THE EFFECT OF RESIDENCE TIME ON SNCR PROCESSES
L. 

## J. Muzio T. A. Montgomery

G. C. 

### Quartucy Fossil Energy Research Corp.



### D. P. Teixeira Pacific Gas and Electric Company



### presented at EPRIIEPA 1993 Joint Symposium on Stationary Combustion NOx Control 

### Bal Harbor, Florida

May 24-27, 1993

### Abstract THE EFFECT OF RESIDENCE TIME ON SNCR PROCESSES L. 

## J. Muzio T. A. Montgomery

G. C. Quartucy Fossil Energy Research Corp. 23342 C SouthPointe Laguna Hills, CA 92653
D.P. Teixeira Pacific Gas and Electric Company 3401 Crow CanyonRd. San Ramon, CA 94583

A pilot-scale experimental study was performed to determine the effect ofresidence time on SNCRprocesses. Testresults showed thatresidence times less than250 msec adversely impact process performance. Further, the test results showed that NO removal was faster with either anhydrous or aqueous ammonia injection than with aqueous urea injection. The results also showed that short residence times can lead to higher N20 emissions since N20 reductionreactions do not have sufficienttime to reduce

### NzO. Chemical kinetic calculations were in qualitative agreement with the pilotscale test results. 

### Introduction Interest in the use of selective non catalytic NOx reduction (SNCR) is increasing within the utility industry. This has resulted in a variety of applications where the SNCR temperature window occursbothin the mainradiantfurnace andwithin the furnace convective sections. When the temperature window is in the convective sections, chemical injection is limitedto the cavitiesbetween convective tubebanks. Depending onthe specific furnace design, residence times in these convective cavities canrange from 30 to 100 milliseconds. These short cavityresidence times, coupled with steep temperature gradients, can limitpotential NOxremoval performance. While an extensive amountofpilot- andbench-scale work hasbeen done on SNCR processes, most ofthis workhas addressed process parameters includingSNCR chemical type, amount of chemical, temperature, initial NOx levels, and additives. Little work has focused explicitly onthe effect ofresidence times. Sun, et al., usedchemicalldnetic calculations to investigateresidence time effects (1). 

### Inthis work, itwas shownthatresidence timewas most important as the temperature decreasedbelow the temperature for peakNOx removal; onthe hightemperature side ofthe temperature window, itwas less important since reaction rates increase exponentially with temperature. The current study was undertaken to experimentally study the effect ofresidence time on SNCR processes. This workwas done in supportof an SNCR demonstration at PG&E's Morro Bay powerplant (2). For this full-scale demonstration, SNCR chemical injection was into the convective section cavities. Since residence times within the convective cavities were on the order of35 milliseconds at full load, itwas decided that a pilot-scale studyofresidence time wouldbebeneficial ininterpreting the full-scale data. The objectives ofthe present studywere to experimentally determine the effect of residence time on SNCRprocesses and to determine the differences inrates ofNOx removal between anhydrous ammonia (NH3), aqueous ammonia (N'H.iOH) and aqueous urea. When addressing SNCRresidence time effects, three characteristic times need to be considered:
• mixing ofthe SNCR chemical with the combustionproducts • evaporation andrelease ofreactive nitrogen compounds (for aqueous solutions) • chemical reaction times In any experimental approach, itis difficult to separate each of the above characteristic times. For the current study, aneffort was made to keep the mixing as constant as possible between the various chemicals. 

### In this way, residence time effects can be attributed 

### to evaporation and release of reactive nitrogen compounds and chemical reaction times. During the current experimental study, the following parameters were investigated: SNCR Chemicals: anhydrous NH3, aqueous ammonia <NH40H), aqueous urea (NH2CONHz) Residence Time: 33

- 500 msec Temperature: 1500- 2100°F Chemical Injection Rate 

### (NINO molar): 0-2 Aqueous Solution Concentration: 0-1.67 gmol N/liter. Again, the primary objective was to define residence time effects onSNCRperformance. To support the experimental results, a limited amount ofchemicalldnetic calculations were performed. The calculations were done using a PC version ofCHEMKIN (3) along with the Bowman andMiller mechanism for nitrogen chemistry (4).

