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, 1993THE EFFECT OF RESIDENCE TIME ON SNCR PROCESSES L. 

## J. Muzio**T.~.Montgo~ery** 

### G. C. 

### Quartucy Fossil Energy Research Corp. 23342 

### C SouthPointe Laguna Hills,**C~** 92653


### D. P. Teixeira Pacific Gas and Electric Company 3401 

### Crow CanyonRd. San Ramon,**C~** 94583

Abstract 

### pilot-scale experimental study was**perfor~ed** 

### to determine the effect ofresidence**ti~e** 

### on SNCRprocesses. Testresults showed thatresidence times less than 250 

### msec adversely impactprocess performance. Further, the test results showed that NO**re~oval** 

### was faster with either anhydrous or aqueous**a~onia** 

### injection than with aqueous urea injection. The results also showed that short residence times can lead to higher N20 emissions since N20 reduction reactions do not have sufficienttime to reduce N20.**Che~cal** 

### kinetic calculations were in qualitative agreement with 

### the pilotscale test results.
Introduction 

### Interestin the use ofselective non catalytic NOx

### reduction (SNCR) is 

### increasing within the utility industry. This has resulted in a variety ofapplications where the SNCR**te~perature** 

### window occurs bothin the main radiantfurnace and within the furnace convective sections. Whenthe temperature window is in the convective sections, chemical injectionis limited to the cavities between convective tube banks. Depending on the specific furnace design, residence times in these convective cavities canrange**fro~** 30 

### to 100 

### milliseconds. These short cavity residence times, coupled with steep**te~perature** 

### gradients, can limitpotential NOx 

### removal performance. While an extensive amountofpilot- andbench-scale work has been done on SNCR processes, most ofthis work has addressed process parameters including SNCR chemical type, amount ofchemical, temperature, initial NOx 

### levels, and additives. Little work has focused explicitly on the effect ofresidence**ti~es.** 

### Sun, et al., usedchemical kinetic calculations to investigateresidence time effects (1). In this work, itwas shown thatresidence time was most important as the temperature decreasedbelow the temperature for peak NOx removal; on the high temperature 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 SNCRprocesses. This work was done in supportofan SNCR demonstration at PG&E's Morro Bay power plant (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, it was decided that a pilot-scale study ofresidence time would be beneficial in interpreting the full-scale data. The objectives ofthe present study were to experimentally determine the effect of residence time on SNCRprocesses and to determine the differences in rates ofNOx removal between anhydrous ammonia (NH3), aqueous ammonia (NH.40H) and aqueous urea. When addressing SNCRresidence time effects, three characteristic times need to be considered:

• mixing ofthe SNCR chemical with the combustionproducts
• evaporation and release ofreactive nitrogen compounds (for aqueous solutions)
• chemical reaction times In any experimental approach, it is difficult to separate each ofthe above characteristic times. For the current study, an effort was made to keep the mixing as constant as possible between the various chemicals. In this way, residence time effects canbe attributed to evaporation and release ofreactive 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 (NH2CONH2) Residence Time: 33

- 500 msec Temperature: 1500

- 2100°F Chemical Injection Rate (N/NO molar): 0-2 Aqueous Solution Concentration: 0-1.67 gmol N/liter. Again, the primary objective was to define residence time effects on SNCRperformance. To support the experimental results, a limited amount ofchemical kinetic calculations were performed. The calculations were done using a PC version ofCHEMKIN (3) along with the Bowman and Miller mechanism for nitrogen chemistry (4).Pilot-Scale Facility 

### A schematic ofthe pilot-scale facility used for the current tests is shownin Figure l. 

### The pilot-scale combustor fires natural gas doped with NH3 to control the initial NO level. The combustion sectionis water cooled and partially refractory lined. The test sectionis refractory lined, 6in. in diameter 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/sec (250°F for the 0.5 second residence time through the test section). Fifteen ports are spaced along the length ofthe test section which provides a residence time resolution ofabout 30 milliseconds. SNCR chemicals used for the current study were gaseous ammonia (NH3), 

### and aqueous ammonia (NH40H) and aqueous urea (NH2CONH2) solutions. The SNCR solutions were injected into the combustion products atthe throat ofaventuri sectionlocatedjust upstream ofthe test section. A small air assist atomizerwas used to inject the chemicals. For the case ofgaseous NH3, the NH3 was mixed with the atomizing air; no liquid solution was used in this case. The atomizerwas fabricated into a water cooled holder and located at the center ofthe venturi throat. The spray was directed downward (Le., co-flowing with the combustionproducts). The solutions were pumped with variable speed peristaltic pumps and metered with rotameters. In 

### order to maintain a constant thermal environment in the 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 % nitrogen per 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 (NOjNOx, 

### N20, CO, C02, and 02). NH3 concentration measurements were made by scrubbing a gas sample through impingers containing dilute sulfuric acid followed by analysis with a specific ion electrode. 

