Maximise the benefit of off and at-line system

Relative to conventional off-line Blaine measurement off- and at-line laser diffraction particle size analysis supports better control by providing:

• Complete size distributions, rather than an averaged figure
• Fully automated analysis

Complete size distribution data allow for more sensitive set-point specification. Research shows that finer particles promote early strength, while the fraction of material in the size range 3 to 32 microns is an excellent indicator of 28-day strength. These subtleties cannot be understood through Blaine measurement.Controlling at a set-point defined in terms of size parameters enables the more precise targeting of strength specifications for better product quality.

Correlating particle size and cement performance

Fully automating analysis gives excellent data integrity. Off- and at-line laser diffraction analysis of cement involves pouring the sample into the instrument and pressing a button. Repeatability and reproducibility are extremely high. In practical terms this means that each result produced can be relied upon for control, minimizing the risk of taking inappropriate action, prompted by an erroneous result. Analysis speed is also important here, with measurements taking just a few minutes.

The knowledge provided by off- and at-line measurement supports the development of process models, descriptors of the impact of control parameters on product quality (as defined by particle size data). Such models can be used to successfully automate process control. A robust process model, in combination with hourly particle size measurement, can deliver relatively tight process control, especially when process dynamics are relatively slow.

For example, at the Holcim site in Obourg (Belgium) an automated laboratory has been installed for the routine analysis of cement composition and particle size. Within this facility an Insitec at-line particle size analyzer from Malvern Instruments provides detailed particle characterization. Analytical results, normally produced every hour, are fed directly to the plant control system driving automated process control on the basis of detailed models developed for each cement grade.

To read the Holcim case study, click here

To find out more about Malvern’s off- and at-line analyzers for cement....