Steam conditions of 246kgf/cm2g, 538/566°C, super critical pressure single reheating has been dominant as a standard type of the thermal power plants in Japan in recent years. There was no significant progress in steam conditions since the 1960s when the above mentioned conditions were established until June 1989 when the epoch making Kawagoe No.1 unit started commercial operation with the steam conditions of 316kgf/cm2g, 566/566/566°C ultra super critical pressure double reheating.
This was because the current materials were used near their limits and enormous funding and time for research and development were needed to improve and develop mate-rials. Also, the investment for improving efficiency could not be compensated by the fuel cost reduction.
But the sudden jump of energy price caused by the Oil Shock, steady progress in mate-rial technology, and accumulated experience in designing, manufacturing, and operation of boilers and turbines made a good start in improving steam conditions and led to the comple-tion of the first large scale ultra super critical pressure plants in the world.
316kgf/cm2g, 566/566/566°C class steam conditions will be adopted to new coal fired plants in Japan. There are some elements to be developed to realize 352kgf/cm2g, 649/593/593°C class steam conditions, and it will take a little more time.When we survey future technology, ultra super critical pressure technology contri-butes to the improvement of the efficiency of not only pulverized coal firing and PFBC (Pressurized Fluidized Bed Combustion) plants, but also of the steam cycle in combined cycle plants.