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Show 11 The dry scrubbing and baghouse processes also performed well as an integral part of the LIDS system. The modest S02 capture achieved in the dry scrubber is to be expected because, as the total S02 removal of the integrated system improves (including significant baghouse S02 capture), the solids returned to the dry scrubber in the slurry become less reactive (the useful CalS entering the dry scrubber decreases). Based on qualitative observations, the dry scrubber and baghouse can be operated at an approach to saturation temperature in the range of 10°F without operability problems. The dry scrubber was operated without any excessive buildup and the hopper ash was easily removed. The baghouse solids felt dry, flowed freely, and were easily transported to the slurry preparation system. AIR TOXICS Title III of the Clean Air Act of 1990 mandated that the Environmental Protection Agency (EPA) evaluate emissions of 189 air toxics from the electric power plants. Since then, researchers have studied the trace emissions of heavy metals (including mercury), acid gases, and organics from power plants; their transport and fate in the environment; and health impacts. Currently, how these results will impact potential regulations is uncertain. Because air toxies regulation is somewhat of awildcard, it was important to evaluate the B&WLEBS against potential airtoxics areas ofconcem. The following is a summary of where potential air toxies regulations may be headed and how the B&W LIDS system stacks up against them. Mercury Mercury emissions from coal-fired power plants are a matter of intense debate. It seems likely that mercury emissions will be regulated in some manner in the future due to its potential to bioaccumulate in the food chain. Since mercury is a likely target for regulation, screening tests of mercury emissions from the LIDS system were performed by Frontier Geosciences, Inc., to characterize the process in terms of its mercury capture capabilities. The Frontier Geosciences measurement method has been documented in many technical papers; details of the method can be referenced in these papersJ4] Measurements were made at the dry scrubber inlet, dry scrubber outlet, and baghouse outlet during the LIDS feasibility demonstration discussed above. LIDS overall mercury removal results are presented in the Table 1. Values recorded for total mercury (Hg) clearly indicate a repeated pattern of mercury reduction across both the dry scrubber and baghouse. Total mercury removal averaged 97% across the LIDS system (Figure 8). |
