EMISSIONS CONTROL 

# t-**~--**

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# ISNCR emissioncontrol

f:- 

## by Joe Horton, Suwannee American Cement/Votorantim Cimentos North America, 

## AI Linero, Florida Department of Environmental Protection, 

## & 

## F MacGregor Miller, Cement Etc, Inc 

# P limc,ry f'-lOx control measures alone 

### do not**alw~1.ys** achiev-e 

### the most stringent regulatory**targ~ts** 

### for abatement or exacerbate process problems 

### from s:ulphur 

### cycles. So,**end-of-pip~** au-gmentation is needed. Providing .good 

### accounts and 

### reviews of using cornbined
measures is important The lndust1y has
concerns regarding ammonia slippage a_nd consequent emission. Operators also


### a.wait contirmation of the extenttb 

### wh1ch .successf-ul industrial demonstrc_tions 

### can imrried1atety be repliCated elsewhere. We need certainty of simu!taneous!y achieving 

### NOx r·eductions, 

### vvhiie avoiding excessive CO or 502 emiss1ons and/or undue 

### process**p~oblems.**



### SCR has potentral expense-and technH:al difficulties associated vvith 

### catalystfouling _and replacement, and scrubbing methods have no lo-ng-term conclusive demonstrations. Hence. SNCR fs tavouredlil, Ammonia, urea,
or other nitrogen compounds (such ascyanuric 

### acid, PJ'ridine, and 

### ammonium acetate) are inje<:t.ed to the kiln system 

### Use ofSNCR to control emissions ofoxide-s ofnitrogen from cement plants: this was the topic ofthe first prize winning paper at this year's IEEE Conference. ICR is delighted to offer the following extracts from this work, augmented by material from another recent 5tudy

- from which more is to appear m a future article that concentrates on allematives to the SNCR method, now described in some detaJ/ below.



# 1

# Various techniques to avoid or abate NOx

# emission~ Pnmary measurf!s

• Fl<itne cooling (for example. waler addition)

•**LOV·.i-NO~** burners (vvhlch arc not always successful)**~** Staged combustion in secondaryJprecalciner firing systems. or mid-kiln firing in long 

### kilns

•**,1\~ineralised** clinker production


### Secondary 'end-of-pipe' measures
• Selective C:otalytiC..Reduction, or 'SCR' (involving an1mcnia and a bas·e-rnctal catalys-t 

### .at em cppropria.te**temp~raturc,** lo 

### read 

### and form water 

### arid gaseous**ni~rogen)** 

### • Gas sGubbing with an oxidi:.ing additive such as ozone or hydrogen peroxide

• Selective Non-Catalytic RcducltDn, 

### or 'SNCR' (injectipn of ammonra or its -::ompounds to preheaters -Of perhaps at rnfd-kiJn, at c,ppropriate COnditions 

# or temperature, e-tc).



### Sorne ca..n be applied s.imnltancously_

;:;t <1ppropriate tempernture -and oxygen concentrations- (and potentially also CO concentrnticms). The selection of reagents 

### is proces-s and telllperature spedfjc: at h1gher temper-atures, ·urea decornposes to produce·amrnonia, which reduces NOx. For reason-s of 

### test safety, simplicity and 

### by-product formatiOn. ammonia 

### and


### F1gure2: ammoniaand urea-dissociationand reduction pathways urea have b-een pr·eterred_ {9) Ammonia has typically_**p~rfQrmed** best in -early kiln applications. in Europe (see box ·story). Cy:;inuric
+OH +NO Add ...:----:....: HNCO

## ~ ! "- NCO

_,_

__ _,.,' HNCO

### "~

# NH,~O, +OH

# o~-NO**NH:~:** N_z

## ~0 •Ny"P'**Ammoni::~ ',-----~**  NH-a --...._ _ /

.,._ NNH/

Oc'(;omp<.:>sition !'r.oc-es_.;**~•-l'.H't~** t-', if<•!"lf'l••, i"tn!>•,;rm;. hWF/i."i/ R<;<;'..lF(fJ l,<JJiOri!(Ot)'**CJ~pa'I,"t'-~fit** -:Jf**M<;:h~>:Jc~l** i.'f'f.'ntci"PG_?, To!'?(;<; c\&Ai U11NNS!:',I 

## Theory of reduction In SNCR f.!l, 

### NO reacts with ammonia: (1) 2NH3 + 2NO 

### +% 0 2 _____,.. 2N 2 

### + 3H 2 0 

### lt urea is used. the reaction is: (2) CO(NH2)2 +2ND + y, 02 -· 2 N2 

### + C02 + 2H20

B-oth react'rons ·form innocuous nilrogen. acco1npanied 

### by water. The reagents are most conveni-ently Introduced**a~** 

### a water solution. 

## Reagents used SNCR with .ammonia and urea. may l?.ke .several paths.EMISSIONS CONTROL


# European experience

SNCR 

## was demonstrated in a preheater kHn with both ammonia and urea_ These


### were injected to the gas riser duct as shown in the Rgure, with a molar ratio of 

### reagent to N02 of 1:1 (7). About 

### 70 per 

### centreduction in emissions was observed with ammonia 

### and about 35 per cent with SNCR is used in 18 European suspension preheater or precalciner kilns, tvvo Swedish,
one Swiss and the rest German. l41The· mpst common reagent is 25 per cent ammonia 

### water.£5.61 NOx reduction 

### rates vary from 

### 10 per 

### cent to 

### 50 per 

### cent with
an NH3:N02 molar ratio of 0.5-0.9, NOx emissions are 

### then 2.4-3.8\b/t 

### of clinker.

urea. There was no major increase in ammonia emissions and 

### greater NOx reductions were obserted with excess reagent, 

### although there was· then increasing ammonia slip. Two dry-process cyclone preheater/ precaldner kilns in Sweden achieve 80 per cent to 85 per cent reductl.on (emission at 11b/t of clinker) at an NH3:N02 molar ratio 

### of 1-1.1. {5,6] One reason 

### for this remarkable result is


### Early 

### application of SNCR 

### at Hokirn Albert Scheuer of the VDZ reported on 148 SNCR trials 

### involving five different kiln**systems~** 

### three with cyclone 

### preheaters and two with grates

..A 25 per cent molar concentration of NH3 in water was the main reagent, with
some additional**te~ts** using ammonium sulphate and urea. NOx reductions with ammonia solution ranged 

### from 15 per"C:erit to 75 per c:ent, with reagent effectiveness strongly influenced 

### by temperature. Maximum NOx reduction occurred 

## at 980"( (1795"F)'. 

### NH3 escape occurred below 

### 900"C {165(YF) and when NOx concentration fluctuated. NH3 utilisation decreased·significantly with 

### increasing NH3:NO molar ratio and with decreasing NOx concentration, suggesting that SNCR 

### offers les.s promise at low NOx emissions levels. [2,3) 

### the use of multiple injection points 

### (12 in al!) 

### that ensure 

### a long enough retention time for the reaction to take 

### place. The optimum 

### temperature is said to 

### be 900-1100'C 

### (1650-2Q1o·F). Results sUg-gestthat some .tests may have been carried out at below-optimum**tempe~atures.**
FLSmidth tested SNCR on 

### a 

### preheaterJprecaldner kilnm, injecting ammonia to the lower preheater cyclone, with favourable temperatures. Emissions reductions 

### averaged 40 per cent, but 

### reductions above 

### 90 per cent were obtained when 

### the Injection 

### rate was 10-20 

### per cent above stoichiometric.
Operating experience has identified some concerns with 

### build-up of ammonium btsulphite or bisulphate scale, which is significant for·sulphur-containing fuels.

The reactions are the same as those for SCR, butthe temperature window is critiCal without a catalyst. If the temperature is too low, unreacted reagent will remain, referred to as 'slip'. Alternatively, 

