In September 2010, the EPA announced the final amendments to the National Emissions Standard for Hazardous Air Pollutants (NESHAP) for the Portland cement industry, also known as the Portland cement maximum achievable control technology (MACT). The EPA's rulemaking includes some important implications for cement manufacturers and other sources that may be subject to revised MACT rulemaking in the future.

 

Monitoring requirements
The cement industry faces the challenge of complying with the numerical emission limits of the final Portland cement MACT. However, the emission
limits themselves may not be the most challenging part of the rule when compared with the monitoring requirements. While the 30-day averaging period that is utilised by the EPA to some extent offsets the stringency of the numerical limits, a plethora of monitoring devices are required by the rule. Some of these devices have not yet been demonstrated in continuous use on cement kilns in the US. For example, the EPA requires mercury continuous emissions monitoring systems (CEMS) on kilns.

 

Continuous THC and HCl monitoring systems
The EPA's performance specifications for THC CEMS dictate that a gas sample is extracted from the source through a heated sample line and heated filter to an analyser. Results are reported as volume concentration equivalents of propane. The performance specification for HCl describes the
criteria that the CEMS must meet to be considered valid for EPA compliance and/or other regulatory applications. Each HCl CEMS must meet the criteria for accuracy, stability, and instrumental response laid out in this document, as well as the installation requirements.

 

By providing a comprehensive monitoring package using an AAS mercury CEMS combined with an in situ THC and HCl analyser, cement plants can meet or exceed their compliance requirements at the lowest cost possible.

 

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