New Materials for Steam Generators with Efficiencies above 50 % (MARCKO DE 2)

Project Number 198

For the purpose of designing steam power plants with net efficiencies of more than 50%, we are talking about steam process temperatures of 650°C to 700°C and steam pressures of 300 bar to 375 bar. For tube walls exposed to hot flue gases on the combustion chamber side, the material temperatures are another 30 K to 40 K higher than those of the main steam. They are also exposed to corrosive attack.

The use of nickel-based alloys is unavoidable for these applications. Up to now, these have only been designed for applications with shorter creep strengths, up to approximately 1,000 operating hours. Important aspects for process (high-temperature thermomechanical treatment, weldability, bending properties) are still unknown.

The aim of the project is to qualify the material NiCr23Co12Mo (alloy 617) for outlet manifolds and superheater tubes in the steam generators of fossil-fuelled power plants; this material has been used up to now to line the combustion chamber of stationary gas turbines. The aim is to achieved a 100,000 operating hour creep strength of approximately 100 MPa.

At the request of MPA of the University of Stuttgart, Prof. Eberhard Roos, and also of four manufacturers, these new steam generator materials will be investigated for the temperature range up to 700°C.

The project will run from April 1, 1999, until March 31, 2003, and will be assisted and managed on behalf of the VGB by the VGB Technical Committee "Materials and Quality Supervision". The project relates to others promoted by VGB in connection with "New Materials for Power Plants" (NWK). These concern materials for steam turbines, steam generators and stationary gas turbines. The present project is being promoted as part of the materials programme, "Materials of a Low CO2 Power Plant" (MARCKO), organised by the German Federal Ministry for Economy (Project No. 0327062). It is additionally funded by the Research Association of the Working Group of the Iron- and Metal-processing Industry e.V. (AVIF, Project No. 130)