Thermal load deviation model for superheater and reheater of a utility boiler

Abstract

The extreme steam temperature deviation experienced in the superheater and reheater of a utility boiler can seriously affect its economic and safe operation. This temperature deviation is one of the root causes of boiler tube failures (BTF), which causes about 40% of the forced power station outages. The steam temperature deviation is mainly due to the thermal load deviation in the lateral direction of the superheater and reheater. This variation is very difficult to measure in situ using direct experimental techniques. In this paper, we propose a thermal load model that is based on the power plant thermodynamic parameters, thermal deviation theory, and flow rate deviation theory. It is found that the calculated results from our model agree well with the in situ experimental results. The predicted BTF positions are the same as that in the reheater of a 300 MW utility boiler at Wujing Power Plant. The proposed model has been used to improve the design of utility boiler in Boiler Works, predict the possible BTF in the design stage, and assess the existing designs. This model can also be applied to utility boilers of different manufactures, and has been successfully applied to the BTF prediction and prevention in the Power Station.