### Pilot-Scale Facility A schematic ofthe pilot-scale facility usedfor the current tests is showninFigure 1. 

### The pilot-scale combustor fires natural gas doped with 

### Nli3 to control the initial NO level. The combustion section is water cooled and partially refractory lined. The test sectionis refractory lined, 6 in. indiameter and 8 feet long. At the firing rates used for these tests, the residence time in the test sectionis nominally 0.5 seconds; the temperature drop along the test sectionis nominally 450°F

### I sec (250°F for the 0.5 second residence time through the test section). Fifteen ports are spaced along the length ofthe test section whichprovides a residence time resolution ofabout 30 milliseconds. SNCR chemicals used for the current study were gaseous ammonia (NH3), 

### and aqueous ammonia (N'l-40H) and aqueous urea (NH2CONH2) solutions. The SNCR solutions were injected into the combustion products at the throat of a venturi sectionlocatedjust upstream ofthe test section. A small air assist atomizer was used to inject the chemicals. For the case of gaseous NH3, the NH3 was mixed with the atomizing air; no liquid solution was used in this case. The atomizer was fabricated into a water cooled holder and located at the center ofthe venturi throat. The spray was directed downward (i.e., co-flowing with the combustion products). The solutions were pumpedwithvariable speed peristaltic pumps and metered withrotameters. In

### order to maintain a constant thermal environment inthe test sectionwhen aqueous solutions were used, the total amount ofliquid injection was held constant atnominally 1 liter/hr. By diluting a concentrated reagent solution with distilled water, the amount of chemical reagent was varied, while the total liquid flow rate was maintained. At a N/NO ratio of2.0, the solution concentrations were 0.833 mole % 

### nitrogenper liter (i.e., 2.5 wt% for urea and 1.4 wt% for ammonium hydroxide). Gas samples were taken at the sampling ports along the test section using a hot watercooled probe and transported to a series ofgas analyzers (NO/NOx, N20, CO, C02, and 02). NH3 concentration measurements were madeby scrubbing a gas sample through impingers containing dilute sulfuric acid followed by analysis with a specific ionelectrode. Experimental Results The results first compare the effect ofresidence time onNO reduction for the three chemicals. Subsequently, the effect ofresidence time onbyproduct emissions (e.g., 

## NH:3, NzO) are discussed. NO Reduction The effect ofresidence time onNO reduction for anhydrous ammonia (NH3)g, Nlf40H and aqueous urea is shownin Figure 2 for chemical injection temperatures of 1600°F, 1750°F and 1850°F and 2000°F. This figure shows data collected atnominal30 msecondintervals along the combustor test section. During this test series, the combustor was operated at a constant combustionproduct flow rate. The overall residence time inthe test section decreased from 0.47 seconds at 1600°F to 0.4 seconds at a temperature of 2000°F. The initial NO level was 125 ppm and the aqueous solutions had a concentration of 0.833 gmol N/liter. The chemicals were injected at a rate corresponding to a 

### NINO molar ratio of 2.0. Itshouldbe noted that the temperature referred to throughout the paper is a suction pyrometer temperature measurement obtained at the first samplingport downstream of the injection point. At this point, the aqueous solutions have had a chance to partially vaporize and mixing with the main combustionproductflow is nearly complete. This was felt to be a more representative temperature than the temperature entering the injection venturi since the concentrations ofthe aqueous solutions used for these experiments were more dilute than those utilized at full scale. (The maximum urea concentration was nominally 5 wt% and the maximum N'H40H concentrationwas nominally 2.8 wt%.) A number of observations canbe made from the data shownin Figute 2. First, at a temperature of 1850°F, residence times in excess of 150 mseconds are generally needed for the reaction to be substantially completed, regardless ofthe chemical utilized. As the temperature decreases, the reactionrates decrease. At temperatures below 1750°F, minimum required residence times approach 250 mseconds. As mentioned above, the experiments contain three characteristic times: mixing, evaporation/decomposition, and reaction. Insightinto evaporationeffects canbe gainedby comparingthe results inFigure 2 for anhydrous ammonia, NI-is(g), and aqueous ammonia, Nli40H (1). For these two cases, the primary differences are expected tobe the evaporation ofthe Nlf40H and the release of the NH3 to the gas phase. As seenin Figure 2, at 1600°F and 1750°F, gaseous NH3 removes NO faster than aqueous ammonia. At a temperature of 1850°F, whichis onthe hightemperature side ofthe SNCRtemperature window for ammonia, the NO removal rates are comparable for the first 100 msec. Higher removals are ultimately attained with aqueous ammonia. This higher overall removal with aqueous ammonia canbe attributed to either 1) the somewhat slower release ofthe chemical with more

