1

TECHNICAL REPORT

“Ottumwa Manual Balancing Demonstration”

Alliant Energy Ottumwa Generating Station

with Electric Power Research Institute and Zolo Technologies

Demonstration: July 22 -27, 2012 Authors / Contributors:

(1) S. Martz (2) R. Himes (3) E. Huelson

(1) Alliant Energy, Ottumwa Generating Station, Ottumwa, Iowa (2) Electric Power Research Institute, Palo Alto, California (3) Zolo Technologies, Inc., Boulder, Colorado Report Issued: August 6, 2012 Rev.A Issued: October 17, 2012

2

Table of Contents Executive Summary ............................................................................................................................................... 3 The Problem ........................................................................................................................................................... 4 Background Data .................................................................................................................................................... 4

ZoloBOSS .......................................................................................................................................................... 5 Tuning Strategies ................................................................................................................................................... 6

Equilibrating East and West ................................................................................................................................ 7 Balancing Combustion ........................................................................................................................................ 7

Manual Balancing Exercise .................................................................................................................................. 10 Conclusion ........................................................................................................................................................... 14 Recommendations for ZoloBOSS Integration........................................................................................................ 14

3

Executive Summary Electric Power Research Institute and Zolo Technologies conducted a demonstration project at Ottumwa Power Station to use ZoloBOSS data and standard plant information to improve combustion performance. Project Objectives:

• Reduce excess O2 set points while maintaining NOx and CO limits. • Achieve superheat and reheat steam temperature targets of 1000 F. • Produce tuning strategies for balancing combustion to achieve NOx, CO and steam temperature objectives

at reduced excess O2. The table below summarizes results after manually tuning the boiler using ZoloBOSS data. The tuning reduced excess O2, moved air from the East Furnace to the West Furnace, and then balanced in-furnace CO.

* EPRI, “Heat Rate Awareness”, Table 4-2 Heat Rate and Generation Impacts of Controllable Losses for a Reheat Unit, 1997 Overview of Results:

• Reduced Excess O2 by 0.75%. • Maintained CO limits. • NOx decreased by 5% (78 to 74ppm). • Superheat and reheat steam temperatures increased from 998 to 1004F and 983 to 1001F respectively. • Auxiliary Power requirements (fan load) decreased by 2.4 MW • Total Heat Rate Reduction (Dry gas loss + Aux Power + RH/SH temp) of 92.9 btu/Kwh or ~0.9%

With further verification and refinement the tuning strategies can be integrated into manual and closed-loop combustion control to achieve sustained boiler operation while maintaining emission and steam temperature targets.

Time

NOx

(ppm)

CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

SH Split West-East (F)

Reheat Temp (F)

RH Split West-East (F)

Baseline - Optimizer Control 7/27 8:00 - 10:00 78.2 72 3.00 40.40 997.7 10.1 983.0 32.7Move air from East to West Furnace 7/27 11:15 - 12:15 73.0 630 2.24 37.43 997.3 14.2 995.0 14.7Balance CO within each Furance 7/27 2:15 - 4:15 74.3 175 2.24 37.96 1004.1 -0.1 1001.0 6.6

Heat Rate Impact (Btu/kWh) * 24.2 34.4 11.6 - 22.7 -Total Heat Rate Reduction (Btu/kWh) 92.8

4

The Problem Ottumwa has three primary goals of boiler operation:

1) Operate within regulatory NOx limits. 2) Operate within regulatory CO limits. 3) Maintain superheat and reheat temperatures.

Since a recent upgrade to plant controls, the NeuCo CombustionOpt optimizer has been successfully maintaining NOx and CO to within plant targets, however reheat steam temperatures are consistently below operational design targets of 1000F. The lack of reheat temperatures is especially problematic as a planned turbine side upgrade assumes adequate temperatures. To help achieve NOx, CO and temperature targets simultaneously, the plant has available a ZoloBOSS system producing in-furnace distributions of temperature, O2, CO and H2O at the bull nose. The purpose of collecting this data is to allow the plant to balance combustion within the furnace and get closer to achieving all of the above objectives. The next step in this process is to determine how to integrate and interpret this data to sustainably produce a benefit for the plant. This effort aims to demonstrate how to integrate ZoloBOSS data into plant operations to reliably minimize NOx and CO while maintaining superheat and reheat steam temperatures. Additionally, results of the demonstration will be used to determine a strategy to integrate real-time boiler balancing into the CombustionOpt system so that Ottumwa can achieve sustained benefits.

