Content area
Full text
Silica analyzers in modern power plants alert operators to harmful silica concentrations in the water-steam turbine cycle. In the boiler, silica forms silicate deposits that interfere with heat transfer and are difficult to remove. In the turbine, silica builds up on the blades and causes drastic decreases in efficiency. Power plants with high pressure boilers closely monitor silica concentrations to avoid these problems.
Plants monitor silica with online analyzers, grab-sample testing or some combination of the two. Both options are expensive. Online analyzers have high capital and maintenance costs. The cost of the reagents alone can exceed $2,000 per year per analyzer. Grab sample analysis of just one batch of samples can take a half hour or more of valuable operator time.
In an attempt to curtail these costs, engineers at PPL Generation's newest energy center in Lower Mount Bethel, Pa., decided to try a silica analyzer recendy introduced by ABB Instrumentation. This compact analyzer, the Navigator 600, can monitor up to six streams simultaneously.
A cost justification prepared for the plant estimated that the Navigator 600 analyzer would save nearly $28,000 annually by replacing three existing silica analyzers and eliminating grab sample testing. At this rate, the payback time for the new analyzer would be eight months.
Combined Cycle Generation
The Lower Mount Bethel plant, completed in 2004, is a 600 MW nominal natural-gas-fired combined cycle mid-merit peaking facility. It sits on the west bank of the Delaware River about 80 miles north of Philadelphia. Two gas-fired combustion turbine generators, two heat-recovery steam generators (HRSGs) with duct burners and one steam turbine generator in a combined-cycle configuration provide efficiencies ranging up to 60 percent.
Heat from the two gas turbines' exhaust gas is used...