Rapeseed Oil Refining Process

As one of the important edible oil varieties in the world, the refining process of rapeseed oil directly affects the stability, flavor and nutritional value of the oil. Modern rapeseed oil refining process systematically removes impurities through physical and chemical means, and realizes the quality upgrade from crude oil to finished oil. The following process flow, key parameters and technical points are analyzed.

I. Pre-treatment stage: laying the foundation for refining

Gross oil pretreatment

Rapeseed oil should be settled to remove surface foam, adjust the oil temperature to 25-35℃ and keep the oil surface smooth. At this stage, it is necessary to test the acid value of the oil, phospholipid content and other indicators, for example, if the acid value exceeds 3mg KOH/g, it is necessary to increase the intensity of alkaline refining.

Lye preparation

According to the characteristics of the oil, make 20-30°Bé lye at the ratio of 1kg caustic soda + 5kg water, and make sure the lye is completely dissolved by circulating pump. The concentration of lye should be dynamically adjusted according to the free fatty acid content, for example, for every 1mg KOH/g increase in acid price, the concentration of lye should be increased by 0.5°Bé.

Second, the core refining process: multi-dimensional quality improvement

1. Lye refining and deacidification: the key link of chemical neutralization

Operating parameters: after the oil temperature rises to 60 ℃, add lye in 5-10 minutes at an even speed, stirring speed from 20r/min to 60r/min, neutralization time control in 1 hour.

Soap foot separation: the temperature rises to 65 ℃ to stop stirring, standing 4-6 hours after the discharge of soap foot. Need to control the oil content of the soap foot is less than 3%, otherwise it needs to be centrifuged through the second recovery.

2. Soap washing: fine control of physical separation

Process points: After the oil is warmed up to 75 ℃, add 5% -10% of the oil weight of 80-85 ℃ hot water, stirring for 5 minutes, and then leave it for 3-4 hours. It is necessary to test the pH value of washing water to ensure that the soap content of the final grease is ≤50ppm.

Equipment selection: small workshops can use disc centrifuge, large factories use decanter centrifuge, the latter can handle up to 50 tons / hour.

3. Vacuum dewatering: protection of heat-sensitive components

Operating conditions: vacuum degree ≥ 700mmHg, temperature rises to 100 ℃ and then maintained for 30 minutes, so that the moisture content is reduced to less than 0.1%. Need to monitor the condenser water temperature to ensure that it does not exceed 35 ℃ to avoid oxidation of oil and grease.

4. Adsorption decolorization: targeted removal of pigments

Dosage of white clay: add 2%-4% active white clay according to the color of the oil, stir at 90-95℃ for 20 minutes. It is necessary to control the fineness of white earth to be above 200 mesh to avoid the blockage of filter residue.

Filtration system: adopt plate and frame filter or leaf filter, filter pressure control at 0.2-0.3MPa, oil transmittance after filtration should be ≥97%.

5. steam deodorization: double guarantee for flavor and safety

Process parameters: vacuum degree ≥755mmHg, temperature 220-240 ℃, direct steam intake 8-16kg/t-h, deodorization time 2-3 hours. Need to monitor the peroxide value of deodorized oil to ensure that ≤ 5mmol/kg.

Equipment requirements: deodorization tower should be made of 316L stainless steel, packing layer height of not less than 3 meters to ensure the oil film dispersion effect.

Third, post-treatment and quality control

Emergency cooling dewaxing: reduce the temperature of refined oil to 0-8℃, and filter it after 12 hours of crystallization, which can improve the low-temperature fluidity of oil and grease.

Add additives: add diatomaceous earth at the ratio of 0.1%-0.5%, after three-stage filtration, the acid value of the finished oil is ≤0.2mg KOH/g, and the peroxide value is ≤3mmol/kg.

Quality testing: It should meet the standard of GB/T 1536-2021, for example, the smoke point of first-grade rapeseed oil should be ≥215℃, and the solvent residue should not be detected.

Fourth, the direction of process optimization

Energy saving and consumption reduction: using heat pump technology to recover the waste heat of deodorized steam, which can reduce energy consumption by 15%-20%.

Utilization of by-products: Soap foot can extract fatty acids, filter residue can be prepared biodiesel, to achieve comprehensive utilization of resources.

Intelligent control: PLC system is introduced to monitor key parameters in real time, for example, acid price is detected online by near-infrared spectrometer, and the accuracy can reach ±0.05mg KOH/g.

The evolution of rapeseed oil refining process has always been centered on the three core objectives of “safety, nutrition and high efficiency”. With the application of supercritical extraction, molecular distillation and other new technologies, the future refining process will pay more attention to retaining the natural nutrients, and at the same time realize the precise control of the whole process through digital means, so as to promote the industry’s transformation and upgrading in the direction of green and intelligence.