Background Data The following graphic provides the orientation of the sensors and controls within the Ottumwa unit. Ottumwa is a twin-tangential fired unit burning Powder River Basin coal with a nameplate capacity of 726 MW. The unit has seven burners per column surrounded by Aux-air. Two levels of OFA exist above the burners, the lower OFA level is corner fired while the upper level fires with eight ports on the rear of the boiler only. While no furnace division wall exists, for purposes of the demonstration the west and east sides of the furnace are defined as West Furnace and East Furnace respectively.

5

ZoloBOSS The ZoloBOSS combustion monitor is provided by Zolo Technologies and consists of a laser-based combustion sensor designed for the ultra-harsh combustion environment of a coal powered furnace. The ZoloBOSS uses tunable diode laser absorption spectroscopy (TDLAS), laser multiplexing, and tomographic algorithms to generate two-dimensional maps of boiler conditions including temperature, O2, CO and H2O concentrations. Measurements are obtained directly in the furnace and in real time. Visibility into the combustion zone makes real time combustion balancing possible. ZoloBOSS Layout at Ottumwa: The ZoloBOSS at Ottumwa includes eight front to rear paths, four paths on the West Furnace and four paths on the East Furnace, and five horizontal paths that traverse the length of the boiler. The paths are located directly below the bullnose of the boiler as illustrated below.

6

Tuning Strategies In typical combustion, furnace imbalances cause regions of high NOx and/or high CO even with an appropriate excess O2 set point. This is particularly the case with CO which rises dramatically as combustion becomes locally fuel rich. Alternatively, if one has balanced combustion in the furnace, overall NOx and CO are minimized for a given excess O2 set point. Thus, as one achieves balanced combustion, excess O2 can be reduced, in Ottumwa’s case to maintain reheat temperatures and NOx, without dramatically spiking the CO in fuel lean regions of the furnace.

This section will discuss techniques for:

CO Measured by ZoloBOSS CO is predominantly generated by the West and East sidewalls

West Furnace East Furnace

7

1) Equilibrating each furnace. 2) Balancing combustion within each furnace.

These techniques can be used by Ottumwa for real time balancing of combustion either by a plant engineer or operator, or through integration into the CombustionOpt optimizer. Equilibrating East and West

• Objective: Determine a technique for moving air from the West Furnace to the East Furnace or vice versa to minimize superheat, reheat, and O2 imbalances.

• Controls manipulated: Rear OFA dampers on the West or East Furnace were increased to test their influence on air and temperature distributions.

• Test Results: The following correlations were found with Rear OFA damper manipulations.

• Conclusion: By manipulating the West or East Rear OFA dampers one can equilibrate West Furnace to East Furnace O2 and temperature deviations as measured by O2 probes, ZoloBOSS O2 and Temp, and Steam temperatures. Once the furnaces are equilibrated, one can proceed to balance each furnace section.

• CombustionOpt Logic: The following functional control logic is suggested as a strategy to sustainably balance West and East air distributions.

o Controls: Rear OFA Dampers groupBA_W = (ROFA1, ROFA2, ROFA3, ROFA4)_level A&B groupBA_E = (ROFA5, ROFA6, ROFA7, ROFA8) _level A&B

o Indicators: ZB_W_O2Avg = Average(ZoloBOSS O2 (P1, P2, P3, & P4)) ZB_E_O2Avg = Average(ZoloBOSS O2 (P5, P6, P7, & P8)) Probe_W_O2Avg = West_O2 Probe_E_O2Avg = East_O2

o Logic: For a 30 minute window If (ZB_W_O2Avg - ZB_E_O2Avg) > 0.2% & If (Probe_W_O2Avg - Probe_E_O2Avg)

