Vertical Disc Mixer

Vertical disc mixers are specialized mixing equipment in the fertilizer industry, serving as core equipment in organic fertilizer, compound fertilizer, and blended fertilizer production lines for mixing multiple components. This equipment uses a vertical disc as a container, achieving thorough mixing of materials through the high-speed tumbling of stirring teeth or arms.

In the entire fertilizer production line, the vertical disc mixer is typically located after crushing and screening and before granulation, acting as a core mixing hub. Organic powder, nitrogen, phosphorus, and potassium fertilizer powder, trace elements, and microbial agents from the crusher are precisely homogenized here, providing stable and nutrient-uniform raw materials for the granulation process. The mixing effect of the vertical disc mixer directly determines the pelleting rate and particle strength in subsequent granulation. Compared to horizontal mixers, the vertical structure offers significant advantages such as smaller footprint, lower energy consumption, and easier maintenance. Because the materials are fluidized during mixing, the equipment operates smoothly with low noise.

Component composition and functional zoning

From the perspective of fertilizer production technology, the vertical disc mixer can be divided into the following functional units:

(I) Feeding Unit: Includes a top feed inlet and a top-mountable atomizing nozzle (for adding liquid inoculants or anti-caking agents). The feeding sequence should follow the principle of heavy to light and dry to wet.

(II) Mixing Unit: This is the core unit of the equipment, including the mixing disc, mixing shaft, mixing arms, and mixing teeth. The mixing teeth, driven by the mixing shaft, ensure thorough mixing of the materials. A three-dimensional mixing method is used, resulting in vigorous relative motion of the materials in three-dimensional space.

(III) Discharge Unit: Includes a discharge port located at the bottom of the disc. Combined with a pneumatic butterfly valve, rapid discharge can be achieved, significantly shortening batch processing time.

(IV) Power Transmission Unit: Includes an electric motor and a cycloidal pinwheel reducer. A belt pulley drives the cycloidal reducer, which has overload protection.

Production line roles and processes

Vertical disc mixers play a crucial role in the mixing stage of fertilizer production lines. The complete fertilizer production process is as follows: raw material crushing → screening → vertical disc mixing → granulation → drying → cooling → screening → packaging.

In the mixing stage, the vertical disc mixer performs several key tasks: precisely mixing the crushed organic powder with fertilizer powder according to the formula; uniformly dispersing trace elements, microbial agents, and other microbial components in the main material; uniformly spraying liquid microbial agents or binders through top atomizing nozzles; and providing stable and nutrient-uniform raw materials for the granulation process. The uniformly mixed material results in a higher pelletizing rate and more consistent particle strength after entering the granulator.

Hybrid Process and Stage Description

The mixing process of a vertical disc mixer can be divided into the following stages:

Feeding and Distribution Stage: Material falls into the rotating disc from the top feed inlet. Materials are added in order of heaviest to lightest, and dry to wet, with liquids evenly sprayed in through top atomizing nozzles.

Centrifugal Spraying Stage: The motor drives the disc to rotate at high speed, and the material is instantly lifted to a high position by the lifting plates or mixing teeth. Under centrifugal force, the material moves radially outward along the disc.

Gravity Diffusion and Mixing Stage: The material falls in a parabolic trajectory under the influence of gravity. Tens of thousands of collisions, penetrations, and diffusions occur between particles. The residence time of the material in the disc can be precisely controlled by adjusting the disc rotation speed and the discharge port height.

Discharge Stage: After mixing is complete, the bottom pneumatic butterfly valve opens, and the material is quickly discharged. The discharge speed is relatively fast, typically completing the discharge of a batch of material in 2-5 minutes.

Preparatory materials and requirements

Vertical disc mixers have specific process requirements for the feed materials. Material characteristics must be well understood: the viscosity, moisture content, particle size, and other properties of the material are essential. For highly viscous materials, the shape and angle of the mixing blades may need to be adjusted appropriately. Material particle size is generally recommended to be controlled within 5 cm; excessively large particles may damage the mixing blades. Material addition amount control is crucial: each machine has a rated processing capacity; exceeding this range will affect the mixing uniformity and may also cause equipment overload. The order of material addition should generally be followed by the main material in larger quantities, and then gradually added in smaller amounts of additives or auxiliary materials.

Operating procedures and key control points

Proper operation of a vertical disc mixer is crucial for ensuring mixing quality and extending equipment lifespan:

Pre-start Inspection: Check the equipment's exterior for damage and ensure all connecting bolts are tightened. Inspect the transmission system, including the motor, belts, chains, and gears. Check the mixing disc for deformation or wear, and ensure the mixing blades are securely fastened. Check the sensors, controllers, and other electrical components for proper functioning.

Correct Start-up Sequence: First, turn on the cooling or heating system (if applicable) to adjust the equipment temperature to a suitable operating range. Start the motor, allowing the disc to rotate slowly. Once the disc reaches a stable speed, gradually add materials. Never add materials before the equipment is started or before the disc's speed is stable.

Operation Monitoring: Operators must remain on duty and closely monitor the equipment's operating status. Observe whether the disc rotation is smooth and whether there is any abnormal vibration or noise. Pay attention to changes in motor current; excessive current may indicate that the equipment is overloaded. Monitor the material mixing process and adjust the mixing time and speed according to actual needs.