Solar power

Pumps for concentrated solar power

Molten salt is produced when salt is heated above its melting point, which – depending on the salt or salt mixture – occurs at temperatures of between 150 °C and 600 °C. Eutectic mixtures of alkali and alkaline earth salts are excellent substitutes for oil and gas as a heat transfer medium. The reason: molten salt is the only medium that can also be used at temperatures above 400 °C. Even temperatures of up to 600 °C pose no problem. The use of molten salt as a heat transfer medium is definitely an economical alternative and it has been used for thermal transfer since the 1950s. Initially, molten salts were mainly used in chemical plants, for the thermochemical treatment of metals, in hardening processes or for thermochemical cleaning.

The use of molten salts as a heat transfer medium also presents pump manufacturers with challenges, especially due to the high temperatures that the systems and components must be able to withstand. The molten salts must be pumped out during the liquid aggregate state. Pumping is extremely demanding and requires a great deal of know-how in the design of the pumps. The ITT Rheinhütte Pumpen GmbH in Wiesbaden is a specialist for corrosion proof and wear resistant materials and for the construction of highly durable pumps.

Fact benefits for customer

Fact 1

The discharge-pipe for the entire flowcapacity has been separated from the column-pipe and the pump main-shaft inside this column-pipe.

  • No distortion / alteration of the ideal flow-form and flow-speed inside of discharge pipe by Bearing-Holders or by Bearings itself.
  • No pressure losses including subsequently reduced hydraulic Efficiency caused by Bearing-Holders in the flow path.
  • Due to plenty of space for the Bearing in the column pipe the Bearing design has not to be restricted with regard to it´s radial dimensions and is therefore able to cover a higher load, especially at large temperature differences within a short time period where thinner Bearings tend to crack.
  • Defined lubrication of Bearings Independent from pumps differential pressure. No increased bearing wear by dry-running conditions in case of an interrupted pump flow.

Fact 2

The discharge-pipe for the entire flowcapacity has been separated from the column-pipe and the pump main-shaft inside this column-pipe.

  • Allows to operate the pump down to a discharge capacity of 0 m³/h at the case of a closed discharge valve.

Fact 3

Discharge nozzle

  • Available in all variations (Size, DIN /ASME Standard, Gasket systems) asdemanded by Customer.
  • Allowable loads up to 2 x API-values as standard. Higher values available upon request.

Fact 4

Test bench / test facility

  • Implementation of a new test facility in year 2016 for molten salt pumps with the possibility to test even pumps with a pipe length (insertion length) up to 20 m. The test bench concept offers possibility for customers and third-party Inspectors to supervise the entire test process.

Fact 5

Sole Plates for installation / Compensation of thermal distortion

  • Sole / Mounting Plates for pump installation can be designed and manufactured in our workshop as per requirements and structure of customers tank /vessel.
  • Compensators which have the function to decouple the pump from the tank are optionally available. These Compensators ensure, especially at large pumps and high temperatures, that thermal induced movements in lateral or vertical direction will not lead to higher forces and/or moments towards tank / vessel shell.

Fact 6

Dry and low-pressurized Shaft-Sealing

  • During normal operation pumped liquid won´t approach the area of upper shaft-sealing, which is standardly designed as a robust stuffing-box with outstanding MTBF-figures ( MTBF=Mean Time Between Failures).
  • Pressure towards Shaft-Sealing is not higher than the pressure in Gas-Phase of tank.
  • Floating Ring Seal for reduced N2 Gas consumption available as option.

Fact 7

Proven Pump design / History of Rheinhütte

  • Although CSP applications (Trough-Type or Power-Tower) in a large industrial scale are market-relevant just since 15 years, our experiences with pumping of nitrate salt melts as a high efficient heat-transfer medium can be traced back to the 1950´s .
  • The outstanding long history of Rheinhütte Co. since 1857 in City of Wiesbaden at Rhine River and the leadership in several segments in pump-market combined with the permanent endeavor for improvement of our products offers to Customer the guarantee that your expectations as valued Business partner will be fulfilled.

Fact 8

Scientifically based studies for molten salt pumps

  • Studies regarding thermal Situation of pump in tank are possible as well as studies regarding critical frequencies under utilization of “state of the art” FEM software.


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