> 0.2%, then +5%bias groupBA_W&-5% biasgroupBA_E If (ZB_W_O2Avg - ZB_E_O2Avg) < -0.2% & If (Probe_W_O2Avg - Probe_E_O2Avg)

< -0.2%, then -5%bias groupBA_W& +5% bias groupBA_E • Additional control possibilities: Boiler air movement was accomplished in this demonstration by moving

West and East Rear OFA dampers. One could get a similar balanced distribution by moving up/down West and East OFA levels, Aux air levels, and/or fuel air. These controls could be substituted for Rear OFA at Ottumwa’s discretion and may provide an advantage if Rear OFA is at its upper limit due to attempts to stage combustion.

Balancing Combustion

• Objective: Determine a technique for balancing combustion within each furnace. • Control manipulated: OFA damper corners were increased or decreased to reduce CO hot spots and/or O2

reduction zones as measured by the ZoloBOSS.

West East West East West East West East West East 40% Bias to Rear OFA level 2 West Side 3.28 2.76 4.66 4.17 2465 2485 1002.8 1002.8 996.7 974.3 20% Bias to Rear OFA level 2 West Side 3.06 2.98 4.09 4.27 2512 2493 1005.1 997.1 993.5 967.0 0% Bias to Rear OFA level 2 2.78 3.11 4.12 4.43 2518 2465 1003.7 979.8 990.6 959.8 20% bias to Rear OFA level 2 East side 2.61 3.41 3.81 4.51 2530 2446 1007.4 977.8 995.1 973.1

Reheat Temp (F)Superheat Temp (F) O2 Probes (%) Zolo O2 (%) Zolo Temp (F)

8

• Test Results: Although a formal testing suite was not conducted, the following template was determined from boiler documentation and manual tuning efforts. This template suggests that air introduced at any OFA corner will be observed at the ZoloBOSS grid 90º from the introduction of the air. This 90º rotation is due to the swirl of the dual T-fired unit and the height of the OFA ports in the combustion zone relative to the ZoloBOSS grid at the bullnose. Air introduced at an OFA port in the West Furnace will be observed +90º (clockwise) whereas on the East Furnace will be observed -90º (counterclockwise). This tuning strategy provides a technique for mitigating high in-furnace CO or O2 by adding or reducing air at the proper locations.

• Conclusion: By manipulating OFA damper corners one can minimize CO and O2 hot spots within each furance.

• CombustionOpt Logic: The following functional control logic is suggested as a strategy to sustainably balance west and east air distributions.

o Controls: OFA Dampers OFA_A = (OFA_A_levelA, OFA_A_levelB) OFA_B = (OFA_B_levelA, OFA_B_levelB) OFA_C = (OFA_C_levelA, OFA_C_levelB) OFA_D = (OFA_D_levelA, OFA_D_levelB) OFA_E = (OFA_E_levelA, OFA_E_levelB) OFA_F = (OFA_F_levelA, OFA_F_levelB) OFA_G = (OFA_G_levelA, OFA_G_levelB) OFA_H = (OFA_H_levelA, OFA_H_levelB)

o Indicators: ZB_WO2Avg = WestFireball_O2Avg ZB_WCOAvg = WestFireball_COAvg ZB_EO2Avg = EastFireball_O2Avg ZB_ECOAvg = East Fireball_COAvg

9

o Logic: For a 30 minute window West Side

• ZB_WMax_CO = Max(ZB_WA_CO, ZB_WB_CO, ZB_WC_CO, ZB_WD_CO) • ZB_WMaxCO_Loc = Identified highest quad (i.e. ZB_WA_CO or ZB_WB_CO) • ZB_WMax_O2 = Max(ZB_WA_O2, ZB_WB_O2, ZB_WC_O2, ZB_WD_O2) • ZB_WMaxO2_Loc = Identified highest quad (i.e. ZB_WA_O2 or ZB_WB_O2) • OFA_CO_Loc = ZB_WMaxCO_Loc - 90º • OFA_O2_Loc = ZB_WMaxO2_Loc - 90º