### ifthe temperature is too high, some or all of the 

### nitrogen present in the 

### reagent 

## may be oXidised to NOx. The traditional optimum temperature range 

## to avoid either of these undesirable 

### outcomes for ammonia 

### Is about 1600- 205"0"F (870-1 t20'C): 

### however several factors 

## may shift this window. 

### For urea the temperature range is slightly higher, with optimal efficiency theoretically around 1000'C. 

### Tests in other industries show that the lowest effective temperature range falls to about**700~C** (1300"F) when 

### hydrogen is cidded simultaneousJylBJ in 

### 'enhanced SNCR', although high sulphur levels may interfere.

In preheater/calciner kiln systems, the 

### relevant temperatures occur at the upper 

### end ofthe rotating kiln, in 

### the gas riser duct and in 

### the lowest preheater cyclones. The effiCiency of reduction depends upon temperature, concentrations of oxygen and carbon monoxide and residence time. as well as upon ammonia and NOx concentrations. This contra?ts with SCR, where a dedicated reactor 

### proVides controlled temperature and residence time, aimlng to avoid ammonia slip a,nd optimise reagent 

### consumption, Concepts for applying SNCR in long kilns are being considered 

### {see box out 

### below).

With urea, the same temperature**.~'profile** problems exist 

### as for ammonia, along 

## wtth 

## a couple of new ones)11l Urea decomposes under the proper conditions to give carbon 

### dioxide, as in Equation 

### 2. If oxygen 

### is deficient, carbon

## monoxi~e.**m-;yTo~·~-;:~.~~~~~Th~-~-;;:1··-** 

# roTes -of carbon monoxide 

### are discussed later: suffice_

## it tQ say .that it can hinder t/ie

## N6~**~~ductig_~_~.a~.~f!..J_n sO~e** **crrCuhlStances~-a-~.? -·~-~~!]!p~er.**  

# A"ddTtlonally, during dissociation of urea to

### -NH2··

# tne

urea 

### competes for 

### the OH radicals needed 

### for NO, reduction as 

### well .as for'the burr-lout of CO. These two competing reactions lead to more unreacted CO. Jn theory 

### thFrprOhleffi 

### Should"be**eq~·~i·ly·**

In a long kiln, the appropriate temperature window occurs at mid-kiln and continuous injection of reage.Jits has not yet been achieved. Mid-kiln fir'ing technology might 

### be applied, though solid ammonium or urea salts cannot be used directly because of rapid decomposition. Injection inside used vehicle tyres has been proposed, but not yet evaluated. Fue! Tech lnc is currently evaluating dry dust
or pellet injectfon methods.f9l



### With mixing air fans to enhance gas turbulence in the system, improved mixing of

## gases containing NOx 

### and ammonia may also otfer possibilities. Chain gas temperatures are generally in the range**1500-1600~F (815-870~C)**  and mid-kiln injection systems are usually down-kiln somewhat, at higher temperatures. There is a good poss.fbility that the correct temperature range can be achieved if mixing is enhanced and volatilisation or decomposition is suitably delayed. In addition, reagents could 

### arrive via. traditional dust return scoops. !twill clearly be necessary to mix NOx with the reagent before this decomposes.

