STUDY OF PRIMARY SULFATE EMISSIONS FROM A COAL-FIRED BOILER WITH FGD

A study was carried out to investigate the emissions of SO2 and primary sulfate materials (H2SO4 and inorganic particulate matter) from a boiler burning fossil fuel and using a wet-limestone scrubber for SO2 removal. Experiments were designed to assess the scrubbing efficiency for SO2 and sulfate, as well as the potential for scrubber liquor reentrainment. The boiler studied was an 820 MW cyclone-fired unit equipped with a wet, limestone scrubber, consisting of eight two-stage venturi-absorber modules designed to treat a flue gas flow rate of 2, 760, 000 acfm. The boiler fuel was a low-grade sub-bituminous coal with ash and sulfur contents of 25 and 5%, respectively. Multiple-sampling methods were employed concurrently on the inlet and outlet of a candidate absorber module to measure SO2, total water-soluble sulfate, and free H2SO4. Samples were collected during three field experiments from September 1977 through April 1978. The average SO2 scrubbing efficiency was 76% and was observed to decrease over the 5 day operation/maintenance cycle of the module. The total water-soluble sulfate input to the scrubber amounted to approximately 1% of the total sulfur oxides and was composed of a 5:1 ratio of H2SO4 to particulate sulfate. The total sulfate scrubbing efficiency, averaging about 29%, was invariant with respect to SO2 removal. The sulfate emissions measured in the scrubber exit gas consisted of about 85 % H2SO4 as a fine aerosol. Mass emissions of acid and particulate sulfate were calculated as 1730 Ib/hr and 305 Ib/hr, respectively. © 1979 Air and Waste Management Association.