Transcript
Cemtek Users Group 9 28 2016
New Developments in TDLAS NH3 Monitoring Presented by John Pisano CEMTEK Environmental UCR (University of California at Riverside) Unisearch Associates Inc
Cemtek Users Group 9 28 2016
Outline • • • •
What is a tunable diode laser (TDL) The theory General overview of a TDL system Navigating LasIRView software – General overview – Accessing and Parsing data
Cemtek Users Group 9 28 2016
What are Tunable Diode Lasers (TDL)? • Lasers made from Ga, As, Sb, P • Telecommunications grade – Long life – Rugged construction – Commercially available at low cost
• Emits in near infrared region when power is applied.
Optical Light Source based Gas Analyzers Cemtek Users Group 9 28 2016
Tunable Diode Lasers (TDL) ? UNISEARCH uses
TO-CAN PACKAGE
OR
Analyzer must be located at the measurement location
14-PIN BUTTERFLY PACKAGE
Analyzer can be located far away from the measurement location
Cemtek Users Group 9 28 2016
Wavelength Scale CO CO2 NH3
H2O
NO2 SO2 NO SO3
O2
Near Infrared 1500 nm NIR TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY
Visible
700 nm
Near UV 350 nm
VIS-UV DIFFERENTIAL OPTICAL ABSORPTION SPECTROSCOPY
Cemtek Users Group 9 28 2016
How do Tunable Diode Lasers (TDL) Operate? • Laser center wavelength depends on material composition • Wavelength can vary based on laser temperature and current – Current: fine tune changes in wavelength (fast) – Temperature: coarse tune changes in wavelength (slow)
• Laser current can be ramped rapidly – Permits the ability to rapidly scan over entire absorption spectrum
• Scans the entire absorption feature – Removes interference from dust via continuous power level monitoring
Cemtek Users Group 9 28 2016
Determination of Concentration • Beer’s Law
(‐Ϭ C L )
• I=Io e
– – – – –
I = Energy Transmitted I0 = Energy Emitted σ = molecular cross‐section, C = Concentration [ppm] L = Pathlength [m]
• All parameters known except for I, I0, and C. – σ unique for each molecule. Experimentally determined. – I and I0 measured
• Ideal Gas Law for temperature and pressure correction
Cemtek Users Group 9 28 2016
Wavelength Scan (5 kHz) Radiation Power
Absorption region Side wavelengths, without absorption
Emission Wavelength
Cemtek Users Group 9 28 2016
NIR Light Absorption When no gas present… Io
When gas present… I Absorbed intensity, I = Io - I
Cemtek Users Group 9 28 2016
Species Specificity with TDLs • Comes from unique molecular structure of monitored specifies • Each species has a group of wavelengths at which light is readily absorbed. – Ammonia: 1514 nm – HCl: ~1800 nm
• Certain absorption peaks selected – Minimizes/eliminates interference due to other compounds
Cemtek Users Group 9 28 2016
Detection Limits • Factor of both path length and path measurement time • Typical detection limit for ammonia:0.5 ppmv • Path Length – Longer path lengths yield higher absorption, increased sensitivity and lower detection limit. – Thus longer path lengths result in better delectability of low concentrations.
Cemtek Users Group 9 28 2016
Detection Limits • Measurement Time – Scales approximately to the square root of the measurement time. – Example: Increasing the time from 1‐second to 1‐ min enhances the detection limit approximately seven fold.
