Читать книгу Continuous Emission Monitoring - James A. Jahnke - Страница 109

In conjunction with Pennsylvania Power and Light (PPL), the Lehigh University Energy Research Center developed a dilution ratio calculation system called “DRCalc^™” (Batug et al. 2004; Romero et al. 1999, 2002, 2005). After the dilution ratio is set initially, this system provides corrections for changes in the dilution air supply pressure, dilution air supply temperature, stack pressure and temperature, the sampled gas molecular weight, and the calibration gas molecular weight. Signals from temperature, pressure, and sensors, in addition to flue gas composition data, are sent to the DRCalc^™ unit, where proprietary software is used to continually recalculate the dilution ratio. This system has been patented (Batug et al. 2004) and was successfully applied at PPL facilities (Sale 2000a, b). It also incorporates an algorithm for changes in the dilution probe flue gas temperature, f(T).

For the EPM dilution probe, an apparatus has been designed (Baugham 1996, 1997) that uses a regulator to adjust the flow of dilution air to maintain a consistent dilution ratio to compensate for gas density changes. The advantage of this apparatus is that it can easily retrofitted into existing systems without having to make computational changes in the data acquisition system. Atmospheric and stack pressure and sample temperature are monitored to provide inputs into the system. Equation 3‐6 is used to adjust for sample temperature changes. The system can also provide for changes in gas density as the flue gas moisture or oxygen concentrations vary.

The Electric Power Research Institute developed an algorithm for in‐stack and external dilution system corrections in their “CEMS Analyzer Bias and Linearity Effects (CABLE) study” (Berry 2000). The study was conducted to improve the accuracy of CEM systems used in the acid rain program and provided recommendations for the implementation of a correction algorithm based on Equation 3‐9. In this algorithm, the temperature dependence, f(T), was expressed empirically as f when the study data were found not to follow the theoretical relation . Here, x, is determined for each individual dilution system. Step‐by‐step procedures and a logic diagram for implementation of the dilution ratio correction routine can be found in an EPRI report of the study (Berry 1999).