Air Dispersion Model
a power plant burns 150,000 tonnes (1 tonne = 1,000 kg) of coal each year. The coal has 2.5% sulfur content, and the air pollution control equipment removals approximately 94% of sulfur. Assume 10% of the sulfur content ends up in the ash. The remaining combustion products are discharged through an 80 m stack with a diameter of 3.0 m. The stack off gas temperature and velocity are 320 oC and 4 m/s, respectively, and the atmospheric conditions are 102 kPa and 25 oC. If the atmospheric conditions are slightly unstable (Class C) and the wind velocity at 10 m elevation is 3.5 m/s:
1. Plot the ground level concentration of sulfur dioxide as a function of distance from the stack and determine the maximum ground level concentration at both with and without air pollution control and the distance from the stack where the maximum concentration occurs.
2. With air pollution control equipment in place, plot the contours for a ground level concentration that is half and ¼ of the maximum value and indicate on your plot the location of the stack and the location of the point where the maximum ground level concentration would occur.
3. Compare your result with Ambient Air Quality Standard and comment it.
Note:
Sulfur dioxide:
Ambient Air Quality Standard = 0.03 ppm at annual average (80 µg/m3 or 8 x 10-5 g/m3 )
Lethal concentration: 400-500 ppm (0.11-0.14 g/m3 )