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Vegetable oil production from sunflower seeds by oil pressing method

One of the options to produce the vegetable oil from the seeds of oil-yielding plants is extraction or pressing of the raw input material — oil seed meal — with the use of M8-MShP screw-type extruders (oil expellers).

Principle of operation of the oil expeller is as follows:

The raw material (sunflower seeds) is charged into the oil mill receiving hopper by a screw conveyor from the grain elevator. Then the seeds are fed into the separator where they are cleaned from contaminants and metallic impurities. After that the seeds are hulled, ground and, when hot pressing, dried and heated in the oil seed cockers of special design, and then conveyed to the oil expeller.

Pre-ground, having passed the thermal treatment and pre-heated up to the required temperature, the oil seed meal of oil-bearing crops (60-90 °C) is pressed in  oil expeller. The oil is pressed in the extracting box consisting of several cages (stages).

The extracting box has four stages (I-II-III-IV). While the material is passing through the stages I to IV the pressure rises, i.e. each cage (chamber) is less in volume then the previous one. Therefore, when the oil seed meal passes through the stages the screw shaft (worm) compresses and squeezes it out through the gaps of laths in the extracting box. The oil pressing itself occurs at the stage III and IV.

With a view to increase the material upthrust in the extracting box a cone is mounted in the end of the chamber. By setting up the gaps between the cone and the cone ring the thickness of the oilcake is adjusted.

The pressed out oil flows down through the gaps in the extracting box plates into the oil collector, and the oilcake shells get to the screw conveyor inlet and are discharged beyond the unit location. The collected oil is pumped over to the place of destination.

The oil mill equipment can be mounted on a common base plate thus facilitating transportation, installation and commissioning of the equipment (the shipment by trucks is possible).

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Vegetable oil production by hot pressing method

Oil pressing is a process of pressing decorticated (dehulled), ground, dehydrated and heattreated seeds of the oilyielding plants (oil seeds meal) in the oil expeller for final extraction.

Hot pressing is a process consisting of preheating of the oil seed meal in the roaster and oil pressing in the screwtype oil presses.

Preheating of the oil seed meal ensures that a minimum level of the residual oil content in the oilcake is achieved within 6 % after dual hot pressing.

At the same time the process of hot pressing ensures that the lowest rate of wear of the equipment is reached as the oil seed meal has the least abrasive abilities in relation to quickwearing parts of the press. First of all it relates to the components of the worm and pressing cage, where the oil is actually produced.

The hot press oil has a rich, more saturated tone color and a specific pleasant odor. The oil produced by hot pressing shall, if necessary, be refined in order to reduce hyperacidity occurred when heating in roasters.
PRODTECHMASH oilpressplant offers complex solutions for production of vegetable oil from the seeds of oilyielding plants, such as sunflower, soya, and rape by ONE or TWO stages of hot pressing in continuous closed cycle.

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Production of the vegetable oil from sunflower oil seeds by cold pressing technology

Vegetable oil is made from seeds of the oil-bearing crops, such as sunflower, corn, soya, safflower, cotton etc. The quality of oil, first of all, depends on the seeds quality. Oil seeds should have a sufficient oil content, their moisture not to exceed 6 % (otherwise the oil would appear to be too aqueous), and it also depends on maturation degree of the seeds that should have enough light and heat. Empirically it is quite clear that the higher oil content in seeds, the higher oil yield shall be.

The “cold” oil pressing method is one of the processes the vegetable oil is produced. Choosing of this method gives less oil yield as a result, however the cold oil pressing method, or so-called “extra virgin” ensures all useful elements and vitamins are retained in the final product.

Equipment used for the vegetable oil production by the cold pressing method

The cold oil pressing method requires less high-value equipment comparing to the other processes of oil production. This technology requires a screw-type oil mill that must include an oil press.
They are available of various types. The difference is that of tonnage capacities of the product to be processes, of the oil content in the oilcake tablets, and of the power consumption. As to the low-capacity oil mills (oil press mill) it is useful to choose a worm mill as simple as possible, which is capable, for example, of processing about 6-10 tons of the product per day. For large oil mills it is recommended to choose the oil pressing plant of a high output.