## NHs reaching the cooler region of the test section; or 2) continued evaporationof the aqueous phasebeyond sample port number 1 

### (33 mseconds) resulting in some cooling of the gases inthe test section. At the two lower temperatures shown inFigure 2, aqueous urea reacts much slower than either anhydrous or aqueous ammonia. At 1850°F, NO removal rates become more comparable for all three chemicals. This is due to two effects. First, since 1850°F is above the peak temperature for NO removal using ammonia, withreactions oxidizing NHs to NObeginningto play a more importantrole, the net affect is an overall decrease inthe NO removal rates. Secondly, at higher temperatures, the evaporation and chemical decompositionrates will increase. At the same time, 1850°F is near the optimumtemperature for NOremoval with urea, whenNOremoval rates shouldbe highest.

### At a higher temperature of 1850°F, itcanbe seen thatthe 

## N'H3 emissions with aqueous ammonia decrease muchmore rapidly than at 1750°F. Again, the 

### Nli3 profile with aqueous urea is different. At this higher temperature, there is 

### no delayin the appearance of

## NH3. However, withurea, the NH3 decay is much slower than with aqueous ammonia injection. Also, as at 1750°F, the maximum 

### NHs concentration with urea injection was only 150 ppm, slightly over one halfofthe injected nitrogen.

NzO is also a productofSNCR process, withurea producinghigher N20 levels than ammonia injection (5). 

### NzOprofiles were also measured along the lengthof the test section during the course ofthe experiments. Figure 6 shows the NzO concentrations as a function ofresidence time for each chemical. In

### Figure 7, 

### the NzO 

### concentrations have beennormalized by the NO reduction, which can also be interpreted as the fraction of NO converted to NzO. Consistent withprevious studies, urea produces higher levels of NzO thaneither aqueous or anhydrous ammonia. The residence time effects onNzO concentrations are quite interesting. At temperatures below 1750°F, the ammonia injection results show increasing NzO 

### concentrations with increasing residence time. As the temperature increases above 1750°F, a peak in the NzO 

### concentration is observed. This peak occurs at a residence time ofnominally 150- 200 mseconds at 1850°F and 75 mseconds at 2000°F. As residence times increase, N20 concentrations decrease due to destruction reactions. Even at 1750°F, N20 concentrations at residence times inexcess of250 mseconds are lower than those measured at 1600°F. This indicates that N20 destruction reactions are important even at these temperatures. Somewhat similar trends are seen with urea injection (Figure 6c) except the overall N20 levels are higher. At temperatures of 1600°F, 1750°F, and 1850°F, N20 levels are seento increase monotonically withbothresidence time and temperature. At a temperature of 2000°F, N20 levels peak at a residence time of 200 mseconds and thenbegin to decrease as N20 destruction reactions predominate. The normalized N20 profiles show similar trends (Figure 7). 

### Withammonia injection, the normalized N20 levels are under 10%. At higher temperatures, normalized N20 levels decrease withincreasing residence times. Withurea injection at longresidence times, normalized N20 concentrations increased from 15% to near40% withincreasing temperatures. More importantly, at hightemperatures and shortresidence times, N20 levels approached 60% ofthe NO reduction. From a practical standpoint, this suggests that for applications with shortresidence times (e.g., injection inconvective cavities), NzO 

### levels maybe enhanced. In

### fact, the residence time effect seeninFigure 7c with urea injection explains the relatively highN20production observed during the PG&E Morro Bay SNCR demonstration(2).At 2000°F, the temperature is beyond the SNCR temperature window for ammonia, at aninitial NO level of 125 ppm, and additional NOis formed along the combustor (Figure 2d). The data for temperatures of 1750°F and 1850°F shownin Figure 2 have been normalized and replotted in Figure 3. 

