Influence of coal ash characteristics on the pretreatment process of fluidized bed cement calcination

Abstract

A new two-process Portland cement clinker manufacturing equipment was utilized to substitute traditional rotary kilns for emission reduction. Cement raw meal became an intermediate product after calcination in the pretreatment process, and the intermediate product turned into a clinker after the final calcination process. During the pretreatment process, the cement raw meal granulated and CaCO3 decomposition and C2S formation occurred simultaneously. Compositions of coal ash differed with cement raw meal and influenced mineral formation and granulation in the first process. Clinker quality and equipment feasibility were influenced accordingly. Therefore, the influence of coal ash component, content and ash fusion temperature on mineral formation and granulation was investigated. Results showed that high-SiO2/Al2O3 coal ash decreased C2AS formation in the intermediate product. Minor component MgO and alkali oxides had no contribution to C2S formation. SO3 promoted C2S formation and suppressed C2AS formation. Mineral types remained unchanged and mass fraction of granules over 1 mm in intermediate products fluctuated slightly as coal ash content increased. Ash fusion temperatures of coal ash were not directly related to granulation. The pretreatment process was feasible and suggestions for fuel selection were provided from the view of coal ash.