Features of the oil mills designed for cold pressing:

  1. the pressing is done at low temperatures only. The product is extracted by the worm press and extracting box (cage) unit. The oil produced is filtered from the sediment;
  2. pressing at lower temperatures prevents the protein from lysing; the initial expenses for the cold press start-up are considerably lower;
  3. when processing the product no contact is required with such substances as acids, alkali, solvents and other chemicals. The finish sunflower-seed oil produced by cold press is valued highly because it practically does not lose the consumer utility, i.e. vitamins.

Vegetable oil production technology by cold pressing method

It is worth mentioning, that it is the most harmless and environment-friendly process. But at the same time it is less profitable as provides less sunflower-seed oil yield in comparison with other technologies (extraction).
Before processing the sunflower seeds shall be prepared in the proper manner. The seeds must be cleaned carefully; the rate of contaminants should not exceed 1 %, and that of improper seeds not to be higher than 3 %.
Just before conveying the seeds to the oil mill, they need to be dried and decorticated (the seed hulls to be separated from kernels). Then the seeds are to be ground. The produced substance is called the oil seed meal.
Then the oil seed meal is charged to the oil mill where a liquid part — oil, and a solid part — oilcake are separated by the worm press. The pressing occurs due to movements of the oil seed meal in the press chamber (cage).The product is heated because of friction. As this process requires no heating, the final product is abundant with such substances as antioxidants, vitamins, and lecithin.

After processing the oil is drained into the crude oil tank and leaved for several hours to settle, or fed directly to the filtration area, where mechanical impurities are removed from the oil. The refined oil is poured into special barrels, only after that it goes for packaging. At present the technology of cold press is regarded as the most optimal, useful, and practical.

The oilcake remained after the sunflower-seed oil production may be used for extraction, secondary pressing with or without heating, or as the feed for livestock.

A disadvantage of the process is that the oil produced by the cold press has a short shelf life. To avoid this, the product shall be subject to refining.

Completeness of the oil pressing depends on certain factors, as follows:

  1. pressure force of the worm inside the extracting cage;
  2. thickness of the oil seed meal layer;
  3. density and viscosity of the product;
  4. the time of the product presence in the pressing cage.

This method of production requires the best sunflower seeds, carefulness and exactness of the personnel resulting in high performance and finish product of top-quality.

Sunflower-seed oil, the first oil press, or so-called “crude” oil, because after processing this is just settled and filtered. The product is characterized by not only set of useful substances contained, but it has surprising taste, excellent and attractive appearance.

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Vegetable oil production from the Safflower-Seeds

Safflower is an oilyielding plant growing in the arid regions of Central Asia, where it is considered as a major alternative oilbearing crop to sunflower.

The safflower oil is notable for high caloric content and nutritive value. The vegetable oil from the safflower seeds is produced by PRODTECHMASH oilpressplant using the following technology:

  1. Safflower seeds preparation and handling area
  2. Milling area
  3. Pressing area

1. SEEDS PREPARATION AREA

The safflower seeds are transported to the Preparation Area after coarse separation. The seeds preparation unit includes a separator where the large and small contaminants are removed (by the use of cyclone and fan). Before coming to the separator the seeds pass through the charging hopper and magnetic trap.

2. MILLING AREA

Due to the fact that the safflower seeds have very hard peel, it needs to be hulled (shelled out) in order to produce oil. For this purpose the seeds, after Preparation Area, are transported to the Hulling Area. Then the dehulled (decorticated) seeds are fed to the separator where the kernel is separated from a large peel. The peel is removed to the waste by the pneumatic conveying system, and the milled kernel with a part of the peel is conveyed to the Pressing Area.

We believe that the remaining shell (considering its thickness) would be less abrasive than the whole seeds, while the abrasive wear of the equipment should be as high as that when processing the sunflower seeds.

3. PRESSING AREA

The prepared seeds are fed by the conveyor to the Press for Preliminary Expression where the oil seed meal is ground and heated, and then it moves to the М8МШП Oil Expeller .

With a view to increase the oil yield we propose the seedcake from the first М8МШП Oil Expeller to be conveyed via a takeup unit to the second М8МШП Oil Expeller for final pressing. The seedcake from the second press is removed by the conveyor, and there is the oil tank with a pump installed between the first and the second М8МШП Oil Expellers.

HOT OR COLD OIL PRESSING?

The method ofhotexpression of the safflower oil includes preliminary heating of the hulled safflower seeds prior to the pressing. This ensures the higher yield of oil and the lower wear rate of the equipment. However, using this technology results in the oil milling cost rise, because the oil cockers and heaters need to be procured. Also this method requires the higher power inputs.

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