Material blockage is one of the most troublesome problems in continuous production of fertilizer granulators. Once it occurs, it can lead to anything from machine shutdown and cleaning to damage to the die rollers and burnout of the motor. In fact, most blockages follow a pattern – by checking three dimensions: moisture, viscosity, and speed, and mastering emergency handling and preventative measures, the production line can be restored to smooth operation.
I. Cause Investigation: Moisture, Viscosity, Speed
1. Moisture Too High or Too Low
Granulation requires a suitable amount of liquid phase. Too high a moisture content (e.g., above 6%): The material becomes a thin muddy consistency, excessively compressed within the die holes, forming wet, sticky columns that cannot be expelled, eventually clogging the die plate. Too low a moisture content (below 2%): The material lacks lubrication, frictional resistance increases sharply, and the powder slips between the die rollers or sinters into hard lumps.
Troubleshooting Method: Hold a handful of material in your hand. If it can clump together and easily crumble when lightly tapped, it is suitable. If your palm is noticeably wet or it does not clump at all, the drying or water spray system needs adjustment.
2. Abnormal Viscosity
If viscous raw materials such as humic acid, molasses, or resin are added to organic or compound fertilizers, they will become like glue and adhere to the inner wall of the die cavity after the temperature rises. This is especially problematic when producing high-nitrogen formulas, as urea melts and recrystallizes at high temperatures, easily causing blockages.
Troubleshooting Method: Check the morphology of the blockage material—if it is black, gel-like, or has hard crystalline lumps, it’s generally a viscosity issue; in this case, reduce the proportion of high-viscosity components in the raw material, or add 3%-5% of anti-blocking agents such as bone meal or stone powder.
3. Speed Mismatch
If the feed rate is greater than the extrusion capacity of the granulator, the material in the die cavity will accumulate and compact, eventually causing blockages. Conversely, if the feed rate is too slow and the granulator is continuously idling, the residual material will harden due to heat, also clogging the die cavity.
Troubleshooting Method: Observe the ammeter—a continuous rise in current exceeding the rated value indicates that the feed rate is too fast; large fluctuations in current and intermittent idling indicate uneven feed. The variable frequency feeder should be adjusted to keep the feed rate synchronized with the spindle speed.
II. Emergency Handling: Stop-and-Stop Solutions
Minor Blockage (Partial Die Hole Discharge): Immediately reduce the feed rate and spray a small amount of water or oil (e.g., 1% waste machine oil) into the material to increase lubrication; continue running for 5-10 minutes, most blockages will clear themselves.
Severe Blockage (Complete Discharge): The machine must be stopped. First, open the granulation chamber door and remove accumulated material. For hard lumps inside the die holes, use an electric drill with a round steel brush to clear them one by one. Do not use a sharp steel chisel to forcefully knock them, as this may damage the die hole’s smoothness. If the die head is removable, soak it in hot alkaline water or a special cleaning agent for 12 hours before cleaning.
Plastic/Woven Bag Fabric Entanglement: Commonly seen in raw materials containing impurities. After stopping the machine, cut off the entangled material and check the cutter clearance.
III. Preventive Measures: Daily Maintenance and Process Optimization
Raw Material Pretreatment: Equip with a screening machine to remove stones and iron filings; control the moisture content of the powder entering the granulator between 3% and 5%; premix anti-caking agents for sticky materials.
Regular die re-molding: Re-molding with abrasive (oil bran + fine sand) every 200-300 tons produced restores the smoothness of the die cavity inner wall.
Equipment: Install a current limit for the pelletizer; exceeding the limit will automatically reduce feeding or trigger an alarm, preventing human error.
Temperature control management: For heat-sensitive raw materials, install a cooler after the mixer to ensure the material temperature entering the pelletizer is ≤45℃.
Sustained operational reliability in granulation systems depends fundamentally on matching equipment design to material behavior, whether the application involves a rotary drum granulator for high-volume spherical production, a disc granulator machine for precision pellet sizing, or a fertilizer compactor for dry fertilizer granules compaction without thermal input. Within the broader organic fertilizer granulator series, a poultry manure pellet machine exemplifies how specialized configurations address the unique challenges of high-moisture, high-fiber feedstocks through optimized die geometry and enhanced anti-adhesion coatings. Ultimately, every fertilizer granulator machine—regardless of granulation principle—benefits from rigorous upstream material conditioning, real-time process monitoring, and disciplined preventive maintenance. By institutionalizing the three-dimensional diagnostic framework of moisture, viscosity, and speed, coupled with standardized emergency protocols and regular die resurfacing schedules, producers can transform blockage mitigation from reactive firefighting into a predictable, science-driven operational discipline that safeguards equipment longevity and ensures uninterrupted production throughput.
Pelletizer blockage is not an intractable problem. Accurate troubleshooting starting with moisture, viscosity, and speed, combined with standardized emergency unblocking methods, and establishing a preventative maintenance system, can reduce the frequency of blockages by more than 80%.