Continuous solvent extraction plant

• 2017-01-16 16:55
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The process of solvent extraction results into a solution of the oil in solvent by diffusing solvent into the oil- bearing of raw materials. Different types of solvents can be used for this purpose, but among all those, hexane is extensively used in the solvent extraction due to its low boiling point.

Edible oil solvent extraction plant

Following are the different stages into which the entire extraction process is divided:
Preparation Of Raw Material (Seed Preparatory Section)
The oil content of soybean is 18 - 22%.These Soyabeans are firstly cleansed, graded and then finally fed into the cracker, where these are cracked into small pieces. Then the soybean can be sent to the cooking section to adjust the temperature and moisture.All this finished, the soybean will be transport to pressing section to get crude soybean oil.

Process Of Extraction In Solvent Extraction Plant
After the extraction process, the materials are fed onto a conveyor through a hopper. There, it forms a solid bed, not allowing solvent vapours to escape. Entire extraction process is carried out in different stages until almost 95% of the original content of oil is extracted from the raw materials. A temperature of 50 – 60℃ and a slightly low pressure as compared to atmospheric is maintained in the extractor for the processing.

Solvent extraction workshop

Extraction Process
In this extraction process, the raw materials are treated with hexane and the oil is recovered, resulting into a solution of oil in hexane called miscella. Condensation, evaporation and distillation of miscella are the process through which the absorbed hexane in the material is recovered. The reason due to which hexane is opted for the extraction process is its low boiling point (67℃) and high solubility of oils and fats in it.

Hexane, being a highly inflammable compound requires utmost care during processing. Thus, all those stages that involve high speed machineries like finishing, material preparation and bagging are carried out at least 50 ft. away from the main extraction plant.

Desolventising
The meal discharged from extractor contains 25% to 30% solvent. This solvent is removed after the meal is propelled in Desolventiser Toaster with the help of high-pressure jacket heating and low-pressure spurge steam. During solvent evaporation process equipment pressure will be slightly below the atmospheric pressure. Thus vapour losses and residual solvent in meal are minimized.

Distillation
According to the nature of the raw materials, the miscella has 10% to 18% content of oil. Firstly, the solvent is separated out from the mixture through carrying out distillation inside heat exchangers, maintaining vacuum conditions. After distillation, the miscella is fed to a flasher, where the content of solvent is reduced to 2%- 3% in the miscella. In an atomizer, on the top and at the jacketed column, hot oil is sprayed and an open steam is injected at the bottom for further processing. A temperature of 27 – 29℃ is maintained in the shell and tube condensers for condensing the solvent vapors. After condensing, final solvent content is removed and separated out from the oil.

Vent Vapour Recovery By Absorption
Non-condensable gases with mostly air get into the system during the processes like extraction, drying and distillation. These gases can cause damage to the system, and thus, have to be vented out. For this, an adsorption system is attached through which the vent gases are passed through. In this adsorption system, there is vegetable oil that completely adsorbs the solvent traces in the gases. A regular check on the oil has to be carried out for the presence of volatiles and as per the requirements, has to be rejected when these levels become perceptible.

Meal Finishing
De-oiled meal is finally transferred to the finishing unit, where it is cooled by air prior to bagging and packing.