### Experimental Results The results first compare the effect ofresidence time on NO reduction for the three chemicals. Subsequently, the effect ofresidence time onbyproduct emissions (e.g., 

### NH3, N20) are discussed. NO Reduction The effectofresidence time on NO reduction for anhydrous ammonia (NH3)g, NI!40H and aqueous urea is shown in Figure 2for chemical injection temperatures of 1600°F, 1750°F and 1850°F and 2000°F. This figure shows data collected at nominal 30 msecondintervals along the combustor test section. During this test series, the combustor was operated at a constant combustionproduct flow rate. The overall residence time in the test section decreased from 0.47 seconds at 1600°Fto 0.4 seconds at a temperature of 2000°F. The initial NO level was 125 ppm and the aqueous solutions had a concentration of0.833 gmol N/liter. The chemicals were injected at a rate corresponding to a N/NO molar ratio of2.0. It should be noted that the temperature referred to throughout the paper is a suction pyrometer temperature measurement obtained at the first sampling port downstream of the injection point. At this point, the aqueous solutions have had a chance to partially vaporize and mixing with the main combustion productflow 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 NH40H concentration was nominally 2.8 wt%.) A number ofobservations can be made from the data shown in Figure 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 reaction rates 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. Insight into evaporation effects canbe gainedby comparing the results inFigure 2 for anhydrous ammonia, NH3(g), and aqueous ammonia, NH.40H (1). For these two cases, the primary differences are expected to be the evaporation ofthe N1f40H and the release ofthe NH3 to the gas phase. As seen in Figure 2, at 1600°F and 1750°F, gaseous NH3 removes NO faster than aqueous ammonia. At a temperature of 1850°F, whichis on the high temperature 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 

### NH3 reaching the cooler region of the test section; or 2) continued evaporation ofthe aqueous phasebeyond sample port number 1 (33 mseconds) resulting in some cooling ofthe gases in the test section. At the two lower temperatures shown in Figure 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, with reactions oxidizing NH3 to NO beginning to playa more importantrole, the net affect is an overall decrease in the NO removal rates. Secondly, at higher temperatures, the evaporation and chemical decompositionrates will increase. At the same time, 1850°F is near the optimum temperature for NO removal with urea, when NO removal rates should be highest.

### At a higher temperature of 1850°F, it canbe seen that the 

### NH3 emissions with aqueous ammonia decrease much more rapidly than at 1750°F. Again, the NH3 profile with aqueous urea is 

### different. Atthis higher temperature, there is 

### no delay in the appearance of

### NH3. However, with urea, the NH3 decay is much slower than with aqueous ammonia injection. Also, as at 1750°F, the maximum NH3 concentration with urea injection was only 150 ppm, slightly over one halfofthe injected nitrogen.
N20 Emissions NzO 

### is also a product ofSNCRprocess, with urea producing higher NzO 

### levels than ammonia injection (5). NzO 

### profiles were also measured along the length ofthe 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 been normalized by the NO reduction, which can also be interpreted as the fraction of NO converted to NzO. 

### Consistent with previous studies, urea produces higher levels of NzO 

### than either aqueous or anhydrous ammonia. The residence time effects onNZO 

### concentrations are quite interesting. At temperatures below 1750°F, the ammonia injectionresults show increasing NzO 

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

### concentration is observed. This peak occurs at aresidence time ofnominally 150- 200 mseconds at 1850°F and 75 mseconds at 2000°F. As residence times increase, NZO 

### concentrations decrease due to destruction reactions. Even at 1750°F, NzO 

### concentrations at residence times in excess of250 mseconds are lower than those measured at 1600°F. This indicates thatNzO 

### destruction reactions are important even at these temperatures. Somewhat similar trends are seen with urea injection (Figure 6c) except the overall NzO 

