1. Emission measurment II. Gas analyzers
Viktória Barbara KOVÁCS

2. Emission Measurement Harmful components Emission measuring systems
In-situ: (in-stack, cross-stack) measurement
Ex-situ: extractive measurement: „analyzers with a measuring probe”
Requirements of analyzers
Reference methods: Analyzers at D.E.E
NDIR (CO, CO2, CH4, ….) Servomex 1400B4 SPX O2/CO2
Thermo 48C CO
(H)CLD (NO, NOx,) Thermo 42C NO-NO2-NOx
FID (THC, CxHy, VOC) Bernath Atomic Modell 9900 THC
PMD (O2) Servomex 1400B4 SPX O2/CO2
Measuring Cell
Chromatography
Older techniques

3. Harmful components of flue gas
CO2: GHG
CO: poisonous (suffocating from ~700ppm)
THC (VOC, PAH)
depends on molecule:
Methane: GHG, but PAH carcinogenic, etc.
NOx: acid rain
SOx: acid rain
(Dioxin, furans: teratogenic, mutagenic)

4. In-situ measurement Advantages Disadvantages Measuring section window
mirror lens
Condenser lens
UV transmitter lamp
Triple reflector
UV detector
mirror
Optic grid
Beam splitting mirror
Evaluation unit
Measuring unit
NOx reduction with SCR_SICK.mp4:
Advantages
Direct and immediate measurement in process
Non-contact measurement: suitable for aggressive or corrosive gases
Very short response time
Very low maintenance requirements
Disadvantages
More expensive
Simultaneously measurement of more component is critical
Humidity causes problems

5. Sample conditioning system
Ex-situ measurment
Advantages
For applications with high dust concentration
Measurement is possible far from the emission source
More components can be measured simultaneously
Low concentration is measurable
Suitable for difficult measurement tasks
Disadvantages
More units
High response time
Corrosion risks
Condensation risk
Soot deposit („pipe remembers”)
Sample conditioning system
Analyzers
Sample
heated pipe
Standard gases

6. Requirements of analyzers
Physical working principle
Fast (reaction time under sec.)
Stable in time
High sensitivity
High selectivity
Low inter-sensitivity
Linear characteristic
Independent from ambient condition
Protected from ambient
Cheap

7. IR spectroscopy
deals with the infrared region of the electromagnetic spectrum
it can be used to identify and study chemicals
molecules absorb specific frequencies that are characteristic of their structure
the frequency of the absorbed radiation matches the transition energy of the bond or group that vibrates
passing a beam of IR light through the sample: when the frequency of the IR is the same as the vibrational frequency of a bond, absorption occurs
λ: 780 nm –1000 μm  (f: 300 GHz – 384 THz)
IR_1.avi:

8. Vibration of CH2 in a CH2X2 group
Symmetrical stretching
Antisymmetrical stretching
Scissoring
Rocking
Wagging
Twisting

9. NDIR (Non-dispersive infrared absorption)
NDIR.avi:

10. NDIR (Non-dispersive infrared absorption)

11. NDIR (Non-dispersive infrared absorption)

12. NDIR (non-dispersive infrared absorption) IR Spectrum

13. NDIR – CO2 IR_3.avi: https://www.youtube.com/watch?v=FR9DFkenWUU

14. FTIR - Furier Transformed IR Spectroscopy
measurement technique that allows one to record IR spectra
Infrared light is guided through an interferometer and then through the sample (or vice versa).
A moving mirror inside the apparatus alters the distribution of infrared light that passes through the interferometer.
The signal directly recorded, called an "interferogram", represents light output as a function of mirror position.
A data-processing technique called Fourier transform turns this raw data into the desired result (the sample's spectrum): Light output as a function of infrared wavelength (or equivalently, wavenumber).
The sample's spectrum is always compared to a reference.

