A proposal for the use of a very high temperature ceramic heat exchanger in gas turbine power production

A highly efficient gas turbine plant is considered which uses ceramic heat exchanger components to take advantage of the very high turbine inlet temperatures available today. The materials used in the heat exchangers may have temperatures in excess of 1000°C. Most advanced power production plant have the process fluid (steam or gases) usually enclosed inside tubes surrounded by combustion gases. A heat exchanger is proposed that has combustion gases on the inside of ceramic tubes in a shell and tube heat exchanger arrangement. The pressurised working fluid flows over the outside of the tubes in the shell. The ceramic tubes are thus kept in compression by the high pressure of this process fluid, utilising the impressive resistance of ceramics to compressive force. The system described could be used in an exhaust-gas heat exchanger gas turbine power cycle to raise the thermal efficiency to approximately 65% (10% about above that obtainable by conventional combined cycle power plant). The low pressure exhaust gases (say 1000°C) from the secondary turbine are fed into the ceramic heat exchanger to heat the air from the high pressure compressor. This high temperature air is then fed to the combustor to provide gases at around 1260°C/5 b for the turbines. The exhaust energy of the heat exchanger (200°C) could be used to raise steam for district heating purposes giving an excellent overall use of energy