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Show participation in the project included final detail design, fabrication, installation, and testing of the system. The U.S. team is assisting in an evaluation of the system's effectiveness in controlling N O x by providing N O x monitoring instrumentation and technical support during testing. Each team focused on the use of reburning as the technology of choice for this project. Reburning (referred to in Russia and the Ukraine as "three-stage combustion") is an attractive alternative for in-furnace N O x control on slagging (wet-bottom) units where either physical or operational modifications to the existing fuel-firing system (as required with most low N O x retrofits) would be problematic from a boiler operating standpoint. As a result, reburning technology was chosen for implementation on a Ukrainian boiler of wet-bottom design. The boiler chosen to represent the design case is located at the Ladyzhin Power Station (Figure 1) in Ladyzhin, near the Ukrainian city of Vinnitsa. The power station consists of six 300-MWe, coal-fired, TPP-312 boilers. These supercritical (3625 psig) steam pressure units employ swirl-stabilized, opposed-wall- fired coal burners (16 per boiler) which burn Ukrainian high volatile bituminous coals of relatively high (25-35 percent) ash content as well as low ash (4-10 percent) Siberian lignite. The boilers operate under slagging conditions; that is, a portion (approximately 20-30 percent by weight) of the ash is retrieved as wet slag at the furnace bottom slag tap, and the remaining ash exiting the boiler is collected as flyash by electrostatic precipitators. The objective of the project was to demonstrate that reburn technology could provide N O x reductions of at least 50 percent on a coal-fired, slagging utility boiler with a wall-fired burner arrangement. If the demonstration is successful, the Ukrainians and Russians intend to extend use of the technology to the other units at Ladyzhin. As many as 300 units of this generic type are located elsewhere in Russia and the Ukraine that are potential candidates for reburn retrofit. Reburn Process Overview Figure 1: Ladyzhin Power Station The concept of three-stage combustion (reburning) and the postulated chemical reactions which account for the reduction of N O x in the reburn zone have been addressed elsewhere1,2'3'4. Briefly, reburning, as shown schematically in Figure 2, is an in-furnace technique for reducing N O x by creating a slightly substoichiometric (reducing) zone downstream of the primary combustor. The reducing zone is created by introducing fuel into a zone with insufficient oxygen available to burn the fuel completely. Interme 3 |