### levels are higher. At temperatures of 1600°F, 1750°F, and 1850°F, NzO 

### levels are seen to increase monotonically withbothresidence time and temperature. At a temperature of 2000°F, NzO 

### levels peak at a residence time of200 mseconds and thenbegin to decrease as NzO 

### destruction reactions predominate. The normalized NzO 

### profiles show similar trends (Figure 7). 

### With ammonia injection, the normalized NzO 

### levels are under 10%. At higher temperatures, normalized NzO 

### levels decrease withincreasing residence times. With urea injection atlong residence times, normalized NzO 

### concentrations increased from 15% to near 40% with increasing temperatures. More importantly, athightemperatures and shortresidence times, NzO 

### levels approached 60% ofthe NO reduction. From a practical standpoint, this 

### suggests that for applications with shortresidence times (e.g., injection in convective cavities), NzO 

### levels may be enhanced. In 

### fact, the residence time effect seenin Figure 7c with urea injection explains the relatively highNzO 

### production observed during the PG&E Morro Bay SNCR demonstration(Z).At 2000°F, the temperature is beyond the SNCRtemperature window for ammonia, at an initial NO level of 125 ppm, and additional NO is formed along the combustor (Figure 2d). The data for temperatures of 1750°F and 1850°F shown in Figure 2 have been normalized and replotted in Figure 3. 

### In Figure 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 which reacts slightly faster than urea. For instance, at 1750°F, 75% ofthe reaction is complete in nominally 150 mseconds with the ammonium chemicals, whereas 220 mseconds is needed for urea. At 1850°F, reaction rates are faster on a normalized basis, with 75% ofthe reaction completed in about 100 mseconds with the ammonium compounds. 

### In comparison, aqueous urea requires about 180 mseconds to complete the same 75% ofthe reaction. To better compare the effect ofresidence time and temperature, the data in Figure 2 for urea and ammonia havebeen cross-plotted as a function oftemperature in Figure 4. With ammonia injection, a marked decrease in NO reduction occurs at residence times less than 110 mseconds. Also, consistentwith previous pilot-scale studies, peak NO removals occur at 1750°F, at long 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/sec), and the slower release ofreactive nitrogen compounds from the urea solution. Also, the data in Figure 4 show peak NO removals for a long residence time at 1850°F with urea, nominally 100°F higher than for 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 section for aqueous ammonia and aqueous urea. The NH3 profiles are shown inFigure 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°Fis markedly different. First, there is a distinct delay in the 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 with urea injection. With urea, it canbe speculated that the aqueous solution must evaporate to near saturationbefore substantial decomposition ofthe urea occurs releasing reactive nitrogen compounds to the gas phase. Secondly, at 1750°F, peak NH3 concentrations are only 100 ppm, whereas 250 ppm ofreactive nitrogen is being injected as urea. These lower measured concentrations of

### NH3 would be consistentwith a urea decomposition mechanism producing NH3 and HNCO (Le., NH2CONH2 

### --> NH3 + HNCO).Chemical Kinetic Calculations To support the pilot-scale tests, chemical kinetic calculations were performed using a PC version ofCHEMKIN(3) and the Miller Bowman mechanismfor nitrogen chemistry(4). The calculations were performed over a temperature range from 1500- 2100°F, for an initial NO level of 125 ppm and 

### NINO 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 shown in Figure 8 for both ammonia and urea. The calculated NO profiles are in qualitative agreement, although the absolute levels ofNO removal are higher than observed experimentally. With NH3 injection, calculations show some NO removal even up to an injection temperature of2100°F; whereas experimentally, additional NO was formed above 2000°F. This couldbe due to the "injection temperature" which was 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 effectwould be expected to be more important at the higher injection temperatures. Likewise, with urea injection, the calculated NO removals are higher than measured experimentally. Again, this may be attributed in part to the mixing and evaporation process which experimentally is more gradual than the assumed instantaneous release ofNH3 +HNCO assumed for the calculations. The calculated N20 profiles versus time are shown in Figure 9 for urea injection. Figure 9a shows the calculated N20 concentrations versus residence time and Figure 9b shows the time histories ofthe N20 concentration normalized by the NO removal. These calculated N20 profiles canbe compared to the experimental profiles in Figures 6c and 7c. The N20 profiles are in good qualitative agreement with the experiments. The calculated N20 profiles further support the observation that short residence times can lead to enhanced levels ofN20 emissions from SNCRprocesses. In fact, consistentwith the experiments, the calculations show that at residence times between 50 and 100 mseconds 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 that for all chemicals tested, residence times on the 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 which may differ from the pilot-scale.

