Assessment of air quality impacts of natural gas and crude oil fuel at 600 MW steam power plant

Abstract

Effective utilization of fossil fuels for power generation depends to a great extent on the types of fuel and the capability of the steam generating equipment to control the emissions of air pollutants. The emitted pollutants are dispersed in the atmosphere resulting in deterioration of ambient air, thereby posing a threat to the environment. The work in this thesis involves estimation of the ground-level concentrations of sulphur dioxide, nitrogen oxides and suspended particulate matter due to the firing of different types of fuels namely, Natural Gas (NG), Light Arabian Crude (LAC) and Heavy Arabian Crude (HAC). Air pollution emissions were estimated from three stacks in the study area. Emissions of the above air contaminants are estimated based on the application of appropriate US EPA AP-42 emission factors and the use of the US EPA approved air quality dispersion modeling system (CALPUFF). The predicted measurements of the air pollutants have been compared with the current air quality standards of Presidency of Meteorology and Environment (PME Standards) of the Kingdom of Saudi Arabia in order to find suitable mitigation measures to prevent any adverse effects on environment. The results of the baseline ambient air quality data revealed that ambient air contaminant concentrations were generally very low with respect to the PME standards. The annual means of nitrogen oxides and sulphur dioxide were measured as 7 ppb and 2 ppb, respectively. Inhalable particulate (PM 10) concentrations were found to be high on occasion but they were generally less than 340 μg/m3 for a 24-hour average. Modeling Results for LAC showed that the maximum predicted one-hour and annual concentrations of NO2 were 200 μg/m3 and 5.7 μg/m3 correspondingly. The maximum 24-hour and annual predicted concentrations of particulate matter (PM10) were found to be 25 μg/m3 and 1.5 μg/m3. Sulfur dioxide results for one-hour and 24-hour were 12,939 μg/m3 and 912 μg/m 3 respectively which exceeded the PME Standards. Modeling predictions for HAC disclosed maximum one-hour and annual concentrations of NO2 to be 206 μg/m3 and 5.1 μg/m 3. Particulate maximum concentrations for 24-hour and annual were 112 μg/m3 and 6.4 μg/m3. For Sulfur dioxide the maximum predicted one-hour, 24-hour and annual concentrations divulged non-compliance with PME Standards. For Natural Gas and HAC, the maximum predicted one-hour and 24-hour average SO2 concentrations were 11,773 μg/m3 and 773 μg/m 3 respectively. Nitrogen oxides and particulate matter were predicted to be less than the PME Standards. Model results show that pollutants travelled mainly southeast and south direction of the emission source. Dispersion model results showed no exceedances for NO2, and PM10. However for SO2, the one-hour and 24-hour concentrations exceeded the PME standards for all three scenarios. Furthermore, the annual SO2 concentrations were also exceeded the standards for the HAC scenarios only. To achieve compliance with PME air quality standards for SO2, three types of mitigation measure were investigated: increasing stack height, reducing load and implementing control technologies. Model results indicate that the most viable solution to reduce SO2 concentrations is the implementation of control technologies.