The high-temperature sulfur corrosion resistance of S30432 and TP310HCbN typically used in the superheater and reheater of a 620 degrees C ultra-supercritical boiler is investigated in this study. Samples coated with coal ash are placed in a device filled with simulated flue gas at 650 degrees C and 700 degrees C, respectively, for 2000 h. The samples are then analyzed through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. S30432 is mainly oxidized under 650 degrees C and 0.2% SO2 volume concentration, and the weight reduction is 6.6 mg cm(-2). However, under 700 degrees C and 0.3% SO2 volume concentration, severe sulfidation reaction occurs, sharply accelerating high-temperature corrosion. As a result, weight reduction up to 41.8 mg cm(-2) occurs. Although sulfidation reaction also occurs in TP310HCbN, there is no serious corrosion; the corrosion rate reduces in the later stages of the experiment, and a weight increase of 2.4 mg cm(-2) is observed. After 11 520 h of the actual operation of the 1000 MW 620 degrees C boiler, there is no obvious high-temperature corrosion in the high-temperature areas without coke-block adhesion. These results indicate that S30432 and TP310HCbN satisfy the requirements of 620 degrees C ultra-supercritical boilers burning high-sulfur coal.

Wall temperature of heat transfer tubes is one of the most important parameters indicating the operation safety of various heat transfer facilities, and as a result, estimation of the wall temperature becomes one of the main tasks in the design of heat transfer facilities. The wall temperature look-up table (Tw-LUT) can be established directly from experimental data and can be then used to estimate the wall temperature of the heat transfer tubes, avoiding the approximation or extrapolation of fluid properties that inevitably exists in the heat transfer correlations. In view of the problems existing in applications with wall temperature estimations of the heat transfer tube, such as limited data points and the limited application scopes of parameters, a look-up table is built in this paper for wall temperatures of vertically-upward round tubes of 10 mm tube diameter with heat transfer to supercritical water (SCW), under conditions with pressure in the range from 22.5 to 31 MPa, the mass velocity in the range from 200 to 3000 kg.m(-2).s(-1), the heat flux in the range from 200 to 1800 kW.m(-2), and the bulk fluid enthalpy in the range from 1000 to 3000 kJ.kg(-1). In order to cover the gaps between the experimental data points, and to improve the prediction accuracy of the Tw-LUT, the best heat transfer correlation is selected for each local area of interest in the LUT based on its prediction accuracy in the corresponding local area, and then the best heat transfer correlation is adopted to supplement wall temperature results to fill up the Tw-LUT. The comparison between the wall temperatures by the Tw-LUT and the experimental wall temperatures is carried out to verify the accuracy of the Tw-LUT, and it is shown that the mean absolute deviation of the results is 0.87%, and 87.81% of the results fall into the +/- 3% error band, indicating that the Tw-LUT has a good accuracy for wall temperature prediction and the establishment method is reliable and can be used to build other look-up tables. The Tw-LUT can be applied not only to normal heat transfer conditions but also to deteriorated heat transfer conditions and enhanced heat transfer conditions with a satisfactory accuracy.