Continuous X-ray diffraction at the buzzi unicem festus plant

Mineralogy directly indicates quality of material as well as performance of a cement plant. For example cement alite and belite (together with particle size) give an indication of strength development. The gypsum de-hydration states, e.g. hemi-hydrate and anhydrite ratio indicate cement set times. Cement standards are also mineral dependant as some limit additive levels, such as calcite or cementitious materials such as slag, ash and pozzolans. Clinker minerals indicate how a kiln is running or whether the raw mix blend is correct. For example, high free lime with high belite (low alite) indicates a cold kiln, whereas high free lime with high alite indicates a hot kiln that has too much lime in the raw mix (Ref. 2). Buzzi Unicem has long recognized that mineral analysis yields valuable information about their product and plants. As such back in 2003 they embarked on a program to monitor mineralogy continuously in real time using Continuous On-Stream Material Analyzer, aka COSMA. COSMA uses X-ray diffraction (XRD), a common analytical technique which directly measures the mineral content of cement and clinker, such as C₃S, C₂S, free-lime and gypsum de-hydration states. XRD can even distinguish between the different phases of a mineral, such as cubic and orthorhombic aluminate. Continuous XRD was first installed on a cement plant in 2001 and that experience has been presented at the IEEE conference in 2003 and 2006 (Ref. 1 and 2). Buzzi Unicem installed their first COSMA on a grinding plant in 2005, in Trino, Italy. The system was proven on the single mill which produced a variety of cements using six different materials (Ref. 3). Following this, Buzzi Unicem installed COSMAs on plants in Guidonia, Italy and Festus, Missouri in 2008. The COSMA systems were multiplexed, taking samples from three different mills. This year a clinker COSMA is being supplied at the Festus plant. This paper describes how COSMA continuous XRD analysis is being carried - - out and used to assist production at the Festus plant. It includes background on the technology and implementation at other Buzzi Unicem plants.