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 $20 per kW. Doosan offers the following comparison of technologies.
Comparison of NOx
Reduction Capabilities vs.
Specific Cost for Available
Technologies |
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|
Nominal NOx Reduction
Rate |
|
|
|
Estimated Installed Cost ($/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 |
NOx Control for
PacifiCorp: Back end NOx
Control |
August 25, 2016
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
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
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which has data on every plant and project plus networking directories and
many other features.
You can register for our free McIlvaine Newsletters at:
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Bob McIlvaine
President
847-784-0012 ext. 112
rmcilvaine@mcilvainecompany.com
www.mcilvainecompany.com