Luminant, a subsidiary of Energy Future Holdings Corp. (EFH) -which owns competitive and regulated energy subsidiaries in Texas -is the largest electricity generator in Texas. Unit two of the Oak Grove Power plant near Franklin in Robertson County, TX went online in the middle of 2010.
Fluor, the project’s EPC company, completed the plant in 35 months and used advanced control technologies to make the Oak Grove super-critical generating station one of the cleanest coal-fired power plants in the U.S. while providing electricity to more than 1 million customers in Texas.
Modern lignite plant
The plant consists of two 800 MWe supercritical 1,000 °F/ 3,550 psia, 1,000 °F reheat boilers firing local lignite. Unit 1 is a tangentially fired Alstom boiler with eleven pulverizers. Unit 2 is an B&W opposed wall fired boiler with ten pulverizers. Oak Grove is one of the nation’s first 100 percent lignite-fired plants with SCR and activated carbon sorbent injection for mercury control. The units are designed to have lower emission rates than any existing lignite plant and rates at least 70 percent lower than the national coal plant average.
Primary airflow control is pivotal for pulverizer and burner operation and thus effects efficiency and emissions of the boiler unit. The PA reading is also a safety aspect for the power plant operation. Finally the air contains fly ash due to recirculation. Consequently this application is very demanding regarding the flow meter
Field tested technology
Texas lignite has a high ash content and is very abrasive. With regenerative air heaters the fly ash carryover is a problem for other flow measurement devices. Other Luminant plants had previously tried pitot tubes, hot wire anemometers and other flow devices unsuccessfully. Starting in 2004 PROMECON had supplied primary air flow measurement for the coal mills on multiple lignite fired boilers in the United States. With that success the correlation based and drift free PROMECON flow measurement technology was specified for the new boilers at Oak Grove. To satisfy redundancy requirements two separate McON air systems were provided for each primary air duct - in total 42 Systems have been installed. The equipment was redundantly wired such that any component failure would safely provide a flow reading in each duct. The installation has been a full success helping the plant to operate efficient, environmental friendly and safe.