### InFigure 3, the NO is shown as the fractional removal ofNO along the test section. Figure 3 shows that anhydrous ammonia reacts slightly faster than aqueous ammonia whichreacts slightly faster thanurea. For instance, at 1750°F, 75% ofthe reactionis complete innominally 150 mseconds withthe ammonium chemicals, whereas 220 mseconds is needed for urea. At 1850°F, reaction rates are faster on a normalizedbasis, with75% ofthe reaction completed in about 100 mseconds with the ammonium compounds. 

### Incomparison, aqueous urea requires about 180 mseconds to complete the same 75% ofthereaction. To better compare the effect ofresidence time and temperature, the data inFigure 2 for urea and ammonia havebeencross-plotted as a function oftemperature inFigure 4. With ammonia injection, a marked decrease inNO reduction occurs at residence times less than 110 mseconds. Also, consistent with previous pilot-scale studies, peak NO removals occur at 1750°F, atlong residence times. For aqueous urea injection, residence times less than 280 mseconds have a marked effect on performance. Again, this is likely related to the temperature gradient in the combustor ( 450°F

### I sec), and the slower release ofreactive nitrogen compounds from the urea solution. Also, the data in Figure 4 show peakNOremovals for a longresidence time at 1850°F with urea, nominally 100°F higher thanfor ammonia. 

### NH3 Emissions During this study, NH3 concentrations were measured along the test section for each of the three chemicals at a temperature of 1750°F. At a temperature of 1850°F, NH3 profiles were obtained along the test sectionfor aqueous ammonia and aqueous urea. The NH3 profiles are showninFigure 5. At 1750°F, 

### the NH3 profiles for anhydrous and aqueous ammonia are comparable,with anhydrous ammonia showing a somewhat faster decay than aqueous ammonia. The NH3 profile with aqueous urea injection at 1750°F is markedly different. First, there is a distinct delay inthe formation of ammonia, withmaximum NH3 concentrations occurring after 100 mseconds. This is consistent with a more gradual release ofreactive nitrogen compounds to the gas phase withurea injection. Withurea, itcanbe speculated that the aqueous solution must evaporate to near saturationbefore substantial decomposition ofthe urea occurs releasingreactive nitrogen compounds to the gas phase. Secondly, at 1750°F, peakNH3 concentrations are only 100 ppm, whereas 250 ppmofreactive nitrogenis beinginjected as urea. These lower measured concentrations of 

### Nli3 would be consistentwith a urea decompositionmechanism producing NH3 and HNCO (i.e., NH2CONH2 

### ->NH3 

### + HNCO).

### Chemical Kinetic Calculations To supportthe pilot-scale tests, chemical kinetic calculations were performed using a PC version ofCHEMKIN(3) and the Miller Bowman mechanismfor nitrogen chem.istry(4). The calculations were performed over a temperature range from 1500- 21000F, for aninitial NO level of 125 ppm andNINO 

### molar ratio of2. The calculations also incorporated a temperature gradient of450°F

### Isecond. Calculations were made for both ammonia (NH3) 

### and urea. The urea calculations assumed that the urea decomposed instantaneously to NH3 + 

### HNCO. The calculated histories ofNO are showninFigure 8 for both ammonia andurea. The calculated NO profiles are in qualitative agreement, although the absolute levels ofNO removal are higher than observed experimentally. With

## N'H3 injection, calculations show some NO removal evenup to aninjection temperature of2100°F; whereas experimentally, additional NO was formed above 2000°F. This could be due to the "injection temperature" whichwas defined for the experiments. Recall, the injection temperature for the experiments was measured at a point 33 

