13 :2 -l 'B'l iO S 9!33 32-lO**.-\LCO** 

### FrEL TE C H @ OO-l t 014 

# Reduction of NOx Emissions from Cement Kiln/Calciner through the Use of the 

# NOxOUT® Process

By W.H. Sun, M.J. Bi snett, and D

.W. Kirk, Nar co Fuel Tach and H.E

. Stauch and J

. Hille, Ash Grove Cement Company



### ABSTRACT Post-combustion urea injection has proven to be a n effective method i n controllingNO;r;from va rious combustion. sources . This process, a s elective non-catalytic reduction process known 

### as NOxOU'J"', 

### has been successfully demonstrated in a cement kiln Icalciner operated by Ash Graue Cement

. Testing was done under ten different kiln 

### I calciner operating conditions. Usinc three to four inje ctors, NOx was efficiently reduced from 350 to 600 pounds per hour (3.5 to 6

. 0 lb Iton of clinker ) to less than l 00poundsper hour (1

. 0 lb I ton o f clinker ). This calculates to a NOx reduction of >80% for most cases. Chemical utiliza · tion was greater than 50%

. A high degree of mi:r:ing and a long residence time at an appro priate tempera· turepresent in thepreheater tower contributed to these excellent resu lts. An average ammonia slip was four ppm above a baseline level at normalized stoichio· metric ratio of1

. Based on this demonstration, cement kiln 

### Icalciners have been identifi ed as an ideal application for the NOxOUTProcess. NOx was efficiently and effectively reduced with minimal by-product emissions and uirtually no effect on plant operations

. 

### INfRODUCTION The oxides 

### of nitrogen (NOx) affect the environment by contributing to acid rain, ground level ozone, and photochemical smog. The Clean Air Act Amendments C CAA) of 1990 address the control ofNOx emissions in Titles 

### I (non-attainment) and 

### IV (acid rain) and state regulators a r e required to submit plans (SIPs) to comply with the CAA. In addition to fossil

-fuel fired utility boilers, which are the major source, industrial sources ofNOx such tts proce ss heaters, incinerators and kilns may be regulated depending on their emis· sion rate and the level of attainment of the National Ambient Air Qualilty Standards in the area of these sources. NOx emissions from cement kilns are significant (>1000 TPY) due to the process requirements. In a cement kiln , gas tempera t ure is raised above 2700°F to form
" clinker"

. This heat is provided by burners whose peak flame temperatures can exceed 3000 °F. Since NOx formation during combustion increases with temperature 

### and oxygen content, NOx concentrations resulting from 

### such high temperature process can exceed 1000 ppm . The thermodynamic equilibrium concentration of NOx at 3000QF and 1% oxygen with natural gas is 1500 ppm. In addition, NOx emission increases with nitrogen content in the fuel**termE~d,** fuel-NOx

. The NOx generation from fuel bound nitrogen is also sensitive to oxygen content in the flame zone. Utilizing its sensitivity to oxygen content, NOx emission can be reduced through combustion modification

. While maintaining the flame temperatlll."e, combustion air can be staged to provide a slightly fuel-rich condition at the flame zone . At 3000°F, the equilibrium NOx concentration decreases to 500 ppm at 

### the stoichiometric condition and even lower under oxygen-starved conditions. Additional air is injected downstream of the peak tem

perature zone to complete the combustion. A combustion modificat ion 

### is an effective method to control NOx but the extent of NOx control 

### is limited because 

### a high temperature zone, which generates NOx, must still be provided for the process. 

### SNCR Process Selective non-catalytic NOx reduction 

### (SNCR) processe s have effectively 

### controlled NOx em.issions in various 

### type : of boilers firing all types of fossil fuel or waste-fueL 1.2 .• Unlike combustion modifications. ammonia' or ureas is injected in the post-combustion zone, typically at tem

peratures between 1600 and 2200 ° F. Therefore , the process does not affect the burner operations. The levei ofNOx removal depends on the**res.~;e nt**  feedrate and car. range from 30 to 70%. Some critical process**parameter ~**  are temperature , residence time , mixing between**th ~**  reagent and flue gas , and uncontrolled NOx level.

