tech provided more details on the combined combustion
modification and SNCR approach. We have included a Doosan paper with some
information on European systems using SNCR reburn and other modifications. We
still need to hear from LP Amina who has a number of systems in China.
We would hope that the crowd problem solving that we have initiated results in
options that have not even been considered before. We have queried a number of
people and asked them to address the following potential option.
The amount of urea added in the boiler is limited by the considerations of
ammonia slip. How much can efficiency be improved if higher ammonia slip is
acceptable? Sterling Gray of AECOM has presented data showing that sodium
bisulfite addition ahead of the air preheater reduces the acid dew point and
eliminates APH problems related to ammonium sulfate build-up. The main purpose
is to provide conditions which allow the expansion of the air heater and improve
boiler efficiency. The question is what impact would this have on NOx? The
higher efficiency means lower Btu input per kWh and therefore lower NOx. Bigger
potential is to improve SNCR efficiency with more urea. Bin Xu of Doosan
responded to the query with this qualification. If sufficient urea is already
being added, then more urea just results in more ammonia slip. But we must be
missing something here in that the SNCR efficiency is low under any
circumstances. One would think there is room for improvement.
Relative to the buildup in the air preheater, would the addition of lime be a
positive or negative factor? Another concern is the blue haze potential. But
with the baghouse and scrubber downstream, this should not be a problem.
McIlvaine has reported on good reduction in the baghouse with additives but not
much success in the scrubber.
A fundamental question for PacifiCorp is the flexibility relative to the
guideline of measurement in lbs/MMBtu of fuel input. If you improve efficiency,
you need fewer BTUs of fuel to achieve the same electrical output. Many more
recent EPA regulations have been based on emissions per MWH output. Is there
flexibility to take into account NOx reduction by improving efficiency? The EPA
Federal Register document which is included in the PPAQD shows the tons per year
of NOx which will be reduced with SNCR and SCR but did that take into account
efficiency increases?
Doosan combines Reburn with SNCR and Combustion Modifications
The high cost of SCR has resulted in demand for other more cost-effective NOx
compliance measures including fuel selection, low-NOx burners (LNB), over-fire
air (OFA) systems, combustion optimization systems, selective non-catalytic
reduction (SNCR) technology, and in-duct or advanced SNCR technology. While
individually these measures cannot deliver the NOx reduction levels of a
traditional full-flow SCR system, in combination with one another they can
deliver significant reductions in NOx emissions at a fraction of the installed
cost of an SCR, according to Doosan.
In coal-fired power plants, the FGR can inhibit the combustion efficiency to an
unacceptable degree, though FGR injected elsewhere and used as a reheat steam
temperature control measure can offer an additional NOx reduction benefit. FGR
technology alone may achieve NOx reduction on the order of 20 percent, at an
installation cost of $3 to $5 per kW.
Combustion optimization ties combustion control methods together to produce a
consistent, controllable furnace combustion process. Often OFA systems and LNB
are installed and initially tuned to provide the best NOx performance at a given
load on a particular fuel. But when a variable changes (unit operating profile,
fuel source, weather), the unit's NOx performance decreases. When this happens,
there is no permanently installed analysis instrumentation like that used in the
initial setup of the OFA system and burners. Because of this, the plant
operations and maintenance staff cannot retest and further optimize the
equipment in a timely or efficient manner. To assist in the maintenance of NOx
performance combustion optimization systems that utilize online gas temperature
monitoring and analysis, systems that are integrated into the boiler control
systems can help to maximize NOx control performance in response to changing
conditions.
SNCR is a method used to reduce NOx by injecting either ammonia or urea into the
boiler furnace at locations where the flue gas is between 1,600 and 2,100°F.
Effective SNCR is dependent upon sufficient reaction time within the flue gas
temperature window and adequate mixing of the reagent with the flue gas.
It is critical to design an SNCR system to operate within this temperature
window. If the temperature is too high, the ammonia will decompose to produce
additional NOx. If the temperature is too low, the reaction will not occur,
resulting in ammonia slip. The slip will react with sulfur from the fuel to form
ammonium sulfate and ammonium bisulfate, which has a tendency to condense on the
cooler surfaces of the air heater and can cause significant loss of efficiency,
in addition to mechanical damage, according to Doosan.
Bob McIlvaine would like to pursue this further. If lime is added ahead of the
air preheater to reduce the acid dew point and to allow the air preheater to be
extended and additional efficiency maintained, then NOx is reduced just due to
efficiency increases. The novel question is whether greater NOx reduction can be
achieved by higher ammonia slip. If the maintenance aspects of ammonia slip are
eliminated due to the lime addition, then higher NOx removal can be obtained.
Will this be a significant efficiency improvement?
Can we correlate ammonia slip and SNCR efficiency? Will the downstream baghouse
capture any lime and slip and ensure there is no blue plume coming out the
stack? Or will the lime scrubber eliminate any residual slip (not likely if it
is already a blue plume) with submicron particle size?
Reply from Bin Xu of Doosan
It depends on the design and operating margin of the SNCR. For an existing SNCR,
its efficiency relies on the optimum temperature window. If the ammonia
utilization already approaches its equilibrium, then increasing the ammonia
injection may only result in higher ammonia slip.
Historically, the need to control reagent injection to meet the constraints of
temperature, mixing, and reaction time has limited SNCR effectiveness and
application in utility-scale, coal-fired boilers where gas temperatures are
relatively high and temperature profiles are dynamic. However, recent
developments in acoustic- and laser-based furnace gas temperature measurement
systems have allowed accurate real-time mapping of furnace temperature profiles,
which can be integrated into the SNCR control scheme, allowing reliable NOx
reductions ranging from 30 to 50 percent.