### }:,gure3;**fet~ttveefl=et:liveness**

### ofammOnia and
urea tn reducing NOx in

## cement kilns



### 100 

# ' E 

## I

1.**Ammoni~** 

# ,.- -

# - 'I 

# I**~** 

### 80**~** 0 u 

# e 

# v**~"'** / I 

# 1 5 60 z I 

# /\

J r 

### - 900"( (1650"F), whereas


### urea 

### achieves almost no reduction.

Some 

### proprietary SNCR variants 

### for de

### NOx will be outlined 

### further in 

### a coming 

### ltR 

### article 'B.iOso!Jds 

### lrriedion Technology (BSJ) and Aqueous Urea 

### Technology (Noxoui't').' 40

850 900 950 1000 1050 1100 Temperature ln "C

vexing for 

### ammonia, but

### appears much


### more prevalent for 

### urea.**~dditionally,** 

### the presence 

### of the localise:d_ 

### CO -genercit\onfr'Om urea**dissoci~tion** 

### may further retard 

### the consumption of NH2

### intermediates in 

### the reaction, 

### giving loy.;_e_re_tfideflcy**~_i_tJ:l** 

### insufficient**oxygen,_?.='_:!tel~iiJlY_~~-~-~~~'l** 

## lhe

___**~jln-cafclner** 

### region. Also, 

## a by-product o·f the

### u·;-ea-reaci10f1~n particular, 

### is nitrous oxide 

### (N 2

### 0). 

### a serious 

### greenhouse gas, 

### Y.Jith effects 

### mNe than 300 times as strong as carbon dioxide.

The 

### advantages of urea are primarily in 

### handling and safety. It has a much lower

### vapour pressure than ammonia, and can 

### be easily 

### handled with 

### fevver
concerns 

### for leaks or spills. 

### However,


### as discussed.**~~~_o_nia** 

### appears to 

### be
a much more effective 

### reagent for 

### use in SNCR, especially 

### considering the 

### 'tn-)nimal

### oxyg~n-content and 

### temperature 

### windows_ in kiln-calciner regions. 

### As !Hustrated ln Figure 3, 

### urea is also 

### slightly 

### less efficient 

### than ammonia, even at its optimum temperature.l4· '10) Ammonia 

### appears to have 

### a maximum

### efficlei1C)f at about 950'C (1740'F), where 

### about 9o 

### per

# ce;;rQf-H1e··No; may be reacted for optimum 

### oxygen and 

### carbon monoxide concentrations. Urea, on the 

### other hand, has a maximum 

### efficiency of 

### ahout 80 

### per cent 

### at**990"~**

### __(1815GF). 

### Ammonia carl achieve almost 70 per 

### cent efficiency at 

## Results of fuli scale cement 

## plant 51\lCR tests The following discussion 

### outlines results of SNCR 

### testlng carried out 

### at five cement plants. At one plant (Pianl D). thls included both urea and ammonia injection. DLJe 

### to the temperature dependenc€"shown

### in Figure 

### 3, Plants A, 0, and E were tested 

### entirely with 

### ammonia or a Combination of both. Plants B and C tested 

### with urea for the reasons noted (safety and ease of handling).**Ba~ed** 

### on the res-ults and 

### condus-tons from the 

### tests, Plant A installed a 

### permanent SNCR system in March 

### 2005 -and has been 

### operating to 

### date with ammonia only. 

## Burnability effects The overall level of NOx 

### from 

### the burning 

### zone will be a function of

### clinker composition· 

### and kiln feed 

### fineness, particularly 

### the quartz and calcite fractions, 

### all other

### things -being 

### equaL Table 

### 1 shows the 

### relative contrfbutions 

### offeed 

### chemistry to kiln NOx; no data 

### is currently available on the
coarse quartz 

### and caldte 

### contributions. As. 

### judged 

### by LSF and slli<;:a ratio, 

### Plant B is 

### by 

### farthe hardest-to-burn mix**here~** 

### reflected in a high level of lbs 

### NO)t clinker. EMISSIONS CONTROL



### Plant A A four-stage preca!ciner facility 

### with no bypass and maximum clinker production 

### level around 

### 120stph. There ls a separate line calciner 

### and tertiary air can 

### be introduced at 

### three locations to -estabfish 

### and (Ontrol staged combustion. 

### Tertiary 

### air can be introduced 

### either to the 

### calciner for 

### combustion, the calciner 

### burner as primary air 

### for Tuel, or further along ·,n the 

### process 

### in the caklner ducting for 

### burnout 

### of CO 

### following 

### the re-ducing zone 

### of staged combustion.



### Thls plant 

### a:lso beneflt-s from 

### a low feed alkali and sulphur 

### content, 

### assisting culciner 

### operation under reducin_g conditions; 

### despite this, it 

### is preferable 

### to operate 

### with oxidising-conditions 

### to avoid build-ups, 

### with attendant increases in prehea.ter pressure drop 

### and output limitation 

### due to ID 

### fan lirhitations. The plant 

### therefore performed -5NCR 

### testing without maxfmising its low-NO)( calciner 

### capability. P!ant A \.vas 

### tested with 

### ammonia, injected after

### the calciner 

### hopper, but before 

### the bottom 

### stage cycione 

### (see Figure 4). This location


### was then fitted with a permanent SNCR 

### system with 

### four nozzles 

### at 90' intervals



### Figt,Jre4: SNCR

### injectionlocation atPlantA
transecting the ducting. The retentiOn 

### time from the 

### cakiner to 

### this location is 

### in ihe 

### order of nearly 

### three 

### seconds, giving 

### sufficient time for the burnout of ca!clner 

### coal.

Here, 'theoretical 

### NOx reduction' 

### is the number of lbs/h reduction of NOEMISSIONS CONTROL

PlantANO • Red.lction 

# I

p

........**~~-""'**

.............**1~~-**

-·...**---~**..rooi!nol

.........**~Figure 5~** 

### SNCR results at PlantA 

### [expressed as N02 ] at 100 

### per cent efficiency, and the ratio of actual reduction 

### to NSR 

### is the efficiency ofthe SNCR process. Thus, 100 per cent efficiency implies complete reaction of ·eve'ry mole of NO with 

### One mole of NH3-, and -an NSR of


### one would result in complete removal 

### cif all NO;.; present at the injection location. ln practice 

### it is usua.lly very difficult to 

### achieve near theoretical reductions, but Plant A did achieve very ·high efficiencies of ammonia utilisation. Figure 5 Shows the res-ults, ·including with the maximum theoretical redUction, 

### a;; well as results 

### obtained from an equipment supplier during tests on 

### a kiln system 

### ofsimilar s!ze 

### and designL10J.

Comparison of the reduction levels to theoretical limits 

### and to results 

### from previously testing, show this 

### to be a highly 

### successful installation. The mechanisms responsible for this success are discussed later.

One other outcome was the formation of an ammonia cyc\e within the roller mill system. Plant A does not monitor 

## "'·•·"'
-··



# "" Q**~""-"~Jl..,..,.i»)<l** ..<O,l



## ___**,._.~**

## ..**-~**

## ..**'"""'t~""**

ammonia continuously, but 

### a Fourier Transform Infrared Analysis 

### (FTIR) 

### gas analyser unit was placed 

### on the stack 

### to observe 

### NH3 emiSsions for 

### part ·of 

### the 

### test pe-riod. The raw mill was stopped ffllce while monitoring, and ammonia was detected at the stack during each of these
occurrences. 

### Data are shown in Figure 6:



### At the first 

### raw mill stop, no ammonia
was injected. 

### On the second instance, 

### injection vvas occurring 

### -..vhen the raw mill iriitlally went down but was stopped part way through 

### the outage. 

### The injection rate did not 

### appear to be correlated with 

### the stack ammonia level, which in both


### cases peaked at about 50ppm (v/v),

The ammonia s-eemed 

### to be caught 

### in an internal 

### cycle in the kiln/raw mill system. 'vVhen the raw mill**v~as** removed from the process during outages, the scrubbing offered 

### by the raw meal was eliminated and ammonia escaped through the 

### stack Several kiln feed 

### samples from various test periods were sent for evaluation of ammonia concentration, to determine the possible enrichment of feed with ammonia. Results, when above the detection limit; s-how an increase ln ammonia concentration over baseiine 

### conditions_. However, 

### due to 

### the relatively low

### -ammonia concentrations and the hlgh detection limitforthe method, .definitive conclusions were nOt**poSsible~** An 

### ammonia cyde was present. in part due tothe highly soluble nature of ammonia. Unrea-cted ammonia condenses on to 

### moist partidP..s in the 

### raw 

### mill (17 per 

### cent moisture in mill feed). 

### As the volatile 

### ammonia encounters 

### higher temperatures within the mill and/or preheater, 

### it evaporates.back 

### int6 the 

### gas stream 

### to 

### repeat the 

### process-. This .cycle continues until the raw 

### mill is stopped, removing 

### the scrubbing effect, 

### whereupon the ammonia escapes· out the stack.


## Plant B Afour-.Stage**pretalcin~r.** with maximum 

### produdiph 

### level of approximately 

### 19otph 

### of clinker; 

### with tertia'Y air 

### recovi:?ry.·from 

### the cooler 

### for use 

### in ca!ciner combustion and 

### an alkali bypass used for·sulphur 

### and alkalis present in raw materials 

### and kiln 

## fuel. During testing, the plant operated at**aroL:~nd** 

### 180tph. of clinker, with approximately 5-10 

### per cent-of main stack floV\1 bypassed 

### through a separate stack. 

### After the**bypas~** takeoff, kiln 

### exit gas travels throUgh a riser 

### dud before 

### tertiary air 

### is introduced at one location only, and during testing 

### the duct was· fixed at 100 per cent open. Following 

### the tertiary air arrival, the kiln riser 

### abruptly stops 

### and is diverted tangentially into the calciner, with 

### four fuel 

### firin-g locations, 

### Following the caldner, exhitUst 

### gases arrive imniediately at the lowest cydone. Retention time from calciner to cyclone is in 

### the order of 0.'2 

### seconds to 

### 0.8 seconds- at the 

## most.

SNCR 

### testing was carried·out wlth urea reagent. injected at four locations. 

### 1. 

### Ri.ser duct, a-fter the alkali byp_ass takeoff, but befO're the tertiary air duct 

### (two nozzleS) 

### 2.·Gas exit of the lowest stage cyclone (two nozzles) 

### 3. The· same location 

### as (1), but with 

### fournozzles 4. In the riser duct, after the tertiary air duct, but before the· caldner.

Figure 

### 7 shows 

### the system layout. The average results 'for the four locations and


### a graph of the results are given in Table 3 and Figure 8.

The results arc similar to reduction 

### levels

### EMISSIONS CONTROL



# i

... 

# !**~ jf,:~:\R:I,<::;**  ! ] ,,. :i 

# "

.**f;,;;~":'lJ!t t!~Ji~~lJ'** 

achieved in tests 

### by an equipment supplier
on a similar sized calciner (5000tpd)l"l0l. 

### The Ideal location was in .the lower portion of the riser duct prior to· tertiary air introduction, due to several factors.



