Power Plant Instrumentation and Control Handbook

Appendix V

Super/Ultra Super Critical Power Plants

Depending on the operating condition, steam power plants can be divided into subcritical, supercritical, and ultra supercritical categories. The criticality is based on the critical pressure point for steam, i.e., 221 MPa and 374°C. Power plants operating at steam pressure below critical pressure are subcritical power plants, and plants operating with a steam pressure >221 MPa and steam temperature >374° are supercritical power plants. The supercritical stage is a thermodynamic expression describing the state of the substance; here it is water and steam, where there is no distinction between the liquid [water and gaseous (steam)] phases. In the subcritical stage latent heat is necessary to convert ...