PROJECT PROFILE: HUNTINGTON BEACH GENERATING STATION 

 

"WORLD'S CLEANEST THERMAL POWER PLANT"

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Technical Summary 

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NEC designed, engineered, and rebuilt two 225 MW generating units (3 & 4) and implemented state-of-the-art pollution control equipment to revitalize this large scale natural gas fired AES thermal power station.

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NEC, as prime contractor working with PMSI, redesigned and replaced two super-critical steam generators and rebuilt two 225-megawatt cross-compound high pressure turbine generator units simultaneously. In addition, all auxiliary equipment and systems were upgraded or replaced with the latest technology. State-of-the-art NOx and CO emission systems were designed and put into place, and the primary control system was replaced by installing a new central distributed control system, including steam turbine generator control systems.

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The project required only 16 month, operating 2 shifts per day, employing 735 men at the peak phase with over 270 subcontractors totaling 1,000 men.

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The steam generator work consisted of redesigning and replacing all the high-pressure boiler components, associated equipment, and flue gas ducting from the boiler to the stack. This work entailed major structural modifications to the existing boiler and ductwork structures, and included removing and replacing 1,200 tons of boiler pressure parts and 650 tons of flue gas ducting to accommodate a higher-pressure boiler gas path system from the fans to stack breeching. NEC developed an analytical model of the boiler and duct structure to validate reinforcing requirements in order to maintain complete structural integrity. The process included a three dimensional analytical model to identify effects of the boiler structures and was used in removing and replacing new duct sections.

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The air pre-heater was rebuilt and replaced, as well as the control dampers and expansion joints, which consisted of 25 tons of material. The steam generator burners were replaced with 24 new low NOx burners for each unit. Four new 1,750 HP boiler fans were put into place with variable frequency drivers.

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In addition, the units post combustion controls were re-designed and installed to include both selective catalytic reduction (SCR) and oxidizing catalyst to reduce both emissions levels to be below 5PPM at 3% O2. NEC's design and implementation of the SCR and CO systems established this project as the cleanest burning plant in California to date. The SCR system included structural design and support of all SCR ductwork and support of the SCR housing within a new support structure, including 750 tons of ducting and 400 cubic yards of reinforced concrete foundations and structure steel to support SCR and CO systems. A new process was installed for ammonia production "on-demand".

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The two 225 megawatt cross compound steam turbine generators were disassembled, overhauled, and rebuilt. A complete overhaul of the turbine generator rotor and stator, including re-wedging, an inspection/testing program, meggar, polarization index, El Cid, and high potential testing each of the four generators was completed. NEC implemented a new solid-state excitation system and a power stabilizer system consisting of redundant controllers.

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The project also included replacing 28,000 tubes in two condensers, repairing four 500 HP vertical mixed flow circulating water pumps with an operation flow of 44,000 GPM, refurbishing 18 feedwater point heaters and eddy current test tubes, and in some cases, re-tubing the heaters.

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All auxiliary equipment was overhauled, upgraded, or replaced and tested. This included the deaerator system, equipment related to the turbine-generator block (including boiler feed pumps), seal oil and hydrogen related equipment, condensate pumps, booster pumps, lube oil pumps, steam exhausters, and associated equipment. A new plant instrument air system was designed and put into place, along with new air piping.

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NEC also removed, redesigned, fabricated and reinstalled approximately 50,000 lineal feet of pipe ranging from A-106 Grade B standard up to A-335, P-11, and P-22 with up to 3-inch wall thickness, and rebuilt or supplied approximately 1,000 valves. All plant piping was tested on-site through x-ray and heat treating critical systems. The condensate polishing system was also designed and replaced, including new back-washable pleated filters with 1-micron cartridges.

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A complete overhaul of the turbine generator rotor and stator was performed, including re-wedging, an inspection/testing program, meggar, polarization index, El Cid, doble and high potential testing each of the four generators. A new solid-state excitation system and a power stabilizer system was also installed.

 

Project Performance   

 

• NEC's design and implementation of the SCR and CO systems established this project as the cleanest thermal generating facility in California to date. In general, this plant has been regarded as the cleanest thermal power plant in the world.

• All NEC designs and supporting calculations were approved by the State of California energy technical consultants. There were no major injuries and no loss time.

• The plant emissions are well below the strict emission standards established in Los Angeles by the South Coast Air Quality Management District and the U.S. federal standards set by the Environmental Protection Agency (EPA).