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Sampling Conditioning System for Extractive CEMS
Continuous Emission Monitoring SystemFrom Understanding to Implementation
CEMSSanjeev RaiPerma PureJan 18, 2017
AGENDA
• Different Application Different CEMS
• Importance of sampling system
• Moisture Removal System
• CEMS comparison Germany/China with • CEMS comparison Germany/China with India
• Common CEMS Installation Issues in India
• Maintenance of CEMS system in India
• Portable Conditioning System for Regulator
• Key Points for Regulators
Different Applications Require Different Approaches to CEMS
• What pollution control systems are now in place?
– FGD? Wet or dry injection?
– SCR? What is ammonia slip level?
– ESP or baghouse? What is particulate level?– ESP or baghouse? What is particulate level?
• What is the fuel source?
– How much sulfur content? (oil, coal)
– Water % by volume? (8-12% normal)
– Trash or other waste (biomass)?
• What is the measurement for?
– Regulation (CEMS)
– Process control
© Perma Pure, 2012 Page 5
Why Does Pollution Control Matter for CEMS?
1. Pollution control systems require BEFORE and AFTER measurements for process control and verification.
2. Low-level analytes require more accurate analyzers ANDmore accurate sample conditioning systems.
3. Key acid gases are highly water soluble.
– NO2 and SO2
– HCl and Hf
4. Catalysts and reagents can create unintended consequences with downstream reactions.
– E.g., Ammonia Injection
© Perma Pure, 2012 Page 7
SO2 Solubility in Water100100
9090
8080
7070
6060
5050
So
lub
ilit
y (
cc
SO
So
lub
ilit
y (
cc
SO
22/1
00
ml
H/1
00
ml
H22O
)O
)
© Perma Pure, 2012 Page 5
Temperature (Deg. C)Temperature (Deg. C)
5050
4040
3030
2020
1010
0000 1010 2020 3030 4040 5050 6060 7070 8080 9090 100100
SO
SO
22S
olu
bil
ity (
cc
SO
So
lub
ilit
y (
cc
SO
ANALYSER SYSTEM
Importance of Sampling System
• Gas Sample Conditioning Systems is an integral part of the Analyser System. Analyser is as good as it’s Sample.
• Tighter emission norms means more accurate measurement.
• It is legendary within the analyzer community that sampling causes 80% of the process analyser downtime( Clevett, K.J. causes 80% of the process analyser downtime( Clevett, K.J. 1986. Process Analyser Technology.New York: Wiley Science)
• Analyser reliability have improved substantially but the system reliability has not improved much because the sampling system are still the same
Gas Cooling Characteristic
• Gas cools down from 300 deg C to 30 Deg C in about 120 mm of bare tubing1
• Gas cools down from 300 deg C to 30 Deg C in about 500 mm of insulated tubing1C in about 500 mm of insulated tubing1
• Only way to avoid condensation is to have heated sample line which are properly terminated and do not have cold spots
• 1 Gross and Bundschuh
Moisture Removal Systems
Condensor
Condensers cool the gas below the dew point, and then remove the condensed liquid water from the gas stream. Water removal is performed automatically to prevent filling the condensate trap and flooding the sampling line.
Permeation Dryer
Permeation dryers are constructed using Nafion®, a material that selectively allows the mass transfer of water vapor from the sample gas through the tube membrane to dry purge gas flowing in an outer tube in the opposite direction.
About Nafion
• Nafion is a copolymer of Teflon and Sulfonic acid and is highly resistant to chemical attack while selectively permeating water through the membrane.
• Nafion removes water by absorption as water-of-hydration.
• Because this is a specific chemical reaction with water, the process is very selective and gases being dried or processed are usually entirely unaffected.
• The transfer of moisture is driven by the differential water vapor pressure between the membrane sides
Nafion Permeation Dryers Selectivity
Totally Retained by Nafion®Totally Retained by Nafion®
Atmospheric GasesAtmospheric Gases
HalogensHalogens
HydrocarbonsHydrocarbons
ArAr He HHe H22 NN22 OO22 OO33
BrBr22 ClCl22 FF22 II22Simple forms (alkanes)Simple forms (alkanes)
Inorganic AcidsInorganic Acids
Other OrganicsOther Organics
OxidesOxides
SulfurSulfur
Toxic GasesToxic Gases
HClHCl HF HNOHF HNO33 HH22SOSO44
Aromatics Esters EthersAromatics Esters Ethers
CO COCO CO22 SOSOXX NONOXX
COS HCOS H22S S MercaptansMercaptans
COClCOCl22 HCN HCN NOClNOCl
Typical Combustion Analytes
Nafion.swf
Nafion Dryer Construction
1. Tube and shell design2. Sample is passed through
Nafion tube3. Dry purge gas is passed
through Shellthrough Shell4. The dry Purge gas sweeps
away the moisture through Nafion tube.
5. The sample gas is dried while the purge gas is humidified
CEMS System Comparison with China/Germany and IndiaChina/Germany and India
CEMS Installation Germany
CEMS Installation Germany
Heated Sample line is connected to probe without any cold spot and it is installed right upto the cooler inlet
CEMS Installation China
CEMS Installation China
Pre SCR installation
• COMMON CEMS INSTALLATION ISSUES IN INDIAISSUES IN INDIA
CEMS Installation in India
HEATED PROBE BUT NO HEATED LINE BETWEEN PSHS AND PROBE
CEMS Installation in India
HEATED SAMPLE LINE HEATED PROBE BUT NEVER POWERED ON SINCE INSTALLATION ( 5 YEARS OLD INSTALLATION)
CEMS Installation in India
HEATED PROBE HEATED LINE BUT NOT PROPERLY TERMINATED
CEMS Installation in India
Non Heated Line Installed Between Probe to blowback
CEMS Installation in India
Condensate Pot Installed Between Blowback and Analyser
CEMS Installation in India
CONDENSATION IN THE SAMPLE LINE INSDE ANALYSER ABINET
CEMS Installation in India
No Heated Sample Line upto the cooler
CEMS Installation in India
Perisaltic pump was regularly failing so they iremoved pump and installed autodrain system
CEMS Installation in India
NO HEATED SAMPLE LINE BEFORE NAFION DRYER
Nafion System Installation
Portable Sample Conditioning System for Onsite Testing
Key Points for Regulator
How to ensure measurement accuracy
Measurement accuracy is more affected by sampling system than by analyzer
Moisture to be removed only in cooler or in Nafion Moisture to be removed only in cooler or in NafionDryer
All the component in the sampling system before moisture separation should be heated, no cold spot
No Condensate Pot/ moisture trap to be present in sampling system
Key Point for Regulator
CEMS is a system and not merely an instrument , if any component of system is not installed as per the best practice the accuracy will get compromised or system will fail much before the useful life.
As permitted levels of Sox and NOx are continually being reduced, it is even important to consider right conditioning technology to get representative sample.
During inspection it is important to look the complete system from probe to analyzer.