OCR Text |
Show 20 A16SE738.T The SNCR system demonstrated average NOx reduction levels of roughly 30 % from a low excess oxygen baseline of 1.1 IblMMBtu. From a more representative baseline of 1.3 Ib/MMBtu, a 30% reduction would provide a targeted level of NO x emissions ofO.9Ib/MMBtu. NFr has predicted a chemical usage of 206 gph to meet this reduction target. This is consistent with pump rates experienced during Period 8, extrapolated to full load conditions. The capital costs for a commercial system on this unit has been estimated at $2,070,000. This is equivalent to 15$/kW. Included is the equipment, installation, engineering and design, as well as the licensing fee. The boiler heat rate penalties resulting from the vaporization of the aqueous solution decrease the boiler efficiency by approximately 0.5 %. It was assumed that multi-level injection would be used for the commercial installation, with each injector discharging 1 gpm/injector on the lower elevation and 0.6 gpm/injector on the upper elevation, resulting in a total liquid flow of 15 gpm. A summary of the cost estimates for the installed SNCR system is presented in Table 3. The analyses are based on the above assumptions, a plant capacity factor of 60 %, and an annual capital recovery rate of 14.67% was used. Based on this analysis, the total SNCR annualized cost would be $1.4 million per year, or $937 per ton NOx removed. Of this total, 22 % is capital investment, 59 % is reagent cost, and the remaining 19% represents maintenance, power requirements, and boiler efficiency penalties. RECOMMENDATIONS Based on the experiences at Atlantic Electric's B.L. England Station Unit 1, several issues need to be addressed relative to the design, operation and maintenance of a commercial SNCR system. These issues include: 1. Mixing the chemical and water at the injection elevation to increase the response time of the injection system and help reduce potential ammonia slip excursions during transient operating periods. 2. Explore localized variability in O2 on NOx, variables other than O2 and load, variables that might have transient impacts on NOx, and methods of tightening control dynamics in order to reduce variability in baseline NOx- 3. Identify tradeoffs between CO and NOx in determining acceptable permit limits for each. 4. Evaluate cost impacts of operation at low excess air to determine upper and lower limits on excess O2• |