This was based on the new ID fans powered by two new main auxiliary transformers, which were added as part of the flue gas desulphurization project. However, the electrical modeling also revealed that an isolated phase bus was a potential limiting component to achieving full turbine-generator output capability. Also, under certain operating conditions when the main auxiliary transformers are out of service, the generator step-up transformer also could be a potential limiting factor. Working with the isolated phase bus vendor, a low-cost solution was developed should the plant decide to remove this restriction to power output.
Here, the client’s goal was to achieve an overall 100 M W increase in generating capacity from three of its four coal-fired
units. This represented a nominal 25 percent increase from the original unit design basis and would offset auxiliary load increases that were expected from an emissions control retrofit. The evaluation examined the effect of firing different coals and an assessment of the industrial production facility’s energy needs and their impact on generating plant production.
A plant capacity evaluation generated options to increase each unit’s net generating capacity to 25 percent (without an HP/IP turbine retrofit) or 50 percent (with an HP/IP turbine retrofit and constrained by a new Environmental Protection Agency permit Q-fired limit). Initial efforts base-lined current operating performance boundaries by conducting a “valves wide open” performance test on one of the three identical turbines. Engineering studies optimized the interaction between the boiler and turbine to determine
the required boiler modifications so that it could generate the necessary steam flow rate to realize the HP/IP turbine upgrade’s full potential. Using the retrofitted boiler/turbine process parameters, a detailed balance of plant analysis was performed to eliminate any constraints that would prevent the plant from attaining the predicted generating capacity increase.
The more significant boiler modifications required to support a gross turbine-generator output increase of around 40 percent from each of the three units include the following:
•Convert the existing electrostatic precipitators from hot side to cold side operation. To increase precipitator collection efficiency, the first two fields should be converted from transformer-rectifier to switched integrated rectifier operation.
•Upgrade the FD fans with new, larger rotors to fit within the existing
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