Equipment Introduction

The double-shaft paddle mixer (industry abbreviation: SG double-shaft mixer, horizontal double-shaft mixer) is a horizontal, enclosed, forced mixing and conveying integrated equipment. Its core consists of two parallel, counter-rotating, synchronously rotating paddle shafts, integrating material mixing, humidification and conditioning, and enclosed conveying functions into one unit.

The equipment casing is a U/W-shaped tank, ensuring enclosed operation and preventing dust escape. Unlike single-shaft mixers, the double-shaft convection shear structure eliminates dead zones in mixing, achieving a mixing uniformity of 95%~98%. It is suitable for continuous production of high-moisture, high-viscosity, and coarse-fine mixed materials, and is widely used in industries such as organic fertilizer, compound fertilizer, solid waste treatment, building material dry powder, feed chemicals, etc. The Zhengzhou Huaqiang SG series is the industry standard model, featuring a continuous spiral + blade combination structure for the main shaft, a low-speed, high-torque design, and individually replaceable wear-resistant paddles, balancing high-intensity mixing with a long service life.

Equipment Structure and Components:

The entire machine can be divided into two main modules: the drive unit and the main body. These components work together to achieve efficient three-dimensional mixing:

1. Drive Unit

1) Motor: Provides the main power; power is matched to production capacity (commonly 11–30 kW).

2) Reducer: Reduces speed and increases torque; typically a hardened gear reducer.

3) Coupling and Synchronous Gear: The motor drives the drive shaft via a coupling. The synchronous gear on the drive shaft then drives the driven shaft, ensuring that the two main shafts always rotate in opposite directions at a fixed speed ratio, preventing impeller collisions due to speed differences.

2. Mixing Body

1) Horizontal Cylinder: Mostly U-shaped or W-shaped troughs, welded from high-quality carbon steel or stainless steel plates. The top has an inlet and liquid spray pipe, and the bottom has a outlet.

2) Dual Mixing Shafts: Two parallel main shafts are horizontally arranged at the bottom of the cylinder. Each shaft is equipped with a combination of continuous spiral and blade-type spiral impellers (or pure blade impellers). The impeller inclination angle is typically 45°–60°.

3) Blade Design: Utilizing a two-blade structure (base + replaceable end blades), only the small blades need replacement after end blade wear, eliminating the need to replace the entire shaft and significantly reducing maintenance costs.

4) Water/Liquid Spray System: Composed of an inlet pipe and nozzles, it can evenly spray water, steam, molasses, oil, or bacterial agents during mixing, achieving simultaneous humidification/greasing.

3. Support and Sealing

1) Bearing Housing: Supports the dual shafts and withstands radial and axial loads. Internal labyrinth seals or packing seals prevent dust from entering the bearings.

2) Frame/Base: Welded from channel steel or H-beams and fixed to the ground with anchor bolts.

4. Discharge Device: Equipped with a pneumatic or manual flap valve at the bottom, the wide-opening design allows direct access to the side of the cylinder, ensuring rapid discharge with minimal residue (typically <0.1%), effectively preventing cross-contamination between different batches.

Equipment Applications:

Working Principle of the Equipment

The working principle of the double-shaft paddle mixer is based on a dual mechanism of “convective mixing + weightless mixing”.

1. Double-shaft counter-rotation

The two mixing shafts rotate synchronously in opposite directions (opposite to each other) driven by a transmission device. Each shaft is equipped with blades arranged at a special angle, which rotate in opposite directions at the same speed.

2. Three-dimensional mixing

The blades drive the material to move in three directions within the mixing tank:

1) Radial motion: The material tumbles radially along the cylinder.

2) Circumferential motion: The material rotates circumferentially along the cylinder.

3) Axial motion: The material is pushed along the length of the cylinder.

3. Instantaneous weightless mixing (core mechanism)

At the intersection of the two rotors, a special weightless zone is formed. Within this zone, the material is in a state of instantaneous weightlessness, causing it to float regardless of its shape, size, or density. The material forms a flow layer within the mixer, generating convective circulation and interlocking shearing.

4. Two Modes: Parallel Flow and Counter-Flow

Double-shaft paddle mixers come in two modes: parallel flow and counter-flow.

1) Parallel Flow Mixing: The two shafts rotate in opposite directions, and the impellers also rotate in opposite directions, pushing the material in the same direction.

2) Counter-Flow Mixing: The two shafts rotate in opposite directions, but the impellers rotate in the same direction, causing the material to flow back and forth, which can extend the mixing time.

5. Solid-Liquid Mixing Operation

When performing solid-liquid mixing, the mixer should be started first, followed by liquid spraying. After spraying, continue mixing for 3-5 minutes.

6. Mixing Time and Uniformity

Generally, materials can be mixed uniformly within 40-120 seconds (0.5-2 minutes). The mixing uniformity (CV) is ≤5%, and continued mixing does not cause gradation or segregation due to differences in specific gravity or particle size.

