Corrosion and Fouling Potential in Diesel Exhausts

The exhaust gases from five large diesel engines—1500 to 6400 kW (2000 to 8900 hp)—were sampled at three sites over a range of engine operating conditions using fuels with 0.05 percent to 0.8 percent sulfur. Measurements of SO₂, SO₃, CO, CO₂, H₂O, NO, NO_x, chlorides, acid dew point, peak rate temperature of acid deposition, particulate loading, particle sizing, particulate composition and smoke number were made to characterize the diesel exhaust. In the diesel exhaust, all of the fuel sulfur was converted to SO₂, SO₃, and other sulfur oxides. The SO₃ as a fraction of the total SO_x ranged from 2 percent to 8 percent varying inversely with fuel sulfur content. The average conversion to SO₃ was 3 percent. Acid dew point measurements were successfully obtained for a medium sulfur fuel (0.8 percent) and were correlated within 4°C with empirical predictions. Under typical diesel operating conditions the acid dew point varied from 112 to 117°C (234 to 242°F) for this fuel. Total particulate emissions varied directly with fuel sulfur content. Fifty percent or greater of the total particulate emissions were less than or equal to 0.3 μm in size. The fouling and corrosion potential of diesel exhaust gas can be approximated given the fuel analysis and engine operating conditions.