How to Control the Temperature in a Ring Roller Mill for ATH

Ring‑roller mill generates cumulative frictional heat from roller‑ring compression‑shear grinding. For heat‑sensitive ATH, material temperature must be strictly kept ≤110 °C to avoid partial crystal‑water loss and LOI drop. Temperature control relies on water‑jacket cooling, airflow heat dissipation, stable operating parameters, feed‑condition management, monitoring & interlock protection. Without proper temperature management, even ring‑roller mill (lower heat than ACM mill) will cause ATH thermal degradation.

1. Water‑jacket cooling system (primary heat removal)

1. Install closed‑loop water‑cooling jacket on mill main housing and classifier housing. Cooling water circulates around grinding chamber to take away friction heat.

• Control cooling‑water inlet temperature: ideally 25‑32 °C; avoid high‑temperature circulating water in hot summer.
• Monitor inlet/outlet water temperature difference; typical ΔT:5‑12 °C. Large temperature rise indicates heavy grinding heat load.
• Maintain stable water flow and pressure; insufficient flow is a frequent root‑cause of over‑temperature.

2. Regular water‑jacket maintenance

• Clean scale and sediment inside cooling jacket and pipelines every month. Scale buildup drastically reduces heat‑exchange efficiency, even with sufficient water flow.
• Check for water leakage; prevent cooling‑water leakage into grinding chamber, which causes powder caking.
• In cold‑season shutdown, prevent water inside jackets from freezing and damaging housing.

Important note: Cooling jacket cools housing, not directly rollers. It removes accumulated chamber heat; it cannot fully compensate for extreme over‑load grinding.

2. Optimize system airflow for auxiliary heat dissipation

Ring‑roller mill runs under negative‑pressure closed‑loop airflow. Airflow carries away grinding‑zone heat together with powder.

1. Keep fan damper and pipeline unobstructed. Remove powder buildup inside air duct, cyclone and bag‑house; blocked airflow reduces heat removal capacity.
2. Do not excessively reduce total air volume for finer product. Too‑low airflow causes heat accumulation inside mill. Balance classifier speed and fan air volume.
3. Minimize hot ambient air ingress via leaking flanges and access doors. Hot incoming air raises overall system temperature. Seal all flange gaskets; replace aged gaskets periodically.
4. For high‑heat‑load fine‑grinding conditions: add optional circulating‑air cooling heat‑exchanger on return‑air pipeline to lower circulating air temperature.

3. Stabilize operating parameters to reduce heat generation

Most excess heat comes from improper operating conditions, not equipment defects.

1. Stable feeding rate
   Adopt loss‑in‑weight feeder to maintain constant feed rate. Over‑feeding causes over‑loaded grinding bed, more friction heat; under‑feeding leads to over‑grinding and temperature rise. Avoid feeding surges.
2. Control grinding pressure / spring tension
   Excessive grinding pressure increases roller‑ring squeezing friction and heat output. Do not blindly increase pressure to chase higher fineness or output. Match grinding pressure to target particle‑size.
3. Avoid long‑time overload operation
   When producing finer ATH grades (D97＜6 μm), heat generation rises sharply. Reduce hourly throughput accordingly; do not force the mill to run at full coarse‑grade capacity for fine ATH.
4. Prevent material stagnation inside dead zones
   Residual ATH staying in dead corners builds up heat and forms sintered agglomerates. Regularly clean material deposits on turntable, roller gaps and classifier housing.

4. Strict feed‑material pre‑treatment

Bad feed conditions worsen temperature drift.

1. Feed ATH must be pre‑deagglomerated by flash dryer, free moisture ≤0.3 %. High‑moisture sticky material cakes on rollers and ring surfaces. Caked material creates thick thermal‑insulation layers; heat cannot dissipate and local hot‑spots appear.
2. No large hard impurities entering grinding chamber; hard contaminants increase friction heat and vibration.

5. Monitoring, alarm and interlock protection

1. Install multi‑point temperature sensors: mill housing temperature, classifier housing temperature, finished‑powder outlet air temperature. Track powder outlet temperature as key index (target ≤110 °C).
2. Set PLC alarm threshold (e.g. 105 °C pre‑alarm; 110 °C high‑alarm). Configure interlock: trigger feed‑reduction or safe‑shutdown once temperature exceeds limit, to prevent mass production of thermally decomposed ATH.
3. Daily shift‑check: record cooling‑water pressure, flow rate, inlet‑outlet water temperature, mill outlet powder temperature. Trend‑chart analysis finds slow temperature drift before quality failure.
4. Periodically cross‑check finished‑product LOI value. Even if temperature reading looks normal, decreased LOI indicates hidden local over‑heating.

6. Maintenance points affecting temperature performance

1. Inspect roller‑ring wear condition. Severely worn liners cause unstable grinding bed, increased friction and heat generation. Replace worn wear‑parts in time.
2. Maintain bearing lubrication. Over‑heated bearings transfer extra heat into grinding chamber. Follow lubrication schedule; avoid insufficient or excessive grease filling.
3. Clean cyclone and bag‑house regularly. Powder buildup increases system resistance, reduces effective airflow and heat‑dissipation capability.

Common troubleshooting for temperature rise

Temperature control for ring‑roller mill in ATH processing is a combined system: water‑jacket cooling removes accumulated heat, airflow takes away heat via powder transport, stable operation parameters minimize friction‑heat generation, qualified pre‑treated feed avoids caking hot‑spots, and temperature‑interlock prevents thermal decomposition. Even with ring‑roller mill’s relatively low‑heat compression‑shear grinding mode, never run without functional water‑jacket cooling for ATH production.