Pumps for molten salts

Nowadays molten salts are used mainly for the transfer and storage of heat in industrial scale plants and power station and also in solar thermal power stations, at a temperature range between 180°C and 450°C. In specific applications the temperatures even reach 560°C. “The manufacture of pumps for high temperature applications requires a high level of coordination between design engineering, material and intelligent plant technology”, states Dr. Jürgen Weinerth, Manager of Sales, Marketing & Service of the Rheinhütte Pumps Division. „Only many years of experience and precise analysis of the specific operating parameters will lead to a successful combination of these three components and so to trouble-free long term pump operation in the plant.“

In sunny regions of the Earth solar thermal power stations are an important technological option for environmental and climate-friendly electricity supplies. In solar tower or parabolic trough concentrator power stations the sun light is concentrated through mirror arrangements. At the focal spot or on the „focal line“ there is a radiation collector, known as the receiver, which heats up the fluid (molten salts or heat transfer oil) in a primary circuit. In a secondary circuit steam is then generated with this heat, and then drives a steam turbine with a generator. A constant electricity supply from individual power stations can only happen with intermediate storage of the heat, which tides them over the night. The excellent heat storage capacity of salt offers a solution for considerably increasing the efficiency of this plant.

One of these new solar-thermal power stations, known as the Archimedes Project, is being built as a demonstration plant in Sicily/Italy. This project has been developed by a consortium consisting of the Italian Energy Corporation ENEL and ENEA, the Italian national Research and Development Institute for new Technologies, Energy and the Environment.

In March 2007 ENEL and ENEA signed a contract for the construction of the Archimedes demonstration plant in Priolo Gargallo. The start of energy production is planned for the end of 2009. According to the planning details the plant can generate 5 MW of solar electricity, corresponding to a saving of about 7,300 tonnes of CO2 compared to conventional power stations.
In July 2007 FRIATEC AG – Rheinhütte Pumps Division received the order for the supply of six vertical pumps up to 8m long for pumping molten salts at 550°C.

The vertical submersible pumps Type GVSO that are used in this promising high temperature application, are made of high grade stainless steels with a special medium-lubricated sleeve bearing concept.