Glossary
Cement
Vertical roller mill
Also known as VRM, vertical roller mills.
A vertical roller mill (VRM) grinds material between rotating tyres and a static grinding table inside a single vertical housing. Hot gas from the preheater tower or kiln exhaust dries the material during grinding and entrains the ground product upward to a classifier that separates fines for collection.
Why VRM displaces ball mills
- 30–40% lower specific energy consumption
- Smaller footprint
- Built-in drying of damp raw materials
- Easier integration with kiln-exhaust heat
- Lower maintenance for the same throughput
Where ball mills persist
Cement grinding (clinker + gypsum) is still partly handled by ball mills because the very fine particle-size distribution required is harder to achieve with a VRM. Many plants run a hybrid: VRM for raw and coal, ball mill or VRM for cement.
Fouling on VRMs
- Hot-gas duct fouling between preheater and VRM inlet
- Classifier fouling disrupting the fines separation
- Discharge-chute coating during high-moisture periods
Sonic horns on the inlet ducting and discharge chute keep the gas and material paths free of build-up.
Related terms
Related terms
- Raw mill, cement mill and coal millCement plants run three principal mills: raw mill (limestone+clay→raw meal), cement mill (clinker→cement), coal mill (raw coal→pulverised fuel for the kiln burner).
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.