Double Screws Compost Turning Machine

Equipment Introduction

The double-screws compost turner is a high-end, deep-layer turning and composting equipment specifically designed for trough-type aerobic fermentation processes. Its core structure consists of two parallel, counter-rotating screws shafts that reciprocate along the fermentation trough track, achieving integrated operations of deep lifting, crushing, mixing, oxygenation, and relocation of organic materials. It is the core fermentation unit for large and medium-sized organic fertilizer plants and manure harmless treatment bases.

I. Core Technological Advantages (Compared to Ordinary Drum and Single-screws Compost Turners)

1. Deep, Large-Span Turning and Composting with Extremely High Space Utilization: The effective turning depth can reach 1.0~1.8m, and the maximum suitable span for fermentation troughs is 6~11m. Under the same plant area, the material loading capacity per trough is increased by 40%, significantly reducing the construction cost of civil engineering fermentation troughs.

2. Dual-axis counter-current convection ensures thorough turning and uniform composting. Two screwss rotate synchronously in opposite directions, creating bidirectional convection. Anaerobic material at the bottom is completely turned to the surface, eliminating any missed turning spots at the tank edges. Material composting uniformity reaches over 95%, completely solving the industry pain points of single-axis equipment, such as one-sided accumulation and uneven stratified fermentation.

3. Strong oxygen supply and heat dissipation capacity significantly shortens the fermentation cycle. The screws blades powerfully break up the material crust, continuously opening oxygen supply channels within the pile, rapidly releasing the high fermentation temperature and maintaining a harmless high-temperature range of 55-70℃. The conventional fermentation cycle is shortened from 30-60 days to 15-25 days, and for sludge and low-organic-matter materials, it can be shortened to 7-14 days.

4. Suitable for high-moisture, viscous materials, preventing tangling and jamming. The double-screws variable-pitch wear-resistant blade design compacts materials at the feed end and loosens and spreads them at the discharge end. It features a built-in anti-stick scraper, allowing stable operation with high-moisture livestock manure and municipal sludge (50%~70% moisture content), preventing tangling with straw and clumping materials.

5. Low energy consumption, stable operation, and long service life. The dual-shaft balanced structure reduces overall machine vibration by 40%, with noise ≤75dB. Power consumption is 15%~20% lower than drum compost turners for the same processing capacity. The thickened carbon steel frame and high-manganese steel wear-resistant blades extend the machine's service life to 8~10 years, far exceeding the 5~6 years of ordinary models. 6. High degree of automation, suitable for large-scale continuous production. The PLC centralized control cabinet supports both manual and automatic modes, variable frequency speed regulation, fixed-point turning and automatic stop at both ends of the track. It can be integrated with solar fermentation chambers, bottom aeration systems, and transfer vehicles to achieve unattended continuous fermentation production.

II. Compatible Scenarios. It can be fully integrated with solar fermentation greenhouses, bottom forced aeration pipes, continuous discharge machines at the tank ends, and cross-tank transfer vehicles. The fermentation tank supports both continuous and batch discharge production modes, suitable for large-scale organic fertilizer production lines with an annual output of 30,000 to 200,000 tons, centralized livestock manure treatment centers, and municipal sludge treatment stations.

Equipment Structure

The entire machine consists of six core functional modules + an intelligent electrical control system + an optional transfer cart. The differentiating core component is the double-screws turning and turning assembly:

1. Overall Load-Bearing Frame: Thickened Q235 carbon steel welded integral gantry frame, surface sandblasted and anti-corrosion painted; the frame has walking support bases on both sides, and the double-screws turning and turning assembly is suspended in the middle. The structural strength can withstand the heavy impact of materials from a depth of 1.8m.

2. Track Walking Device: Composed of a walking variable frequency motor, transmission reduction gearbox, double-row walking sprockets, track load-bearing walking wheels, and track limit switches; the walking speed is steplessly adjustable from 0.5 to 2m/min. The track must be grounded to prevent leakage safety hazards.

