Tube burst occurred on platen superheater of a circulating fluidized bed boiler(CFB).Based on series of tests such as microstructure examination

chemical composition analysis and mechanical property test

long time over-temperature operation was considered as the main reason.Thus

heating surface of the platen superheater was changed into water cooling evaporate panel

to reduce the heat exchange surface

and increase the flow speed of medium inside the pipe.Furthermore

part of the superheater pipes were cut

and the coverage area of refractory were enlarged

too.Results show that

after the improvement

the outlet wall temperature of primary platen superheater is about 455 ℃

and the one for final platen superheater is about 488 ℃

which are all in a reasonable range.