of-plant systems which, if implemented, could achieve a new gross generating capacity rating between 808 MW and 817 MW, depending upon seasonal ambient temperatures. Integrating the boiler and balance-of-plant systems into the overall analysis removed constraints to allow the IP/LP turbine retrofit to achieve its full potential, plus deliver an

additional 30 M W under certain ambient and operating conditions.

The boiler had at least two limitations, for which the project team analyzed and developed solutions. First, firing rate and steam generation were curtailed when the flue gas temperature leaving the economizer exceeds 850 F. The reheat boiler performance program sized

Reduce

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the additional primary superheater and economizer surface that would be needed to rectify this limitation and increase the boiler’s steaming capacity.

Second, the existing water lances were not keeping the furnace waterwalls clean enough to provide good control of furnace slagging and, thus, furnace outlet gas temperature. The boiler performance program recommended adding a heat flux monitoring system and water cannons.

Balance-of-plant systems were analyzed and several limitations to increased generation and plant efficiency were identifi ed.

• The cycle cooling system (consisting of the condenser; circulating water system; and the circular, wet, mechanical draft, cooling tower) was found to have two major deficiencies. First, the cooling tower was not large enough to reject all of the heat required to obtain good cycle thermal performance and power output. Because of this, both the existing and the retrofit turbine will operate at a backpressure higher than normal for this size of turbine-generator. Second, the present circulating water flow was nearly 15 percent below the design water flow. The study recommended adding an auxiliary cooling tower and either modifying the existing circulating water pumps or adding a fifth pump to the existing four to obtain the proper water flow. A preliminary economic analysis showed that implementing the boiler and the cooling system modifications would result in a payback of slightly less than one year.

• The extraction steam system will be affected by the IP/LP turbine retrofit because the piping and expansion joints within the condenser shell will be subjected to new extraction steam pressures, temperatures and flows. The study showed that one of the expansion joints would need replacement.

•Modeling of the plant electrical distribution system indicated the system was sufficiently robust to handle the additional electrical loads caused by the unit uprate.