The document discusses NOx assessment and reduction techniques. It provides information on: 1) NOx emissions from cement kilns can range from <500 to >1500 mg/Nm3 without additional controls, depending on factors like fuel used, kiln operation, and calciner design. Getting below 500 mg/Nm3 typically requires optimized reburn design or retrofits. 2) Hot reburn designs by CINAR involve maintaining temperatures of 1200C or 1300C for short residence times (0.15-1 seconds) before additional air/meal introduction to allow NOx reduction reactions while avoiding re-oxidation. 3) Optimizing SNCR for maximum NOx reduction requires understanding the impact of CO

2. CINAR NOx Assessment
and Reduction
Dr Tom Lowes

3. NOx Assessement
 NOx is normally measured quite well at the stack for legislation
purposes and varies from < 500 to > 1500 mg/Nm3 at 10% O2
without SNCR
 This range of NOx emissions are a function of:-
 The fuel used
 Operation of the kiln
 Design of the calciner
 To get to < 500 mg/Nm3 without AFR or SNCR requires either luck
or a CINAR hot reburn design either in the plant build or retrofit
afterwards
 The concept of reburn is not new, however as developed by Hupa
and applied by CINAR is, as detailed in its 2011 IEEE paper above,
namely:-
 1200 C reburn and staging for @1sec at a SR for vols at < 0.9 (locally)
 1300 C for 0.15 sec followed by @ 0.5 sec with meal addition for a
customised retrofit for calciners (including AT) at a SR < 0.9
 The reason for the RT before, the TA is to allow the CHi reburn of
NO to NHi compounds to further react to form N2 and not with O2 to

4. NOx Assessment
 The next 2 slides show the reactions/kinetics,
 This is followed by a slide that shows NOx from 2 new FLS
kilns, one that needed a hot reburn 3 at 10% O2 and another
that did not as by a miracle the TA was delayed mixing with
the coal volatile
 N.B for a complete pass through of kiln NOx the slope is @
0.4 and zero for 100% reburn

5. Fundamentals of NOx
Fuel N HCN/NH3
NO Products
N2
Thermal NOx
NHi - this is
SNCR Opt. T
very CO
dependent
+CHi / HCCO
Reburn – 1 sec plus
1200C, 1300C and higher
< 0.2 secs
AFRs with high volatiles a
benefit, need to aim for
30% sub stoichiometric
conditions
Staged combustion of Fuel NOx,
Need to combust the vols sub
stoichiometric by @ 30 %.
N.B. In actual practise the
measured vols are an
underestimate of the practical
situation by up to a factor of 2.
It should be noted that
this is the SNCR reaction
and is very temperature
sensitive to drop the NO
via the NH3 route
To paraphrase Cardinal
Newman “Optimum
Reburning/Staging is
easy just like walking on
a tight rope at 100m”
Needs
TIME

6. Optimum Air Ratio for Reburn and Staged
Combustion
Target initial
operation for
vols in riser
Normal Plant operation
based on volatiles, if NHi
mixed fast with TA then
no good reburn or
staging

7. Key Reactions in Hot Reburn

8. y = 0.0365x+ 192.32
y = 0.1143x+ 294.16
y = 0.3172x+ 569.05
y = 0.2868x+ 644.92
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
1000.0
0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0 1600.0 1800.0 2000.0
S
t
a
c
k
m
g
/
N
m
3
a
t
1
0
%
O
2
KBE NO ppm
St Gen /Pueblo before TAD mods/BurnersDown Stack NOx vs Kiln NOx
St Gen BurnersDown Before TAD After TAD
Linear (St Gen) Linear (BurnersDown) Linear (Before TAD) Linear (After TAD)
BurnersDown
rebutn 73%,
staging - 50%
STGen
reburn 92%
staging 70%
Plant G and SG

9. NOx Reduction
 The next 2 slides shows a comparison of volatile residence time and
temperatures for Plant G and SG
 If SG had had temperatures as low as G then the NOx emission levels
would have been higher than current
 It should be noted that further reduction could have been achieved at G via
more burner optimisation, however the Plant were happy to get below 2.3
lbs/st and there is room for further improvement at SG via MI-CFD driven
calciner burner optimisation
 While reburn will drop the NOx emission, it is a also important to stage the
N in the calciner fuel – the constant on the previous slide
 Normally the maximum value of this constant seen is @ the NOx level
associated with the fuel volatile * % N, however the 3rd slide shows an
evaluation of the base case data from Alesd shows that in high local O2
conditions – as in an RSP – on devolatilisation then the calciner fuel NOx
contribution can be higher
 When there are more volatiles available than in a bituminous coal then the
reburn becomes easier. The 4th slide shows a horizontal line with brown
coal.(FLS info) The 5th slide shows the hot reburn plus MI-CFD
breakthrough in NOx reduction compared to the classic information

