Cement producer Sacci S.p.A. is using an Insitec on-line laser diffraction particle size analyzer from Malvern Instruments at its site in Tavernola, Italy, for process control of the cement mill, to enhance product quality and reduce the time that operators spend on process control. The use of real-time particle size data to automate the milling circuit that produces finished cement has liberated operators to focus on higher value work. At the same time it has significantly improved product consistency.
“Before we installed the Insitec we relied on off-line particle size data to control the milling circuit,” said Alessandro Mazzucco, plant quality manager. “The quality of the data was fine but the frequency of measurement, every two hours, wasn’t really high enough. Quite large changes were made after each measurement and so our product was not as consistent as we would have liked.”
At the plant, particle size data are used to automatically vary the speed of the classifier used to separate the milled cement into a fine product stream and a coarser recycle. In the past this control loop was driven by data measured in the laboratory using a Malvern Mastersizer 2000 laser diffraction particle size analyzer. Now the data come from the on-line Insitec system.
“Our experience of Malvern was very positive so we expected the Insitec to work well,” continued Mazzucco. “It’s a robust, well-designed instrument and over the three years it’s been running, reliability has been excellent. We need to clean the optical window from time to time, but other than that it needs almost no maintenance. Being able to rely on this level of performance is crucial for 24/7 operations such as ours. Production has become far more consistent than when we relied on the off-line analysis of single samples, with much smaller process changes now made automatically on a more frequent basis.”
The Insitec is installed on the elevator conveyor that carries finished product to the storage silo. It automatically samples the cement via a two-stage sampling system which ensures a representative cut of the very large process flow. A full particle size distribution is produced every five seconds but rolling average data are used for process control.
This continuous data stream gives much finer control of the classifier, which is now varied within far tighter limits compared with using off-line measurement, leading to a more consistent product. Automating sampling, analysis, and control has saved considerable operator time - time that is now being used to further other production goals.