Clinker Grindability Assessment : Method development using Laboratory Ball Mill and Power Logging

Sammanfattning

Milling of cement is one of the most electric energy intensive steps during cement production, where the grindability of clinker has a large impact on the energy consumption. Grindability can be measured using standardized methods such as Zeisel-test. However, equipment is not available for these tests at the Quality and Development Lab in Slite at Heidelberg Materials. The purpose of this project was therefore to develop a method for assessing clinker grindability with a laboratory mill and a power logger. During this project, different clinker samples were milled, analysed, and blended with additives in a laboratory setting. The logged energy consumption was integrated over the milling time to calculate the specific energy consumption (SEC) which was then related to the particle fineness of the cement. The fineness was analysed with the Blaine air permeability method and laser diffraction. The effect of variations in chemical composition, mineralogy, microstructure, filler, binder and grinding aid was also researched. Results show that power logging can be used for measuring grindability with a laboratory mill. A developed algorithm could identify most of the milling runs automatically, which made it possible to calculate the SEC. A comparison of the methods for measuring fineness indicate that Blaine and laser diffraction measure different particle properties and therefore yield different values for grindability. The results also show that clinker samples, grinding aid and limestone milling strategy affect the measured energy demand and cement performance. The developed method can be used as a local complement to the external Zeisel-test, to support future optimization of materials for milling operations. Further validation against specific Zeisel-tests and analysis of additional clinker samples, is recommended to further strengthen the method.