Public Health Consultation

Appendix C: History of generating station and pollution control measures

The Greenidge power plant was built in the 1930s for the New York State Electric and Gas Corporation (NYSEG), and was bought in 1999 by the AES Corporation. The facility's first generator, Unit 1, went into service in 1937. Additional generating units were built in 1939 (Unit 2), 1950 (Unit 3), and 1953 (Unit 4) to meet growing electricity demands in the area. In 1985, Units 1 and 2 were retired from service and their respective boilers and turbines removed from the premises (DOE, 2004).

The remaining generating units, Units 3 and 4, have a combined generating output of 161 megawatts (MW). Unit 3 consists of two dry-bottom, wall-fired, pulverized coal boilers (Boilers 4 and 5) which exhaust through a common stack. Unit 4 consists of one dry bottom, tangentially fired, pulverized coal boiler (boiler 6) which exhausts to another stack. Both Units 3 and 4 have a stack height of 250 feet, although the stack for Unit 3 begins 23 feet above ground level. Water for cooling is drawn from Seneca Lake, and returned via a discharge channel and the Keuka Outlet. The coal handling system encompasses coal delivery, transfer to hoppers, storage, crushing, and conveyer belt transportation to the boilers (DOE, 2004). All emissions from the plant are reported to NYS DEC as part of AES Greenidge's Titles IV and V permits (NYS DEC, n.d.).

All three boilers burn eastern bituminous pulverized coal as their primary fuel. Boiler 4 is permitted to burn up to 30% untreated wood and wood waste from furniture manufacturing, and #2 fuel oil, diesel oil, waste oil, and natural gas on an occasional or as-needed basis. Typical content for coal burned at the facility is as follows: 5.8-7.6% moisture content, 67.9-72.2% carbon, 3.9-4.8% hydrogen, 1.4-1.6% nitrogen, 0.9-2.9% sulfur, 7.9-13.5% ash, 4.7-5.0% oxygen and 0.07-0.10% chlorine (DOE, 2004). The Greenidge plant also began a biomass cofiring program in October 1994 (IEA, n.d.). Biomass co-firing involves replacing a portion of the coal that normally would have been used with biomass fuels such as wood waste either before or during the combustion process (DOE, 2006). Because biomass fuels have very little sulfur, SO2 emissions are reduced proportionally to the amount of coal not used. NOx emissions may also be somewhat reduced by the process.

Unit 3 and 4 are equipped with electrostatic precipitators to remove particulate matter from flue gas, thereby reducing emission of particulate matter to air. Until recently, sulfur dioxide (SO2) from all three boilers has been controlled primarily by limiting the sulfur content of the coal fuel. Nitrogen oxides (NOx) emissions have been controlled until recently by using an overfire air reburn system (air injected above the main burn zone) to reduce the production of NOx in Unit 3; while Unit 4 had relied on two technologies to limit NOx emissions. First, a gas reburn system which supplied both natural gas and overfire air, limited the production of NOx further than overfire air alone. Second, an advanced gas reburn system was installed as part of a 1996 demonstration project to reduce NOx emissions post-combustion. This process involved the injection of a nitrogen agent, in this case, ammonia (NH3), to convert NOx created in the fuel combustion process to nitrogen and oxygen in addition to gas reburn (DOE, 2004; Zamansky and Folsom, 1997). However, this system was able to achieve only modest NOx reductions and has been discontinued. Neither Unit 3 nor 4 were equipped with scrubbers.

Latest pollutant control modifications

In January 2005, then New York State Governor George Pataki and Attorney General Eliot Spitzer announced two landmark agreements designed to substantially reduce emissions from six-upstate New York coal-fired electric generating plants. Overall goals are the reduction of NOx emissions by 70% and SO2 emissions by 90%, as well as the reduction of particulate matter for the protection of public health and the environment (NYS Office of the Attorney General (OAG), 2005a).

Included in these agreements, the operators of AES Greenidge facility in the Town of Torrey, NY agreed that Unit 3 would meet Best Available Control Technology (BACT) standards, re-power (with cleaner technologies), or shut down by 2009. In addition, a multi-pollutant control project (MCP project) was begun on Unit 4 during a scheduled outage at the plant in September 2006. If the objectives of the MCP can not be met, Unit 4 must also meet BACT standards, repower, or shut down by December 2009 (NYS OAG, 2005b).

The MPC project, part of the agreement between AES and NYS, will demonstrate control technologies to reduce emissions of NOx, SO2, mercury (Hg), particulate matter (PM 2.5 and PM10), and acidic gases such as hydrochloric acid (HCl), sulfur trioxide (SO3), and hydrogen fluorides (HF) at the AES Greenidge plant. Specifically, the new demonstration technologies will include: a circulating dry scrubber (CDS) with an activated carbon injection system to capture 95% of SO2 emissions, up to 90% Hg, and 95% of acidic gases; a single-bed selective catalytic reduction (SCR) system (using urea injected into the boiler, which is converted to ammonia for use in the catalyst) in combination with low- NOx combustion technology for NOx control and; a selective non-catalytic reduction (SNCR) with urea injection and associated storage tank for additional NOx control.

According to preliminary project and quarterly reports major construction on Unit 4 was completed in early 2007 (Connell, 2007a; Connell 2007b). Currently the Unit is undergoing a 20 month period of operation during which the performance of the system will be evaluated. The MCP project is part of a demonstration project approved and partially funded by the Department of Energy (DOE) (DOE, n.d.).

References (Appendix C)