Presented at the International Spec i a l

ty Conference on Wastll Combustion i n Boil ers and Industrial Fvrnaees, sponsored by A'

r & Wa st e Managemen! Associ ation, Kansas C ity, M issour i, Apri/2 1. 199 4

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A leading SNCR process that injects stabilized urea to control NOx is the NOxOUT Process, marketed b y Nalco Fuel Tech

. In the process, NOxOUT·A, a stabi· lized urea solution, is injected into a furn!lce and reacts with NOx in the gas phase to produce molecular nitrogen, water, and C0 2• Urea+ Nitrogen+ Oxygen-.> Nitrogen +Carbon +Water Oxide Dioxide A**dime~ionless** parameter that describes the reagent flowrate 1s the normalized stoichiometric ratio (NSR). This ratio is defin ed as an actual molar ratio of urea to inlet NOx divided by the stoichiometric molar ratio. The reagent utilization is the ratio ofNOx reduc

tion and NSR. Nalco Fuel Tech expanded the technology by devel· oping chemical injection hardware , widening the applicable temperature range , and process control expertise required for commercial applications. The design of a system is guided by a computational 

### £1 uid dynamics (CFD) and chemical kinetic (CKM) models, in addition to results from field measurements. These**co~puter** models determine the ideal temperature**reg~o n**  for chemical reaction and the optimum injection strategy to distribute the reagent. The NOxOUT Process also provides effective load following capabilities through control of reagent concentration. multilevel injection, droplet size and spray patterns, and the introduction of chemicals at selected injector l ocations

. There 

### are substantial benefits gained from the application of the NOxOUT Proce$S compared to first generation NOx control technolo· gies, such as ammonia injection. These benefits are briefly SWlllnarized below:
• Use of non-toxic, non-hazardous chemicals
• Potentially lower capital cost due to the lack of large system compressors and elimination of anhydrous ammonia storage, handling, and safety equipment
• Lower operating costs resulting primarily from minimization of gas ( steam or compres:sed air) requirements
• Inherently more effective control ofspray patterns and chemical distribution for better mixing with the use of liquid rather than gas -based reagents, thereby resulting in better chemical utilization
• Chemical enhancers which can be used to improve control of potential by-product generation while reducing NOx over an expanded t emperature range There are over 100 commercial applications of the NOxOUT Process in the world and over 200 short· :erm test applications. Recently, the NOxOUT Process has been demonstra ted at a cement plant operated by Ash Grove Cement in Seattle. CE:l\IIENT KILN/CALCINER Ash Grove Cement in Seattle operates 

### a calcinerlkiln that processes about 160 tons of solids per hour to produce -100 tons of clinker

. This unit is an energy efficient design that consists of a kiln and a preheater/ precalciner

. The preheater tower, as shown in Figure 1, is made up offive cyclones and a calciner

. The plant is equipped with an elaborate feed system, a finishing mill , and storage silos. The entire plant is well inst rumented and automated. Combustion products flow countercurrent to solid flow. Hot flue gas is generated with a burner firing natural gas or coal at one end of a kiln

. Gas flows through 

### a slightly inclined rotating kiln to a calciner. Inside the 

### kiln, lime, silica, and clay undergo reac· tions to form clinker which is subsequently milled to produce cement
. The calciner is at the bottom of a preheater tower and is about 60 feet high and l4 feet in diam e ter
. To further improve fuel efficiency, gas or coal in an amount of 5 to 10% of total heat input is injected into the calciner. Flue gas enters at the bottom of the calciner and flows upwards carrying solids dropped from the bottom of cyclone #4. Solids are calcined and exit to cyclone #5. Solids are separated from the gas, dropped through a bottom chute to the bottom of the calciner, and then flow into the kiln

. Flue gas exits cyclone #5 into cyclone #4 and continues upwards to eventually reach cyclone #1. Finely groWld solids of limestone, silica, 