### The**sele~.:tion** 

### of urea reagent forced higher temperature profiles for increased reduction efficiency. Location 2, the 

### gas exit after the lowest cyclone, ha.d conditions very similarto those used at Plant 

### A: temperature around**1550~F.** 

### sufficient oxygen (1-2**p~::r** 

### cent). CO 

### at 1-000-2000ppm, and sufficient r·etention time for the reaction. However, with urea 

### the reaction did not achieve comparable 

### efficiency, As previously discussed, the dissociation and reaction of urea is-improved by 

### a higher 

### temperature 

### profile**w~th** sufficient 

### oxygen present 

### and perhap-s. !onger retention tfme. ln 

### Plant B, the temperature was the 

### most significant factor-affecting. effidency. This 

### led to 

### the highest temperature injection 

### location (riser duct location 

### prior to the 

### introduction of tlie 'colder' tertiary air) being the 

### most partly due to mixing occurring 

### as a 

### result of waH effects_ 

### However, with the 

### noztles -selected 

### and tested, 

### little difference was noted 

### between the use of

### one, two, three,


### or 

### tour nozzles 

### at the same flow rates, 

### caJiing into question 

### the hypothesis 

### of a lack of mixing between reagent and-gas**-stream~** Fluid 

### -dynaf!:ll£_mliing.:etft:.<ttS may 

### be more

## ette&·~lth ammonia

## re~ient

one**Other-n~bk diffe~~~;·"-**  between 

### results 

### at P_lants A.and _B was the 

### observed 

### increase in 

### CO from Plant 8, especially with_.reagent 

### inj€(tian·at**~ocations** 

### with**!~wver** oxygen content. As

### [x~viously 

### discussed, urea 

### can create CO in its dissociation 

### into NH 3 , 

### but 

### may also interfer€ 

### with the OH radical and retard 

### burnout of CO to C02 more rapidly than ammonia. Perhaps the creation of NH3 from urea results in dissociation of urea and creates denser localised 

### areas of CO, which can 

### interfere \.vith the oxygenenhanced 

### NH2

### /NO interaction.



### Amrnonia s.!ip was not monitored at Plant 

### B, but a pronounced t:letached 

### plume was noted dudng testing, 

### despite low 

### levels of 502 

### in the stack. 

### This, coupled V'Jith the overall low level of 

### efficiency for NOx removal. 

### suggests that Plant B would achieve only limited NOx reduction 

### with lhe SNCR system as tested; -however some improvements learned

### ~f~~IT!Other tests 

# may be. possible.

·Ther-f-is 

### a.ri.Jriteresting explarlation fOr 

### the 

### relatively inefficient**NO~** 

### removal from Plant B (and Plant C) 

### relative to 

### the other plants. Plants 

### Band Care caldner kilns, where 

### the rtser 

### duct is the 

### most efficient 

### location for 

### injection. This**V<~o.uld** 

### be expected to 

### deal efficiently with NOx from the burning ;::one, but


### Ftgure7: 

### Plant Bca:Jcfnerconfiguration 

### effident location, still resulting 

### in much lower efficiency than 

### in Plant A. 

### j Kiln B:lt Gas K'!n Ff'e-d



### Additionally, Plant B's caldner


### cross section is much larger than at Plant A. 

### As noted 

### from Rose, Alder and Erpeldingf10]


### a measurable reduction in SNCR efficiency is observed as the cross sectional size of the injection location increase-s. This is partially attributed to a 

### reduction in mixing capabilities at the injection location from 

### both the reagent and 

### the NOx ln the gas 

### stream. It may also be ' 

## ' 

# r--Q y------l



# .**o"~----n** lnjer:1ion •"'I

# -¥ Localion**•+-·······~1** hljeclion

### ~------1 Ter!iaryAir 

# I
UJC.11ion '**'-~="---'--·-~--~---"' .---~~** **~-----11-\** ByPass 

### i 

# \T---.,.

### F1gure 8: SNCR Results- Plant B

P1a01tB NO • Redocloo

0,1l

- /tlrt<DI>co:;

...... l),

....__"'-"_1>_>!**o'"""''"'~-~"'"'--~~**

.. lllo

..IW<IPJI..-

..Il•""-...,,,.._,p,Duor

### car~-~~~!?_d!~~~!~~9X~~~~~!~tep 

## ln_th':

___ calciiler, as the injection pOilit 

### is up.Str_eam; No 

## direct measurements of NO,: and flow 

### combined were taken

__up.s-tream of

### the Injection site,

### ~ __no direct

### ·ll}~a?Yf~memtof the effic1ency

## Can be·off.ered fn

### t~rm.S:of 

### NSR. For comparison**purpos~S,** 

### the':NSR 

### listed a·ssumes 

### that a_ll**~Q~J~·-g~~-~~!~ ·-~-·1-**  

# .....-...**e.~**

........**,......~Jo.ot~..-.l-4--o<-•l'l'o**....ol**-n.-~-~-""'**



### the dlstiilct.advantages 

### asSociated wlth 

# mmg.-arnmonia:ra,th'e·r·fua]i -urea,

# as the

## apti'm~m tf!nlperature is: lower.


## Plant C ,A 

### two string 

### preheatertower with 

### {):ne string:·equlpped w·lth a calciner and the;othe.r Without. 

### The strings. 

### time, yielded 

## elevated 

# co levels post-ca!dner and through the lower 

### preheaterstage. In addition, residual 

### carbonaceous material in raw 

### meal is believed 

### to contribute to elevated CO levels throughout 

### preheater and calciner

SNCR testing was carried out lVith urea injection 

### to each string. Calciner injection 

### locations were: 1. 

### lower portion o-f the caldner 

### (two nozzles) 

### 2. up·per 

### portion of 

### lhe calciner 

### (two nozzles) 3. 

### gas exit ofthe lowest cyclone 

### after calciner (two 

### nozzles).

Preheater·string injection 

### locations vvere: 

### 1. lower 

### portlon of the 

### riser duct (two 

### noZzles) 2. 

### uper .portion of 

### the riser duct {two 

### nozzles).

A

### combination of locations was also tested -wlth the upper 

### portion of the preheater 

### s-tring riser and the 

### upper portion of 

### the calciner. Rgure 9 

### shows the 

### plant layout. The avera-ge 

### results for the locations and a graph of the results 

### are given 

### in Table 4 and Figure 10.

In -general Plant C 

### reduction efficiencies
were very low, with rnlnimal decrease In NOx emissions despite high NSR. As discussed, 

### the choice 

### of urea 

### as reagent probably 

### damaged efficiency of the

i

### rom the**burnintt~?-~e_,**

### _that ·hOne·Pfthis tak'ine.r**~rin-g-** 

### has mQc:h**latSE:dhf.o~:ghput,-** 

### re¢eiVirlg 

### appfoxirililtely**80~85** 

### per·Cerit figure 9: 

### Plant

### Cconfiguration 

### is reduced ir:i 

# the caltin"er, 

# .anathatthe## calci~~r**_g;_e_~~~!~s ~o**  fUrl:her NOx·:·b.f
course-"these**are~;:;Q(~~IT~f_"a5sU0-Ptions,---** 

# as·**the-5~1~0-~~r~9~rif0?,~!~0~~1~9~}br** 

## mosrfu:els,

__so_thai__the

## :?-N~_**-~ffld_er\:cy determir1~d** 

# atu:;;:**~~s-~-~~-;-pt~bab!i**

# .. a·rtificialiY 

# 10W,·**;1~d~** 

## th>e**j~age~t-did** ·n9t have

## ~he

# __**?er~f~:~f!Y:?JJb1":@~i9~----­ locatiqnJ9._r~_?.0:** **:~i_th _l)J_.9·~·-'geb~rated**  

## further_

__Qack in th_e_**~roGess"** 

## in -the_. ·ca!dner

.



