:,.''',JI'(i'11J'-'!/'", t

HOx Control in a Brown Coal-Fired Utility Boiler John E. Hofmann Fuel Tech, Inc., Stamford, CT, USA Joachim von Bergmann Fuel Tech GmbH, Frankfurt, Germany Dr. Dieter Bokenbrink Professor Dr. Klaus Hein Rheinisch-Westf::ilisches Elektrizitiitswerk, Germany

ABSTRACT Rheinisch-Westfalisches Elektrizitatswerk (RWE), initiated a number of tests during 1987 of the NOxOUT(Rl Process for NOx reduction on a 150 MWe brown coalfired boi1er. The NOxOUT Process uses urea and enhancer chemica1s for the reduction ofNOx to molecular nitrogen, water vapor and carbon dioxide. The test objectives nf up to**5~** NOx reduction and NHJ slip of <5 ppm were met over a range of operating conditions. In 1988, acommercial NOxOUT system was subsequently installed on a 75 MWe brown coal-fired boiler to comply with a controlled NOx level of 200 mg/NmJ (approximately 100 ppm). NOx was first reduced to 300 mg/NmJ (approximately 150 ppm) by the use of combustion modifications. Additional NOx reduction down to 180-195 mg/NmJ (approximately 90-98 ppm) has been achieved using the NOxOUT Process. NH slip has been controlled to a level of <2 ppm through the combination 0

## t enhancer chemicals plus selective injection.

INTRODUCTION The Federal Republic of Germany is recognized as aworld leader for the control of sulfur and nitrogen oxides emitted from stationary combustion sources. Acid rain arising from these pollutants is not only affecting human health but is also considered to be one of the major contributors to the damage of the fauna, in particular to forests, and to historical buildings (1, 2). Current legislation and local agreements between industry and the state authorities require that nitrogen oxides be reduced to amaximum of200 mg/NmJ (approximately 100 ppm) for all boilers in e-xcess of 300 MWth by the end of this decade. Rheinisch-Westfalisches ElektriziLitswerk A.G. (RWE) has a total generating capacity of more than 20,000 MW and is the largest utility in the Federal Republic ofGermany. One of the major fuels ofRWE is brown coal which is burned in power stations of about 10,000 MWe installed capacity, with individual units sized up to 600 MWe. The Rhinish brown coal differs distinctly from other fossil fuels such as bituminous coals or lignites. Ahigh moisture level of 55

- 62% on a raw coal basis, a variable ash content of 2 - 20%, and a low nitrogen concentration of 0.3

- 0.4%, are typical for this fuel. Consequently brown coal combustion requires specifically designed fuel preparation circuits and boilers which in conjunction with the fuel properties result in specific flue gas characteristics. The flue gas contains about 20% water vapor resulting in maximum flame temperatures below 1200°C and fairly constant NOx concentrations well below 800 mg/NmJ (approximately 400 ppm).
7A-53

..:..,...... .;'fo!... • .'

. . .._

# '1

1 

### i J It is noteworthy that this fuel Is mostly burned In tangentially fired boilers with jet burners In vertically arranged slits in the walls and/or corners of the combustion chamber. Normal operation with one burner slit always out of service at full load and more slits out of service at partial load differs from the firing mode of higher quality coals and results In aSYl111letric horizontal temperature distributions in the boiler, which has major consequences, as will be discussed later. In order to comply with the NOx emission requirements, after having completed extensive large scale testing and economic evaluation of the selectivecatalytic reduction (SCR) technique (3), and also having reached very promising results with combustion modifications (4), RWE decided to retrofit 37 boilers with a total capacity of 9,300 MWe with alterations to the combustion chamber only. However, there were**~ome** indications that the final goal of a maximum NOx emission of 200 mg/Nrrr' (approximately 100 ppm) may not be achievable for all boilers anct under all operating conditions. Therefore, additional NOx removal principals would be required. This led to large scale tests of various options of injection systems. One major option for RWE was the NOxOUT Process (Rl. The NOxOUT Process licensed through Fuel Tech, N.V. is arelatively low cost retrofitNOx control technology. The NOxOUT Process can be installed with a short downtime and is applicable to a very broad range offuels and boilers. NOx reductions up to**8~** are achievable with this technology (5). The NOxOUT Process can be installed along with combustion modifications to achieve even higher levels ofreduction. Hence, the NOxOUT Process is applicable as aprimary retrofit application and can be applied in conjunction with combustion modifications. The NOxOUT Process is based upon the chemical reaction between nitrogen oxides and urea. 2NO + NH2CONH + 1/2 O ------) 2N + COz + 2Hz O z 2 z The reaction takes place at a temperature of about 925