### clay and iron mill scale are fed into cyclone #2 and flow downwards through the cyclones. Flue gas enters the bottom 

### of the calciner at about 2100°F and cools to 550°F at the top of cyclone #1. Flue gas then flows through a raw mill, a cyclone, and a baghouse before exiting to the atmosphere

. Flue gas is analyzed at several locations : kiln exit, preheater e:cit, and stack

. NOx, CO, and 0 2 are monitored at the kiln exit while CO and 0 1 are measured at the preheater exit

. At the stack, NO:"' SOx, CO, 

### and 0 2 are measured. Opacity and flue gas flowrate are also measured at the stack. The stack emission limits for the plant are 422 pounds per hour (pph) of NOx, o38 pph of CO , and 40 pph ofSO •. Emissions of 

## so2 are well controlled from reactionS between lime and S02 to form CaS0 4 in the preheater / calciner and a raw mill

. When the raw mill needs servicing, sodium bicar bonate is injected before the baghouse to control SO. emissions

. Particulates are well con· trolled by the baghouse indicated by low opacity. NOx, however, can be higher than the limit when firing with gas in the kiln. NOx emission decreases below the limit when fired with coaL However, NOx still may exceed the limit with coal 

### if the kiln needs to operate at higher than typical kiln temperature to proces s material that is "hard to bum "

. It was desir·. 09 ·· 21 : 9 5 13 : :! 6 "Bl iOS 98 3 32-1 0**AL O**  FL"EL TE C H

## ----~----------~~~~~~----~**~** 141 006 / 01-1



# .. 0

0 0 0 Fe ed

C a l cin er fuel

K i l n 

## i ·--- - - - -- - - · · · ···· · ···- T o coal m i!ls

### -------**----~** o n sh eet 3 P reh eat er '



### · ····· · · · ·· ···--- ----- - T o raw m ill on s h eet 1 fan Figure 1 - Cement kilnlcalcin.er

? !:1111 air !Uppl y 

## 11:: I**~** 

# tE l nji:C!Org 

# I I 

## L.rCh a mocal mat uring : 

# I f1::;

r --------, :liJmp:;**~ .._** **n~ o~** 

# ~ 

# $**~~=~ L------!:..~**  'n41 ne 

### n:u a

1 e r 1



## l**Fl~orcu alkln**  Pllm:l I Plant W8 19f -------+ 

### 8
Figure 2

- NOxOUT equipment layout

able, therefore, 

### to te s t the NOxOUT Proce s s to determine its effectiveness 

### in NOx control under 

### all operating conditions and to establish its effect on other emissions and p lant o perations.

NOxOUT EQUIPMENT AND INJECTION LOCATIONS The chemical and water pumping e quipment were delivered and used in a 20 ft

. trailer

. The reagent, 

### NOxOUT

- A, w as delivered and stored in a 4 500 ga llon i nsulated tanker trailer. The equipment cons isted of a chemical recir cul ation module with an in-line K i l n f ue l

o a a a

To c linke r sto rage

chemical heater, chemical metering pumps, water pumps, chemical distribution panels , and sufficient number and type of injectors to test several spray patterns
. Inside the trailer , metered NOxOUT-Aflow and water were mix e d with a static mixer before**flow ~**  ing to the dis t ributio n panel. 

### On this panel, liquid tlowrate to each injector was 

### controlled with a needle valve and atomizing air pressure was controlled with an air regulator. NOxOUT equipment layout is shown in F i gure 2. Observation ports at the cnlciner were modified t o accommodate NFT injectors

. Three ports at the top of the ca lciner, t hree por t s halfway up the calciner , and four ports at the bottom ofthe calciner were used to inject 

### NOxOUT-A

. Gas temperature was also measured through thes e ports using a suction pyrometer. 

