General information about extraction

The extraction method of obtaining oil is the most economical in obtaining oil, which ensures maximum defatting of oily raw materials, allows obtaining high quality oil and defatted residue – meal.

For the defatting of sunflower or rapeseed seeds, a method is used in which a part of the oil is preliminarily released by pressing the seeds to obtain a cake, which then goes to its further, residual release due to extraction.

Soybean seed defatting uses a method in which all the oil is extracted from the pre-prepared seed. Soybean seeds go through the process of flaking (flattening) before extraction.

The extracted material (cake or petal) in the extraction plant passes through a magnetic separator, a loading screw and a receiving hopper, and only after that it enters the extractor. The temperature at the entrance to the extractor is 65 oC.

The basis of the extraction process is the ability of vegetable oils to dissolve in organic solvents. Nefras (H-hexane) is used as a solvent. Nefras is a mixture of hydrocarbons with a boiling point of 63-75 °С.

A solution of oil in a solvent is called a solution.

The extraction scheme used at the enterprise is extraction by the stepwise irrigation method. Nefras (hexane), passing through the moving layer of cake or petal inside the extractor, is saturated with oil and turns into mestel. The mixture (oil in it – 15…20%) is removed from the extractor and goes to distillation.

Distillation of the mixture is the distillation of the solvent (volatile substance from non-volatile oil) from it. A three-stage distillation scheme is used in the workshop on both lines.

During distillation, it is necessary to achieve rapid and complete removal of the solvent at lower temperatures, but during distillation, the boiling point of the solvent increases simultaneously with an increase in its concentration. Therefore, first the distillation takes place at atmospheric pressure, and then at discharge. Distillation is carried out by heating the place due to the heat released during the condensation of the steam coming from the boiler room.

The driven off solvent is condensed in heat exchangers due to heat exchange with circulating water, collected in a special container and returned to the extractor again. The oil, purified from the solvent, accumulates in two containers and is then fed into the tank for hydration and further storage. It is possible to transfer the oil for hydrogenation to the oil press shop and then for storage. Cooling before hydration takes place due to heating of the place sent to distillation, and after hydration due to circulating water. The oil temperature during shipment should not exceed 35°C

The extracted material passing through the extractor and losing oil turns into meal saturated with solvent. The meal defatted in the extraction process may contain from 25 to 40% solvent and water. The solvent in the meal is in a bound state and can be removed by the distillation method in the toaster, where it enters after the extractor.

Distillation of the solvent from the meal in the moving layer is carried out in the tank evaporators of the toaster, where the meal is treated with hot steam while stirring with a stirrer, and is also heated due to the condensation of steam in the shirts of the toaster. Distillation of the solvent continues for 55-60 minutes. The temperature of the meal at the exit from the evaporators is 100-105 °C. After the toaster, the meal enters the cooler (the cooler on the line with a capacity of 900 tons of seeds per day is part of the toaster), where it is cooled to a temperature not higher than 40 °C, while excess moisture is removed by air supplied by fans. For storage, toasted meal must have a moisture content of no more than 10%, a temperature of no more than 35 °C, and a residual solvent content in the meal of no more than 0.1%.

After leaving the toaster, the meal is moved by the system of transport elements to the meal hopper, from which it is shipped to the consumer.

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