Keyspan Energy - Ravenswood Cogeneration Facility Article X Application
Total Page：16
File Type：pdf, Size：1020Kb
KeySpan Energy - Ravenswood Cogeneration Facility Article X Application 8.1 Introduction A thorough understanding of several key elements is essential in anticipating the potential effects of a proposed power plant. Arguably, the most important of these factors is the pattern and magnitude of the cooling water flow because cooling water withdrawal, total flow, and intake velocity play a fundamental role in determining the number of organisms lost through entrainment and impingement. Additionally, cooling water discharge-coupled with the physical characteristics of the discharge structure-determines the spatial orientation of the thermal plume. This orientation, in turn, can affect aquatic species. It should be noted that the intake volume is not necessarily the same as the discharge volume. For example, the cooling water discharge from a wet closed-cycle cooling system is the intake volume less the amount lost to atmospheric evaporation. A second set of factors critical to the determination of potential impact on aquatic organisms is the load carried by the generating unit and the characteristics of the pumping system. Generally, increased load requires increased cooling water flow. This increase, however, may not necessarily translate on a one-to-one basis because many generating units employ fixed speed pumps that are on whenever the unit is generating power, regardless of load. A third set of considerations is the availability of power generated by other competing units. Under a deregulated market, a surplus of available power will limit the demand from uneconomical producers. This, in turn, limits intake flow and heat discharge from these units. Finally, all of these factors must be estimated to reflect future conditions, including demand for power, because the analysis is intended to forecast future impacts, rather than reflect past performance. The following paragraphs present an overview of the proposed project and explain how each of these factors was considered in estimating the pattern and magnitude of cooling water flows. 8.1.1 No-Build Scenario In assessing the potential biological impacts of the project, two general conditions were considered. First, the "No-Build" scenario describes the present Ravenswood facility without the proposed Cogeneration Facility. Second, the "Build" scenario describes the Ravenswood Facility with the proposed Cogeneration Facility. The "No-Build" scenario describes operation under the existing three-unit configuration, i.e., without the proposed Cogeneration Facility and without any intake modification. A detailed description of the existing facility can be found in Section 3 of this Application. Briefly, the current Ravenswood Steam Electric Generating Facility consists of three gas/oil fired units (Nos. 1, 2, and 3) with a rated capacity of 385, 385 and 972 MWe, respectively. Each unit has once- Case99-F-1625 Page ^ KeySpan Energy - Ravenswood Cogeneration Facility Article X Application through cooling with two circulating water system (CWS) pumps. Total rated pump flow through Units 1 and 2 is 214,000 gpm at each unit while flow through Unit 3 is 537,000 gpm. In addition to the CWS pumps, each Unit is equipped with two service water system (SWS) pumps, each rated at 16,000 gpm. At Unit 3 both SWS pumps are run during May through September when it is operating. During October through April, however, generally only a single SWS pump operates per Unit. The Ravenswood Facility operates conventional traveling screens (four each at Units 1 and 2 and six at Unit 3) on an automated preset wash schedule of approximately one 30-minute wash cycle every 3 hours. During periods of high debris, the screens may be washed continuously. The screens are constructed with 0.375 x 0.375-inch mesh. Cooling and service water is drawn from the East River into a protected embayment directly in front of each Unit's traveling screens. A bar rack in front of the traveling screens removes floating debris and large material before reaching the traveling screens. Fish, crabs, and debris removed from the water by the traveling screens are washed from the screens and into a screenwash sluiceway at each Unit. Since late 1994, each Unit has a polyethylene spiral-tube fish-return system to provide a smooth transfer offish through the debris basin into the discharge canal and back to the East River, via the discharge canal. Cooling water passing through Units 1 and 2 is heated to a maximum delta T of 8.70C (15.70F) while water passing through Unit 3 is heated to a maximum differential of 10.4oC (18.80F). Water from all three Units exit through a common discharge canal at the south side of the plant. The average maximum discharge temperature differential in the common discharge is 9.550C (17.250F). 