### RESULTS AND DISCUSSIONS The perf ormance of the NOxOUT Process was optimized through a s eries of te s ts at kilnlcalciner operating conditions listed in Table 1. Solid feedrate was steady at 160 tons per hour and kiln was fired with natural 

### gas . These conditions covered 

### a wide operating range of fuel firing and excess air conditions . At each operating condition , tests were carried out t o achieve eff e ct i ve chemical distribu tion by vary· ing the following parameters : air and liquidflowrates, type ofinjector tip, injection level, and treatment rate
. Effectiv e chemical di s tribution is achieved when a s ufficient a mount of chem i cal is di s tributed in a region where t emperature 

### and residence time are

### · --- · 13 : 2 8 'B'l i08 983 32-10**~- ~L** **CO** FrEL TE C H**08 01-1** 

Table 1 - Tested Kiln/Calciner Conditions
Fuel to Heat Input to Praheater Uncontrolled calclner calclner oxygen(%) NOx (pph)

gas 5% 1 .8-2

. 1 415-455 2" gas 9 % 2-2

.2 420-520 3' gas 5% 2-2

.2 42o-520 

### I 4 gas 5% 2

.2 500-550 

# I 5 gas 5% 2

.2

- 2.4 350-400 6 gas 5% 2.4-2.7 45o-530 

### I 7 gas 

### s•;. 2

. 3-2

.5 45C -500 

### e coa l 9% 2

. 3-2

.7 460-550 9 coal 5% 2

. 6-2.9 340-500 10 I 9%**2.~ 2**  41 

### coa 0-426

• Rawmill was off snd soeflum blt:aroaiiBtB injscrlon wA$ on

from several operating conditions showed NOx reduction was lower by 20% at NSR 1

. 5 when oxygen increased from 2% to 2.6%

. Even at this reduced efficiency, the reduction was still high : -50 % at NSR 1. NOxOUT-A injection through three different elevations in the calciner showed similar reductions, indi

cating that process requirements are satisfied as long as 

### the reagent i.s injected in the calciner. Baseline NOx varied from 350 pph for condition 5 to 550 pph for condition 4. This variation in the baseline had negligible impact on NOx reduction which remained at -60% at NSR 1. The NOxOU'l' Process , like any other chemical reaction, requires good mixing between the reagent and NOx and appropriate temperature and residence time. In this kiJnlcalciner application , the reagent was well mixed with the flue gas due to highly turbulent flows in the calciner and cyclone preheater and an appropriate placement and use ofNFTinjectors

. Gas temperature of about 1530° F is at the lower end of the process temperature window

. However , high CO concentration from coal or gas oxidation inside the calciner shifted the requ ired process temperature to a lower temperature
. 6 The calciner temperatures, therefore, became more optimum as the result of elevated CO concentration. The available reaction time at this temperature exceeded 1 second in the calciner and another 

### 1-2 seconds in cyclone #5. This reaction time of 2-3 seconds is higher than reaction times of 0.5 U> l second in other applications

. As the available reaction time increase s, the required temperature shifts U> a lower temperature and NOx reduction efficiency increases

. 6 This combination of long residence time, good mixing , and an appropriate reaction temperature (a result of elevated CO and long residence time ) gave excellent process performance

. A typical heat input to the calciner was about 5% of the total heat input to the kilnlcalciner. Increasing this heat input had a negligible effect on NOx reduction when gas was injected into the calciner. Changing the calciner fuel from gas to coal or decreasing the coal feedrate decreased the reductions. This decrease was likely caused by an increase in oxygen concentration that accompanied coal injection

. When coal is injected into the calciner, air carries pulverized coal from a mill to the calciner. 

### This additional air increased preheater oxygen from 2 to 2.5% for gas U> 2.4 to 3

. 3% for coal. High oxygen preheater condition with gas as the calciner fuel was virtually the same as the coal fired cases with high 

### 0 2• Similarly, improvement in reduction with increasing coal feedrate is because of reduced preheater oxygen. As indicated in Table 1, oxygen was the highest at 2.8- 3

. 3% under 5% coal and 2.6-2

. 7% with 9% coal feedrate

. 

