Complete Rapeseed Oil Plant: Pretreatment, Pressing, Extraction & Refining

1. 🌾 Pretreatment Section

Pretreatment directly impacts oil yield and quality. Core steps include:

• Cleaning: Removes dirt, stones, metal shavings and other impurities from rapeseed using magnetic separators, vibrating screens and stone removers. Protects downstream equipment, reduces wear and prevents foreign matter contamination.
• Flaking: Uses roller mills to crush rapeseed into thin flakes, maximizing surface area and completely disrupting oilseed cell structure for easier extraction in subsequent processes.
• Cooking: A critical step for hot pressing and pre-press solvent extraction processes. Typically uses a stacked cooker for moist cooking. Adjusts moisture and temperature of the flaked material to unlock rapeseed aroma, denature proteins, coagulate oils and prepare the material for optimal pressing conditions.

2. ⚙️ Pressing Process

Pressing methods are classified as hot pressing or cold pressing based on whether cooking is applied:

• Hot Pressing Process: Cooked flakes are fed into a screw press for extraction under high temperature and pressure. Features higher oil yield and rich oil aroma, but high temperatures may cause some nutrient loss.
• Cold Pressing Process: Cleaned rapeseed is directly pressed by a screw press or dedicated cold press at lower temperatures (e.g., 60-70°C) without heat treatment or only with low-temperature conditioning. Better retains natural nutrients like vitamin E, sterols and polyphenols, producing oil with light color and fresh flavor.
• Filtration: Crude oil from pressing is filtered using equipment such as plate-and-frame filters to remove solid meal residues.

3. 🔬 Solvent Extraction Process

For maximum oil yield, large-scale production often uses the "pre-press + solvent extraction" method:

• Pre-Pressing: Cooked flakes are first pre-pressed by a screw press to extract most of the oil, yielding a pre-pressed cake with residual oil content of approximately 12%-18%.
• Extraction: Pre-pressed cake is fed into extractors (rotary, annular, or drag-chain type) and soaked with solvents like n-hexane to dissolve residual oil.
• Solvent Recovery: The oil-solvent miscella is heated via evaporators and stripping towers to separate the solvent and obtain crude extracted oil. Solvent vapors are condensed and recycled. Wet meal is desolventized in a DTDC desolventizer to produce finished meal.

Extraction System Technical Parameters:

• Residual Oil Content: ≤ 0.5% (extremely high extraction rate)
• Solvent Consumption: ≈ 1.5 kg/t (very low consumption, high economic efficiency)
• System Recovery Rate: ≥ 99.5% (safe and environmentally friendly)
• Thermal Energy Efficiency: 10%–15% improvement (energy-saving and cost-reducing)

4. 🧪 Refining Section

Crude oil from pressing or extraction requires refining before consumption. Typical processes include:

• Degumming: Heated crude oil is treated with water or dilute acid to remove gum-soluble impurities such as phospholipids via hydration or acid refining.
• Deacidification: Food-grade sodium hydroxide solution is added, or physical distillation is applied, to neutralize and remove free fatty acids.
• Bleaching: Activated bleaching earth or activated carbon is added in a bleaching tower to adsorb pigments (e.g., chlorophyll), residual soapstock and trace contaminants.
• Deodorization: Under high temperature (220-240°C) and high vacuum, effectively removes odor-causing substances and peroxides, significantly improving the oil's smoke point and oxidative stability, achieving "zero trans fatty acids" and "zero glycidyl esters" standards.
• Winterization (Optional): Oil is cooled, crystallized and filtered to remove solid fats, improving clarity and appearance.

🎯 Process Comparison & Selection Guide