## ..**~s;;ce th~-**  

### rise;**d~ct** 

## [;;c3.11Gl1-Wa5-

______ _c
- 

### optimum for thes-e kilns despite**Jh~-fa,t;t** 

### that 

### ca.lclner fuel NOx**vi.as·m~_t:;trea:te.d,** 

## 1 

# !_**~ppe_~~~-!b.§_t** 

## ___**R9_s!~~~~~~~t**_J

### .9_e~!:~n 

### wa?_§ijpo

__lo_w_

__**~--!~_n::p~e~':"!We, -.or_~Up~q·.**  

### high a 

### CO

.. level,**~obe·effedjve_v~tth**

## tb~.~Y-~~-~-r~~g;~t 'Again, ih-is;:sJlbwS**~f**

## the gas- ·and material ·flow. MaximU(Jl production level is ·?tpproXimateJy .215tph of- clinker. There ls_an 

## p.Jkilli bypass, used, 

### fOr

## sufphu'rar1d .alkalis

# presentin fuel and rav·{ materials. Tertiary 

## iidrbm the. 

## coOler i.S inthJ.duc'ed 

### pr!or'.to ±he caldiier in that strl.ng ofthe 

### tower. During

-**t~?ting,** 

### the plant operated at around 206tph of clinker. 

### The pettoke fuel 

### was·.u:se·d in both 

### main**·burn~r** 

### ahd 

### talcfner, and as 

# are:.ult

## bf !Pw volatile 

### content :iihd 

### limited C:ak:inet 

### retentiOnEMISSIONS CONTROL



### F1 ure 10: 

### SNCRresults Plant C
PlantC NO·• Redudlon



# ·-**~** 

# :I :I I I

'-

.... ,- 

# I

/



# ·- - "'""'"'" I**·~** I

# / 

# ..

= 

# I**·~e-;l~~-~----~-K'~-~-~--~~~~~~~r~-~-~~-·._:**

# __**--~-.L._** __________________________________ •

__

# ··_··----~

# ~,~~-----·--~·~:--~~----------------------------------------------------~ "' "' 

# ..• HO :l..r:<l**l.~** 

# ,

# .

calciner would have been greatly reduced 

## by the calciner with its inherent reducing
zone as operated durin·g tests. Since these principles ofstaged combustio·n are present in the calciner and quite effective 

### at Plant Cfor reducing r_eduction was more 

### effective in the upper portions. ·of the riser, which was_ unusual, 

### given the reagent. With 

### \)tea

### temperature was evidently th-e dorrilnant 

## factor controlling effiCiency, However, temperatures 

## in this riser duct

### .may- not- increase. in 

### the upper portions, 

### but it

### is 

### presumed 

## that CO 

### present atthe 

### ki!h irilet ft'orri uncombusted ·fuel 

### deCreases in the upper portion of 

### the- riser. This 

### may contribute to increased efficiency for the upper portfon 

### of the riser.


### Plant D A tvvo-strlng 

### preheater kiln without calciner, 

### maximum clinke:r production level 

### approximately 11 Otph. 

### Alkali bypass used 

### both for sulphur 

### and alkalis present in 

### the
raw materials and 'fueL 

### During testing; 

### the 

### plant operated 

### with an hourly 

### clinker production of around 105tph. The fuel used during testing was petcoke, SNCR testing was carried out with both u1·ea 

### and 

### ammonia. Jnjeclion locations were selected 

### in the upper and lower portions of the comnlon r!ser duct. (ln kilns without cakiners, the optimum temperature will 

### usually be found i-n 

### the riser 

### duct). 1. Lower portion of the 

### riser with urea 

### (four nozzles) 2. Upper portion of

## the riser with urea (three nozzles) 3. Upper portion of the 

## riser with ammonia 

### (three nozzles). NSR. As stated earlier, independent 

### measurements have shown that a great deal ofNOx here Is generated in the tower (fuel and feed NOx), subsequent to the injection site. As previously 

### discussed this makes 

### it very difficult to calculate the overall NSR and efficiency,


### :as injection locations prior to the calciner 

### do not reduce NOx generated within kfln NOx, the 

### effectiveness of the Low-NOx calciner should 

### be maximised, 

### Ftgure 11: 

### Plant D:eonfiguratfon



### the cakiner and the molar rate of NOx flow frorn the kiln is not easily known. ln PlantC, kiln and calciner operation do quite an effective job at reducing burning


### zone thenna!**NO~** 

### generation. so that lnjectJon zones prior to the calciner 

### have two d'1sadvantages. First they wll! have 

### only limited a111ounts of NO/( present to reduce: when compared to overall rates of NOx reduction, 

### it will appear to have 

### very limited efficiency, but in reality SNCR may be effectively reducing the limited NO;.; present atthe injec:tion location. Secondly, 

### NOx reduced 

### by SNCR priorto the 

### with subsequent SNCR reduction. The choke 

### and location of testing should mOst 

### likely 

### have focused
on post calciner injection. since there is a [ow NOx level in 

### ga5 enter'mg the 

### caloner and significant generation of NOx from 

### ceJciner fuel, Plant C's size may have contributed
some inefficiency, being the 

### lar_g·est tested.

In the preheater string, Kiln Feel:!

### Rgure 12: 

### SNCRresultsPlantD**-----~~"**

# ··r·------------------~·L·~-----c----------~,~-·~·~···~·~--~~---~-~·--··~ ..

# ~·---------..--:1 //'

## ,..,~ 

# -

# ~~~--~-~~1~-----~~------'-'-------------------------------cl ;; "

# ;~~**f---~-~~;'·-·--~">--~--------------------------------------------------il /·~**  

# • 

# •• I

.

... /



# ·---·--
F1gure 13:

### P!antDureaversus ammanra

/



# --.- 

# J i



# -**~** 

# -----**:~. --~_£~·~~--:~:~---~-·----------** 

/ 

## /**;?·:~/** 

# /'

# .•

____,

# __**·---~--** 

# ·-----

Figure 

### 't1 shows the plant 

### tafout: 

### Tabl'e- 5 and Figure 12 give the 

### -average**resul~** for 

### the locations.

Plant D experienced·the·iT)ost.effident reductions of any plantte$d

# With urea. 

### This planthas low riser ductCO and suffident temperature for the 

### highly temperature 

### sensitive urea reaction. 

### Also; no fuel is burned -subsequent to the**injectior:~** location, so no chance

### of additional fuf'i!**NO~:** 

### fe>:rmation exists. 

### Fe-ed NOx, ofcourse, could still form. This wasalso the only 

### plant tD 

### test both 

### with
urea and ammonia_ Results ln the same location 

### showed marked improvement 

### for ammonia, 

### with almost theoretical reductions in**NO~** result-ed. Rgure 

### 13 shows results of the
sc.me injection location with the same numberof nozzles for ureaversus ammonia.



### Results show the effioency 

### advantages of ammonia 

### over urea, 

### as \<\'ell as 

### the possible influence 

### of siz_e and wa.ll 

### effects that could 

### be present in 

### smaller crosssectlona! injection 

### locations.

PlantE A small preheat-er kiin with maximum dinker production of approximately 30tph. There is no alkali bypass despite- the fact that 100 

### per cent petcoke was 

### -ftred and there are high S03 concentrations in clinker 

### {2.52 per cent 

### 503). SNCR testing
was carried out with arnmonl.a at injection 

### locations throughout the riser duct. as follows: 1. lower portion 

### of the**ri~er** {t-.·.·o nozzles) 

### 2. lo-•.-;er portion otthe riser (one 

### nozzle) 3. middle portion of riser (two nozzles} 4_ middle portion of riser (one nozzle) 

### 5. 

### upper portion of the rlser (tv,ro 

### nozzles) 6. 

### upper portion o·f the riser ione nozzle).

Figure 

### 14 shoWs the plant layout. The average results tor the locations are given in Table 6 and Figure 15.

Plant 

### £. with low CO and high oxygen throughout the kiln inlet and riser duct, expenenced very 

### effJCtent**NO~** reduction. The lov..-er porUons ofthe 

### riser duct with higher temperature wer-e**Fi~re** 

### 14: PJantEconhgurabonEMISSIONS CONTROL

Figure 15; SNCR results Plant'E

PlantDNO' Rt)ducliOfl

### ·~-·~- ><**,~,..**......**,_~>'~"""'r'** 

### u.---"'O<iy**--~~** •**--·~=loo:J.C>nl:f** £ >Oll<o..R

.... :-•



# -**~-~-~·-"'~ ~** **<-;~>o**...**~-** 0**'---1~0.U,O**



### the 

### most efficlent reductiOn locations

.. CO and oxygen levels are fairly uniform throughoutthe riser so the higher 

### temperature provided higher reductions, but even at lowertemperatures exiting the riser duct, redUction efficiencies were 