• For short residence time applications (t<100 mseconds), itis necessary to inject at higher temperatures where evaporation and reaction rates are increased. Even at higher temperatures, residence times can still impact SNCRperformance.

• The tests also showed that gaseous ammonia and aqueous ammonia (NI-40H) reacted more rapidly than urea. For instance, with ammonia, peak removals occurred at a temperature of 1750°F while for urea, peak removals occurred at 1850°F. The table below shows the residence times required to complete 50% of the NO removal observed at the combustor exit.

Chemical NH.tOH

Urea Temperature Time for 50% ofthe Overall Removal 70 mseconds 110 mseconds

• Atresidence times below 100 mseconds and temperatures greater than 1850°F, NzO levels canbe relatively highfor urea injection. For these conditions, NzO destruction reactions, which are relatively slow, have not had sufficient time to reduce NzO. 

### References 1. Sun, W. H., et al., "Post Combustion NOxReduction withUrea: Theory and Practice," presented at the Seventh Annual International Pittsburgh Coal 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 and Modeling ofNitrogen Chemistry in Combustion." 

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

## J., et al., ''NzO Formationin SNCRReduction Processes," EPA/EPRI 1991 Joint Symposium on Stationary Combustion NOx Control (March 1991).....-WATERJACKET
INSULATION COOUNG COILS (6 TOTAL)

PCUEO..JS H20 REAGENT ATOMIZING AIR MAIN AIR

NH3 NAT. GAS

Figure 1. Pilot Scale Combustor Facility0.5 0.4 0.3 0.2 0.1 0.00 L....;I000.10.....10...........L...................-.10......."""-......................10......................""""-1......J...... 0.0 1.00 0 NH3 (g) E 0.80 11 NH40H (I) c. c. 

# - E 0 Urea (I) c. c. 6 0.60 z lIII :E 

### .: 0.40 

# - 0 Z lIII c 0.20 

# -

Residence Time, seconds

0.5 0.4 0.3 0.2 0.1 0.000.0 1.00 0 NH3 (g) E 0.80 11 NH40H (I) c. c. 

# - E 0 Urea (I) c. c. 6 0.60 z iii 

# = .: 0.40 

# - 0 Z lIII 0.20 c ;:

Residence Time, seconds b) 17500 F Figure 2. Effect of Residence Time and Chemical on NOx on Reduction (NOj 

## =125 ppm; NINO 

## =2.0)0.5 0.4 0.3 0.2 0.1 0.00 L...o -"" ....L. -"" ..... 0.0 1.00 0 NH3 (g) E 0.80 IJ. NH40H (I) c. c. 

# - E 0 Urea (I) c. c. 6 0.60 z III .: c 0.40 

# - 0 Z III c 0.20 

# -

Residence Time, seconds

Urea (I) 

### o 

### o NH3 (g)

0.5 0.4 0.3 0.2 --0--:::::0---0-10 is IJ. A

0.1 1.60 1.40 E c. c. 1.20 

# - E c. c. 6 1.00 z 0.80 c


# - 0.60 0 z iii 0.40 c :;:: 0.20 0.000.0 Residence Time, seconds d) 20000 F Figure 2. (Continued) Effect of Residence Time and Chemical on NOx on Reduction (NOi 

## = 125 ppm; NINO 

## =2.0)0.5 0.4 0.3 0.2 0.1 0.2

0.2
0.0 B-

__......--Io........-...Io-......-...--r..-...Io-

__.I.-.I--Io.......__...&...

__.......--Io..... 0.0 1.0 0 NH3 (g) 0.8 11 NH40H (I) CI Urea (I)

# ~~ 0.6 

### 00 0.4 z

0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds a) 17500 F

1.0 0 NH3 (g) 0.8 li. NH40H (I) 0 Urea (I)

# ~: 0.6

0.4

Residence Time, seconds

Figure 3. Normalized NO profiles versus Residence Times (NOi 

## = 125 ppml NINO 

## =2.0)1.2
.; 1.0 

### .- s:::: 

### 0 0

.8 Z



### ..... -; 0.6 s:::: 

# g- 0.4 Z 0.2 RESIDENCE TIME. msec --0-- 33 110 ts 280

• 420

0.0 L...-.....L.._I...-...J-----'-....L...----'--..L...----'--'---
.........-.r.-----'

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

### ~-----C---n----- 1:: 0 0.8 <'CS s:::: 

## g 0.6 Z

..... 0.4


# - - o z 0.2 RESIDENCE TIME. msec
c 33 -0-- 110 ts 280

• 420

0.0 '---
..........----'""---
.........---I._

................_ ................_"'---.....L..--JL.....---'

