SO3 control
Online elemental analysers are generally relied upon for real-time analysis of the primary elements which make up clinker – Si, Al, Fe and Ca – as well as Mg, K and Na. It is rare that a cement producer even looks to the analyser for S information, but that is clearly a priority of the Branford plant.
Florida has strict emission limits on SO2, and the Branford quarry does have some sections high in pyrite (FeS2), which if not diluted in the feed to the limestone stockpile, would result in emission exceedances. (While the actual form of sulfur in the quarry is FeS2, the lab analysis reflects it as SO3 equivalent, which then leads to SO2 in stack emissions.) Further, the insoluble nature of pyritic sulfur – and its tendency to increase in concentration due to material scrubbing in the raw mill – can lead to fouling of the preheater tower. These adverse consequences of spikes in SO3 explain a lot of the motivation for the addition of the quarry analyser and for the inclusion of SO3 in the loader cab display. As a result, the Branford plant is able to comply confidently with environmental regulations.
Analyser data management
While the analysers provide vast amounts of data, with full elemental detail available every two minutes, it’s not always obvious where to display the data and in what form. It therefore seemed entirely appropriate to merge the analyser data with the rest of the instrumentation data throughout the plant, and that occurs in the PI data base system. From there, the analyser data can be configured as needed. The plant has created two summary screens available at monitors throughout the facility. One has six trend displays, two of which are quarry and raw mill results. These two trend displays show the critical real-time information from the CNA’s. A second summary display incorporates key operating data from the quarry, raw mill, kiln, coal mill, and finish mill .
Summary
In its 13-year history the Suwannee American Cement plant at Branford has received a combined twenty years of reliable real-time composition information from its two PANalytical CNA online analysers. Through its own creativity, the plant has found ways to improve its quarry management, particularly with respect to LSF and SO3. These analysers are vital instruments, which bring economic benefit to the plant on a daily basis.
This is part three of a three-part article written for World Cement’s May issue and abridged for the website. Subscribers can read the full May issue by signing in, and can also catch up on-the-go via our new app for Apple and Android. Non-subscribers can access a preview of the April 2016 issue here.