### BY-PRODUCT EMISSIONS SNCR processes can release unreacted ammonia, known as "ammonia slip", and increase CO above baseline levels. A part of the NOxOUT Process technology is a method and know-how to minimize byproduct emissions. During this test, NOxOUT-A injection increased concentrations of 

## co and 

## so2 in stack gas . This increase was related to oxygen concentration at the preheater exit and can be minimized by injecting through the bottom ports , operating the calciner at oxygen greater than 2.3% , or by limiting the NOxOUT-A flowrate 

### to less than NSR of 0. 7.


# co The CO emissions exiting the preheater were higher than from the kiln. At the kiln exit , CO was typically less than 0

. 02 % while the preheater exit gas contained between 0.08 and 0.1%

. This CO increase in preheater is the result of gas or coal firing in the calciner in addition to oxidation of organics in the raw mix

. The temperature in the calciner is 1500 to 1550°F and oxygen concentration is typically less than 1%. Such condition delays combustion of gas or coal resulting in an elevated CO emission. In Figure 6, CO at the stack corrected to 10% oxygen is plotted against preheater exit oxygen concentra

tion for several chemical injection rates (NSR ) and without injection. The best fi t curves through each set ofdata are also presented in the figure. The stack CO emission i ncreased with decreasing preheater exit oxygen and with increasing NSR. This CO increase was negligible at preheater oxygen concen· tration greater than 2.4% and at NSR less than 0.7. When the reagent was injected through the bottom

### --· 13 : 28 '5'1 i 08 983 32.!0**~. -\LCO**  F'l'EL TE C H**~008 0l.l** 

Table 1 - Tested Kiln/Calciner Conditio n s Fuel t o Heat Input to Preheater Un controlled calc l ner calc:lner oxygen(%) N Ox (pph)

gas 5% 1.8-2.1 415-455 ! 2. gas 9%**~-2.2** 420-520

3" gas 5% 2

- 2

.2 420-520 I 4 gas 5% 2.2 500-550 5 gas 5% 2.2-2.4 350-400 6 gas 5% 2.4-2.7 450-530 

### I 7 gas 5% 2.3-2

. 5 45o-500 

### e coal 9% 2

.3-2.7 48()-550 9 coal 5% 2

.6-2.9 34CJ-500 10 coal 9% 2.C>-2

.2 410-426

• Rawmill was offsna $Od iu

m 1:1/caroonate lnjectJo•, was 01)

from several opera**tin~** conditions showed NOx reduc

tion was lower by 20% at NSR 1 .5 when oxygen increased from 2% to 2.6%

. Even at this reduced effi

ciency, the reduction was still high: -50% at NSR 1

. NOxOUT-A injection through three different eleva· tions in the calciner showed similar reductions, indicating that process requirements are satisfied as long as the**rea~ent** is injected in the calciner. Baseline NOx varied from 350 pph for conditio n 5 to 550 pph for condition 4. Thls variation in the baseline had negligible impact on NOx reduction which remained at -60% at NSR 1. The NOxOUT Process , like any other chemical reaction, re q uires good mixing between the reagent and NOx and appropriate temperature and residence time. In this kiln/calciner application, the reagent was well mixed with the flue gas due to highly turbulent flows in the calciner and cyclone preheater and an appropriate placement and use ofNFT injectors. Gas temperature of about 1530°F is at the lower end of the process temperature window. However, high CO concentration from coal or gas oxidation inside the c:alciner shifted the required process temperature to a lower temperature. 6 The cal ciner temperatures, therefore , became more optimum as the result of elevated CO concentration. The available reaction time at this temperature exceeded 1 second in the calciner and another 

### 1-2 seconds in cyclone #5. This reaction time of 2-3 seconds is higher than reaction times of 0

.5 to 1 second in other applications

. As the available reaction time increases, the r e quired temperature shifts to a lower temperature and NOx reduction efficiency increases

. 6 Th is combination of long residence time, good mixing, and an appropri· ate reaction temperature ( a result of elevated CO and long residence time ) gave excellent process performance. A typical heat input to the calciner was about 5% of the total heat input to the kilnlcal c iner . Increasing this heat input had a negligible effect on NOx reduction when gas was injected into the calciner

. Chang· ing the calciner fuel from gas to coal or decreasing the coal**f~edrate** d e creased the reductions. This decrease was likely caused by an incr ease in oxygen concentration that accompanied coal injection. When coal is injected into the calciner, air carries pulverized coal from 

### a mill to the calciner. This a dditional air increased preheater oxygen from 2 to 2.5% for gas to 2.4 to 3

. 3% for coal. High oxygen preheater condi

tion with 

### gas as 

### the calciner fuel was virtually the same as the coal fired cases with high 

### 0 2 . S imilarly, impr ovem ent in reduction with increasi ng coal feedrate i s because of redu ced preheater oxygen. As indicated in Table 1 , oxygen was the highest at 2

. 8

- 3.3% under 5% coal and 2

. 6

- 2

. 7% with 9% coal feedrate

. 

