Industrial air monitoring – Stack gases
Monitoring emissions from industry
Gases released into the atmosphere from industrial processes (stack or flue gases) may contain many different pollutants. These need to be monitored in order to:
- Comply with environmental legislation.
- Provide data for emissions inventories.
- Calibrate continuous emission monitoring (CEM) systems.
- Provide data for environmental impact assessments.
- Assess process efficiency and process control.
- Assess the performance of pollution-control devices (abatement systems).
To ensure representative and accurate results, the procedures for analysis of stack gases generally follow standard test methods and protocols. These originate from a variety of regulators, government bodies and other trade organisations, and are usually pollutant-specific.
What Markes can offer
|Thermal desorption vs. solvent extraction || |
Use of pumped sampling onto glass tubes packed with charcoal, followed by carbon disulfide (CS2) extraction and gas chromatography (GC) analysis, was developed as an air monitoring method for volatile organic compounds (VOCs) in the 1970s.
It is still used today for monitoring of stack gases, but the laborious and hazardous sample preparation, together with its relatively low sensitivity, mean that it is increasingly being superseded by TD–GC methods.
See Application Note 046 for more information on thermal desorption and solvent extraction.
While most measurements of bulk organic vapours in stack gases are made using sensors (such as CEM systems), lower-level toxic organics are measured using collection onto sorbent tubes, for analysis by solvent extraction–GC or thermal desorption (TD)–GC. Key test methods for analysis of lower-level volatile organic compounds (VOCs) in stack gases include US EPA Methods 0030, 0031 and 5041A (in the USA) and EN 13649 (in Europe).
While originally restricted to solvent extraction, the 2014 revision of CEN/TS 13649 includes a description of a thermal desorption method, in response to a demand from industry.
Sampling stack gases
Sampling of stack gases requires a sampling train to remove particulates, acids or other corrosive chemicals, and so avoid contamination or damage to the monitoring equipment. With this done, the sample gas is collected onto sorbent tubes for analysis by TD–GC.
Two methods are commonly employed:
For a description of the benefits of thermal desorption for stack emissions testing, see Application Note 119.