When considering the choices for new generation, each partner evaluated its individual needs. Numerous technologies were considered, including commercial availability, reliability, environmental effects, and the need for base load capacity. These factors resulted in the selection of a super critical pulvirized coal (SCPC) based generating unit designed for sub-bituminous, low-sulfur coal.
SCPC technology was selected for the Project because at the scale required it was found to best meet the Project’s requirements. A supercritical steam cycle is energy efficient allowing the unit to maximize energy production while minimizing air emissions.
The term “supercritical” refers to the steam cycle used in the plant design. When water pressure is increased to 3,200 pounds per square inch (psi) and temperature is increased to approximately 700 degrees Fahrenheit, water changes to steam without going through a conventional boiling process. These conditions are referred to as the “critical point” of water.
Units that operate above these conditions are called “supercritical,” while units operated below these conditions are called “subcritical.” The Project unit will be designed to operate at or above 3,600 psi and 1,080 degrees Fahrenheit. This design significantly improves unit efficiency over traditional subcritical unit designs. The result is that less fuel is required, which reduces operating costs, water requirements, and air emissions.