Book excerpt: This book focuses on how to keep blast furnaces running stably and smoothly with low consumption and long operating life spans. Assessing and adjusting blast furnace performance are key to operation. The book describes in detail cases of both successful and failed blast furnace operation. It also demonstrates various phenomena and “symptoms” in the smelting process that have rarely been studied before, e.g. abnormal gas distribution, bending loss of tuyere, slag crust fall-off, blast furnace thickening, and hearth accumulation. As such, it will help readers understand internal phenomena in blast furnaces, providing a basis for developing intelligent control and management systems.