In industrial edible oil production, soybean oil ranks among the world’s most consumed edible oils. To achieve high efficiency and quality, modern soybean oil plants rely on meticulously designed processes and advanced oil extraction machine. Among the available technologies, solvent extraction has become the mainstream method for large-scale production due to its higher oil yield and economic advantages.
Primary Oil Extraction Methods
Soybean oil is typically obtained through two main methods: mechanical pressing and solvent extraction. The resulting crude oil is subsequently refined to produce edible-grade soybean oil.
1. Mechanical Pressing (Expeller Pressing)
In this method, pretreated soybeans are fed into a screw oil press—a horizontal drum equipped with a rotating screw shaft. As the material advances, pressure gradually increases, forcing the oil out.
- Advantages: Continuous operation, simple process.
- Disadvantages: Friction generates heat, potentially causing protein denaturation, and leaves a high residual oil rate (5%–10%), reducing overall oil yield.
2. Solvent Extraction
This process uses a food-grade solvent, typically hexane, to dissolve the oil from soybean flakes. Through wetting, diffusion, and percolation, the solvent extracts nearly all the oil. The solvent is then separated and recovered from the oil-solvent mixture, leaving crude soybean oil.
- Advantages: Extremely low residual oil content (below 1%), high yield, better preservation of protein quality in the meal, and high automation.
- Applications: Ideal for large soybean oil mills efficiently processing high volumes of soybeans.
Why Solvent Extraction is the Preferred Method for Soybean Processing
Soybeans’ inherent characteristics make them better suited for solvent extraction than mechanical pressing:
- Low Oil Content: Soybeans contain only about 18%–20% oil, significantly less than oilseeds like peanuts or sunflower seeds. Mechanical pressing would leave substantial oil unextracted, resulting in economic loss.
- Higher Oil Yield: Solvent extraction recovers over 99% of available oil, enhancing profitability.
- Better Meal Quality: The process operates at lower temperatures, preserving the nutritional value of soybean meal—a valuable byproduct used in animal feed.
- Automation & Scalability: Modern solvent extraction plants are highly automated, reducing labor costs while enabling stable, high-yield production.
Key Components of Solvent Extraction Systems
A complete soybean oil extraction system includes:
- Pre-treatment section: Cleans, crushes, conditions, and flakes soybeans to optimize oil release.
- Extractor: Continuous extractors—such as rotary, ring, or chain designs—ensure uniform solvent contact with soybeans and achieve high extraction efficiency.
- Desolventizer-Toaster (DT): Removes solvent from spent soybean meal to produce roasted soybean meal.
- Solvent Recovery Unit: Evaporates and condenses solvent for reuse, minimizing operational costs and environmental impact.
- Oil Refining Section: Further purifies crude oil through degumming, neutralization, bleaching, and deodorization.
Selecting the Right Solvent
An ideal vegetable oil extraction solvent should meet the following requirements:
- High selectivity for oils at low temperatures.
- Low boiling point and latent heat for easy recovery.
- Good chemical stability, non-reactive with oil, meal, or equipment.
- Non-toxic, safe, and environmentally friendly.
- Cost-effective and available in bulk.
Due to its efficiency and mature recovery technology, hexane remains the most widely used solvent in industrial oil extraction.
Advancements in Oil Extraction Machinery
Modern oil extraction machine prioritizes energy efficiency, safety, and continuous operation in its design. Common extraction machine configurations include:
- Rotary (Disc) Extractors
- Ring Extractors
- Basket-Type Extractors
These systems offer advantages such as high throughput, minimal solvent loss, and seamless integration with downstream refining processes.
Environmental and Economic Benefits
Modern soybean oil plants utilizing solvent extraction benefit from:
Solvent Recycling: Up to 99% of solvents can be recycled, reducing operational costs and emissions.
Energy Efficiency: Advanced heat recovery systems minimize steam and electricity consumption.
By-Product Valorization: High-protein soybean meal can be sold as animal feed, creating additional revenue streams.
Ready to optimize your soybean oil plant?
As a leading oil extraction equipment manufacturer, Huatai provides custom solutions for soybean oil extraction, from individual oil extraction machines to complete solvent extraction turnkey projects. Contact us today for a free consultation and tailored plan to enhance your oil production efficiency and profitability.