Super critical is like 2X superheated steam... correct me if Im wrong, buta SC units' steam is when the temperature is greater than the pressure. 2200PSI and 2300F.
We had a plant at Powerton (Pekin Il) that was a SC unit, but never got to work there... ws
From RE.... er ah, wikipedia...
Supercritical steam generatorsSupercritical steam generators (also known as Benson boilers) are frequently used for the production of electric power. They operate at "supercritical pressure". In contrast to a "subcritical boiler", a supercritical steam generator operates at such a high pressure (over 3,200 psi/22.06 MPa or 220.6 bar) that actual boiling ceases to occur, and the boiler has no water - steam separation. There is no generation of steam bubbles within the water, because the pressure is above the "critical pressure" at which steam bubbles can form. It passes below the critical point as it does work in the high pressure turbine and enters the generator's condenser. This is more efficient, resulting in slightly less fuel use. The term "boiler" should not be used for a supercritical pressure steam generator, as no "boiling" actually occurs in this device.
[edit] History of supercritical steam generationContemporary supercritical steam generators are sometimes referred as Benson boilers. In 1922, Mark Benson was granted a patent for a boiler designed to convert water into steam at high pressure.
Safety was the main concern behind Benson’s concept. Earlier steam generators were designed for relatively low pressures of up to about 100 bar (10,000 kPa; 1,450 psi), corresponding to the state of the art in steam turbine development at the time. One of their distinguishing technical characteristics was the riveted water/steam separator drum. These drums were where the water filled tubes were terminated after having passed through the boiler furnace .
These header drums were intended to be partially filled with water and above the water there was a baffle filled space where the boiler's steam and water vapour collected. The entrained water droplets were collected by the baffles and returned to the water pan. The mostly dry steam was piped out of the drum as the separated steam output of the boiler. These drums were often the source of boiler explosions, usually with catastrophic consequences.
However, this drum could be completely eliminated if the evaporation separation process was avoided altogether. This would happen if water entered the boiler at a pressure above the critical pressure (3,206 psi); was heated to a temperature above the critical temperature (706 degrees F) and then expanded (through a simple nozzle) to dry steam at some lower subcritical pressure. This could be obtained at a throttle valve located downstream of the evaporator section of the boiler.
