Measurement of Sulfate Aerosols from Western Low-Rank-Coal-Fired Boilers with FGD: Results of Tests at Clay Boswell Unit 4.

摘要

The average particulate removal efficiency of the module tested was 99.1 percent, as calculated from the instack filter results. The impactor total mass loading results are in good agreement with those measured with the instack filters. The size dependent particulate removal by the scrubber may be characterized by the size at 50 percent collection efficiency, or cut point of the scrubber. The cut point is about 0.35 micrometer physical diameter or about 0.7 micrometer aerodynamic diameter, which is typical for a venturi with about 13 inches water volume pressure drop. The SO sub 2 concentrations measured with the continuous monitors are believed to be more accurate than those measured by the plant's instruments or by wet chemical methods. On the average, based on the instack filter results, 0.47 percent of the particulate mass loading at the inlet is sulfate. At the outlet, this fraction increases to 18 percent. The absolute amount of sulfate is roughly the same at inlet and outlet. The reason for this increase in relative sulfate concentratin can be seen from the impactor results. The sulfate fraction is greatest, at both the inlet and outlet, in the size range smaller than 0.3 micrometer. This size particle is collected relatively inefficiently by the scrubber, and so remains in the flue gas. A significant fraction of this small sulfate aerosol is probably sulfuric acid formed by condensation of SO sub 3 with water. The inlet temperature was about equal to the acid dew point, and the outlet temperature was well below the acid dew point. It should be noted that about 99 percent of the sulfur present in the flue gas stream at the inlet and about 96 percent at the outlet was in the form of SO sub 2 . Therefore, the potential amount of secondary sulfate aerosol was much greater than the primary sulfate aerosol present. (ERA citation 06:022008)