### BY

-PROD UCT EMISSIONS SNCR processes can release unreacted ammonia, known as " ammonia slip " , and increase CO above baseline levels. A part of the NOxOUT P ro cess technology is a method and know

-h ow to minimize byproduct emissions. During this test, NOxOUT · A injection increased concentratio ns of 

## co and 

## so2 in stack gas. This increase was related t o oxygen concentration at the pre heater exit and can be minimized by injecting through the bottom ports, oper ating the calciner at oxygen greater than 2

. 3% , or by limiting the NOxOUT-A flowrate io less than NS R of 0. 7. 

# co The CO emi ssions exiting the preheater were h igh er than from the kiln. At the kiln exit, CO was typically less than 0

. 02 % while the preheater exit gas contained between 0.08 and 0

. 1%

. This CO increase inpreheater is the res u lt of gas or coal firin g in the calciner in addition to oxidation of organ ics in the raw mix

. The temperature in the calciner is 1500 to 1550<>F and oxygen con centration is typically l ess than 1%. Such condition delays combustion of gas or c oal resulting in an elevated CO emission

. In Figure 6, CO at the stack corrected to 10% oxygen is plotted against preheater exit oxygen concentra· tion for sev eral chemical injection rates (NSR) and without in jection. The best fit curves through each set ofdata are a l so presented in the figure

. The stack CO emi ssion incre as e d with decreasing pr eheater exit oxygen and with increasing NSR. This CO increase was negligible at preheater oxygen concen· tration greater than 2.4 % and at NSR less than 0.7. When the reagent was injected through t h e bottom• 09 : 21 : 9 5 13 : 2 !3 '5'1 7 08 983 32.!0**1~0r---------------------------------~** 0 ):1 1400 Q £ 1 20 0 

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. . -->-- - - • Figure G -Effect of**NO~OU'I!A** injection on. atack 

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...... .. ... .o .. ........ • ... Figure 7 -Effect of prehea.ter orygen on atack SO1 ports, CO was about the same as the baseline levels atNSR L The NOxOUT chemistry requires oxygen and appropriate temperature to react with NOx. At low 0= or at low temperatures, CO generated from the urea decomposition**oxi~es** to C0 2 at a slower rate. In addition, combustion of gas, coal , or CO is delayed with a reduced 0 2 concentration caused by the NOxOUT reactions that consume**0~.** Both of these paths are likely to have contributed to -the CO increase with NOxOUT injection at 0 2 less than 2.3%. A$ in· jection location moved to a higher temperature region (the bottom level), the rate of CO oxidation increased, which gave lower CO than the middle or top ports. Therefore, the NOxOUT-A injection into high temperature zones and/or increased oxygen can prevent a CO increase above a baseline level.


### S0 2 Emissions ofS02 increased with decreasing preheater exit oxygen concentration

. Concentration of**SO~** 

### \:\.LC O FrEL TEC H**~009 01-t** 

corrected to 10% 0 2 was about 20 ppm at >2.4% 0 2 , but increased to 36 ppm at lower 0 2 • This increase is likely to be the result of very low oxygen and high CO concentrations which decrease the rate of sulfur capture by lime. In high temperature applications described in literature, the rate ofsulfur capture with lime or limestone decreased as excess oxygen decreased close to stoichiometric condition. 7 NOxOUT injection increased S0 2 with increasing NSR and decreasing 0 2 • In Figure 7, 80 2 during in· jection was higher than baseline conditions but only at less than 2.3% oxygen . This oxygen level is also the level where CO started to increase

. The SO. increase was the least when the reagent was injected through the bottom level ports
. This correspondence between 

## so2 and 

## co supports the role of high 

## co and low 0 2 concentrations in reducing the**SO~** capture efficiency.

### ~ Flue gas was analyzed for ammonia at the preheater exit. Many samples were obtained and analyzed during injection and baseline condition. The results, however, were erratic, ranging from 5 ppm to 20 ppm during injection and between 2 and 9 ppm with an average of6.5 ppm during baseline conditions. At NSR of 1, average of 7 data points were 10.4 ppm of ammonia

. Further ammonia sampling and analysis is needed to validate these results.



