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

HOx Control in a Brown Coal-Fired Utility Boiler 

John E. Ho fmann 

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 coalfi red boi 1er. The NOxOUT Process uses urea and enhancer chemi ca1s for the 

reduction of NOx 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, a commercial 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. 

INT RODUCT ION 

The Federal Republic of Germany is recognized as a world 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 a maximum of 200 mg/NmJ (approximately 100 ppm) for 

all boilers in e-xcess of 300 MW th 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 of Germany. One of the major fuels of RWE 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. A high 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 qual ity coal s 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 selective catalytic 

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 a relatively low cost retrofit NOx control technology. 

The NOxOUT Process can be installed with a short downtime and is applicable to 

a very broad range of fuels 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 of reduction. Hence, the 

NOxOUT Process is applicable as a primary 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 + NH 2CONH + 1/2 O ------) 2N + COz + 2H z 2 z zO

The reaction takes place at a temperature of about 925 - l,1000e. 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 appl ication 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 sulfur content of RWE 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 NH 3 emissions, or 

·slip·,below 3.8 mg/Nn( (approximately 5 ppm) 

7A-54 
the 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 

were expected after the envisaged install at ion of combust ion modi ficat Ions. 

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 0 boiler 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 of the backpass after the primary superheater. 

A number 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 cool ing and atomization at levels two and three due to a 1imited availabil ity 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 5 ppm at all operating conditions. 

Based on experience from the 0 boiler, 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 injectors were used at all levels. Steam was 

used as the cool ing and atomizing fluid for all injectors. 

TEST RESULTS - D BOILER 

A. Temperature and Composition Profiles 

Pri or to the commencemen t of NOxOUT irlject ion, tempera tures were measured ateach 

of the 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 

(leve 1 3). 

7A-55 

-., 

.' .. .,.. " '.', .. :,". 
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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 1 and 2 were 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 0t concentrations differed at the three levels. NOx 

values were highest at level l. Higher NOx concentrations recorded at level 2 

were associated with higher Oz concentrations at this level. The CO levels were 

found to be significantly hlgher at level 1 than other levels. The higher concentration of CO at level 1 indicates that complete burnout has not occurred 

until after this point. 

B. tiQx..]eductiQo. level 1 Injection 

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 add ition of enhancer cou1d result in either increased NOx reduct ion, 

decreased NOx reduct ion or no change in NOx reduct ion. A decrease in NOx 

reduction impl ies 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 

reaction temperature window in that by-product NH formation is suppressed while 

NOx reduction is only slightly diminished (11). 1

The amount of NOx reduct ion achieved in these experiments impl ies 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 of HOx). 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 1 and 2 to 

determine if multiple level injection would significantly (A) increase chemical 

utilization, (8) reduce NH1 slip, and (C) increase the HOx reduction. 

Results from injection of urea and enhancer at level 1 versus levels 1 and 2 at 

comparable test conditions are contained in Table 1. 

7A-56 

j

j

j

j 

t

I 
Generally, it can be concluded that urea utilization increases when 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 NHJ slip 

from level 2 was the result of chemical impingement on the superheater platens which were within 5 feet of the 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 off occurs when NOx reduction has to be forfeited to maintain 

low NH3 level s. 

Figure 4 shows a comparison of ammonia slip versus 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 collection was 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 

previously described, prior to injection with different configirations of burner 

sl its in service. Only sl ight variations in daily average 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 indicate no significant difference in process performance .. The amount 

of urea required to achieve a given level of NOx 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 1 revealed 

significant differences for the modified conditions (TJb1e 2). 

7A-57 
· 

, . Low excess air resulted in a higher temperature and a lower 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 3 and compared with 

data obtained at normal 10~ load conditions. 