1500160017001800 190020002100 TEMPERATURE, of b) Urea

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

### o 50 250 0 NH3 (9) /:i NH40H (I) 200 0 Urea (I) E Co 150 Co
en M 100 

# = z

o0.0 0.1 . I 0.2 0.3 0.4 0.5 Residence Time, seconds

0.5 0.4 0.2 0.1 

# oL... .-..J.
.........**_....s:...:::::;::I:::i:::::;;tEc~** 

## .......................J

0.0 250 /:i NH40H (I) 0 Urea (I) 200
E c. 150 c. Ii en M 100 

# = z 50

Residence Time, seconds b) 18500 F Figure 5. NH3 Profiles along the Combustor (NINO = 2.0; NOi = 125 ppm)10 0 1600 of 8 

### t:. 1750 of E 0. 6 Cl 1850 of 0. 0 4 <> 2000 of N z 2 0**o~o-** 0.1 0.2 0.3 0.4 -0.5 Residence Time, seconds a) NH3 (g) 10 0 1600 OF 8 t:. 1750 .oF E 0. 6 0 1850 OF 0. 6 4 <> 2000 OF N z 2 00.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds b) Aqueous Ammonia (NH4OH) 20 0 1600 of 15 

### t:. 1750 .oF E 0. 0. 0 1850 OF 10 0

N <> 2000 of z 5 00.0 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)0.5 0 1600 of 0.4 tJ. 1750 *F 0 z 0.3 <1 0 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 

# - - 

# - 0 1850 of 0 0.2 

# - N z 0.1 

# -**~r-1** "I" ..., 0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds b) Aqueous Ammonia (NH4OH)
1.0 0 1600 of 0.8 tJ. 1750 *F 0 z 0.6 <l 0 1850 of 

# - 0 0.4 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 (NOj 

## =125 ppm, NINO 

## =2.0)c 25 o 50 o 100 6 200

• 500 RESIDENCE TIME. msec

0.0 L.-

........_L.-

........._L.-

........___JL...-
........----l_

........---I._

........---J

1500 1600 1700 1800 19002000 2100 TEMPERATURE, of a) Ammonia ctl c 0.4

0.2 

### o z :=- 0.8 ctl



# - - c 

# o 0.6 Z 

# -**-~**

1.0 RESIDENCE TIME. msec 0.8 ctl C 25 c 0 50 

# - 0.6 0 Z 0 100 

# - - ctl 6 200 c 0.4



# - • 500 

# - 0 Z 0.2
0.0 L.-

........_.L..-

........_.L-

........___JL...-....I----lL...-
........---lL...-.....I...----l

1500 1600 1700 1800 190020002100 TEMPERATURE, of b) Urea
Figure 8. Calculated Effect of Temperature and Time on NO Removal (NOj 

## =125 ppm, NINO 

## =2.0)500 200 300 400 RESIDENCE TIME, msec 100 5 25 TEMPERATURE. of
0 1500 20 6 1700 E [] 1800 Co 15 Co 1900- 0 0 C\l 2100 Z 

# • 10

a) N20 Concentration, ppm

60 TEMPERATURE of 50 0 1500



# .. 1700 <f!. 40 1800 [J 6 z 

## • 1900 0 30 N 

## • 2100 Z 20

10

RESIDENCE TIME, msec

Figure 9. Calculated N20 Profiles (Urea, NINO = 2.0; NOj 

## =125 ppm)0.5 0.4 0.3 0.2 0.1 0.2

0.0 r'I-

......-...-................................-.._.........."'---...-.._

................................... 0.0 0.2 0.0 0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds a) 17500 F

1.0 0 NH3 (g) 0.8 6. NH40H (I) [J Urea (I)

# ~: 0.6

0.4 1.0 0 NH3 (g) 0.8 6. NH40H (I) [J Urea (I) 

