How to solve blocking issues in LFP grinding mills

Mill blockage (material clogging) is a common fault during LFP dry de-agglomeration. It usually occurs at feed inlet, grinding chamber, classifier wheel, air duct or powder discharge section. Blocking is mainly caused by material agglomeration, high moisture, unstable feeding, improper airflow and oversized incoming clinker. Below is the root cause analysis, troubleshooting and preventive measures for JCSM air classifier mill and JFJM fluidized bed jet mill.

1. Common root causes of mill blocking for LFP

Raw material side

1. High moisture of calcined LFP clinker
   Moisture makes fine particles sticky. Powder adheres to chamber walls, accumulates and gradually narrows flow passages, eventually forming blockages. LFP absorbs moisture rapidly in humid environments.
2. Large hard sintered chunks or foreign debris
   Uncrushed big clinker blocks the feed screw or grinding chamber inlet. Hard agglomerates may jam the classifier wheel.
3. Excessive fine submicron fractions
   Over-grinded superfine powder has strong cohesive force, easy to stick and bridge inside the mill.

Process and parameter side

1. Overfeeding / unstable feeding
   Feed rate exceeds the mill’s processing capacity. Material accumulates faster than airflow can carry fine powder out. Loss-in-weight feeder drift is a typical trigger.
2. Mismatched airflow or classifier speed

• Too low airflow: insufficient lifting force to carry qualified powder out of the grinding zone; powder accumulates inside.
• Too high classifier wheel speed: cut point becomes extremely fine, material circulation load rises sharply, internal powder buildup occurs.

3. Improper pre-treatment
   No pre-sieving or magnetic separation; hard impurities enter the mill and jam rotating components.

Equipment & environmental side

1. Static adhesion
   Static causes LFP powder to stick to ceramic liner, classifier wheel and pipeline inner walls. Layer-by-layer deposits reduce flow cross-section.
2. Cold wall condensation
   Pipeline or chamber temperature below dew point, water condenses on surfaces and powder sticks.
3. Dust collector bag clogging
   High differential pressure on pulse dust collector increases system backpressure; negative pressure in the grinding chamber drops, and powder cannot be transported out smoothly.

2. Rapid troubleshooting when blockage occurs

Safety reminder: Before opening the mill for cleaning, activate E-stop, cut power, perform LOTO lockout-tagout, release pressure and purge residual powder. Never open the chamber while the machine is running.

1. Stop feeding immediately, then stop the main grinding rotor/classifier.
2. Check differential pressure of dust collector first. If bag clogging causes backpressure, perform pulse cleaning or replace filter bags.
3. Check feed inlet: remove oversized chunks or caked wet material.
4. Inspect classifier wheel for powder caking; clean adhered LFP deposits.
5. Check air ducts and cyclone inlet for accumulated powder.
6. After cleaning, test run at low feed rate, gradually increase load while monitoring pressure and PSD.

3. Preventive solutions by equipment type

JCSM air classifier mill (mechanical classifier mill)

Most blockages happen at grinding chamber outlet and turbine classifier wheel.

1. Pre-crush + vibrating sieve before feeding, remove clinker >1–3 mm.
2. Use loss-in-weight feeding with interlock: if chamber pressure rises, PLC automatically reduces feed rate.
3. Balance rotor speed and classifier speed. Avoid excessively high classifier speed that increases internal circulation load.
4. Maintain stable induced draft fan airflow to keep proper negative pressure.
5. Regularly inspect classifier wheel surface for powder caking; install periodic air purge for the classifier zone.

JFJM fluidized bed jet mill

Blockage usually appears in feed nozzle or fluidized bed chamber.

1. Ensure compressed air is dry (dew point ≤ -40 ℃). Wet powder easily adheres to nozzles.
2. Keep jet pressure stable. Low jet pressure weakens fluidization and causes powder deposition at the bottom.
3. Control feed rate strictly; do not feed material faster than jet grinding and classification can handle.
4. Install anti-static lining and full grounding to reduce wall adhesion.

4. Long-term process optimization measures

1. Raw material control
   Keep incoming LFP moisture below 0.2%. Store calcined clinker in low-humidity silos (RH <40%).
2. Optimize pre-treatment
   Vibrating sieve + pre-magnetic separator to remove large chunks and tramp metal.
3. Parameter interlock strategy
   Set pressure difference alarm for grinding chamber. When pressure differential exceeds threshold, the system automatically cuts feeding to avoid full blockage.
4. Static and anti-sticking design
   Full equipotential bonding and grounding; smooth ceramic-lined surfaces to minimize powder adhesion.
5. Regular maintenance schedule
   Periodic inspection and cleaning of classifier wheel, nozzles, cyclone and pipeline deposits. Prevent thin powder layers from building up into thick cake.
6. Avoid condensation
   Insulate mill body and air pipelines; control carrier gas dew point.

5. Quick checklist summary

✅ Raw material: low moisture, no large chunks
✅ Feeding: loss-in-weight feeder with pressure interlock
✅ Air circuit: stable negative pressure, dust collector differential pressure monitoring
✅ Parameters: avoid over-high classifier speed and overfeeding
✅ Hardware: anti-static, ceramic lining, regular cleaning of classifier wheel / nozzles

LFP mill blockage is mostly caused by wet/sticky powder, oversized feed material, overfeeding, mismatched airflow and powder static adhesion. The solution combines raw material control, pre-sieving & magnetic separation, interlocked loss-in-weight feeding, airflow tuning, static elimination and periodic maintenance. Real-time differential pressure monitoring is the most effective early warning method to prevent serious blockage in both JCSM and JFJM mills.