High Temperature Creep and Mechanical Properties of the Packed-bed Thermal Storage Tank in 50 MWe Solar Power Plant

Abstract

In order to analyze the packed-bed tank failure and molten salt leakage problems induced by the high temperature creep and alternative stress in the solar power station, a coupled thermal-mechanical method for analyzing the creep and mechanical performances of the commercial tank with 347H material was developed by taking into account the real structure and stress loads, and the corresponding dynamic characteristics in different charging-discharging time were further numerically studied. The results show that the temperature change rate of the tank wall is obviously lower than that of the packed-bed region, and the creep phenomenon occurs at first on the wallboards 1-4 (4.2<H<12.5 m) at the end of charging (t=6 h), then on the wallboards 5-6 (0<H<4.2 m) when they experience another 8 h after charging. The operation strategies of hot and cold molten salts flowing respectively into the tank from the upper and bottom locations lead to the creep time of wallboards differing significantly. In single cycle, the creep time of the top wallboard is 18.5 h, which is 7.4 times that of the bottom wallboard. Meanwhile, the wall temperature gradient has important influence on the stress performance, and higher temperature difference leads to larger peak stress. Besides, although the stress of most wallboards (2.1 m<H<12.5 m) is lower than 30 MPa, the plastic damage phenomenon could be easily induced by the stress concentration of the fillet weld region in the bottom wallboard.

Keywords

• molten salt
• concentrating solar power
• thermal storage tank
• packed-bed
• creep