Double roller granulator 

The double-roller extrusion granulator is a key piece of equipment for compound fertilizer granulation, characterized by advanced technology, rational design, a compact structure, innovative utility, and low energy consumption. In organic fertilizer production lines, it is used to process fermented materials and represents a new generation of compound fertilizer granulation equipment. It employs a room-temperature, drying-free process to achieve granulation in a single step. The equipment requires low investment, yields quick returns, and offers strong economic benefits, while the complete system features a compact, scientifically sound layout.

As a typical dry granulation device, the double-roller extrusion granulator forms granules by directly utilizing the material's inherent crystal water or a minimal amount of moisture, reducing energy consumption by 30%–50% compared to traditional processes. The resulting granules possess high strength and a smooth finish; furthermore, because the process avoids high temperatures, the activity of biological bacteria within the material remains fully preserved.

Equipment Structure:

The core structure of the twin-roll extrusion granulator consists of a pair of counter-rotating rolls. The overall system comprises the following components:

Main Unit: Utilizing the principle of twin-roll extrusion, this unit shapes powdered materials into uniform granules and serves as the production line's core equipment. Its key components are two extrusion rolls rotating synchronously towards each other, featuring custom-designed hemispherical mold cavities evenly distributed across their surfaces.

Feeding System: Materials are fed quantitatively and uniformly between the rolls via a screw feeder or vacuum loader; maintaining a stable feed rate is crucial to preventing clogging.

Crushing and Screening System: The extruded material sheets (cakes) are crushed and broken down, then classified using a vibrating screen. Granules meeting specifications proceed to the next stage, while oversized particles or fines are recycled for re-granulation.

Conveying System: Transports material from the fermentation workshop to the granulation equipment, enabling automated, continuous production.

Screening Equipment: Screens the finished granules to separate out non-conforming particles, thereby ensuring product quality.

Raw materials for equipment:

The double-roller extrusion granulator is suitable for a wide range of organic fertilizer raw materials:

Livestock and poultry manure: Fermented organic materials such as chicken, cattle, and pig manure.

Plant stalks: Fermented plant stalks.

Organic waste: Mushroom residue, humus soil, etc.

Organic-inorganic composite materials: Mixtures of fermented chicken manure with urea, superphosphate, and other additives in specific proportions to produce organic-inorganic compound fertilizers.

The moisture content of the raw materials is typically controlled to below 10%. The double-roller extrusion granulator offers exceptional versatility, allowing it to flexibly accommodate various organic and inorganic raw materials.

Working principle of the equipment:

The working principle of the double-roller extrusion granulator is based on the theories of external force extrusion and molecular bonding. Fermented and pulverized organic fertilizer materials—in the form of dry or fine powder—fall evenly under gravity into the gap between two extrusion rollers. Driven by a hydraulic system or a spring-loaded pressure mechanism, the pressure within the roll gap becomes extremely high, forcing the loose powder particles to shift and rearrange while expelling air from between them.

Under this high pressure, the distance between material particles is drastically reduced, generating intermolecular van der Waals forces; some material even undergoes lattice deformation, enabling cold-press forming. As the rollers rotate, the material is forcibly extruded, compacted, and released, forming uniform granules in a single pass. The entire process requires no added moisture or binders, relying on purely physical forming that preserves the fertilizer's nutrient content. Once the material passes the narrowest point of the roll gap, the pressure is instantly released, and the formed sheets or granules detach naturally under the influence of gravity and centrifugal force.

The equipment's fermentation process:

In organic fertilizer production, the fermentation and granulation processes are closely integrated:

1. Initial Fermentation: Livestock and poultry manure is mixed with appropriate additives and fermented in fermentation pits. Achieving full decomposition through fermentation is a critical step in organic fertilizer production.

2. Post-Fermentation Processing: The fully decomposed material undergoes crushing and screening. Once crushed and blended, the powdered organic fertilizer feedstock is ready for the granulation stage.

3. Extrusion Granulation: The processed organic fertilizer powder is evenly fed between two rollers by a feeding mechanism and extruded under high pressure into a high-density, strip-like material cake. After exiting the discharge port, the cake is crushed and screened to produce the final granules.

The combined use of trough-type turning equipment and double-roller extrusion equipment enables a seamless transition from fermentation to granulation. Material that has completed fermentation can be conveyed directly to the double-roller extrusion unit for granulation, thereby minimizing material loss and time wastage associated with intermediate handling. The forming rate exceeds 95%, resulting in granules that possess high strength and resistance to breakage.

Application of the equipment in the production line:

The double-roller extrusion granulator is a core piece of equipment in organic and compound fertilizer production lines. The typical production process is as follows:

1. Qualified raw materials are added to a high-efficiency mixer according to the required formulation and mixed thoroughly.

2. The mixture is conveyed to a disc feeder; during this process, any ferrous impurities are removed.

3. Material from the disc feeder enters the extrusion granulator evenly, where it is forced between two pressure rollers and compressed into sheets.

4. The sheets are broken into fragments by a coarse crusher located beneath the rollers and then screened; material retained on the screen undergoes further crushing and screening.

5. Semi-finished material is conveyed to a finishing screen; undersized particles are returned directly to the disc feeder, while oversized particles are pulverized before being returned.

6. Qualified screened products are conveyed to an automatic packaging scale for weighing, packaging, and warehousing.

This equipment can be used as a standalone unit or integrated with other machinery to form small- or large-scale production lines, enabling continuous, mechanized production.