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 South Pointe 

Laguna Hills, CA 92653 

D.P. Teixeira 

Pacific Gas and Electric Company 

3401 Crow Canyon Rd. 

San Ramon, CA 94583 

A pilot-scale experimental study was performed to determine the effect of residence 

time on SNCR processes. Test results showed that residence times less than 250 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 N 20 emissions since N20 reduction reactions do not have sufficient time 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 occurs both in the main radiant furnace and within the furnace 

convective sections. When the temperature window is in the convective sections, 

chemical injection is limited to the cavities between convective tube banks. Depending 

on the specific furnace design, residence times in these convective cavities can range 

from 30 to 100 milliseconds. These short cavity residence times, coupled with steep 

temperature gradients, can limit potential NOx removal performance. 

While an extensive amount of pilot- and bench-scale work has been done on SNCR 

processes, most of this work has addressed process parameters including SNCR 

chemical type, amount of chemical, temperature, initial NOx levels, and additives. 

Little work has focused explicitly on the effect of residence times. Sun, et al., used 
chemicalldnetic calculations to investigate residence time effects (1). In this work, it was 

shown that residence time was most important as the temperature decreased below the 

temperature for peak NOx removal; on the high temperature side of the temperature 

window, it was less important since reaction rates increase exponentially with 

temperature. 

The current study was undertaken to experimentally study the effect of residence time 

on SNCR processes. This work was done in support of an 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 of 35 milliseconds at full load, it was decided that 

a pilot-scale study of residence time would be beneficial in interpreting the full-scale 

data. 

The objectives of the present study were to experimentally determine the effect of 

residence time on SNCR processes and to determine the differences in rates of NOx 

removal between anhydrous ammonia (NH3), aqueous ammonia (N'H.iOH) and 

aqueous urea. 

When addressing SNCR residence time effects, three characteristic times need to be 

considered: 

• mixing of the SNCR chemical with the combustion products 

• evaporation and release of reactive nitrogen compounds (for aqueous solutions) 

• chemical reaction times 

In any experimental approach, it is difficult to separate each of the 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 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 on SNCR performance. 

To support the experimental results, a limited amount of chemicalldnetic calculations 

were performed. The calculations were done using a PC version of CHEMKIN (3) along 

with the Bowman and Miller mechanism for nitrogen chemistry (4). 
Pilot-Scale Facility 

A schematic of the pilot-scale facility used for the current tests is shown in Figure 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 

section is refractory lined, 6 in. in diameter and 8 feet long. At the firing rates used for 

these tests, the residence time in the test section is nominally 0.5 seconds; the 

temperature drop along the test section is 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 of the 

test section which provides a residence time resolution of about 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 section located just 

upstream of the 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 of the venturi throat. The spray was directed 

downward (i.e., co-flowing with the combustion products). The solutions were 

pumped with variable speed peristaltic pumps and metered with rotameters. In order 

to maintain a constant thermal environment in the test section when aqueous solutions 

were used, the total amount of liquid injection was held constant at nominally 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 of 2.0, 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 of gas analyzers (NO/NOx, 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 of residence time on NO reduction for the three 

chemicals. Subsequently, the effect of residence time on byproduct emissions (e.g., 

NH:3, NzO) are discussed. 

NO Reduction 

The effect of residence time on NO reduction for anhydrous ammonia (NH3)g, Nlf40H 

and aqueous urea is shown in Figure 2 for chemical injection temperatures of 1600°F, 

1750°F and 1850°F and 2000°F. This figure shows data collected at nominal30 msecond 
intervals along the combustor test section. During this test series, the combustor was 

operated at a constant combustion product flow rate. The overall residence time in the 

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. 

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 product flow is nearly complete. This 

was felt to be a more representative temperature than the temperature entering the 

injection venturi since the concentrations of the 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 concentration was 

nominally 2.8 wt%.) 

