Flat die pelleting machine: Protecting the activity of microbial agents in low-temperature granulation

fertilizer granulator Nov 3, 2025

The core challenge in biofertilizer production lies in ensuring that the granulation process does not destroy the activity of the microbial agent. Most functional bacteria (such as Bacillus subtilis and Trichoderma harzianum) are significantly inactivated at temperatures above 45°C. The flat die pelleting machine, with its low-temperature granulation capabilities, is a suitable choice for biofertilizer production. Its core advantage lies in its low-friction, no-additional-heat granulation process.

The flat die pelleting machine utilizes a vertical extrusion process, with the rollers and the die in contact with each other over a surface area rather than at points. This results in more uniform force per unit area, less frictional heat generation, and a temperature within the granulation chamber typically maintained at 35-40°C, well below the inactivation threshold of the microbial agent.

Furthermore, the machine does not rely on high-temperature conditioning or hot air conditioning; instead, it achieves granulation solely through the viscosity of the raw material and moderate extrusion, eliminating the need for additional heat input.

Furthermore, the flat die granulator’s speed is adjustable (typically 30-50 rpm). For biofertilizer raw materials with high microbial content, the speed can be reduced to below 30 rpm to further reduce frictional heat generation and ensure a microbial survival rate above 85%.

In practical applications, it is even more effective when used with a “room-temperature binder.” This eliminates the need for heating and dissolving the pellets, while also improving the pelletizing efficiency and complementing the flat die pelleting machine‘s low-temperature characteristics. This ensures the biofertilizer’s core function (microbial activity) while producing uniform pellets, meeting the dual requirements of “functionality” and “commerciality.”

Operational adjustment tips for ring die granulators in low-temperature environments

fertilizer granulator Nov 3, 2025

During winter in northern China or in low-temperature workshops (temperatures below 5°C), ring die granulators are prone to low pelletizing efficiency and poor pellet formation due to decreased raw material viscosity and insufficient lubrication of equipment components. Targeted adjustments are required to ensure proper operation.

During raw material processing, an electric heater can be added to the conditioner to preheat the raw materials to 15-20°C. This increases raw material molecular activity and viscosity, preventing low-temperature conditions that can lead to agglomeration and difficulty in extrusion.

Also, the steam saturation can be appropriately increased (from 80% to over 90%) to utilize steam heat to assist in heating the raw materials and prevent moisture from freezing at low temperatures, which can affect pelletizing. During raw material storage, insulation should be installed in the silo to prevent the raw materials from cooling too low during storage and avoid wasted energy from secondary heating.

Before operating the ring die granulator, preheat the ring die and rollers for 30 minutes. This can be done by running the machine at no load to allow frictional heating, or by wrapping the outer ring die with an electric heat tracer. The temperature should be set between 25-30°C to prevent the raw material from solidifying and clogging the die bore due to low temperatures. The lubricant should also be replaced with a low-temperature-specific lubricant (viscosity grade 46#) to prevent freezing and potentially blocking transmission components. The lubricant fluidity should be checked every two hours to ensure proper lubrication.

These adjustments can effectively mitigate the effects of low temperatures on the ring die granulator, ensuring a pellet formation rate above 95% and preventing material waste due to low temperatures.

Maintaining key components in fertilizer coating machines

fertilizer granulator Nov 1, 2025

Proper routine maintenance of fertilizer coating machines can reduce downtime and extend the coating machine life, with particular attention paid to key components.

First, maintain the conveyor belt. Fertilizer pellets easily accumulate. After daily downtime, clean the conveyor belt surface with a soft-bristled brush, especially around the edges to prevent residual pellets from clumping and scratching the belt coating. Check the conveyor belt tension weekly. If slippage occurs, adjust the tensioner immediately. Also, check the conveyor belt joints for cracks. Repair any cracks promptly to prevent uneven conveying and film shifting. For coating machines that frequently handles high-humidity pellets, apply anti-rust lubricant to the conveyor belt bearings monthly to prevent rust and seizure.

Second, clean the heat seal assembly. The heating tubes in the heat-sealing tunnel are prone to film residue. Wipe them every three days with a heat-resistant cloth. If the residue is hard, gently clean it with a small amount of alcohol. Be careful not to scratch the surface of the heating tube with hard objects to prevent damage to the temperature control sensor. Check the sealing performance of the heat-sealing tunnel weekly. If the tunnel door seal strips are deteriorating, replace them promptly to prevent heat loss that affects the heat seal and reduce energy waste.

Third, inspect the cutting blade. Check the cutting blade for sharpness weekly. If burrs appear, sharpen them with a whetstone at a 45° angle to ensure a smooth cutting edge. Also, clean the cutting blade holder to prevent film debris from getting stuck and causing deviations in cutting dimensions, which could affect packaging consistency. Check the cutting blade’s fixing screws monthly for looseness. Tighten them immediately if loose to prevent blade deviation during cutting, which could pose a safety hazard.