BANGOR, Pa. – ABB’s Navigator 600 Silica analyzer provides real-time readings of steam silica content during warm start-ups of a combined cycle power plant, delivering savings, measured by PPL, of thousands of dollars per day. The alternative, taking grab samples for analysis prior to start-up, often results in start-up delays of 15 to 30 minutes. Even this short delay for a 550-megawatt plant can deny revenue of $5,000 to $10,000 a day. With more than 100 warm start-ups a year, these dollar savings quickly add into the millions per year.
These results are the experience at PPL Generation’s Lower Mount Bethel gas-fired plant in eastern Pennsylvania. In late 2008, the plant installed a Navigator 600 silica analyzer from ABB Instrumentation. At that time justification was based on lower reagent and maintenance costs, with an estimated payoff period of about eight operating months. The trial led to installation of a six-stream analyzer to monitor plant operation and a two-stream analyzer to monitor the anion and mixed-bed stages of the demineralizer.
As explained by Bernard Herre, manager of the chemical laboratory for PPL Generation, the plant can't go on line until the silica content gets down to acceptable levels. Higher silica levels can reduce efficiency and damage the turbines. He says that operators can configure the six-stream ABB analyzer to selectively sequence only critical sample points during start-up.
Once the plant is online, operators return the unit to sequencing the six sample points normally monitored. Sample points for normal operation measure silica in high-pressure steam and boiler water from each of two HRSGs, plus the condensate and makeup water.