Читать книгу Continuous Emission Monitoring - James A. Jahnke - Страница 21

CEM systems were originally required by regulatory agencies in the United States for monitoring the effectiveness of air pollution control equipment in removing pollutants from flue gases. As indicators of control equipment performance, the data could be used to track plant performance and target sources that were not meeting their emission limitations. Manual source tests would then be conducted on targeted sources to determine if, indeed, they were failing to be in compliance with emission limitations.

However, the extension of CEM data to direct enforcement applications has grown in both federal and state programs. By stating specifically in a rule or permit that a CEM system provides enforceable data that determines if an emission limit is being met or exceeded, the earlier link to control equipment performance is not as important. In addition, the promulgation of the “credible evidence” rule now allows the use of CEM system data in litigation.

CEM systems also provide the basis for the U.S. EPA acid rain control program mandated in the 1990 Clean Air Act Amendments. Here, CEM systems determine the “allowances,” the number of tons per year of SO₂ emissions that are traded between the electrical utilities. This successful regulatory program has led to significant SO₂ reductions in the United States within two years of its implementation. The over 2000 utility CEM systems installed to track allowances have contributed much to this success, providing an accurate database necessary to instill confidence in the trading market.

Another trading program is found in the Cross‐State Air Pollution Rule, where NO_x emissions are traded between electrical utilities and other sources in the northeastern states. These regulatory programs as well as economic forces led to an 89% decrease in SO₂ emissions and an 82% decrease in NO_x emissions from 1995 to 2017.

Although emission monitoring systems have been applied principally to satisfy such regulatory requirements, CEM system data can also be used proactively by plant and corporate management by providing a base of information on compliance status or for consideration in legal issues. As a result of both agency environmental programs and proactive source monitoring, the CEM database provides assurance to the public that emissions are being monitored to address environmental concerns.

However, the essential purpose of CEM systems should not be forgotten when providing for the timely submission of emissions reports. That purpose is to use CEM system data to control plant operations to meet emissions limitations (Figure 1‐3). The continuous record of emissions data enables plant operators and engineers to optimize plant performance and control equipment operation. On a continuous basis, emissions can then be maintained within regulated limits. In some cases, operating costs can be reduced and data can be gathered for plant design and maintenance information. In sum, the focus should not be on the quarterly emissions report, but rather, on how to use the data to improve operational efficiencies to minimize emissions.

Figure 1‐3 Industry uses of CEM system data.