LIFETIME EXTENSION OF VRM COAL MILL GRINDING ELEMENTS·METAL-MATRIX COMPOSITE TECHNOLOGIES·PUSHING THE BOUNDARIES OF MATERIAL LFIETIMES

摘要

Efficient coal pulverization is critical to downstream combustion performance and back-end emissions in coal-fired thermal power stations. The grinding elements within the mill are an essential component to reliable and efficient coal pulverization and performance. Metal-matrix composite technology, a combination of high chrome alloy metal and granularized ceramic, far exceeds the wear resistance and lifetime offered by high alloy mono-metal solutions such as NiHard, high chromium or high chromium hard-surfacing thereby pushing the boundaries of material wear performance far beyond mono-metal solutions. One such metal-matrix composite technology is Xwin~R. Depending upon the type of mill, the coal quality, and the mill operation, Xwin~R has consistently demonstrated grinding element lifetime extensions of between 2-4 times that of high chromium mono-metal alloy solutions resulting in longer running life and longer mill operating campaigns while better maintaining grinding profile consistency and grinding efficiency. An advanced metal-matrix composite technology, called Neox, has demonstrated further significant improvements in wear life. Metal matrix technologies such as Xwin~R and Neox have become the standard in India due to the severity of the coal and have been implemented in other regions of the world where coal severity is a concern or improvements are sought in extension of the mill cycle life or efficiency. This paper provides an understanding of metal-matrix composite technology and application experience using this technology on different VRM mill types and coals in Asia as well as other locations in the world.