- l,1000

## e. Research on the urea-based process was initiated in 1976 under sponsorship of the Electric Power Research Institute (6). Starting with the EPRI inventions (7, 8), Fuel Tech has made a number of contributions to improve the application of the technology (9, 11), including broadening and/or shifting of the optimum temperature for reaction by the use of Fuel Tech proprietary chemical enhancers (10, 12, 13, 14). Fuel Tech patented enhancers have also been effective in the control of ammonia formation (11). Airrnonia (NH3), is a by-product of the reaction between NOx and urea that can be formed under certain conditions. Aninonia production is generally undesirable because of the possibility of forming sulfates and bisulfates in the presence of sulfur trioxide and in the contamination of ash, affecting ash disposal options. (Bisulfates have been known to cause fouling in the air preheater area.) The sulfurcontent ofRWE coal**(0.2~** by weight) and the temperatures of the preheater area «330°C) could provide a reactive environment for the formation of bisulfates if there is ammonia present.
TEST PROCEDURES The introduction of the NOxOUT Process to brown coal fired boilers was**c~rr\ed** out in various steps. The first preliminary tests had to show:
at least 30 to**5~** NOx reduction is possible with NH3 emissions, or ·slip·,below 3.8 mg/Nn( (approximately 5 ppm)
7A-54the process is flexible enough to accommodate various combinations of burners in operation the process could cope with load variations down to partial loads of**6~** · i the process is also effective under simulated flue gas conditions which wereexpected aftertheenvisaged installation ofcombustion modificatIons. These tests were carried out on a 150**M~e** boiler (Unit 0, RWE Weisweiler power 

# I ! station, figure 1) during the summer of 1987. Temporary equipment was used for the 0boiler tests which consisted of plastic day tanks for chemical storage, a portable pumping skid, mixing headers for combination of NOxOUT-A solution, enhancers and water, rubber hoses, and distribution headers to split the flow between**multi~le** wall injectors at each of three levels of injection. NOxOUT-A is an aqueous solution of urea and proprietary additives. The first level of injection was into the upper furnace region at 25 meters. The second level was located immediately before the secondary superheater. The third level was located at the top ofthe backpass after the primary superheater. Anumber of different injectors were tried and the final arrangement consisted of sixteen external mix injectors at level one (2 per penetration), nine pin jet injectors at level two, and four internal mix injectors at level three. Steam was used for cooling and atomization for injectors at level one. Air was used for cooling and atomization at levels two and three due to a 1imited availability of steam. After the successful completion of the preliminary tests a full scale demonstration was conducted at the same power station on a 75 MWe boiler (Unit C2, figure 2) during the sumer of 1988. Combustion modifications, installed during the spring of 1988, reduced the NOx emission from about 450 mg/NmJ (approximately 225 ppm) to about 275-325 mg/Nm3 (approximately 140

- 165 ppm) at full load. The major goal of the Unit C2 demonstration was the successful performance of the NOxOUT Process for 4 weeks of continuous operation, durinj which the NOx emission must not exceed the guaranteed level of 200 mg/Nm (approximately 100 ppm). In addition, the process was required to meet this emission limit while maintaining ammonia emissions below 5ppm at all operating conditions. Based on experience from the 0boiler, NOxOUT injectors were installed at three levels; at 19 meters immediately above the burners but below the flue gas recycle and overfire air ports, at 25 meters immediately before the secondary superheater, and at 36 meters at the top of the backpass after the primary )uperheater. There were 12 penetrations at level one, twelve at level two, and four at level three. External mix injectorswere used at all levels. Steam was used as the cooling and atomizing fluid for all injectors.
TEST RESULTS - DBOILER A. Temperature and Composition Profiles Priorto the commencement ofNOxOUT irljection, temperatures weremeasured ateach ofthe three levels of injection. Temperature measurements were made using water cooled suction pyrometers. Analyses for 02' CO and NOx were carried out at the same time as the temperature measurements. Typic.al temperature measurements for**10~** load were found to be 1021°C (Levell), 825°C (Level 2), and 580°C (leve13).

7A-55

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## .. :,".,0,_.