• If((( ZB_WMax_CO - ZB_WCOAvg)/ZB_WCOAvg – 1) > 0.2&((ZB_WMax_O2 - ZB_WO2Avg)/ZB_WO2Avg – 1) > 0.2) then +5% bias OFA_CO_Loc& -5% bias OFA_O2_Loc

• Examples: o If CO is 35% higher in quadrant ZB_WA than the average West

Furnace CO and O2 is 25% higher than the average West Furnace O2 in ZB_WB then a +5% bias would be applied to OFA_D and a -5% bias would be applied to OFA_A.

o If CO is 25% higher in quadrant ZB_WD and O2 is 15% higher in ZB_WB then there would be no change as O2 is not greater than 20%.

East Side • ZB_EMax_CO = Max(ZB_EE_CO, ZB_EF_CO, ZB_EG_CO, ZB_EH_CO) • ZB_EMaxCO_Loc = Identified highest quad (i.e. ZB_EE_CO or ZB_EF_CO) • ZB_EMax_O2 = Max(ZB_EE_O2, ZB_EF_O2, ZB_EG_O2, ZB_EH_O2) • ZB_EMaxO2_Loc = Identified highest quad (i.e. ZB_EE_O2 or ZB_EF_O2) • OFA_CO_Loc = ZB_EMaxCO_Loc + 90º • OFA_O2_Loc = ZB_EMaxO2_Loc -+ 90º

• If ((( ZB_EMax_CO - ZB_ECOAvg)/ZB_ECOAvg – 1) > 0.2 & ((ZB_EMax_O2 - ZB_EO2Avg)/ZB_EO2Avg – 1) > 0.2) then +5% bias OFA_CO_Loc& -5% bias OFA_O2_Loc

ZB_WA_O2 = Avg (ZB_O2 ( x6_y7, x6_y14, x20_y7, x20_y14)) ZB_WA_CO = Avg (ZB_CO ( x6_y7, x6_y14, x20_y7, x20_y14))

ZB_WB_O2 = Avg (ZB_O2 ( x6_y31, x6_y36, x20_y31, x20_y36)) ZB_WB_CO = Avg (ZB_CO ( x6_y31, x6_y36, x20_y31, x20_y36))

ZB_WC_O2 = Avg (ZB_O2 ( x34_y31, x34_y36, x43_y31, x43_y36)) ZB_WC_CO = Avg (ZB_CO ( x34_y31, x34_y36, x43_y31, x43_y36))

ZB_WD_O2 = Avg (ZB_O2 ( x34_y7, x34_y14, x43_y7, x43_y14)) ZB_WD_CO = Avg (ZB_CO ( x34_y7, x34_y14, x43_y7, x43_y14))

ZB_EE_O2 = Avg (ZB_O2 ( x49_y7, x49_y14, x58_y7, x58_y14)) ZB_EE_CO = Avg (ZB_CO ( x49_y7, x49_y14, x58_y7, x58_y14))

ZB_EF_O2 = Avg (ZB_O2 ( x49_y31, x49_y36, x58_y31, x58_y36)) ZB_EF_CO = Avg (ZB_CO ( x49_y31, x49_y36, x58_y31, x58_y36))

ZB_EG_O2 = Avg (ZB_O2 ( x73_y31, x73_y36, x87_y31, x87_y36)) ZB_EG_CO = Avg (ZB_CO ( x73_y31, x73_y36, x87_y31, x87_y36))

ZB_EH_O2 = Avg (ZB_O2 ( x73_y7, x73_y14, x87_y7, x87_y14)) ZB_EH_CO = Avg (ZB_CO ( x73_y7, x73_y14, x87_y7, x87_y14))

10

• Additional control possibilities: For the manual balancing exercise CO spots were mitigated through OFA

movements. Alternatively one could shift combustion centering with lower auxiliary air and fuel air dampers. Air introduced lower in the furnace will rotate to a greater degree than air introduced at OFA. Initial exercises indicate a 180º rotation from the upper Aux air ports and a 225º rotation from the lower Aux air ports. This is graphically described below but should be verified prior to final integration.

