Parametric Modeling of Exhaust Gas Emission From Natural Gas Fired Gas Turbines

Abstract

Increased focus on air pollution from gas turbines in the Norwegian sector of the North Sea has resulted in taxes on CO2. Statements made by the Norwegian authorities imply regulations and/or taxes on NOx emissions in the near future. The existing CO2 tax of NOK 0.82/Sm3 (US Dollars 0.12/Sm3) and possible future tax on NOx are analyzed mainly with respect to operating and maintenance costs for the gas turbine. Depending on actual tax levels, the machine should be operated on full load/optimum thermal efficiency or part load to reduce specific exhaust emissions. Based on field measurements, exhaust emissions (CO2, CO, NOx, N20, UHC, etc.) are established with respect to load and gas turbine performance, including performance degradation. Different NOx emission correlations are analyzed based on test results, and a proposed prediction model presented. The impact of machinery performance degradation on emission levels is particularly analyzed. Good agreement is achieved between measured and predicted NOx emissions from the proposed correlation. To achieve continuous exhaust emission control, the proposed NOx model is implemented to the on-line condition monitoring system on the Sleipner A platform, rather than introducing sensitive emission sensors in the exhaust gas stack. The on-line condition monitoring system forms an important tool in detecting machinery condition/degradation and air pollution, and achieving optimum energy conservation.

Thermodynamic, Environmental and Economic Assessment of Exhaust Gas Recirculation for NOx Reduction in Gas Turbine Based Compressor Station

“…In general, the main factors controlling NO, emissions from conventional combustors are the homogeneity of the combustion process, temperature, equivalence ratio, the residence time in the primary-zone, and the liner-wall quenching characteristics. There are some Predictive Emission Monitoring (PEM) models that incorporate all of these parameters, or, equivalently, utilize fundamental combustion mechanisms, and can be applied to any given machine [7,8]. In the present study, a one-dimensional model previously developed for PEM [8] is utilized to thermodynamically assess and quantify NO, reduction through EGR in a typical stationary natural gas fueled turbine system.…”

One-Dimensional Model to Quantify NOx Reduction in Gas Turbines Using EGR

“…In general, the main factors controlling NOX emissions from conventional combustors are the homogeneity of the combustion process, temperature, equivalence ratio, the residence time of the primary-zone, and the liner-wall quenching characteristics. There are some PEM models that incorporate all these parameters, or, equivalently, utilize fundamental combustion mechanisms, and can be applied to any given machine [4,5]. In the present study, a one dimensional model previously developed for PEM in [5] is utilized to thermodynamically assess and quantify NOx reduction in a typical stationary natural gas turbine system.…”

One-Dimensional Predictive Emission Monitoring Model for Gas Turbine Combustors

“…Several empirically developed correlations to predict NO x emissions are listed in [13] with combustor pressure, overall fuel-air ratio, combustor inlet temperature, combustor air flow rate and residence time as input variables. Sullivan used these parameters to create a similar, improved correlation [13,14] which also included the effects of inlet humidity, vitiated air and emissions from a direct fired preheater. Other correlations have been developed by Bakken and Skogly [14], Rokke [15], and Melte et al [16] for emissions from gas fired turbines in offshore production platforms.…”

“…Sullivan used these parameters to create a similar, improved correlation [13,14] which also included the effects of inlet humidity, vitiated air and emissions from a direct fired preheater. Other correlations have been developed by Bakken and Skogly [14], Rokke [15], and Melte et al [16] for emissions from gas fired turbines in offshore production platforms. These parameters include fuel-air ratio, compressor pressure ratio, and compressor discharge pressure, combustor discharge temperature and air flow rate.…”