ZX204 Spiral Pre-Pressing Machine

The ZX series operates on the principle of mechanical pressing. It has a screw shaft within a press cage. As the screw shaft rotates, it conveys the pre - treated oilseeds through the press cage. The pitch of the screw gradually decreases, and the space between the screw and the cage bars also narrows. This causes the oilseeds to be compressed. The pressure generated forces the oil out of the seeds, which then seeps through the gaps in the cage bars. Before pressing, many models in the ZX series are equipped with a steaming wok. This allows for the adjustment of the moisture and temperature of the oilseed material embryo. For example, the appropriate moisture content for most seeds is around 8 - 12%, and the temperature can be adjusted to 60 - 80°C, which softens the seeds and improves oil extraction efficiency. The process from feeding the seeds, steaming and cooking them (if applicable), to discharging the oil and forming the cake is continuous and automatic in most ZX series models.

• Regular cleaning: After each use, clean the press cage, screw shaft, and other parts to remove any residual oilseeds, oil, and debris. This prevents the build - up of contaminants that could affect the performance of the machine and cause corrosion.
• Lubrication: Regularly lubricate all moving parts, such as the gears, bearings, and screw shaft. Use high - quality lubricants recommended by the manufacturer. For example, the gears may require industrial - grade gear oil, while the bearings may need a specific type of grease. Lubrication reduces friction, extends the lifespan of the components, and ensures smooth operation.
• Inspection of wear - and - tear parts: Periodically check parts like the cage bars, screws, and seals for signs of wear. Replace worn - out parts promptly. For instance, if the cage bars show significant signs of abrasion or the screws are damaged, they should be replaced to maintain the proper pressure and oil extraction efficiency.
• Checking the steaming wok (if applicable): If the machine has a steaming wok, check its heating elements, temperature sensors, and water - supply system. Ensure that the temperature and moisture adjustment functions are working correctly.
• Monitoring the gearbox: Some ZX series models have a gearbox cooler. Monitor the temperature of the gearbox and the cooler to ensure they are operating within the normal range. Also, check the oil level in the gearbox regularly and change the gearbox oil as recommended by the manufacturer.

Screw oil presses are highly versatile and can process most oil-rich seeds, including:

• High-oil seeds: Peanuts (45–50% oil), sesame (45–55%), sunflower seeds (40–50%), and rapeseed (35–45%).
• Medium-oil seeds: Soybeans (18–22%), cottonseeds (18–25%), and corn germ (30–40%).
• Specialty seeds: Castor beans, flaxseeds, palm kernels, and tea seeds.

The machine’s performance depends on seed preparation (e.g., dehulling for sunflower seeds, moisture adjustment for soybeans) and press settings (e.g., screw speed, cage tightness). Some models are optimized for specific seeds (e.g., cold-press screws for sesame), but most are adjustable for multi-seed use.

Oil yield depends on the seed type, preparation, and machine quality, but typical ranges are:

• High-oil seeds: 35–45% (peanuts), 30–40% (sunflower seeds) when properly conditioned.
• Medium-oil seeds: 12–18% (soybeans), 15–20% (cottonseeds) with optimal pressing.

Screw presses generally achieve 70–90% of the seed’s total oil content. For example, soybeans with 20% oil content yield 14–18% oil (residual oil in the cake is 2–6%). Hot-pressing often increases yield by 2–5% compared to cold-pressing due to better oil flow at higher temperatures.

Seed preparation: Proper cleaning (removing stones/dirt) prevents equipment damage; conditioning (moisture 8–12%, temperature 60–80°C) softens seeds for better oil release.
Screw design: The screw’s pitch, diameter, and compression ratio (ratio of initial to final volume) determine pressure. A steeper compression ratio (e.g., 1:8) increases yield but requires more power.
Operating parameters: Screw speed (50–200 rpm) affects residence time—slower speeds allow more thorough pressing but reduce throughput.
Maintenance: Worn screws or clogged cage slots reduce pressure and yield; regular cleaning and lubrication prevent inefficiencies.

Large-scale oil presses are engineered for efficiency, automation, and durability, with key differences including:

• Automation: Fully integrated with PLC (Programmable Logic Controller) systems to monitor and adjust parameters (pressure, temperature, feed rate) in real time. They often connect to upstream (cleaning, conditioning) and downstream (filtration, refining) equipment via conveyors for continuous flow.
• Multi-stage pressing: Use a series of screws with varying compression ratios (e.g., 1:6 to 1:10) to gradually increase pressure, maximizing oil extraction (residual oil in cake as low as 1–3%).
• Heavy-duty construction: Components like screws, press cages, and gears are made from high-strength alloys (e.g., 42CrMo steel) to withstand constant high pressure (up to 150 MPa) and reduce wear.
• Energy efficiency: Equipped with variable-frequency drives (VFDs) to adjust motor speed, heat recovery systems, and low-friction bearings to minimize energy loss.

Power consumption scales with capacity, but large-scale presses typically require 50–500 kW of electrical power, with additional energy for auxiliary systems:

• Main motor: 30–300 kW (depending on throughput) to drive the screw shaft.
• Conditioning systems: 10–50 kW for heaters and mixers.
• Conveyors and pumps: 5–50 kW for material handling.

Large-scale presses are part of integrated systems that include:

• Preprocessing: Magnetic separators (remove metal), destoners, dehullers, and conditioning tanks to prepare seeds.
• Extraction: The press itself, often paired with solvent extraction (for ultra-high yield) to recover residual oil from press cake.
• Post-extraction: Crude oil filtration (to remove solids), refining (degumming, neutralization), and storage in temperature-controlled tanks.
• By-product handling: Conveyors to transport press cake to drying and pelletizing systems (for animal feed) or further processing.

Integration is managed via PLCs, which synchronize all stages to maintain consistent flow—e.g., adjusting feed rate if the press slows down to prevent bottlenecks.

Consistency control: Maintaining uniform seed quality (moisture, purity) across large batches is critical—variations can reduce yield by 2–5%.
Energy costs: Fluctuations in electricity or fuel prices impact profitability; many plants use on-site renewable energy (solar, biomass) to mitigate this.
Regulatory compliance: Meeting food safety standards (e.g., EU REACH, FDA) for oil purity and worker safety (OSHA, ISO 45001) requires ongoing investment in testing and training.
Downtime risk: A single breakdown can halt the entire line, so plants often have backup presses or redundant systems for critical components.