Dynaswirl-LN™ Case Study 112

Pittsburg Power Station Units No. 5 and No. 6

The Situation

The Environmental Protection Agency (EPA) continues to lower the allowable NOx emission rates through stringent regulations. These regula-tions are being met by several advanced methods in California.

One unit in particular at the Mirant (formerly Southern Energy California) plant in Pittsburg, CA, required a new low NOx burner system to help comply with the clean air requirements. The daily average emission rate of the existing utility boiler needed to be reduced to less than 36 ppm.

The Boiler

The Pittsburg Station Units No. 5 and No. 6 are each 326 MWe power boilers capable of delivering 2,150 kpph steam at 2,475 psig and 1,050°F. Each unit has two firing walls with two rows of six burners on each wall. There is a row of six Over Fire Air (OFA) ports – one above each burner column on each firing wall. The burners and OFA ports are all in one common windbox. Flue Gas Recirculation (FGR) is supplied to the air stream via sparger sections. Table 1 shows the boiler data.

Unit No. 5 and 6

No. Burners 24
No. Over Fire Ports 12
Boiler/Turbine Output, MW (gross) 326
Steam Flow @ MCR, kpph 2,150
Nominal Combustion Air Temp., °F 575

The TODD® Solution

In 1999, COOLflow technology was used to prepare for the supply of 24 TODD Dynaswirl-LN burners that used the existing FGR system and OFA ports. It was not necessary to increase the capacity of the FGR system or to modify the OFA ports. The TODD Dynaswirl-LN is a low NOx gas/oil burner for multi-burner and utility boilers.

The TODD Result

The TODD Dynaswirl-LN burners reduced NOx emissions by over 40%. The excess O2 and CO levels were lowered to 0.88% O2 and 133 ppm CO, which benefited efficient boiler operation. Finally, the Dynaswirl-LN retrofit improved the boiler turn-down and operating flexibility.