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

Equipment Parameters

Location of Supporting Equipment in the Production Line

In the complete organic fertilizer production line, the process sequence is as follows: Raw material silo → Automatic batching machine → Double-shaft paddle mixer (adding water and microbial agents for mixing and conditioning) → Fermentation turning workshop / Extrusion granulator → Dryer → Cooling and screening → Packaging machine. Core function: To unify the moisture content of materials, break up clumps, and uniformly mix various raw materials, solving the problems of uneven fermentation and difficulty in granulation of high-moisture, coarse-fiber materials. It is the core pretreatment equipment of the entire production line. Multiple units can be used in parallel, suitable for ultra-large-scale organic fertilizer and solid waste treatment plants.

Standard Operating Procedures (Start-up and Shutdown Guidelines)

1. Start-up Sequence (Strictly Prohibited from Reversing)

① Start the motor under no-load;

② Feed material smoothly;

③ Turn on the spray water system; Requirements: Strictly prohibit starting under heavy load with material, to avoid motor stalling and impeller deformation.

2. Shutdown Sequence (Reverse Operation)

① Turn off the feed and stop feeding;

② Wait until the material in the tank is completely conveyed and emptied;

③ Turn off the spray water;

④ Turn off the motor.

Equipment Maintenance and Upkeep Details

1. Daily Maintenance (Per Shift)

1) Stop the machine and clean any residual material adhering to the tank and blades to prevent drying and clumping;

2) Add No. 4 calcium-based grease to all bearing housing lubrication points;

3) Check for clogged spray nozzles and leaks in the shaft end seals.

2. Regular Oil Changes (Use Fixed Oil Brand)

1) Reducer: Add No. 150~200 industrial gear oil, check the oil level regularly, and replace any deteriorated oil;

2) Main shaft gearbox: Immerse in No. 15~22 machine oil for lubrication;

3) Grease grade can be slightly adjusted according to local winter and summer temperatures.

3. Periodic Overhaul

Weekly: Tighten blade bolts, foundation bolts, and coupling fixing bolts; Monthly: Check blade wear; Quarterly: Inspect seals, chains, and sprockets; Annually: Disassemble the machine for a comprehensive inspection of main shaft deformation and housing corrosion. 4. Replacement Standard for Wear Parts: When the blade end plates are worn thin, the stirring output decreases, or the mixing is uneven, the blades can be replaced individually without replacing the entire shaft, resulting in low maintenance costs.

Common Equipment Faults, Causes and Solutions

Target Customers for this Equipment:

1. Organic fertilizer/bio-fertilizer/compound fertilizer manufacturers (plants with an annual production capacity of 10,000 to 500,000 tons);
2. Livestock and poultry breeding groups’ manure resource utilization workshops;
3. Municipal sludge and agricultural and forestry straw solid waste resource utilization enterprises;
4. Dry mortar and building material clay product processing plants;
5. Feed premix and chemical powder raw material processing enterprises;
6. Environmental protection equipment engineering companies (procurement of complete organic fertilizer production line equipment);
7. Organic waste disposal sections of garbage and sewage treatment plants;
8. Organic fertilizer equipment distributors and complete production line customization service providers.

Core Advantages of the Equipment:

1. High Mixing Efficiency: Dual-shaft convection eliminates dead zones, reducing mixing time by over 40% compared to single-shaft equipment, achieving a uniformity of 95%+;
2. Three Functions in One Machine: Mixing, humidification, and closed conveying are completed simultaneously, simplifying production line processes;
3. Suitable for High-Moisture and Difficult-to-Handle Materials: Specifically optimized for viscous, coarse-fiber, and semi-wet agglomerated materials;
4. Sealed and Environmentally Friendly: Fully enclosed tank, preventing dust leakage, with integrated dust suppression spray;
5. Low Maintenance Costs: Independently detachable and replaceable paddles, resulting in a long overall lifespan for the main shaft;
6. Continuous Automation: Can be integrated with belt conveyors and automatic batching systems for unmanned continuous production;
7. Strong Installation Adaptability: Horizontal structure with a compact footprint, suitable for indoor factory overhead installation, and adaptable to the retrofitting of new and old production lines.

Double-shaft paddle mixers/Twin-shaft mixers are highly efficient core equipment in the modern powder and granular material mixing field. Through a unique mechanism of counter-rotating twin shafts, three-dimensional impeller scattering, and instantaneous homogenization of the weightless zone, they achieve mixing precision far exceeding that of traditional single-shaft equipment in a very short time. Whether for raw material premixing and humidification in continuous fertilizer production lines or for high-precision batching in the intermittent feed and food industries, this equipment meets the needs of large-scale industrial production with stable performance, low residue levels, and convenient maintainability. Proper installation accuracy, reasonable control of raw material moisture content and filling rate, and implementation of standardized maintenance are key to ensuring its long-term efficient operation.