### quite hJgh. As with Plant D the absence of


### a cakiner or 

## pbst kiln 

### burner**NO~** 

### source niakes evaluatiOn of NSR and SNCR efficiency accurate arid reliable.



### PlantD was also 

## by far the smallest kiln tested and exhibited very high efficiencies for NOx reduction. These results suggest 

### that, after all, there may be som:e vqlidity in considering the possibJ·e influence of mixing and wa\1 effects 

### on SNCR efficiency.


## Conclusions Reagent VVith regard 

### to reagent 

### selection, ammonia solutiOn 

### is seemingly always favoured ·In cement 

### manufacturing for reduction efficiencies. In research 

### by D. Kupper 

### and 

### l. Brentrupm, it was 

### noted 

### that ammonia 

### water was much more 

### -effective at reducing NOxemissions 

### than
urea solution. In particular, ammonia 

### has greater reaction 

### efficiency through the normaJ temperature 

### window 

### ptes_ent in the preheater or calciner. 

### Additionally the increase 

### of CO is 

### much 

### more prevalent with use of urea, 

### especially when 

### used in 

### injection locations vitth low oxygen or high CO. It 

### appears that dissociation 

### of
urea results 

### in additional 

### CO that then may compete for the 

### OH radical pool for the oxidat1on to C02. Figure 16 shows the 

### marked increase 

### in CO from injection 

### of urea 

### in Plant 

### B in 

### the high CO region after the c.alciner.

This localised 

### increase in 

### CO with 

### dissociation of urea to 

### NH3 may be one
reason 

### why urea achieves lower efficiency 

### in the tests. This increase in CO competes 

### for the limited 

### supply of OH radicalS, and 

### n-ot only for burnout of the CO; these
same radicals are 

### needed tor 

### the NH3- 

### to-NH20H intermediate, fundamental for reduction of NOx. In the low oxygen environment

### of**preheat~_rs** and caldners, there is limited oxygen ·present to g_enerate the·se 

### OH radicals. ThiS 

### was also noted 

### in research 

### by Steuchl11l, which showed increased stack

### :concentrations of CO; The CO**incr~ase** 

## was minimised 

### with oxygen concentrations greaterthan 

### 2.4 

### per cent 

### and at 

### NSR injection ratlo 

### of less 

### than 0,7, Additionally, urea indicated a 

### strong dependence 

### on temperatures in 

### the range of 

### 1600 to 

### 170trFfor 

### effective reduction. Ammonia 

### was shown to react with NOx with 

### high effidenQes 

### at temperatures 

### as low as 

### 1500'F, giving many more useful 

### potential injection lo_catioris 

### than urea.

Plant size versus reduction 

### Acorrelation between 

### plant 

### size and reduction 

### efficiency was· noted. This agreed with previous 

### findingsf10,12J 

### that larger 

### plants had lower 

### efficiencies than smaller.- 

### The fallowing figure shows 

### the best resUltS achiE-ved from all five 

### plants, and the· thre.e plants with 

### outputs from 600-300Dtpd 

### have much higher 

### efficiencies than 

### the two larger facilities. 

### Intuitively it

### seems to make ·sense 

### that large 

### gas flows with larger 

### cross sectional
areas would result 

### In 

### less miXing and direct c:o·ntact 

### between NH3 and NOw However, testing**condu~ed** 

### atseveral 

### ofthe· plants Shows 

### that the addition of more injector 

### nozzles in the 

### same location traversing 

### the ducting did not increase effidency. 

### Under the 

### first assumption the increase 

### in injection locations 

### with the same flow should have overcome the 

### presumed lack 

### o.f mixing

### and increased efficiency noted. Figvre 18 shows testing 

### conducted 

# at the
same 

### location with varying number 

### of nozzles for Plant 

### B.

No change 

### was noted with four 

### versus two 

### nozzles

.. Howevet', 

### the correlation between 

### size and reduction efficiency is evidentand 

### may instead rely on fluid dynamic mixing differences experienced 

### br on stratification present 

### as size increases. Additionally the influence of wall effects Which exert a slowing effect
on 

### the te'nninal velocity of particles, may increase the lam'1nar character of flow, and could impact the efficiency 

### of reactton 

### between the 

### reagent andEMISSIONS CONTROL



### F1gure 16:

### CO increase in Plant B

Figure 

### 17: 

### il!l plants**NO~~.** 

### reduction and plant size

figure 18: 

### Plant Bresults 

### with d1fferentnozzleconfigurations



## ::+1

____________________

# ~/'~~----c-·~-~·~-------------------------~

# ~:1**===,,;';:,;=-:;~~;,_,~-~:========~-~-"'**:

I ,v**"'~----J"~------~"o_**

# _________________________________________**.,~** 

# ••**~.""-**

# ·~+l

# ___**/7~1~-"~0~0~-~~~,~~~~---·-**__ -_-

__

-_-_-_-_._-_-_-_-_·_______________________c 

### r· 0 o



# .. ·-· 

# .. '" '" NOx present ln the gas stream. 

### Ctttaly.tlc 

### effects of Iron Compounds ha:ve also been- shown to aid NOx decomposition: 

### wall effects may enhance interaction between such potential catalysts and 

### gas stream components; this will 

### be discussed 

### subsequently_ Complex conceptual fluid dynamic modelling ofinjection locations would 

### be required to further examine the influEnce of Wall effects: and is bey_ond the 

### scope ofthis paper.
Sulphur cycle effects on 

### SNCR reaction The presence of sulphur and chlorine


### were "OTiginally 

### thoughtto be potentially troublesome to the SNCR reaction due to the propensity 

### of ammonia to interact 

### with sulphates 

### .and chlorides. However, the 

### stability of ammonium 

### salts was known to 

### be low 

### in the high temperature profile of the injection locations, and 

### with the volatility 

### of the ammonia, it


### was expected to readily volatilise even 

### if trctnsitorily -combine-d 

### with sulphate or chloricje. 

### lt 

### was not 

### known. however, 

### if this would develop a· cyde with sulphur
or even chloi"ine l 13,14l that might impair reaction of NH-3 with**NO~** as 1t circulated. It appears that the presence of sulphur 

### has little effect on 

### the use 

### of ammonia
as a reagent. PlantE, which fired 100 per c.ent.petcoke, had high 

### 502 in the injection area, high dinker

### 503 and yet experiehced some of the highest reduction efficiencies. This has fed to the perhaps intUitive conclusion that the presence of 

### sulphur, all other things equal, 

### has no 

### apparent detrimental 

### impact on the SNCR reaction.


### Catalytic reactions from kiln feed The correlatiori between iron content in the kiln feed and researchers have noted
an increase In the reduction efficiency of SNCR reaction.L1 5, 16llt was observed that Plant A, D and E, whkh had higher iron**perc~ntage** in klln feed than Plant Band 

