Measuring H2S and SO2 in Flue Gas Applied Analytics Application Note No. AN-033
Application Summary Analytes: H2S (hydrogen sulfide), SO2 (sulfur dioxide) Detection Technology: OMA-300 Process Analyzer Process Stream: flue gas Typical Range: 0-300 ppm
Introduction Power plants and refineries are required to monitor and regulate the flue gas released from the burning of fossil fuels because this gas is released directly into the environment. A certified CEMS (Continuous Emissions Monitoring System) is enormously expensive to implement and maintain, so many operators choose to install affordable emissions analyzers and have the results audited yearly by a government agency. H2S and SO2 are two highly controlled pollutants which are commonly found in flue gas from hydrocarbon fuel combustion. H2S occurs naturally in many fossil fuel reserves as well as biogas, and oxidizes to SO2 in combustion. Legal requirements for monitoring the emissions of both chemicals are growing increasingly stringent with increasingly severe punitive measures for exceeding the required limits. As the world energy industry delves deeper into sour gas reserves, the emphasis on regulating these specific emissions is bound to grow. The OMA system provides fast response measurement of H2S and SO2 in the flue gas stream for tight emissions control. Providing excellent detection limits in a solid state package, the OMA is a highly practical solution for a facility that needs reliable emissions monitoring but lacks an astronomical budget for analyzers and maintenance.
OMA Benefits »» Measures sulfur compound concentration using solid state, consumable-free technology »» Close-coupled sample conditioner provides fast response with easier maintenance than cross-stack »» Scalable measurement allows later addition of analytes and modified concentration ranges »» Decades of field-proven performance in demanding flue gas applications
APPLIED A N A L Y T I C S
TM
[1]
AN-033: Measuring H2S and SO2 in Flue Gas
absorbance (AU)
Measuring H2S and SO2 in Flue Gas SO2 20 ppm
Applied Analytics Application Note No. AN-033
SO2 15 ppm SO2 10 ppm
H2S and SO2 Absorbance Curves
SO2 5 ppm
Any single photodiode measurement is vulnerable to noise, signal saturation, or unexpected interference. This susceptibility to H2S 20 ppm error makes a lone photodiode data point an unreliable indicator of one chemical’s absorbance. H2S 15 ppm
As accepted in the lab community for decades, the best way to neutralize H2S 10 ppm this type of error is to use collateral data in the form of ‘confirmation wavelengths,’ i.e. many data points at many wavelengths instead of a single wavelength: H2S 5 ppm
0.2
absorbance (AU)
0.16
0.12
0.08
0.04 SO2 20 ppm 0 210
220
230
240
250
SO2 15 ppm 280 290 wavelength (nm) SO2 10 ppm SO2 5 ppm 260
270
SO2 20 ppm
H2S 20 ppm
SO2 15 ppm
H2S 15 ppm
SO2 10 ppm
H2S 10 ppm
SO2 5 ppm
H2S 5 ppm
300
310
320
H2S 20 ppm 0.2
H2S 15 ppm
The figures above demonstrates how the OMA ‘learns’ the absorbance curve structure of each analyte through a full-spectrum H2S 10 ppm calibration on a standard concentration mixture. Using the measurements from each photodiode (each circle in the curve 5 ppm 0.16 represents a single photodiode providing a data H2S point at an integer wavelength), the OMA knows the expected relation of each point in the absorbance curve and automatically eradicates erroneous results.
0.2
absorbance (AU)
This full-spectrum measurement also allows the OMA to easily de-convolute the overlapping absorbance curves of H2S and 0.12 SO2 to accurately isolate the absorbance of each. This capability is unique to spectrophotometers and ensures that there will be no false positive sulfur compound readings, while also preventing cross-interference between the two components. 0.16 0.08
0.12 0.04 0.08
[2]
AN-033: Measuring H2S and SO2 in Flue Gas
0 210
220
230
240
250
260
270
280
290
300
310
320
Measuring H2S and SO2 in Flue Gas Applied Analytics Application Note No. AN-033
Close-Coupled Sample Conditioner Design The OMA flue gas analyzer is paired with a close-coupled sample conditioner which is mounted directly on the stack via a sintered metal probe which extracts the sample. This design has extremely fast response due to the minimal sample route, yet is far easier to install and maintain than a cross-stack method (no issues with optical alignment or span gas validation).
Example system: close-coupled SCS for measuring H2S in flue gas.
Schematic: close-coupled mounting.
Example Installation: close-coupled OMA system analyzing flue gas at a manufacturing site. [3]
AN-033: Measuring H2S and SO2 in Flue Gas
Measuring H2S and SO2 in Flue Gas Applied Analytics Application Note No. AN-033
The specifications below represent performance of the OMA-300 Process Analyzer in a typical flue gas application. For technical details about the OMA-300 Process Analyzer, see the data sheet: http://www.a-a-inc.com/documents/AA_DS001A_OMA300.pdf
Subject to modifications. Specified product characteristics and technical data do not serve as guarantee declarations.
All performance specifications are subject to the assumption that the sample conditioning system and unit installation are approved by Applied Analytics. For any other arrangement, please inquire directly with Sales. Application Data Performance Specifications Custom measurement ranges available; example ranges below.
Accuracy
H2S
0-10 ppm (@10 bar): ±0.1 ppm 0-10 ppm (@1 bar): ±1 ppm 0-100 ppm: ±1% full scale or 1 ppm* 0-10,000 ppm: ±1% full scale
SO2
0-100 ppm: ±1% full scale or 1 ppm* 0-10,000 ppm: ±1% full scale *Whichever is larger.
[4]
AN-033: Measuring H2S and SO2 in Flue Gas
Measuring H2S and SO2 in Flue Gas Applied Analytics Application Note No. AN-033
Revised 17 September 2013
Further Reading Subject
Location
OMA-300 CEM System Data sheet
http://www.a-a-inc.com/documents/AA_DS001D_OMA300CEM.pdf
Advantage of Collateral Data Technical Note
http://www.a-a-inc.com/documents/AA_TN-202_CollateralData.pdf
Close-Coupled Sample Conditioner Data Sheet
http://www.a-a-inc.com/documents/AA_DS604A_CloseCoupledSCS.pdf
APPLIED A N A L Y T I C S
TM
is a registered trademark of Applied Analytics Group BV.
Headquarters + Manufacturing Applied Analytics, Inc. Burlington, MA |
[email protected]
Asia Pacific Sales Applied Analytics Asia Pte. Ltd. Singapore |
[email protected]
North America Sales Applied Analytics North America, Ltd. Houston, TX |
[email protected]
Middle East Sales Applied Analytics Middle East (FZE) Sharjah, UAE |
[email protected]
Europe Sales Applied Analytics Europe, SpA Milan, Italy |
[email protected]
Brazil Sales Applied Analytics do Brasil Rio de Janeiro, Brazil |
[email protected]
| www.a-a-inc.com
India Sales Applied Analytics (India) Pte. Ltd. Mumbai, India |
[email protected]
© 2013 Applied Analytics Group BV. Products or references stated may be trademarks or registered trademarks of their respective owners. All rights reserved. We reserve the right to make technical changes or modify this document without prior notice. Regarding purchase orders, agreed-upon details shall prevail.
[5]
AN-033: Measuring H2S and SO2 in Flue Gas