# r 0.6

z I I

..**_~** 0.4 --

Residence Time, seconds 

### b) 18500 

### F
Figure 

### 3. Normalized NO profiles versus Residence Times 

### (NOi = 

### 125 ppml 

### NINO = 

### 2.0)1.2


# - ttl :: 1.0 c: 

### 0 0

.8 Z 

# - ;0.6-- c: 

# g- 0.4 Z 0.2 RESIDENCE TIME. msec ---0-- 33 110 ts _280.

• 420

0.0 1...-

.........---"_

.............._01...--'-----'-_""'-
........_""'"---'-----'

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

1.0**....---r----r-"'T"""---r--..--....,....-,.......-r----,.-~"""T"---,** 

# ....**~----_a_--_----** C

_ 0.8 eu ;:: c: 

## g 0.6 Z ::::::.. 0.4 

# - - o 

### z 0.2 RESIDENCE TIME. msec c 33 ---0-- 110 A 280

• 420

0.0 L..--'--.....I._

..............._""'"--...L----I_...L...
......._.J....,.
.........---I

1500 1600 1700 1800 190020002100 TEMPERATURE, of b) Urea

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

# =125 ppm, NINO

# =2.0)

### o NH3 (g)

[J Urea (I)



### o 50 100 200

150 

### e c. c.**-~-** UJ (') :%: Z



### o0.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds

0.5 0.4 0.3 0.2 0.1 

### o

# L..
...........L.
..............

### ~::::i:J:::i::i:tI:c::::=;a....... ...........

## ..J 0.0 250 A NH40H (I) [J Urea (I) 200


### e 150 c. c.
UJ (') 100 :z:: z
50

Residence Time, seconds b) 18500 F 

### Figure 5. NH3 Profiles along the Combustor (NINO 

### = 2.0; NOi = 125 ppm)10 0 1600 of 8 A 1750 of E c. 6 [J 1850 of c. 

### 0 4 0 2000 of N z 2 0

-0:0---- ---0:1- - ---0:2-------

- - -0:3--

- --- - 0.4 0.5 Residence Time, seconds a) NHS (9) 10 0 1600 of

8 l:!t. 1750 *F E of c. 6 [J 1850 c. 

### 0 4 0 2000 of N z 2 00.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds b) Aqueous Ammonia (NH40H) 20 0 1600 of 15 6 1750 *F E c. c. [J 1850 of 10 

### 0 N 0 2000 of z 5 00.0 0.1 0.2 0.3 0.4 0.5 Residence Time, seconds C) Aqueous Urea Figure 6. N20 Concentration Versus Residence Time (NOj = 125 ppm; NINO = 2.0)0.5 0 1600 of 0.4 Ii. 1750 "F 0 z 0.3 <l [J 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 I I I I- 0 1600 of 0.4 

# · 0 Ii. 1750 "F z <l 0.3 

# · 

# - [J 1850 of 0 0.2 

# · N z 0.1 

### l:- 

# ·**~.A:::I** 1""'1 -""" FI '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 Ii. 1750 "F 0 z 0.6 <l 0 1850 of 

# - 0 0.4 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 (NOj 

### = 125 ppm, NINO 

### = 2.0)::::::- 0.8 as 

# - 0' 0.6 Z 

# -

- - -..-.,----------------------- ----------- --- as l: 0.4


# - - o z 0.2 RESIDENCE TIME. msec c 25 o 50 o 100

---- - 6 200

• 500

0.0 L..........L-.......I_
.........--'-_....&..........L._
........--L-----''--
.........--L-----I

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

1.0 RESIDENCE TIME. msec ::::::- 0.8 C'll c 25 

# - l: 0 50 

# - 0.6 0 Z 0 100 

# - - as 6 200 l: 0.4


# - • 500 

# - 0 Z 0.2
0.0 L...-
........_ .........&..........I_

.........--I._....&....
........._ ............L._L..-......I

1500 1600 1700 1800 1900 2000 2100 TEMPERATURE, of b) Urea
Figure 8. Calculated Effect of Temperature and Time on NO Removal (NOj 

# =125 ppm, NINO 

# = 2.0)500 200 300 400 RESIDENCE TIME, msec 100 5 25 TEMPERATURE, of 0 1500 20 6 1700 E D 1800 c. 15 c.
_.- --- --- - ---- 

### -.-----

0 C\I 2100 Z 

# • 10

a) N20 Concentration, ppm

60 TEMPERATURE OF 50 0 1500



# .. 1700 40 1800 c 6 :z 

## • 1900 0 30 ('\I 

## • 2100 :z 20
10

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

### = 2.0; NOj 

### = 125 ppm)