15. NDIR/ FTIR comparison Gas Filter Correlation IR
Narrow frequency range defined by the filter
One filter for one component
More component more filter
More filters more calibrations
IR_2.avi
Fourier Transform Infrared (FTIR)
"Fellgett's advantage" or the "multiplex advantage„
information at all frequencies is collected simultaneously
improving both speed and signal-to-noise ratio
"Jacquinot's Throughput Advantage„ - higher light levels
Better wavelength accuracy
Lower stray light sensitivity
More components are observable simultaneously
Kertész Károly: Folyamatos gázelemzés

16. Thermo 48C CO Analyzer (D.E.E.) GFC IR

17. NO+O3 → (1-n)·NO2+ n·NO2*+O2
chemiluminescence
Nitric oxide (NO) and ozone (O3) react to produce a characteristic luminescence with an intensity linearly proportional to the NO concentration.
NO+O3 → (1-n)·NO2+ n·NO2*+O2
IR light emission results when excited NO2 molecules decay to lower energy states.
NO2* → NO2+ hv
Nitrogen dioxide (NO2) must be first transformed into NO before it can be measured with chemiluminescent method.

18. CLD (Chemiluminescent Detector)
Principle: NO+O3→NO2*+O2
Chemiluminescence magic.mp4:

19. Thermo 42C NO-NO2-NOX Analyzer (D.E.E.) CLD
NO+O3→NO2*+O2
Converter
efficiency depends on temperature: molybdenum heated to approximately 325°C
consists of an insulated housing, heater, replaceable cartridge, and a type K thermocouple

20. FID - Flame Ionisation Detector
In a flame, oxygen and hydrogen are burned.
When in a hydrogen flame other molecules pass, these will burn also and increase the amount of ions.
The ions generated by the flame are attracted to the positive side of an electrical field in the detector cell.
The electrical current in the detector cell changes, this change is measured and has a direct correlation with the concentration.

21. FID- Flame Ionisation Detector
CH + O  CHO+ + e-
Measurable current : 10-12A
Without sample: 10-14A
Detector response~ measurable *107
Sensitivity 10-2 compared to TCD
Fid.swf

22. FID - Flame Ionization Detector
CH + O  CHO+ + e-

23. PMD (ParaMagnetic Detector)
Oxygen is attracted into a strong magnetic field. Most other gases are not.
A focused magnetic field is created. Any oxygen that is present will be attracted into the strongest part of the magnetic field.
Two nitrogen filled glass spheres are mounted on a rotating suspension within a magnetic field.
A mirror is mounted centrally on the suspension. Light is shone onto the mirror. The reflected light is directed onto a pair of photocells. Oxygen attracted into the magnetic field will displace the nitrogen filled spheres, causing the suspension to rotate. The photocells will detect the movement and generate a signal.
The signal generated by the photocells is passed to a feedback system. The feedback system will pass a current around a wire mounted on the suspension. This causes a motor effect, which will keep the suspension in its original position. The current measured flowing around the wire will be directly proportional to the concentration of oxygen within the gas mixture.

24. PMD (ParaMagnetic Detector)

25. PMD (ParaMagnetic Detector)
Cross contamination O2
+100
Nitrogen
-0.42
Air
+21 (száraz)
Chlorine
-0.13
CO2
-0.61
Hydrogen
-0.12
Argon
-0.58
Acetylene
-0.38
Ammonia
N2O
Ethane
-0.83 NO
+43.8
Methane
-0.37
NO2
+28.0

26. Alternative O2 measurement: Electrochemical method
1- air; 2- exhaust gas; 3- sensor; 4- electrolyte (zirconium dioxide);
5- exhaust side; 6-reference side; 7- span
Oxygen Sensor.avi:

27. Measuring Cell Testo 350 sample gas diffusion barrier Probe (anode)
–SO2 activated carbon, gold
- CO, platinum
electrolyte
Probe (cathode)
–platinum
Cross contamination
diffusion barrier CO
SO2 NO
NO2
H2S
100 65 30
-60
340 2
-100
200 5 15 18 -1 -5 20 7
-20
reference gas

28. Gas Chromatography
GC Columns.avi:

29. Chromatogram

30. Questions
What are the harmful components of exhaust gas? Why are they harmful?
Describe cross-stack measuring technique! (advantages, disadvantages)
Describe extractive measuring technique! (advantages, disadvantages)
What are the requirements of analyzers?
Describe NDIR! (working principle, detected components)
Describe CLD! (working principle, detected components)
Describe FID! (working principle, detected components)
Describe PMD! (working principle, detected components)

31. Thank you for your attention!
Viktória Barbara KOVÁCS
Build. D room 207B