10. 0.050
0.045
0.040
0.035
0.030
0.025
0.020
0.015
0.010
0.005
C-vol. (fr)
17m
.85s(20m/s)
Plant G needed retrofit Plant SG No retrofit needed
0.050
0.045
0.040
0.035
0.030
0.025
0.020
0.015
0.010
0.005
C-v.i(fr)
0.230
0.207
0.184
0.161
0.138
0.115
0.092
0.069
0.046
0.023
0.000
O2 (fr)
12m
0.15 sec
- 3.5 m
Hot
reburn
Then 0.5
sec
with meal
0.230
0.207
0.184
0.161
0.138
0.115
0.092
0.069
0.046
0.023
O2 (fr)
20m
.65s(30m/s)
Total RT:1.5
10

11. 1400
1280
1160
1040
920
800
680
560
440
320
200
1400
1280
1160
1040
920
800
680
560
440
320
200
Temperature Simulations
Plant SG
1200 C maintained
Plant G before reburn mods
That moved the burners
down 3.5 m -1100C maximum
It should be noted for
Plants with an excess
of SO3 over alkalis in
the hot meal that hot
reburn will produce
build up issues
This is well covered
in the 3.5 m hot
reburn zone at
Pueblo by a non
coating refractory
plus blasters
It is believed that St
Gen has some build
up issues

12. Stack NOx = 0.63KBENO+ 629.
R² = 0.7763
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 200 400 600 800 1000 1200 1400 1600 1800
S
t
a
c
k
N
O
x
Kiln NO
Alesd Calciner Stack NOx vs Kiln NOx
Dilution and conversion to NO2 would mean the stack NOx was 0.82 KBENO
The 0.63 factor indicates 25% reburn with tyres and sludge
For the average KBENO of 986 from the data set , this means @ 50% stack NOx is from the kiln
and 50% from the calciner
The calciner contribution to the stack is very high considering the fuel (25% calciner) split
The 629 mg/NM3 at 10% O2 represents almost a 50% conversion of the fuel N (3.5%)which is an
exceptionally high %age for a < 30% Vols coal
Recommend lower N coal , more kiln fuel and higher KBEO2
RSP

13. Brown Coal a good Natural Reburn for SR < 0.9
Note the emissions levels are @ 250 mg/Nm3 at 10% O2
It appears as if with a high volatile
Brown Coal/Lignite or an AFR that a
hot reburn may not be needed and a
SR < 0.9 plus @ 0.6 sec RT before
O2 from the TA may be all that is
required to get a good reburn

14. Reburn Guidelines Before Hupa and CINAR
80% reburn
at 6 N/MW
At Pueblo
MI-CFD
Rules

15. Typical Hot Reburn Installation
NO [ppm]
Normal FLS
configuration.
Coal and meal
inlet @ 10 m
below the TA inlet
giving a stack NOx
of 800 to 1000
mg/Nm3 at 10%
O2
Note local NOx in
red
Hot Reburn for coal
moved the coal injectors
0.15 secs RT below the
meal inlet and
optimised their angle
and velocity via MI-CFD
at to get stack NOx of <
500 mg/Nm3
Note red zone has gone

16. Conclusions on Reburn
For reburn to work as effectively as possible one needs:-
 Local micro substoichiometric combustion for at least 0.5 secs before the gases
mix with the TA to complete the combustion
 The temperature of the reburn as well as the RT at the temperature will depend
on the fuel used. For a normal bituminous coal 0.15 sec is required at 1300C
followed by @ 0.5 secs at @ 1000C (meal quench) before the TA .
 For lignite and AFR the RT appears to be more important than the reburn
temperature
 For a hot reburn section, non coating refractories and blasters/cardox are
recommended
 This is normally manageable for ILC, RSP calciner are more difficult but
manageable by taking some of the fuel out of the calciner and reburning in the
riser.
 AT calciners need a detailed knowledge of the KBE O2, CO and NOx
distribution and detailed design of the reburn burners to exploit this. CINAR
have had some success in the US with a AT calciner on low volatile coal at 30%
in the AT calciner, as a shown on the next slide, which involves a JAMS to
produce better local sub stoichiometric conditions. With a lignite aor volatile AFR
the burner system and even the use of JAMS may not be needed and can be
developed via MI-CFD

