OCR Text |
Show specific SO goal. The reduced sorbent and the zero ash content of natural gas reduces particulate loading thus lessening the need for dust collector upgrades. The emission control effectiveness of GR-SI depends to some extent on the design of the boiler. However GR-SI systems have been designed for three utility boilers with widely varying characteristics. Emission reductions of greater than 60 and 50 percent have been projected for NOx and S02' respectively. Gas Reburning - Low NOx Burners (GR-LNB) Low NOx Burners can be retrofitted to many wall fired boilers to achieve NOx emissions at low capital cost and with very low operating cost'o. Low NOx Burners slow the rate of NOx formation during the combustion process. This is achieved by delaying the mixing of the fuel and air. Under the oxygen deficient conditions which result, the nitrogen bound in the coal is preferentially reduced to atmospheric nitrogen (N~) rather than oxidized to NOx. In addition, the heat transfer from the oxygen ~eficient flame reduces thermal NOx. The delayed mixing is achieved by appropriate design of the air registers and pulverized coal injection system. Delaying fuel/air mixing extends the heat release zone in length, width, or in both directions. As a result, the flames may impinge upon the furnace wall. Since most ash particles have lower softening temperatures under fuel rich conditions, there can be increased slag deposition. In addition, the delay in the completion of the fuel/air mixing can lead to high carbon loss. Due to these considerations, the effectiveness of Low NOx Burners depends on the specific application. NO levels 30 to 50 percent lower than uncont ro 11 ed 1 eve 1 s are usua 11 y ach i evab 1 e wi thout sign i fi cant performance degradation. GR is an ideal technology for integration with Low NOx Burners if additional NO;< control is required. In contrast to Low NOx Burners, which control NO formation, GR reduces NO previously formed in the combustion process. T~e integration of GR and Low ~Ox Burners (GR-LNB) effectively provides two stages of NOx cont ro 1 and has the potent i alto increase the NOx cont ro 1 effectiveness to about 75 percent. FIELD EVALUATIONS Energy and Environmental Research Corporation (EER) is conducting field evaluations of integrated ~R systems on three coal fired utility boilers as part of the DO~ C1 ean Coal Technology Program. GR-SI is bei ng evaluated on two boi1ers"-' and GR-LNB on one boi1er'8 as follows: Gas Reburning - Sorbent Injection • Tangential Fired Boiler Hennepin Station, Unit 1, a 71 MW unit owned and operated by Illinois Power. • Cvc10ne Fired Boiler Lakeside Station, Unit 7, a 33 MW unit owned and operated by City Water, Light and Power, the municipal utility of Springfield, Illinois. 5 |