Media selection is critical for efficient and cost effective fluidized stirred milling. The specific density of media is the key parameter in the selection. This paper selects the proper density
ceramic mill media for different types of fluidized stirred mills.

I. Various types of ceramic mill media in the market
Actually, there are many types of ceramic mill media offered in the market. However we could divide them into three categories in terms of specific density, shown in the following table.

II. Select the proper density ceramic mill media for different types of fluidized stirred mills
i. Ceramic mill media for vertically stirred mills
Generally speaking, vertically stirred mills especially the big size ones should use low or medium density ceramic beads, not the high density ones. Because big vertical mills usually have a tall and deep grinding chamber, high density grinding media will be easy to sink to the bottom of mill.
When the mill is running, normal power intensity can not distribute the media throughout the feed slurry. Thus efficient grinding can not be achieved and higher energy consumption will occur. However, some small or medium sized vertical mills can use high density media to improve the grinding efficiency because their grinding chambers are not very big and tall.

Some vertical mills and the ceramic mill media they’re using
1. Chinese made 500L, 1000L, 2000L, 3600L, 5000L vertical mills mostly use low density beads with density of 2.7 g/c.c. or 3.2 g/c.c..
2. Austria GAW Technology GmbH’s 1000L and 2000L vertical mills have high dinstalled power, thus using 6.0 – 6.2 g/cc high density beads.
3. ALPINE HOSOKAWA’s 5000L vertical mills are using 4.0 g/cc medium density ceramic media.
4. Metso Minerals licensed the Stirred Media Detritor (SMD) technology from ECC

International(now trading as Imerys). The SMD is a fluidized vertical stirred mill designed for optimum grinding efficiency for fine and ultrafine grinding. It utilizes the rotational energy of the impeller arms to impart a high-energy motion to the media/slurry mixture inside the mill. This results in particle-to-particle shear and compressive forces which produce the desired grinding mechanism for efficient grinding. As above mentioned, using high density grinding media may cause the sinking problem. So low or medium density ceramic beads milling media will be more suitable.
ii. Ceramic mill media for horizontally stirred mills
The horizontal arrangement does not have the above mentioned grinding media’s sinking problem.
Using medium or high density ceramic beads can improve the grinding efficiency.
Some horizontally stirred mills and the ceramic mill media they’re using
1. NETZSCH and BUHLER’s 500L & 1000L horizontal mills in China are using mostly 6.0 g/cc density yttrium stabilized zirconia beads. And a few are using 4.0 g/cc media.
2. XSTRATA’s IsaMills are using mostly 3.7 g/cc and 4.0 g/cc ceramic grinding media.