EPRI Case Study on Operational Flexibility #8: Subcritical Drum Boiler—Low-Load Evaluation

Improving the operational flexibility of fossil steam generating units is important to support the evolution of the power supply system. This report presents a methodology for understanding and improving generating unit minimum loads. The methodology uses engineering reviews and operational testing to diagnose limits and identify approaches to improve minimum load. The methodology can be applied to any type of fossil steam generating unit technology.

A case study using the operational flexibility improvement methodology is provided in this report for a coal-fired, subcritical drum boiler. Specific recommendations for reducing the minimum load for this type of unit are provided. In this case study, the unit minimum load was reduced by approximately 17%. Also provided is guidance, based on the experience in this case study, concerning the implementation of the operational flexibility improvement methodology.

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