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Measurement Differences between CEMS and Sorbent Traps

This study examined some of the factors that could contribute to differences between Method 30B Hg measurements and those that result from Hg CEMS.12 The following conclusions can be drawn: • When Hg is not controlled, the contribution of HgP is generally not enough to result in a significant difference between Method 30B and electronic Hg CEMS. • ACI and Br addition for Hg control will increase HgP. When Hg is controlled to MATS control levels, HgP that makes it past the PM control device may be sufficient to cause Method 30B to overestimate the gaseous Hg emissions by a significant degree, but typically not enough to impact whether or not a RATA is passed. • At sufficiently high Br levels, there is a potential for Br to contribute to differences between Method 30B and Hg CEMS that are not explained by HgP alone. One possible mechanism is the reaction of Br on the probe filter (or other surface) with gaseous Hg. This will be exacerbated if the probe or filter surfaces are reactive (ie., not adequately coated), if the filter condition has deteriorated or if material with reactive surface has accumulated on the filter. Others have also suggested that interference with the sample conversion system may contribute to this difference. For most Br addition rates expected under practical conditions, this potential effect is not expected to be significant. • The use of brominated activated carbon will impact the difference between Hg CEMS and sorbent traps due to formation of HgP as a direct and intended result of controlling Hg. The increased HgP that makes it past the PM control device will contribute to a difference between Hg CEMS and Method 30B. On the other hand, Br released from brominated activated carbon does not appear to impact gaseous mercury measurements to any significant degree. • This paper explored some key factors that might impact the difference between Hg CEMS

Revision Date:  4/30/2014

Tags:  562213 - Solid Waste Combustors and Incinerators , Andover Technology Partners, Sorbent Trap, Mercury Monitor, Continuous Emissions Monitor