## C. h-c.d rhuch higher SNCR efficiei'ndes, 

### It should a!so be noted that these plants. als-o used ammonia instead of urea and


### are the smaller sized of the five plants. 

### The presence 

### of some catalytic 

### reduction with ammonia 

### either in the inje-ction location or at higher portions of the tower at lower temperatures cannot 

### be discounted. The SCR reaction can occur at temperatures from 570"F 

### and 8406F and this temperature range is present at the

## 1.2-,----------:.-----, -II- 

## w/o CO

0.8 

# 0 z ;::::: 0.6- 0 

# z 0.4
0.2 --+- 

## 100 ppm CO**~** 

## 1000ppmCO



## -+- 

# sooo ppm

# co

Horoogeneous Case 

## Quench Rate=-260C/sec**o~~~~~~~~~~** 

## 600 700 800 

## 900. iQOO 1100.1200 

# Tempera!llie(G} Figure3. 

### Effect

## Qf CQ

### On,$.t:'{fR

# ¥14**rurutl:~~_fqr**

### hOmOgeneqUs**~ditions** 

### with 

### NOi

## =500**P~-~/NDi ':;;:::,1.5~_:_and-.a_thermalquencll** 

### rateof260K/sec. 

### Figure 19; EffectofCO on SNCR


## top Of

## preheater**toviers-~** 

## so i:efentibii>tfliie:
nthe area of greater'th.::in 1 

### 0-.secOndS

# -at this temperature -are 

## exper!Emced. rn,:ci.IIJb.e preheater towers.**Despite-the·ab?e~~-** 

### · of a traditional catalyst**s,uqh.:as:-.q~!d:e~**

### .. of titanium and vanadiu'm,**the,:influ·~n,ce:** 

### of increased NO'X. reductio'n 

# py .t_at_a:l¥tl:t 

### mechanisms_cannot be_.-dis¢Q_i:!ri±¢d-

# rrP.PJ the 

### testing- conducteil

CO effect -on SNCR reactiOn·-, 

### CO was ·shown·to**ha>/ebol:h•••~o.>nd\i'"** 

### and negative

# impa:ct**<on.lh''·'~·ed.tJc!ign** 

## t!X·'ob;n\fliSt,

..a high GO atmosphere with**lftil~;o~;y~en,•or** 

### ·J.!)_su_ff)crie?t mixirtg of**t.<l'-!i<~~·qs ,sr'o~ltllechaili**  

### :re·action of**•b,;Jr~(Jutqf**

## c:oan.cl the ·continuing**/tq*'i~.n,:ol'x<<oi<;als** 

### when -both Oxygen ln approXimately

(1 

## I (2) (3) (4).


### of NOx with

# th~,(~~~~~**~:ii~~··~;r;:~~~6:;, ,,,)~~~~"'~;~;::~~1~=** 

and the N 

### of (0 

### to C02 

### the reaction of
the radical pool

# ~~t:i~:it:;~;~~~~ the-rise_r

SiZ¢ 

### frl EMISSIONS CONTROL



### and construction of preheatertowers. available raw materials orfuels. However, it 

### does appear that three key approaches for 

### SNCR NOx reduction are identified 

### and one or more should b-e achievable 

### at most locations, to approach desired efficiencies.



### The first approach to riser duct reducti.on 

### -of kiln NO>: 

### relies on the tradittona! reduction 

### techniques., requiring high temperature, sufficient oxygen and 

### low CO_ In most cases these conditions should be available ln 

### ca!ciner systems, 

### and for preheater·ki!ns 

### it 

### is the only option. However, 

### lf suffiCient oxygen is not present in the riser or 

### kiln exit. due t6 carryover 

### of unbUrned fuel or'insufficient 

### oxygen from the kiln itself, 

### then efficiency forthis 

### reduction Will 5Uffer. Additionally, this location upstream of the calciner 

### will only reduce 

### kiln NOx, which 

### is pr-esumed 

### to be 

### the majority 

### of the NOx formed, 

### and 

### will not reduce NO>< subsequently generated 

### in the caldnerfrom fuel 

### of feed nitrogen.

The :Second approach for 

### SNCR reduction is to 

### use a post calciner location. Jn most situations**tem~ratures** 

### are lower In these regions than in the riser duct. and choosing 

### a spot 

### with adequate 

### oxygen and 

### small amounts of CO will lead to 

### greatest efficiency. ln 

### calciners with limited retention 

### time for burnout of 

### CO, such 

## a locatfon may not exist or may even be at the exit 

### of the lowest cyclone. 

### However for most 

### new calciner designs, a location should be available in the burnout
zone 

### wlth sufficient oxygen, 

### CO and temperature. D.ependlng 

### on fwel 

### usage arid its 

### associated volatility, a location prior to the lowest-cyclone 

### should be sufficient.

The 

### other distiilct "advantage of post

### calclner injection is the reduction 

### of total NOx produced 

### from both combustion
zones. 

### While 

### it is' assumed that most stack NO:.: is produced 

## vra the thermal NOxmechanism in the kiln, calculations ·at Plant A showed apprOximately 20 

### per cent 

### NOx generation 

### in the calciner. Frbm studies conducted at Plant C, the majOrity of

## Nox generation again occurs 

### 1n the calciner. Th.1s NOx generatlon was also noted by Tokheiml1Bl 

### in studies of the impact of staged cor'nbustion on NO-x reQuction, 

### where it was noted that 30 to 

### 40_per cent of the total NOx was· caltiner 

### generated, A riser duct 

### iiljediOn location, sacrifices the ability to 

### reduce NOx from 

### this source.EMISSIONS CONTROL



### F1gure 20: Pl11nt Amolar NOxba!am:e



### .........

# -

...

