| OCR Text |
Show Overall Summary of the 15-30 KVt Boiler Simulation Facility Tests The baseline, optimized minimum , and maximum percent reduction NOz emissions for the subject tests conducted in the BSF are presented in Table 1 . This shows that despite variables between these tests, consistently high (60+%) NOz emissions reductions can be achieved when reburning is employed as a NOz control technology and that reburning, based on the data presented herein, offers NOs reductions beyond those obtainable with staged overfire air alone . MAXIMUM NOx REDUCTION CASES L~ILIZING GAS REBURNING AT C-E'S BOILER SIMULATI O~ FACILITY LOAD BASELINE MINIMUM 6 NOs MMBtujHR NOs TESTED NOz (M\Jt ) (31 O2 (3% 02 ) 90 213 77 64% 65 185 67 641 90 179 76 58X 72 211 79 63X 72 22 7 72 68% TABLE Close-coupled (CC ) reburn (where reburn fuel is introduced through the upper windbox compartment) produced NOs emissions similar to those found for the standard reburn configuration . This system should prove very useful for retrofit , or when space and cost considerations make the standard reburn arrangement impractical . Fe'l SCA'E EXPERIME~Al ACTIVITIES AT SANTA GILLA U~IT ~ C ~ EKEL' s Santa Gilla Unit ~o . 2 is a oil-design, tangentially fired boiler of 100 ~ thermal capacity ( 35 ~;e ) . Figure 20 shows the relevant geometric and ope~a~ional characteristics of this unit . This boiler and the coal-design Unit No . I, are dedicated to expe~imental activities , particularly in-furnace pollution control and combustion optimization research . For the reburn test program , the unit was fired at its full thermal capacity with No . 6 oil main fue and liquefied petrole~ (LP ) gas reburn fuel . Gas / oil designs typically operate with very high volumetric heat release rates ; achieving substantial NOz reductions in these units can be a technical challenge in many cases . At the time of paper preparation , Unit 2 reburn testing is in progress . Baseline and overfire air (air staging without reburn fuel) tests are being run for comparison to the reburn results . Variables tested include combustion zone stoichiometries, reburn LP and carrier gas (FGR ) quantities, final O2 , main burner tilt , and reburn and overfire air nozzle tilt and yaw (horizontal tilt ). Data analysi s had just begun during the period of time when this paper was prepared . Data from the Santa Gilla trials will be made available during the conference presentation . SW1~Y OF REBURN TECHNOLOGY EVALUATION TO PATE EKEL is actively proceeding with a comprehensive evaluation of reburning technology as demonstrated by 9 Magawa" Rate (BectncaJ), MVVe 35 Plan Area Heat Release Rate, MVV/m' 5 790 Furnace LJberanon Rate, MVV/m' 0473 Fumace Release Rate. MN/m' 0 468 Fumace ExJt Gas Temperature. "C "50 Fig. 20 Main Characteristics of Santa Gilla Power Statl()(1 No 2 the workscope described in this paper . Results from the 50 KWt bench scale and 15-30 M\Jt pilot scale studies to date have shown that reburning offers promise both in terms of substantially reducing NOx (up to 681 from baseline levels in the pilot scale trials) while having minimal negative impact on other emissions (CO/particulate) or boiler operating characteristics. Alternative reburn system configurations ("close-coupled" reburning) have been tested which can achieve performance levels on par with more conventional reb urn system arrangements with the advantage of more cost effective retrofit to existing units . Additional reburn system performance data is currently being obtained from the 35 M\Je Santa Gille demonstration unit in Italy . GLOSSARY Stoichiometry (~) - ratio of combustion air to fuel where ~ of 1.0 equals the exact chemical proportion for complete combustion of the hydrocarbon fuel . Main Burner Zone - the furnace region from the bottom of the main windbox to the uppermost combustion air compartment within the main windbox (excluding the Close Coupled (CC) overfire air (OFA) compartment ) (See Figure 8) Windbox Zone - the furnace region from the top of the main windbox to the reburn compartments (same as the main burner zone if CC OFA non-operational) Reburn Zone - the furnace region from the reburn compartments to the separated OFA, or burnout air compartments (same as the windbox zone if no reburn employed ) Burnout Zone (Combustion Completion Zone ) - the region above the OFA nozzles |