### mseconds below the point ofinjection. Thus, some ofthe injected ammonia experienced higher temperatures during the mixing process. This effect wouldbe expected to be more important at the higher injection temperatures. Likewise, withurea injection, the calculated NO removals are higher thanmeasured experimentally. Again, this may be attributed inpart to the mixing and evaporation process which experimentallyis more gradual thanthe assumed instantaneous release ofNH3 + 

### HNCO assumed for the calculations. The calculated NzO profiles versus time are shownin Figure 9 for urea injection. Figure 9a shows the calculated NzO concentrations versus residence time and Figure 9b shows the time histories of the NzO concentrationnormalized by the NO removaL These calculated NzO profiles canbe compared to the experimental profiles inFigures 6c and 7c. The NzO profiles are in good qualitative agreement with the experiments. The calculated NzO profiles further support the observationthat short residence times can lead to enhanced levels ofNzO emissions from SNCRprocesses. In

### fact, consistentwith the experiments, the calculations show that atresidence times between50 and 100 m.seconds over 50% ofthe NO reduced canbe converted to N20. Conclusions The results ofthe present study have shownthe importance ofresidence time for SNCR processes. Specifically:
• The tests showed thatfor all chemicals tested, residence times onthe order of250 mseconds were required to substantially complete 80% ofthe NO removal. This residence time will vary somewhatfor full-scale application, since mixing andevaporation times will be dependent on site-specific factors whichmay differ from the pilot-scale.
• For shortresidence time applications (t<lOO mseconds), itis necessary to inject at higher temperatures where evaporation and reaction rates are increased. Even at higher temperatures, residence times can still impact SNCR performance.
• The tests also showed that gaseous ammonia and aqueous ammonia (Nli40H) reacted more rapidly 

### thanurea. For instance,with ammonia, peak removals occurred at a temperature of 1750°F while for urea, peakremovals occurred at 1850°f. The tablebelOW ShOWS the residence timeS required tO COmplete 50°/o Of the NO removal observed atthe combustor exit.

Chemical Temperature NH40H

Urea Time for SO% of the Overall Removal 70mseconds 110 mseconds
• Atresidence times below 100 mseconds and temperatures greater than 1850°F, N20 levels canbe relativelyhighfor urea injection. For these conditions, N20 destruction reactions, which are relatively slow, have not had sufficient time to reduceN20. 

### References 1. Sun, W. H., et al., "Post CombustionNOx ReductionwithUrea: Theory and Practice," presented atthe SeventhAnnual International PittsburghCoal Conference (September 1990). 2. Teixeira, D. P., et al., "Selective Non catalytic Reduction (SNCR) Demonstration in a Natural Gas Fired Boiler," 1993 Joint Symposium on Stationary Combustion NOx Control. 3. Kee, 

### R. J., et al., CHEMKIN: A General-Purpose, Problem-Independent, Transportable FORTRAN Chemical Kinetics Code Package, SANDIA Report SAND80-8003, reprinted July 1987. · 4. Miller,

## J. A., Bowman, C. T., "Mechanism andModeling ofNitrogenChemistry in Combustion." 

### Progress in Energy and Combustion Science, 15,287 (1989). 5. Muzio, L.

## J., et al., 

### 'N20FormationinSNCRReduction Processes," EP A/EPRI 1991 Joint Symposiumon Stationary Combustion NOx Control (March 1991).JACKET

.LII.:'lUEOJS H20 REAGENT

--11>- SAMPLE FORTS (13 TOTAL)



### Figure 1. Pilot Scale Combustor Facility MAIN AIR 

# t NH3 NAT. GAS1.00
E 0.80 Q. Q. 

# - E Q. Q. 

### o· 0.60 z ] : c 0.40 

# - 0 z a; ..5 0.20 

# -
0.000.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds

1.00

E 0.80 Q. Q. 