17. Kiln Inlet
KBE O2 : 5 %
Kiln Gases: 152327 Nm3/h
Temperature: 1200 oC
NOx: 1200 ppm
1.1%
1.3%
Exit, NOx = 450 mg/m3
> 50 % Reduction
Oxygen Coal Volatiles NOx
Higher JAMS
27973 Nm3/h
4 Burners (1/4 in each)
Total Transport Air: 2210 Nm3/h
Total Fuel Flow Rate: 6.76 t/h
Temperature: 77 oC
Case 10: 5% KBEO2, 4 Burners(2Original,2Lower) Upper
JAMS

18. State of the ART
Process Knowledge on SNCR
Tom Lowes

19. NOx Reduction with SNCR
 While CINAR would always advocate looking at a hot reburn
optimisation in preference to SNCR, customers also need to
be able to drop NOx via SNCR to go even lower on some
occasions while minimising NH3 slip and using SNCR as
effectively as possible
 The forthcoming regulations in the EU where 200 mg/Nm3 at
10% O2 may have to be met for all cement Plant using AFR
means that even hot reburn and even customised calciner
designs will struggle to meet these numbers.
 Hence in the future CINAR will need to help its customers
optimise the use of SNCR as well as hot reburn to meet its
permit limits
 This note gives info on what controls the effectiveness of
SNCR
19

20. Course on
Environment 2006
SNCR for NOx Reduction in Cement
Production
 Temperature is most critical for successful SNCR
 Urea, photochemical residues need higher temperatures than
ammonia (impact of local temperatures)
 For calciners Urea is not as effective as aqua NH3
 Typical molar ratios applied (1 -2 )NH3NOx ratio
 Efficiencies 40 to 80%
Generally recognised
to be the optimum
range for NOx
reduction and
Minimum NH3 slip,
but is it?
What about the
impact of CO?
How many injectors?
Micro mixing?

21. Impact of CO on optimum SNCR Temperature
21
Optimum temperature
with 1000 ppm CO –
850C

22. Calculated Impact of CO in SNCR
Optimum Temperature
22
Hence for optimum SNCR operation it is
needed to:-
• Identify CO and hence the optimum
temperature range
• Get good coverage of the process gases
with the injected NH3 (multiple lances)
• Ensure a good local micro mixing – JAMS
if needed
•CFD provides an optimal solution
The next slide shows some SNCR optimisation work based on the CO level

23. SNCR utilization
Calciner Temperature Profile & Lance Placement
830 o C
880 o C
950 oC
900 oC
880 o C
830 o C
900 oC
950 oC Lance placement 1
Recommended temperature
range of 950 to 1000 oC
8 nozzles flowing 10 gpm of
ammonia
80% reduction
Calciner DIA ~ 6100 mm
Lance placement 2
Lower than recommended
temperature range
8 nozzles flowing 8 gpm of
ammonia
80% reduction
Calciner DIA ~ 6100 mm
Lance placement 3
Lower than recommended
temperature range
6 nozzles flowing 6 gpm of
ammonia
88% reduction , with 25%
less NH3
Stage 5 inlet DIA ~4300 mm
NH3/NOx = 1
Solution 20%
aqueous NH3
CO ex calciner 1000
ppm
In position 3, 200 mg/Nm3
could be achieved on a
regular basis with an 88%
efficiency and no NH3 slip
Aqueous NH3 of < 30%
used in US for Homeland
security reasons and safety
regulations
There is not much use of
Urea as it is much less
effective than NH3

24. Conclusions on SNCR
 Significant improvement can be made in the cost NOx reduction via
SNCR by:-
 Knowing what is the best temperature location as a function of CO
 Where best to located the NH3 injectors as a function of the impact of
the NH3 solution on local temperatures
 How much NH3 to put through each injector – and its design - as a
function of the predicted NOx profiles in the calciner
 The key Questions to lower NH3 costs are:-
 What
 Where
 How
 These questions can only adequately be answered with MI CFD
experts who are very conversant with Cement Production.