Double-Shafts Paddle Mixer

Equipment Introduction

A double-shaft paddle mixer, also known as a double-shaft paddle mixer or double-shaft blade mixer, is a horizontal mixing device that uses two parallel, counter-rotating mixing shafts as its core, employing paddles to powerfully shear and convectively mix materials.

Double-shaft mixers are among the most widely used mixing equipment in industries such as organic fertilizer, compound fertilizer, chemicals, building materials, and feed. Their greatest advantages lie in their strong adaptability to high-moisture materials, high mixing efficiency, and large production capacity, effectively solving the pain points of traditional mixing equipment such as uneven mixing, inconsistent moisture content, severe dust generation, and material stratification. Unlike ordinary single-shaft or ribbon mixers, double-shaft mixers are characterized by high-moisture, non-clogging operation, fast mixing speed, and large batch production capacity, making them suitable for organic materials with high viscosity, high moisture content, and a tendency to clump, such as chicken manure, cow manure, and sheep manure.

In the fertilizer industry, double-shaft mixers are often referred to as "gravity-free mixers" or "gravity-free double-shaft paddle mixers"—when two opposing rotating shafts drive the paddles to rotate at high speed, the material forms a momentary weightless state in the overlapping area, as if it were in a weightless environment, achieving rapid and uniform mixing.

Equipment Structure

The double-shaft paddle mixer mainly consists of the following six systems:

1. Body (Cylinder/Tank): It has a horizontal W-shaped or twin-circular structure, with two overlapping teardrop-shaped cavities inside. The shell is mainly welded from plates and shaped steel, ensuring a tight seal and preventing dust leakage. The cylinder and parts in contact with materials are often made of stainless steel (304, 316L) or carbon steel (Q235).

2. Mixing Mechanism (Core Part): It consists of two horizontally arranged mixing shafts and multiple sets of specially angled blades mounted on the shafts. The two shafts are arranged parallel and symmetrically, with the blades arranged in a spiral pattern on the shafts. The blade material is selected from wear-resistant composite ceramics or wear-resistant alloys that are not prone to dust adhesion.

3. Transmission System: It consists of a motor, reducer, transmission gears, sprockets, and chains. A cycloidal pinwheel reducer or a ZQ series reducer drives the two rotors to rotate in opposite directions. The sprocket and chain adopt a three-row chain structure, providing high transmission torque, smooth operation, and low wear.

4. Feeding and Discharging Devices

1) Feed Inlet: Located at the top of the tank, material enters through this inlet.

2) Discharge Mechanism: The bottom adopts a full-length double-door structure for rapid discharge and minimal residue.

5. Auxiliary Systems

1) Atomizing Humidification System: Atomizing nozzles are installed at the top for even spraying of water or nutrient solution.

2) Sealing Device: The shaft end uses a combination of labyrinth and packing seals for excellent double sealing performance.

3) Flying Knife Device: For fibrous materials, a high-speed flying knife can be added for cutting before mixing.

4) Variable Frequency Speed ​​Control System: Operating parameters are flexibly adjusted according to material humidity and output.

6. Frame Section

The entire frame is constructed from high-quality carbon steel plates and channel steel, with all working parts mounted and fixed on the frame.

Working Principle

1. Power Transmission: The motor drives two main shafts to rotate synchronously in opposite directions at low speeds via a reducer and sprocket (industry average speed 30~46 r/min, SG600 is 36 r/min);

2. Three-Dimensional Convection Mixing: The staggered blades propel the material, simultaneously generating three types of motion:

1. Axial Motion: The blades spirally push the material forward and backward along the tank;

2. Radial Convection: The counter-rotating dual shafts cause the material to surge upwards between the two shafts, forming a gravity-free suspension layer;

3. Shearing and Crushing: The blades knead and break up clumps and coarse fibrous materials, eliminating the stratification of coarse and fine materials;

4. Synchronous Humidification and Conditioning: During the material mixing process, the top spray system evenly sprays water to precisely control the material's moisture content;

5. Continuous Discharge: The material is mixed and humidified while being uniformly pushed axially to the discharge port, achieving continuous and uninterrupted operation.

Raw Materials for the Equipment

This equipment is adaptable to a wide range of raw material forms, but the following basic characteristics must be met:

1. Form: Powdered, granular, short-fiber, and lightweight flake materials are all acceptable; for highly viscous materials such as filter cake and sludge, the sufficiency of the impeller thrust must be assessed.

2. Moisture Content: The moisture content should ideally be <15% when mixing dry powders; if humidification and granulation are required, the continuous twin-shaft mixer can adjust the moisture content to 20%–35% (e.g., for organic fertilizer raw materials). Excessive moisture content (>50%) can easily lead to sticking to the walls, clumping, and reduced mixing efficiency.

3. Particle Size: Raw materials should be pre-crushed and screened to prevent large stones, iron blocks, woven bags, and other foreign objects (>50 mm) from entering, which could jam the main shaft or damage the impeller. Examples of common raw materials:

1) Organic fertilizer: well-rotted chicken manure, pig manure, cow manure, straw powder, biogas residue, humic acid, functional microbial agents

2) Compound fertilizer: urea, monoammonium phosphate, potassium chloride, fillers (bentonite, talc)

3) Feed: corn, soybean meal, wheat bran, amino acids, mineral premix