# - E Q. Q. 0 0.60 z ] : c 0.40 

# - 0 z c 0.20 c ;::

0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds b) 1750°F Figure 2. Effect of Residence Time and Chemical on NOxon Reduction (NOi = 125 ppm; NINO = 2.0) 0 NH3 (g) ll NH40H {I) Cl Urea (I)

0 NH3 {g) ll NH40H (I) 0 Urea (I)1.00 0 NH3 (g) 

## s 0.80 A NH40H (I) a. a. 

# - s Cl Urea (I) a. a. 

### 0 0.60 z ii :;::: ] 0.40 

# - 0 z iii c 0.20 ;;:

0.000.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds

1.60 0 NH3 (g) 1.40 

## s a. a. 1.20 

# - s a.**---o--~o~----o--~o** A A A Cl Urea {I) a. 

### o· 1.00**·-·-·-·-·~·-·~·-·-·-·-·-·-·-·-·-·~·-·-·-·-·-·-·-·** z ] 0.80


# - ]


# - 0.60 0 z iii 0.40 c ;;: 0.20 0.000.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds d) 2000°F Figure 2. (Continued) Effect of Residence Time and Chemical on NOx on Reduction (NOi = 125 ppm; NINO = 2.0)

# ~~ 0 z

# ~: 1.0 0 0.8 l1 Cl 0.6

0.4

0.2

0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds 

### a) 1750°F
1.0 0 0.8 A 0.6 Cl

0.4

0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds



### Figure 3. Normalized NO profiles versus Residence Times 

### (NOi = 125 ppm/ NINO 

### = 2.0) NH3 (g) NH40H (I) Urea (I)

NH3 (g) NH40H (I) Urea (I)1.2 

# - ca :;: 1.0 c:: 

## 0 0.8 

### z 

# - ; 0.6 c:: 

# - 0 0.4 

### z 0.2 0.0 I...--'----I-..J-----1..-..__-'-___..-....L..----I....----JL.....--L-----J

1500 1600 1700 1800 1900 2000 2100 TEMPERATURE, °F a) Ammonia

## ~-----~~--~------ 1::1 c -0.8
c:: 

## g 0.6 

### z ::::::.**~** 0.4 

# - 

# - 0 

### z 0.2
0.0**~....-_._.......~._....._--~.._....__,_____._...~--__.__..___.____,** RESIDENCE TIME. msec 

### --o-- 33 

## -o-- 110 A 280 • 420

RESIDENCE TIME. msec c 33 -o--**~10** l!s. 280 420

1500 1600 1700 1800 1900 2000 2100 TEMPERATURE, °F b) Urea

Figure 4. Effect of Temperature and Residence Time on NO Reduction with a) Anhydrous NH3 , and b) Aqueous Urea (NOi = 125 ppm, NINO= 2.0)250

200


## s c. 150 c.

### ~ Ill (") 100 ::: z 50

0 0.0

250

200


### s c. 150 c. 

### Ji. (i) (") 100 :::c: z
50

0.0 0 D. [J

0

. I 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds

D. [J

0.1 0.2 0.3 0.4 0.5 Residence Time, seconds 

### b) 1850°F Figure 5. NH3 Profiles along the Combustor (NINO= 2.0; NOi = 125 

### ppm) NH3 (g) NH40H {I) Urea (I)

NH40H (I} Urea (I)10 8 E c. c. 6 

### 0 4 N z 2 0**0~0~**

10 8 E c. 6 c. 

### 6 4 N z 2 0 0.0

20 15 E c. c. 10 0 N z 5 00.0 0 A Cl 

### <>

0.1 0.2 0.3 0.4 

### 6.5 Residence Time, seconds a) NH 3 (g)

0.1 0.2 0.3 0.4 0.5 Residence Time, seconds b) Aqueous Ammonia (NH40H)

0.1 0.2 0.3 0.4 0.5 Residence Time, seconds c) Aqueous Urea Figure 6. N20 Concentration Versus Residence Time (NOi = 125 

