Development of a High-Temperature, Long-Shafted, Molten-Salt Pump for Power Tower Applications

TLDR

Previous molten‑salt power tower plants required pumps housed in shallow sumps fed by storage tanks, and only cantilever pumps had been qualified for hot molten‑salt service due to a lack of suitable bearing materials. The study aims to qualify a long‑shafted molten‑salt pump with salt‑lubricated bearings. The pump was tested for over 5,000 hours at 565 °C in nitrate salt to evaluate its performance. The new hot‑salt pump reduces capital cost, eliminates many piping, valve, and sump issues, improves reliability, and removes the need for sump level‑control valves, thereby preventing pump sump overflow.

Abstract

A new hot-salt pump has been developed for molten-salt solar power tower applications that will reduce the capital cost of the plant, eliminate many of the piping, valve and sump problems associated with the handling of molten salt, and improve the reliability of a critical part of the operating system of the plant. Previous systems required that the pumps in these plants be housed in shallow sumps that were gravity fed by the storage tanks. This new pump arrangement will eliminate the sump level-control valves and the potential for overflowing the pump sump vessels. Until now, only cantilever pumps were qualified for hot molten-salt service because no suitable bearing materials had been tested. This paper describes the successful qualification of a long-shafted pump with salt-lubricated bearings tested for over 5000 hours with nitrate salt at 565°C.