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Show 4,857 64.2*/ ^fl ^r \ 1,154 ^H Br 1,554 Ca) Population Nurrtoer of Units 904,767 81.6* 1 9,971,000 45.9* / ^ \ 9,271,790 47.4* C O Power Capacity Brake Horse Power ^ ^ ^ \l17,659 10.6* ^66,735 7.8% CtO Estimated NOx Emissions Tons of NOx | | Gas Turbines | | Lean Burn per year R G C I P S . | | Rich Burn Recips. Figure 1. Estimates of population, capacity, and N O x emissions 3.0 CANDIDATE NOx CONTROLS FOR PRIME MOVERS Candidate NOx controls for retrofit on existing prime movers are summarized in Table 5. Reciprocating engines are distinguished among two and four stroke engines and with either naturally aspirated or turbocharged air systems. This distinction is important because it affects the applicability of certain controls. Although all these technologies represent candidate controls, not all are considered viable for retrofit on prime movers at natural gas compressor stations. The following summarize the applicability, performance, cost, and experience of each control option. Water Injection for Gas Turbines The injection of water (or steam) in a gas turbine's combustor lowers the peak combustion temperature and the average exhaust gas temperature entering the power turbine. The drop in peak temperature results in significant N O x reduction, and generally, depending on the amount of water injected, an increase in unburned fuel in the form of C O and total hydrocarbon emissions. Performance obtained on large base-loaded heavy-duty and aeroderivative gas turbines in cogeneration and utility applications has shown controlled N O x levels in the range of 27 to 50 p pm corrected to 15 percent 0 2 from uncontrolled levels of 67 to 240 ppm. All major gas turbine manufacturers offer retrofit kits for W I for their gas turbines and are conducting research on methods to reduce increased combustor wear and equipment failure associated with the technology. 3 1-4 |