Northampton Generating Co. LP (NGC) is nearing an approval from the Pennsylvania Department of Environmental Protection for a permit revision for its waste-coal-fired power plant in Northampton County related to the variable lead content in its coal supply.
The DEP said in a notice of its intent to approve the revision, published in the April 4 Pennsylvania Bulletin, that the revision of the permit limit for lead (Pb) emissions is to address the variability of Pb content in fuel inherent with the multiple coal refuses piles that the plant currently uses in its circulating fluidized bed (CFB) boiler. The company has sampled and tested approximately 21 refuse coal piles for lead content in order to determine the base line for Pb. The results were varied, ranging from 4.3 ppms to 140 ppms. NGC has used 140 ppms (highest Pb found in the sample) in re-developing the lead emissions limit.
Based on these sampling and findings the company has requested the department to revise the Pb limit, when burning supplemental Tire Derived Fuel (TDF), from 0.0027 pound per hour to 0.0588 pound per hour. A Health Risk Assessment Model was provided to justify the revised lead emissions limit. No other operational changes were proposed by the company.
The department’s Central Office Air Quality staff reviewed the Health Risk Assessment results and concluded that for the increased Pb emissions (0.0588 lb/hr = 0.00742 g/sec), the cancer risks for the baseline and TDF scenarios is 1.22 E-06. The non-cancer risks for the baseline and TDF scenarios have gone up slightly to 0.14 and 0.19, respectively, which are still below the acceptable level of 0.25.
Based on 8,760 hour per year operation and maximum of 140 ppms of lead content in coal refuse, the potential Pb emissions from the boiler are 0.258 ton/year. No other emissions changes are expected due to this change from the facility.