Dynaswirl-LN™ Case Study 110

Encina Power Station Units No. 4 and No. 5

The Situation

The Environmental Protection Agency (EPA) continues to lower the allowable NOx emission rates through stringent regulations. These regulations are being met by several advanced methods in California. The Cabrillo Power I LLC plant in Carlsbad, CA, required a new low NOx burner system to comply with the San Diego Clean Air requirements. The daily average emission rate of the existing utility boiler needed to be reduced to less than 30 ppm.

The Boiler

In particular, Cabrillo Power I LLC was modifying Encina Station Units No. 4 and No. 5. Unit 4 is a 320 MWe power boiler, capable of delivering 2,278 kpph steam at 2,225 psig and 995°F. Unit 5 is a 345 MWe power boiler, capable of delivering 2,405 kpph steam at 2,300 psig and 1,005°F. The units each have two firing walls with three rows of four burners on each wall. There is a row of four Over Fire Air (OFA) ports, one above each burner column on each firing wall. Flue Gas Recirculation (FGR) is supplied to the air streams via sparger sections. Table 1 shows the boiler data.

Unit No. 4 Unit No. 5

No. Burners 24 24
No. Over Fire Ports 16 16
Boiler/Turbine Output, MWe 320 345
Steam Flow @ MCR, kpph 2,278 2,405
Nominal Combustion Air Temp., °F 460 480

The TODD® Solution

In 1999, a contract was awarded for the turnkey supply and installation of 24 TODD Dynaswirl-LN burners and eight TODD advanced Separated Over Fire Air (SOFA) ports for each boiler. The Dynaswirl-LN is a low NOx gas/oil burner for multi-burner and utility boilers.

In planning the retrofit, COOLflow technology was used to design a physical model of both units. COOLflow helped model the combustion air, FGR and advanced SOFA systems; helped correct air-flow problems; maximized the FGR mixing device performance; and helped ensure the proper SOFA penetration into the rising furnace gases.

The TODD burners and advanced SOFA ports for Unit 4 were installed during a turnkey outage in December 1999. This unit will undergo an FGR upgrade in November 2000. The Unit 5 burners and advanced SOFA ports were installed during another turnkey outage in March 2000.

The TODD Result

The TODD Dynaswirl-LN burners, advanced SOFA ports and COOLflow modeling reduced NOx emissions by over 85% to 20 ppm in Unit 5 and to 30 ppm in Unit 4. The scheduled FGR upgrade in November is expected to reduce Unit 4 emissions to match Unit 5 levels. The excess O2 and CO levels were lowered to between 1.0-1.5% O2 and less than 300 ppm CO. Also, the Dynaswirl-LN retrofit improved the boiler turndown and operating flexibility.

Encina Unit 5 Low NOx Results 327 MWe

Baseline Test Post Retrofit Test
Excess %O2 (wet) 0.90 1.0
OFA/SOFA (%) 12 23
%FGR 9.57 25.3
NOx (ppm @ 3% O2) 59 19.8
CO (ppm @ 3% O2) 100 300

Encina Unit 4 Low NOx Results 327 MWe

Baseline Test Post Retrofit Test
Excess %O2 (wet) 0.86 1.50
OFA/SOFA (%) 12 21
%FGR 7.13 ~20.5
NOx (ppm @ 3% O2) 93 29.4
CO (ppm @ 3% O2) 48 307

In 1999, the sub-30 ppm NOx guarantee for this project was the lowest ever stated and successfully demonstrated for a utility low NOx retrofit project. The 20 ppm operation on Unit 5 is the lowest NOx in the USA on any utility boiler greater than 200 MWe using only combustion modifications for NOx control, which supercedes TODD’s previous record-breaking experience highlighted in the Contra Costa Unit 7 case study, No. 109.