Investigating multicomponent breakage in cement grinding

• Multi-component breakage analysis was performed in cement grinding.
• Size by assay method is used to determine the particle size distribution of each component around the circuit.
• Breakage rates of the components ground in a quaternary-mixture were calculated separately.

The production of blended cements involves grinding raw materials such as cement clinker, pozzolan, blast furnace slag, limestone and gypsum, within the same mill. This is known as intergrinding. However, it is not possible to control the product fineness of each component separately in the multicomponent system and this results in overgrinding of relatively softer components. Since each component exhibits different breakage characteristics, the fineness of the components around the closed grinding circuit will vary depending on relative grindabilities and the overall fineness of the cement will then depend on the ratio of the components in the blend with different grindabilities. This paper aims to examine the size by mass distribution of each component around a closed circuit ball mill during cement production by intergrinding. For this purpose, a ball mill with an air classifier in a cement plant was sampled and size by assay analyses of the samples was carried out to calculate the particle size distribution of each component around the circuit. The results indicated that the size distributions of the components in each stream vary depending on their grindabilities and the final product comprises components with different fineness. The breakage rates of the components were calculated and it was seen that the breakage rates of the relatively softer components are higher than that of harder ones.