Manual Balancing Exercise On July 27, 2012 EPRI, Ottumwa, and Zolo conducted an effort to demonstrate NOx and CO reduction while improving reheat steam temperatures. The demonstration resulted in reduced NOx, CO and improved steam temperatures. This was accomplished by decreasing fuel air, lowering excess O2, evening out air flows to the West and East Furnace, and then balancing each furnace. The steps and results of the manual balancing exercise will be reviewed below. Performance Indicators Results of each step in the combustion balancing demonstration are given in the table below. The West to East Furnace Split indicators provides the difference between the West Furnace and East Furnace as measured by ZoloBOSS CO and O2 and superheat and reheat temperatures. The In-Furnace Balance indicators provides the balance within each furnace zone as indicated by the Standard Deviation of the O2 and CO ZoloBOSS paths on each side of the boiler. Minimizing the West to East Furnace Split and In-Furnace Balance indicators provides for improved furnace balance and in better Performance Results.

• Step 1: CombustionOpt baseline performance 8:00 – 9:50

o Objective: Provide baseline data for current boiler performance. o Actions: Collect two hours of baseline performance data

Step

Stack NOx

(ppm)

Stack CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

Reheat Temp (F)

Zolo O2 West -East

(%)

Zolo CO West -East

(%)

SH Split West-East

(F)

RH Split West-East

(F)

Zolo O2 Stdev West

Zolo O2 Stdev East

Zolo CO Stdev West

Zolo CO Stdev East

1 78.2 72.0 3.00 40.4 998 983 -0.40 666 10.1 32.7 0.88 0.83 2342 18972 74.3 56.2 2.79 39.4 1000 996 -0.53 1661 15.8 10.8 1.05 0.74 3043 16823 73.0 83.0 2.64 38.4 1001 996 -0.39 939 10.0 15.9 0.99 0.80 2835 21204 72.6 115.4 2.51 37.8 1007 1003 -0.12 1914 1.2 16.8 1.08 0.74 3339 18465 69.1 311.4 2.24 37.0 1008 1003 -0.04 1262 -3.6 3.5 0.63 0.64 2016 15206 73.0 630.1 2.24 37.4 1004 1002 0.34 -593 4.6 3.8 0.86 0.69 2264 28227 74.3 175.3 2.24 38.0 1004 1001 -0.03 397 -0.1 6.6 0.65 0.70 1987 20328 73.7 140.1 2.29 38.1 1004 996 -0.09 1673 3.0 24.9 0.66 0.69 2031 1815

Performance Results West to East Furnace Split In-Furnace Balance

11

Note: For all tomography plots displayed, Temp 2000-2800F, CO 2,000-16,000, O2 1.0% -8.0%. Blue = low, Green = Med, Red = High, Black = Max

• Step 2: Reduce fuel air dampers and Excess O2 10:00 – 10:30 o Objective: Reduce air to the lower furnace to increase staging and decrease NOx o Actions:

CombustionOpt system turned off. Reduce Fuel Air dampers to 20% open on burners 102-107. Reduce Excess O2 by 0.25%.

o Result: NOx and CO reduction, increase in reheat and steam temps, in-furnace CO spiking on West Wall.

• Step 3: Reduce Excess O2 10:30 – 10:45 o Objective: Reduce NOx by reducing Excess O2. o Actions: Reduce Excess O2 by 0.25%. o Result: NOx slightly decreased, CO increased, and in-furnace CO hot spot still present.

• Step 4: Reduce Excess O2, reduce West to East Furnace Split 10:45-11:00 o Objective: Reduce NOx, improve steam temps, and improve the West to East O2 distribution. o Actions:

Reduce Excess O2 by 0.25%.

