The context of the work is the study of a 180 bar nitrogen
recuperated and intercooled turbo-compressor of 300 MWe. The
net efficiency of this closed cycle gas turbine is assessed between
37 and 37.5%, but which could be increased by considering
waste heat recovery techniques.
Among waste heat recovery technologies which are currently
used in conventional gas turbines we find organic Rankine cycles
(ORC). This kind of machine is similar to a conventional steam
cycle energy conversion system, but uses an organic fluid instead
of water. A main challenge is the low level of temperature of
waste (90°C).
Preliminary studies are carried out on the design of ORC
using three different fluids: traditional and mature R245fa
technology, innovative R125 cycle and high pressure low
temperature transcritical CO2 machine. Different architectures
are compared and advantages of using transcritical cycles have
been underlined. From a thermodynamic point of view the best
solution would be to use R125 cycle at a supercritical pressure at
precooler secondary side and at a subcritical pressure at
intercooler secondary side. A supplementary power of more than
15 MWe could be achieved. The resulting combined cycle could
reach a net efficiency of 39%.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