A number of observations can be made from the data shown in 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 of the 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 can be 

gained by comparing the results in Figure 2 for anhydrous ammonia, NI-is(g), and 

aqueous ammonia, Nli40H (1). For these two cases, the primary differences are 

expected to be the evaporation of the Nlf40H and the release of the 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, which is on the high temperature side 

of the SNCR temperature 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 can be attributed to either 1) the 

somewhat slower release of the chemical with more NHs reaching the cooler region of 

the test section; or 2) continued evaporation of the aqueous phase beyond sample port 

number 1 (33 mseconds) resulting in some cooling of the 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 

NHs to NO beginning to play a more important role, the net affect is an overall decrease 

in the NO removal rates. Secondly, at higher temperatures, the evaporation and 

chemical decomposition rates 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 can be seen that the N'H3 emissions with aqueous 

ammonia decrease much more rapidly than at 1750°F. Again, the Nli3 profile with 

aqueous urea is different. At this 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 NHs concentration with 

urea injection was only 150 ppm, slightly over one half of the injected nitrogen. 

NzO is also a product of SNCR process, with urea producing higher N20 levels than 

ammonia injection (5). NzO profiles were also measured along the length of the test 

section during the course of the experiments. Figure 6 shows the NzO concentrations as 

a function of residence 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 on NzO 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 of nominally 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 in excess of 250 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 seen to 

increase monotonically with both residence time and temperature. At a temperature of 

2000°F, N20 levels peak at a residence time of 200 mseconds and then begin to decrease 

as N20 destruction reactions predominate. 

The normalized N20 profiles show similar trends (Figure 7). With ammonia injection, 

the normalized N20 levels are under 10%. At higher temperatures, normalized N20 

levels decrease with increasing residence times. With urea injection at long residence 

times, normalized N20 concentrations increased from 15% to near 40% with increasing 

temperatures. More importantly, at high temperatures and short residence times, N20 

levels approached 60% of the NO reduction. From a practical standpoint, this suggests 

that for applications with short residence times (e.g., injection in convective cavities), 

NzO levels may be enhanced. In fact, the residence time effect seen in Figure 7c with 

urea injection explains the relatively high N20 production observed during the PG&E 

Morro Bay SNCR demonstration(2). 
At 2000°F, the temperature is beyond the SNCR temperature 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 of NO 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% of the 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% of the reaction completed in about 100 

mseconds with the ammonium compounds. In comparison, aqueous urea requires 

about 180 mseconds to complete the same 75% of the reaction. 

To better compare the effect of residence time and temperature, the data in Figure 2 for 

urea and ammonia have been cross-plotted as a function of temperature in Figure 4. 

With ammonia injection, a marked decrease in NO reduction occurs at residence times 

less than 110 mseconds. Also, consistent with 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 I sec), and the slower release 

of reactive 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 in Figure 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 in the formation of 

ammonia, with maximum NH3 concentrations occurring after 100 mseconds. This is 

consistent with a more gradual release of reactive nitrogen compounds to the gas phase 

with urea injection. With urea, it can be speculated that the aqueous solution must 

evaporate to near saturation before substantial decomposition of the urea occurs 

releasing reactive nitrogen compounds to the gas phase. Secondly, at 1750°F, peak NH3 

concentrations are only 100 ppm, whereas 250 ppm of reactive nitrogen is being injected 

as urea. These lower measured concentrations of Nli3 would be consistent with a urea 

decomposition mechanism producing NH3 and HNCO (i.e., NH2CONH2 -> NH3 + 

HNCO). 
Chemical Kinetic Calculations 

To support the pilot-scale tests, chemical kinetic calculations were performed using a 

PC version of CHEMKIN(3) and the Miller Bowman mechanism for nitrogen 

chem.istry(4). The calculations were performed over a temperature range from 1500-

21000F, for an initial NO level of 125 ppm and NINO molar ratio of 2. The calculations 

also incorporated a temperature gradient of 450°F I second. Calculations were made for 

both ammonia (NH3) and urea. The urea calculations assumed that the urea 

decomposed instantaneously to NH3 + HNCO. 

