“Comparative analysis for NOx Analyzer selection For Coal fired power plants In view of New MOEF Norms”

1. “Comparative analysis for
NOx Analyzer selection
For Coal fired power plants
In view of New MOEF
Norms”
By
Santosh Sawant
Instrumentation Control and Electrical Engineering
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2. Index
 INTRODUCTION
 DESIGN REQUIREMENTS FOR NOx
ANALYSERS IN POWER PLANT
 SAMPLE CONDITIONING SYSTEMS
FOR NOx ANALYSER
 TYPES OF NOx ANALYSERS
 CONCLUSION
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3. Background
 Climate Change Discussions – Changing World
political orientation
 Paris Conference December 2015.
 Global thrust on reducing NOx and SOx
 The Primary sources of NOx pollutants is :
 Mobile sources (Vehicles, Ships, Planes etc) – 50%
 Electric Power Plants – 20%.
 Everything Else (Other human activities) – 30%.
 New Norms for Indian Power plants designated by
Ministry of Environment
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4. What NOx means…
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5. How NOx affect Environment
 NO2 reacts in the presence of air and ultraviolet
light (UV) in sunlight to form ozone and nitric
oxide (NO). Tropospheric ozone is the primary
constituent of smog.
 Acid Rain
 Nutrient enrichment problems (eutrophication)
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6. New Pollution Control Norms
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7. New Pollution Control Norms
 NOx - earlier norms were equivalent of 600mG/Nm3
(approx)
 which now stand at 100mG/Nm3.
 It seems that almost all coal fired power plants
commissioned after 2006 in
India will have to install :
 Equipment called Selective catalytic reduction (SCR) or
SNCR at downstream of boiler furnace to Reduce NOx
emission – irrespective of type of coal.
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8. Wind Turbine
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9. Challenges for SCR inlet
and outlet NOx Analysers
 NO and NO2 gas highly soluble in water / moisture
 High accuracy and repeatability is required as
these will be used in closed loop control.
Response time should be fast.
 High temperature of the order of 350 deg C as
against a temperature of 120 deg C seen by
Conventional Analyser at Stack.
 % of coal ash and moisture will also be higher as
these analysers will be located upstream of ESP.
For Indian coals, the dust concentration will be as
high as 80-84 gm/Nm3.
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10. Challenges for SCR inlet
and outlet NOx Analysers
 No proven technology available for Indian coal
conditions which has high silica ash content of 55-
60%.
 Wide Range required as SCR inlet NOx is
substantially reduced at the SCR outlet
 NOx generated in Furnace of Coal fired power
plants comprises of NO to the extent of 95% while
the Norms typically refer to NO2 released in
atmosphere at Stack – so analyser at SCR shall
be tuned for NO measurement and Not NO2.
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11. 1. Chemiluminiscence Analyser
 NO + O3  NO2* + O2.
 NO2  NO2 + Photoelectric Emmission
 Emitted Photons are measured which are indicative of Nox
concentration
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12. 1. Chemiluminiscence Analyser
• Requires extraction probe and sample conditioning
system
• Minimum measuring range of 0–2 ppm.
• Accuracy and repeatability very high.3/12/2017 12

13. 2. DOAS- Differential Optical
Absorption Spectroscopy
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14. 2. DOAS Analyser
 R1 : Source intensity when the filter wheel is open.
 R2 : Source intensity when the filter wheel contains a cuvette with NO,
 M1 : Intensity of the source less that absorbed by gas in the sample cell.
 M2 : Intensity of the source less that absorbed by the NO gas filter
 The absorbance caused only by the analyte, NO, in
the sample cell is thus given by :
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15. 3. In Situ Gas Corelation Analyser
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16. 3. In Situ Gas Co-relation Analyser
 No Gas sampling or conditioning system required.
 Less Maintenance
 Operates in IR for High Range and UV in Low range
measurement
 Comparatively Low accuracy in Low range
measurement
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17. 4. FTIR Spectrophotometer
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18. 4. FTIR based Analyser
 Most suited for multiple gases measurement
 Comparatively Low Accuracy
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19. Sample Gas Extraction System
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20. Sample Gas Extraction System
 Dilution Probe (Chemiluminiscence type)
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21. Comparative Analysis of
Branded Analysers
Parameter Chemiluminescence
Analyser
In Situ IR Gas co-
relation Analyser
Cross duct UV
Spectroscopic
Analyser (DOAS)
FTIR
Spectroscopic
Analyser
Manufacturer I II III IV
Sampling Probe Dilution Probe with
Critical orifice
In situ Multipoint
probe
Cross duct trans-
receiver
Hot Extractive
probe
Possibility of
Water interference
Minimum Minimum Minimum Exists
Impact of flue gas
Pressure and
temperature
variation
No Yes Yes No
Lowest Range 0-0.1mG/m3 0-750 mG/Nm3
(0-1500 ppm)
0-50mG/m3 0-125mG/m3
(0-250 ppm)
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22. Comparative Analysis of
Branded Analysers
Parameter Chemiluminescence
Analyser
In Situ IR Gas co-
relation Analyser
Cross duct UV
Spectroscopic
Analyser (DOAS)
FTIR
Spectroscopic
Analyser
Manufacturer I II III IV
Sampling Probe Dilution Probe with
Critical orifice
In situ Multipoint
probe
Cross duct trans-
receiver
Hot Extractive
probe
Lower detectable
limit
0.1%
(0.5 ppb for 500 ppb
range)
1% 1%
0.5 mG/m3
1%
Filter size for Ash
particle removal
2 Micron 20 Micron Not Required 3.5 Micron
Response time 40 seconds 10 Seconds 43 seconds 7 seconds
Precision 0.1%
(0.5 ppb for 500 ppb
range)
2% 0.41% 1%
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23. Conclusion
 FTIR based IR spectroscopy is suitable for wide variety of
pollutants, irrespective of natural absorption spectrum of the
material. But the FTIR analysis requires reference spectrum which
keeps changing with Ash composition / coal composition and needs
highly trained technicians to calibrate and operate the analysers.
 NO and NO2 components absorb radiations in UV range hence
using IR spectroscopy (Gas co-relation technique) is not most
suitable.
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24. Conclusion
 With stricter norms and high ash Indian coal conditions, we need to
select an analyser which has higher accuracy, higher availability and
better dust elimination.
 In view of this Chemiluminescence analyser with advanced dilution
probe seems to be most suited and these have worldwide proven
performance .
 Alternately UV based In-situ Gas correlation analysers are a good
proposition – however these need to prove their performance in high
temperature and high ash environment at SCR inlet.
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