Editorial - VGB PowerTech Journal 8/2015
Increase of efficiency by qualification of materials and components on the basis of field tests
Steam power plants form the backbone of reliable energy supply in Germany and Europe. They are indispensable even with enhanced expansion of renewable energies. Power plant technology is faced with constantly increasing requirements for new and existing plants with regard to flexible operation, reduction of emissions and increase in efficiency to e.g. values > 50 % which would cause sustainable reduction of emissions as well as worldwide conservation of fossil resource.
German and European globally active manufacturers of components for steam power plants have to meet a broad range of demands now and in the future. In order to place successfully their products on the international markets, they need to demonstrate the technical feasibility and cost effectiveness in Germany and Europe.
Current technology has to be improved to meet the requirements of efficiency increase, flexible operation and sustainable reduction of emissions. In addition to technical aspects, such improvements also involve consideration of economic efficiency and specific requirements of standards beyond the state of the art.
The further development in the field of materials for steam power plants of the last few decades was based on steady accumulation of operational experience and basic research projects. The latter can only deliver knowledge about basic material data and a restricted characterisation of the specific failure mechanisms of complex loaded components, as in reality, during operation, special loading conditions will arise, which also will be influenced by production and processing of the component and the specific installation in relation with the operational situation in the power plant.
Technical and economic testing of new materials in addition to their further processing in pilot and demonstration projects can be considered as an important milestone in the qualification of new materials to the large-scale deployment. New developments and alternatives are not free of risk. A continuous balancing of different options is required which is not simple considering the complex issues. Distinctive knowledge in process technology, mode of operation and holistic system knowledge, covering the entire value-added chain, is necessary. The required rapid implementation of progress in technology calls for an integrated approach with direct participation of all stakeholders in the process chain of material, boiler and tube manufacturers, system suppliers, surveyors, science and utilities integrated in a common technical-scientific task. Thus, a high transfer into practice and synergies increase the competence of all stakeholders, leading to a better position on the global market. In addition, also the role as pioneer for the continuous development of resource conservation and environmentally friendly energy conversion will be strengthened.
Within the framework of the BMWi-Project “Investigation of operational and failure behaviour of thick-walled components for high-efficient power plants” a high-temperature material test path (HWT II) was set up in Grosskraftwerk Mannheim (GKM). The objective was to expose components to loading, reflecting the new operational situation of power plants after the change in energy policy in Germany (“Energiewende”) and thus to investigate their operational behaviour. With the use of the Nickel alloys Alloy 617B and Alloy C-263 a new class of materials for pressure equipment in power plant engineering was introduced in strict accordance with the applicable regulations and standards. The strength potential of these materials also could be used for structures exposed to higher temperatures/pressures but also for reducing the wall thickness in order to make the component tolerant to the thermal gradients of flexible operation.
Yet Nickel alloys had been used for the first time as structural material for thick-walled pressure equipment, e.g. tubes, headers, valves and casings. The physical and mechanical-technological properties of Nickel alloys are significantly different from that of low- and high-alloy steels used so far. These differences also influence the manufacture and processing of components and consequently have an impact on their deformation and failure behaviour. Transfer of methods used for design and life and failure assessment, successfully used for components made of creep-resistant steels to Nickel alloys components, requires fundamental reviewing, taking into account the specific material properties. The operation of the worldwide unique GKM test path demonstrates an excellent possibility to check the methods, to evaluate uncertainty factors and to optimise reliability. With the successful execution of the 18 m € project, the 29 partners involved have made a major contribution to improving the technology for higher efficiency and flexibility. It demonstrates that future steam power plants with efficiency > 50 % also taking into account the new conditions of the “Energiewende” are realistic and that these new types of power plants could reliably contribute to for secure energy supply.
The project was funded by the German Federal Ministry of Economic Affairs and Energy (BMWi project number: 03ET2017), with financial support of VGB and own contributions by the project partners. Special thanks go to all concerned in the successful execution of the project, particular to Project Management Jülich (PtJ). The demanding goals of the project could only be achieved due to the commitment of all partners.