Low-pollutant corrosion and chromate control in heat transfer systems with nitrate melts
Duration: 1.1.2022 - 31.12.2025
Molten salts are of central importance as heat transfer and storage medium for many thermal processes and are currently used in the temperature range up to 550 degrees Celsius. Industrially, they are mainly used in processes for the production of fertilisers and melamine. In the field of solar thermal power generation, they have so far been used in tower power plants and are currently being researched for parabolic trough power plants. In addition, molten salts are particularly interesting for the operation of thermochemical reactors in which solar fuels or regenerative fuels in general are produced by electrical heating.
Due to their characteristic high melting temperatures, interactions with materials used (corrosion) and decomposition reactions in the upper temperature range (>550 degrees Celsius), the use of molten salts is generally demanding. It is important here to design the equipment to be freeze-proof, to select suitable materials and components, and to ensure safe operation management.
Key innovations for temperatures up to 600 degrees Celsius
In the SAKONI project, key innovations from industry and research are being developed, tested and qualified to enable reliable and environmentally friendly use of molten salt technology at temperatures of up to 600 degrees Celsius.
In particular, innovative components from the project partners (pump, insulation materials, trace heating) are brought together with developments specific to molten salt such as a corrosion-inhibiting layer and chromate-consuming salt additions. They are implemented in a next-generation liquid salt plant together with the plant manufacturer heat11 on a pilot plant scale at DLR. The subsequent operation takes place under conditions typical for the application, and will be tested, evaluated and further developed under independent appraisal by TÜV Nord.
By supporting higher operating temperatures, SAKONI therefore creates the basis for driving thermal processes on a broader variety of renewable energy sources in the future. In addition to the operation of solar thermal reactors with molten salts, the use of electric heaters with wind or PV electricity is thus also supported (power-to-heat).
With regard to the central innovations, the SAKONI project aims at six substantive goals that are being worked on together:
Düchting Pumpen Maschinenfabrik GmbH develops, designs and demonstrates a low-maintenance vertical centrifugal pump for use in molten salts up to 600 degrees Celsius.
CEPROTEC GmbH works out and adapts the most economical thermal insulation for piping systems at 600 degrees Celsius, taking into account the best possible environmental and health compatibility.
Winkler AG designs, develops and demonstrates a weatherproof and high temperature resistant heat tracing system for use in molten salt CSP plants.
Flucon fluid control GmbH develops, manufactures and qualifies a measurement technology for viscosity and thermal conductivity for applications with liquid molten salts at temperatures up to 600 degrees Celsius.
DLR demonstrates the effectiveness of non-hazardous molten salt additions that significantly reduce the formation of carcinogenic chromate or avoid its accumulation. The demonstration will be conducted in continuous cyclic operation at pilot plant scale.
The demonstration and investigation of a (patented) corrosion-inhibiting coating that enables the use of low-alloy steels for liquid salt applications, thus contributing to cost reduction.