3. Hydraulic Lifting Assembly (Standard Configuration for SFP-Y Hydraulic Model)

Independent 46# wear-resistant hydraulic oil tank, dedicated hydraulic pump motor, electromagnetic reversing valve assembly, high-pressure oil-resistant oil pipe, dual-side lifting cylinders, lifting support arm; the cylinder extension and retraction are controlled by an electronically controlled valve, precisely adjusting the depth of the double screws turning and tumbling mechanism. During maintenance, the entire screws can be raised for easy cleaning and upkeep.

4. Core Double screws Turning and Tumbling Assembly (Equipment Differentiation Core)

1) Dual Main Shaft Drive Unit: Two independent main motors + cycloidal pinwheel reducers, driving the left and right screws shafts to rotate synchronously in opposite directions;

2) screws Main Shaft and Blades: Two parallel high-manganese steel screws shafts, with variable-pitch wear-resistant screws blades welded to the surface. The blades are thickened for wear resistance and can be disassembled and replaced individually;

3) Anti-stick Auxiliary Scraper: An elastic scraper is installed close to the screws shaft to automatically scrape off high-moisture materials adhering to the shaft, preventing material entanglement and jamming.

5. Transfer Vehicle (Optional Equipment): Independent walking motor, transmission gears, load-bearing wheels, and lateral support frame; allows for lateral movement of the entire machine to other fermentation tanks, enabling multi-tank production and reducing total equipment purchase investment by over 40%.

Applicable Raw Materials:

The equipment can stably process all high-organic-matter industrial, agricultural, livestock, and municipal organic waste. Pre-treatment standards for raw materials: Moisture content should be adjusted to 50%~65%, and the carbon-to-nitrogen ratio to 20~30:1 before fermentation. For sludge and low-organic-matter waste, deep turning and turning can raise the pile temperature, compensating for insufficient organic matter in the fermentation process.

1. Livestock and poultry manure: Pig manure, cow manure, chicken manure, sheep manure, duck manure, and other livestock manure.

2. Agricultural and forestry straw: Corn stalks, wheat straw, rice husks, sawdust, peanut shells, and fallen leaves from gardens.

3. Industrial organic waste residue: Sugar factory filter mud, liquor lees, vinegar lees, medicinal herb residue, rapeseed cake, cottonseed cake, and other oilseed cakes and residues.

4. Municipal organic solid waste: Dewatered sludge from urban sewage treatment plants, sorted kitchen waste organic slurry, and landscaping pruning waste.

5. Edible fungi waste: Waste mushroom sticks and edible fungi cultivation residue.

Working Principle

The working mechanism of the double-screws compost turner can be summarized as a synergistic process of "dual-axis counter-rotation—three-dimensional turning—forced oxygenation and mixing":

1. Material Grabbing and Lifting Stage: The two helical shafts rotate at high speed in opposite directions. The helical blades penetrate deep into the bottom of the pile, using the axial thrust of the helical surface to push the bottom material upwards along the helical grooves. Due to the counter-rotation of the two shafts, the material is subjected to shear forces in two opposite directions during the lifting process, forming a "tearing-dispersion" effect, effectively breaking up agglomerated materials.

2. Scattering and Mixing Stage: After the material is lifted to the upper surface of the pile, it is scattered to a distance of 0.2–1.5 meters under the action of centrifugal force and gravity. During this process, the material achieves three-dimensional movement of upper and lower layer exchange, front-to-back displacement, and lateral diffusion, ensuring thorough mixing of materials at different fermentation stages and with different moisture contents.

3. Oxygenation and Cooling Stage: The turning and turning action loosens the dense material pile, creating a suitable porous structure. A large amount of outside air is drawn into the pile, maintaining the oxygen concentration within the ideal range of 8%–18%, meeting the metabolic needs of aerobic microorganisms. Simultaneously, turning and turning removes a significant amount of heat, rapidly reducing the pile temperature from above 65℃ to around 55℃, preventing the inhibition of microbial activity by high temperatures.