### ppm; NINO= 2.0) 1600 Of 1750 Of 1850 Of 2000 Of

0 1600 Of A 1750 *f Cl 1850 Of 

### <> 2000 Of

0 1600 Of A 1750 *F Cl 1850 Of 

### <> 2000 Of0.5 0 1600 OF 0.4 tJ. 0 1750 *F z 0.3 <1 D 1850 OF 

# - 0 0.2 N z 0.1 0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds a) NH3 (g) 0.5 I T I I :


## . 0 1600 OF 0.4 

# - 

# - 0 tJ. 1750 *F z <l 0.3 

# - - 

# - D 1850 OF 0 0.2**~** 

# - N z 0.1**~** 

# -**~.1:]** _...... 

### "'" '-" 0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds b) Aqueous Ammonia (NH 40H)
1.0 0 1600 OF 0.8 0 tJ. 1750 *F z 0.6 <l D 1850 OF 

# - 0 0.4 0 N 2000 OF z 0.2 0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds c) Aqueous Urea Figure 7. Normalized N20 Profiles versus Residence Time (NOi = 125 ppm, NINO= 2.0):::::::- 0.8 ctl 

# - c: 

## 0 0.6 

### z ..._ ctl c: 0.4 

# - - 0 z 0.2
0.0 I...-.....L...---l-.....L...--1.-...__--I._
........**--~...----~._...~....-__,_---1** RESIDENCE TIME. msec c 25 0 50 0 100 A 200 • 500

1500 1600 1700 1800 1900 2000 2100 TEMPERATURE, °F a) Ammonia

1.0 RESIDENCE TIME. msec 0.8 ctl c 25 

# - c: 0 50 

# - 0.6 0 

### z 0 100 

# - ctl A 200 c: 0.4 

# - • 500 

# - 0 

### z 0.2
0.0 1...-....&...-1...-..&...---1-...L...---I.-"""--....&....-....____._____.----l

1500 1600 1700 1800 1900 2000 21 00 TEMPERATURE, °F b) Urea
Figure 8. Calculated Effect of Temperature and Time on NO Removal (NOi = 125 ppm, NINO= 2.0)25
20 E c. 15 c.

- 

# . 0 C\i 

### z 10

5

60

50 

## *' 40 6 z .:::::! 0 30 C'\1 z 20

10 100 200 300 400 RESIDENCE TIME, msec a) N2

## o Concentration, ppm

RESIDENCE TIME, msec

Figure 

### 9. Calculated 

### N20 Profiles (Urea, NINO= 2.0; NOi 

# =125 ppm) 500 TEMPERATURE. °F 0 1500 6 1700 c 1800 -o- 19oo- 

# • 2100

TEMPERATURE, °F
0 1500 

## • 1700
1:1 1800 

## • 1900 

## • 2100

# r z I I**-~**

# ~: 1.0 0 0.8 6. [J 0.6

0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds a) 

### 1750°F
1.0 0 0.8 6. 0.6 [J

0.4
0.2**0.0·~._~~_.~~._~~--~~._~~--~~~~~** 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds



### Figure 3. Normalized NO profiles versus Residence Times (NOi = 125 

### ppm/ NINO = 2.0) NH3 (g) NH40H (I) Urea (I)

NH3 (g) NH40H (I) Urea (I)1.2


# - «< 

# =1.0

;: 

## 0 0.4 

### z 0.2 0.0 '-------'--olo...""""'-......lo-"'--""""'-......1.-..a...........l----l'----l

1500 1600 1700 1800 1900 2000 21 00



### _ o.a .-:: c 

### (5' 0.6 

### z 

# - - co .E 0.4 

# - 

# - 0 

### z 0.2 TEMPERATURE, °F a) Ammonia



# ....**D---------~----~------** 9::1 --c

0.0 1...-....a........l.-...._
........ __ olo...__._
__ l...-......._.....1._....._.....1RESIDENCE TIME. msec 

### --o-- 33 

### --o- 110



### ... ta -280 • 420

RESIDENCE TIME. msec 1:1 33 

### --o-- 110 A 280 

# • 420

1500 1600 1700 1800 1900 2000 2100 TEMPERATURE. °F b) Urea

Figure 4. Effect of Temperature and Residence Time on NO Reduction with a) Anhydrous NH3, and b) Aqueous Urea (NOi 