Temp CO O2

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

Step

Stack NOx

(ppm)

Stack CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

Reheat Temp (F)

Zolo O2 West -East

(%)

Zolo CO West -East

(%)

SH Split West-East

(F)

RH Split West-East

(F)

Zolo O2 Stdev West

Zolo O2 Stdev East

Zolo CO Stdev West

Zolo CO Stdev East

1 78.2 72.0 3.00 40.4 998 983 -0.40 666 10.1 32.7 0.88 0.83 2342 18972 74.3 56.2 2.79 39.4 1000 996 -0.53 1661 15.8 10.8 1.05 0.74 3043 1682

Performance Results West to East Furnace Split In-Furnace Balance

Temp CO O2

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

Step

Stack NOx

(ppm)

Stack CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

Reheat Temp (F)

Zolo O2 West -East

(%)

Zolo CO West -East

(%)

SH Split West-East

(F)

RH Split West-East

(F)

Zolo O2 Stdev West

Zolo O2 Stdev East

Zolo CO Stdev West

Zolo CO Stdev East

2 74.3 56.2 2.79 39.4 1000 996 -0.53 1661 15.8 10.8 1.05 0.74 3043 16823 73.0 83.0 2.64 38.4 1001 996 -0.39 939 10.0 15.9 0.99 0.80 2835 2120

Performance Results West to East Furnace Split In-Furnace Balance

Temp CO O2

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

In-furnace CO spot

12

+5% Bias to all Level B OFA West Furnace dampers (Corn ABCD). o Result: NOx slightly decreased, reheat temperatures increased, temperature &O2 balance improved.

Stack CO continuing to rise and in-furnace CO spot still present.

• Step 5: Reduce Excess O2, reduce West to East Furnace Split 11:00 – 11:15 o Objective: Reduce Excess O2 to further reduce NOx and improve steam temperatures and further

reduce the East to West Furnace Split. o Actions:

Rear OFA level B +20% West Furnace, -20% East Furnace. Reduce Excess O2 by 0.25%.

o Result: Excess O2 and reheat temperature splits minimized. The temperature of the furnace gasses increased with the reduction in Excess O2.

• Step 6: Balance in-furnace combustion 11:15 – 12:15 o Objective: Mitigate the West Wall CO hot spot. o Actions: OFA level A - A to 95%, D to 90%, E & H to 95%. o Result: While the movements did reduce CO on the West Wall, the movements also increased the

formation of CO on the East Wall.

Step

Stack NOx

(ppm)

Stack CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

Reheat Temp (F)

Zolo O2 West -East

(%)

Zolo CO West -East

(%)

SH Split West-East

(F)

RH Split West-East

(F)

Zolo O2 Stdev West

Zolo O2 Stdev East

Zolo CO Stdev West

Zolo CO Stdev East

3 73.0 83.0 2.64 38.4 1001 996 -0.39 939 10.0 15.9 0.99 0.80 2835 21204 72.6 115.4 2.51 37.8 1007 1003 -0.12 1914 1.2 16.8 1.08 0.74 3339 1846

Performance Results West to East Furnace Split In-Furnace Balance

Temp CO O2

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

Step

Stack NOx

(ppm)

Stack CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

Reheat Temp (F)

Zolo O2 West -East

(%)

Zolo CO West -East

(%)

SH Split West-East

(F)

RH Split West-East

(F)

Zolo O2 Stdev West

Zolo O2 Stdev East

Zolo CO Stdev West

Zolo CO Stdev East

4 72.6 115.4 2.51 37.8 1007 1003 -0.12 1914 1.2 16.8 1.08 0.74 3339 18465 69.1 311.4 2.24 37.0 1008 1003 -0.04 1262 -3.6 3.5 0.63 0.64 2016 1520

Performance Results West to East Furnace Split In-Furnace Balance

Temp CO O2

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

Step

Stack NOx

(ppm)

Stack CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

Reheat Temp (F)

Zolo O2 West -East

(%)

Zolo CO West -East

(%)

SH Split West-East

(F)

RH Split West-East

(F)

Zolo O2 Stdev West

Zolo O2 Stdev East

Zolo CO Stdev West

Zolo CO Stdev East

5 69.1 311.4 2.24 37.0 1008 1003 -0.04 1262 -3.6 3.5 0.63 0.64 2016 15206 73.0 630.1 2.24 37.4 1004 1002 0.34 -593 4.6 3.8 0.86 0.69 2264 2822