8.1.2 Build Scenarios The "Build" scenario describes operation of the Ravenswood Facility with the proposed Cogeneration Facility. The proposed design for cooling the Cogeneration Facility is the Integrated Facility Cooling System. This is the most effective system, among all alternatives including the "no-build" option for minimizing the potential for adverse environmental impact. For comparison, several alternatives, including wet closed-cycle, dry closed-cycle, hybrid cooling towers and wedge-wire screens are explored. A summary of the different scenarios is presented in Table 8.1. Comparisons to flows at other stations is presented in Table 8.2. Case 99-F-l625 Page 8-5 • • • KeySpan Energy - Ravenswood Cogeneration Facility Article X Application Tal jleS.l Su mmary of Water Use Scenarios . • 1 Option Pumps Screens Cogen Unit 1 1 Unit 2 1 Unit 3 | Cogen Unit 1 Unit 2 Unit 3 ... Total Total Total Total Vol. Vol. Vol. Vol. Type No Type No Type Type No (gpm) No (gpm) No (gpm) No (gpm) No Type No Nn RnilH . CWS 2 214,000 2 214,000 2 537,000 - - Existing 4 conventional 4 conventional 6 conventional - - 3 Condition SWS 2 16,000 2 16,000 2 16,000 - - Build 1 2 Intakes combined CWS 2 214,000 2 214,000 2 Variable 2 Variable 4 conventional 4 conventional IFCS 3 6 Ristroph screens SWS 2 16,000 2 16,000 2 16,000 2 16,000 2 CWS 2 214,000 2 214,000 2 537,000 2 Variable ICS with 4 conventional 4 conventional 6 conventional wedgewire 3 Wedgewire SWS 2 16,000 2 16,000 2 16,000 2 16,000 Intakes combined4 CWS 2 214,000 2 214,000 2 537,000 - - Mechanical Draft 4 conventional 4 conventional 3 6 conventional screens (wet) SWS 2 16,000 2 16,000 2 16,000 uses Unit 3's Intakes combined" CWS 2 214,000 2 214,000 2 537,000 - • t conventional 4 conventional Hybrid (wet/dry) 3 6 conventional screens SWS 2 16,000 2 16,000 2 16,000 uses Unit 3's CWS 2 214,000 2 214,000 2 537,000 - - 4 conventional 4 conventional 6 conventional Air-cooled (dry) 3 SWS 2 16,000 2 16,000 2 16,000 - - i • 1 • • 1537,000 gpm maximum 273,000 gpm maximum 316,000 gpm is a single pump volume; i rom May thr ough Septc jmber two pumps run with a combined volume of 32,000 gpm. 4Units share SWS pumps Page 8-6 Case 99-F-1625 KeySpan Energy- Ravenswood Cogeneration Facility Article X Application Table 8.2 Flow Rates at Other Stations in the Vicinity of Ravenswood Pumps Generating Congeneration Total Vol. Station Unit Cooling Unit Type (gpm) Screens Option Arthur Kill' All 2 CWS 122,000 Vertical dual-flow SWS 16,000 3 CWS 105,000 Vertical dual- flow SWS 25,000 Astoria All 3 CWS 224,000 Vertical dual-flow SWS 16,000 4 CWS 244,000 Vertical dual-flow SWS 16,000 5 CWS 244,000 Vertical dual-flow SWS 16,000 East River All 6 CWS 113,400 Conventional SWS 5,000 Poletti All 1 CWS Var1 Conventional SWS Var2 World Trade All Conventional Center 253,000 gpm maximum 1200 gpm maximum Case 99-F-l 625 Page 8-7 KeySpan Energy - Ravenswood Cogeneration Facility Article X Application a. Integrated Facility Cooling System (IFCS) The proposed Cogeneration Facility would be located north and adjacent to Ravenswood Unit 3. The proposed Cogeneration Unit incorporates a single gas turbine generator, a supplementary heat recovery steam generator, a single steam turbine generator with condenser, kettle boilers for steam cogeneration and a water treatment facility with associated storage tanks. A more detailed description of the proposed facility can be found in Section 3. The proposed method for cooling, IFCS, will integrate the proposed unit into the existing Unit 3 screen intake chamber, obtaining cooling water through the existing Ravenswood Unit 3 screening/intake chamber. No new intake facility is required. The two existing Unit 3 CWS pumps would be replaced with two variable speed pumps. These pumps can reduce intake flow to the minimum capacity necessary to maintain efficient unit operation. Cooling water requirements for the new unit will be lower during periods when the cogeneration unit operates in steam export mode. All analyses performed in the application assumed no steam export. This is a conservative assumption in that actual flows and temperature differentials will be lower than those used in the analysis when steam is exported. The conventional traveling screens at the common Unit 3/Cogen intake would be replaced as part of the IFCS with modified Ristroph traveling screens. These screens would include key fish- conserving components such as screen basket lip troughs designed to retain water and minimize vortex stress, a high pressure spray wash system for debris removal from the front side of the machine, and a low pressure spray wash system for fish removal from the rear side of the machine.