During the experiments at higher NSR, enhancer alone was injected at level 2 to 

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 a target level depends upon the temperature at the point 

of injection. The average temperature at level 1 varied over the range of 954 

to 1,065°C. Within this temperature range, the amount of enhancer required to 

meet NH) limits increased from 1 part 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 of NOxOUT injection and soon after the C2 boiler returned 

to stable conditions with the newly installed combustion 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 

19m had the effect of extending the primary combustion zone. The first injection 

level was within this extended combustion zone. As a result of these conditions, 

the values for both HOx and CO were extremely erratic and averages were 

considered to be meaningless. 

Although temperature 1eve1sat 19 meters wO'll d appear to be conduc i ve 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 of NOx reduction required to achieve <200 mg/NmJ proved 

to be only about 35~ which could be readily achieved at level 2. 

7A-58 
B. 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 utilization were
 

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 D boiler
 

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 that the process results were irdependent of the specific burner 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
 

ach 1eve <200 mg/Nn? was about 1.5 and reagent ut 111 zat ion is lower than that
 

achieved at 10~ load. The reason for thts I~ postulated to be the higher CO
 

concentration at 8~ load. As previously noted, 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
 

period, 

slip was 

64 

a very 

analyses 

important 

of ammonia 

consideration 

were to be 

for 

undertaken 

RWE. During 

to determine 

the four week 

compliance 

acceptance
 

with
 I

the 5 ppm 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 NHJ 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 bo 11 er was ut l1i zed 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 profile at 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 sl i p. 3 

7A-59 
Elimination 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. 

A total 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 5 ppm. 

CONCLUDING REMARKS 

The results of the above described projects at the t~o brown coal fired boilers 

can be summarized as follows. 

A NOx 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 NH J 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 is effective at various 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 easily retrofitted on an existing boiler with 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 of Acid Rain", Scientific American, Vol. 259, 

No.2, 30-38, August, 1988. 

2.	 Bruck, R. I., "Decl ine 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 of NOx 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 Concentration of Pollutants 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 of Nitrogen 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 of Nitrogen - 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 by Ammonia", Paper No. 88-67, Western States Section/The 

Combustion Institute Fall Technical Meeting, Dana Point, CA, October, 1988. 

, 

! 

I 

,I 

7A-61 

~'

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TABLE 1 

SINGLE VS. TWO LEVEL INJECTION 

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.ratio ot NHi moles injected 

divided by the initial moles 01 NOx 

(2) Weight ratio 01 Enhancer to Urea 

TABLE 2 

EFFECT OF BOOS ON TEMPERATURE AND GAS COMPOSITION 

Conventional Low Excess Conventional 

Excess Air Air Excess Air 

Operation 100% Load 100% Load 60% Load 

Level 1 

Avg. Temp?C 1,008 1,065 954 

Avg. NOx mglNm] (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. NOx mglNm (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) Corrected to 60/0 ° 2 , 

7A-52 
TABLE 4 

C2 BOILER - TEMPERATURE AND GAS COMPOSITON 

Load ____100% _ _ 80% _ 

Level 1(19m\ 2(25m) 1(19 m) ·2(25 m) 

TemperatureJ

o C 

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. D BOILER 

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-65 
NOx 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 NO x 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 

EPA Project Officer:
 EPRI Project Manager:

William P. Linak
 David Eskinazi 

U.S.	 ~nvironmental Protection Agency Electric Power Research Institute
 

Air and Energy Engineering Research Laboratory 3412 Hillview Avenue


Research Triangle Park. NC 27711 Palo Alto, CA 93404

AIR AND ENERGY ENG1NEERING RESEARCH LAGORATORY 

OFF ICE OF RESEARCH AND DEVELOPt-IENT 

U.S.	 ENVIRONMENTAL PROTECTION AGENCY 

RESEARCH TRIANGLE PARK, NC 27711 

REPRODUCED BY 

U.S. DEPARTMENT OF COMMERCE 

NATIONAL TECHNICAL INFORMATION SERVICE 

SPRI~JGFIELD. VA. 22161