_



### As expected, in the upper furnace region temperatures near the wall tended to be lower than temperatures towards the center of the boiler. However, the overall temperature profiles tended to be fairly uniform. The temperatures at levels 1and 2were within the temperature window for enhanced urea chemicals. The temperature at level 3 however, was too cold for injection of chemicals available at RWE. Gas composition profiles for NOx, CO and Oz were recorded at the three levels of injections. The NOx, CO and 0tconcentrations differed at the threelevels. NOx values were highest at level l. 

### Higher NOx concentrations recorded at level 2 were associated with higher Oz concentrations atthis level. The CO levels were found to be significantly hlgher at level 1 than other levels. The higher concentration ofCO at level 1indicates that complete burnout has not occurred until after this point.
B. tiQx..]eductiQo. level 1Injection Results obtained from injection of mixtures of NOxOUT-A and enhancer at level 1 in the 0 boiler are shown in Figure 3. The Normalized Stoichiometric Ratio (NSR) is defined as the ratio of NHz species injected divided by the initial moles of NOx. Thus one mole of urea per mole of NOx represents an NSR of 2.0. The initial HOx level for these series of experiments was approximately 550 mg/Nmr**(6~** 

### Oz). The results show an essentially linear response to increasing amounts of urea injection. The effect of enhancer is to shift the temperature window for NOx reduction activity to a lower temperature (5). Thus at a specific operating temperature, the addit

### ion of enhancer cou1d result in either increased NOx reduction, decreased NOx reduction or no change in NOx reduction. Adecrease in NOx reduction implies that the reaction temperature (in this case approximately 1020°C) is such that the operation is on the high side of the reaction temperature window. There is a benefit in operating on the high side of the formation is suppressed while reaction temperature window in thatby-product NH NOx reduction is only slightly diminished (11). 1 

### The amount of NOx reduction achieved in these experiments implies a urea utilization in the range of**27~** 

### with the low enhancer ratio shifting to 20% for the high enhancer ratio (assuming that each urea molecule is theoretically capable of reducing two molecules ofHOx). As Figure 3 indicates, the response of utilization to increasing NSR is essentially flat over the range of NSR investigated. Other studies have shown that utilization will tend to decrease with increasing NSR (5).
C. NOx Reduction, Two level Injection Urea and enhancer injection was performed simultaneously at levels 1and 2 to determine ifmultiple level injectionwould significantly (A) 

### increase chemical utilization, (8) reduce NH1 

### slip, and (C) increase the HOx reduction. Results from injection of urea and enhancer at level 1versus levels 1and 2at comparable test conditions are contained in Table 1.

7A-56 

# j 

# j j j t I

### Generally, itcan be concluded thaturea utilization increaseswhen urea is split between two levels at the same overall NSR. These results were achieved despite a slightly higher overall E/U ratio with two level injection. Although it has previously been found that a higher E/U ratio leads to lower NH3 

### slip, NH3 

### slip was as high with two level injection as with one. It is believed that NH J 

### slip from level 2was the result of chemical impingement on the superheater platens which were within 5feet ofthe point of injection at Level 2. Efforts were made to inject the chemicals between the platens, but it was virtually impossible to completely eliminate direct chemical impingement.
D. Enhancer/Urea Ratio. Control of NH3 Slip The enhancer/urea (E/U) ratio is one of the most significant process variables in the NOxOUT Process. As previously noted, the enhancer/urea ratio can affect the level of NOx reduction but it is particularly important in the control of**N~** 

### slip. AJIIT10nia (NH) is a by-product of the reaction between NOx and urea that can be fonned under certain conditions. The amount of

### NH~ produced is a function of various process variables and tends to increase with: decreasing temperature increasing the reagent to NOx mole ratio (increasing NOx reduction) decreasing enhancer/urea ratio. The amount of NH fonned tends to increase with increases in NOx reduction and therefore a trade 3 

### offoccurs when NOx reduction has to be forfeited to maintain low NH3 

### levels. Figure 4shows acomparison ofammonia slipversus NOx reduction at two different E/U ratios. At the higher E/U ratio less ammonia was generated per increment of NOx reduction. The higher E/U ratio enables NOx reduction to be increased from about**3~** 