### ECONOMIC ANALYSIS The cost to maintain NOx emissions to less than the limit of422lblhr will depend on the firing rate in the kiln to process a raw material mix to manufacture a certain type of clinker. Raw material variations and the product requirements change the firing rate which in 

### tum affects the NOx levels such that the required NOxOUT

-A feedrate will change constantly. In Figure 8, the average daily NOx emissions in pounds per hour for June, 1993 , varit:!d from 300 pph to 700 pph

. Using this as a basis, the reagent cost for a ton of clinker was estimated as shown in Figure 9. This cost varied even more and ranged from no chemical feed to $0

. 50 /ton of clinker. An average chemical cost for June, 1993 would have been $0.18 per ton of clinker

. In addition to high chen1ical utilization, the NOxOUT Process is cost-effective because the chemical is injected only when necessary and the bulk of the operating cost is the chemical. The capital cost of the process for this cement 

### kiln! calciner was estimated to be SO

. OS per ton of clinker on a 15

-ye ar life , 85 % average plant capacity of••• .**-.0~9 ·** **2~1~ ·** **9~5-~~~1~3i i2il9••'a'iilill-il** **,** t il )o

- 9 i1

S il.

)

- 3 111i!.!

. -!ill(•

l

____**..,..:\.._A~ _**  . . C_l_P:EL TE C H**800,-------- ------------------------~** 

&0 NO,**11111** •**42~** POll

1 3 ! 7 9 ', 1 13**~** 5 17 ,**~** 21 23 25 27 29 OSy! (JUr\6, 1993) Figure 8 -AJJerage daily NO:r emissions

100 tonlhr normal output. The capital cost incbdes equipment, engineering , installation (estimate ) , license fee , service cont.ract, start-up, optimization and training

. 

### CONCLUSIONS A short-term testing of the NOxOUT Process on a cement kiln/calciner has demonstrated that the process is highly effective and efficient. At NSR of 1.5, NOx reduction was as high as 80% and chemical utilizations were typically higher than 50%

. High degree ofmixing and a long residence time at appropriate temperature contributed to the excellent process performance. The current limit of 422 pounds per hour was maintained under various kiln /calciner operating conditions with less than 40 gph of NOxOUT-A or NSR of less thar. 0.5. As for byproducts, SO. and CO were unchanged from baseline levels at NSRless tho.n 0. 7. At higher flowrates , these emissions also !"emained near baseline levels when preheater oxygen concentration was greater than 2.3%. However, both**SO~** and CO increased slightly wit.h increasing chem.ical injection rate at low er oxy gen. Ammoni a measurement at the exit uf the preheater was erratic but range d about 6 ppm under**basel~-:le** condition and 10 ppm during chemical injection at NSR of 1. The NOxOUT Process was easily installed, tested , and removed

. using existinr, ports and available resources without 

### e plant outage
. The plant operation was unaffected during the NOxODT testing. A commercial system should also be easily s.de.pted t.o plant operations and easily maintained.

. An economic analysis using June , 1993 as an example showed that the average operating cost would be $0.18 per ton of clinker to meet the current limit of 1 3 5 7 9 11 1 3 15 17 19**~** 23 2$ Oay6 (June.**~ 0~3)**  Figure 9 -Rea gent C011f in $ / ton of clinker

422 pph. \Vith the capital cost of $0 .0 8 per ton, the NOxOUT Proces$ is a cost-e ffective and flexible system to meet the current NOx requirement as well as any futl;.!'e lower limits. 

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.E

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