Vertical shaft kilns are still used in some parts of the world to produce cement, predominately in China where they are currently used to manufacture nearly half of the cement produced annually (Wang 2007). A shaft kiln essentially consists of a large drum set vertically with a packed mixture of raw material and fuel traveling down through it under gravity. Parallel evolution of shaft kiln technology with the more complex dry process rotary kilns kept the mix of pyroprocessing technologies in China's cement industry more diverse than in almost any other country. Coal is the primary fuel burned in.
