Startup and Shutdown Air Permit Limit Development Framework for Combustion Sources Monitored by Continuous Emission Monitoring Systems

摘要

This paper is meant to help the air quality industry work towards establishing standardized guidelines to develop startup (SU) and shutdown (SD) air permit limits for large stationary combustion units including boilers and combustion turbines equipped with Continuous Emission Monitoring Systems (CEMS). The concept of monitoring emissions during all operating times and comparing emissions data to appropriate emission limits during startup, shutdown and malfunction (SSM) events are at the center of this development process. Since emissions data during SU/SD events are highly variable for certain monitored parameters including oxides of nitrogen (NO_x) and carbon monoxide (CO), establishing SU/SD limits that both government agencies and the energy industry find satisfactory can be a challenge. This paper discusses an objective framework for developing SU/SD limits that can be applied to any combustion unit equipped with CEMS. The framework is comprehensive and uses a practical data-driven approach to develop optimal unit specific SU/SD duration and emission limits based on CEMS data. The framework has both qualitative and quantitative elements. The qualitative aspects involve gathering preliminary data to identify applicable unit and facility specific requirements, stakeholder participation, regulatory engagements and permitting, as well as data acquisition and handling system (DAHS) programming efforts. The quantitative portion focuses on the development of numerical duration and mass per SU/SD event emission limits using objective statistical methods including the upper prediction bound and linear regression, while avoiding more subjective based limit development processes as well as limits based on emissions concentrations and rates. Our data analysis process uses open source statistical programming packages to develop optimal unit specific duration and mass per SU/SD event emission limits from minute level CEMS data. The paper also discusses lessons-learned from successfully applying these standard guidelines in developing SU/SD limits for inclusion within multiple air permits.