Cemtek Users Group 9 28 2016 Multi-channel capability – single analyzer to measure multiple locations. They can be extractive, open path, in-situ stack or duct or any combination. Channels are independent with zero cross-talk between them. PORTABLE MULTI-CHANNEL ANALYZER GAS IN GAS OUT
1 - 150 m
1 2
EXTRACTIVE
1 - 75 m
10 - 500 m
OPEN PATH
3
1 - 15 m
1 - 500m
STACK/DUCT
Cemtek Users Group 9 28 2016 TRANSMITTER OPTICS
When using non fiber-coupled light source, need to locate the gas analyzer at the measurement location
RECEIVER OPTICS
Cemtek Users Group 9 28 2016
TRANSMITTER OPTICS
GAS ANALYZER •Locate Laserthe temperature have toat bethe o measurement stabilized tolocation within +/-0.01 C • Laser temperature can be o o anywhere between 5 C to 45 C
RECEIVER OPTICS
Cemtek Users Group 9 28 2016 TRANSMITTER OPTICS
Purge Air
RECEIVER OPTICS
Purge Air
When using fiber-coupled light source, the analyzer can be located inside the a control room
Armored Fiber Cable
Coax Cable
Cemtek Users Group 9 28 2016 NH3 Slip Measurements in Coal-fired Power Plants
Coal-fired Power Plants Application - Ammonia slip measurement
Cemtek Users Group 9 28 2016 NH3 slip measurement
Cemtek Users Group 9 28 2016
NH3 slip measurement
Cemtek Users Group 9 28 2016
NOX reduction in an SCR Coal-fired Boiler NH3/ Urea
NOX
NOX
H2 O NH3
NOX
Dirty Gas
N2
NOX
NOX NH3
NOX
DeNOx Catalyst
Cleaner Gas
H2 O
N2 NOX
NOX
H2 O NH3 N2
4NO + 4NH3 2NO2 + 4NH3
4N2 + 6H2O 3N2 + 6H2O
Cemtek Users Group 9 28 2016
NOX reduction in an SCR Coal‐fired Boiler NH NH33/ Urea NH3 NOX
NOX
H 2O
NH3
NOX
NH3 N2
NH3
Dirty Gas
NOX
NOX NH3
NOX
DeNOx Catalyst
N2
NH3 NOX
NOX NH3
4NO + 4NH3 2NO2 + 4NH3
4N2 + 6H2O 3N2 + 6H2O
NH3 Slip
H 2O
H 2O
NH3 N2
Cemtek Users Group 9 28 2016
In-situ NH3 measurement (Lowest Detection Limit ~0.5 ppm for a 5 meter duct diameter)
Cemtek Users Group 9 28 2016
NOx Reduction in Power Plants
Fiber cable
Coax cable
UNDER VERY HIGH DUST CONDITIONS… In-situ laser beam may not pass through the duct!!!
Cemtek Users Group 9 28 2016 PIMS (Pseudo In-situ Measurement System)
Cemtek Users Group 9 28 2016
Purge Control cable
Cemtek Users Group 9 28 2016
Optics
Heated & temperature-stabilized gas cell
Optics
Fiber IN Coax OUT
V2
Pump TC
V1 PR
Filtered gas Extraction and optics enclosure
Purging gas
DUCT
Sampling tube
Control Line IN
Cemtek Users Group 9 28 2016
Sampling tube
DUCT
PURGE CONTROL LINE
Analyzer located in Control Room
COAX
FIBER
Cemtek Users Group 9 28 2016 NH3 Measurement in Power Plants with High Dust Loading PIMS installed in Duct
Analyzer in Control Room
Cemtek Users Group 9 28 2016
PIMS (Pseudo In-situ Measurement System) (China, USA, Canada, Europe, International patent pending)
Cemtek Users Group 9 28 2016
EPRI PIMS Measurement at First Energy coal-fired Power Plant in US
PIMS
Cemtek Users Group 9 28 2016
5 4 3 2
1
Multi-point PIMS to measure NH3 inhomogeniety
Cemtek Users Group 9 28 2016
Cemtek Users Group 9 28 2016
10 8 ppm 6
4
2
0
Cemtek Users Group 9 28 2016
Unisearch gas analyzer do not require field calibration. Audit Modules containing permanently sealed gas cells are available to check the validity of the measurements. Therefore, compressed gas cylinders are not required to check the performance or validity of the analyzer.
Cemtek Users Group 9 28 2016
Fiber cable
Audit module Coax cable
Analyzer Offline Audit
Cemtek Users Group 9 28 2016
Fiber cable
Audit module Fiber cable Coax cable
Analyzer Inline Audit
Cemtek Users Group 9 28 2016
Audit module
Fiber cable
GAS IN GAS OUT
Gas in Fiber cable Coax cable
Analyzer Inline Audit with Cylinder Gas
Cemtek Users Group 9 28 2016
Data logging: Internal compact flash card (4 GB) – can store ~5 years of data Analog: 4-20 mA outputs (for gas level and signal power) Digital: RS232 (ASCII), Ethernet, Modbus (TCP/IP)
Alarms: 6 dry-contact relays (5 configurable by user) Examples: • Analyzer main power (fixed) • Software operation • Gas level alarm (low and high) • Instrument fault alarm