4. Quantitative Displacement Stage: Through continuous or intermittent movement of the traveling device, the equipment pushes the material longitudinally along the fermentation tank a certain distance (usually 1–2 meters per day) while turning and turning, achieving continuous feeding and discharging of the fermentation tank. Combined with the discharge device at the end of the fermentation tank, this creates a continuous fermentation operation.

Operating Methods and Procedures

(I) Pre-operation Preparation

Equipment Inspection: Before starting the machine, check all fasteners (bolts, nuts, couplings) for looseness; check the spiral blades for deformation, cracks, or abnormal wear; check the meshing state of the traveling wheels and guide rails; check the hydraulic oil level and the sealing of the oil pipe joints.

Electrical System Inspection: Confirm that there are no abnormal alarms in the PLC control cabinet and that the signals of all sensors (limit switches, temperature probes) are normal; check the motor insulation resistance to ensure the reliability of the main circuit and grounding circuit.

Material Status Confirmation: Measure the moisture content (target 50%–65%), temperature, and C/N ratio of the material to be turned. If the moisture content is too high, add dry material to adjust; if it is too low, spray an appropriate amount of water.

No-load Test Run: Start the main motor and run it under no-load for 3–5 minutes, observing whether the spiral shaft rotation direction is correct (dual shafts should rotate in opposite directions), and whether there is any abnormal vibration or noise; test the hydraulic lifting and traveling functions. (II) Operation Process Control

Parameter Settings: Set the turning depth (usually 2/3 of the pile height, approximately 0.8–1.5 meters), travel speed (3 m/min for loose materials, reduced to 1–2 m/min for highly moist and viscous materials), and auger speed (generally 50–100 r/min) according to material characteristics.

Turning Strategy: Adopt an "S-shaped route" or layered turning mode, with an interval of ≥24 hours between layers. For low-temperature environments in winter, extend the turning interval from 4–6 hours at normal temperatures to 8–10 hours, and appropriately reduce the turning depth to minimize contact between the pile and cold air.

Process Monitoring: Monitor motor current, hydraulic pressure, and equipment vibration in real time during operation. If the current exceeds 110% of the rated value, the frequency converter automatically reduces the speed; if it exceeds 150%, an emergency shutdown is triggered.

Foreign Object Handling: Immediately stop the machine and remove any hard blocks, stones, or metal foreign objects encountered. Operating the equipment while it is malfunctioning is strictly prohibited. 

(III) Post-operation cleanup

Raise the turning device to the highest position and move it to the stop position;

Clean the residual material on the auger blades and frame, and start the vibrating motor to assist in cleaning if necessary;

Turn off the main power and lock the control cabinet;

Fill out the equipment operation record, recording the turning volume, abnormal situations and handling measures.
Common equipment malfunctions and troubleshooting solutions

Applications in Organic Fertilizer Production Lines

The double-screws compost turner is the core fermentation equipment in an industrial organic fertilizer production line. It is typically located at the very beginning of the production process, undertaking the task of harmless and stabilizing the organic raw materials.

1. Typical Production Line Configuration

1) Annual production line of 10,000–50,000 tons of powdered organic fertilizer:

Raw material pretreatment (crushing/dehydration) → Ingredient mixing → Tank fermentation (double-screws compost turner) → Crushing → Screening → Packaging

2) Annual production line of 30,000–100,000 tons of granular organic fertilizer:

Raw material pretreatment → Ingredient mixing → Tank fermentation (double-screws compost turner) → Crushing → Screening → Granulation (disc/drum/extrusion) → Drying → Cooling → Screening → Coating → Packaging

2. Supporting Equipment

1) Fermentation Tank: Concrete or steel structure, width 2–11 meters, depth 1.5–3.0 meters, length designed according to production capacity (usually 30–100 meters);

2) Transfer Machine: Used for lateral switching of the double-screws turner between different fermentation tanks, achieving one machine for multiple tanks;

3) Aeration System: Perforated pipes are laid at the bottom of the fermentation tank, with forced oxygen supply in conjunction with a blower;

4) Temperature/Humidity Monitoring: Real-time feedback from online sensors, automatically starting and stopping the turner.