### to about**5~** 

### at 5 ppm of NH3• 

### NOx reduction can be further increased to about 65% with an NH3 

### slip of less than 15 ppm.
E. Burner$ Qyt-of-Service During the demonstration, extensive data collectionwas undertaken to detennine if differences in NOxOUT Process perfonnance could be attributed to a specific burner slit that was out-of-service. Temperature measurements were taken, as previouslydescribed, priorto injectionwith differentconfigirations ofburner slits in service. Only slightvariations in dailyaverage temperatures indicated that there was no significant temperature difference with any specific burner slit out-of-service. In addition, process results obtained with the four different burner slits outof-service indicateno significantdifference in process performance

..The amount of urea required to achieve agiven level ofNOx reduction and the level of NH slip were essentially unchanged. 3



### F. Low Excess Air and Low Load Two of the specific objectives of the demonstration were to detennine the flexibility of the NOxOUT Process to respond to reduced load and to low excess air (simulated combustion modification). Temperature profiles and gas composition analyses obtained at Level 1revealed significant differences for the modified conditions (TJb1e 2).

7A-57

# ·

, 

## . Low excess air resulted in ahigher temperature and alower HOx content at level 1. Oxygen content was significantly lower and carbon monoxide (CO) was higher. When load was reduced to**6~** the temperature and NOx content dropped. Substantial variation in CO content was observed from point to point at level 1 during the experiment with low excess air. These localized concentration variations of CO could be the result of slow burnout of char. Process results obtained with low excess air and low load are shown in Table 3and compared with data obtained at normal**10~** load conditions. During the experiments at higher NSR, enhancer alone was injected at level 2to provide an additional level of control over NHJ slip. Experiments at low excess air were initially carried out (exp. H) at the same chemical flow rates as had previously been determined to be the optimum for 100r. load conditions (exp.G). The NSR increased**fro~** 2.4 to 3.0 because of the lower baseline level of NOx and reduction declined from**4~** to**45~.** At**6~** load conditions (exp. 1) the temperature at Levell is lower than at**100~** load (954°C vs. 1,021OC). At these conditions a three-fold increase in enhancer rate was required to maintain the HH3 slip at 5 ppm. The fact that an NSR of 3.0 is required to achieve comparable HOx reductions for both low load and low excess air conditions is most likely due to the lower initial NOx concentration in the flue gas. Overall, these data clearly demonstrate that the amount of enhancer required to maintain NH3 slip below atarget level depends upon the temperature at the point of injection. The average temperature at level 1varied over the range of 954 to 1,065°C. Within this temperature range, the amount of enhancer required to meet NH) limits increased from 1part enhancer to 30 parts urea at 1,065°C to 1 part**en~ancer** to 2 parts urea at 954°C.
TEST RESULTS

- C2 BOILER A. Start-yo Tests Prior to the start-up ofNOxOUT injection and soon after the C2 boiler returned to stableconditionswith thenewly installedcombustion modifications, Fuel Tech measured basfline temperature, NOx,**O~** and CO. These measurements were carried out in a grid at each level of injectlon. Temperature and gas composition data gathered at 80 and**10~** load are shown in Table 4. The overfire air which diverted a part of the combustion air to the ports above 19mhad the effectofextending the primary combustion zone. The first injection level was within this extended combustion zone. As aresult ofthese conditions, the values for both HOx and CO were extremely erratic and averages were considered to be meaningless. A

lthough temperature 1eve1sat 19 meters wO'lld appear to be conducive to good NOxOUT reagent utilization, the high CO levels existing at level 1 have the impact of shifting the temperature window In which urea is effective (15). Early injection tests at level 1 were not productive for HOx reduction. It was apparent that the "effective" temperature at these high CO conditions was too high for reasonable urea utilization. Further testing was based on injection at the second (25m) level. The third level of injection (36m) was not required because the total amount ofNOx reduction required to achieve <200 mg/NmJ proved to be only about**35~** which could be readily achieved at level 2.

