Solvent Extraction Plant
The solvent extraction plants are used where oil is
extracted from oil seeds like soybean, sunflower, cottonseed, other oil
seeds and oil cakes like mustard cake, groundnut cake and rice bran.
Plant Capacity :
- Preparatory Section
- Extraction Section
- Conditioning Section
- Distillation Section
- Recuperation Section
Upto 2500 TPD
The plants are ergonomically designed and are energy efficient, consistent
in output quantity and quality, operator friendly and generate less
effluent. The level of plant automation depends upon client requirement.
These plants are more efficient than the traditional hydraulic press, ghani
or continuous screw.
- Continuous operation
- Low oil residue in extracted meal
- Low power and steam consumption
- Low solvent loss
- Low sediment in the extracted oil
- Extractors with automatic feeding function
Process Description for Continuous Solvent Extraction Plant
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.
Following are the different stages into which the entire extraction
process is divided:
Preparation Of Raw Material (Seed Preparatory Section)There are 3
different types of Soyabeans viz. brown, yellow and black with 18 - 22%
content of oil. These Soyabeans are firstly cleansed, graded and then
finally fed into the cracker, where these are cracked into small pieces. The
gap between the cracker rolls should be adjusted in such a way as to avoid
powder of the beans.
As to separate the hulls, a hull- separator is attached to the cracker
machine into which the material is received. The broken meats with some
content of hulls is carried on the vibratory deck into the hopper whereas,
the powdery material called chuni is collected at the lower most
A current of air is passed for minimizing the content of hulls in the
material. After this, the material is passed into the cooker conditioner for
A jacket steam along with injection of open steam is applied for complete
conditioning of the beans. There is a flaker machine into which the
conditioned meats are fed and then processed through a pair of smooth rolls
rotating at the same speed in opposite direction. Compression springs or
hydraulic power pack is attached in the rolls due to which the thickness of
flakes is adjusted. Generally, the thickness of the flakes coming out of the
machine is about 0.25 to 0.28 mm. After flaking, the Soyabeans are fed into
the expander for preparing the cakes and collets. In order to remove the
moisture from the collets generated from the expander, these are fed in
dryer cooler and cooled up to the extraction temperature. Finally, the
cooled collets free from moisture are fed to the extraction system through
Process Of Extraction In Solvent Extraction PlantAfter 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
oC and a slightly low pressure as compared to atmospheric is
maintained in the extractor for the processing.
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 (67oC) 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.
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
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 29oC
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.
De-oiled meal is finally transferred to the finishing unit, where it is
cooled by air prior to bagging and packing.