Performance Results West to East Furnace Split In-Furnace Balance

+

+

+

+

Steadily increasing furnace temp + + + + - - - - + + + + - - - -

+

+

+

+

13

• Step 7: Manual Balancing Test 12:15 – 14:15 o Objective: Reduce CO on the sidewalls and collect Manual Balanced data set. o Actions:

OFA level B – E to 100% H to 90% OFA level A – Decrease C to 25% Decrease F to 25% Movements were primarily designed to pinch air in the center where O2 was high and CO was

low thus forcing air to the sidewalls. Additionally, because the East Wall had slightly higher CO, OFA corners E and H (level B) were opened up to provide more air to this region.

o Result: In-furnace CO was mitigated resulting in reduced stack CO from 620ppm to 175ppm. Additionally, NOx was minimally influenced and superheat and reheat temperatures were all above 1,000 F.

• Step 8: Lower burner tilts14:15 – 15:00 o Purpose: Quick final test to verify if reheat temperatures could be maintained and NOx could be

reduced by decreasing burner tilts. o Actions: All burner tilts lowered to 60%. o Result: While NOx did slightly decrease, reheat temperatures also decreased by approximately 5

degrees and the steam temperature splits increased.

Temp CO O2

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

Step

Stack NOx

(ppm)

Stack CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

Reheat Temp (F)

Zolo O2 West -East

(%)

Zolo CO West -East

(%)

SH Split West-East

(F)

RH Split West-East

(F)

Zolo O2 Stdev West

Zolo O2 Stdev East

Zolo CO Stdev West

Zolo CO Stdev East

6 73.0 630.1 2.24 37.4 1004 1002 0.34 -593 4.6 3.8 0.86 0.69 2264 28227 74.3 175.3 2.24 38.0 1004 1001 -0.03 397 -0.1 6.6 0.65 0.70 1987 2032

Performance Results West to East Furnace Split In-Furnace Balance

Temp CO O2

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

Step

Stack NOx

(ppm)

Stack CO

(ppm)Excess O2 (%)

Aux Power (MW)

Superheat Temp (F)

Reheat Temp (F)

Zolo O2 West -East

(%)

Zolo CO West -East

(%)

SH Split West-East

(F)

RH Split West-East

(F)

Zolo O2 Stdev West

Zolo O2 Stdev East

Zolo CO Stdev West

Zolo CO Stdev East

7 74.3 175.3 2.24 38.0 1004 1001 -0.03 397 -0.1 6.6 0.65 0.70 1987 20328 73.7 140.1 2.29 38.1 1004 996 -0.09 1673 3.0 24.9 0.66 0.69 2031 1815

Performance Results West to East Furnace Split In-Furnace Balance

Temp CO O2

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

A

B

D

C

E

F

H

G

In-furnace CO reduced on east side but high on west side

+

+

+

+

+

+

+

+

+

+

+

+ - - - -

14

Conclusion The demonstration conducted showed Ottumwa could achieve increased reheat temperatures while minimizing NOx and CO using ZoloBOSS data. Reheat temperatures increased from 983 to 1001 F, superheat temperatures increased from 998 to 1004 F, NOx decreased by 5% and CO, while higher than baseline measurements, was shown to reduce by 2/3 from 630ppm to 175ppm after balancing combustion within the furnace and was contained within regulatory limitations. With proper implementation of the strategies discussed, the plant should be able to maintain steam temperatures while staying in compliance with emission limits.

Recommendations for ZoloBOSS Integration

1. Verify that Zolo OPC communications have been established. 2. Add ZoloBOSS BalanceApp tags to the plant historian. 3. Verify all ZoloBOSS tags are received by the CombustionOpt optimizer. 4. At a fixed load, verify and optimize the tuning strategies suggested above. 5. Integrate West and East distribution strategies into CombustionOpt. 6. Integrate in-furnace balancing strategies into CombustionOpt.