7A-58B. TwentY-fiye Meter Leyel Injection HOx reductions in the range of**40-50~** were repeatedly achieved at relatively low HSR values from baseline NOx levels of 275-325 mg/Nrrr. Figure 5 shows the reductions and utilizations observed at varying NSR values. Although the majority of the tests were performed with straight injectors, some comparative tests were performed using angled injectors. NOx reduction and utilizationwere not found to be sensitive to different types of Injectors. These tests were carried out at an E/U ratto in the :"**"~ge** of 0.3 to 0.6. This range was based on results previously determined to be optimum In the Dboiler tests. Specific tests to optimize the quantity of enhancer for the C2 boiler remain to be undertaken. Tests at**8~** load with each one of the four separate burner banks out-of-service showed thattheprocess resultswere irdependent ofthe specificburner bank that was**out-of-servi~e.** Baseline NOx levels at**8~** load were typically in the range of 250·275 mg/Nrrr compared to 275-325 mg/Hm3 at**10~** load. The NSR required to ach1eve <200 mg/Nn? was about 1.5 and reagent ut111zation is lower than that achieved at**10~** load. The reason for thts**I~** postulated to be the higher CO concentration at**8~** load. As previouslynoted, CO shifts the temperature window to lower temperatures, and at the upper end of the window this results in decreased reagent utilization.
C. Ammonia Slip The Unit C2 contract between RWE and Fuel Tech specified that after the initial j optimization portion of the demonstration, the "recipe" for achieving the necessary NOx reductions over a range of operating conditions would be turned over to RWE to test its ability to operate continuously for four weeks. Ammonia slipwas avery important consideration for RWE. During the four week acceptance 

# I
period, 64 analyses ofammoniawere to be undertaken todetermine compliance with the 5ppm limit. Fuel Tech performed considerable ammonia sampling and computer 

## J modelling to gather information on the potential for ammonia formation. i Samples of flue gas were withdrawn from four locations in the flue gas ducts upstream of the air heater. The flue gas temperature at this point is approximately 325°C. The baseline level of NH J was determined before the start of injection and was found to be 0.7 ppm. Tnere was no stratification of NH in the flue gas. Following the start of injection at the second level (2:> J meters) it was found that the overall specification of <5 ppm of NHl. could be maintained at both**10~** and**8~** load while also maintaining NOx at <200 mg/Nm3• A computer model of the C2 bo11er was utl1ized in an effort to get a better Interpretation of the flow and temperature regimes affecting ammonia formation within the boiler at the second level of injection. Figure 6 shows a computer generated temperature profileat 25 meters and the location of the 12 injectors. The model showed that velocity and temperature are influenced by the boiler throat which starts right above the 25 meter level. This throat shifts the swirl in the flue gas which is characteristic of a tangentially fired boiler. This shift combined with the location of the overfire air ports results in cooler areas in the front right and back left corners away from the core of the swirl. This suggested that injection into these cooler regions might be leading to NH slip. 3

7A-59Elimination of five of the twelve injectors at level two combined with an enhancer/urea ratio of about 0.6 led to the extremely low levels of NH3 slip. Atotal of 64 individual analyses for NH3 were carried out over a one month period; 24 at**100~** load and 40 at**80~** load. The overall average of 1.5 ppm is less than one ppm above baseline. The overall amount of slip is well below the target of 5ppm.
CONCLUDING REMARKS The results of the above described projects at the**t~o** brown coal fired boilers can be summarized as follows. ANOx reduction of 40 to 50% can be achieved with less than ppm of NH3 slip. Higher NOx reductions are possible depending on the ability to achieve a good distribution of the chemicals and/or on the availability of multiple levels for injection. In particular, with a HOx emission of 300 mg/Nm3 (approximately 150 ppm) or less, which was established by the application of combustion modifications, the intended emission value of less than 200 mg/Nm3 (approximately 100 ppm) can be reached with an NHJ slip of well below 5 ppm. The use of enhancer is effective in the control of NH slip over various boiler loads especially when load changes result in 3tempt?l"ature shifts within the boiler. The process iseffective atvarious loads and operating conditior.s, without having to change injectors. Reagent utilization increases with multiple level i:ljection of urea where more than one level is available at appropriate temperatures. The use of enhancer permits the chemical utilization to be optimized for a specific reaction temperature. The process can be easilyretrofittedon an existing boilerwith only small disruption to on-going operations. RWE's performance objectives for NOx reduction were met by the NOxOUT Process. Further optimization of operating cost can be achieved as the technology evolves. This will be done by optimizing chemical treatment \ and injection parameters for specific boiler applications. , 

### .! REFERENCES
1. Mohnen, V.A., "The Challenge ofAcid Rain", ScientificAmerican, Vol. 259, No.2, 30-38, August, 1988. 2. Bruck, R.I., "Decline of Boreal Forest Ecosystems in Central Europe and the Eastern North America

