For the current investigation and simulation of superheater
tubes the P91 steel tube samples were placed in the vicinity of
boiler final superheater, SH3, in the area between the cyclones and
the convective section. The sampling probe was cooled by some
ambient air sucked into the tube. The flue gas temperature in that
area and the temperature inside the tube were measured by thermocouples
and were roughly 850 C and 700 C, respectively. The
temperature of 850 C was an optimum and typical for CFB combustion
flue gas, while 700 C inside the tube was chosen as an
average value of steam temperature in modern advanced power
boilers (currently up to 600e620 C) and in the boilers that are
planned to be designed in near future (temperatures of up to
700e740 C are considered). The sample residence time during all
the industrial tests was 12 h.