Rotary Screener Machine

The rotary screen is a core piece of equipment in the post-processing section of a fertilizer production line, responsible for separating finished products from recycled materials and grading the products. This equipment is typically deployed after granulation and drying processes and before packaging. In a complete organic fertilizer processing production line, the dried and cooled granular material is conveyed to the inlet of the rotary screen via a belt conveyor. After entering the rotating cylinder, the material is graded by centrifugal force and gravity.

The rotary screen can be used in conjunction with equipment such as compost turners, crushers, granulators, coolers, coating machines, and packaging scales. Adding a rotary screen after granulation and drying in an organic fertilizer production line is specifically for grading and screening—qualified granules are packaged, while unqualified large granules and powder are returned for re-granulation. Through this closed-loop screening-recycle system, the yield of the fertilizer production line can be significantly improved. The equipment operates stably and can operate continuously for 24 hours, matching the uninterrupted processing rhythm of an annual production line of tens of thousands of tons of organic fertilizer.

Component composition and functional partitioning

From a production process perspective, a rotary screen can be divided into the following functional units:

(I) Feeding Unit: Includes the feed inlet and guiding device. Material enters the drum evenly through this inlet. Feeding methods are diverse, including belt feeding, hopper feeding, or other methods.

(II) Screening Execution Unit: This is the core workstation of the equipment, including an inclined rotating drum and multiple layers of screens fixed inside the drum. The drum's interior is equipped with guide structures such as lifting plates. Depending on the grading requirements, the material can be divided into 1-4 sections from fine to coarse.

(III) Grading and Discharge Unit: Includes collection hoppers and discharge ports below each layer of screens. Material is discharged from different discharge ports according to different particle sizes. The coarse material section is equipped with chutes to directly transport coarse material to the conveying machinery.

(IV) Transmission and Drive Unit: Includes the motor, reducer, coupling, etc. The motor is connected to the drum assembly via the reducer, driving the drum to rotate around its axis.

(V) Sealing and Dust Removal Unit: Includes a sealing cover and a dust cover. The entire screening mechanism is designed inside a sealed dust cover, effectively preventing dust from escaping.

Production line roles and processes

Rotary screens play a crucial role in the screening process of organic and compound fertilizer production lines. The complete fertilizer production process is as follows: raw material pretreatment → fermentation → crushing → batching and mixing → granulation → drying → cooling → screening → coating → packaging.

In the screening stage, the rotary screen performs several key tasks: classifying the dried and cooled granular materials according to particle size; separating finished granules that meet the size requirements for packaging; returning large particles and powder that do not meet the requirements to the granulator for re-granulation or back to the batching system; and removing impurities such as stones and plastic flakes from the system. Through the return cycle established by the screening machine, the fertilizer production line achieves closed-loop material recycling.

Screening process and stage description

The screening process of a rotary screen can be divided into the following stages:

Feed Distribution Stage:The granular material to be screened enters evenly from the feed inlet at the higher end of the drum. The material is distributed across the cross-section of the drum by a guiding device.

Tumbling Screening Stage:The drum rotates at a uniform speed of 10-15 r/min. Under the action of gravity and friction from the inner wall of the drum, the material moves along the axis from the higher end to the lower end. Lifting plates on the inner wall of the drum continuously lift and throw the material down. Qualified particles with a diameter smaller than the screen mesh size pass through the screen mesh.

Grading and Discharge Stage:Materials of different particle sizes are separated into multiple grades by screens with different mesh sizes. The finished product is discharged from each discharge port. Large particles or impurities larger than the screen mesh size are discharged from the slag discharge port at the end of the drum.

Preparatory materials and requirements

Rotary screens have certain requirements for the feed material. Material temperature: The material entering the screen should be cooled, room-temperature granules to avoid damage to the screen from high-temperature materials. Material moisture content: The moisture content of the granulated and dried material should be controlled within the standard range; excessive moisture content will cause screen clogging. Material particle size: The feed particle size should generally be less than 300mm. Impurity removal requirements: Hard objects such as metal and stones should be removed by an impurity removal device before feeding to prevent damage to the screen.

Operating procedures and key control points

(I) Pre-start Preparation: Check that the drum is securely installed and that the anchor bolts are not loose. Check for any damage to the screen. Check the lubrication of the transmission device. Check that the sealing device is intact.

(II) No-load Start-up: The equipment should be started under no-load. Material can only be fed after the equipment is running normally.

(III) Operation Control: Adjust the feed rate according to the material characteristics and screening requirements. Observe the screening effect carefully and adjust promptly. Listen carefully for any abnormal noise from the equipment.

(IV) Shutdown Operation: First, stop feeding. Disconnect the power supply only after all material has been discharged from the drum.

Application effectiveness and industrial contribution

Rotary screening machines have demonstrated significant application effects in actual production. The equipment boasts high screening efficiency, equipped with plate or comb-type cleaning mechanisms that effectively prevent screen clogging regardless of the material's viscosity, wetness, or complexity. It has a large screening capacity; for the same size, a circular screen has a larger area than other shapes, resulting in a larger effective screening area. The equipment has low energy consumption, with motor power only 1/2 to 1/3 that of other types of screening machines. The screening cylinder is sealable, facilitating dust collection and creating a favorable working environment.

Target customer group

The main target audience for rotary screening machines includes: production managers and equipment procurement personnel of organic fertilizer, compound fertilizer, and blended fertilizer production enterprises; process designers of fertilizer production lines; managers of fertilizer production enterprises seeking to improve yield and product quality; and operation managers of composting and solid waste treatment projects.