Section B Ι New Build Invesments

Thursday, 22 September 2016, 09:00-09:30h/B01

First operational experience with advanced materials in USC boilers of RWE Generation

Dr. Frank Neumann, Christoph Götte, Dr. Jens Hannes, Georg Bung and Dr. Reinhold Elsen, RWE Generation SE

In 2005/6 the Federal Government initiated a program to supplement conventional new build power plant with plants having a significantly higher efficiency compared to the old plants. This lead to an unprecedented concentration of new build projects in Germany and other European countries.

Over the past 16 years, 7 new power plant units were built just by RWE with an installed capacity of more than 6 GW operating in the portfolio of hard coal and lignite-fired plants. These modern plants reach the world's highest efficiencies according to the current state of the art. These efficiencies are achieved mainly by raising the steam parameters that became possible by the application of new, advanced materials. Some of these materials came into commercial operation for the first time in this new generation of power plants with USC boilers and their performance for large-scale applications could only partially tested under operational conditions in existing pow plants in test tracks.

Numerous experiences on each single material in their respective application areas covering manufacturing and operation exist after commissioning and the first years of commercial operation.

The first major challenge in the new plants was certainly the material T24. In numerous research projects, the material has been specifically tested and qualified for use as a membrane tube wall material. Nevertheless, numerous damages arose during commissioning of various power plants. Hence, an extensive R & D program has been launched at RWE Generation to solve the problems with this material. Extensive special measures have been developed to reduce the risk of damage from T24 welds during commissioning.

During the first operation period of the BoA 1 unit extensive tube damage occurred in the region of superheater 5 and reheater 3 (Material X3CrNiMo 17 10) at the austenitic heating surface. This was due to spalling inner protective layers in the final superheater, which led to blockages in pipe bends, overheating and subsequent pipe failures. Such flaking and damage was not experienced until this material was selected in 1998. Based on this experience only 27% Cr steels (DMV 310 N or the Japanese version HR3C) were used in subsequent installations for the steam temperature range > 600 °C. But even with these new austenitic pipe materials for the final stages of the USC steam generator there are new, unexpected difficulties and challenges.

Today we have experience with these advanced materials with operating times of up to 40.000 operating hours. Although some significant difficulties arose when handling these materials, we are now able to understand the mechanisms and to develop appropriate measures for the erection, operation and maintenance of the power plants.

In this lecture we deal with the materials and their operating behaviour and explain measures for the respective materials derived from the research activities.