- Links to Air Pollution and the Deposition of



# .. ,i Nitrogen Compounds", 1987 Joint Symposium on Stationary Combustion NOx Control, March 23-26, 1987, New Orleans, LA 3. Konig, J., Derichs, 11'., Hein, K., "Untersuchungen zum Einsatz der SCR­**T~chnjk** hinter Braunkohlefeuerungen", Sonderheft der Zeitschriften BWK, TU und Umwelt im VOl-Verlag (1988), Heft 10

,''',.,

### 4. Hein, K., "The Application of Combustion Modifications for HOx Reduction to Low-Rank Coal-Fired Boilers", 1989 Joint Symposium of Stationary Combustion HOx Control, March 6-9, 1989, San Francisco, CA. 5. Epperly, W.R., Broderick, R.G., and Peter-Hoblyn, J.D., "Control of Nitrogen Oxide Emissions from Stationary Sources", American Power Conference, April 20, 1988, Chicago, 1L. 6. Muzio, L.J., and Arand, J.K., ·H(jillogeneous Gas Phase Decomposition of Oxides of Nitrogen", EPRI Report No. FP-253, 1976. 7. Arand, J.K., and Muzio, L.J., "Urea Reduction of NOx in Combustion Effluents", U.S. Patent *4,208,386 (1980). 8. Arand, J.K. and Muzio, L.J., ·Urea Reduction ofNOx in Fuel-Rich Combustion Effluents·, U.S. Patent *4,325,924 (1982). 9. Epperly, W.R., Peter-Hoblyn, J.D., Shulof, G.F. and Sullivan,J.C., "MultiStage Process for Reducing the ConcentrationofPollutants in an Effluent", U.S. Patent *4,777,024 (1988). 10. Epperly, W.R., and Sullivan, J.C., ·Process for the Reduction of Nitrogen Oxides in an Effluent", U.S. Patent *4,770,863 (1988) 11. Epperly, W.R., O'Leary, J.H., and Sullivan, J.C., "Process for Nitrogen Oxides Reduction and Minimization of the Production of Other Pollutants", U.S. Patent 14,780,289 (1988). 

### 12. Epperly, W.R. and Sullivan, J.C., "Process for the Reduction ofNitrogen Oxides in an Effluent", U.S. Patent 14,803,059 (1989).

, 

### 13. Bowers, W.E., "Reduction of Nitrogen-Based Pollutants Through the Use of 

# I i ,i 

### Urea Solutions Containing Oxygenated Hydrocarbon Solvents", U.S. Patent *4,719,092 (1988). 14. Bowers, W.E., "Reduction ofNitrogen

- and Carbon-Based Pollutants", U.S. Patent *4,751,065 (1988).

I· I t 

### 15. Caton, J.A. and Siebers, D.L., "Comparison of Nitric Oxide Removal by Cyanuric Acid and byAmmonia", PaperNo. 88-67, Western States Section/The Combustion InstituteFall Technical Meeting, DanaPoint, CA, October, 1988.

, 

## !

I 

# ,I
7A-61

## ~'**~.** rTABLE 1 SINGLEVS. TWO LEVELINJECTION Experiment A. B C 0 E F
No. 01 Levels 2 2 1 2
NSR (1) 1.2 1.0 2.7 2.6 3.0 3.3
8U(2) 0.1 0.15 0.2 0.56 0.03 0.2
% Reduction %Utillzatlon NHJ,ppm 31.4 26.0 13.0 44.6 45.0 14.0 51.0 19.0 20.5 64.0 24.0 44.0 14.5 50.5 15.5 12.9

(1) NSR.ratiootNHi molesinjected

dividedbythe initialmoles01 NOx (2)Weightratio01 Enhancerto Urea

TABLE2 EFFECTOF BOOSONTEMPERATUREAND GASCOMPOSITION
Conventional Low Excess Conventional ExcessAir Air ExcessAir Operation 100% Load 100% Load 60% Load
Level 1

Avg. Temp?C 1,008 1,065 954 Avg. NOxmglNm](l) 460 321 362 Avg. CO, ppm 47 700 38 Avg. vol. % 5.2 2.2 5.7
Level 2 0

Avg. Temp, C J 811 878 804 Avg. NOxmglNm (1) 513 328 347 Avg. CO, ppm 11 330 0**Avg.~,** vol. % 6.3 3.1 5.5
Stack J

NOx,mglNm (1) 584 403 427 CO, ppm 6 3 0**~,vol.%** 7.1 4.5 7.6 (1) Correctedto 60/0

# ° 2,

7A-52TABLE4 C2 BOILER

- TEMPERATUREAND GASCOMPOSITON
Load

____100%

_ _ 80%

_ Level 1(19m\ 2(25m) 1(19m) ·2(25m) Temperature

### J oC NOx, mglNm 1040 250-400 995 250-350 992 150-400 980 150-400 CO, ppm 

# ° 500-10000 70-3000 10000-30000 250-10000

2,% 3.2 4.1 1.2 4.2

7A-63

### , .' 'r ., 

# I , r

.'