### = 125 ppm, NINO= 2.0)250

200 E c. 150 c. _g.. UJ C') 100 :J: z 50

0 0.0

250

200
E 150 c. c.

### ~ UJ C') 100 :J: 

### z 50

0.0 0 A []

0

0.1 0.2 0.3 0.4 0.5 Residence Time, seconds

A []

0.1 0.2 0.3 0.4 0.5 Residence Time, seconds 

### b) 1850°F Figure 5. NH3 Profiles along the Combustor (NINO= 2.0; NOj = 125 ppm) NH3 (g) NH40H (I) Urea (I)

NH40H (I) Urea (I)

### e c. c. 

### 0 N z



## e c. c. 

### 0 N z



## e

c. c. 

### 0 N z 10 0 8 ll. 6 Cl 4 

### <> 2 0 

### ··**-o:o~~···** 

### ·· 

## --o:5

10

8 6 4 2 00.0

20 15 10

5 00.0 Residence Time, seconds a) NH3 (g)

0.1 0.2 0.3 0.4 0.5 Residence Time, seconds b) Aqueous Ammonia (NH40H)

0.1 0.2 0.3 0.4 0.5 Residence Time, seconds c) Aqueous Urea Figure 6. N20 Concentration Versus Residence Time {NOi = 125 

### ppm; NINO= 2.0) 1600 "F 1750 Of 1850 Of 2000 OF

0 1600 °F 1!. 1750 *F 0 1850 °F 

### <> 2000 °F

0 1600 °F 6 1750 *F Cl 1850 °F 

### <> 2000 °F0.5 0 1600 Of 0 6 1750 •f z <I Cl 1850 Of 

# - 0 IN z

0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds a) NH 3 {g) 0.5 I I I I : 0 1600 Of 0.4 1:- 

# .. 0**~** 6 1750 *f z to <I 0.3 1- 

### -: 

# - : Cl 1850 Of 0 0.2 1:-**~** IN z ' 0.1 1- 

### -: 

### ( ..r:'l :1**~** T 

## - 0.00.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds b) Aqueous Ammonia {NH40H)
1.0 0 1600 Of 0.8 0 A 1750 •f z 0.6 <I [J 1850 Of 

# - 0 0.4 0 IN 2000 Of z 0.2 0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds c) Aqueous Urea Figure 7. Normalized N20 Profiles versus Residence Time (NOi 

# =125 ppm, NINO

# = 2.0)RESIDENCE TIME. msec ::::::- 0.8 tU c: 

## 0 0.6 

### z 

# -**~~**..........._ tU c: 0.4 

# - 

# - 0 

### z 0.2
0.0 L-.-'----L-..&.-....L.-L...--L...---1.--'----'----lL...-..1....---I

1500 1600 1700 1800 1900 2000 21 00 TEMPERATURE, °F a) Ammonia D 25 0 50 0 100 6 200 • 500

RESIDENCE TIME. msec ::::::- 0.8 tU



## .... 0 0.6 

### z 

# - - tU c: 0.4 ;;::: 

# - 0 

### z 0.2
0.0 L...--'----'--'----'--"'---'-----'--'----'--"'----'----1

1500 1600 1700 1800 1900 2000 21 00 TEMPERATURE, °F b) Urea D 25 0 50 0 100 6 200 • 500

Figure 8. Calculated Effect of Temperature and Time on NO Removal (NOi 

### = 125 ppm, NINO= 2.0)20

10

5

60
50
eft 40 ci :z**~ ~**  30 :z 20
10 TEMPERATURE. Of 0 1500 A 1700 D 1800
--"Y--···--- ·-···-- --····--=o.-,_...oot:!'""'::'"'-:-'"=l ····· --o-19oo-

--

100 200 300 400 RESIDENCE TIME, msec a) N20 Concentration, ppm

RESIDENCE TIME, msec**Figure~·** Calculated N20 Profiles (Urea, NINO= 

### 2.0; NOi 

### = 125 ppm) 500 • 2100

IEMF'ERAIURE. °F
0 1500
6 1700 c 1800 

## • 1900 

## • 2100