SNCR has significant economic advantages over SCR. It is a simpler system, it
does not require an expensive catalyst, and can be installed within a regular
plant outage schedule. Installing an SNCR system on a utility boiler typically
costs $10 to $20 per kW. Doosan offers the following comparison of technologies.
Comparison of NOx Reduction Capabilities vs. Specific Cost for Available
Technologies
Nominal NOx Reduction Rate Estimated Installed Cost ($/kW)
low high low high
Baseline 0% 0
LNB 30% 50% 5 10
OFA 20% 45% 5 10
Reburn 15% 30% 5 10
FGR 10% 20% 3 5
SNCR 25% 50% 10 20
LNB+OFA 44% 73% 10 20
LNB+FGR 37% 60% 8 15
LNB+SNCR 48% 75% 15 30
LNB+OFA+FGR 50% 78% 13 25
LNB+OFA+Reburn 52% 81% 15 30
LNB+OFA+SNCR 58% 86% 20 40
LNB+OFA+FGR+SNCR 62% 89% 23 45
LNB+OFA+Reburn+SNCR 64% 90% 25 50
SCR 80% 90% 100 200
T Plant Performance Improvements by enhanced combustion through Laser-based
Optimization
Don Hatch of Siemens explained the benefits of the optimizer system using the
Zolo TDL. Boiler efficiency is increased through (1) O2 reduction; (2) improve
and balance combustion; (3) balance temperature distribution; (4) balance O2
distribution; and (5) continuous adaptation to varying boiler conditions. The
optimizer modules are (1) laser-based measuring technology; (2) distribution
calculation based on computer aided tomography (CAT) procedure; and (3)
combustion optimization controls. TDL sensors from Zolo measure O2, CO, and
temperature at multiple grid points. The combustion optimizer controls are (1)
fire ball centering by modifying secondary auxiliary air; (2) combustion
balancing by modifying secondary boundary air; (3) O2 distribution balancing by
SOFA; and (4) O2 reduction by modifying the O2 set point.
Emerson SILO Optimization can achieve Emission Levels as low as 0.1 lbs/MMBtu
Jeff Williams was asked in the previous session whether the company had systems
which were achieving low emission levels with the Emerson optimization system.
In this session Jeff confirmed that Emerson has achieved low levels with their
SILO optimization system. SILO optimization tasks include: (1) measured
disturbances including boiler load, coal mills, configuration; (2) non-measured
disturbances including coal calorific value, biomass co-firing, quality of
mills, grinding; (3) control signals including secondary air dampers, OFA, SOFA,
COFA, O2, coal feeders, RH steam temperature, SH steam temperature, CO, NOx, O2
balance. SILO has advantages over model predictive control (MPC) including
adapting to different operating points and process change. There is no need for
model creation. Expert knowledge about the process can be implemented even if it
is not precise.
Click here to Register for the Webinar
Upcoming Hot Topic Hours
DATE HOT TOPIC HOUR AND DECISION GUIDE SCHEDULE
The opportunity to interact on important issues
August 2, 2016
11:00am CDT NOx Control for PacifiCorp: Back end NOx Control
Discussion of options for PacifiCorp to comply with new NOx removal requirements
for four 350 MW coal-fired generators operating in Utah. This third webinar will
consider the range of options such as peroxide, ozone, and catalysis, to reduce
emissions to 0.06 lbs/MMBtu.
Click here for more information
August 25, 2016
10:00am CDT
Markets Oil, Gas, Refining - Supply and demand; impact on flow control and
treatment products; regional impacts e.g. subsea in North Atlantic vs. shale in
the US vs. Oil Sands in Canada.
TBA
Markets Food - Analysis of 12 separate applications within food and beverage
with analysis of valve, pump, compressor, filter, analyzer and chemical options;
impact of new technologies such as forward osmosis.
TBA
Markets Municipal Wastewater - Quality of pumps, valves, filters, and analyzers
in Chinese and Asian plants; new pollutant challenges; water purification for
reuse.
TBA
Markets Mobile Emissions - Reduction in CO, VOCs, and particulate in fuels,
oils, and air used in on and off road vehicles; impact of RDE and failure of NOx
traps and the crisis in Europe created by the focus on clean diesel.
Utility E-Alert Tracks Billions of Dollars of New Coal-fired Power Plants on a
Weekly Basis
Here are some headlines from the Utility E-Alert.
UTILITY E-ALERT
#1282 – July 22, 2016
Table of Contents
COAL – US
• Kemper Power Plant in Mississippi producing Gas from Coal
• Endicott 55 MW Coal-fired Power Plant may have Buyer
• Great River Energy to retire Stanton Station
• FirstEnergy to deactivate Units at Oregon and Stratton, Ohio Power Plants
COAL – WORLD
• China Emissions Projects
• India approves installation of 1980 MW Thermal Power Project
• Bangladesh awards $2.5 Billion Coal-fired Power Project to Malaysia
The 41F Utility E-Alert is issued weekly and covers the coal-fired projects,
regulations and other information important to the suppliers. It is $950/yr. but
is included in the $3020 42EI Utility Tracking System which has data on every
plant and project plus networking directories and many other features.
You can register for our free McIlvaine Newsletters at:
http://home.mcilvainecompany.com/index.php?option=com_rsform&formId=5.
Bob McIlvaine
President
847-784-0012 ext. 112
rmcilvaine@mcilvainecompany.com
www.mcilvainecompany.com