1A-64 

## R.W.E. C2 BOILER

.-...... ". 

## R.W.E. DBOILER

Fig. 2. Fig.1

.**~'I** 

## . , .J**.~;** .,' :

### Fig. 3. 

### NOx REDUCTION AND UTILIZATION vs. NSR 

## R.W.E. UNIT D 100 ,.------------------------,

I::l 0**.~** ..... ('ll N ;.:::l**.~** .....

0 

### '"' I::l 0 :;l CJ '"d 0::**,~.** 

### Fig.

, ' 100 90 80 I::l 0 70**.~** ..... CJ 60 '"d 0:: 50
0 40 Z

..... 30 I::l CJ 20 

### '"' 10 0 90
BO
70
60**~O** 40
30
20
10 +

E/U Ratio = 0.1 E/U Ratio = 0.17

### ""O'-------~-o •

### ~---------_0-------_{J

O-+--,----,.--,-...,.----r--r----r--.,--...,----.....--,..-----.j

0.0 0.3 0.6 0.8 1.1 1.4 1.7 2.0 2.3 2.5 2.B 3.1 3.4 NORMALIZED STOICHIOMETRIC RATIO (NSR)

E/U Ratio = Enhancer to Urea Weight Ratio REDUCTION ( ) UTIUZATION (-------)



### 4. 

### AMMONIA vs. PERCENT NOx REDUCTION 

## R.W.E.

- UNIT D
E/U Ratio = Enhancer to Urea Weight Ratio

Average E/U Ratio

## =0.2 •



# • ° Average E/U Ratio

## =0.1 

### ° oOso 

# • 0 

### ° ° ° 0



### 'h°o 0 o 0 0 )i· ," I; I, r,

" 

## I

## '~; "

0.0 1.5 3.0 4.5 6.0 7.5 9.0 10.5 12.0 13.5 15.0 

### Ammonia (ppm) 7A-65NOx Reduction

Utilization 

# -----. x 

# •
x 

# •



# =1 

# E'**-~Li** I

# I I I 

### I 1 I 

# I I 

# I I I 

# I

12 II 10
7A-66 

### NOx REDUCTION AND UTILIZATION YS. 

### NSR 

## R.W.E.

- UNIT C2

0.3 0.5 O.B 1.1 1.3 1.6 1.9 2.1 2.4 2.7 2.9 3.2

NORMALIZED STOICHIOMETRIC RATIO (NSR) NSR = molar ratio of the amount of urea used relative to the amount of NOx present 

### FURNACE MODELLING

- TEMPERATURE PROFILE R.W.E. C2 BOILER

- 25m LEVEL O-t--,---,----,--.....---r---,,.--,---,--.---,.---,---j

0.0 50

. 70 90 60

60

30
20
10 40 100 

### -r----------------------, Fig. 5.

Fig. 6.

### EPA-600/9-89-062b June 

### 1989

PROCEEDINGS: 1989 JOINT SYMPCSIUM ON STATIONARY COMBUSTION NOx CONTROL San Francisco, CA. March 6-9. 1989 Volume 2

,',

Compiled by Claudia Runge Electric Power Research Institute 3412 Hillview Avenue Palo Alto, CA 93404

EPRI Project Manager: EPA Project Officer: William P. Linak David Eskinazi
U.S.**~nvironmental** Protection Agency Electric Power Research Institute 3412 Hillview Avenue Air and Energy Engineering Research Laboratory Palo Alto, CA 93404 Research Triangle Park. NC 27711



### AIR AND ENERGY ENG1NEERING RESEARCH LAGORATORY OFFICE OF RESEARCH AND DEVELOPt-IENT U.S. ENVIRONMENTAL PROTECTION AGENCY RESEARCH TRIANGLE PARK, NC 27711

REPRODUCED BY U.S. DEPARTMENTOF COMMERCE NATIONAL TECHNICAL INFORMATION SERVICE**SPRI~JGFIELD.** VA. 22161