A mill is a device, often a structure, machine or kitchen appliance, that breaks solid materials into smaller pieces by grinding, crushing, or cutting. Such comminution is an important unit operation in many are many different types of mills and many types of materials processed in them. Historically mills were powered by hand or by animals (, via a hand .
The discharge mechanism of a mill is an important design characteristic, as it can have a significant impact on the throughput of the mill. The flow characteristics through the mill are commonly discussed in terms of the slurry head that builds up within the mill, grinding chamber. This property is referred to as slurry lifters are a commonly found discharge .