3. Process Integration

After fermentation and composting, the material is transported to subsequent stages by forklift or belt conveyor. Modern intelligent fermentation systems use AI algorithms to compress the fermentation cycle from the traditional 25 days to approximately 15 days, increasing nitrogen retention to over 92%, significantly improving the overall efficiency of the production line.

Supporting Fermentation Process

(Complete double-screws Tank Aerobic High-Temperature Fermentation Process)

I. Complete Fermentation Process Flow:

Organic raw material collection → Solid-liquid dehydration pretreatment (optional for high-moisture manure) → Straw auxiliary material crushing → Ingredient mixing (manure + straw + fermentation agent, adjusting moisture content to 50%~65%, carbon-nitrogen ratio to 20~30:1) → Uniform distribution in fermentation tank → Segmented timed turning and fermentation by double-screws turning machine → Discharge of matured material → Crushing and screening/granulation for further processing → Packaging of finished organic fertilizer.

II. Staged Fermentation Process Parameters (Adapted to the Advantages of double-screws Deep Turning)

Total fermentation cycle: 15-25 days, controlled in three stages, leveraging the deep turning capabilities of the double-screws to meet the process requirements of each stage:

1. Heating Stage (Days 1-5 of Fermentation)

Process Objective: Rapidly raise the temperature to above 55℃, quickly eliminating odors from the pile;

double-screws Turning Parameters: Shallow turning to a depth of 0.8-1.0m, turning once every 1-2 days;

Process Effect: Shallow turning quickly breaks up material clumps, introduces air to activate aerobic microorganisms, raises the pile temperature to above 50℃ within 16 hours, and completely eliminates anaerobic odors from the pile within 3-5 days.

2. High-Temperature Decomposition Stage (Days 6-15 of Fermentation) Process Objective: Maintain a high temperature of 55-70℃ for at least 7 days to completely kill insect eggs, pathogens, and weed seeds. double-screws Turning Parameters: Deep turning to a maximum depth of 1.4-1.8m, turning once every 2-3 days. Process Function: The double-screws deep turning completely brings the bottom anaerobic material to the surface for heat dissipation, stabilizes the high-temperature range of the pile, ensures complete material replacement throughout the entire pit, and fully aerates the deep material, achieving simultaneous decomposition and harmless maturation of the entire pit's material.

3. Cooling and Stabilization Stage (Days 16-25 of Fermentation) Process Objectives: The pile temperature gradually drops below 40℃, organic matter is completely degraded, and the material is dehydrated and stabilized. double-screws Turning Parameters: Medium-depth precise turning at a depth of 1.0-1.4m, once every 3-5 days. Process Benefits: Precise height-controlled turning accelerates moisture evaporation from the pile, ensures uniform material maturation, and enriches humus, providing high-quality and stable raw materials for subsequent granulation and powdered organic fertilizer processing.

III. Core Technological Value of the double-screws Turner in Fermentation Process

1. Full-cycle Adaptability to Turning Depth: Unlike ordinary drum turners with fixed heights, the double-screws turner can adjust the turning depth in real time according to the fermentation stage, shortening the fermentation cycle by 3-7 days and significantly improving material turnover efficiency in the fermentation workshop.

2. Flexible Heavy-duty Adaptability to Complex Materials: Under conditions of high-resistance materials such as high-moisture, viscous pig manure and municipal sludge, the double-shaft balanced structure has stronger load buffering capacity, resulting in a much lower equipment failure rate than single-shaft or drum turners, ensuring continuous fermentation production without interruption.

3. Improved Quality of Finished Organic Fertilizer: Deep, uniform, bidirectional turning ensures completely consistent material maturity, resulting in finished organic fertilizer with consistently high levels of organic matter, effective viable bacteria, and humus, meeting the national standard NY525-2021 for organic fertilizer. The fertilizer fertility and slow-release effect are superior to those of ordinary machines, making it more competitive in the market.
Equipment demand groups