The calculated histories of NO are shown in Figure 8 for both ammonia and urea. The 

calculated NO profiles are in qualitative agreement, although the absolute levels of NO 

removal are higher than observed experimentally. With N'H3 injection, calculations 

show some NO removal even up to an injection temperature of 2100°F; whereas 

experimentally, additional NO was formed above 2000°F. This could be 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 

of injection. Thus, some of the injected ammonia experienced higher temperatures 

during the mixing process. This effect would 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 

of NH3 + HNCO assumed for the calculations. 

The calculated NzO profiles versus time are shown in 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 concentration normalized by the NO removaL These 

calculated NzO profiles can be compared to the experimental profiles in Figures 6c and 

7c. The NzO profiles are in good qualitative agreement with the experiments. The 

calculated NzO profiles further support the observation that short residence times can 

lead to enhanced levels of NzO emissions from SNCR processes. In fact, consistent with 

the experiments, the calculations show that at residence times between 50 and 100 

m.seconds over 50% of the NO reduced can be converted to N20. 

Conclusions 

The results of the present study have shown the importance of residence time for SNCR 

processes. Specifically: 

• The tests showed that for all chemicals tested, residence times on the order of 250 

mseconds were required to substantially complete 80% of the NO removal. This 

residence time will vary somewhat for full-scale application, since mixing and 
evaporation times will be dependent on site-specific factors which may differ 

from the pilot-scale. 

• For short residence time applications (t<lOO mseconds), it is 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 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°/o Of 

the NO removal observed at the combustor exit. 

Chemical Temperature 

NH40H 

Urea 

Time for SO% of the 

Overall Removal 

70mseconds 

110 mseconds 

• At residence times below 100 mseconds and temperatures greater than 1850°F, 

N20 levels can be relatively high for 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 Combustion NOx Reduction with Urea: 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 of Nitrogen Chemistry in 

Combustion." Progress in Energy and Combustion Science, 15,287 (1989). 

5. Muzio, L. J., et al., 'N20 Formation in SNCR Reduction Processes," EP A/EPRI 1991 

Joint Symposium on 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. 

GAS 
1.00 

E 

Q. 0.80 

Q. 

-E 

Q. 

Q. 

o· 0.60 

z 

] 

: 

c 0.40 

-

0 

z 

a; 

..5 0.20 

-

0.00 

0.0 0.1 0.2 0.3 0.4 0.5 

Residence Time, seconds 

1.00 

E 

Q. 0.80 

Q. 

-E 

Q. 

Q. 

0 0.60 

z 

] 

: 

c 0.40 

-

0 

z 

c 

c 0.20 

;:: 

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 

a. Cl Urea (I) 

a. 

0 0.60 

z 

ii 

:;::: 

] 0.40 

-

0 

z 

iii 

c 0.20 ;;: 

0.00 

0.0 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 

0.00 

0.0 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 

N 4 

z 

2 

0 

0~0~ 

10 

8 

E 

c. 6 c. 

6 

N 4 

z 

2 

0 

0.0 

20 

15 

E 

c. 

c. 10 

0 

N 

z 

5 

0 

0.0 

0 

A 

Cl 

<> 

0.1 0.2 0.3 0.4 6.5 

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 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 Of 
0.5 0 1600 OF 

0.4 tJ. 0 1750 *F 

z 

<1 0.3 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 

N 0.2 ~ - z 

0.1 ~ - ~.1:] _...... 

"'" 

'-" 

0.0 

0.0 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 

tJ. 1750 *F 

z 

<l 0.6 D 1850 OF -

0 0.4 N 0 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) N2o 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 1 800 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._....._.....1 

RESIDENCE 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 

c. 150 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 

0 

0.0 

20 

15 

10 

5 

0 

0.0 

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 °F 
0.5 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) NH3 {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 - 0.0 

0.0 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 

<I 0.6 [J 1850 Of 

-

0 0.4 IN 0 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