# \

# ~--**~** \

...._

# __ II\

# "

# .....__

Another benefit of the**post~calciner** 

### injection is the use of inherent staged caldner combustion for initial reduction 

### of kiln NOx. via staged**~ombustlon** 

### design arid**Operation~** 

### This redu_ction mechanism 

### will be present integral to the Operation of the calciner and should be used to 

### reduce
as much kiln- generate-d NOx as possible, with SNCR 

### treating the residual unreduced 

### NOx or newly created calciner NO_){" This aHows for accurate NSR calculations and 

### reduction efficiencies from SNCR to be 

### calculated.

To illustrate this point, a tOtal NOx 

### balance calculated for PIJnt A is shown in the**fol~owing** 

### ftgure. 

### Cohcentrations of NOx at the kiln inlet are known, as wei!
as estimated flows from C02 balances. 

### Molar rates 

### of NOx as 

### N02 

### are given for 

### NOx from the 

### kiln burning zone as we\!
as NQx generated in the. calciner. 

### lt was estimated that approximately 40 per cent 

### of fuel nitrogen was converted to 

### NOx.- The 

### reducing zone created 

### in the calciner,


### even with 

### the kiln 

### operated in an 

### oxidised 

### state, reduces around 45 per cent of 

### both NOx from 

### the kiln and NOx from calciner

## p::;::~wr•c:·oa:;r~::-.·.

# 1

fueL The reducing capacity 

### of staged combustion can 

### be 

### increased 

### by the presence 

## ot CO; howeverduring testing 

### this 45 per·cent reduction 

### was achieved 

### with at least

### two per cent oxygen at

### the kiln· 

### exit Finally the 

### molar ratio of the 

### Nbx expressed 

### as N02 is given at the 

### exit 

### of the 

### system or the 

### stack.

If 

## two separate scenarios are evaluated 

### with injection locations in the riser 

### duct and in the upper portions of the calciner with 

### the same NSR and reduction efficiency, 

### the following is observed. The post ca.lciner location will cause correspon'dingly 

### greate-r overall stack**NO~** reduction. due to the reduction of both fuel NOx from the caldner and thermal 

### NOx from the kiln. Also, the calciner reducing conditions de-stroy more of the 

### burning zone thermal**NO~.** Table 7 shows 

### the theoretical reductions based on a 0.7 NSR at the actual location of reductlon (molar 

### rate of NH3 divided 

### by molar rate of NOx at the location of injection). 

### the overall 

### 1'-JSR (molar rate of NH 3 divided by the uncontrolled molar rate 

### of NOx at the stack) and a 75 per 

### cent efficiency of reduction at each location

. The overall efficiency of NOx reduction 

### is the reduction 

### of the l.mcontrolled 

### NOx
versus 

### the theOretical reduction 

### of NOx 

### achieved at each location. 

### Thes'e results
are 

### achievable with ammonia at Plants 

### A, D and 

### E, 

## as irlustrated in Table 

### 7.

The results demonstrate that

### -even though each location 

## was- assigned 

## a 0.7 NSR, to actually achieve this 

### NSR jn a kiln 

### riser with high 

### exitoxygen requires: 

### much more reagent In addition, even 

### though the riser 

### location reduces the 

### NO:.:: 

### wlth 75 

## p_er cent efficiency, this results in an 

### overall 41 

### per cent 

### reduction from uncontrolled 

### NOx levels 

### .at the 

### stack-. 

### As stated earlier, 

### this is because 

### this location has 

### no opportunity to 

### reduce NOx .generated 

### irom cakiner fuel. For 

### the riser duct location to achieve the same**reduction~** 

### as_the post caldner location,
a localised NSR rate of 0 

### 865 (185gph) 

### wOuld have to 

### be used. Thus, we 

### see the advantages ofuslng 

### SNCR at a postcalciner location, 

### This relationship 

### of red.uction 

### would 

### further be ·-exagge_rated 

### ifthe kiln were run 

### with lower excess oxygen and had loy.ier levels of 

### klln exit 

### NOx. The presence 

### of unburne-d tyres or ·other 

### lump fuel 

### introduced 

### atthe kiln 

## ex·1t could lead to 

### this -situatiOn. 

### In these 

### cases, injection 

### points at 

### the calclner 

### exit would 

### be the only acceptable location for 

### SNCR. 

### As for preheater

### kilns, this issue is avoided



### as no additional fuel 

### or ther.mal NOx 

### is 

## ge·nerated- past 

## the burning zOne. Lastly,


### we have not seen a:ny ·ability**fo~** ammonia
or urea to remain 

### unreacted and circulat,:; 

### pci.:st the calciner, 

### if injected in the rlser duct.



### The thlrd approach 

### is to adopt multiple injection points 

### for ammonia-and/or


### urea. Junker[5

### J

### at the Slite cement plant 

### in Sweden achieved excellent suCcess with 

### techniques 

### including the 

### use of 

### 12 injection points, redudng the NOx emissiOns to about 

### 11b/t of clinker.

References 

### [1] Kupper. D. and L. Brentrup; ''SNCR technology 

### for NOxreduction in the cement 

### indust1y"; 

### Krupp Polysius. Germany; 

### March 1992; pp. 4-8. [2] Penta Engineering Corporation Report
on 

### NO>: Formation and 

### Variability in Portland Cement Kiln Systems Potential Control Techniques and Their Feasibility and Cost Effectiveness. Penta Project No-.EMISSIONS CONTROL



### 971212_ Prepared for the Portland CementAssodation. 

### PCA R&D 

### Serial No. 2227. Skokie, IL. 1999. [3] Scheuer, A., Non-cataJytic 

### reduction of NO with NH3 ln 

### the cement burning· p'roc¢_!?S. 

## -Z!;ment-Kalk-.Gip.s, Nci. 3/1990, VV1esbaden. Germany. 

### [4] Campbell, LM

.. O.K. StOne, and GS 

### ShareeL Sourceb-ook: NO';( Control 

### Technology Data: U.S. EPA, Air and Energy Engineering Research 

### LaboratOry.**_'EPA-600-/2-91-029~** July 

### r991. t5J Junker, P., Member of

## the Techni_gd Working 

### Group, Swedish Environmental**pr~feCtion**

## Agency, Ui.nsstyre1sen Gotland, S-62185 

### Visby, Sweden 

### [6J Euro-pean lnlegra:te.d pOllution Prevention and 

### Control Bureau (ElPPCB). 

### Reference :DOcuinenton Best Available 

### Techniqu-es in the 

### Cement,:U,d-Uine Manufacturing Industries. World 

### Trade Center, Seville_. Spain. 

### March 2000. 

### f7l Yee. 

### G.M. Suggested**Co,n~l M~asure**  

### fOr the Control of 

### Emissions of Oxides of NitrOgen 

### fr:pm Ceirlent Kilns. Presented 

### to the State ofCalifornJC\•.Alr-Resourc_es_BOard for Discussion
on October 21, 1981. 

### [8] Haas, GA Selective

## NMcell)!ytic**~ed~ction** 

### tSNCR): 

### Experience with the 

## EXXO:n Thefri'1ZI**DeNO~** 

### Process. Presented at the NO:.: Control V**t:Onferen~e.**

## ··toundl ofIndustrial**Boi~er** 

### 0-.•.:ners. Long Beach,**CA.-_Februilry10~'11,** 

### 1992. !91 Lin, 

### M.L. MJ.**Knenfeirl~·fue1**

## Tech Inc.. "Cement Kiln 

### NO:.: Reduction Experi_enc_e_

### ~s!ng_·_tne~NOxD~ 

### Process," 

### proceedings 

## o·f the 2000 lr:'Jfem.atjo:nai_JO,int Powe.r Generation Conference, Miami Beech, 

### EL,)yly;23S26, 20.00. [10] Rose, D., K. Alde;r;·:ahd:b

..

### :·;;Ei-pddihg·.;··jlNOx Abatement with the SNCR- 

### Proce.ss:in Kiln**:~n_t5-.with** 

### Staged· Combustion": kn;pp 

### POJys)uS-,. 'Seckt.i'rt{Gefnlany [11] Steuch, H.E., J. HifieT

### WJ';.. -Sun.-MJ.--Blsnett, and 

### D.W. Kirk: "Reduction of N{)x £missjons_,frQm a·Dry Process Preheater Kiln with**Caltin~r**

### Tt}_(Ough the- Use of.the Urea 

### Based SNCR Process''; 1995.'!E£E Cement Industry Technical Conference; XXXVI**C_ofift:{t'eliC~:·Hec_ord;·Se:n** 

### Juan, PR; June 1995;p. 466 

### (12] Schmidt A, 'The·ModUlar PDi_f5ius Caldner 

### Concept- A Solution far All

### Ap~liCationS:b,Y:-<;:Orr\binatlon

### .... ECR'\ Seminar; 

### Experiences 

### with Precaki!ler:

# :KilnS;·semburg Gerrriany. November 2004. [13] Ritzmann,

### H~. "'Kr{!istaUre·:in 

### {?rehofe_nsystemt:nM ,.Zement.:. 

### Kalk-Gips 24 (1971), 

### p ..338 

### [14} Sprung, S., "-DEJS**V¢rhal.t~n-·:.des'·?Cllyrefels** 

### be.im Brennen
von 

### Zementklinker",**l'98inq~stfieZe.itur.g89** 

### (1955), 

### Nr. 96. p, 124 [151 

### Zamansky. V.M._. V.\1. 

### LiSslariski, a.'ld HM. Maly.**~Promotion** 

### -of 

### SNC'R

## oy:s.f.X:iiUri_-Ltompounds," Energy 

## and Environmental Research cOfPO_fiipon. ·18 :Mason, bv!ne, CA 926i8 [16] Yang. R. 

### T., and K::-T

## _Li**·_:··~·~ialytlc** Decomposition of Nitric Oxide on Sodium**Ferrite·~_,** 

## Jryq.:Eng;**'(:~em**

## . .-·R¢s. DeY., Vol. 21, No.1.1982, 

### p. 407. [17] 

### Brouwer. L M.P.**H~ap;_ :o:w~-**  

### .Pershirig,-ahd PJ. Smith, Proc. 

### Combust. lnst.**26;2.117-212~** 

### (1996) (18] Tokhe;m, L, -TheImpactofStaged Combustion on**th~** 

### Op--eration of a Precaldne:r C:ement'!(J!n", PhD Thesis, T-ekmark Colle-ge. Porsgrunn**Norway._~-~·**